Merge fix for AEAD Random IVs

ChangeLog

@@ -3,6 +3,10 @@ mbed TLS ChangeLog (Sorted per branch, date)
 = mbed TLS 2.3.x branch released 2016-xx-xx
 
 Security
+   * Remove MBEDTLS_SSL_AEAD_RANDOM_IV option, because it was not compliant
+     with RFC5116 and could lead to session key recovery in very long TLS
+     sessions. (H. Bock, A. Zauner, S. Devlin, J. Somorovsky, P. Jovanovic -
+     "Nonce-Disrespecting Adversaries Practical Forgery Attacks on GCM in TLS")
    * Fix potential stack corruption in mbedtls_x509write_crt_der() and
      mbedtls_x509write_csr_der() when the signature is copied to the buffer
      without checking whether there is enough space in the destination. The

include/mbedtls/config.h

@@ -940,18 +940,6 @@
  */
 //#define MBEDTLS_SHA256_SMALLER
 
-/**
- * \def MBEDTLS_SSL_AEAD_RANDOM_IV
- *
- * Generate a random IV rather than using the record sequence number as a
- * nonce for ciphersuites using and AEAD algorithm (GCM or CCM).
- *
- * Using the sequence number is generally recommended.
- *
- * Uncomment this macro to always use random IVs with AEAD ciphersuites.
- */
-//#define MBEDTLS_SSL_AEAD_RANDOM_IV
-
 /**
  * \def MBEDTLS_SSL_ALL_ALERT_MESSAGES
  *

library/ssl_tls.c

@@ -1373,17 +1373,6 @@ static int ssl_encrypt_buf( mbedtls_ssl_context *ssl )
         /*
          * Generate IV
          */
-#if defined(MBEDTLS_SSL_AEAD_RANDOM_IV)
-        ret = ssl->conf->f_rng( ssl->conf->p_rng,
-                ssl->transform_out->iv_enc + ssl->transform_out->fixed_ivlen,
-                ssl->transform_out->ivlen - ssl->transform_out->fixed_ivlen );
-        if( ret != 0 )
-            return( ret );
-
-        memcpy( ssl->out_iv,
-                ssl->transform_out->iv_enc + ssl->transform_out->fixed_ivlen,
-                ssl->transform_out->ivlen - ssl->transform_out->fixed_ivlen );
-#else
         if( ssl->transform_out->ivlen - ssl->transform_out->fixed_ivlen != 8 )
         {
             /* Reminder if we ever add an AEAD mode with a different size */
@@ -1394,7 +1383,6 @@ static int ssl_encrypt_buf( mbedtls_ssl_context *ssl )
         memcpy( ssl->transform_out->iv_enc + ssl->transform_out->fixed_ivlen,
                              ssl->out_ctr, 8 );
         memcpy( ssl->out_iv, ssl->out_ctr, 8 );
-#endif
 
         MBEDTLS_SSL_DEBUG_BUF( 4, "IV used", ssl->out_iv,
                 ssl->transform_out->ivlen - ssl->transform_out->fixed_ivlen );

library/version_features.c

@@ -324,9 +324,6 @@ static const char *features[] = {
 #if defined(MBEDTLS_SHA256_SMALLER)
     "MBEDTLS_SHA256_SMALLER",
 #endif /* MBEDTLS_SHA256_SMALLER */
-#if defined(MBEDTLS_SSL_AEAD_RANDOM_IV)
-    "MBEDTLS_SSL_AEAD_RANDOM_IV",
-#endif /* MBEDTLS_SSL_AEAD_RANDOM_IV */
 #if defined(MBEDTLS_SSL_ALL_ALERT_MESSAGES)
     "MBEDTLS_SSL_ALL_ALERT_MESSAGES",
 #endif /* MBEDTLS_SSL_ALL_ALERT_MESSAGES */

tests/ssl-opt.sh

@@ -333,8 +333,10 @@ detect_dtls() {
 # Usage: run_test name [-p proxy_cmd] srv_cmd cli_cmd cli_exit [option [...]]
 # Options:  -s pattern  pattern that must be present in server output
 #           -c pattern  pattern that must be present in client output
+#           -u pattern  lines after pattern must be unique in client output
 #           -S pattern  pattern that must be absent in server output
 #           -C pattern  pattern that must be absent in client output
+#           -U pattern  lines after pattern must be unique in server output
 run_test() {
     NAME="$1"
     shift 1
@@ -475,28 +477,49 @@ run_test() {
         case $1 in
             "-s")
                 if grep -v '^==' $SRV_OUT | grep -v 'Serious error when reading debug info' | grep "$2" >/dev/null; then :; else
-                    fail "-s $2"
+                    fail "pattern '$2' MUST be present in the Server output"
                     return
                 fi
                 ;;
 
             "-c")
                 if grep -v '^==' $CLI_OUT | grep -v 'Serious error when reading debug info' | grep "$2" >/dev/null; then :; else
-                    fail "-c $2"
+                    fail "pattern '$2' MUST be present in the Client output"
                     return
                 fi
                 ;;
 
             "-S")
                 if grep -v '^==' $SRV_OUT | grep -v 'Serious error when reading debug info' | grep "$2" >/dev/null; then
-                    fail "-S $2"
+                    fail "pattern '$2' MUST NOT be present in the Server output"
                     return
                 fi
                 ;;
 
             "-C")
                 if grep -v '^==' $CLI_OUT | grep -v 'Serious error when reading debug info' | grep "$2" >/dev/null; then
-                    fail "-C $2"
+                    fail "pattern '$2' MUST NOT be present in the Client output"
+                    return
+                fi
+                ;;
+
+                # The filtering in the following two options (-u and -U) do the following
+                #   - ignore valgrind output
+                #   - filter out everything but lines right after the pattern occurances
+                #   - keep one of each non-unique line
+                #   - count how many lines remain
+                # A line with '--' will remain in the result from previous outputs, so the number of lines in the result will be 1
+                # if there were no duplicates.
+            "-U")
+                if [ $(grep -v '^==' $SRV_OUT | grep -v 'Serious error when reading debug info' | grep -A1 "$2" | grep -v "$2" | sort | uniq -d | wc -l) -gt 1 ]; then
+                    fail "lines following pattern '$2' must be unique in Server output"
+                    return
+                fi
+                ;;
+
+            "-u")
+                if [ $(grep -v '^==' $CLI_OUT | grep -v 'Serious error when reading debug info' | grep -A1 "$2" | grep -v "$2" | sort | uniq -d | wc -l) -gt 1 ]; then
+                    fail "lines following pattern '$2' must be unique in Client output"
                     return
                 fi
                 ;;
@@ -639,6 +662,14 @@ run_test    "Default, DTLS" \
             -s "Protocol is DTLSv1.2" \
             -s "Ciphersuite is TLS-ECDHE-ECDSA-WITH-AES-256-GCM-SHA384"
 
+# Test for uniqueness of IVs in AEAD ciphersuites
+run_test    "Unique IV in GCM" \
+            "$P_SRV exchanges=20 debug_level=4" \
+            "$P_CLI exchanges=20 debug_level=4 force_ciphersuite=TLS-ECDHE-ECDSA-WITH-AES-256-GCM-SHA384" \
+            0 \
+            -u "IV used" \
+            -U "IV used"
+
 # Tests for rc4 option
 
 requires_config_enabled MBEDTLS_REMOVE_ARC4_CIPHERSUITES