[sr-dev] git:master:4fabe253: websocket: check bounds before reading mask

[Armen Babikyan]

Module: kamailio
Branch: master
Commit: 4fabe253a1eb0f9b494521cfa98365523a93adcf
URL: https://github.com/kamailio/kamailio/commit/4fabe253a1eb0f9b494521cfa98365523a93adcf

Author: Armen Babikyan <armen at firespotter.com>
Committer: Armen Babikyan <armen at firespotter.com>
Date: 2018-01-25T17:43:33-08:00

websocket: check bounds before reading mask

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Modified: src/modules/websocket/ws_frame.c

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Diff:  https://github.com/kamailio/kamailio/commit/4fabe253a1eb0f9b494521cfa98365523a93adcf.diff
Patch: https://github.com/kamailio/kamailio/commit/4fabe253a1eb0f9b494521cfa98365523a93adcf.patch

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diff --git a/src/modules/websocket/ws_frame.c b/src/modules/websocket/ws_frame.c
index 9bc3268601..32a1f4bf6a 100644
--- a/src/modules/websocket/ws_frame.c
+++ b/src/modules/websocket/ws_frame.c
@@ -470,13 +470,6 @@ static int decode_and_validate_ws_frame(ws_frame_t *frame,
 	} else
 		mask_start = 2;
 
-	/* Decode mask */
-	frame->masking_key[0] = (buf[mask_start + 0] & 0xff);
-	frame->masking_key[1] = (buf[mask_start + 1] & 0xff);
-	frame->masking_key[2] = (buf[mask_start + 2] & 0xff);
-	frame->masking_key[3] = (buf[mask_start + 3] & 0xff);
-
-	/* Decode and unmask payload */
 	if((unsigned long long)len
 			!= (unsigned long long)frame->payload_len + mask_start + 4) {
 		LM_WARN("message not complete frame size %u but received %u\n",
@@ -492,7 +485,15 @@ static int decode_and_validate_ws_frame(ws_frame_t *frame,
 		*err_text = str_status_message_too_big;
 		return -1;
 	}
+	/* Decode mask */
+	frame->masking_key[0] = (buf[mask_start + 0] & 0xff);
+	frame->masking_key[1] = (buf[mask_start + 1] & 0xff);
+	frame->masking_key[2] = (buf[mask_start + 2] & 0xff);
+	frame->masking_key[3] = (buf[mask_start + 3] & 0xff);
+
 	frame->payload_data = &buf[mask_start + 4];
+
+	/* Decode and unmask payload */
 	for(i = 0; i < frame->payload_len; i++) {
 		j = i % 4;
 		frame->payload_data[i] = frame->payload_data[i] ^ frame->masking_key[j];