GnuTLS: Fix client detection of server reject of client cert under TLS1.3

(cherry picked from commit fc243e944ec00b59b75f41d07494116f925d58b4)

12 files changed, 111 insertions, 44 deletions

diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog
index 66c8a7a1b..867a1d8ab 100644
--- a/doc/doc-txt/ChangeLog
+++ b/doc/doc-txt/ChangeLog
@@ -11,6 +11,13 @@ Since version 4.92
 JH/06 Fix buggy handling of autoreply bounce_return_size_limit, and a possible
       buffer overrun for (non-chunking) other transports.
 
+JH/07 GnuTLS: Our use of late (post-handshake) certificate verification, under
+      TLS1.3, means that a server rejecting a client certificate is not visible
+      to the client until the first read of encrypted data (typically the
+      response to EHLO).  Add detection for that case and treat it as a failed
+      TLS connection attempt, so that the normal retry-in-clear can work (if
+      suitably configured).
+
 
 Exim version 4.92
 -----------------
diff --git a/src/src/deliver.c b/src/src/deliver.c
index 664d00452..e17994117 100644
--- a/src/src/deliver.c
+++ b/src/src/deliver.c
@@ -7433,7 +7433,7 @@ if (addr_senddsn)
 
     tctx.u.fd = fd;
     tctx.options = topt_add_return_path | topt_no_body;
-    /*XXX hmm, retval ignored.
+    /*XXX hmm, FALSE(fail) retval ignored.
     Could error for any number of reasons, and they are not handled. */
     transport_write_message(&tctx, 0);
     fflush(f);
diff --git a/src/src/smtp_out.c b/src/src/smtp_out.c
index 9bd90c77a..b194e8043 100644
--- a/src/src/smtp_out.c
+++ b/src/src/smtp_out.c
@@ -688,20 +688,22 @@ Returns:    TRUE if a valid, non-error response was received; else FALSE
 /*XXX could move to smtp transport; no other users */
 
 BOOL
-smtp_read_response(void * sx0, uschar *buffer, int size, int okdigit,
+smtp_read_response(void * sx0, uschar * buffer, int size, int okdigit,
    int timeout)
 {
 smtp_context * sx = sx0;
-uschar *ptr = buffer;
-int count = 0;
+uschar * ptr = buffer;
+int count = 0, rc;
 
 errno = 0;  /* Ensure errno starts out zero */
 
 #ifdef EXPERIMENTAL_PIPE_CONNECT
 if (sx->pending_BANNER || sx->pending_EHLO)
-  if (smtp_reap_early_pipe(sx, &count) != OK)
+  if ((rc = smtp_reap_early_pipe(sx, &count)) != OK)
     {
     DEBUG(D_transport) debug_printf("failed reaping pipelined cmd responsess\n");
+    buffer[0] = '\0';
+    if (rc == DEFER) errno = ERRNO_TLSFAILURE;
     return FALSE;
     }
 #endif
diff --git a/src/src/tls-gnu.c b/src/src/tls-gnu.c
index c404dc29a..de2d70c09 100644
--- a/src/src/tls-gnu.c
+++ b/src/src/tls-gnu.c
@@ -229,7 +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 */
 
@@ -1278,7 +1278,6 @@ int rc;
 size_t sz;
 const char *errpos;
 uschar *p;
-BOOL want_default_priorities;
 
 if (!exim_gnutls_base_init_done)
   {
@@ -1387,32 +1386,24 @@ 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(rc, string_sprintf(
       "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
diff --git a/src/src/transports/lmtp.c b/src/src/transports/lmtp.c
index 240d78b21..57b346d49 100644
--- a/src/src/transports/lmtp.c
+++ b/src/src/transports/lmtp.c
@@ -122,7 +122,8 @@ Arguments:
 Returns:       TRUE if a "QUIT" command should be sent, else FALSE
 */
 
-static BOOL check_response(int *errno_value, int more_errno, uschar *buffer,
+static BOOL
+check_response(int *errno_value, int more_errno, uschar *buffer,
   int *yield, uschar **message)
 {
 *yield = '4';    /* Default setting is to give a temporary error */
diff --git a/src/src/transports/smtp.c b/src/src/transports/smtp.c
index a351da847..bfd6018dc 100644
--- a/src/src/transports/smtp.c
+++ b/src/src/transports/smtp.c
@@ -594,6 +594,11 @@ switch(*errno_value)
 	  pl, smtp_command, s);
     return FALSE;
 
+  case ERRNO_TLSFAILURE:	/* Handle bad first read; can happen with
+				GnuTLS and TLS1.3 */
+    *message = US"bad first read from TLS conn";
+    return TRUE;
+
   case ERRNO_FILTER_FAIL:	/* Handle a failed filter process error;
 			  can't send QUIT as we mustn't end the DATA. */
     *message = string_sprintf("transport filter process failed (%d)%s",
@@ -942,6 +947,7 @@ Arguments:
 
 Return:
  OK	all well
+ DEFER	error on first read of TLS'd conn
  FAIL	SMTP error in response
 */
 int
@@ -949,6 +955,7 @@ smtp_reap_early_pipe(smtp_context * sx, int * countp)
 {
 BOOL pending_BANNER = sx->pending_BANNER;
 BOOL pending_EHLO = sx->pending_EHLO;
+int rc = FAIL;
 
 sx->pending_BANNER = FALSE;	/* clear early to avoid recursion */
 sx->pending_EHLO = FALSE;
@@ -960,6 +967,7 @@ if (pending_BANNER)
   if (!smtp_reap_banner(sx))
     {
     DEBUG(D_transport) debug_printf("bad banner\n");
+    if (tls_out.active.sock >= 0) rc = DEFER;
     goto fail;
     }
   }
@@ -974,6 +982,7 @@ if (pending_EHLO)
   if (!smtp_reap_ehlo(sx))
     {
     DEBUG(D_transport) debug_printf("bad response for EHLO\n");
+    if (tls_out.active.sock >= 0) rc = DEFER;
     goto fail;
     }
 
@@ -1011,7 +1020,7 @@ return OK;
 fail:
   invalidate_ehlo_cache_entry(sx);
   (void) smtp_discard_responses(sx, sx->conn_args.ob, *countp);
-  return FAIL;
+  return rc;
 }
 #endif
 
@@ -1056,6 +1065,7 @@ Returns:      3 if at least one address had 2xx and one had 5xx
              -2 I/O or other non-response error for RCPT
              -3 DATA or MAIL failed - errno and buffer set
 	     -4 banner or EHLO failed (early-pipelining)
+	     -5 banner or EHLO failed (early-pipelining, TLS)
 */
 
 static int
@@ -1064,10 +1074,11 @@ sync_responses(smtp_context * sx, int count, int pending_DATA)
 address_item * addr = sx->sync_addr;
 smtp_transport_options_block * ob = sx->conn_args.ob;
 int yield = 0;
+int rc;
 
 #ifdef EXPERIMENTAL_PIPE_CONNECT
-if (smtp_reap_early_pipe(sx, &count) != OK)
-  return -4;
+if ((rc = smtp_reap_early_pipe(sx, &count)) != OK)
+  return rc == FAIL ? -4 : -5;
 #endif
 
 /* Handle the response for a MAIL command. On error, reinstate the original
@@ -1083,6 +1094,8 @@ if (sx->pending_MAIL)
     {
     DEBUG(D_transport) debug_printf("bad response for MAIL\n");
     Ustrcpy(big_buffer, mail_command);  /* Fits, because it came from there! */
+    if (errno == ERRNO_TLSFAILURE)
+      return -5;
     if (errno == 0 && sx->buffer[0] != 0)
       {
       int save_errno = 0;
@@ -1141,6 +1154,11 @@ while (count-- > 0)
       }
     }
 
+  /* Error on first TLS read */
+
+  else if (errno == ERRNO_TLSFAILURE)
+    return -5;
+
   /* Timeout while reading the response */
 
   else if (errno == ETIMEDOUT)
@@ -1253,6 +1271,10 @@ if (pending_DATA != 0)
     int code;
     uschar *msg;
     BOOL pass_message;
+
+    if (errno == ERRNO_TLSFAILURE)	/* Error on first TLS read */
+      return -5;
+
     if (pending_DATA > 0 || (yield & 1) != 0)
       {
       if (errno == 0 && sx->buffer[0] == '4')
@@ -1802,7 +1824,9 @@ Args:
    tc_chunk_last	add LAST option to SMTP BDAT command
    tc_reap_prev		reap response to previous SMTP commands
 
-Returns:	OK or ERROR
+Returns:
+  OK or ERROR
+  DEFER			TLS error on first read (EHLO-resp); errno set
 */
 
 static int
@@ -1859,10 +1883,12 @@ if (flags & tc_reap_prev  &&  prev_cmd_count > 0)
     case 2: sx->completed_addr = TRUE;	/* 5xx (only) => progress made */
     case 0: break;			/* No 2xx or 5xx, but no probs */
 
-    case -1:				/* Timeout on RCPT */
+    case -5: errno = ERRNO_TLSFAILURE;
+	     return DEFER;
 #ifdef EXPERIMENTAL_PIPE_CONNECT
     case -4:				/* non-2xx for pipelined banner or EHLO */
 #endif
+    case -1:				/* Timeout on RCPT */
     default: return ERROR;		/* I/O error, or any MAIL/DATA error */
     }
   cmd_count = 1;
@@ -1933,6 +1959,9 @@ BOOL pass_message = FALSE;
 uschar * message = NULL;
 int yield = OK;
 int rc;
+#ifdef SUPPORT_TLS
+uschar * tls_errstr;
+#endif
 
 sx->conn_args.ob = ob;
 
@@ -2474,27 +2503,27 @@ if (  smtp_peer_options & OPTION_TLS
   TLS_NEGOTIATE:
     {
     address_item * addr;
-    uschar * errstr;
     sx->cctx.tls_ctx = tls_client_start(sx->cctx.sock, sx->conn_args.host,
 			    sx->addrlist, sx->conn_args.tblock,
 # ifdef SUPPORT_DANE
 			     sx->dane ? &tlsa_dnsa : NULL,
 # endif
-			     &tls_out, &errstr);
+			     &tls_out, &tls_errstr);
 
     if (!sx->cctx.tls_ctx)
       {
       /* TLS negotiation failed; give an error. From outside, this function may
       be called again to try in clear on a new connection, if the options permit
       it for this host. */
-      DEBUG(D_tls) debug_printf("TLS session fail: %s\n", errstr);
+GNUTLS_CONN_FAILED:
+      DEBUG(D_tls) debug_printf("TLS session fail: %s\n", tls_errstr);
 
 # ifdef SUPPORT_DANE
       if (sx->dane)
         {
 	log_write(0, LOG_MAIN,
 	  "DANE attempt failed; TLS connection to %s [%s]: %s",
-	  sx->conn_args.host->name, sx->conn_args.host->address, errstr);
+	  sx->conn_args.host->name, sx->conn_args.host->address, tls_errstr);
 #  ifndef DISABLE_EVENT
 	(void) event_raise(sx->conn_args.tblock->event_action,
 	  US"dane:fail", US"validation-failure");	/* could do with better detail */
@@ -2503,7 +2532,7 @@ if (  smtp_peer_options & OPTION_TLS
 # endif
 
       errno = ERRNO_TLSFAILURE;
-      message = string_sprintf("TLS session: %s", errstr);
+      message = string_sprintf("TLS session: %s", tls_errstr);
       sx->send_quit = FALSE;
       goto TLS_FAILED;
       }
@@ -2601,7 +2630,22 @@ if (tls_out.active.sock >= 0)
 #endif
     {
     if (!smtp_reap_ehlo(sx))
+#ifdef USE_GNUTLS
+      {
+      /* The GnuTLS layer in Exim only spots a server-rejection of a client
+      cert late, under TLS1.3 - which means here; the first time we try to
+      receive crypted data.  Treat it as if it was a connect-time failure.
+      See also the early-pipe equivalent... which will be hard; every call
+      to sync_responses will need to check the result.
+      It would be nicer to have GnuTLS check the cert during the handshake.
+      Can it do that, with all the flexibility we need? */
+
+      tls_errstr = US"error on first read";
+      goto GNUTLS_CONN_FAILED;
+      }
+#else
       goto RESPONSE_FAILED;
+#endif
     smtp_peer_options = 0;
     }
   }
@@ -3261,6 +3305,7 @@ for (addr = sx->first_addr, address_count = 0;
 
 #ifdef EXPERIMENTAL_PIPE_CONNECT
       case -4: return -1;			/* non-2xx for pipelined banner or EHLO */
+      case -5: return -1;			/* TLS first-read error */
 #endif
       }
     sx->pending_MAIL = FALSE;            /* Dealt with MAIL */
@@ -3589,11 +3634,12 @@ if (  !(sx.peer_offered & OPTION_CHUNKING)
 
     case 1: sx.ok = TRUE;            /* 2xx (only) => OK, but if LMTP, */
     if (!sx.lmtp) sx.completed_addr = TRUE; /* can't tell about progress yet */
-    case 0: break;                       /* No 2xx or 5xx, but no probs */
+    case 0: break;			/* No 2xx or 5xx, but no probs */
 
-    case -1: goto END_OFF;               /* Timeout on RCPT */
+    case -1: goto END_OFF;		/* Timeout on RCPT */
 
 #ifdef EXPERIMENTAL_PIPE_CONNECT
+    case -5:				/* TLS first-read error */
     case -4:  HDEBUG(D_transport)
 		debug_printf("failed reaping pipelined cmd responses\n");
 #endif
@@ -3730,19 +3776,20 @@ else
       {
       case 3: sx.ok = TRUE;            /* 2xx & 5xx => OK & progress made */
       case 2: sx.completed_addr = TRUE;    /* 5xx (only) => progress made */
-      break;
+	      break;
 
-      case 1: sx.ok = TRUE;            /* 2xx (only) => OK, but if LMTP, */
+      case 1: sx.ok = TRUE;		/* 2xx (only) => OK, but if LMTP, */
       if (!sx.lmtp) sx.completed_addr = TRUE; /* can't tell about progress yet */
-      case 0: break;                       /* No 2xx or 5xx, but no probs */
+      case 0: break;			/* No 2xx or 5xx, but no probs */
 
-      case -1: goto END_OFF;               /* Timeout on RCPT */
+      case -1: goto END_OFF;		/* Timeout on RCPT */
 
 #ifdef EXPERIMENTAL_PIPE_CONNECT
+      case -5:				/* TLS first-read error */
       case -4:  HDEBUG(D_transport)
 		  debug_printf("failed reaping pipelined cmd responses\n");
 #endif
-      default: goto RESPONSE_FAILED;       /* I/O error, or any MAIL/DATA error */
+      default: goto RESPONSE_FAILED;	/* I/O error, or any MAIL/DATA error */
       }
     }
 
diff --git a/test/confs/2027 b/test/confs/2027
index cc47218fb..c1b93a2ce 100644
--- a/test/confs/2027
+++ b/test/confs/2027
@@ -47,9 +47,11 @@ local_delivery:
   user = CALLER
 
 send_to_server:
-  driver = smtp
+  driver =	smtp
   allow_localhost
-  hosts = ${if eq{$local_part}{userx}{127.0.0.1}{HOSTIPV4}}
-  port = PORT_D
+  hosts =	${if eq{$local_part}{userx}{127.0.0.1}{HOSTIPV4}}
+  port =	PORT_D
+  tls_verify_certificates =	DIR/aux-fixed/cert1
+  tls_verify_cert_hostnames =	:
 
 # End
diff --git a/test/confs/5652 b/test/confs/5652
index 13c8d8617..28d3a95bb 100644
--- a/test/confs/5652
+++ b/test/confs/5652
@@ -29,6 +29,7 @@ tls_ocsp_file =   DRSA/server1.example.com/server1.example.com.ocsp.good.resp \
 	      : DECDSA/server1.example_ec.com/server1.example_ec.com.ocsp.good.resp
 
 
+tls_require_ciphers = NORMAL:!VERS-TLS1.3
 
 # ------ ACL ------
 
diff --git a/test/confs/5821 b/test/confs/5821
index 86ddbdedd..8a2d6459e 100644
--- a/test/confs/5821
+++ b/test/confs/5821
@@ -23,7 +23,7 @@ tls_certificate = ${if eq {SERVER}{server} {CDIR2/fullchain.pem}fail}
 tls_privatekey =  ${if eq {SERVER}{server} {CDIR2/server1.example.com.unlocked.key}fail}
 
 # Permit two specific ciphers
-tls_require_ciphers = NORMAL:-KX-ALL:+RSA:-CIPHER-ALL:+AES-128-CBC:+CAMELLIA-256-GCM
+tls_require_ciphers = NORMAL:-VERS-TLS1.3:-KX-ALL:+RSA:-CIPHER-ALL:+AES-128-CBC:+CAMELLIA-256-GCM
 
 # ----- Routers -----
 begin routers
diff --git a/test/log/2027 b/test/log/2027
index 0bdd86a57..499351cd0 100644
--- a/test/log/2027
+++ b/test/log/2027
@@ -1,7 +1,7 @@
 1999-03-02 09:44:33 10HmaX-0005vi-00 <= CALLER@myhost.test.ex U=CALLER P=local S=sss
 1999-03-02 09:44:33 10HmaY-0005vi-00 <= CALLER@myhost.test.ex U=CALLER P=local S=sss
 1999-03-02 09:44:33 Start queue run: pid=pppp -qf
-1999-03-02 09:44:33 10HmaX-0005vi-00 => userx@test.ex R=client T=send_to_server H=127.0.0.1 [127.0.0.1] X=TLS1.x:ke-RSA-AES256-SHAnnn:xxx CV=no C="250 OK id=10HmaZ-0005vi-00"
+1999-03-02 09:44:33 10HmaX-0005vi-00 => userx@test.ex R=client T=send_to_server H=127.0.0.1 [127.0.0.1] X=TLS1.x:ke-RSA-AES256-SHAnnn:xxx CV=yes C="250 OK id=10HmaZ-0005vi-00"
 1999-03-02 09:44:33 10HmaX-0005vi-00 Completed
 1999-03-02 09:44:33 10HmaY-0005vi-00 TLS session: (gnutls_handshake): A TLS fatal alert has been received.: delivering unencrypted to H=ip4.ip4.ip4.ip4 [ip4.ip4.ip4.ip4] (not in hosts_require_tls)
 1999-03-02 09:44:33 10HmaY-0005vi-00 => usery@test.ex R=client T=send_to_server H=ip4.ip4.ip4.ip4 [ip4.ip4.ip4.ip4] C="250 OK id=10HmbA-0005vi-00"
diff --git a/test/runtest b/test/runtest
index 10ae833ff..dafca16ec 100755
--- a/test/runtest
+++ b/test/runtest
@@ -1253,6 +1253,20 @@ RESET_AFTER_EXTRA_LINE_READ:
     s/(DANE attempt failed.*error:)[0-9A-F]{8}(:SSL routines:)(ssl3_get_server_certificate|tls_process_server_certificate|CONNECT_CR_CERT)(?=:certificate verify failed$)/$1xxxxxxxx$2ssl3_get_server_certificate/;
     s/(DKIM: validation error: )error:[0-9A-F]{8}:rsa routines:(?:(?i)int_rsa_verify|CRYPTO_internal):(?:bad signature|algorithm mismatch)$/$1Public key signature verification has failed./;
 
+    # gnutls version variances
+    if (/TLS error on connection \(recv\): .* Decode error/)
+      {
+      my $prev = $_;
+      $_ = <IN>;
+      if (/error on first read/)
+	{
+	s/TLS session: \Kerror on first read:/(gnutls_handshake): A TLS fatal alert has been received.:/;
+	goto RESET_AFTER_EXTRA_LINE_READ;
+	}
+      else
+	{ $_ = $prev; }
+      }
+
     # DKIM timestamps
     if ( /(DKIM: d=.*) t=([0-9]*) x=([0-9]*) / )
       {
diff --git a/test/scripts/2000-GnuTLS/2027 b/test/scripts/2000-GnuTLS/2027
index 0d94ac4cd..3e071b665 100644
--- a/test/scripts/2000-GnuTLS/2027
+++ b/test/scripts/2000-GnuTLS/2027
@@ -3,9 +3,11 @@ gnutls
 munge gnutls_handshake
 exim -DSERVER=server -bd -oX PORT_D
 ****
+# will send to 127.0.0.1 and the server requests a client-cert
 exim userx@test.ex
 Test message
 ****
+# will send to HOSTIPV4 and the server requests&requires
 exim usery@test.ex
 Test message
 ****