* Exim - an Internet mail transport agent *
*************************************************/
-/* Copyright (c) University of Cambridge 1995 - 2015 */
+/* Copyright (c) University of Cambridge 1995 - 2018 */
+/* Copyright (c) The Exim Maintainers 2020 */
/* See the file NOTICE for conditions of use and distribution. */
/* This module provides TLS (aka SSL) support for Exim. The code for OpenSSL is
based on a patch that was originally contributed by Steve Haslam. It was
adapted from stunnel, a GPL program by Michal Trojnara. The code for GNU TLS is
-based on a patch contributed by Nikos Mavroyanopoulos. Because these packages
+based on a patch contributed by Nikos Mavrogiannopoulos. Because these packages
are so very different, the functions for each are kept in separate files. The
relevant file is #included as required, after any any common functions.
#include "exim.h"
#include "transports/smtp.h"
+#if !defined(DISABLE_TLS) && !defined(USE_OPENSSL) && !defined(USE_GNUTLS)
+# error One of USE_OPENSSL or USE_GNUTLS must be defined for a TLS build
+#endif
+
+
+#if defined(MACRO_PREDEF) && !defined(DISABLE_TLS)
+# include "macro_predef.h"
+# ifdef USE_GNUTLS
+# include "tls-gnu.c"
+# else
+# include "tls-openssl.c"
+# endif
+#endif
+
+#ifndef MACRO_PREDEF
+
+static void tls_per_lib_daemon_init(void);
+static void tls_per_lib_daemon_tick(void);
+static void tls_server_creds_init(void);
+static void tls_server_creds_invalidate(void);
+static void tls_client_creds_init(transport_instance *, BOOL);
+static void tls_client_creds_invalidate(transport_instance *);
+static void tls_daemon_creds_reload(void);
+static BOOL opt_set_and_noexpand(const uschar *);
+static BOOL opt_unset_or_noexpand(const uschar *);
+
+
+
/* This module is compiled only when it is specifically requested in the
build-time configuration. However, some compilers don't like compiling empty
modules, so keep them happy with a dummy when skipping the rest. Make it
in a dummy argument to stop even pickier compilers complaining about infinite
loops. */
-#ifndef SUPPORT_TLS
+#ifdef DISABLE_TLS
static void dummy(int x) { dummy(x-1); }
-#else
+#else /* most of the rest of the file */
+
+const exim_tlslib_state null_tls_preload = {0};
/* Static variables that are used for buffering data by both sets of
functions and the common functions below.
can switch, so we can do TLS callouts during ACLs. */
static const int ssl_xfer_buffer_size = 4096;
-#ifndef USE_GNUTLS
+#ifdef USE_OPENSSL
static uschar *ssl_xfer_buffer = NULL;
static int ssl_xfer_buffer_lwm = 0;
static int ssl_xfer_buffer_hwm = 0;
-static int ssl_xfer_eof = 0;
-static int ssl_xfer_error = 0;
+static int ssl_xfer_eof = FALSE;
+static BOOL ssl_xfer_error = FALSE;
#endif
-uschar *tls_channelbinding_b64 = NULL;
-
/*************************************************
* Expand string; give error on failure *
*/
static BOOL
-expand_check(const uschar *s, const uschar *name, uschar **result)
+expand_check(const uschar *s, const uschar *name, uschar **result, uschar ** errstr)
+{
+if (!s)
+ *result = NULL;
+else if ( !(*result = expand_string(US s)) /* need to clean up const more */
+ && !f.expand_string_forcedfail
+ )
+ {
+ *errstr = US"Internal error";
+ log_write(0, LOG_MAIN|LOG_PANIC, "expansion of %s failed: %s", name,
+ expand_string_message);
+ return FALSE;
+ }
+return TRUE;
+}
+
+
+#ifdef EXIM_HAVE_INOTIFY
+/* Add the directory for a filename to the inotify handle, creating that if
+needed. This is enough to see changes to files in that dir.
+Return boolean success.
+
+The word "system" fails, which is on the safe side as we don't know what
+directory it implies nor if the TLS library handles a watch for us.
+
+The string "system,cache" is recognised and explicitly accepted without
+setting a watch. This permits the system CA bundle to be cached even though
+we have no way to tell when it gets modified by an update.
+
+We *might* try to run "openssl version -d" and set watches on the dir
+indicated in its output, plus the "certs" subdir of it (following
+synlimks for both). But this is undocumented even for OpenSSL, and
+who knows what GnuTLS might be doing.
+
+A full set of caching including the CAs takes 35ms output off of the
+server tls_init() (GnuTLS, Fedora 32, 2018-class x86_64 laptop hardware).
+*/
+static BOOL
+tls_set_one_watch(const uschar * filename)
+{
+uschar * s;
+
+if (Ustrcmp(filename, "system,cache") == 0) return TRUE;
+
+if (!(s = Ustrrchr(filename, '/'))) return FALSE;
+s = string_copyn(filename, s - filename);
+DEBUG(D_tls) debug_printf("watch dir '%s'\n", s);
+
+if (inotify_add_watch(tls_watch_fd, CCS s,
+ IN_ONESHOT | IN_CLOSE_WRITE | IN_DELETE | IN_DELETE_SELF
+ | IN_MOVED_FROM | IN_MOVED_TO | IN_MOVE_SELF) >= 0)
+ return TRUE;
+DEBUG(D_tls) debug_printf("add_watch: %s\n", strerror(errno));
+return FALSE;
+}
+
+
+/* Create an inotify facility if needed.
+Then set watches on the dir containing the given file or (optionally)
+list of files. Return boolean success. */
+
+static BOOL
+tls_set_watch(const uschar * filename, BOOL list)
{
-if (s == NULL) *result = NULL; else
+rmark r;
+BOOL rc = FALSE;
+
+if (tls_watch_fd < 0 && (tls_watch_fd = inotify_init1(O_CLOEXEC)) < 0)
{
- *result = expand_string(US s); /* need to clean up const some more */
- if (*result == NULL && !expand_string_forcedfail)
+ DEBUG(D_tls) debug_printf("inotify_init: %s\n", strerror(errno));
+ return FALSE;
+ }
+
+if (!filename || !*filename) return TRUE;
+
+r = store_mark();
+
+if (list)
+ {
+ int sep = 0;
+ for (uschar * s; s = string_nextinlist(&filename, &sep, NULL, 0); )
+ if (!(rc = tls_set_one_watch(s))) break;
+ }
+else
+ rc = tls_set_one_watch(filename);
+
+store_reset(r);
+return rc;
+}
+
+
+/* Called, after a delay for multiple file ops to get done, from
+the daemon when any of the watches added (above) fire.
+
+Dump the set of watches and arrange to reload cached creds (which
+will set up new watches). */
+
+static void
+tls_watch_triggered(void)
+{
+DEBUG(D_tls) debug_printf("watch triggered\n");
+close(tls_watch_fd);
+tls_watch_fd = -1;
+
+tls_daemon_creds_reload();
+}
+#endif /* EXIM_HAVE_INOTIFY */
+
+
+void
+tls_client_creds_reload(BOOL watch)
+{
+for(transport_instance * t = transports; t; t = t->next)
+ if (Ustrcmp(t->driver_name, "smtp") == 0)
{
- log_write(0, LOG_MAIN|LOG_PANIC, "expansion of %s failed: %s", name,
- expand_string_message);
- return FALSE;
+ tls_client_creds_invalidate(t);
+ tls_client_creds_init(t, watch);
}
+}
+
+static void
+tls_daemon_creds_reload(void)
+{
+tls_server_creds_invalidate();
+tls_server_creds_init();
+
+tls_client_creds_reload(TRUE);
+}
+
+
+/* Utility predicates for use by the per-library code */
+static BOOL
+opt_set_and_noexpand(const uschar * opt)
+{ return opt && *opt && Ustrchr(opt, '$') == NULL; }
+
+static BOOL
+opt_unset_or_noexpand(const uschar * opt)
+{ return !opt || Ustrchr(opt, '$') == NULL; }
+
+
+
+/* Called every time round the daemon loop */
+
+void
+tls_daemon_tick(void)
+{
+tls_per_lib_daemon_tick();
+#ifdef EXIM_HAVE_INOTIFY
+if (tls_watch_trigger_time && time(NULL) >= tls_watch_trigger_time + 5)
+ {
+ tls_watch_trigger_time = 0;
+ tls_watch_triggered();
}
-return TRUE;
+#endif
+}
+
+/* Called once at daemon startup */
+
+void
+tls_daemon_init(void)
+{
+tls_per_lib_daemon_init();
}
static uschar *
to_tz(uschar * tz)
{
- uschar * old = US getenv("TZ");
- setenv("TZ", CS tz, 1);
- tzset();
- return old;
+uschar * old = US getenv("TZ");
+(void) setenv("TZ", CCS tz, 1);
+tzset();
+return old;
}
+
static void
restore_tz(uschar * tz)
{
- if (tz)
- setenv("TZ", CS tz, 1);
- else
- unsetenv("TZ");
- tzset();
+if (tz)
+ (void) setenv("TZ", CCS tz, 1);
+else
+ (void) os_unsetenv(US"TZ");
+tzset();
}
/*************************************************
*************************************************/
#ifdef USE_GNUTLS
-#include "tls-gnu.c"
-#include "tlscert-gnu.c"
-
-#define ssl_xfer_buffer (state_server.xfer_buffer)
-#define ssl_xfer_buffer_lwm (state_server.xfer_buffer_lwm)
-#define ssl_xfer_buffer_hwm (state_server.xfer_buffer_hwm)
-#define ssl_xfer_eof (state_server.xfer_eof)
-#define ssl_xfer_error (state_server.xfer_error)
-
-#else
-#include "tls-openssl.c"
-#include "tlscert-openssl.c"
+# include "tls-gnu.c"
+# include "tlscert-gnu.c"
+# define ssl_xfer_buffer (state_server.xfer_buffer)
+# define ssl_xfer_buffer_lwm (state_server.xfer_buffer_lwm)
+# define ssl_xfer_buffer_hwm (state_server.xfer_buffer_hwm)
+# define ssl_xfer_eof (state_server.xfer_eof)
+# define ssl_xfer_error (state_server.xfer_error)
+#endif
+
+#ifdef USE_OPENSSL
+# include "tls-openssl.c"
+# include "tlscert-openssl.c"
#endif
int
tls_feof(void)
{
-return ssl_xfer_eof;
+return (int)ssl_xfer_eof;
}
int
tls_ferror(void)
{
-return ssl_xfer_error;
+return (int)ssl_xfer_error;
}
}
-#endif /* SUPPORT_TLS */
+#endif /*DISABLE_TLS*/
void
tls_modify_variables(tls_support * dest_tsp)
modify_variable(US"tls_certificate_verified", &dest_tsp->certificate_verified);
modify_variable(US"tls_cipher", &dest_tsp->cipher);
modify_variable(US"tls_peerdn", &dest_tsp->peerdn);
-#if defined(SUPPORT_TLS) && !defined(USE_GNUTLS)
+#ifdef USE_OPENSSL
modify_variable(US"tls_sni", &dest_tsp->sni);
#endif
}
-#ifdef SUPPORT_TLS
+#ifndef DISABLE_TLS
/************************************************
* TLS certificate name operations *
************************************************/
static void
dn_to_list(uschar * dn)
{
-uschar * cp;
-for (cp = dn; *cp; cp++)
+for (uschar * cp = dn; *cp; cp++)
if (cp[0] == '\\' && cp[1] == ',')
*cp++ = ',';
}
uschar * ele;
uschar * match = NULL;
int len;
-uschar * list = NULL;
+gstring * list = NULL;
while ((ele = string_nextinlist(&mod, &insep, NULL, 0)))
if (ele[0] != '>')
|| Ustrncmp(ele, match, len) == 0 && ele[len] == '='
)
list = string_append_listele(list, outsep, ele+len+1);
-return list;
+return string_from_gstring(list);
}
}
return FALSE;
}
-#endif /*SUPPORT_TLS*/
+
+
+/* Environment cleanup: The GnuTLS library uses SSLKEYLOGFILE in the environment
+and writes a file by that name. Our OpenSSL code does the same, using keying
+info from the library API.
+The GnuTLS support only works if exim is run by root, not taking advantage of
+the setuid bit.
+You can use either the external environment (modulo the keep_environment config)
+or the add_environment config option for SSLKEYLOGFILE; the latter takes
+precedence.
+
+If the path is absolute, require it starts with the spooldir; otherwise delete
+the env variable. If relative, prefix the spooldir.
+*/
+void
+tls_clean_env(void)
+{
+uschar * path = US getenv("SSLKEYLOGFILE");
+if (path)
+ if (!*path)
+ unsetenv("SSLKEYLOGFILE");
+ else if (*path != '/')
+ {
+ DEBUG(D_tls)
+ debug_printf("prepending spooldir to env SSLKEYLOGFILE\n");
+ setenv("SSLKEYLOGFILE", CCS string_sprintf("%s/%s", spool_directory, path), 1);
+ }
+ else if (Ustrncmp(path, spool_directory, Ustrlen(spool_directory)) != 0)
+ {
+ DEBUG(D_tls)
+ debug_printf("removing env SSLKEYLOGFILE=%s: not under spooldir\n", path);
+ unsetenv("SSLKEYLOGFILE");
+ }
+}
+
+/*************************************************
+* Drop privs for checking TLS config *
+*************************************************/
+
+/* We want to validate TLS options during readconf, but do not want to be
+root when we call into the TLS library, in case of library linkage errors
+which cause segfaults; before this check, those were always done as the Exim
+runtime user and it makes sense to continue with that.
+
+Assumes: tls_require_ciphers has been set, if it will be
+ exim_user has been set, if it will be
+ exim_group has been set, if it will be
+
+Returns: bool for "okay"; false will cause caller to immediately exit.
+*/
+
+BOOL
+tls_dropprivs_validate_require_cipher(BOOL nowarn)
+{
+const uschar *errmsg;
+pid_t pid;
+int rc, status;
+void (*oldsignal)(int);
+
+/* If TLS will never be used, no point checking ciphers */
+
+if ( !tls_advertise_hosts
+ || !*tls_advertise_hosts
+ || Ustrcmp(tls_advertise_hosts, ":") == 0
+ )
+ return TRUE;
+else if (!nowarn && !tls_certificate)
+ log_write(0, LOG_MAIN,
+ "Warning: No server certificate defined; will use a selfsigned one.\n"
+ " Suggested action: either install a certificate or change tls_advertise_hosts option");
+
+oldsignal = signal(SIGCHLD, SIG_DFL);
+
+fflush(NULL);
+if ((pid = exim_fork(US"cipher-validate")) < 0)
+ log_write(0, LOG_MAIN|LOG_PANIC_DIE, "fork failed for TLS check");
+
+if (pid == 0)
+ {
+ /* in some modes, will have dropped privilege already */
+ if (!geteuid())
+ exim_setugid(exim_uid, exim_gid, FALSE,
+ US"calling tls_validate_require_cipher");
+
+ if ((errmsg = tls_validate_require_cipher()))
+ log_write(0, LOG_PANIC_DIE|LOG_CONFIG,
+ "tls_require_ciphers invalid: %s", errmsg);
+ fflush(NULL);
+ exim_underbar_exit(EXIT_SUCCESS);
+ }
+
+do {
+ rc = waitpid(pid, &status, 0);
+} while (rc < 0 && errno == EINTR);
+
+DEBUG(D_tls)
+ debug_printf("tls_validate_require_cipher child %d ended: status=0x%x\n",
+ (int)pid, status);
+
+signal(SIGCHLD, oldsignal);
+
+return status == 0;
+}
+
+
+
+
+#endif /*!DISABLE_TLS*/
+#endif /*!MACRO_PREDEF*/
/* vi: aw ai sw=2
*/
git://git.exim.org / exim.git / blobdiff