io: Add support for fragmented websocket binary frames

Allows fragmented binary frames by saving the previous opcode. Handles
the case where an intermediary (i.e., web proxy) fragments frames
originally sent unfragmented by the client.

Signed-off-by: Brandon Carpenter <brandon.carpenter@cypherpath.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

2 files changed, 19 insertions, 8 deletions

diff --git a/include/io/channel-websock.h b/include/io/channel-websock.h
index 3c9ff84727..7c896557c5 100644
--- a/include/io/channel-websock.h
+++ b/include/io/channel-websock.h
@@ -65,6 +65,7 @@ struct QIOChannelWebsock {
     guint io_tag;
     Error *io_err;
     gboolean io_eof;
+    uint8_t opcode;
 };
 
 /**
diff --git a/io/channel-websock.c b/io/channel-websock.c
index 4e5afb2e95..909d6367f0 100644
--- a/io/channel-websock.c
+++ b/io/channel-websock.c
@@ -636,28 +636,38 @@ static int qio_channel_websock_decode_header(QIOChannelWebsock *ioc,
     has_mask = header->b1 & QIO_CHANNEL_WEBSOCK_HEADER_FIELD_HAS_MASK;
     payload_len = header->b1 & QIO_CHANNEL_WEBSOCK_HEADER_FIELD_PAYLOAD_LEN;
 
+    /* Save or restore opcode. */
+    if (opcode) {
+        ioc->opcode = opcode;
+    } else {
+        opcode = ioc->opcode;
+    }
+
     if (opcode == QIO_CHANNEL_WEBSOCK_OPCODE_CLOSE) {
         /* disconnect */
         return 0;
     }
 
     /* Websocket frame sanity check:
-     * * Websocket fragmentation is not supported.
-     * * All  websockets frames sent by a client have to be masked.
+     * * Fragmentation is only supported for binary frames.
+     * * All frames sent by a client MUST be masked.
      * * Only binary encoding is supported.
      */
     if (!fin) {
-        error_setg(errp, "websocket fragmentation is not supported");
-        return -1;
+        if (opcode != QIO_CHANNEL_WEBSOCK_OPCODE_BINARY_FRAME) {
+            error_setg(errp, "only binary websocket frames may be fragmented");
+            return -1;
+        }
+    } else {
+        if (opcode != QIO_CHANNEL_WEBSOCK_OPCODE_BINARY_FRAME) {
+            error_setg(errp, "only binary websocket frames are supported");
+            return -1;
+        }
     }
     if (!has_mask) {
         error_setg(errp, "client websocket frames must be masked");
         return -1;
     }
-    if (opcode != QIO_CHANNEL_WEBSOCK_OPCODE_BINARY_FRAME) {
-        error_setg(errp, "only binary websocket frames are supported");
-        return -1;
-    }
 
     if (payload_len < QIO_CHANNEL_WEBSOCK_PAYLOAD_LEN_MAGIC_16_BIT) {
         ioc->payload_remain = payload_len;