Implement ALPN server-side
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 16fb264..2cbc798 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -683,6 +683,69 @@
}
#endif /* POLARSSL_SSL_SESSION_TICKETS */
+#if defined(POLARSSL_SSL_ALPN)
+static int ssl_parse_alpn_ext( ssl_context *ssl,
+ unsigned char *buf, size_t len )
+{
+ size_t list_len, cur_len;
+ const unsigned char *theirs, *start, *end;
+ const char **ours;
+
+ /* If ALPN not configured, just ignore the extension */
+ if( ssl->alpn_list == NULL )
+ return( 0 );
+
+ /*
+ * opaque ProtocolName<1..2^8-1>;
+ *
+ * struct {
+ * ProtocolName protocol_name_list<2..2^16-1>
+ * } ProtocolNameList;
+ */
+
+ /* Min length is 2 (list_len) + 1 (name_len) + 1 (name) */
+ if( len < 4 )
+ return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
+
+ list_len = ( buf[0] << 8 ) | buf[1];
+ if( list_len != len - 2 )
+ return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
+
+ /*
+ * Use our order of preference
+ */
+ start = buf + 2;
+ end = buf + len;
+ for( ours = ssl->alpn_list; *ours != NULL; ours++ )
+ {
+ for( theirs = start; theirs != end; theirs += cur_len )
+ {
+ /* If the list is well formed, we should get equality first */
+ if( theirs > end )
+ return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
+
+ cur_len = *theirs++;
+
+ /* Empty strings MUST NOT be included */
+ if( cur_len == 0 )
+ return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
+
+ if( cur_len == strlen( *ours ) &&
+ memcmp( theirs, *ours, cur_len ) == 0 )
+ {
+ ssl->alpn_chosen = *ours;
+ return( 0 );
+ }
+ }
+ }
+
+ /* If we get there, no match was found */
+ ssl_send_alert_message( ssl, SSL_ALERT_LEVEL_FATAL,
+ SSL_ALERT_MSG_NO_APPLICATION_PROTOCOL );
+ return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
+}
+#endif /* POLARSSL_SSL_ALPN */
+
/*
* Auxiliary functions for ServerHello parsing and related actions
*/
@@ -1385,6 +1448,16 @@
break;
#endif /* POLARSSL_SSL_SESSION_TICKETS */
+#if defined(POLARSSL_SSL_ALPN)
+ case TLS_EXT_ALPN:
+ SSL_DEBUG_MSG( 3, ( "found ALPN extension" ) );
+
+ ret = ssl_parse_alpn_ext( ssl, ext + 4, ext_size );
+ if( ret != 0 )
+ return( ret );
+ break;
+#endif /* POLARSSL_SSL_SESSION_TICKETS */
+
default:
SSL_DEBUG_MSG( 3, ( "unknown extension found: %d (ignoring)",
ext_id ) );
@@ -1625,6 +1698,42 @@
}
#endif /* POLARSSL_ECDH_C || POLARSSL_ECDSA_C */
+#if defined(POLARSSL_SSL_ALPN )
+static void ssl_write_alpn_ext( ssl_context *ssl,
+ unsigned char *buf, size_t *olen )
+{
+ if( ssl->alpn_chosen == NULL )
+ {
+ *olen = 0;
+ return;
+ }
+
+ SSL_DEBUG_MSG( 3, ( "server hello, alpn extension" ) );
+
+ /*
+ * 0 . 1 ext identifier
+ * 2 . 3 ext length
+ * 4 . 5 protocol list length
+ * 6 . 6 protocol name length
+ * 7 . 7+n protocol name
+ */
+ buf[0] = (unsigned char)( ( TLS_EXT_ALPN >> 8 ) & 0xFF );
+ buf[1] = (unsigned char)( ( TLS_EXT_ALPN ) & 0xFF );
+
+ *olen = 7 + strlen( ssl->alpn_chosen );
+
+ buf[2] = (unsigned char)( ( ( *olen - 4 ) >> 8 ) & 0xFF );
+ buf[3] = (unsigned char)( ( ( *olen - 4 ) ) & 0xFF );
+
+ buf[4] = (unsigned char)( ( ( *olen - 6 ) >> 8 ) & 0xFF );
+ buf[5] = (unsigned char)( ( ( *olen - 6 ) ) & 0xFF );
+
+ buf[6] = (unsigned char)( ( ( *olen - 7 ) ) & 0xFF );
+
+ memcpy( buf + 7, ssl->alpn_chosen, *olen - 7 );
+}
+#endif /* POLARSSL_ECDH_C || POLARSSL_ECDSA_C */
+
static int ssl_write_server_hello( ssl_context *ssl )
{
#if defined(POLARSSL_HAVE_TIME)
@@ -1791,6 +1900,11 @@
ext_len += olen;
#endif
+#if defined(POLARSSL_SSL_ALPN)
+ ssl_write_alpn_ext( ssl, p + 2 + ext_len, &olen );
+ ext_len += olen;
+#endif
+
SSL_DEBUG_MSG( 3, ( "server hello, total extension length: %d", ext_len ) );
*p++ = (unsigned char)( ( ext_len >> 8 ) & 0xFF );