From 4b5a0e1932104adb25132d31bf84f1caf621d8bc Mon Sep 17 00:00:00 2001
From: Matthew Jordan <mjordan@digium.com>
Date: Wed, 27 Mar 2013 14:28:36 +0000
Subject: [PATCH] AST-2013-001: Prevent buffer overflow through H.264 format
negotiation
The format attribute resource for H.264 video performs an unsafe read against a
media attribute when parsing the SDP. The value passed in with the format
attribute is not checked for its length when parsed into a fixed length buffer.
This patch resolves the vulnerability by only reading as many characters from
the SDP value as will fit into the buffer.
(closes issue ASTERISK-20901)
Reported by: Ulf Harnhammar
patches:
h264_overflow_security_patch.diff uploaded by jrose (License 6182)
........
Merged revisions 383973 from http://svn.asterisk.org/svn/asterisk/branches/11
git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@383975 65c4cc65-6c06-0410-ace0-fbb531ad65f3
---
res/res_format_attr_h264.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/res/res_format_attr_h264.c b/res/res_format_attr_h264.c
index 9642c51f1a..eae1aa36ef 100644
--- a/res/res_format_attr_h264.c
+++ b/res/res_format_attr_h264.c
@@ -41,8 +41,14 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
/*! \brief Value that indicates an attribute is actually unset */
#define H264_ATTR_KEY_UNSET UINT8_MAX
-/*! \brief Maximum size for SPS / PPS values in sprop-parameter-sets attribute */
+/*! \brief Maximum size for SPS / PPS values in sprop-parameter-sets attribute
+ * if you change this value then you must change H264_MAX_SPS_PPS_SIZE_SCAN_LIMIT
+ * as well. */
#define H264_MAX_SPS_PPS_SIZE 16
+/*! \brief This is used when executing sscanf on buffers of H264_MAX_SPS_PPS_SIZE
+ * length. It must ALWAYS be a string literal representation of one less than
+ * H264_MAX_SPS_PPS_SIZE */
+#define H264_MAX_SPS_PPS_SIZE_SCAN_LIMIT "15"
enum h264_attr_keys {
H264_ATTR_KEY_PROFILE_IDC,
@@ -111,7 +117,8 @@ static int h264_format_attr_sdp_parse(struct ast_format_attr *format_attr, const
format_attr->format_attr[H264_ATTR_KEY_PROFILE_IDC] = ((val2 >> 16) & 0xFF);
format_attr->format_attr[H264_ATTR_KEY_PROFILE_IOP] = ((val2 >> 8) & 0xFF);
format_attr->format_attr[H264_ATTR_KEY_LEVEL] = (val2 & 0xFF);
- } else if (sscanf(attrib, "sprop-parameter-sets=%[^','],%s", sps, pps) == 2) {
+ } else if (sscanf(attrib, "sprop-parameter-sets=%" H264_MAX_SPS_PPS_SIZE_SCAN_LIMIT "[^','],%" H264_MAX_SPS_PPS_SIZE_SCAN_LIMIT "s", sps, pps) == 2) {
+ /* XXX sprop-parameter-sets can actually be of unlimited length. This may need to be addressed later. */
unsigned char spsdecoded[H264_MAX_SPS_PPS_SIZE] = { 0, }, ppsdecoded[H264_MAX_SPS_PPS_SIZE] = { 0, };
int i;
--
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