X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/875512a36119423217802de1f79350e7fce1cd9b..980b106561b5b7ad9dd4c501d05a4f9083ef7417:/src/src/tls-gnu.c

diff --git a/src/src/tls-gnu.c b/src/src/tls-gnu.c
index 8836bb259..de2d70c09 100644
--- a/src/src/tls-gnu.c
+++ b/src/src/tls-gnu.c
@@ -2,7 +2,7 @@
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
-/* Copyright (c) University of Cambridge 1995 - 2015 */
+/* Copyright (c) University of Cambridge 1995 - 2018 */
 /* See the file NOTICE for conditions of use and distribution. */
 
 /* Copyright (c) Phil Pennock 2012 */
@@ -39,6 +39,7 @@ require current GnuTLS, then we'll drop support for the ancient libraries).
 #include <gnutls/x509.h>
 /* man-page is incorrect, gnutls_rnd() is not in gnutls.h: */
 #include <gnutls/crypto.h>
+
 /* needed to disable PKCS11 autoload unless requested */
 #if GNUTLS_VERSION_NUMBER >= 0x020c00
 # include <gnutls/pkcs11.h>
@@ -60,10 +61,34 @@ require current GnuTLS, then we'll drop support for the ancient libraries).
 #if GNUTLS_VERSION_NUMBER >= 0x030014
 # define SUPPORT_SYSDEFAULT_CABUNDLE
 #endif
+#if GNUTLS_VERSION_NUMBER >= 0x030104
+# define GNUTLS_CERT_VFY_STATUS_PRINT
+#endif
+#if GNUTLS_VERSION_NUMBER >= 0x030109
+# define SUPPORT_CORK
+#endif
+#if GNUTLS_VERSION_NUMBER >= 0x030506 && !defined(DISABLE_OCSP)
+# define SUPPORT_SRV_OCSP_STACK
+#endif
+
+#ifdef SUPPORT_DANE
+# if GNUTLS_VERSION_NUMBER >= 0x030000
+#  define DANESSL_USAGE_DANE_TA 2
+#  define DANESSL_USAGE_DANE_EE 3
+# else
+#  error GnuTLS version too early for DANE
+# endif
+# if GNUTLS_VERSION_NUMBER < 0x999999
+#  define GNUTLS_BROKEN_DANE_VALIDATION
+# endif
+#endif
 
 #ifndef DISABLE_OCSP
 # include <gnutls/ocsp.h>
 #endif
+#ifdef SUPPORT_DANE
+# include <gnutls/dane.h>
+#endif
 
 /* GnuTLS 2 vs 3
 
@@ -79,7 +104,7 @@ Changes:
 /* Values for verify_requirement */
 
 enum peer_verify_requirement
-  { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED };
+  { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED, VERIFY_DANE };
 
 /* 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
@@ -100,10 +125,11 @@ typedef struct exim_gnutls_state {
   int			fd_in;
   int			fd_out;
   BOOL			peer_cert_verified;
+  BOOL			peer_dane_verified;
   BOOL			trigger_sni_changes;
   BOOL			have_set_peerdn;
-  const struct host_item *host;
-  gnutls_x509_crt_t 	peercert;
+  const struct host_item *host;		/* NULL if server */
+  gnutls_x509_crt_t	peercert;
   uschar		*peerdn;
   uschar		*ciphersuite;
   uschar		*received_sni;
@@ -120,32 +146,64 @@ typedef struct exim_gnutls_state {
   uschar *exp_tls_verify_certificates;
   uschar *exp_tls_crl;
   uschar *exp_tls_require_ciphers;
-  uschar *exp_tls_ocsp_file;
   const uschar *exp_tls_verify_cert_hostnames;
 #ifndef DISABLE_EVENT
   uschar *event_action;
 #endif
+#ifdef SUPPORT_DANE
+  char * const *	dane_data;
+  const int *		dane_data_len;
+#endif
 
   tls_support *tlsp;	/* set in tls_init() */
 
   uschar *xfer_buffer;
   int xfer_buffer_lwm;
   int xfer_buffer_hwm;
-  int xfer_eof;
-  int xfer_error;
+  BOOL xfer_eof;	/*XXX never gets set! */
+  BOOL 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,
+  .session =		NULL,
+  .x509_cred =		NULL,
+  .priority_cache =	NULL,
+  .verify_requirement =	VERIFY_NONE,
+  .fd_in =		-1,
+  .fd_out =		-1,
+  .peer_cert_verified =	FALSE,
+  .peer_dane_verified =	FALSE,
+  .trigger_sni_changes =FALSE,
+  .have_set_peerdn =	FALSE,
+  .host =		NULL,
+  .peercert =		NULL,
+  .peerdn =		NULL,
+  .ciphersuite =	NULL,
+  .received_sni =	NULL,
+
+  .tls_certificate =	NULL,
+  .tls_privatekey =	NULL,
+  .tls_sni =		NULL,
+  .tls_verify_certificates = NULL,
+  .tls_crl =		NULL,
+  .tls_require_ciphers =NULL,
+
+  .exp_tls_certificate = NULL,
+  .exp_tls_privatekey =	NULL,
+  .exp_tls_verify_certificates = NULL,
+  .exp_tls_crl =	NULL,
+  .exp_tls_require_ciphers = NULL,
+  .exp_tls_verify_cert_hostnames = NULL,
 #ifndef DISABLE_EVENT
-                                            NULL,
+  .event_action =	NULL,
 #endif
-  NULL,
-  NULL, 0, 0, 0, 0,
+  .tlsp =		NULL,
+
+  .xfer_buffer =	NULL,
+  .xfer_buffer_lwm =	0,
+  .xfer_buffer_hwm =	0,
+  .xfer_eof =		FALSE,
+  .xfer_error =		FALSE,
 };
 
 /* Not only do we have our own APIs which don't pass around state, assuming
@@ -159,7 +217,7 @@ second connection.
 XXX But see gnutls_session_get_ptr()
 */
 
-static exim_gnutls_state_st state_server, state_client;
+static exim_gnutls_state_st state_server;
 
 /* 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
@@ -171,7 +229,7 @@ static gnutls_dh_params_t dh_server_params = NULL;
 
 static const int ssl_session_timeout = 200;
 
-static const char * const exim_default_gnutls_priority = "NORMAL";
+static const uschar * const exim_default_gnutls_priority = US"NORMAL";
 
 /* Guard library core initialisation */
 
@@ -189,7 +247,8 @@ static BOOL gnutls_buggy_ocsp = FALSE;
 
 /* 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. */
+callbacks.  Possibly GNuTLS also looks for an environment variable
+"GNUTLS_DEBUG_LEVEL". */
 #ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL
 # define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1
 #endif
@@ -205,9 +264,9 @@ before, for now. */
 # 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, errstr); \
+#define exim_gnutls_err_check(rc, Label) do { \
+  if ((rc) != GNUTLS_E_SUCCESS) \
+    return tls_error((Label), US gnutls_strerror(rc), host, errstr); \
   } while (0)
 
 #define expand_check_tlsvar(Varname, errstr) \
@@ -273,11 +332,11 @@ Returns:    OK/DEFER/FAIL
 */
 
 static int
-tls_error(const uschar *prefix, const char *msg, const host_item *host,
+tls_error(const uschar *prefix, const uschar *msg, const host_item *host,
   uschar ** errstr)
 {
 if (errstr)
-  *errstr = string_sprintf("(%s)%s%s", prefix, msg ? ": " : "", msg ? msg : "");
+  *errstr = string_sprintf("(%s)%s%s", prefix, msg ? ": " : "", msg ? msg : US"");
 return host ? FAIL : DEFER;
 }
 
@@ -302,14 +361,14 @@ Returns:   nothing
 static void
 record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text)
 {
-const char * msg;
+const uschar * msg;
 uschar * errstr;
 
 if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED)
-  msg = CS string_sprintf("%s: %s", US gnutls_strerror(rc),
+  msg = string_sprintf("%s: %s", US gnutls_strerror(rc),
     US gnutls_alert_get_name(gnutls_alert_get(state->session)));
 else
-  msg = gnutls_strerror(rc);
+  msg = US gnutls_strerror(rc);
 
 (void) tls_error(when, msg, state->host, &errstr);
 
@@ -393,7 +452,8 @@ gnutls_datum_t channel;
 #endif
 tls_support * tlsp = state->tlsp;
 
-tlsp->active = state->fd_out;
+tlsp->active.sock = state->fd_out;
+tlsp->active.tls_ctx = state;
 
 cipher = gnutls_cipher_get(state->session);
 /* returns size in "bytes" */
@@ -404,6 +464,9 @@ tlsp->cipher = state->ciphersuite;
 DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite);
 
 tlsp->certificate_verified = state->peer_cert_verified;
+#ifdef SUPPORT_DANE
+tlsp->dane_verified = state->peer_dane_verified;
+#endif
 
 /* 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. */
@@ -474,7 +537,7 @@ host_item *host = NULL; /* dummy for macros */
 DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n");
 
 rc = gnutls_dh_params_init(&dh_server_params);
-exim_gnutls_err_check(US"gnutls_dh_params_init");
+exim_gnutls_err_check(rc, US"gnutls_dh_params_init");
 
 m.data = NULL;
 m.size = 0;
@@ -498,7 +561,7 @@ else if (Ustrcmp(exp_tls_dhparam, "none") == 0)
 else if (exp_tls_dhparam[0] != '/')
   {
   if (!(m.data = US std_dh_prime_named(exp_tls_dhparam)))
-    return tls_error(US"No standard prime named", CS exp_tls_dhparam, NULL, errstr);
+    return tls_error(US"No standard prime named", exp_tls_dhparam, NULL, errstr);
   m.size = Ustrlen(m.data);
   }
 else
@@ -510,7 +573,7 @@ else
 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");
+  exim_gnutls_err_check(rc, US"gnutls_dh_params_import_pkcs3");
   DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n");
   return OK;
   }
@@ -561,7 +624,7 @@ if ((fd = Uopen(filename, O_RDONLY, 0)) >= 0)
     {
     saved_errno = errno;
     (void)close(fd);
-    return tls_error(US"TLS cache stat failed", strerror(saved_errno), NULL, errstr);
+    return tls_error(US"TLS cache stat failed", US strerror(saved_errno), NULL, errstr);
     }
   if (!S_ISREG(statbuf.st_mode))
     {
@@ -573,27 +636,27 @@ if ((fd = Uopen(filename, O_RDONLY, 0)) >= 0)
     saved_errno = errno;
     (void)close(fd);
     return tls_error(US"fdopen(TLS cache stat fd) failed",
-        strerror(saved_errno), NULL, errstr);
+        US strerror(saved_errno), NULL, errstr);
     }
 
   m.size = statbuf.st_size;
   if (!(m.data = malloc(m.size)))
     {
     fclose(fp);
-    return tls_error(US"malloc failed", strerror(errno), NULL, errstr);
+    return tls_error(US"malloc failed", US strerror(errno), NULL, errstr);
     }
   if (!(sz = fread(m.data, m.size, 1, fp)))
     {
     saved_errno = errno;
     fclose(fp);
     free(m.data);
-    return tls_error(US"fread failed", strerror(saved_errno), NULL, errstr);
+    return tls_error(US"fread failed", US strerror(saved_errno), NULL, errstr);
     }
   fclose(fp);
 
   rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
   free(m.data);
-  exim_gnutls_err_check(US"gnutls_dh_params_import_pkcs3");
+  exim_gnutls_err_check(rc, US"gnutls_dh_params_import_pkcs3");
   DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename);
   }
 
@@ -623,11 +686,11 @@ if (rc < 0)
 
   if ((PATH_MAX - Ustrlen(filename)) < 10)
     return tls_error(US"Filename too long to generate replacement",
-        CS filename, NULL, errstr);
+        filename, NULL, errstr);
 
-  temp_fn = string_copy(US "%s.XXXXXXX");
+  temp_fn = string_copy(US"%s.XXXXXXX");
   if ((fd = mkstemp(CS temp_fn)) < 0)	/* modifies temp_fn */
-    return tls_error(US"Unable to open temp file", strerror(errno), NULL, errstr);
+    return tls_error(US"Unable to open temp file", US strerror(errno), NULL, errstr);
   (void)fchown(fd, exim_uid, exim_gid);   /* Probably not necessary */
 
   /* GnuTLS overshoots!
@@ -650,7 +713,7 @@ if (rc < 0)
     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");
+  exim_gnutls_err_check(rc, 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
@@ -661,10 +724,10 @@ if (rc < 0)
   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");
+    exim_gnutls_err_check(rc, US"gnutls_dh_params_export_pkcs3(NULL) sizing");
   m.size = sz;
   if (!(m.data = malloc(m.size)))
-    return tls_error(US"memory allocation failed", strerror(errno), NULL, errstr);
+    return tls_error(US"memory allocation failed", US strerror(errno), NULL, errstr);
 
   /* 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,
@@ -672,7 +735,7 @@ if (rc < 0)
   if (rc != GNUTLS_E_SUCCESS)
     {
     free(m.data);
-    exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3() real");
+    exim_gnutls_err_check(rc, US"gnutls_dh_params_export_pkcs3() real");
     }
   m.size = sz; /* shrink by 1, probably */
 
@@ -680,19 +743,19 @@ if (rc < 0)
     {
     free(m.data);
     return tls_error(US"TLS cache write D-H params failed",
-        strerror(errno), NULL, errstr);
+        US strerror(errno), NULL, errstr);
     }
   free(m.data);
   if ((sz = write_to_fd_buf(fd, US"\n", 1)) != 1)
     return tls_error(US"TLS cache write D-H params final newline failed",
-        strerror(errno), NULL, errstr);
+        US strerror(errno), NULL, errstr);
 
   if ((rc = close(fd)))
-    return tls_error(US"TLS cache write close() failed", strerror(errno), NULL, errstr);
+    return tls_error(US"TLS cache write close() failed", US strerror(errno), NULL, errstr);
 
   if (Urename(temp_fn, filename) < 0)
     return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"",
-          temp_fn, filename), strerror(errno), NULL, errstr);
+          temp_fn, filename), US strerror(errno), NULL, errstr);
 
   DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);
   }
@@ -724,15 +787,18 @@ if ((rc = gnutls_x509_crt_init(&cert))) goto err;
 where = US"generating pkey";
 if ((rc = gnutls_x509_privkey_generate(pkey, GNUTLS_PK_RSA,
 #ifdef SUPPORT_PARAM_TO_PK_BITS
-	    gnutls_sec_param_to_pk_bits(GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_LOW),
+# ifndef GNUTLS_SEC_PARAM_MEDIUM
+#  define GNUTLS_SEC_PARAM_MEDIUM GNUTLS_SEC_PARAM_HIGH
+# endif
+	    gnutls_sec_param_to_pk_bits(GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_MEDIUM),
 #else
-	    1024,
+	    2048,
 #endif
 	    0)))
   goto err;
 
 where = US"configuring cert";
-now = 0;
+now = 1;
 if (  (rc = gnutls_x509_crt_set_version(cert, 3))
    || (rc = gnutls_x509_crt_set_serial(cert, &now, sizeof(now)))
    || (rc = gnutls_x509_crt_set_activation_time(cert, now = time(NULL)))
@@ -765,13 +831,34 @@ out:
   return rc;
 
 err:
-  rc = tls_error(where, gnutls_strerror(rc), NULL, errstr);
+  rc = tls_error(where, US gnutls_strerror(rc), NULL, errstr);
   goto out;
 }
 
 
 
 
+/* Add certificate and key, from files.
+
+Return:
+  Zero or negative: good.  Negate value for certificate index if < 0.
+  Greater than zero: FAIL or DEFER code.
+*/
+
+static int
+tls_add_certfile(exim_gnutls_state_st * state, const host_item * host,
+  uschar * certfile, uschar * keyfile, uschar ** errstr)
+{
+int rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
+    CS certfile, CS keyfile, GNUTLS_X509_FMT_PEM);
+if (rc < 0)
+  return tls_error(
+    string_sprintf("cert/key setup: cert=%s key=%s", certfile, keyfile),
+    US gnutls_strerror(rc), host, errstr);
+return -rc;
+}
+
+
 /*************************************************
 *       Variables re-expanded post-SNI           *
 *************************************************/
@@ -792,7 +879,7 @@ Returns:          OK/DEFER/FAIL
 */
 
 static int
-tls_expand_session_files(exim_gnutls_state_st *state, uschar ** errstr)
+tls_expand_session_files(exim_gnutls_state_st * state, uschar ** errstr)
 {
 struct stat statbuf;
 int rc;
@@ -807,11 +894,11 @@ int cert_count;
 if (!host)	/* server */
   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")
-       ))
+    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;
@@ -827,7 +914,11 @@ if (!host)	/* server */
     }
 
 rc = gnutls_certificate_allocate_credentials(&state->x509_cred);
-exim_gnutls_err_check(US"gnutls_certificate_allocate_credentials");
+exim_gnutls_err_check(rc, US"gnutls_certificate_allocate_credentials");
+
+#ifdef SUPPORT_SRV_OCSP_STACK
+gnutls_certificate_set_flags(state->x509_cred, GNUTLS_CERTIFICATE_API_V2);
+#endif
 
 /* remember: expand_check_tlsvar() is expand_check() but fiddling with
 state members, assuming consistent naming; and expand_check() returns
@@ -878,44 +969,81 @@ if (state->exp_tls_certificate && *state->exp_tls_certificate)
       DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\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 */
+  if (!host)	/* server */
+    {
+    const uschar * clist = state->exp_tls_certificate;
+    const uschar * klist = state->exp_tls_privatekey;
+    const uschar * olist;
+    int csep = 0, ksep = 0, osep = 0, cnt = 0;
+    uschar * cfile, * kfile, * ofile;
 
+#ifndef DISABLE_OCSP
+    if (!expand_check(tls_ocsp_file, US"tls_ocsp_file", &ofile, errstr))
+      return DEFER;
+    olist = ofile;
+#endif
 
-/* Set the OCSP stapling server info */
+    while (cfile = string_nextinlist(&clist, &csep, NULL, 0))
+
+      if (!(kfile = string_nextinlist(&klist, &ksep, NULL, 0)))
+	return tls_error(US"cert/key setup: out of keys", NULL, host, errstr);
+      else if (0 < (rc = tls_add_certfile(state, host, cfile, kfile, errstr)))
+	return rc;
+      else
+	{
+	int gnutls_cert_index = -rc;
+	DEBUG(D_tls) debug_printf("TLS: cert/key %s registered\n", cfile);
+
+	/* Set the OCSP stapling server info */
 
 #ifndef DISABLE_OCSP
-if (  !host	/* server */
-   && tls_ocsp_file
-   )
-  {
-  if (gnutls_buggy_ocsp)
-    {
-    DEBUG(D_tls) debug_printf("GnuTLS library is buggy for OCSP; avoiding\n");
+	if (tls_ocsp_file)
+	  if (gnutls_buggy_ocsp)
+	    {
+	    DEBUG(D_tls)
+	      debug_printf("GnuTLS library is buggy for OCSP; avoiding\n");
+	    }
+	  else if ((ofile = string_nextinlist(&olist, &osep, NULL, 0)))
+	    {
+	    /* Use the full callback method for stapling just to get
+	    observability.  More efficient would be to read the file once only,
+	    if it never changed (due to SNI). Would need restart on file update,
+	    or watch datestamp.  */
+
+# ifdef SUPPORT_SRV_OCSP_STACK
+	    rc = gnutls_certificate_set_ocsp_status_request_function2(
+	      state->x509_cred, gnutls_cert_index,
+	      server_ocsp_stapling_cb, ofile);
+
+	    exim_gnutls_err_check(rc,
+	      US"gnutls_certificate_set_ocsp_status_request_function2");
+# else
+	    if (cnt++ > 0)
+	      {
+	      DEBUG(D_tls)
+		debug_printf("oops; multiple OCSP files not supported\n");
+	      break;
+	      }
+	      gnutls_certificate_set_ocsp_status_request_function(
+		state->x509_cred, server_ocsp_stapling_cb, ofile);
+# endif
+
+	    DEBUG(D_tls) debug_printf("OCSP response file = %s\n", ofile);
+	    }
+	  else
+	    DEBUG(D_tls) debug_printf("ran out of OCSP response files in list\n");
+#endif
+	}
     }
   else
     {
-    if (!expand_check(tls_ocsp_file, US"tls_ocsp_file",
-	  &state->exp_tls_ocsp_file, errstr))
-      return DEFER;
-
-    /* Use the full callback method for stapling just to get observability.
-    More efficient would be to read the file once only, if it never changed
-    (due to SNI). Would need restart on file update, or watch datestamp.  */
-
-    gnutls_certificate_set_ocsp_status_request_function(state->x509_cred,
-      server_ocsp_stapling_cb, state->exp_tls_ocsp_file);
-
-    DEBUG(D_tls) debug_printf("OCSP response file = %s\n", state->exp_tls_ocsp_file);
+    if (0 < (rc = tls_add_certfile(state, host,
+		state->exp_tls_certificate, state->exp_tls_privatekey, errstr)))
+      return rc;
+    DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
     }
-  }
-#endif
+
+  } /* tls_certificate */
 
 
 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
@@ -1010,7 +1138,7 @@ else
 if (cert_count < 0)
   {
   rc = cert_count;
-  exim_gnutls_err_check(US"setting certificate trust");
+  exim_gnutls_err_check(rc, US"setting certificate trust");
   }
 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count);
 
@@ -1023,7 +1151,7 @@ if (state->tls_crl && *state->tls_crl &&
   if (cert_count < 0)
     {
     rc = cert_count;
-    exim_gnutls_err_check(US"gnutls_certificate_set_x509_crl_file");
+    exim_gnutls_err_check(rc, US"gnutls_certificate_set_x509_crl_file");
     }
   DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
   }
@@ -1074,7 +1202,7 @@ if (!state->host)
 /* 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");
+exim_gnutls_err_check(rc, US"gnutls_credentials_set");
 
 return OK;
 }
@@ -1142,6 +1270,7 @@ tls_init(
     const uschar *crl,
     const uschar *require_ciphers,
     exim_gnutls_state_st **caller_state,
+    tls_support * tlsp,
     uschar ** errstr)
 {
 exim_gnutls_state_st *state;
@@ -1149,7 +1278,6 @@ int rc;
 size_t sz;
 const char *errpos;
 uschar *p;
-BOOL want_default_priorities;
 
 if (!exim_gnutls_base_init_done)
   {
@@ -1164,18 +1292,18 @@ if (!exim_gnutls_base_init_done)
   if (!gnutls_allow_auto_pkcs11)
     {
     rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL);
-    exim_gnutls_err_check(US"gnutls_pkcs11_init");
+    exim_gnutls_err_check(rc, US"gnutls_pkcs11_init");
     }
 #endif
 
   rc = gnutls_global_init();
-  exim_gnutls_err_check(US"gnutls_global_init");
+  exim_gnutls_err_check(rc, 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 */
+    /* arbitrarily chosen level; bump up to 9 for more */
     gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
     }
 #endif
@@ -1190,9 +1318,15 @@ if (!exim_gnutls_base_init_done)
 
 if (host)
   {
-  state = &state_client;
+  /* For client-side sessions we allocate a context. This lets us run
+  several in parallel. */
+  int old_pool = store_pool;
+  store_pool = POOL_PERM;
+  state = store_get(sizeof(exim_gnutls_state_st));
+  store_pool = old_pool;
+
   memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
-  state->tlsp = &tls_out;
+  state->tlsp = tlsp;
   DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
   rc = gnutls_init(&state->session, GNUTLS_CLIENT);
   }
@@ -1200,11 +1334,11 @@ else
   {
   state = &state_server;
   memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
-  state->tlsp = &tls_in;
+  state->tlsp = tlsp;
   DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
   rc = gnutls_init(&state->session, GNUTLS_SERVER);
   }
-exim_gnutls_err_check(US"gnutls_init");
+exim_gnutls_err_check(rc, US"gnutls_init");
 
 state->host = host;
 
@@ -1239,12 +1373,12 @@ if (host)
     sz = Ustrlen(state->tlsp->sni);
     rc = gnutls_server_name_set(state->session,
         GNUTLS_NAME_DNS, state->tlsp->sni, sz);
-    exim_gnutls_err_check(US"gnutls_server_name_set");
+    exim_gnutls_err_check(rc, 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);
+      "have an SNI set for a server [%s]\n", state->tls_sni);
 
 /* This is the priority string support,
 http://www.gnutls.org/manual/html_node/Priority-Strings.html
@@ -1252,39 +1386,31 @@ 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;
-
+p = NULL;
 if (state->tls_require_ciphers && *state->tls_require_ciphers)
   {
   if (!expand_check_tlsvar(tls_require_ciphers, errstr))
     return DEFER;
   if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
     {
-    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;
+    DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n", p);
     }
   }
-if (want_default_priorities)
+if (!p)
   {
+  p = exim_default_gnutls_priority;
   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_printf("GnuTLS using default session cipher/priority \"%s\"\n", p);
   }
+rc = gnutls_priority_init(&state->priority_cache, CCS p, &errpos);
 
-exim_gnutls_err_check(string_sprintf(
+exim_gnutls_err_check(rc, 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");
+exim_gnutls_err_check(rc, US"gnutls_priority_set");
 
 gnutls_db_set_cache_expiration(state->session, ssl_session_timeout);
 
@@ -1390,14 +1516,14 @@ if (cert_list == NULL || cert_list_size == 0)
       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, errstr);
+        US"no certificate received from peer", state->host, errstr);
   return OK;
   }
 
 ct = gnutls_certificate_type_get(state->session);
 if (ct != GNUTLS_CRT_X509)
   {
-  const char *ctn = gnutls_certificate_type_get_name(ct);
+  const uschar *ctn = US 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)
@@ -1413,7 +1539,7 @@ if (ct != GNUTLS_CRT_X509)
       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, errstr); \
+	return tls_error((Label), US gnutls_strerror(rc), state->host, errstr); \
       return OK; \
       } \
     } while (0)
@@ -1453,8 +1579,8 @@ gnutls_certificate_set_verify_function() to fail the handshake if we dislike
 the peer information, but that's too new for some OSes.
 
 Arguments:
-  state           exim_gnutls_state_st *
-  errstr          where to put an error message
+  state		exim_gnutls_state_st *
+  errstr	where to put an error message
 
 Returns:
   FALSE     if the session should be rejected
@@ -1462,11 +1588,15 @@ Returns:
 */
 
 static BOOL
-verify_certificate(exim_gnutls_state_st *state, uschar ** errstr)
+verify_certificate(exim_gnutls_state_st * state, uschar ** errstr)
 {
 int rc;
-unsigned int verify;
+uint verify;
+
+if (state->verify_requirement == VERIFY_NONE)
+  return TRUE;
 
+DEBUG(D_tls) debug_printf("TLS: checking peer certificate\n");
 *errstr = NULL;
 
 if ((rc = peer_status(state, errstr)) != OK)
@@ -1475,65 +1605,208 @@ if ((rc = peer_status(state, errstr)) != OK)
   *errstr = US"certificate not supplied";
   }
 else
+
+  {
+#ifdef SUPPORT_DANE
+  if (state->verify_requirement == VERIFY_DANE && state->host)
+    {
+    /* Using dane_verify_session_crt() would be easy, as it does it all for us
+    including talking to a DNS resolver.  But we want to do that bit ourselves
+    as the testsuite intercepts and fakes its own DNS environment. */
+
+    dane_state_t s;
+    dane_query_t r;
+    uint lsize;
+    const gnutls_datum_t * certlist =
+      gnutls_certificate_get_peers(state->session, &lsize);
+    int usage = tls_out.tlsa_usage;
+
+# ifdef GNUTLS_BROKEN_DANE_VALIDATION
+    /* Split the TLSA records into two sets, TA and EE selectors.  Run the
+    dane-verification separately so that we know which selector verified;
+    then we know whether to do name-verification (needed for TA but not EE). */
+
+    if (usage == ((1<<DANESSL_USAGE_DANE_TA) | (1<<DANESSL_USAGE_DANE_EE)))
+      {						/* a mixed-usage bundle */
+      int i, j, nrec;
+      const char ** dd;
+      int * ddl;
+
+      for(nrec = 0; state->dane_data_len[nrec]; ) nrec++;
+      nrec++;
+
+      dd = store_get(nrec * sizeof(uschar *));
+      ddl = store_get(nrec * sizeof(int));
+      nrec--;
+
+      if ((rc = dane_state_init(&s, 0)))
+	goto tlsa_prob;
+
+      for (usage = DANESSL_USAGE_DANE_EE;
+	   usage >= DANESSL_USAGE_DANE_TA; usage--)
+	{				/* take records with this usage */
+	for (j = i = 0; i < nrec; i++)
+	  if (state->dane_data[i][0] == usage)
+	    {
+	    dd[j] = state->dane_data[i];
+	    ddl[j++] = state->dane_data_len[i];
+	    }
+	if (j)
+	  {
+	  dd[j] = NULL;
+	  ddl[j] = 0;
+
+	  if ((rc = dane_raw_tlsa(s, &r, (char * const *)dd, ddl, 1, 0)))
+	    goto tlsa_prob;
+
+	  if ((rc = dane_verify_crt_raw(s, certlist, lsize,
+			    gnutls_certificate_type_get(state->session),
+			    r, 0,
+			    usage == DANESSL_USAGE_DANE_EE
+			    ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
+			    &verify)))
+	    {
+	    DEBUG(D_tls)
+	      debug_printf("TLSA record problem: %s\n", dane_strerror(rc));
+	    }
+	  else if (verify == 0)	/* verification passed */
+	    {
+	    usage = 1 << usage;
+	    break;
+	    }
+	  }
+	}
+
+	if (rc) goto tlsa_prob;
+      }
+    else
+# endif
+      {
+      if (  (rc = dane_state_init(&s, 0))
+	 || (rc = dane_raw_tlsa(s, &r, state->dane_data, state->dane_data_len,
+			1, 0))
+	 || (rc = dane_verify_crt_raw(s, certlist, lsize,
+			gnutls_certificate_type_get(state->session),
+			r, 0,
+# ifdef GNUTLS_BROKEN_DANE_VALIDATION
+			usage == (1 << DANESSL_USAGE_DANE_EE)
+			? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
+# else
+			0,
+# endif
+			&verify))
+	 )
+	goto tlsa_prob;
+      }
+
+    if (verify != 0)		/* verification failed */
+      {
+      gnutls_datum_t str;
+      (void) dane_verification_status_print(verify, &str, 0);
+      *errstr = US str.data;	/* don't bother to free */
+      goto badcert;
+      }
+
+# ifdef GNUTLS_BROKEN_DANE_VALIDATION
+    /* If a TA-mode TLSA record was used for verification we must additionally
+    verify the cert name (but not the CA chain).  For EE-mode, skip it. */
+
+    if (usage & (1 << DANESSL_USAGE_DANE_EE))
+# endif
+      {
+      state->peer_dane_verified = state->peer_cert_verified = TRUE;
+      goto goodcert;
+      }
+# ifdef GNUTLS_BROKEN_DANE_VALIDATION
+    /* Assume that the name on the A-record is the one that should be matching
+    the cert.  An alternate view is that the domain part of the email address
+    is also permissible. */
+
+    if (gnutls_x509_crt_check_hostname(state->tlsp->peercert,
+	  CS state->host->name))
+      {
+      state->peer_dane_verified = state->peer_cert_verified = TRUE;
+      goto goodcert;
+      }
+# endif
+    }
+#endif	/*SUPPORT_DANE*/
+
   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. */
+/* Handle the result of verification. INVALID is set if any others are. */
 
-if (rc < 0 ||
-    verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED)
-   )
+if (rc < 0 || verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED))
   {
   state->peer_cert_verified = FALSE;
   if (!*errstr)
+    {
+#ifdef GNUTLS_CERT_VFY_STATUS_PRINT
+    DEBUG(D_tls)
+      {
+      gnutls_datum_t txt;
+
+      if (gnutls_certificate_verification_status_print(verify,
+	    gnutls_certificate_type_get(state->session), &txt, 0)
+	  == GNUTLS_E_SUCCESS)
+	{
+	debug_printf("%s\n", txt.data);
+	gnutls_free(txt.data);
+	}
+      }
+#endif
     *errstr = verify & GNUTLS_CERT_REVOKED
       ? US"certificate revoked" : US"certificate invalid";
+    }
 
   DEBUG(D_tls)
     debug_printf("TLS certificate verification failed (%s): peerdn=\"%s\"\n",
         *errstr, 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;
-    }
+    goto badcert;
   DEBUG(D_tls)
     debug_printf("TLS verify failure overridden (host in tls_try_verify_hosts)\n");
   }
 
 else
   {
-  if (state->exp_tls_verify_cert_hostnames)
+  /* Client side, check the server's certificate name versus the name on the
+  A-record for the connection we made.  What to do for server side - what name
+  to use for client?  We document that there is no such checking for server
+  side. */
+
+  if (  state->exp_tls_verify_cert_hostnames
+     && !gnutls_x509_crt_check_hostname(state->tlsp->peercert,
+		CS state->exp_tls_verify_cert_hostnames)
+     )
     {
-    int sep = 0;
-    const uschar * list = state->exp_tls_verify_cert_hostnames;
-    uschar * name;
-    while ((name = string_nextinlist(&list, &sep, NULL, 0)))
-      if (gnutls_x509_crt_check_hostname(state->tlsp->peercert, CS name))
-	break;
-    if (!name)
-      {
-      DEBUG(D_tls)
-	debug_printf("TLS certificate verification failed: cert name mismatch\n");
-      if (state->verify_requirement >= VERIFY_REQUIRED)
-	{
-	gnutls_alert_send(state->session,
-	  GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
-	return FALSE;
-	}
-      return TRUE;
-      }
+    DEBUG(D_tls)
+      debug_printf("TLS certificate verification failed: cert name mismatch\n");
+    if (state->verify_requirement >= VERIFY_REQUIRED)
+      goto badcert;
+    return TRUE;
     }
+
   state->peer_cert_verified = TRUE;
   DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=\"%s\"\n",
       state->peerdn ? state->peerdn : US"<unset>");
   }
 
-state->tlsp->peerdn = state->peerdn;
+goodcert:
+  state->tlsp->peerdn = state->peerdn;
+  return TRUE;
 
-return TRUE;
+#ifdef SUPPORT_DANE
+tlsa_prob:
+  *errstr = string_sprintf("TLSA record problem: %s",
+    rc == DANE_E_REQUESTED_DATA_NOT_AVAILABLE ? "none usable" : dane_strerror(rc));
+#endif
+
+badcert:
+  gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
+  return FALSE;
 }
 
 
@@ -1644,11 +1917,12 @@ server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
   gnutls_datum_t * ocsp_response)
 {
 int ret;
+DEBUG(D_tls) debug_printf("OCSP stapling callback: %s\n", US ptr);
 
 if ((ret = gnutls_load_file(ptr, ocsp_response)) < 0)
   {
   DEBUG(D_tls) debug_printf("Failed to load ocsp stapling file %s\n",
-			      (char *)ptr);
+			      CS ptr);
   tls_in.ocsp = OCSP_NOT_RESP;
   return GNUTLS_E_NO_CERTIFICATE_STATUS;
   }
@@ -1680,12 +1954,10 @@ int rc;
 uschar * yield;
 exim_gnutls_state_st * state = gnutls_session_get_ptr(session);
 
-cert_list = gnutls_certificate_get_peers(session, &cert_list_size);
-if (cert_list)
+if ((cert_list = gnutls_certificate_get_peers(session, &cert_list_size)))
   while (cert_list_size--)
   {
-  rc = import_cert(&cert_list[cert_list_size], &crt);
-  if (rc != GNUTLS_E_SUCCESS)
+  if ((rc = import_cert(&cert_list[cert_list_size], &crt)) != GNUTLS_E_SUCCESS)
     {
     DEBUG(D_tls) debug_printf("TLS: peer cert problem: depth %d: %s\n",
       cert_list_size, gnutls_strerror(rc));
@@ -1742,10 +2014,10 @@ int rc;
 exim_gnutls_state_st * state = NULL;
 
 /* Check for previous activation */
-if (tls_in.active >= 0)
+if (tls_in.active.sock >= 0)
   {
-  tls_error(US"STARTTLS received after TLS started", "", NULL, errstr);
-  smtp_printf("554 Already in TLS\r\n");
+  tls_error(US"STARTTLS received after TLS started", US "", NULL, errstr);
+  smtp_printf("554 Already in TLS\r\n", FALSE);
   return FAIL;
   }
 
@@ -1756,7 +2028,7 @@ DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n");
 
 if ((rc = tls_init(NULL, tls_certificate, tls_privatekey,
     NULL, tls_verify_certificates, tls_crl,
-    require_ciphers, &state, errstr)) != OK) return rc;
+    require_ciphers, &state, &tls_in, errstr)) != OK) return rc;
 
 /* If this is a host for which certificate verification is mandatory or
 optional, set up appropriately. */
@@ -1806,12 +2078,15 @@ mode, the fflush() happens when smtp_getc() is called. */
 
 if (!state->tlsp->on_connect)
   {
-  smtp_printf("220 TLS go ahead\r\n");
+  smtp_printf("220 TLS go ahead\r\n", FALSE);
   fflush(smtp_out);
   }
 
 /* Now negotiate the TLS session. We put our own timer on it, since it seems
-that the GnuTLS library doesn't. */
+that the GnuTLS library doesn't.
+From 3.1.0 there is gnutls_handshake_set_timeout() - but it requires you
+to set (and clear down afterwards) up a pull-timeout callback function that does
+a select, so we're no better off unless avoiding signals becomes an issue. */
 
 gnutls_transport_set_ptr2(state->session,
     (gnutls_transport_ptr_t)(long) fileno(smtp_in),
@@ -1820,11 +2095,11 @@ state->fd_in = fileno(smtp_in);
 state->fd_out = fileno(smtp_out);
 
 sigalrm_seen = FALSE;
-if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
+if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
 do
   rc = gnutls_handshake(state->session);
 while (rc == GNUTLS_E_AGAIN ||  rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
-alarm(0);
+ALARM_CLR(0);
 
 if (rc != GNUTLS_E_SUCCESS)
   {
@@ -1834,12 +2109,12 @@ if (rc != GNUTLS_E_SUCCESS)
 
   if (sigalrm_seen)
     {
-    tls_error(US"gnutls_handshake", "timed out", NULL, errstr);
+    tls_error(US"gnutls_handshake", US"timed out", NULL, errstr);
     gnutls_db_remove_session(state->session);
     }
   else
     {
-    tls_error(US"gnutls_handshake", gnutls_strerror(rc), NULL, errstr);
+    tls_error(US"gnutls_handshake", US gnutls_strerror(rc), NULL, errstr);
     (void) gnutls_alert_send_appropriate(state->session, rc);
     gnutls_deinit(state->session);
     gnutls_certificate_free_credentials(state->x509_cred);
@@ -1858,8 +2133,7 @@ DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
 
 /* Verify after the fact */
 
-if (  state->verify_requirement != VERIFY_NONE
-   && !verify_certificate(state, errstr))
+if (!verify_certificate(state, errstr))
   {
   if (state->verify_requirement != VERIFY_OPTIONAL)
     {
@@ -1885,6 +2159,7 @@ and initialize appropriately. */
 state->xfer_buffer = store_malloc(ssl_xfer_buffer_size);
 
 receive_getc = tls_getc;
+receive_getbuf = tls_getbuf;
 receive_get_cache = tls_get_cache;
 receive_ungetc = tls_ungetc;
 receive_feof = tls_feof;
@@ -1901,7 +2176,7 @@ static void
 tls_client_setup_hostname_checks(host_item * host, exim_gnutls_state_st * state,
   smtp_transport_options_block * ob)
 {
-if (verify_check_given_host(&ob->tls_verify_cert_hostnames, host) == OK)
+if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
   {
   state->exp_tls_verify_cert_hostnames =
 #ifdef SUPPORT_I18N
@@ -1916,6 +2191,77 @@ if (verify_check_given_host(&ob->tls_verify_cert_hostnames, host) == OK)
 }
 
 
+
+
+#ifdef SUPPORT_DANE
+/* Given our list of RRs from the TLSA lookup, build a lookup block in
+GnuTLS-DANE's preferred format.  Hang it on the state str for later
+use in DANE verification.
+
+We point at the dnsa data not copy it, so it must remain valid until
+after verification is done.*/
+
+static BOOL
+dane_tlsa_load(exim_gnutls_state_st * state, dns_answer * dnsa)
+{
+dns_record * rr;
+dns_scan dnss;
+int i;
+const char **	dane_data;
+int *		dane_data_len;
+
+for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS), i = 1;
+     rr;
+     rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
+    ) if (rr->type == T_TLSA) i++;
+
+dane_data = store_get(i * sizeof(uschar *));
+dane_data_len = store_get(i * sizeof(int));
+
+for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS), i = 0;
+     rr;
+     rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
+    ) if (rr->type == T_TLSA && rr->size > 3)
+  {
+  const uschar * p = rr->data;
+  uint8_t usage = p[0], sel = p[1], type = p[2];
+
+  DEBUG(D_tls)
+    debug_printf("TLSA: %d %d %d size %d\n", usage, sel, type, rr->size);
+
+  if (  (usage != DANESSL_USAGE_DANE_TA && usage != DANESSL_USAGE_DANE_EE)
+     || (sel != 0 && sel != 1)
+     )
+    continue;
+  switch(type)
+    {
+    case 0:	/* Full: cannot check at present */
+		break;
+    case 1:	if (rr->size != 3 + 256/8) continue;	/* sha2-256 */
+		break;
+    case 2:	if (rr->size != 3 + 512/8) continue;	/* sha2-512 */
+		break;
+    default:	continue;
+    }
+
+  tls_out.tlsa_usage |= 1<<usage;
+  dane_data[i] = CS p;
+  dane_data_len[i++] = rr->size;
+  }
+
+if (!i) return FALSE;
+
+dane_data[i] = NULL;
+dane_data_len[i] = 0;
+
+state->dane_data = (char * const *)dane_data;
+state->dane_data_len = dane_data_len;
+return TRUE;
+}
+#endif
+
+
+
 /*************************************************
 *    Start a TLS session in a client             *
 *************************************************/
@@ -1924,42 +2270,64 @@ if (verify_check_given_host(&ob->tls_verify_cert_hostnames, host) == OK)
 
 Arguments:
   fd                the fd of the connection
-  host              connected host (for messages)
+  host              connected host (for messages and option-tests)
   addr              the first address (not used)
   tb                transport (always smtp)
-
+  tlsa_dnsa	    non-NULL, either request or require dane for this host, and
+		    a TLSA record found.  Therefore, dane verify required.
+		    Which implies cert must be requested and supplied, dane
+		    verify must pass, and cert verify irrelevant (incl.
+		    hostnames), and (caller handled) require_tls
+  tlsp		    record details of channel configuration
   errstr	    error string pointer
 
-Returns:            OK/DEFER/FAIL (because using common functions),
-                    but for a client, DEFER and FAIL have the same meaning
+Returns:            Pointer to TLS session context, or NULL on error
 */
 
-int
+void *
 tls_client_start(int fd, host_item *host,
     address_item *addr ARG_UNUSED,
     transport_instance * tb,
-#ifdef EXPERIMENTAL_DANE
-    dns_answer * tlsa_dnsa ARG_UNUSED,
+#ifdef SUPPORT_DANE
+    dns_answer * tlsa_dnsa,
 #endif
-    uschar ** errstr)
+    tls_support * tlsp, uschar ** errstr)
 {
-smtp_transport_options_block *ob =
-  (smtp_transport_options_block *)tb->options_block;
+smtp_transport_options_block *ob = tb
+  ? (smtp_transport_options_block *)tb->options_block
+  : &smtp_transport_option_defaults;
 int rc;
-exim_gnutls_state_st *state = NULL;
+exim_gnutls_state_st * state = NULL;
+uschar *cipher_list = NULL;
+
 #ifndef DISABLE_OCSP
 BOOL require_ocsp =
-  verify_check_given_host(&ob->hosts_require_ocsp, host) == OK;
+  verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
 BOOL request_ocsp = require_ocsp ? TRUE
-  : verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
+  : verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
 #endif
 
 DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd);
 
-if ((rc = tls_init(host, ob->tls_certificate, ob->tls_privatekey,
+#ifdef SUPPORT_DANE
+if (tlsa_dnsa && ob->dane_require_tls_ciphers)
+  {
+  /* not using expand_check_tlsvar because not yet in state */
+  if (!expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
+      &cipher_list, errstr))
+    return NULL;
+  cipher_list = cipher_list && *cipher_list
+    ? ob->dane_require_tls_ciphers : ob->tls_require_ciphers;
+  }
+#endif
+
+if (!cipher_list)
+  cipher_list = ob->tls_require_ciphers;
+
+if (tls_init(host, ob->tls_certificate, ob->tls_privatekey,
     ob->tls_sni, ob->tls_verify_certificates, ob->tls_crl,
-    ob->tls_require_ciphers, &state, errstr)) != OK)
-  return rc;
+    cipher_list, &state, tlsp, errstr) != OK)
+  return NULL;
 
   {
   int dh_min_bits = ob->tls_dh_min_bits;
@@ -1982,12 +2350,22 @@ if ((rc = tls_init(host, ob->tls_certificate, ob->tls_privatekey,
 set but both tls_verify_hosts and tls_try_verify_hosts are unset. Check only
 the specified host patterns if one of them is defined */
 
-if (  (  state->exp_tls_verify_certificates
-      && !ob->tls_verify_hosts
-      && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
-      )
-    || verify_check_given_host(&ob->tls_verify_hosts, host) == OK
-   )
+#ifdef SUPPORT_DANE
+if (tlsa_dnsa && dane_tlsa_load(state, tlsa_dnsa))
+  {
+  DEBUG(D_tls)
+    debug_printf("TLS: server certificate DANE required.\n");
+  state->verify_requirement = VERIFY_DANE;
+  gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
+  }
+else
+#endif
+    if (  (  state->exp_tls_verify_certificates
+	  && !ob->tls_verify_hosts
+	  && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
+	  )
+	|| verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
+       )
   {
   tls_client_setup_hostname_checks(host, state, ob);
   DEBUG(D_tls)
@@ -1995,7 +2373,7 @@ if (  (  state->exp_tls_verify_certificates
   state->verify_requirement = VERIFY_REQUIRED;
   gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
   }
-else if (verify_check_given_host(&ob->tls_try_verify_hosts, host) == OK)
+else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
   {
   tls_client_setup_hostname_checks(host, state, ob);
   DEBUG(D_tls)
@@ -2018,14 +2396,16 @@ if (request_ocsp)
   DEBUG(D_tls) debug_printf("TLS: will request OCSP stapling\n");
   if ((rc = gnutls_ocsp_status_request_enable_client(state->session,
 		    NULL, 0, NULL)) != OK)
-    return tls_error(US"cert-status-req",
-		    gnutls_strerror(rc), state->host, errstr);
-  tls_out.ocsp = OCSP_NOT_RESP;
+    {
+    tls_error(US"cert-status-req", US gnutls_strerror(rc), state->host, errstr);
+    return NULL;
+    }
+  tlsp->ocsp = OCSP_NOT_RESP;
   }
 #endif
 
 #ifndef DISABLE_EVENT
-if (tb->event_action)
+if (tb && tb->event_action)
   {
   state->event_action = tb->event_action;
   gnutls_session_set_ptr(state->session, state);
@@ -2041,30 +2421,33 @@ DEBUG(D_tls) debug_printf("about to gnutls_handshake\n");
 /* There doesn't seem to be a built-in timeout on connection. */
 
 sigalrm_seen = FALSE;
-alarm(ob->command_timeout);
+ALARM(ob->command_timeout);
 do
-  {
   rc = gnutls_handshake(state->session);
-  } while ((rc == GNUTLS_E_AGAIN) ||
-      (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen));
-alarm(0);
+while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
+ALARM_CLR(0);
 
 if (rc != GNUTLS_E_SUCCESS)
+  {
   if (sigalrm_seen)
     {
     gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_USER_CANCELED);
-    return tls_error(US"gnutls_handshake", "timed out", state->host, errstr);
+    tls_error(US"gnutls_handshake", US"timed out", state->host, errstr);
     }
   else
-    return tls_error(US"gnutls_handshake", gnutls_strerror(rc), state->host, errstr);
+    tls_error(US"gnutls_handshake", US gnutls_strerror(rc), state->host, errstr);
+  return NULL;
+  }
 
 DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
 
 /* Verify late */
 
-if (state->verify_requirement != VERIFY_NONE &&
-    !verify_certificate(state, errstr))
-  return tls_error(US"certificate verification failed", *errstr, state->host, errstr);
+if (!verify_certificate(state, errstr))
+  {
+  tls_error(US"certificate verification failed", *errstr, state->host, errstr);
+  return NULL;
+  }
 
 #ifndef DISABLE_OCSP
 if (require_ocsp)
@@ -2084,29 +2467,30 @@ if (require_ocsp)
       gnutls_free(printed.data);
       }
     else
-      (void) tls_error(US"ocsp decode", gnutls_strerror(rc), state->host, errstr);
+      (void) tls_error(US"ocsp decode", US gnutls_strerror(rc), state->host, errstr);
     }
 
   if (gnutls_ocsp_status_request_is_checked(state->session, 0) == 0)
     {
-    tls_out.ocsp = OCSP_FAILED;
-    return tls_error(US"certificate status check failed", NULL, state->host, errstr);
+    tlsp->ocsp = OCSP_FAILED;
+    tls_error(US"certificate status check failed", NULL, state->host, errstr);
+    return NULL;
     }
   DEBUG(D_tls) debug_printf("Passed OCSP checking\n");
-  tls_out.ocsp = OCSP_VFIED;
+  tlsp->ocsp = OCSP_VFIED;
   }
 #endif
 
 /* Figure out peer DN, and if authenticated, etc. */
 
-if ((rc = peer_status(state, errstr)) != OK)
-  return rc;
+if (peer_status(state, errstr) != OK)
+  return NULL;
 
 /* Sets various Exim expansion variables; may need to adjust for ACL callouts */
 
 extract_exim_vars_from_tls_state(state);
 
-return OK;
+return state;
 }
 
 
@@ -2120,39 +2504,127 @@ return OK;
 daemon, to shut down the TLS library, without actually doing a shutdown (which
 would tamper with the TLS session in the parent process).
 
-Arguments:   TRUE if gnutls_bye is to be called
+Arguments:
+  ct_ctx	client context pointer, or NULL for the one global server context
+  shutdown	1 if TLS close-alert is to be sent,
+		2 if also response to be waited for
+
 Returns:     nothing
 */
 
 void
-tls_close(BOOL is_server, BOOL shutdown)
+tls_close(void * ct_ctx, int shutdown)
 {
-exim_gnutls_state_st *state = is_server ? &state_server : &state_client;
+exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
 
-if (!state->tlsp || state->tlsp->active < 0) return;  /* TLS was not active */
+if (!state->tlsp || state->tlsp->active.sock < 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);
+  DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
+    shutdown > 1 ? " (with response-wait)" : "");
+
+  ALARM(2);
+  gnutls_bye(state->session, shutdown > 1 ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);
+  ALARM_CLR(0);
   }
 
 gnutls_deinit(state->session);
 gnutls_certificate_free_credentials(state->x509_cred);
 
 
-state->tlsp->active = -1;
+state->tlsp->active.sock = -1;
+state->tlsp->active.tls_ctx = NULL;
+if (state->xfer_buffer) store_free(state->xfer_buffer);
 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
+}
+
+
+
+
+static BOOL
+tls_refill(unsigned lim)
+{
+exim_gnutls_state_st * state = &state_server;
+ssize_t inbytes;
+
+DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
+  state->session, state->xfer_buffer, ssl_xfer_buffer_size);
 
-if ((state_server.session == NULL) && (state_client.session == NULL))
+sigalrm_seen = FALSE;
+if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
+
+do
+  inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
+    MIN(ssl_xfer_buffer_size, lim));
+while (inbytes == GNUTLS_E_AGAIN);
+
+if (smtp_receive_timeout > 0) ALARM_CLR(0);
+
+if (had_command_timeout)		/* set by signal handler */
+  smtp_command_timeout_exit();		/* does not return */
+if (had_command_sigterm)
+  smtp_command_sigterm_exit();
+if (had_data_timeout)
+  smtp_data_timeout_exit();
+if (had_data_sigint)
+  smtp_data_sigint_exit();
+
+/* Timeouts do not get this far.  A zero-byte return appears to mean that the
+TLS session has been closed down, not that the socket itself has been closed
+down. Revert to non-TLS handling. */
+
+if (sigalrm_seen)
   {
-  gnutls_global_deinit();
-  exim_gnutls_base_init_done = FALSE;
+  DEBUG(D_tls) debug_printf("Got tls read timeout\n");
+  state->xfer_error = TRUE;
+  return FALSE;
   }
-}
 
+else if (inbytes == 0)
+  {
+  DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
+
+  receive_getc = smtp_getc;
+  receive_getbuf = smtp_getbuf;
+  receive_get_cache = smtp_get_cache;
+  receive_ungetc = smtp_ungetc;
+  receive_feof = smtp_feof;
+  receive_ferror = smtp_ferror;
+  receive_smtp_buffered = smtp_buffered;
+
+  gnutls_deinit(state->session);
+  gnutls_certificate_free_credentials(state->x509_cred);
+
+  state->session = NULL;
+  state->tlsp->active.sock = -1;
+  state->tlsp->active.tls_ctx = NULL;
+  state->tlsp->bits = 0;
+  state->tlsp->certificate_verified = FALSE;
+  tls_channelbinding_b64 = NULL;
+  state->tlsp->cipher = NULL;
+  state->tlsp->peercert = NULL;
+  state->tlsp->peerdn = NULL;
+
+  return FALSE;
+  }
 
+/* Handle genuine errors */
 
+else if (inbytes < 0)
+  {
+  DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv(\n", __FUNCTION__);
+  record_io_error(state, (int) inbytes, US"recv", NULL);
+  state->xfer_error = TRUE;
+  return FALSE;
+  }
+#ifndef DISABLE_DKIM
+dkim_exim_verify_feed(state->xfer_buffer, inbytes);
+#endif
+state->xfer_buffer_hwm = (int) inbytes;
+state->xfer_buffer_lwm = 0;
+return TRUE;
+}
 
 /*************************************************
 *            TLS version of getc                 *
@@ -2164,84 +2636,48 @@ Only used by the server-side TLS.
 
 This feeds DKIM and should be used for all message-body reads.
 
-Arguments:  lim		Maximum amount to read/bufffer
+Arguments:  lim		Maximum amount to read/buffer
 Returns:    the next character or EOF
 */
 
 int
 tls_getc(unsigned lim)
 {
-exim_gnutls_state_st *state = &state_server;
-if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
-  {
-  ssize_t inbytes;
-
-  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);
-  inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
-    MIN(ssl_xfer_buffer_size, lim));
-  alarm(0);
-
-  /* Timeouts do not get this far; see command_timeout_handler().
-     A zero-byte return appears to mean that the TLS session has been
-     closed down, not that the socket itself has been closed down. Revert to
-     non-TLS handling. */
-
-  if (sigalrm_seen)
-    {
-    DEBUG(D_tls) debug_printf("Got tls read timeout\n");
-    state->xfer_error = 1;
-    return EOF;
-    }
-
-  else if (inbytes == 0)
-    {
-    DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
-
-    receive_getc = smtp_getc;
-    receive_get_cache = smtp_get_cache;
-    receive_ungetc = smtp_ungetc;
-    receive_feof = smtp_feof;
-    receive_ferror = smtp_ferror;
-    receive_smtp_buffered = smtp_buffered;
+exim_gnutls_state_st * state = &state_server;
 
-    gnutls_deinit(state->session);
-    gnutls_certificate_free_credentials(state->x509_cred);
+if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
+  if (!tls_refill(lim))
+    return state->xfer_error ? EOF : smtp_getc(lim);
 
-    state->session = NULL;
-    state->tlsp->active = -1;
-    state->tlsp->bits = 0;
-    state->tlsp->certificate_verified = FALSE;
-    tls_channelbinding_b64 = NULL;
-    state->tlsp->cipher = NULL;
-    state->tlsp->peercert = NULL;
-    state->tlsp->peerdn = NULL;
+/* Something in the buffer; return next uschar */
 
-    return smtp_getc(lim);
-    }
+return state->xfer_buffer[state->xfer_buffer_lwm++];
+}
 
-  /* Handle genuine errors */
+uschar *
+tls_getbuf(unsigned * len)
+{
+exim_gnutls_state_st * state = &state_server;
+unsigned size;
+uschar * buf;
 
-  else if (inbytes < 0)
+if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
+  if (!tls_refill(*len))
     {
-    record_io_error(state, (int) inbytes, US"recv", NULL);
-    state->xfer_error = 1;
-    return EOF;
+    if (!state->xfer_error) return smtp_getbuf(len);
+    *len = 0;
+    return NULL;
     }
-#ifndef DISABLE_DKIM
-  dkim_exim_verify_feed(state->xfer_buffer, inbytes);
-#endif
-  state->xfer_buffer_hwm = (int) inbytes;
-  state->xfer_buffer_lwm = 0;
-  }
 
-/* Something in the buffer; return next uschar */
-
-return state->xfer_buffer[state->xfer_buffer_lwm++];
+if ((size = state->xfer_buffer_hwm - state->xfer_buffer_lwm) > *len)
+  size = *len;
+buf = &state->xfer_buffer[state->xfer_buffer_lwm];
+state->xfer_buffer_lwm += size;
+*len = size;
+return buf;
 }
 
+
 void
 tls_get_cache()
 {
@@ -2254,6 +2690,14 @@ if (n > 0)
 }
 
 
+BOOL
+tls_could_read(void)
+{
+return state_server.xfer_buffer_lwm < state_server.xfer_buffer_hwm
+ || gnutls_record_check_pending(state_server.session) > 0;
+}
+
+
 
 
 /*************************************************
@@ -2264,17 +2708,18 @@ if (n > 0)
 then the caller must feed DKIM.
 
 Arguments:
+  ct_ctx    client context pointer, or NULL for the one global server context
   buff      buffer of data
   len       size of buffer
 
 Returns:    the number of bytes read
-            -1 after a failed read
+            -1 after a failed read, including EOF
 */
 
 int
-tls_read(BOOL is_server, uschar *buff, size_t len)
+tls_read(void * ct_ctx, uschar *buff, size_t len)
 {
-exim_gnutls_state_st *state = is_server ? &state_server : &state_client;
+exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
 ssize_t inbytes;
 
 if (len > INT_MAX)
@@ -2290,13 +2735,20 @@ DEBUG(D_tls)
   debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
       state->session, buff, len);
 
-inbytes = gnutls_record_recv(state->session, buff, len);
+do
+  inbytes = gnutls_record_recv(state->session, buff, len);
+while (inbytes == GNUTLS_E_AGAIN);
+
 if (inbytes > 0) return inbytes;
 if (inbytes == 0)
   {
   DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
   }
-else record_io_error(state, (int)inbytes, US"recv", NULL);
+else
+  {
+  DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv(\n", __FUNCTION__);
+  record_io_error(state, (int)inbytes, US"recv", NULL);
+  }
 
 return -1;
 }
@@ -2310,31 +2762,43 @@ return -1;
 
 /*
 Arguments:
-  is_server channel specifier
+  ct_ctx    client context pointer, or NULL for the one global server context
   buff      buffer of data
   len       number of bytes
+  more	    more data expected soon
 
 Returns:    the number of bytes after a successful write,
             -1 after a failed write
 */
 
 int
-tls_write(BOOL is_server, const uschar *buff, size_t len)
+tls_write(void * ct_ctx, const uschar * buff, size_t len, BOOL more)
 {
 ssize_t outbytes;
 size_t left = len;
-exim_gnutls_state_st *state = is_server ? &state_server : &state_client;
+exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
+#ifdef SUPPORT_CORK
+static BOOL corked = FALSE;
+
+if (more && !corked) gnutls_record_cork(state->session);
+#endif
+
+DEBUG(D_tls) debug_printf("%s(%p, " SIZE_T_FMT "%s)\n", __FUNCTION__,
+  buff, left, more ? ", more" : "");
 
-DEBUG(D_tls) debug_printf("tls_do_write(%p, " SIZE_T_FMT ")\n", buff, left);
 while (left > 0)
   {
   DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n",
       buff, left);
-  outbytes = gnutls_record_send(state->session, buff, left);
+
+  do
+    outbytes = gnutls_record_send(state->session, buff, left);
+  while (outbytes == GNUTLS_E_AGAIN);
 
   DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);
   if (outbytes < 0)
     {
+    DEBUG(D_tls) debug_printf("%s: gnutls_record_send err\n", __FUNCTION__);
     record_io_error(state, outbytes, US"send", NULL);
     return -1;
     }
@@ -2356,6 +2820,14 @@ if (len > INT_MAX)
   len = INT_MAX;
   }
 
+#ifdef SUPPORT_CORK
+if (more != corked)
+  {
+  if (!more) (void) gnutls_record_uncork(state->session, 0);
+  corked = more;
+  }
+#endif
+
 return (int) len;
 }