ref: 466b01d504d7e45f1e9169ac90b3e34ab94aed14
parent: 7da4a83b230d069a9d731b1e64f6e6b52802576a
author: Hugo Lefeuvre <hle@debian.org>
date: Mon Feb 25 05:49:03 EST 2019
syntax.c: check for syntax element inconsistencies Implicit channel mapping reconfiguration is explicitely forbidden by ISO/IEC 13818-7:2006 (8.5.3.3). Decoders should be able to detect such files and reject them. FAAD2 does not perform any kind of checks regarding this. This leads to security vulnerabilities when processing crafted AAC files performing such reconfigurations. Add checks to decode_sce_lfe and decode_cpe to make sure such inconsistencies are detected as early as possible. These checks first read hDecoder->frame: if this is not the first frame then we make sure that the syntax element at the same position in the previous frame also had element_id id_syn_ele. If not, return 21 as this is a fatal file structure issue. This patch addresses CVE-2018-20362 (fixes #26) and possibly other related issues.
--- a/libfaad/syntax.c
+++ b/libfaad/syntax.c
@@ -344,6 +344,12 @@
can become 2 when some form of Parametric Stereo coding is used
*/
+ if (hDecoder->frame && hDecoder->element_id[hDecoder->fr_ch_ele] != id_syn_ele) {+ /* element inconsistency */
+ hInfo->error = 21;
+ return;
+ }
+
/* save the syntax element id */
hDecoder->element_id[hDecoder->fr_ch_ele] = id_syn_ele;
@@ -390,6 +396,12 @@
/* element_output_channels not set yet */
hDecoder->element_output_channels[hDecoder->fr_ch_ele] = 2;
} else if (hDecoder->element_output_channels[hDecoder->fr_ch_ele] != 2) {+ /* element inconsistency */
+ hInfo->error = 21;
+ return;
+ }
+
+ if (hDecoder->frame && hDecoder->element_id[hDecoder->fr_ch_ele] != id_syn_ele) {/* element inconsistency */
hInfo->error = 21;
return;