Merge pull request #3050 from mpg/skip-close-notify-dev

Fix possible close_notify/ClientHello confusion
diff --git a/programs/ssl/ssl_client2.c b/programs/ssl/ssl_client2.c
index c188900..ab72f15 100644
--- a/programs/ssl/ssl_client2.c
+++ b/programs/ssl/ssl_client2.c
@@ -145,6 +145,7 @@
 #define DFL_REPRODUCIBLE        0
 #define DFL_NSS_KEYLOG          0
 #define DFL_NSS_KEYLOG_FILE     NULL
+#define DFL_SKIP_CLOSE_NOTIFY   0
 
 #define GET_REQUEST "GET %s HTTP/1.0\r\nExtra-header: "
 #define GET_REQUEST_END "\r\n\r\n"
@@ -389,6 +390,7 @@
     "                        options: 1 (level-triggered, implies nbio=1),\n" \
     "    read_timeout=%%d     default: 0 ms (no timeout)\n"        \
     "    max_resend=%%d       default: 0 (no resend on timeout)\n" \
+    "    skip_close_notify=%%d default: 0 (send close_notify)\n" \
     "\n"                                                    \
     USAGE_DTLS                                              \
     USAGE_CID                                               \
@@ -517,6 +519,7 @@
     const char *cid_val_renego; /* the CID to use for incoming messages
                                  * after renegotiation                      */
     int reproducible;           /* make communication reproducible          */
+    int skip_close_notify;      /* skip sending the close_notify alert      */
 } opt;
 
 int query_config( const char *config );
@@ -1311,6 +1314,7 @@
     opt.reproducible        = DFL_REPRODUCIBLE;
     opt.nss_keylog          = DFL_NSS_KEYLOG;
     opt.nss_keylog_file     = DFL_NSS_KEYLOG_FILE;
+    opt.skip_close_notify   = DFL_SKIP_CLOSE_NOTIFY;
 
     for( i = 1; i < argc; i++ )
     {
@@ -1723,6 +1727,12 @@
         {
             opt.nss_keylog_file = q;
         }
+        else if( strcmp( p, "skip_close_notify" ) == 0 )
+        {
+            opt.skip_close_notify = atoi( q );
+            if( opt.skip_close_notify < 0 || opt.skip_close_notify > 1 )
+                goto usage;
+        }
         else
             goto usage;
     }
@@ -3160,10 +3170,25 @@
     mbedtls_printf( "  . Closing the connection..." );
     fflush( stdout );
 
-    /* No error checking, the connection might be closed already */
-    do ret = mbedtls_ssl_close_notify( &ssl );
-    while( ret == MBEDTLS_ERR_SSL_WANT_WRITE );
-    ret = 0;
+    /*
+     * Most of the time sending a close_notify before closing is the right
+     * thing to do. However, when the server already knows how many messages
+     * are expected and closes the connection by itself, this alert becomes
+     * redundant. Sometimes with DTLS this redundancy becomes a problem by
+     * leading to a race condition where the server might close the connection
+     * before seeing the alert, and since UDP is connection-less when the
+     * alert arrives it will be seen as a new connection, which will fail as
+     * the alert is clearly not a valid ClientHello. This may cause spurious
+     * failures in tests that use DTLS and resumption with ssl_server2 in
+     * ssl-opt.sh, avoided by enabling skip_close_notify client-side.
+     */
+    if( opt.skip_close_notify == 0 )
+    {
+        /* No error checking, the connection might be closed already */
+        do ret = mbedtls_ssl_close_notify( &ssl );
+        while( ret == MBEDTLS_ERR_SSL_WANT_WRITE );
+        ret = 0;
+    }
 
     mbedtls_printf( " done\n" );
 
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index e65b8ec..8585b25 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -2535,7 +2535,7 @@
 
 run_test    "Session resume using tickets, DTLS: basic" \
             "$P_SRV debug_level=3 dtls=1 tickets=1" \
-            "$P_CLI debug_level=3 dtls=1 tickets=1 reconnect=1" \
+            "$P_CLI debug_level=3 dtls=1 tickets=1 reconnect=1 skip_close_notify=1" \
             0 \
             -c "client hello, adding session ticket extension" \
             -s "found session ticket extension" \
@@ -2549,7 +2549,7 @@
 
 run_test    "Session resume using tickets, DTLS: cache disabled" \
             "$P_SRV debug_level=3 dtls=1 tickets=1 cache_max=0" \
-            "$P_CLI debug_level=3 dtls=1 tickets=1 reconnect=1" \
+            "$P_CLI debug_level=3 dtls=1 tickets=1 reconnect=1 skip_close_notify=1" \
             0 \
             -c "client hello, adding session ticket extension" \
             -s "found session ticket extension" \
@@ -2563,7 +2563,7 @@
 
 run_test    "Session resume using tickets, DTLS: timeout" \
             "$P_SRV debug_level=3 dtls=1 tickets=1 cache_max=0 ticket_timeout=1" \
-            "$P_CLI debug_level=3 dtls=1 tickets=1 reconnect=1 reco_delay=2" \
+            "$P_CLI debug_level=3 dtls=1 tickets=1 reconnect=1 skip_close_notify=1 reco_delay=2" \
             0 \
             -c "client hello, adding session ticket extension" \
             -s "found session ticket extension" \
@@ -2577,7 +2577,7 @@
 
 run_test    "Session resume using tickets, DTLS: session copy" \
             "$P_SRV debug_level=3 dtls=1 tickets=1 cache_max=0" \
-            "$P_CLI debug_level=3 dtls=1 tickets=1 reconnect=1 reco_mode=0" \
+            "$P_CLI debug_level=3 dtls=1 tickets=1 reconnect=1 skip_close_notify=1 reco_mode=0" \
             0 \
             -c "client hello, adding session ticket extension" \
             -s "found session ticket extension" \
@@ -2718,7 +2718,7 @@
 
 run_test    "Session resume using cache, DTLS: tickets enabled on client" \
             "$P_SRV dtls=1 debug_level=3 tickets=0" \
-            "$P_CLI dtls=1 debug_level=3 tickets=1 reconnect=1" \
+            "$P_CLI dtls=1 debug_level=3 tickets=1 reconnect=1 skip_close_notify=1" \
             0 \
             -c "client hello, adding session ticket extension" \
             -s "found session ticket extension" \
@@ -2732,7 +2732,7 @@
 
 run_test    "Session resume using cache, DTLS: tickets enabled on server" \
             "$P_SRV dtls=1 debug_level=3 tickets=1" \
-            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1" \
+            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1 skip_close_notify=1" \
             0 \
             -C "client hello, adding session ticket extension" \
             -S "found session ticket extension" \
@@ -2746,7 +2746,7 @@
 
 run_test    "Session resume using cache, DTLS: cache_max=0" \
             "$P_SRV dtls=1 debug_level=3 tickets=0 cache_max=0" \
-            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1" \
+            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1 skip_close_notify=1" \
             0 \
             -S "session successfully restored from cache" \
             -S "session successfully restored from ticket" \
@@ -2755,7 +2755,7 @@
 
 run_test    "Session resume using cache, DTLS: cache_max=1" \
             "$P_SRV dtls=1 debug_level=3 tickets=0 cache_max=1" \
-            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1" \
+            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1 skip_close_notify=1" \
             0 \
             -s "session successfully restored from cache" \
             -S "session successfully restored from ticket" \
@@ -2764,7 +2764,7 @@
 
 run_test    "Session resume using cache, DTLS: timeout > delay" \
             "$P_SRV dtls=1 debug_level=3 tickets=0" \
-            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1 reco_delay=0" \
+            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1 skip_close_notify=1 reco_delay=0" \
             0 \
             -s "session successfully restored from cache" \
             -S "session successfully restored from ticket" \
@@ -2773,7 +2773,7 @@
 
 run_test    "Session resume using cache, DTLS: timeout < delay" \
             "$P_SRV dtls=1 debug_level=3 tickets=0 cache_timeout=1" \
-            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1 reco_delay=2" \
+            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1 skip_close_notify=1 reco_delay=2" \
             0 \
             -S "session successfully restored from cache" \
             -S "session successfully restored from ticket" \
@@ -2782,7 +2782,7 @@
 
 run_test    "Session resume using cache, DTLS: no timeout" \
             "$P_SRV dtls=1 debug_level=3 tickets=0 cache_timeout=0" \
-            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1 reco_delay=2" \
+            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1 skip_close_notify=1 reco_delay=2" \
             0 \
             -s "session successfully restored from cache" \
             -S "session successfully restored from ticket" \
@@ -2791,7 +2791,7 @@
 
 run_test    "Session resume using cache, DTLS: session copy" \
             "$P_SRV dtls=1 debug_level=3 tickets=0" \
-            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1 reco_mode=0" \
+            "$P_CLI dtls=1 debug_level=3 tickets=0 reconnect=1 skip_close_notify=1 reco_mode=0" \
             0 \
             -s "session successfully restored from cache" \
             -S "session successfully restored from ticket" \
@@ -4543,19 +4543,19 @@
 
 run_test    "Event-driven I/O, DTLS: ticket + client auth + resume" \
             "$P_SRV dtls=1 event=1 tickets=1 auth_mode=required" \
-            "$P_CLI dtls=1 event=1 tickets=1 reconnect=1" \
+            "$P_CLI dtls=1 event=1 tickets=1 reconnect=1 skip_close_notify=1" \
             0 \
             -c "Read from server: .* bytes read"
 
 run_test    "Event-driven I/O, DTLS: ticket + resume" \
             "$P_SRV dtls=1 event=1 tickets=1 auth_mode=none" \
-            "$P_CLI dtls=1 event=1 tickets=1 reconnect=1" \
+            "$P_CLI dtls=1 event=1 tickets=1 reconnect=1 skip_close_notify=1" \
             0 \
             -c "Read from server: .* bytes read"
 
 run_test    "Event-driven I/O, DTLS: session-id resume" \
             "$P_SRV dtls=1 event=1 tickets=0 auth_mode=none" \
-            "$P_CLI dtls=1 event=1 tickets=0 reconnect=1" \
+            "$P_CLI dtls=1 event=1 tickets=0 reconnect=1 skip_close_notify=1" \
             0 \
             -c "Read from server: .* bytes read"
 
@@ -4567,7 +4567,7 @@
 run_test    "Event-driven I/O, DTLS: session-id resume, UDP packing" \
             -p "$P_PXY pack=50" \
             "$P_SRV dtls=1 event=1 tickets=0 auth_mode=required" \
-            "$P_CLI dtls=1 event=1 tickets=0 reconnect=1" \
+            "$P_CLI dtls=1 event=1 tickets=0 reconnect=1 skip_close_notify=1" \
             0 \
             -c "Read from server: .* bytes read"
 
@@ -7807,7 +7807,7 @@
              key_file=data_files/server8.key \
              hs_timeout=10000-60000 \
              force_ciphersuite=TLS-ECDHE-ECDSA-WITH-AES-128-GCM-SHA256 \
-             mtu=1450 reconnect=1 reco_delay=1" \
+             mtu=1450 reconnect=1 skip_close_notify=1 reco_delay=1" \
             0 \
             -S "autoreduction" \
             -s "found fragmented DTLS handshake message" \
@@ -8656,7 +8656,7 @@
             "$P_SRV dtls=1 dgram_packing=0 hs_timeout=500-10000 tickets=0 auth_mode=none \
              psk=abc123 debug_level=3" \
             "$P_CLI dtls=1 dgram_packing=0 hs_timeout=500-10000 tickets=0 psk=abc123 \
-             debug_level=3 reconnect=1 read_timeout=1000 max_resend=10 \
+             debug_level=3 reconnect=1 skip_close_notify=1 read_timeout=1000 max_resend=10 \
              force_ciphersuite=TLS-PSK-WITH-AES-128-CCM-8" \
             0 \
             -s "a session has been resumed" \
@@ -8670,7 +8670,7 @@
             "$P_SRV dtls=1 dgram_packing=0 hs_timeout=500-10000 tickets=0 auth_mode=none \
              psk=abc123 debug_level=3 nbio=2" \
             "$P_CLI dtls=1 dgram_packing=0 hs_timeout=500-10000 tickets=0 psk=abc123 \
-             debug_level=3 reconnect=1 read_timeout=1000 max_resend=10 \
+             debug_level=3 reconnect=1 skip_close_notify=1 read_timeout=1000 max_resend=10 \
              force_ciphersuite=TLS-PSK-WITH-AES-128-CCM-8 nbio=2" \
             0 \
             -s "a session has been resumed" \