GnuTLS: lose DH-param setup, for recent library versions where no longer needed

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 3afc62989a093566ea0686f3dd72f88f42034ea6..c0c7bdc80e487e02d6c89a0a2d336020a0b700a2 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -17736,7 +17736,14 @@ larger prime than requested.
 The value of this option is expanded and indicates the source of DH parameters
 to be used by Exim.
 
 The value of this option is expanded and indicates the source of DH parameters
 to be used by Exim.
 

-&*Note: The Exim Maintainers strongly recommend using a filename with site-generated
+.new
+&*Note: This option is ignored for GnuTLS version 3.6.0 and later.
+The library manages parameter negitiation internally.
+.wen
+
+&*Note: The Exim Maintainers strongly recommend,
+for other TLS braries,
+using a filename with site-generated

 local DH parameters*&, which has been supported across all versions of Exim.  The
 other specific constants available are a fallback so that even when
 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
 local DH parameters*&, which has been supported across all versions of Exim.  The
 other specific constants available are a fallback so that even when
 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.

diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog
index cad1f5abb6f859870b79e0383a6faaba355a5ed2..93f4a1eb2d7ca2118903ceaa8d9e7c36591e60aa 100644 (file)
--- a/doc/doc-txt/ChangeLog
+++ b/doc/doc-txt/ChangeLog
@@ -187,6 +187,11 @@ JH/39 Promote DMARC support to mainline.
 
 JH/40 Bug 2452: Add a References: header to DSNs.
 
 
 JH/40 Bug 2452: Add a References: header to DSNs.
 

+JH/41 With GnuTLS 3.6.0 (and later) do not attempt to manage Diffie-Hellman
+      parameters.  The relevant library call is documented as "Deprecated: This
+      function is unnecessary and discouraged on GnuTLS 3.6.0 or later. Since
+      3.6.0, DH parameters are negotiated following RFC7919."
+

 
 Exim version 4.92
 -----------------
 
 Exim version 4.92
 -----------------

diff --git a/src/src/tls-gnu.c b/src/src/tls-gnu.c
index 22f7fe5489434b3980812e4fa363500a4d7179d5..13bf905a0153a836f5be183c8986ff43abd0165b 100644 (file)
--- a/src/src/tls-gnu.c
+++ b/src/src/tls-gnu.c
@@ -76,6 +76,9 @@ require current GnuTLS, then we'll drop support for the ancient libraries).
 #if GNUTLS_VERSION_NUMBER >= 0x030506 && !defined(DISABLE_OCSP)
 # define SUPPORT_SRV_OCSP_STACK
 #endif
 #if GNUTLS_VERSION_NUMBER >= 0x030506 && !defined(DISABLE_OCSP)
 # define SUPPORT_SRV_OCSP_STACK
 #endif

+#if GNUTLS_VERSION_NUMBER >= 0x030600
+# define GNUTLS_AUTO_DHPARAMS
+#endif

 #if GNUTLS_VERSION_NUMBER >= 0x030603
 # define EXIM_HAVE_TLS1_3
 # define SUPPORT_GNUTLS_EXT_RAW_PARSE
 #if GNUTLS_VERSION_NUMBER >= 0x030603
 # define EXIM_HAVE_TLS1_3
 # define SUPPORT_GNUTLS_EXT_RAW_PARSE


@@ -217,11 +220,13 @@ XXX But see gnutls_session_get_ptr()
 
 static exim_gnutls_state_st state_server;
 
 
 static exim_gnutls_state_st state_server;
 

+#ifndef GNUTLS_AUTO_DHPARAMS

 /* 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 gnutls_dh_params_t dh_server_params = NULL;
 /* 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 gnutls_dh_params_t dh_server_params = NULL;

+#endif

 
 static int ssl_session_timeout = 7200; /* Two hours */
 
 
 static int ssl_session_timeout = 7200; /* Two hours */
 


@@ -524,6 +529,7 @@ tlsp->sni =    state->received_sni;
 
 
 
 
 
 

+#ifndef GNUTLS_AUTO_DHPARAMS

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


@@ -546,7 +552,7 @@ init_server_dh(uschar ** errstr)
 {
 int fd, rc;
 unsigned int dh_bits;
 {
 int fd, rc;
 unsigned int dh_bits;

-gnutls_datum_t m;
+gnutls_datum_t m = {.data = NULL, .size = 0};

 uschar filename_buf[PATH_MAX];
 uschar *filename = NULL;
 size_t sz;
 uschar filename_buf[PATH_MAX];
 uschar *filename = NULL;
 size_t sz;


@@ -559,9 +565,6 @@ DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n");
 if ((rc = gnutls_dh_params_init(&dh_server_params)))
   return tls_error_gnu(US"gnutls_dh_params_init", rc, host, errstr);
 
 if ((rc = gnutls_dh_params_init(&dh_server_params)))
   return tls_error_gnu(US"gnutls_dh_params_init", rc, host, errstr);
 

-m.data = NULL;
-m.size = 0;
-

 if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam, errstr))
   return DEFER;
 
 if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam, errstr))
   return DEFER;
 


@@ -711,14 +714,12 @@ if (rc < 0)
     return tls_error_sys(US"Unable to open temp file", errno, NULL, errstr);
   (void)exim_chown(temp_fn, exim_uid, exim_gid);   /* Probably not necessary */
 
     return tls_error_sys(US"Unable to open temp file", errno, NULL, errstr);
   (void)exim_chown(temp_fn, exim_uid, exim_gid);   /* Probably not necessary */
 

-  /* 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.
-   */
+  /* 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;
   if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10)
     {
     dh_bits_gen = dh_bits - 10;


@@ -781,6 +782,7 @@ if (rc < 0)
 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
 return OK;
 }
 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
 return OK;
 }

+#endif

 
 
 
 
 
 


@@ -1395,6 +1397,7 @@ tls_set_remaining_x509(exim_gnutls_state_st *state, uschar ** errstr)
 int rc;
 const host_item *host = state->host;  /* macro should be reconsidered? */
 
 int rc;
 const host_item *host = state->host;  /* macro should be reconsidered? */
 

+#ifndef GNUTLS_AUTO_DHPARAMS

 /* 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. */
 /* 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. */


@@ -1403,8 +1406,11 @@ if (!state->host)
   {
   if (!dh_server_params)
     if ((rc = init_server_dh(errstr)) != OK) return rc;
   {
   if (!dh_server_params)
     if ((rc = init_server_dh(errstr)) != OK) return rc;

+
+  /* Unnecessary & discouraged with 3.6.0 or later */

   gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
   }
   gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
   }

+#endif

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