Add $tls_in_* variables; note the old names as deprecated.

[users/heiko/exim.git] / src / src / tls-gnu.c

diff --git a/src/src/tls-gnu.c b/src/src/tls-gnu.c
index 8fcdd109dd7ecec7a4d99690e079b30d598e74a1..c582af79f0c43472c434e6881c1ae9e666005fbc 100644 (file)
--- a/src/src/tls-gnu.c
+++ b/src/src/tls-gnu.c
@@ -1,151 +1,196 @@
-/* $Cambridge: exim/src/src/tls-gnu.c,v 1.24 2009/11/16 19:50:37 nm4 Exp $ */
-

 /*************************************************
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
 /*************************************************
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 

-/* Copyright (c) University of Cambridge 1995 - 2009 */
+/* Copyright (c) University of Cambridge 1995 - 2012 */

 /* See the file NOTICE for conditions of use and distribution. */
 
 /* See the file NOTICE for conditions of use and distribution. */
 

-/* This module provides TLS (aka SSL) support for Exim using the GnuTLS
-library. It is #included into tls.c when that library is used. The code herein
-is based on a patch that was contributed by Nikos Mavroyanopoulos.
+/* Copyright (c) Phil Pennock 2012 */
+
+/* This file provides TLS/SSL support for Exim using the GnuTLS library,
+one of the available supported implementations.  This file is #included into
+tls.c when USE_GNUTLS has been set.
+
+The code herein is a revamp of GnuTLS integration using the current APIs; the
+original tls-gnu.c was based on a patch which was contributed by Nikos
+Mavroyanopoulos.  The revamp is partially a rewrite, partially cut&paste as
+appropriate.
+
+APIs current as of GnuTLS 2.12.18; note that the GnuTLS manual is for GnuTLS 3,
+which is not widely deployed by OS vendors.  Will note issues below, which may
+assist in updating the code in the future.  Another sources of hints is
+mod_gnutls for Apache (SNI callback registration and handling).

 
 

-No cryptographic code is included in Exim. All this module does is to call
-functions from the GnuTLS library. */
+Keeping client and server variables more split than before and is currently
+the norm, in anticipation of TLS in ACL callouts.

 
 

+I wanted to switch to gnutls_certificate_set_verify_function() so that
+certificate rejection could happen during handshake where it belongs, rather
+than being dropped afterwards, but that was introduced in 2.10.0 and Debian
+(6.0.5) is still on 2.8.6.  So for now we have to stick with sub-par behaviour.

 
 

-/* Heading stuff for GnuTLS */
+(I wasn't looking for libraries quite that old, when updating to get rid of
+compiler warnings of deprecated APIs.  If it turns out that a lot of the rest
+require current GnuTLS, then we'll drop support for the ancient libraries).
+*/

 
 #include <gnutls/gnutls.h>
 
 #include <gnutls/gnutls.h>

+/* needed for cert checks in verification and DN extraction: */

 #include <gnutls/x509.h>
 #include <gnutls/x509.h>

+/* man-page is incorrect, gnutls_rnd() is not in gnutls.h: */
+#include <gnutls/crypto.h>
+
+/* GnuTLS 2 vs 3

 
 

+GnuTLS 3 only:
+  gnutls_global_set_audit_log_function()

 
 

-#define UNKNOWN_NAME "unknown"
-#define DH_BITS      1024
-#define PARAM_SIZE 2*1024
+Changes:
+  gnutls_certificate_verify_peers2(): is new, drop the 2 for old version
+*/

 
 

+/* Local static variables for GnuTLS */

 
 

-/* Values for verify_requirment */
+/* Values for verify_requirement */

 
 

-enum { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED };
+enum peer_verify_requirement { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED };

 
 

-/* Local static variables for GNUTLS */
+/* This holds most state for server or client; with this, we can set up an
+outbound TLS-enabled connection in an ACL callout, while not stomping all
+over the TLS variables available for expansion.

 
 

-static host_item *client_host;
+Some of these correspond to variables in globals.c; those variables will
+be set to point to content in one of these instances, as appropriate for
+the stage of the process lifetime.

 
 

-static gnutls_dh_params dh_params = NULL;
+Not handled here: global tls_channelbinding_b64.
+*/

 
 

-static gnutls_certificate_server_credentials x509_cred = NULL;
-static gnutls_session tls_session = NULL;
+typedef struct exim_gnutls_state {
+  gnutls_session_t session;
+  gnutls_certificate_credentials_t x509_cred;
+  gnutls_priority_t priority_cache;
+  enum peer_verify_requirement verify_requirement;
+  int fd_in;
+  int fd_out;
+  BOOL peer_cert_verified;
+  BOOL trigger_sni_changes;
+  BOOL have_set_peerdn;
+  const struct host_item *host;
+  uschar *peerdn;
+  uschar *ciphersuite;
+  uschar *received_sni;
+
+  const uschar *tls_certificate;
+  const uschar *tls_privatekey;
+  const uschar *tls_sni; /* client send only, not received */
+  const uschar *tls_verify_certificates;
+  const uschar *tls_crl;
+  const uschar *tls_require_ciphers;
+  uschar *exp_tls_certificate;
+  uschar *exp_tls_privatekey;
+  uschar *exp_tls_sni;
+  uschar *exp_tls_verify_certificates;
+  uschar *exp_tls_crl;
+  uschar *exp_tls_require_ciphers;
+
+  tls_support *tlsp;   /* set in tls_init() */
+
+  uschar *xfer_buffer;
+  int xfer_buffer_lwm;
+  int xfer_buffer_hwm;
+  int xfer_eof;
+  int xfer_error;
+} exim_gnutls_state_st;
+
+static const exim_gnutls_state_st exim_gnutls_state_init = {
+  NULL, NULL, NULL, VERIFY_NONE, -1, -1, FALSE, FALSE, FALSE,
+  NULL, NULL, NULL, NULL,
+  NULL, NULL, NULL, NULL, NULL, NULL,
+  NULL, NULL, NULL, NULL, NULL, NULL,
+  NULL,
+  NULL, 0, 0, 0, 0,
+};

 
 

-static char ssl_errstring[256];
+/* Not only do we have our own APIs which don't pass around state, assuming
+it's held in globals, GnuTLS doesn't appear to let us register callback data
+for callbacks, or as part of the session, so we have to keep a "this is the
+context we're currently dealing with" pointer and rely upon being
+single-threaded to keep from processing data on an inbound TLS connection while
+talking to another TLS connection for an outbound check.  This does mean that
+there's no way for heart-beats to be responded to, for the duration of the
+second connection. */

 
 

-static int  ssl_session_timeout = 200;
-static int  verify_requirement;
+static exim_gnutls_state_st state_server, state_client;

 
 

-/* Priorities for TLS algorithms to use. In each case there's a default table,
-and space into which it can be copied and altered. */
+/* dh_params are initialised once within the lifetime of a process using TLS;
+if we used TLS in a long-lived daemon, we'd have to reconsider this.  But we
+don't want to repeat this. */

 
 

-static const int default_proto_priority[16] = {
-  GNUTLS_TLS1,
-  GNUTLS_SSL3,
-  0 };
+static gnutls_dh_params_t dh_server_params = NULL;

 
 

-static int proto_priority[16];
+/* No idea how this value was chosen; preserving it.  Default is 3600. */

 
 

-static const int default_kx_priority[16] = {
-  GNUTLS_KX_RSA,
-  GNUTLS_KX_DHE_DSS,
-  GNUTLS_KX_DHE_RSA,
-  0 };
+static const int ssl_session_timeout = 200;

 
 

-static int kx_priority[16];
+static const char * const exim_default_gnutls_priority = "NORMAL";

 
 

-static int default_cipher_priority[16] = {
-  GNUTLS_CIPHER_AES_256_CBC,
-  GNUTLS_CIPHER_AES_128_CBC,
-  GNUTLS_CIPHER_3DES_CBC,
-  GNUTLS_CIPHER_ARCFOUR_128,
-  0 };
+/* Guard library core initialisation */

 
 

-static int cipher_priority[16];
+static BOOL exim_gnutls_base_init_done = FALSE;

 
 

-static const int default_mac_priority[16] = {
-  GNUTLS_MAC_SHA,
-  GNUTLS_MAC_MD5,
-  0 };

 
 

-static int mac_priority[16];
+/* ------------------------------------------------------------------------ */
+/* macros */

 
 

-/* These two are currently not changeable. */
+#define MAX_HOST_LEN 255

 
 

-static const int comp_priority[16] = { GNUTLS_COMP_NULL, 0 };
-static const int cert_type_priority[16] = { GNUTLS_CRT_X509, 0 };
+/* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup
+the library logging; a value less than 0 disables the calls to set up logging
+callbacks. */
+#ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL
+#define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1
+#endif

 
 

-/* Tables of priority names and equivalent numbers */
+#ifndef EXIM_CLIENT_DH_MIN_BITS
+#define EXIM_CLIENT_DH_MIN_BITS 1024
+#endif

 
 

-typedef struct pri_item {
-  uschar *name;
-  int *values;
-} pri_item;
+/* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we
+can ask for a bit-strength.  Without that, we stick to the constant we had
+before, for now. */
+#ifndef EXIM_SERVER_DH_BITS_PRE2_12
+#define EXIM_SERVER_DH_BITS_PRE2_12 1024
+#endif

 
 

+#define exim_gnutls_err_check(Label) do { \
+  if (rc != GNUTLS_E_SUCCESS) { return tls_error((Label), gnutls_strerror(rc), host); } } while (0)

 
 

-static int tls1_codes[] = { GNUTLS_TLS1, 0 };
-static int ssl3_codes[] = { GNUTLS_SSL3, 0 };
+#define expand_check_tlsvar(Varname) expand_check(state->Varname, US #Varname, &state->exp_##Varname)

 
 

-static pri_item proto_index[] = {
-  { US"TLS1", tls1_codes },
-  { US"SSL3", ssl3_codes }
-};
+#if GNUTLS_VERSION_NUMBER >= 0x020c00
+#define HAVE_GNUTLS_SESSION_CHANNEL_BINDING
+#define HAVE_GNUTLS_SEC_PARAM_CONSTANTS
+#define HAVE_GNUTLS_RND
+#endif

 
 
 
 

-static int kx_rsa_codes[]      = { GNUTLS_KX_RSA,
-                                   GNUTLS_KX_DHE_RSA, 0 };
-static int kx_dhe_codes[]      = { GNUTLS_KX_DHE_DSS,
-                                   GNUTLS_KX_DHE_RSA, 0 };
-static int kx_dhe_dss_codes[]  = { GNUTLS_KX_DHE_DSS, 0 };
-static int kx_dhe_rsa_codes[]  = { GNUTLS_KX_DHE_RSA, 0 };

 
 

-static pri_item kx_index[] = {
-  { US"DHE_DSS", kx_dhe_dss_codes },
-  { US"DHE_RSA", kx_dhe_rsa_codes },
-  { US"RSA", kx_rsa_codes },
-  { US"DHE", kx_dhe_codes }
-};

 
 

+/* ------------------------------------------------------------------------ */
+/* Callback declarations */

 
 

-static int arcfour_128_codes[] = { GNUTLS_CIPHER_ARCFOUR_128, 0 };
-static int arcfour_40_codes[]  = { GNUTLS_CIPHER_ARCFOUR_40, 0 };
-static int arcfour_codes[]     = { GNUTLS_CIPHER_ARCFOUR_128,
-                                   GNUTLS_CIPHER_ARCFOUR_40, 0 };
-static int aes_256_codes[]     = { GNUTLS_CIPHER_AES_256_CBC, 0 };
-static int aes_128_codes[]     = { GNUTLS_CIPHER_AES_128_CBC, 0 };
-static int aes_codes[]         = { GNUTLS_CIPHER_AES_256_CBC,
-                                   GNUTLS_CIPHER_AES_128_CBC, 0 };
-static int des3_codes[]        = { GNUTLS_CIPHER_3DES_CBC, 0 };
-
-static pri_item cipher_index[] = {
-  { US"ARCFOUR_128", arcfour_128_codes },
-  { US"ARCFOUR_40", arcfour_40_codes },
-  { US"ARCFOUR", arcfour_codes },
-  { US"AES_256", aes_256_codes },
-  { US"AES_128", aes_128_codes },
-  { US"AES", aes_codes },
-  { US"3DES", des3_codes }
-};
+#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
+static void exim_gnutls_logger_cb(int level, const char *message);
+#endif

 
 

+static int exim_sni_handling_cb(gnutls_session_t session);

 
 

-static int mac_sha_codes[]     = { GNUTLS_MAC_SHA, 0 };
-static int mac_md5_codes[]     = { GNUTLS_MAC_MD5, 0 };

 
 

-static pri_item mac_index[] = {
-  { US"SHA",  mac_sha_codes },
-  { US"SHA1", mac_sha_codes },
-  { US"MD5",  mac_md5_codes }
-};

 
 
 
 

+/* ------------------------------------------------------------------------ */
+/* Static functions */

 
 /*************************************************
 *               Handle TLS error                 *
 
 /*************************************************
 *               Handle TLS error                 *


@@ -160,120 +205,141 @@ some shared functions.
 
 Argument:
   prefix    text to include in the logged error
 
 Argument:
   prefix    text to include in the logged error

-  host      NULL if setting up a server;
-            the connected host if setting up a client

   msg       additional error string (may be NULL)
             usually obtained from gnutls_strerror()
   msg       additional error string (may be NULL)
             usually obtained from gnutls_strerror()

+  host      NULL if setting up a server;
+            the connected host if setting up a client

 
 Returns:    OK/DEFER/FAIL
 */
 
 static int
 
 Returns:    OK/DEFER/FAIL
 */
 
 static int

-tls_error(uschar *prefix, host_item *host, const char *msg)
+tls_error(const uschar *prefix, const char *msg, const host_item *host)

 {
 {

-if (host == NULL)
+if (host)
+  {
+  log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s)%s%s",
+      host->name, host->address, prefix, msg ? ": " : "", msg ? msg : "");
+  return FAIL;
+  }
+else

   {
   uschar *conn_info = smtp_get_connection_info();
   {
   uschar *conn_info = smtp_get_connection_info();

-  if (strncmp(conn_info, "SMTP ", 5) == 0)
+  if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)

     conn_info += 5;
   log_write(0, LOG_MAIN, "TLS error on %s (%s)%s%s",
     conn_info += 5;
   log_write(0, LOG_MAIN, "TLS error on %s (%s)%s%s",

-    conn_info, prefix, msg ? ": " : "", msg ? msg : "");
+      conn_info, prefix, msg ? ": " : "", msg ? msg : "");

   return DEFER;
   }
   return DEFER;
   }

-else
-  {
-  log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s)%s%s",
-    host->name, host->address, prefix, msg ? ": " : "", msg ? msg : "");
-  return FAIL;
-  }

 }
 
 
 
 }
 
 
 

+

 /*************************************************
 /*************************************************

-*             Verify certificate                 *
+*    Deal with logging errors during I/O         *

 *************************************************/
 
 *************************************************/
 

-/* Called after a successful handshake, when certificate verification is
-required or optional, for both server and client.
+/* We have to get the identity of the peer from saved data.

 
 

-Arguments:
-  session    GNUTLS session
-  error      where to put text giving a reason for failure
+Argument:
+  state    the current GnuTLS exim state container
+  rc       the GnuTLS error code, or 0 if it's a local error
+  when     text identifying read or write
+  text     local error text when ec is 0

 
 

-Returns:     TRUE/FALSE
+Returns:   nothing

 */
 
 */
 

-static BOOL
-verify_certificate(gnutls_session session, const char **error)
+static void
+record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text)

 {
 {

-int verify;
-uschar *dn_string = US"";
-const gnutls_datum *cert;
-unsigned int cert_size = 0;
+const char *msg;

 
 

-*error = NULL;
+if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED)
+  msg = CS string_sprintf("%s: %s", US gnutls_strerror(rc),
+    US gnutls_alert_get_name(gnutls_alert_get(state->session)));
+else
+  msg = gnutls_strerror(rc);

 
 

-/* Get the peer's certificate. If it sent one, extract it's DN, and then
-attempt to verify the certificate. If no certificate is supplied, verification
-is forced to fail. */
+tls_error(when, msg, state->host);
+}

 
 

-cert = gnutls_certificate_get_peers(session, &cert_size);
-if (cert != NULL)
-  {
-  uschar buff[1024];
-  gnutls_x509_crt gcert;

 
 

-  gnutls_x509_crt_init(&gcert);
-  dn_string = US"unknown";

 
 

-  if (gnutls_x509_crt_import(gcert, cert, GNUTLS_X509_FMT_DER) == 0)
-    {
-    size_t bufsize = sizeof(buff);
-    if (gnutls_x509_crt_get_dn(gcert, CS buff, &bufsize) >= 0)
-      dn_string = string_copy_malloc(buff);
-    }

 
 

-  verify = gnutls_certificate_verify_peers(session);
-  }
-else
-  {
-  DEBUG(D_tls) debug_printf("no peer certificate supplied\n");
-  verify = GNUTLS_CERT_INVALID;
-  *error = "not supplied";
-  }
+/*************************************************
+*        Set various Exim expansion vars         *
+*************************************************/

 
 

-/* Handle the result of verification. INVALID seems to be set as well
-as REVOKED, but leave the test for both. */
+/* We set various Exim global variables from the state, once a session has
+been established.  With TLS callouts, may need to change this to stack
+variables, or just re-call it with the server state after client callout
+has finished.

 
 

-if ((verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED)) != 0)
-  {
-  tls_certificate_verified = FALSE;
-  if (*error == NULL) *error = ((verify & GNUTLS_CERT_REVOKED) != 0)?
-    "revoked" : "invalid";
-  if (verify_requirement == VERIFY_REQUIRED)
-    {
-    DEBUG(D_tls) debug_printf("TLS certificate verification failed (%s): "
-      "peerdn=%s\n", *error, dn_string);
-    gnutls_alert_send(session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
-    return FALSE;                       /* reject */
-    }
-  DEBUG(D_tls) debug_printf("TLS certificate verify failure (%s) overridden "
-      "(host in tls_try_verify_hosts): peerdn=%s\n", *error, dn_string);
-  }
-else
-  {
-  tls_certificate_verified = TRUE;
-  DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=%s\n",
-    dn_string);
-  }
+Make sure anything set here is inset in tls_getc().
+
+Sets:
+  tls_active                fd
+  tls_bits                  strength indicator
+  tls_certificate_verified  bool indicator
+  tls_channelbinding_b64    for some SASL mechanisms
+  tls_cipher                a string
+  tls_peerdn                a string
+  tls_sni                   a (UTF-8) string
+
+Argument:
+  state      the relevant exim_gnutls_state_st *
+*/
+
+static void
+extract_exim_vars_from_tls_state(exim_gnutls_state_st *state, BOOL is_server)
+{
+gnutls_cipher_algorithm_t cipher;
+#ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
+int old_pool;
+int rc;
+gnutls_datum_t channel;
+#endif
+
+state->tlsp->active = state->fd_out;
+
+cipher = gnutls_cipher_get(state->session);
+/* returns size in "bytes" */
+state->tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8;
+
+state->tlsp->cipher = state->ciphersuite;
+
+DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite);

 
 

-tls_peerdn = dn_string;
-return TRUE;                            /* accept */
+state->tlsp->certificate_verified = state->peer_cert_verified;
+
+/* note that tls_channelbinding_b64 is not saved to the spool file, since it's
+only available for use for authenticators while this TLS session is running. */
+
+tls_channelbinding_b64 = NULL;
+#ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
+channel.data = NULL;
+channel.size = 0;
+rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel);
+if (rc) {
+  DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc));
+} else {
+  old_pool = store_pool;
+  store_pool = POOL_PERM;
+  tls_channelbinding_b64 = auth_b64encode(channel.data, (int)channel.size);
+  store_pool = old_pool;
+  DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n");
+}
+#endif
+
+state->tlsp->peerdn = state->peerdn;
+state->tlsp->sni =    state->received_sni;

 }
 
 
 
 }
 
 
 

+

 /*************************************************
 *            Setup up DH parameters              *
 *************************************************/
 /*************************************************
 *            Setup up DH parameters              *
 *************************************************/


@@ -288,30 +354,100 @@ file is never present. If two processes both compute some new parameters, you
 waste a bit of effort, but it doesn't seem worth messing around with locking to
 prevent this.
 
 waste a bit of effort, but it doesn't seem worth messing around with locking to
 prevent this.
 

-Argument:
-  host       NULL for server, server for client (for error handling)
-

 Returns:     OK/DEFER/FAIL
 */
 
 static int
 Returns:     OK/DEFER/FAIL
 */
 
 static int

-init_dh(host_item *host)
+init_server_dh(void)

 {
 {

-int fd;
-int ret;
+int fd, rc;
+unsigned int dh_bits;

 gnutls_datum m;
 gnutls_datum m;

-uschar filename[200];
+uschar filename_buf[PATH_MAX];
+uschar *filename = NULL;
+size_t sz;
+uschar *exp_tls_dhparam;
+BOOL use_file_in_spool = FALSE;
+BOOL use_fixed_file = FALSE;
+host_item *host = NULL; /* dummy for macros */

 
 

-/* Initialize the data structures for holding the parameters */
+DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n");

 
 

-ret = gnutls_dh_params_init(&dh_params);
-if (ret < 0) return tls_error(US"init dh_params", host, gnutls_strerror(ret));
+rc = gnutls_dh_params_init(&dh_server_params);
+exim_gnutls_err_check(US"gnutls_dh_params_init");

 
 

-/* Set up the name of the cache file */
+m.data = NULL;
+m.size = 0;

 
 

-if (!string_format(filename, sizeof(filename), "%s/gnutls-params",
-      spool_directory))
-  return tls_error(US"overlong filename", host, NULL);
+if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam))
+  return DEFER;
+
+if (!exp_tls_dhparam)
+  {
+  DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n");
+  m.data = US std_dh_prime_default();
+  m.size = Ustrlen(m.data);
+  }
+else if (Ustrcmp(exp_tls_dhparam, "historic") == 0)
+  use_file_in_spool = TRUE;
+else if (Ustrcmp(exp_tls_dhparam, "none") == 0)
+  {
+  DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
+  return OK;
+  }
+else if (exp_tls_dhparam[0] != '/')
+  {
+  m.data = US std_dh_prime_named(exp_tls_dhparam);
+  if (m.data == NULL)
+    return tls_error(US"No standard prime named", CS exp_tls_dhparam, NULL);
+  m.size = Ustrlen(m.data);
+  }
+else
+  {
+  use_fixed_file = TRUE;
+  filename = exp_tls_dhparam;
+  }
+
+if (m.data)
+  {
+  rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
+  exim_gnutls_err_check(US"gnutls_dh_params_import_pkcs3");
+  DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n");
+  return OK;
+  }
+
+#ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS
+/* If you change this constant, also change dh_param_fn_ext so that we can use a
+different filename and ensure we have sufficient bits. */
+dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL);
+if (!dh_bits)
+  return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL);
+DEBUG(D_tls)
+  debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n",
+      dh_bits);
+#else
+dh_bits = EXIM_SERVER_DH_BITS_PRE2_12;
+DEBUG(D_tls)
+  debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n",
+      dh_bits);
+#endif
+
+/* Some clients have hard-coded limits. */
+if (dh_bits > tls_dh_max_bits)
+  {
+  DEBUG(D_tls)
+    debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n",
+        tls_dh_max_bits);
+  dh_bits = tls_dh_max_bits;
+  }
+
+if (use_file_in_spool)
+  {
+  if (!string_format(filename_buf, sizeof(filename_buf),
+        "%s/gnutls-params-%d", spool_directory, dh_bits))
+    return tls_error(US"overlong filename", NULL, NULL);
+  filename = filename_buf;
+  }

 
 /* Open the cache file for reading and if successful, read it and set up the
 parameters. */
 
 /* Open the cache file for reading and if successful, read it and set up the
 parameters. */


@@ -320,27 +456,50 @@ fd = Uopen(filename, O_RDONLY, 0);
 if (fd >= 0)
   {
   struct stat statbuf;
 if (fd >= 0)
   {
   struct stat statbuf;

-  if (fstat(fd, &statbuf) < 0)
+  FILE *fp;
+  int saved_errno;
+
+  if (fstat(fd, &statbuf) < 0)  /* EIO */

     {
     {

+    saved_errno = errno;

     (void)close(fd);
     (void)close(fd);

-    return tls_error(US"TLS cache stat failed", host, strerror(errno));
+    return tls_error(US"TLS cache stat failed", strerror(saved_errno), NULL);
+    }
+  if (!S_ISREG(statbuf.st_mode))
+    {
+    (void)close(fd);
+    return tls_error(US"TLS cache not a file", NULL, NULL);
+    }
+  fp = fdopen(fd, "rb");
+  if (!fp)
+    {
+    saved_errno = errno;
+    (void)close(fd);
+    return tls_error(US"fdopen(TLS cache stat fd) failed",
+        strerror(saved_errno), NULL);

     }
 
   m.size = statbuf.st_size;
   m.data = malloc(m.size);
   if (m.data == NULL)
     }
 
   m.size = statbuf.st_size;
   m.data = malloc(m.size);
   if (m.data == NULL)

-    return tls_error(US"memory allocation failed", host, strerror(errno));
-  errno = 0;
-  if (read(fd, m.data, m.size) != m.size)
-    return tls_error(US"TLS cache read failed", host, strerror(errno));
-  (void)close(fd);
-
-  ret = gnutls_dh_params_import_pkcs3(dh_params, &m, GNUTLS_X509_FMT_PEM);
-  if (ret < 0)
-    return tls_error(US"DH params import", host, gnutls_strerror(ret));
-  DEBUG(D_tls) debug_printf("read D-H parameters from file\n");
+    {
+    fclose(fp);
+    return tls_error(US"malloc failed", strerror(errno), NULL);
+    }
+  sz = fread(m.data, m.size, 1, fp);
+  if (!sz)
+    {
+    saved_errno = errno;
+    fclose(fp);
+    free(m.data);
+    return tls_error(US"fread failed", strerror(saved_errno), NULL);
+    }
+  fclose(fp);

 
 

+  rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);

   free(m.data);
   free(m.data);

+  exim_gnutls_err_check(US"gnutls_dh_params_import_pkcs3");
+  DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename);

   }
 
 /* If the file does not exist, fall through to compute new data and cache it.
   }
 
 /* If the file does not exist, fall through to compute new data and cache it.


@@ -348,13 +507,13 @@ If there was any other opening error, it is serious. */
 
 else if (errno == ENOENT)
   {
 
 else if (errno == ENOENT)
   {

-  ret = -1;
+  rc = -1;

   DEBUG(D_tls)
   DEBUG(D_tls)

-    debug_printf("parameter cache file %s does not exist\n", filename);
+    debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename);

   }
 else
   }
 else

-  return tls_error(string_open_failed(errno, "%s for reading", filename),
-    host, NULL);
+  return tls_error(string_open_failed(errno, "\"%s\" for reading", filename),
+      NULL, NULL);

 
 /* If ret < 0, either the cache file does not exist, or the data it contains
 is not useful. One particular case of this is when upgrading from an older
 
 /* If ret < 0, either the cache file does not exist, or the data it contains
 is not useful. One particular case of this is when upgrading from an older


@@ -362,59 +521,93 @@ release of Exim in which the data was stored in a different format. We don't
 try to be clever and support both formats; we just regenerate new data in this
 case. */
 
 try to be clever and support both formats; we just regenerate new data in this
 case. */
 

-if (ret < 0)
+if (rc < 0)

   {
   {

-  uschar tempfilename[sizeof(filename) + 10];
-
-  DEBUG(D_tls) debug_printf("generating %d bit Diffie-Hellman key...\n",
-    DH_BITS);
-  ret = gnutls_dh_params_generate2(dh_params, DH_BITS);
-  if (ret < 0) return tls_error(US"D-H key generation", host, gnutls_strerror(ret));
+  uschar *temp_fn;
+  unsigned int dh_bits_gen = dh_bits;

 
 

-  /* Write the parameters to a file in the spool directory so that we
-  can use them from other Exim processes. */
+  if ((PATH_MAX - Ustrlen(filename)) < 10)
+    return tls_error(US"Filename too long to generate replacement",
+        CS filename, NULL);

 
 

-  sprintf(CS tempfilename, "%s-%d", filename, (int)getpid());
-  fd = Uopen(tempfilename, O_WRONLY|O_CREAT, 0400);
+  temp_fn = string_copy(US "%s.XXXXXXX");
+  fd = mkstemp(CS temp_fn); /* modifies temp_fn */

   if (fd < 0)
   if (fd < 0)

-    return tls_error(string_open_failed(errno, "%s for writing", filename),
-      host, NULL);
+    return tls_error(US"Unable to open temp file", strerror(errno), NULL);

   (void)fchown(fd, exim_uid, exim_gid);   /* Probably not necessary */
 
   (void)fchown(fd, exim_uid, exim_gid);   /* Probably not necessary */
 

-  /* export the parameters in a format that can be generated using GNUTLS'
-   * certtool or other programs.
-   *
-   * The commands for certtool are:
-   * $ certtool --generate-dh-params --bits 1024 > params
+  /* GnuTLS overshoots!
+   * If we ask for 2236, we might get 2237 or more.
+   * But there's no way to ask GnuTLS how many bits there really are.
+   * We can ask how many bits were used in a TLS session, but that's it!
+   * The prime itself is hidden behind too much abstraction.
+   * So we ask for less, and proceed on a wing and a prayer.
+   * First attempt, subtracted 3 for 2233 and got 2240.

    */
    */

+  if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10)
+    {
+    dh_bits_gen = dh_bits - 10;
+    DEBUG(D_tls)
+      debug_printf("being paranoid about DH generation, make it '%d' bits'\n",
+          dh_bits_gen);
+    }

 
 

-  m.size = PARAM_SIZE;
+  DEBUG(D_tls)
+    debug_printf("requesting generation of %d bit Diffie-Hellman prime ...\n",
+        dh_bits_gen);
+  rc = gnutls_dh_params_generate2(dh_server_params, dh_bits_gen);
+  exim_gnutls_err_check(US"gnutls_dh_params_generate2");
+
+  /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time,
+  and I confirmed that a NULL call to get the size first is how the GnuTLS
+  sample apps handle this. */
+
+  sz = 0;
+  m.data = NULL;
+  rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
+      m.data, &sz);
+  if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
+    exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3(NULL) sizing");
+  m.size = sz;

   m.data = malloc(m.size);
   if (m.data == NULL)
   m.data = malloc(m.size);
   if (m.data == NULL)

-    return tls_error(US"memory allocation failed", host, strerror(errno));
-
-  m.size = PARAM_SIZE;
-  ret = gnutls_dh_params_export_pkcs3(dh_params, GNUTLS_X509_FMT_PEM, m.data,
-    &m.size);
-  if (ret < 0)
-    return tls_error(US"DH params export", host, gnutls_strerror(ret));
-
-  m.size = Ustrlen(m.data);
-  errno = 0;
-  if (write(fd, m.data, m.size) != m.size || write(fd, "\n", 1) != 1)
-    return tls_error(US"TLS cache write failed", host, strerror(errno));
+    return tls_error(US"memory allocation failed", strerror(errno), NULL);
+  /* this will return a size 1 less than the allocation size above */
+  rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
+      m.data, &sz);
+  if (rc != GNUTLS_E_SUCCESS)
+    {
+    free(m.data);
+    exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3() real");
+    }
+  m.size = sz; /* shrink by 1, probably */

 
 

+  sz = write_to_fd_buf(fd, m.data, (size_t) m.size);
+  if (sz != m.size)
+    {
+    free(m.data);
+    return tls_error(US"TLS cache write D-H params failed",
+        strerror(errno), NULL);
+    }

   free(m.data);
   free(m.data);

-  (void)close(fd);
+  sz = write_to_fd_buf(fd, US"\n", 1);
+  if (sz != 1)
+    return tls_error(US"TLS cache write D-H params final newline failed",
+        strerror(errno), NULL);

 
 

-  if (rename(CS tempfilename, CS filename) < 0)
-    return tls_error(string_sprintf("failed to rename %s as %s",
-      tempfilename, filename), host, strerror(errno));
+  rc = close(fd);
+  if (rc)
+    return tls_error(US"TLS cache write close() failed",
+        strerror(errno), NULL);

 
 

-  DEBUG(D_tls) debug_printf("wrote D-H parameters to file %s\n", filename);
+  if (Urename(temp_fn, filename) < 0)
+    return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"",
+          temp_fn, filename), strerror(errno), NULL);
+
+  DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);

   }
 
   }
 

-DEBUG(D_tls) debug_printf("initialized D-H parameters\n");
+DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");

 return OK;
 }
 
 return OK;
 }
 


@@ -422,91 +615,122 @@ return OK;
 
 
 /*************************************************
 
 
 /*************************************************

-*            Initialize for GnuTLS               *
+*       Variables re-expanded post-SNI           *

 *************************************************/
 
 *************************************************/
 

-/* Called from both server and client code. In the case of a server, errors
-before actual TLS negotiation return DEFER.
+/* Called from both server and client code, via tls_init(), and also from
+the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni".
+
+We can tell the two apart by state->received_sni being non-NULL in callback.
+
+The callback should not call us unless state->trigger_sni_changes is true,
+which we are responsible for setting on the first pass through.

 
 Arguments:
 
 Arguments:

-  host            connected host, if client; NULL if server
-  certificate     certificate file
-  privatekey      private key file
-  cas             CA certs file
-  crl             CRL file
+  state           exim_gnutls_state_st *

 
 Returns:          OK/DEFER/FAIL
 */
 
 static int
 
 Returns:          OK/DEFER/FAIL
 */
 
 static int

-tls_init(host_item *host, uschar *certificate, uschar *privatekey, uschar *cas,
-  uschar *crl)
+tls_expand_session_files(exim_gnutls_state_st *state)

 {
 {

+struct stat statbuf;

 int rc;
 int rc;

-uschar *cert_expanded, *key_expanded, *cas_expanded, *crl_expanded;
-
-client_host = host;
+const host_item *host = state->host;  /* macro should be reconsidered? */
+uschar *saved_tls_certificate = NULL;
+uschar *saved_tls_privatekey = NULL;
+uschar *saved_tls_verify_certificates = NULL;
+uschar *saved_tls_crl = NULL;
+int cert_count;
+
+/* We check for tls_sni *before* expansion. */
+if (!state->host)
+  {
+  if (!state->received_sni)
+    {
+    if (state->tls_certificate &&
+        (Ustrstr(state->tls_certificate, US"tls_sni") ||
+         Ustrstr(state->tls_certificate, US"tls_in_sni") ||
+         Ustrstr(state->tls_certificate, US"tls_out_sni")
+       ))
+      {
+      DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n");
+      state->trigger_sni_changes = TRUE;
+      }
+    }
+  else
+    {
+    /* useful for debugging */
+    saved_tls_certificate = state->exp_tls_certificate;
+    saved_tls_privatekey = state->exp_tls_privatekey;
+    saved_tls_verify_certificates = state->exp_tls_verify_certificates;
+    saved_tls_crl = state->exp_tls_crl;
+    }
+  }

 
 

-rc = gnutls_global_init();
-if (rc < 0) return tls_error(US"tls-init", host, gnutls_strerror(rc));
+rc = gnutls_certificate_allocate_credentials(&state->x509_cred);
+exim_gnutls_err_check(US"gnutls_certificate_allocate_credentials");

 
 

-/* Create D-H parameters, or read them from the cache file. This function does
-its own SMTP error messaging. */
+/* remember: expand_check_tlsvar() is expand_check() but fiddling with
+state members, assuming consistent naming; and expand_check() returns
+false if expansion failed, unless expansion was forced to fail. */

 
 

-rc = init_dh(host);
-if (rc != OK) return rc;
+/* check if we at least have a certificate, before doing expensive
+D-H generation. */

 
 

-/* Create the credentials structure */
+if (!expand_check_tlsvar(tls_certificate))
+  return DEFER;

 
 

-rc = gnutls_certificate_allocate_credentials(&x509_cred);
-if (rc < 0)
-  return tls_error(US"certificate_allocate_credentials",
-    host, gnutls_strerror(rc));
+/* certificate is mandatory in server, optional in client */

 
 

-/* This stuff must be done for each session, because different certificates
-may be required for different sessions. */
+if ((state->exp_tls_certificate == NULL) ||
+    (*state->exp_tls_certificate == '\0'))
+  {
+  if (state->host == NULL)
+    return tls_error(US"no TLS server certificate is specified", NULL, NULL);
+  else
+    DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n");
+  }

 
 

-if (!expand_check(certificate, US"tls_certificate", &cert_expanded))
+if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey))

   return DEFER;
 
   return DEFER;
 

-key_expanded = NULL;
-if (privatekey != NULL)
+/* tls_privatekey is optional, defaulting to same file as certificate */
+
+if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0')

   {
   {

-  if (!expand_check(privatekey, US"tls_privatekey", &key_expanded))
-    return DEFER;
+  state->tls_privatekey = state->tls_certificate;
+  state->exp_tls_privatekey = state->exp_tls_certificate;

   }
 
   }
 

-/* If expansion was forced to fail, key_expanded will be NULL. If the result of
-the expansion is an empty string, ignore it also, and assume that the private
-key is in the same file as the certificate. */

 
 

-if (key_expanded == NULL || *key_expanded == 0)
-  key_expanded = cert_expanded;
-
-/* Set the certificate and private keys */
-
-if (cert_expanded != NULL)
+if (state->exp_tls_certificate && *state->exp_tls_certificate)

   {
   DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
   {
   DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",

-    cert_expanded, key_expanded);
-  rc = gnutls_certificate_set_x509_key_file(x509_cred, CS cert_expanded,
-    CS key_expanded, GNUTLS_X509_FMT_PEM);
-  if (rc < 0)
+      state->exp_tls_certificate, state->exp_tls_privatekey);
+
+  if (state->received_sni)

     {
     {

-    uschar *msg = string_sprintf("cert/key setup: cert=%s key=%s",
-      cert_expanded, key_expanded);
-    return tls_error(msg, host, gnutls_strerror(rc));
+    if ((Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0) &&
+        (Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0))
+      {
+      DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n");
+      }
+    else
+      {
+      DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n");
+      }

     }
     }

-  }

 
 

-/* A certificate is mandatory in a server, but not in a client */
-
-else
-  {
-  if (host == NULL)
-    return tls_error(US"no TLS server certificate is specified", NULL, NULL);
-  DEBUG(D_tls) debug_printf("no TLS client certificate is specified\n");
-  }
+  rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
+      CS state->exp_tls_certificate, CS state->exp_tls_privatekey,
+      GNUTLS_X509_FMT_PEM);
+  exim_gnutls_err_check(
+      string_sprintf("cert/key setup: cert=%s key=%s",
+        state->exp_tls_certificate, state->exp_tls_privatekey));
+  DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
+  } /* tls_certificate */

 
 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
 provided. Experiment shows that, if the certificate file is empty, an unhelpful
 
 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
 provided. Experiment shows that, if the certificate file is empty, an unhelpful


@@ -514,48 +738,87 @@ error message is provided. However, if we just refrain from setting anything up
 in that case, certificate verification fails, which seems to be the correct
 behaviour. */
 
 in that case, certificate verification fails, which seems to be the correct
 behaviour. */
 

-if (cas != NULL)
+if (state->tls_verify_certificates && *state->tls_verify_certificates)

   {
   {

-  struct stat statbuf;
-
-  if (!expand_check(cas, US"tls_verify_certificates", &cas_expanded))
+  if (!expand_check_tlsvar(tls_verify_certificates))

     return DEFER;
     return DEFER;

+  if (state->tls_crl && *state->tls_crl)
+    if (!expand_check_tlsvar(tls_crl))
+      return DEFER;

 
 

-  if (stat(CS cas_expanded, &statbuf) < 0)
+  if (!(state->exp_tls_verify_certificates &&
+        *state->exp_tls_verify_certificates))

     {
     {

-    log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s "
-      "(tls_verify_certificates): %s", cas_expanded, strerror(errno));
-    return DEFER;
+    DEBUG(D_tls)
+      debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n");
+    /* With no tls_verify_certificates, we ignore tls_crl too */
+    return OK;

     }
     }

+  }
+else
+  {
+  DEBUG(D_tls)
+    debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n");
+  return OK;
+  }

 
 

-  DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
-    cas_expanded, statbuf.st_size);
+if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0)
+  {
+  log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s "
+      "(tls_verify_certificates): %s", state->exp_tls_verify_certificates,
+      strerror(errno));
+  return DEFER;
+  }

 
 

-  /* If the cert file is empty, there's no point in loading the CRL file. */
+/* The test suite passes in /dev/null; we could check for that path explicitly,
+but who knows if someone has some weird FIFO which always dumps some certs, or
+other weirdness.  The thing we really want to check is that it's not a
+directory, since while OpenSSL supports that, GnuTLS does not.
+So s/!S_ISREG/S_ISDIR/ and change some messsaging ... */
+if (S_ISDIR(statbuf.st_mode))
+  {
+  DEBUG(D_tls)
+    debug_printf("verify certificates path is a dir: \"%s\"\n",
+        state->exp_tls_verify_certificates);
+  log_write(0, LOG_MAIN|LOG_PANIC,
+      "tls_verify_certificates \"%s\" is a directory",
+      state->exp_tls_verify_certificates);
+  return DEFER;
+  }

 
 

-  if (statbuf.st_size > 0)
-    {
-    rc = gnutls_certificate_set_x509_trust_file(x509_cred, CS cas_expanded,
-      GNUTLS_X509_FMT_PEM);
-    if (rc < 0) return tls_error(US"setup_certs", host, gnutls_strerror(rc));
+DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
+        state->exp_tls_verify_certificates, statbuf.st_size);

 
 

-    if (crl != NULL && *crl != 0)
-      {
-      if (!expand_check(crl, US"tls_crl", &crl_expanded))
-        return DEFER;
-      DEBUG(D_tls) debug_printf("loading CRL file = %s\n", crl_expanded);
-      rc = gnutls_certificate_set_x509_crl_file(x509_cred, CS crl_expanded,
-        GNUTLS_X509_FMT_PEM);
-      if (rc < 0) return tls_error(US"CRL setup", host, gnutls_strerror(rc));
-      }
-    }
+if (statbuf.st_size == 0)
+  {
+  DEBUG(D_tls)
+    debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n");
+  return OK;

   }
 
   }
 

-/* Associate the parameters with the x509 credentials structure. */
+cert_count = gnutls_certificate_set_x509_trust_file(state->x509_cred,
+    CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM);
+if (cert_count < 0)
+  {
+  rc = cert_count;
+  exim_gnutls_err_check(US"gnutls_certificate_set_x509_trust_file");
+  }
+DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count);

 
 

-gnutls_certificate_set_dh_params(x509_cred, dh_params);
+if (state->tls_crl && *state->tls_crl &&
+    state->exp_tls_crl && *state->exp_tls_crl)
+  {
+  DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl);
+  cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred,
+      CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM);
+  if (cert_count < 0)
+    {
+    rc = cert_count;
+    exim_gnutls_err_check(US"gnutls_certificate_set_x509_crl_file");
+    }
+  DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
+  }

 
 

-DEBUG(D_tls) debug_printf("initialized certificate stuff\n");

 return OK;
 }
 
 return OK;
 }
 


@@ -563,290 +826,534 @@ return OK;
 
 
 /*************************************************
 
 
 /*************************************************

-*           Remove from a priority list          *
+*          Set X.509 state variables             *

 *************************************************/
 
 *************************************************/
 

-/* Cautiously written so that it will remove duplicates if present.
+/* In GnuTLS, the registered cert/key are not replaced by a later
+set of a cert/key, so for SNI support we need a whole new x509_cred
+structure.  Which means various other non-re-expanded pieces of state
+need to be re-set in the new struct, so the setting logic is pulled
+out to this.

 
 Arguments:
 
 Arguments:

-  list         a zero-terminated list
-  remove_list  a zero-terminated list to be removed
+  state           exim_gnutls_state_st *

 
 

-Returns:       nothing
+Returns:          OK/DEFER/FAIL

 */
 
 */
 

-static void
-remove_priority(int *list, int *remove_list)
+static int
+tls_set_remaining_x509(exim_gnutls_state_st *state)

 {
 {

-for (; *remove_list != 0; remove_list++)
+int rc;
+const host_item *host = state->host;  /* macro should be reconsidered? */
+
+/* Create D-H parameters, or read them from the cache file. This function does
+its own SMTP error messaging. This only happens for the server, TLS D-H ignores
+client-side params. */
+
+if (!state->host)

   {
   {

-  int *p = list;
-  while (*p != 0)
+  if (!dh_server_params)

     {
     {

-    if (*p == *remove_list)
-      {
-      int *pp = p;
-      do { pp[0] = pp[1]; pp++; } while (*pp != 0);
-      }
-    else p++;
+    rc = init_server_dh();
+    if (rc != OK) return rc;

     }
     }

+  gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);

   }
   }

-}

 
 

+/* Link the credentials to the session. */

 
 

+rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred);
+exim_gnutls_err_check(US"gnutls_credentials_set");
+
+return OK;
+}

 
 /*************************************************
 
 /*************************************************

-*            Add to a priority list              *
+*            Initialize for GnuTLS               *

 *************************************************/
 
 *************************************************/
 

-/* Cautiously written to check the list size
+/* Called from both server and client code. In the case of a server, errors
+before actual TLS negotiation return DEFER.

 
 Arguments:
 
 Arguments:

-  list         a zero-terminated list
-  list_max     maximum offset in the list
-  add_list     a zero-terminated list to be added
+  host            connected host, if client; NULL if server
+  certificate     certificate file
+  privatekey      private key file
+  sni             TLS SNI to send, sometimes when client; else NULL
+  cas             CA certs file
+  crl             CRL file
+  require_ciphers tls_require_ciphers setting
+  caller_state    returned state-info structure

 
 

-Returns:       TRUE if OK; FALSE if list overflows
+Returns:          OK/DEFER/FAIL

 */
 
 */
 

-static BOOL
-add_priority(int *list, int list_max, int *add_list)
+static int
+tls_init(
+    const host_item *host,
+    const uschar *certificate,
+    const uschar *privatekey,
+    const uschar *sni,
+    const uschar *cas,
+    const uschar *crl,
+    const uschar *require_ciphers,
+    exim_gnutls_state_st **caller_state)

 {
 {

-int next = 0;
-while (list[next] != 0) next++;
-while (*add_list != 0)
+exim_gnutls_state_st *state;
+int rc;
+size_t sz;
+const char *errpos;
+uschar *p;
+BOOL want_default_priorities;
+
+if (!exim_gnutls_base_init_done)

   {
   {

-  if (next >= list_max) return FALSE;
-  list[next++] = *add_list++;
+  DEBUG(D_tls) debug_printf("GnuTLS global init required.\n");
+
+  rc = gnutls_global_init();
+  exim_gnutls_err_check(US"gnutls_global_init");
+
+#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
+  DEBUG(D_tls)
+    {
+    gnutls_global_set_log_function(exim_gnutls_logger_cb);
+    /* arbitrarily chosen level; bump upto 9 for more */
+    gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
+    }
+#endif
+
+  exim_gnutls_base_init_done = TRUE;

   }
   }

-list[next] = 0;
-return TRUE;
-}

 
 

+if (host)
+  {
+  state = &state_client;
+  memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
+  state->tlsp = &tls_out;
+  DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
+  rc = gnutls_init(&state->session, GNUTLS_CLIENT);
+  }
+else
+  {
+  state = &state_server;
+  memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
+  state->tlsp = &tls_in;
+  DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
+  rc = gnutls_init(&state->session, GNUTLS_SERVER);
+  }
+exim_gnutls_err_check(US"gnutls_init");

 
 

+state->host = host;

 
 

-/*************************************************
-*          Adjust a priority list                *
-*************************************************/
+state->tls_certificate = certificate;
+state->tls_privatekey = privatekey;
+state->tls_require_ciphers = require_ciphers;
+state->tls_sni = sni;
+state->tls_verify_certificates = cas;
+state->tls_crl = crl;

 
 

-/* This function is called to adjust the lists of cipher algorithms, MAC
-algorithms, key-exchange methods, and protocols.
+/* This handles the variables that might get re-expanded after TLS SNI;
+that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */

 
 

-Arguments:
-  plist       the appropriate priority list
-  psize       the length of the list
-  s           the configuation string
-  index       the index of recognized strings
-  isize       the length of the index
+DEBUG(D_tls)
+  debug_printf("Expanding various TLS configuration options for session credentials.\n");
+rc = tls_expand_session_files(state);
+if (rc != OK) return rc;

 
 

+/* These are all other parts of the x509_cred handling, since SNI in GnuTLS
+requires a new structure afterwards. */

 
 

-  which       text for an error message
+rc = tls_set_remaining_x509(state);
+if (rc != OK) return rc;

 
 

-Returns:      FALSE if the table overflows, else TRUE
-*/
+/* set SNI in client, only */
+if (host)
+  {
+  if (!expand_check(state->tlsp->sni, "tls_out_sni", &state->exp_tls_sni))
+    return DEFER;
+  if (state->exp_tls_sni && *state->exp_tls_sni)
+    {
+    DEBUG(D_tls)
+      debug_printf("Setting TLS client SNI to \"%s\"\n", state->exp_tls_sni);
+    sz = Ustrlen(state->exp_tls_sni);
+    rc = gnutls_server_name_set(state->session,
+        GNUTLS_NAME_DNS, state->exp_tls_sni, sz);
+    exim_gnutls_err_check(US"gnutls_server_name_set");
+    }
+  }
+else if (state->tls_sni)
+  DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \
+      "have an SNI set for a client [%s]\n", state->tls_sni);

 
 

-static BOOL
-set_priority(int *plist, int psize, uschar *s, pri_item *index, int isize,
-   uschar *which)
-{
-int sep = 0;
-BOOL first = TRUE;
-uschar *t;
+/* This is the priority string support,
+http://www.gnu.org/software/gnutls/manual/html_node/Priority-Strings.html
+and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
+This was backwards incompatible, but means Exim no longer needs to track
+all algorithms and provide string forms for them. */
+
+want_default_priorities = TRUE;

 
 

-while ((t = string_nextinlist(&s, &sep, big_buffer, big_buffer_size)) != NULL)
+if (state->tls_require_ciphers && *state->tls_require_ciphers)

   {
   {

-  int i;
-  BOOL exclude = t[0] == '!';
-  if (first && !exclude) plist[0] = 0;
-  first = FALSE;
-  for (i = 0; i < isize; i++)
+  if (!expand_check_tlsvar(tls_require_ciphers))
+    return DEFER;
+  if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)

     {
     {

-    uschar *ss = strstric(t, index[i].name, FALSE);
-    if (ss != NULL)
-      {
-      uschar *endss = ss + Ustrlen(index[i].name);
-      if ((ss == t || !isalnum(ss[-1])) && !isalnum(*endss))
-        {
-        if (exclude)
-          remove_priority(plist, index[i].values);
-        else
-          {
-          if (!add_priority(plist, psize, index[i].values))
-            {
-            log_write(0, LOG_MAIN|LOG_PANIC, "GnuTLS init failed: %s "
-              "priority table overflow", which);
-            return FALSE;
-            }
-          }
-        }
-      }
+    DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n",
+        state->exp_tls_require_ciphers);
+
+    rc = gnutls_priority_init(&state->priority_cache,
+        CS state->exp_tls_require_ciphers, &errpos);
+    want_default_priorities = FALSE;
+    p = state->exp_tls_require_ciphers;

     }
   }
     }
   }

+if (want_default_priorities)
+  {
+  DEBUG(D_tls)
+    debug_printf("GnuTLS using default session cipher/priority \"%s\"\n",
+        exim_default_gnutls_priority);
+  rc = gnutls_priority_init(&state->priority_cache,
+      exim_default_gnutls_priority, &errpos);
+  p = US exim_default_gnutls_priority;
+  }

 
 

-DEBUG(D_tls)
+exim_gnutls_err_check(string_sprintf(
+      "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
+      p, errpos - CS p, errpos));
+
+rc = gnutls_priority_set(state->session, state->priority_cache);
+exim_gnutls_err_check(US"gnutls_priority_set");
+
+gnutls_db_set_cache_expiration(state->session, ssl_session_timeout);
+
+/* Reduce security in favour of increased compatibility, if the admin
+decides to make that trade-off. */
+if (gnutls_compat_mode)

   {
   {

-  int *ptr = plist;
-  debug_printf("adjusted %s priorities:", which);
-  while (*ptr != 0) debug_printf(" %d", *ptr++);
-  debug_printf("\n");
+#if LIBGNUTLS_VERSION_NUMBER >= 0x020104
+  DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
+  gnutls_session_enable_compatibility_mode(state->session);
+#else
+  DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
+#endif

   }
 
   }
 

-return TRUE;
+*caller_state = state;
+return OK;

 }
 
 
 
 
 /*************************************************
 }
 
 
 
 
 /*************************************************

-*        Initialize a single GNUTLS session      *
+*            Extract peer information            *

 *************************************************/
 
 *************************************************/
 

-/* Set the algorithm, the db backend, whether to request certificates etc.
+/* Called from both server and client code.
+Only this is allowed to set state->peerdn and state->have_set_peerdn
+and we use that to detect double-calls.
+
+NOTE: the state blocks last while the TLS connection is up, which is fine
+for logging in the server side, but for the client side, we log after teardown
+in src/deliver.c.  While the session is up, we can twist about states and
+repoint tls_* globals, but those variables used for logging or other variable
+expansion that happens _after_ delivery need to have a longer life-time.

 
 

-TLS in Exim was first implemented using OpenSSL. This has a function to which
-you pass a list of cipher suites that are permitted/not permitted. GnuTLS works
-differently. It operates using priority lists for the different components of
-cipher suites.
+So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from
+doing this more than once per generation of a state context.  We set them in
+the state context, and repoint tls_* to them.  After the state goes away, the
+tls_* copies of the pointers remain valid and client delivery logging is happy.

 
 

-For compatibility of configuration, we scan a list of cipher suites and set
-priorities therefrom. However, at the moment, we pay attention only to the bulk
-cipher.
+tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues
+don't apply.

 
 Arguments:
 
 Arguments:

-  side         one of GNUTLS_SERVER, GNUTLS_CLIENT
-  expciphers   expanded ciphers list or NULL
-  expmac       expanded MAC list or NULL
-  expkx        expanded key-exchange list or NULL
-  expproto     expanded protocol list or NULL
+  state           exim_gnutls_state_st *

 
 

-Returns:  a gnutls_session, or NULL if there is a problem
+Returns:          OK/DEFER/FAIL

 */
 
 */
 

-static gnutls_session
-tls_session_init(int side, uschar *expciphers, uschar *expmac, uschar *expkx,
-  uschar *expproto)
+static int
+peer_status(exim_gnutls_state_st *state)

 {
 {

-gnutls_session session;
-
-gnutls_init(&session, side);
+uschar cipherbuf[256];
+const gnutls_datum *cert_list;
+int old_pool, rc;
+unsigned int cert_list_size = 0;
+gnutls_protocol_t protocol;
+gnutls_cipher_algorithm_t cipher;
+gnutls_kx_algorithm_t kx;
+gnutls_mac_algorithm_t mac;
+gnutls_certificate_type_t ct;
+gnutls_x509_crt_t crt;
+uschar *p, *dn_buf;
+size_t sz;
+
+if (state->have_set_peerdn)
+  return OK;
+state->have_set_peerdn = TRUE;
+
+state->peerdn = NULL;
+
+/* tls_cipher */
+cipher = gnutls_cipher_get(state->session);
+protocol = gnutls_protocol_get_version(state->session);
+mac = gnutls_mac_get(state->session);
+kx = gnutls_kx_get(state->session);
+
+string_format(cipherbuf, sizeof(cipherbuf),
+    "%s:%s:%d",
+    gnutls_protocol_get_name(protocol),
+    gnutls_cipher_suite_get_name(kx, cipher, mac),
+    (int) gnutls_cipher_get_key_size(cipher) * 8);
+
+/* I don't see a way that spaces could occur, in the current GnuTLS
+code base, but it was a concern in the old code and perhaps older GnuTLS
+releases did return "TLS 1.0"; play it safe, just in case. */
+for (p = cipherbuf; *p != '\0'; ++p)
+  if (isspace(*p))
+    *p = '-';
+old_pool = store_pool;
+store_pool = POOL_PERM;
+state->ciphersuite = string_copy(cipherbuf);
+store_pool = old_pool;
+state->tlsp->cipher = state->ciphersuite;
+
+/* tls_peerdn */
+cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size);
+
+if (cert_list == NULL || cert_list_size == 0)
+  {
+  DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n",
+      cert_list, cert_list_size);
+  if (state->verify_requirement == VERIFY_REQUIRED)
+    return tls_error(US"certificate verification failed",
+        "no certificate received from peer", state->host);
+  return OK;
+  }

 
 

-/* Initialize the lists of permitted protocols, key-exchange methods, ciphers,
-and MACs. */
+ct = gnutls_certificate_type_get(state->session);
+if (ct != GNUTLS_CRT_X509)
+  {
+  const char *ctn = gnutls_certificate_type_get_name(ct);
+  DEBUG(D_tls)
+    debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn);
+  if (state->verify_requirement == VERIFY_REQUIRED)
+    return tls_error(US"certificate verification not possible, unhandled type",
+        ctn, state->host);
+  return OK;
+  }

 
 

-memcpy(cipher_priority, default_cipher_priority, sizeof(cipher_priority));
-memcpy(mac_priority, default_mac_priority, sizeof(mac_priority));
-memcpy(kx_priority, default_kx_priority, sizeof(kx_priority));
-memcpy(proto_priority, default_proto_priority, sizeof(proto_priority));
+#define exim_gnutls_peer_err(Label) do { \
+  if (rc != GNUTLS_E_SUCCESS) { \
+    DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", (Label), gnutls_strerror(rc)); \
+    if (state->verify_requirement == VERIFY_REQUIRED) { return tls_error((Label), gnutls_strerror(rc), state->host); } \
+    return OK; } } while (0)

 
 

-/* The names OpenSSL uses in tls_require_ciphers are of the form DES-CBC3-SHA,
-using hyphen separators. GnuTLS uses underscore separators. So that I can use
-either form for tls_require_ciphers in my tests, and also for general
-convenience, we turn hyphens into underscores before scanning the list. */
+rc = gnutls_x509_crt_init(&crt);
+exim_gnutls_peer_err(US"gnutls_x509_crt_init (crt)");

 
 

-if (expciphers != NULL)
+rc = gnutls_x509_crt_import(crt, &cert_list[0], GNUTLS_X509_FMT_DER);
+exim_gnutls_peer_err(US"failed to import certificate [gnutls_x509_crt_import(cert 0)]");
+sz = 0;
+rc = gnutls_x509_crt_get_dn(crt, NULL, &sz);
+if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)

   {
   {

-  uschar *s = expciphers;
-  while (*s != 0) { if (*s == '-') *s = '_'; s++; }
+  exim_gnutls_peer_err(US"getting size for cert DN failed");
+  return FAIL; /* should not happen */

   }
   }

+dn_buf = store_get_perm(sz);
+rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz);
+exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]");
+state->peerdn = dn_buf;

 
 

-if ((expciphers != NULL &&
-      !set_priority(cipher_priority, sizeof(cipher_priority)/sizeof(int),
-        expciphers, cipher_index, sizeof(cipher_index)/sizeof(pri_item),
-        US"cipher")) ||
-    (expmac != NULL &&
-      !set_priority(mac_priority, sizeof(mac_priority)/sizeof(int),
-        expmac, mac_index, sizeof(mac_index)/sizeof(pri_item),
-        US"MAC")) ||
-    (expkx != NULL &&
-      !set_priority(kx_priority, sizeof(kx_priority)/sizeof(int),
-        expkx, kx_index, sizeof(kx_index)/sizeof(pri_item),
-        US"key-exchange")) ||
-    (expproto != NULL &&
-      !set_priority(proto_priority, sizeof(proto_priority)/sizeof(int),
-        expproto, proto_index, sizeof(proto_index)/sizeof(pri_item),
-        US"protocol")))
-  {
-  gnutls_deinit(session);
-  return NULL;
-  }
+return OK;
+#undef exim_gnutls_peer_err
+}

 
 

-/* Define the various priorities */

 
 

-gnutls_cipher_set_priority(session, cipher_priority);
-gnutls_compression_set_priority(session, comp_priority);
-gnutls_kx_set_priority(session, kx_priority);
-gnutls_protocol_set_priority(session, proto_priority);
-gnutls_mac_set_priority(session, mac_priority);

 
 

-gnutls_cred_set(session, GNUTLS_CRD_CERTIFICATE, x509_cred);

 
 

-gnutls_dh_set_prime_bits(session, DH_BITS);
+/*************************************************
+*            Verify peer certificate             *
+*************************************************/

 
 

-/* Request or demand a certificate of the peer, as configured. This will
-happen only in a server. */
+/* Called from both server and client code.
+*Should* be using a callback registered with
+gnutls_certificate_set_verify_function() to fail the handshake if we dislike
+the peer information, but that's too new for some OSes.

 
 

-if (verify_requirement != VERIFY_NONE)
-  gnutls_certificate_server_set_request(session,
-    (verify_requirement == VERIFY_OPTIONAL)?
-      GNUTLS_CERT_REQUEST : GNUTLS_CERT_REQUIRE);
+Arguments:
+  state           exim_gnutls_state_st *
+  error           where to put an error message

 
 

-gnutls_db_set_cache_expiration(session, ssl_session_timeout);
+Returns:
+  FALSE     if the session should be rejected
+  TRUE      if the cert is okay or we just don't care
+*/

 
 

-/* Reduce security in favour of increased compatibility, if the admin
-decides to make that trade-off. */
-if (gnutls_compat_mode)
+static BOOL
+verify_certificate(exim_gnutls_state_st *state, const char **error)
+{
+int rc;
+unsigned int verify;
+
+*error = NULL;
+
+rc = peer_status(state);
+if (rc != OK)

   {
   {

-#if LIBGNUTLS_VERSION_NUMBER >= 0x020104
-  DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
-  gnutls_session_enable_compatibility_mode(session);
-#else
-  DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
-#endif
+  verify = GNUTLS_CERT_INVALID;
+  *error = "not supplied";
+  }
+else
+  {
+  rc = gnutls_certificate_verify_peers2(state->session, &verify);
+  }
+
+/* Handle the result of verification. INVALID seems to be set as well
+as REVOKED, but leave the test for both. */
+
+if ((rc < 0) || (verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED)) != 0)
+  {
+  state->peer_cert_verified = FALSE;
+  if (*error == NULL)
+    *error = ((verify & GNUTLS_CERT_REVOKED) != 0) ? "revoked" : "invalid";
+
+  DEBUG(D_tls)
+    debug_printf("TLS certificate verification failed (%s): peerdn=%s\n",
+        *error, state->peerdn ? state->peerdn : US"<unset>");
+
+  if (state->verify_requirement == VERIFY_REQUIRED)
+    {
+    gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
+    return FALSE;
+    }
+  DEBUG(D_tls)
+    debug_printf("TLS verify failure overridden (host in tls_try_verify_hosts)\n");
+  }
+else
+  {
+  state->peer_cert_verified = TRUE;
+  DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=%s\n",
+      state->peerdn ? state->peerdn : US"<unset>");

   }
 
   }
 

-DEBUG(D_tls) debug_printf("initialized GnuTLS session\n");
-return session;
+state->tlsp->peerdn = state->peerdn;
+
+return TRUE;

 }
 
 
 
 }
 
 
 

-/*************************************************
-*           Get name of cipher in use            *
-*************************************************/

 
 

-/* The answer is left in a static buffer, and tls_cipher is set to point
-to it.
+/* ------------------------------------------------------------------------ */
+/* Callbacks */

 
 

-Argument:   pointer to a GnuTLS session
-Returns:    nothing
+/* Logging function which can be registered with
+ *   gnutls_global_set_log_function()
+ *   gnutls_global_set_log_level() 0..9
+ */
+#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
+static void
+exim_gnutls_logger_cb(int level, const char *message)
+{
+  size_t len = strlen(message);
+  if (len < 1)
+    {
+    DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
+    return;
+    }
+  DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
+      message[len-1] == '\n' ? "" : "\n");
+}
+#endif
+
+
+/* Called after client hello, should handle SNI work.
+This will always set tls_sni (state->received_sni) if available,
+and may trigger presenting different certificates,
+if state->trigger_sni_changes is TRUE.
+
+Should be registered with
+  gnutls_handshake_set_post_client_hello_function()
+
+"This callback must return 0 on success or a gnutls error code to terminate the
+handshake.".
+
+For inability to get SNI information, we return 0.
+We only return non-zero if re-setup failed.
+Only used for server-side TLS.

 */
 
 */
 

-static void
-construct_cipher_name(gnutls_session session)
+static int
+exim_sni_handling_cb(gnutls_session_t session)

 {
 {

-static uschar cipherbuf[256];
-uschar *ver;
-int bits, c, kx, mac;
+char sni_name[MAX_HOST_LEN];
+size_t data_len = MAX_HOST_LEN;
+exim_gnutls_state_st *state = &state_server;
+unsigned int sni_type;
+int rc, old_pool;
+
+rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0);
+if (rc != GNUTLS_E_SUCCESS)
+  {
+  DEBUG(D_tls) {
+    if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
+      debug_printf("TLS: no SNI presented in handshake.\n");
+    else
+      debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n",
+        gnutls_strerror(rc), rc);
+  };
+  return 0;
+  }
+
+if (sni_type != GNUTLS_NAME_DNS)
+  {
+  DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type);
+  return 0;
+  }
+
+/* We now have a UTF-8 string in sni_name */
+old_pool = store_pool;
+store_pool = POOL_PERM;
+state->received_sni = string_copyn(US sni_name, data_len);
+store_pool = old_pool;

 
 

-ver = string_copy(
-  US gnutls_protocol_get_name(gnutls_protocol_get_version(session)));
-if (Ustrncmp(ver, "TLS ", 4) == 0) ver[3] = '-';   /* Don't want space */
+/* We set this one now so that variable expansions below will work */
+state->tlsp->sni = state->received_sni;

 
 

-c = gnutls_cipher_get(session);
-bits = gnutls_cipher_get_key_size(c);
+DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name,
+    state->trigger_sni_changes ? "" : " (unused for certificate selection)");

 
 

-mac = gnutls_mac_get(session);
-kx = gnutls_kx_get(session);
+if (!state->trigger_sni_changes)
+  return 0;

 
 

-string_format(cipherbuf, sizeof(cipherbuf), "%s:%s:%u", ver,
-  gnutls_cipher_suite_get_name(kx, c, mac), bits);
-tls_cipher = cipherbuf;
+rc = tls_expand_session_files(state);
+if (rc != OK)
+  {
+  /* If the setup of certs/etc failed before handshake, TLS would not have
+  been offered.  The best we can do now is abort. */
+  return GNUTLS_E_APPLICATION_ERROR_MIN;
+  }

 
 

-DEBUG(D_tls) debug_printf("cipher: %s\n", cipherbuf);
+rc = tls_set_remaining_x509(state);
+if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN;
+
+return 0;

 }
 
 
 
 }
 
 
 

+
+/* ------------------------------------------------------------------------ */
+/* Exported functions */
+
+
+
+

 /*************************************************
 *       Start a TLS session in a server          *
 *************************************************/
 /*************************************************
 *       Start a TLS session in a server          *
 *************************************************/


@@ -857,9 +1364,6 @@ a TLS session.
 
 Arguments:
   require_ciphers  list of allowed ciphers or NULL
 
 Arguments:
   require_ciphers  list of allowed ciphers or NULL

-  require_mac      list of allowed MACs or NULL
-  require_kx       list of allowed key_exchange methods or NULL
-  require_proto    list of allowed protocols or NULL

 
 Returns:           OK on success
                    DEFER for errors before the start of the negotiation
 
 Returns:           OK on success
                    DEFER for errors before the start of the negotiation


@@ -868,21 +1372,16 @@ Returns:           OK on success
 */
 
 int
 */
 
 int

-tls_server_start(uschar *require_ciphers, uschar *require_mac,
-  uschar *require_kx, uschar *require_proto)
+tls_server_start(const uschar *require_ciphers)

 {
 int rc;
 const char *error;
 {
 int rc;
 const char *error;

-uschar *expciphers = NULL;
-uschar *expmac = NULL;
-uschar *expkx = NULL;
-uschar *expproto = NULL;
+exim_gnutls_state_st *state = NULL;

 
 /* Check for previous activation */
 
 /* Check for previous activation */

-
-if (tls_active >= 0)
+if (tls_in.active >= 0)

   {
   {

-  tls_error("STARTTLS received after TLS started", NULL, "");
+  tls_error(US"STARTTLS received after TLS started", "", NULL);

   smtp_printf("554 Already in TLS\r\n");
   return FAIL;
   }
   smtp_printf("554 Already in TLS\r\n");
   return FAIL;
   }


@@ -890,36 +1389,40 @@ if (tls_active >= 0)
 /* Initialize the library. If it fails, it will already have logged the error
 and sent an SMTP response. */
 
 /* Initialize the library. If it fails, it will already have logged the error
 and sent an SMTP response. */
 

-DEBUG(D_tls) debug_printf("initializing GnuTLS as a server\n");
+DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n");

 
 

-rc = tls_init(NULL, tls_certificate, tls_privatekey, tls_verify_certificates,
-  tls_crl);
+rc = tls_init(NULL, tls_certificate, tls_privatekey,
+    NULL, tls_verify_certificates, tls_crl,
+    require_ciphers, &state);

 if (rc != OK) return rc;
 
 if (rc != OK) return rc;
 

-if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers) ||
-    !expand_check(require_mac, US"gnutls_require_mac", &expmac) ||
-    !expand_check(require_kx, US"gnutls_require_kx", &expkx) ||
-    !expand_check(require_proto, US"gnutls_require_proto", &expproto))
-  return FAIL;
-

 /* If this is a host for which certificate verification is mandatory or
 optional, set up appropriately. */
 
 /* If this is a host for which certificate verification is mandatory or
 optional, set up appropriately. */
 

-tls_certificate_verified = FALSE;
-verify_requirement = VERIFY_NONE;
-

 if (verify_check_host(&tls_verify_hosts) == OK)
 if (verify_check_host(&tls_verify_hosts) == OK)

-  verify_requirement = VERIFY_REQUIRED;
+  {
+  DEBUG(D_tls) debug_printf("TLS: a client certificate will be required.\n");
+  state->verify_requirement = VERIFY_REQUIRED;
+  gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
+  }

 else if (verify_check_host(&tls_try_verify_hosts) == OK)
 else if (verify_check_host(&tls_try_verify_hosts) == OK)

-  verify_requirement = VERIFY_OPTIONAL;
+  {
+  DEBUG(D_tls) debug_printf("TLS: a client certificate will be requested but not required.\n");
+  state->verify_requirement = VERIFY_OPTIONAL;
+  gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
+  }
+else
+  {
+  DEBUG(D_tls) debug_printf("TLS: a client certificate will not be requested.\n");
+  state->verify_requirement = VERIFY_NONE;
+  gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
+  }

 
 

-/* Prepare for new connection */
+/* Register SNI handling; always, even if not in tls_certificate, so that the
+expansion variable $tls_sni is always available. */

 
 

-tls_session = tls_session_init(GNUTLS_SERVER, expciphers, expmac, expkx,
-  expproto);
-if (tls_session == NULL)
-  return tls_error(US"tls_session_init", NULL,
-    gnutls_strerror(GNUTLS_E_MEMORY_ERROR));
+gnutls_handshake_set_post_client_hello_function(state->session,
+    exim_sni_handling_cb);

 
 /* Set context and tell client to go ahead, except in the case of TLS startup
 on connection, where outputting anything now upsets the clients and tends to
 
 /* Set context and tell client to go ahead, except in the case of TLS startup
 on connection, where outputting anything now upsets the clients and tends to


@@ -927,28 +1430,34 @@ make them disconnect. We need to have an explicit fflush() here, to force out
 the response. Other smtp_printf() calls do not need it, because in non-TLS
 mode, the fflush() happens when smtp_getc() is called. */
 
 the response. Other smtp_printf() calls do not need it, because in non-TLS
 mode, the fflush() happens when smtp_getc() is called. */
 

-if (!tls_on_connect)
+if (!state->tlsp->on_connect)

   {
   smtp_printf("220 TLS go ahead\r\n");
   {
   smtp_printf("220 TLS go ahead\r\n");

-  fflush(smtp_out);
+  fflush(smtp_out);            /*XXX JGH */

   }
 
 /* Now negotiate the TLS session. We put our own timer on it, since it seems
 that the GnuTLS library doesn't. */
 
   }
 
 /* Now negotiate the TLS session. We put our own timer on it, since it seems
 that the GnuTLS library doesn't. */
 

-gnutls_transport_set_ptr2(tls_session, (gnutls_transport_ptr)fileno(smtp_in),
-                                       (gnutls_transport_ptr)fileno(smtp_out));
+gnutls_transport_set_ptr2(state->session,
+    (gnutls_transport_ptr)fileno(smtp_in),
+    (gnutls_transport_ptr)fileno(smtp_out));
+state->fd_in = fileno(smtp_in);
+state->fd_out = fileno(smtp_out);

 
 sigalrm_seen = FALSE;
 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
 
 sigalrm_seen = FALSE;
 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);

-rc = gnutls_handshake(tls_session);
+do
+  {
+  rc = gnutls_handshake(state->session);
+  } while ((rc == GNUTLS_E_AGAIN) ||
+      (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen));

 alarm(0);
 
 alarm(0);
 

-if (rc < 0)
+if (rc != GNUTLS_E_SUCCESS)

   {
   {

-  tls_error(US"gnutls_handshake", NULL,
-    sigalrm_seen ? "timed out" : gnutls_strerror(rc));
-
+  tls_error(US"gnutls_handshake",
+      sigalrm_seen ? "timed out" : gnutls_strerror(rc), NULL);

   /* It seems that, except in the case of a timeout, we have to close the
   connection right here; otherwise if the other end is running OpenSSL it hangs
   until the server times out. */
   /* It seems that, except in the case of a timeout, we have to close the
   connection right here; otherwise if the other end is running OpenSSL it hangs
   until the server times out. */


@@ -964,21 +1473,39 @@ if (rc < 0)
 
 DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
 
 
 DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
 

-if (verify_requirement != VERIFY_NONE &&
-     !verify_certificate(tls_session, &error))
+/* Verify after the fact */
+
+if (state->verify_requirement != VERIFY_NONE)

   {
   {

-  tls_error(US"certificate verification failed", NULL, error);
-  return FAIL;
+  if (!verify_certificate(state, &error))
+    {
+    if (state->verify_requirement == VERIFY_OPTIONAL)
+      {
+      DEBUG(D_tls)
+        debug_printf("TLS: continuing on only because verification was optional, after: %s\n",
+            error);
+      }
+    else
+      {
+      tls_error(US"certificate verification failed", error, NULL);
+      return FAIL;
+      }
+    }

   }
 
   }
 

-construct_cipher_name(tls_session);
+/* Figure out peer DN, and if authenticated, etc. */
+
+rc = peer_status(state);
+if (rc != OK) return rc;
+
+/* Sets various Exim expansion variables; always safe within server */
+
+extract_exim_vars_from_tls_state(state, TRUE);

 
 /* TLS has been set up. Adjust the input functions to read via TLS,
 and initialize appropriately. */
 
 
 /* TLS has been set up. Adjust the input functions to read via TLS,
 and initialize appropriately. */
 

-ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
-ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
-ssl_xfer_eof = ssl_xfer_error = 0;
+state->xfer_buffer = store_malloc(ssl_xfer_buffer_size);

 
 receive_getc = tls_getc;
 receive_ungetc = tls_ungetc;
 
 receive_getc = tls_getc;
 receive_ungetc = tls_ungetc;


@@ -986,8 +1513,6 @@ receive_feof = tls_feof;
 receive_ferror = tls_ferror;
 receive_smtp_buffered = tls_smtp_buffered;
 
 receive_ferror = tls_ferror;
 receive_smtp_buffered = tls_smtp_buffered;
 

-tls_active = fileno(smtp_out);
-

 return OK;
 }
 
 return OK;
 }
 


@@ -1004,15 +1529,14 @@ Arguments:
   fd                the fd of the connection
   host              connected host (for messages)
   addr              the first address (not used)
   fd                the fd of the connection
   host              connected host (for messages)
   addr              the first address (not used)

-  dhparam           DH parameter file
+  dhparam           DH parameter file (ignored, we're a client)

   certificate       certificate file
   privatekey        private key file
   certificate       certificate file
   privatekey        private key file

+  sni               TLS SNI to send to remote host

   verify_certs      file for certificate verify
   verify_crl        CRL for verify
   require_ciphers   list of allowed ciphers or NULL
   verify_certs      file for certificate verify
   verify_crl        CRL for verify
   require_ciphers   list of allowed ciphers or NULL

-  require_mac       list of allowed MACs or NULL
-  require_kx        list of allowed key_exchange methods or NULL
-  require_proto     list of allowed protocols or NULL
+  dh_min_bits       minimum number of bits acceptable in server's DH prime

   timeout           startup timeout
 
 Returns:            OK/DEFER/FAIL (because using common functions),
   timeout           startup timeout
 
 Returns:            OK/DEFER/FAIL (because using common functions),


@@ -1020,119 +1544,140 @@ Returns:            OK/DEFER/FAIL (because using common functions),
 */
 
 int
 */
 
 int

-tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam,
-  uschar *certificate, uschar *privatekey, uschar *verify_certs,
-  uschar *verify_crl, uschar *require_ciphers, uschar *require_mac,
-  uschar *require_kx, uschar *require_proto, int timeout)
+tls_client_start(int fd, host_item *host,
+    address_item *addr ARG_UNUSED, uschar *dhparam ARG_UNUSED,
+    uschar *certificate, uschar *privatekey, uschar *sni,
+    uschar *verify_certs, uschar *verify_crl,
+    uschar *require_ciphers, int dh_min_bits, int timeout)

 {
 {

-const gnutls_datum *server_certs;
-uschar *expciphers = NULL;
-uschar *expmac = NULL;
-uschar *expkx = NULL;
-uschar *expproto = NULL;
-const char *error;
-unsigned int server_certs_size;

 int rc;
 int rc;

+const char *error;
+exim_gnutls_state_st *state = NULL;

 
 

-DEBUG(D_tls) debug_printf("initializing GnuTLS as a client\n");
+DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd);

 
 

-verify_requirement = (verify_certs == NULL)? VERIFY_NONE : VERIFY_REQUIRED;
-rc = tls_init(host, certificate, privatekey, verify_certs, verify_crl);
+rc = tls_init(host, certificate, privatekey,
+    sni, verify_certs, verify_crl, require_ciphers, &state);

 if (rc != OK) return rc;
 
 if (rc != OK) return rc;
 

-if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers) ||
-    !expand_check(require_mac, US"gnutls_require_mac", &expmac) ||
-    !expand_check(require_kx, US"gnutls_require_kx", &expkx) ||
-    !expand_check(require_proto, US"gnutls_require_proto", &expproto))
-  return FAIL;
+if (dh_min_bits < EXIM_CLIENT_DH_MIN_MIN_BITS)
+  {
+  DEBUG(D_tls)
+    debug_printf("WARNING: tls_dh_min_bits far too low, clamping %d up to %d\n",
+        dh_min_bits, EXIM_CLIENT_DH_MIN_MIN_BITS);
+  dh_min_bits = EXIM_CLIENT_DH_MIN_MIN_BITS;
+  }

 
 

-tls_session = tls_session_init(GNUTLS_CLIENT, expciphers, expmac, expkx,
-  expproto);
+DEBUG(D_tls) debug_printf("Setting D-H prime minimum acceptable bits to %d\n",
+    dh_min_bits);
+gnutls_dh_set_prime_bits(state->session, dh_min_bits);

 
 

-if (tls_session == NULL)
-  return tls_error(US "tls_session_init", host,
-    gnutls_strerror(GNUTLS_E_MEMORY_ERROR));
+if (verify_certs == NULL)
+  {
+  DEBUG(D_tls) debug_printf("TLS: server certificate verification not required\n");
+  state->verify_requirement = VERIFY_NONE;
+  /* we still ask for it, to log it, etc */
+  gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
+  }
+else
+  {
+  DEBUG(D_tls) debug_printf("TLS: server certificate verification required\n");
+  state->verify_requirement = VERIFY_REQUIRED;
+  gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
+  }

 
 

-gnutls_transport_set_ptr(tls_session, (gnutls_transport_ptr)fd);
+gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr)fd);
+state->fd_in = fd;
+state->fd_out = fd;

 
 /* There doesn't seem to be a built-in timeout on connection. */
 
 sigalrm_seen = FALSE;
 alarm(timeout);
 
 /* There doesn't seem to be a built-in timeout on connection. */
 
 sigalrm_seen = FALSE;
 alarm(timeout);

-rc = gnutls_handshake(tls_session);
+do
+  {
+  rc = gnutls_handshake(state->session);
+  } while ((rc == GNUTLS_E_AGAIN) ||
+      (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen));

 alarm(0);
 
 alarm(0);
 

-if (rc < 0)
-  return tls_error(US "gnutls_handshake", host,
-    sigalrm_seen ? "timed out" : gnutls_strerror(rc));
+if (rc != GNUTLS_E_SUCCESS)
+  return tls_error(US"gnutls_handshake",
+      sigalrm_seen ? "timed out" : gnutls_strerror(rc), state->host);

 
 

-server_certs = gnutls_certificate_get_peers(tls_session, &server_certs_size);
+DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");

 
 

-if (server_certs != NULL)
-  {
-  uschar buff[1024];
-  gnutls_x509_crt gcert;
+/* Verify late */

 
 

-  gnutls_x509_crt_init(&gcert);
-  tls_peerdn = US"unknown";
+if (state->verify_requirement != VERIFY_NONE &&
+    !verify_certificate(state, &error))
+  return tls_error(US"certificate verification failed", error, state->host);

 
 

-  if (gnutls_x509_crt_import(gcert, server_certs, GNUTLS_X509_FMT_DER) == 0)
-    {
-    size_t bufsize = sizeof(buff);
-    if (gnutls_x509_crt_get_dn(gcert, CS buff, &bufsize) >= 0)
-      tls_peerdn = string_copy_malloc(buff);
-    }
-  }
+/* Figure out peer DN, and if authenticated, etc. */
+
+rc = peer_status(state);
+if (rc != OK) return rc;

 
 

-/* Should we also verify the hostname here? */
+/* Sets various Exim expansion variables; may need to adjust for ACL callouts */

 
 

-if (verify_requirement != VERIFY_NONE &&
-      !verify_certificate(tls_session, &error))
-  return tls_error(US"certificate verification failed", host, error);
+extract_exim_vars_from_tls_state(state, FALSE);

 
 

-construct_cipher_name(tls_session);    /* Sets tls_cipher */
-tls_active = fd;

 return OK;
 }
 
 
 
 return OK;
 }
 
 
 

+

 /*************************************************
 /*************************************************

-*    Deal with logging errors during I/O         *
+*         Close down a TLS session               *

 *************************************************/
 
 *************************************************/
 

-/* We have to get the identity of the peer from saved data.
-
-Argument:
-  ec       the GnuTLS error code, or 0 if it's a local error
-  when     text identifying read or write
-  text     local error text when ec is 0
+/* This is also called from within a delivery subprocess forked from the
+daemon, to shut down the TLS library, without actually doing a shutdown (which
+would tamper with the TLS session in the parent process).

 
 

-Returns:   nothing
+Arguments:   TRUE if gnutls_bye is to be called
+Returns:     nothing

 */
 
 */
 

-static void
-record_io_error(int ec, uschar *when, uschar *text)
+void
+tls_close(BOOL is_server, BOOL shutdown)

 {
 {

-const char *msg;
+exim_gnutls_state_st *state = is_server ? &state_server : &state_client;

 
 

-if (ec == GNUTLS_E_FATAL_ALERT_RECEIVED)
-  msg = string_sprintf("%s: %s", gnutls_strerror(ec),
-    gnutls_alert_get_name(gnutls_alert_get(tls_session)));
-else
-  msg = gnutls_strerror(ec);
+if (!state->tlsp || state->tlsp->active < 0) return;  /* TLS was not active */
+
+if (shutdown)
+  {
+  DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS\n");
+  gnutls_bye(state->session, GNUTLS_SHUT_WR);
+  }
+
+gnutls_deinit(state->session);
+
+state->tlsp->active = -1;
+memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
+
+if ((state_server.session == NULL) && (state_client.session == NULL))
+  {
+  gnutls_global_deinit();
+  exim_gnutls_base_init_done = FALSE;
+  }

 
 

-tls_error(when, client_host, msg);

 }
 
 
 
 }
 
 
 

+

 /*************************************************
 *            TLS version of getc                 *
 *************************************************/
 
 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
 it refills the buffer via the GnuTLS reading function.
 /*************************************************
 *            TLS version of getc                 *
 *************************************************/
 
 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
 it refills the buffer via the GnuTLS reading function.

+Only used by the server-side TLS.
+
+This feeds DKIM and should be used for all message-body reads.

 
 Arguments:  none
 Returns:    the next character or EOF
 
 Arguments:  none
 Returns:    the next character or EOF


@@ -1141,15 +1686,16 @@ Returns:    the next character or EOF
 int
 tls_getc(void)
 {
 int
 tls_getc(void)
 {

-if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
+exim_gnutls_state_st *state = &state_server;
+if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)

   {
   {

-  int inbytes;
+  ssize_t inbytes;

 
 

-  DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%lx, %lx, %u)\n",
-    (long) tls_session, (long) ssl_xfer_buffer, ssl_xfer_buffer_size);
+  DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
+    state->session, state->xfer_buffer, ssl_xfer_buffer_size);

 
   if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
 
   if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);

-  inbytes = gnutls_record_recv(tls_session, CS ssl_xfer_buffer,
+  inbytes = gnutls_record_recv(state->session, state->xfer_buffer,

     ssl_xfer_buffer_size);
   alarm(0);
 
     ssl_xfer_buffer_size);
   alarm(0);
 


@@ -1167,11 +1713,14 @@ if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
     receive_ferror = smtp_ferror;
     receive_smtp_buffered = smtp_buffered;
 
     receive_ferror = smtp_ferror;
     receive_smtp_buffered = smtp_buffered;
 

-    gnutls_deinit(tls_session);
-    tls_session = NULL;
-    tls_active = -1;
-    tls_cipher = NULL;
-    tls_peerdn = NULL;
+    gnutls_deinit(state->session);
+    state->session = NULL;
+    state->tlsp->active = -1;
+    state->tlsp->bits = 0;
+    state->tlsp->certificate_verified = FALSE;
+    tls_channelbinding_b64 = NULL;     /*XXX JGH */
+    state->tlsp->cipher = NULL;
+    state->tlsp->peerdn = NULL;

 
     return smtp_getc();
     }
 
     return smtp_getc();
     }


@@ -1180,30 +1729,32 @@ if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
 
   else if (inbytes < 0)
     {
 
   else if (inbytes < 0)
     {

-    record_io_error(inbytes, US"recv", NULL);
-    ssl_xfer_error = 1;
+    record_io_error(state, (int) inbytes, US"recv", NULL);
+    state->xfer_error = 1;

     return EOF;
     }
 #ifndef DISABLE_DKIM
     return EOF;
     }
 #ifndef DISABLE_DKIM

-  dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
+  dkim_exim_verify_feed(state->xfer_buffer, inbytes);

 #endif
 #endif

-  ssl_xfer_buffer_hwm = inbytes;
-  ssl_xfer_buffer_lwm = 0;
+  state->xfer_buffer_hwm = (int) inbytes;
+  state->xfer_buffer_lwm = 0;

   }
 
   }
 

-

 /* Something in the buffer; return next uschar */
 
 /* Something in the buffer; return next uschar */
 

-return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
+return state->xfer_buffer[state->xfer_buffer_lwm++];

 }
 
 
 
 }
 
 
 

+

 /*************************************************
 *          Read bytes from TLS channel           *
 *************************************************/
 
 /*************************************************
 *          Read bytes from TLS channel           *
 *************************************************/
 

-/*
+/* This does not feed DKIM, so if the caller uses this for reading message body,
+then the caller must feed DKIM.
+

 Arguments:
   buff      buffer of data
   len       size of buffer
 Arguments:
   buff      buffer of data
   len       size of buffer


@@ -1213,32 +1764,45 @@ Returns:    the number of bytes read
 */
 
 int
 */
 
 int

-tls_read(uschar *buff, size_t len)
+tls_read(BOOL is_server, uschar *buff, size_t len)

 {
 {

-int inbytes;
+exim_gnutls_state_st *state = is_server ? &state_server : &state_client;
+ssize_t inbytes;
+
+if (len > INT_MAX)
+  len = INT_MAX;

 
 

-DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%lx, %lx, %u)\n",
-  (long) tls_session, (long) buff, len);
+if (state->xfer_buffer_lwm < state->xfer_buffer_hwm)
+  DEBUG(D_tls)
+    debug_printf("*** PROBABLY A BUG *** " \
+        "tls_read() called with data in the tls_getc() buffer, %d ignored\n",
+        state->xfer_buffer_hwm - state->xfer_buffer_lwm);
+
+DEBUG(D_tls)
+  debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
+      state->session, buff, len);

 
 

-inbytes = gnutls_record_recv(tls_session, CS buff, len);
+inbytes = gnutls_record_recv(state->session, buff, len);

 if (inbytes > 0) return inbytes;
 if (inbytes == 0)
   {
   DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
   }
 if (inbytes > 0) return inbytes;
 if (inbytes == 0)
   {
   DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
   }

-else record_io_error(inbytes, US"recv", NULL);
+else record_io_error(state, (int)inbytes, US"recv", NULL);

 
 return -1;
 }
 
 
 
 
 return -1;
 }
 
 
 

+

 /*************************************************
 *         Write bytes down TLS channel           *
 *************************************************/
 
 /*
 Arguments:
 /*************************************************
 *         Write bytes down TLS channel           *
 *************************************************/
 
 /*
 Arguments:

+  is_server channel specifier

   buff      buffer of data
   len       number of bytes
 
   buff      buffer of data
   len       number of bytes
 


@@ -1247,27 +1811,28 @@ Returns:    the number of bytes after a successful write,
 */
 
 int
 */
 
 int

-tls_write(const uschar *buff, size_t len)
+tls_write(BOOL is_server, const uschar *buff, size_t len)

 {
 {

-int outbytes;
-int left = len;
+ssize_t outbytes;
+size_t left = len;
+exim_gnutls_state_st *state = is_server ? &state_server : &state_client;

 
 

-DEBUG(D_tls) debug_printf("tls_do_write(%lx, %d)\n", (long) buff, left);
+DEBUG(D_tls) debug_printf("tls_do_write(%p, " SIZE_T_FMT ")\n", buff, left);

 while (left > 0)
   {
 while (left > 0)
   {

-  DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %lx, %d)\n", (long)buff,
-    left);
-  outbytes = gnutls_record_send(tls_session, CS buff, left);
+  DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n",
+      buff, left);
+  outbytes = gnutls_record_send(state->session, buff, left);

 
 

-  DEBUG(D_tls) debug_printf("outbytes=%d\n", outbytes);
+  DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);

   if (outbytes < 0)
     {
   if (outbytes < 0)
     {

-    record_io_error(outbytes, US"send", NULL);
+    record_io_error(state, outbytes, US"send", NULL);

     return -1;
     }
   if (outbytes == 0)
     {
     return -1;
     }
   if (outbytes == 0)
     {

-    record_io_error(0, US"send", US"TLS channel closed on write");
+    record_io_error(state, 0, US"send", US"TLS channel closed on write");

     return -1;
     }
 
     return -1;
     }
 


@@ -1275,39 +1840,137 @@ while (left > 0)
   buff += outbytes;
   }
 
   buff += outbytes;
   }
 

-return len;
+if (len > INT_MAX)
+  {
+  DEBUG(D_tls)
+    debug_printf("Whoops!  Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n",
+        len);
+  len = INT_MAX;
+  }
+
+return (int) len;

 }
 
 
 
 }
 
 
 

+

 /*************************************************
 /*************************************************

-*         Close down a TLS session               *
+*            Random number generation            *

 *************************************************/
 
 *************************************************/
 

-/* This is also called from within a delivery subprocess forked from the
-daemon, to shut down the TLS library, without actually doing a shutdown (which
-would tamper with the TLS session in the parent process).
+/* Pseudo-random number generation.  The result is not expected to be
+cryptographically strong but not so weak that someone will shoot themselves
+in the foot using it as a nonce in input in some email header scheme or
+whatever weirdness they'll twist this into.  The result should handle fork()
+and avoid repeating sequences.  OpenSSL handles that for us.

 
 

-Arguments:   TRUE if gnutls_bye is to be called
-Returns:     nothing
+Arguments:
+  max       range maximum
+Returns     a random number in range [0, max-1]

 */
 
 */
 

-void
-tls_close(BOOL shutdown)
+#ifdef HAVE_GNUTLS_RND
+int
+vaguely_random_number(int max)

 {
 {

-if (tls_active < 0) return;  /* TLS was not active */
-
-if (shutdown)
+unsigned int r;
+int i, needed_len;
+uschar *p;
+uschar smallbuf[sizeof(r)];
+
+if (max <= 1)
+  return 0;
+
+needed_len = sizeof(r);
+/* Don't take 8 times more entropy than needed if int is 8 octets and we were
+ * asked for a number less than 10. */
+for (r = max, i = 0; r; ++i)
+  r >>= 1;
+i = (i + 7) / 8;
+if (i < needed_len)
+  needed_len = i;
+
+i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len);
+if (i < 0)

   {
   {

-  DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS\n");
-  gnutls_bye(tls_session, GNUTLS_SHUT_WR);
+  DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n");
+  return vaguely_random_number_fallback(max);
+  }
+r = 0;
+for (p = smallbuf; needed_len; --needed_len, ++p)
+  {
+  r *= 256;
+  r += *p;

   }
 
   }
 

-gnutls_deinit(tls_session);
-tls_session = NULL;
+/* We don't particularly care about weighted results; if someone wants
+ * smooth distribution and cares enough then they should submit a patch then. */
+return r % max;
+}
+#else /* HAVE_GNUTLS_RND */
+int
+vaguely_random_number(int max)
+{
+  return vaguely_random_number_fallback(max);
+}
+#endif /* HAVE_GNUTLS_RND */
+
+
+
+
+/*************************************************
+*  Let tls_require_ciphers be checked at startup *
+*************************************************/
+
+/* The tls_require_ciphers option, if set, must be something which the
+library can parse.
+
+Returns:     NULL on success, or error message
+*/
+
+uschar *
+tls_validate_require_cipher(void)
+{
+int rc;
+uschar *expciphers = NULL;
+gnutls_priority_t priority_cache;
+const char *errpos;
+
+#define validate_check_rc(Label) do { \
+  if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \
+  return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0)
+#define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0)
+
+if (exim_gnutls_base_init_done)
+  log_write(0, LOG_MAIN|LOG_PANIC,
+      "already initialised GnuTLS, Exim developer bug");
+
+rc = gnutls_global_init();
+validate_check_rc(US"gnutls_global_init()");
+exim_gnutls_base_init_done = TRUE;
+
+if (!(tls_require_ciphers && *tls_require_ciphers))
+  return_deinit(NULL);
+
+if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
+  return_deinit(US"failed to expand tls_require_ciphers");
+
+if (!(expciphers && *expciphers))
+  return_deinit(NULL);
+
+DEBUG(D_tls)
+  debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
+
+rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos);
+validate_check_rc(string_sprintf(
+      "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"",
+      expciphers, errpos - CS expciphers, errpos));
+
+#undef return_deinit
+#undef validate_check_rc

 gnutls_global_deinit();
 
 gnutls_global_deinit();
 

-tls_active = -1;
+return NULL;

 }
 
 
 }
 
 


@@ -1326,8 +1989,10 @@ Returns:     nothing
 void
 tls_version_report(FILE *f)
 {
 void
 tls_version_report(FILE *f)
 {

-fprintf(f, "GnuTLS compile-time version: %s\n", LIBGNUTLS_VERSION);
-fprintf(f, "GnuTLS runtime version: %s\n", gnutls_check_version(NULL));
+fprintf(f, "Library version: GnuTLS: Compile: %s\n"
+           "                         Runtime: %s\n",
+           LIBGNUTLS_VERSION,
+           gnutls_check_version(NULL));

 }
 
 /* End of tls-gnu.c */
 }
 
 /* End of tls-gnu.c */