Implement initial negotiation of EtM
Not implemented yet:
- actually using EtM
- conditions on renegotiation
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index ad67c22..c884e7c 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -635,6 +635,29 @@
}
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
+#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
+static int ssl_parse_encrypt_then_mac_ext( ssl_context *ssl,
+ const unsigned char *buf,
+ size_t len )
+{
+ if( len != 0 )
+ {
+ SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
+ return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
+ }
+
+ ((void) buf);
+
+ if( ssl->encrypt_then_mac == SSL_ETM_ENABLED &&
+ ssl->minor_ver != SSL_MINOR_VERSION_0 )
+ {
+ ssl->session_negotiate->encrypt_then_mac = SSL_ETM_ENABLED;
+ }
+
+ return( 0 );
+}
+#endif /* POLARSSL_SSL_ENCRYPT_THEN_MAC */
+
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
static int ssl_parse_extended_ms_ext( ssl_context *ssl,
const unsigned char *buf,
@@ -1523,6 +1546,16 @@
break;
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
+#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
+ case TLS_EXT_ENCRYPT_THEN_MAC:
+ SSL_DEBUG_MSG( 3, ( "found encrypt then mac extension" ) );
+
+ ret = ssl_parse_encrypt_then_mac_ext( ssl, ext + 4, ext_size );
+ if( ret != 0 )
+ return( ret );
+ break;
+#endif /* POLARSSL_SSL_ENCRYPT_THEN_MAC */
+
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
case TLS_EXT_EXTENDED_MASTER_SECRET:
SSL_DEBUG_MSG( 3, ( "found extended master secret extension" ) );
@@ -1682,6 +1715,32 @@
}
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
+#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
+static void ssl_write_encrypt_then_mac_ext( ssl_context *ssl,
+ unsigned char *buf,
+ size_t *olen )
+{
+ unsigned char *p = buf;
+
+ if( ssl->session_negotiate->encrypt_then_mac == SSL_EXTENDED_MS_DISABLED ||
+ ssl->minor_ver == SSL_MINOR_VERSION_0 )
+ {
+ *olen = 0;
+ return;
+ }
+
+ SSL_DEBUG_MSG( 3, ( "server hello, adding encrypt then mac extension" ) );
+
+ *p++ = (unsigned char)( ( TLS_EXT_ENCRYPT_THEN_MAC >> 8 ) & 0xFF );
+ *p++ = (unsigned char)( ( TLS_EXT_ENCRYPT_THEN_MAC ) & 0xFF );
+
+ *p++ = 0x00;
+ *p++ = 0x00;
+
+ *olen = 4;
+}
+#endif /* POLARSSL_SSL_ENCRYPT_THEN_MAC */
+
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
static void ssl_write_extended_ms_ext( ssl_context *ssl,
unsigned char *buf,
@@ -2012,6 +2071,11 @@
ext_len += olen;
#endif
+#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
+ ssl_write_encrypt_then_mac_ext( ssl, p + 2 + ext_len, &olen );
+ ext_len += olen;
+#endif
+
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
ssl_write_extended_ms_ext( ssl, p + 2 + ext_len, &olen );
ext_len += olen;