X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/94431adbd61d7706fe6df3a19bcae043fec950bf..a55697acf8d60ff8fc67f8fc46f23b8f53a3b823:/src/src/tls.c

diff --git a/src/src/tls.c b/src/src/tls.c
index 60f0cfe98..f95091218 100644
--- a/src/src/tls.c
+++ b/src/src/tls.c
@@ -2,13 +2,13 @@
 *     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. */
 
 /* 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.
 
@@ -19,6 +19,22 @@ functions from the OpenSSL or GNU TLS libraries. */
 #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
+
 /* 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
@@ -26,7 +42,7 @@ reference itself to stop picky compilers complaining that it is unused, and put
 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
 
@@ -37,16 +53,14 @@ We're moving away from this; GnuTLS is already using a state, which
 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     *
@@ -64,17 +78,18 @@ Returns:    TRUE if OK; result may still be NULL after forced 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 == NULL) *result = NULL; else
+if (!s)
+  *result = NULL;
+else if (  !(*result = expand_string(US s)) /* need to clean up const more */
+	&& !f.expand_string_forcedfail
+	)
   {
-  *result = expand_string(US s); /* need to clean up const some more */
-  if (*result == NULL && !expand_string_forcedfail)
-    {
-    log_write(0, LOG_MAIN|LOG_PANIC, "expansion of %s failed: %s", name,
-      expand_string_message);
-    return FALSE;
-    }
+  *errstr = US"Internal error";
+  log_write(0, LOG_MAIN|LOG_PANIC, "expansion of %s failed: %s", name,
+    expand_string_message);
+  return FALSE;
   }
 return TRUE;
 }
@@ -87,19 +102,20 @@ return TRUE;
 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();
 }
 
 /*************************************************
@@ -107,18 +123,18 @@ restore_tz(uschar * tz)
 *************************************************/
 
 #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)
+# 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
 
-#else
-#include "tls-openssl.c"
-#include "tlscert-openssl.c"
+#ifdef USE_OPENSSL
+# include "tls-openssl.c"
+# include "tlscert-openssl.c"
 #endif
 
 
@@ -160,7 +176,7 @@ Returns:       non-zero if the eof flag is set
 int
 tls_feof(void)
 {
-return ssl_xfer_eof;
+return (int)ssl_xfer_eof;
 }
 
 
@@ -182,7 +198,7 @@ Returns:       non-zero if the error flag is set
 int
 tls_ferror(void)
 {
-return ssl_xfer_error;
+return (int)ssl_xfer_error;
 }
 
 
@@ -204,7 +220,7 @@ return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm;
 }
 
 
-#endif  /* SUPPORT_TLS */
+#endif  /*DISABLE_TLS*/
 
 void
 tls_modify_variables(tls_support * dest_tsp)
@@ -213,13 +229,13 @@ modify_variable(US"tls_bits",                 &dest_tsp->bits);
 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         *
 ************************************************/
@@ -233,8 +249,7 @@ inplace.
 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++ = ',';
 }
@@ -261,7 +276,7 @@ uschar outsep = '\n';
 uschar * ele;
 uschar * match = NULL;
 int len;
-uschar * list = NULL;
+gstring * list = NULL;
 
 while ((ele = string_nextinlist(&mod, &insep, NULL, 0)))
   if (ele[0] != '>')
@@ -277,7 +292,7 @@ while ((ele = string_nextinlist(CUSS &dn, &insep, NULL, 0)))
      || Ustrncmp(ele, match, len) == 0 && ele[len] == '='
      )
     list = string_append_listele(list, outsep, ele+len+1);
-return list;
+return string_from_gstring(list);
 }
 
 
@@ -352,7 +367,115 @@ else if ((subjdn = tls_cert_subject(cert, NULL)))
   }
 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 = fork()) < 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(0);
+  }
+
+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
 */