[FFmpeg-cvslog] Fix movtext crashes caused due to lack of proper bounds checking
Niklesh
git at videolan.org
Wed May 20 05:35:58 CEST 2015
ffmpeg | branch: master | Niklesh <niklesh.lalwani at iitb.ac.in> | Tue May 19 18:40:55 2015 +0530| [b44a55ad2d182dc5dce09609badfb6dcb575e632] | committer: Philip Langdale
Fix movtext crashes caused due to lack of proper bounds checking
Signed-off-by: Niklesh <niklesh.lalwani at iitb.ac.in>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b44a55ad2d182dc5dce09609badfb6dcb575e632
---
libavcodec/movtextdec.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/libavcodec/movtextdec.c b/libavcodec/movtextdec.c
index 3059599..53ffef0 100644
--- a/libavcodec/movtextdec.c
+++ b/libavcodec/movtextdec.c
@@ -96,7 +96,7 @@ static int mov_text_decode_frame(AVCodecContext *avctx,
char *ptr = avpkt->data;
char *end;
//char *ptr_temp;
- int text_length, tsmb_type, style_entries, tsmb_size;
+ int text_length, tsmb_type, style_entries, tsmb_size, tracksize;
int **style_start = {0,};
int **style_end = {0,};
int **style_flags = {0,};
@@ -135,20 +135,31 @@ static int mov_text_decode_frame(AVCodecContext *avctx,
(AVRational){1,100});
tsmb_size = 0;
+ tracksize = 2 + text_length;
// Note that the spec recommends lines be no longer than 2048 characters.
av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
if (text_length + 2 != avpkt->size) {
- while (text_length + 2 + tsmb_size < avpkt->size) {
- tsmb = ptr + text_length + tsmb_size;
+ while (tracksize + 8 <= avpkt->size) {
+ // A box is a minimum of 8 bytes.
+ tsmb = ptr + tracksize - 2;
tsmb_size = AV_RB32(tsmb);
tsmb += 4;
tsmb_type = AV_RB32(tsmb);
tsmb += 4;
+ if (tracksize + tsmb_size > avpkt->size)
+ break;
+
if (tsmb_type == MKBETAG('s','t','y','l')) {
+ if (tracksize + 10 > avpkt->size)
+ break;
style_entries = AV_RB16(tsmb);
tsmb += 2;
+ // A single style record is of length 12 bytes.
+ if (tracksize + 10 + style_entries * 12 > avpkt->size)
+ break;
+
for(i = 0; i < style_entries; i++) {
style_pos = av_malloc(4);
*style_pos = AV_RB16(tsmb);
@@ -176,6 +187,7 @@ static int mov_text_decode_frame(AVCodecContext *avctx,
av_freep(&style_end);
av_freep(&style_flags);
}
+ tracksize = tracksize + tsmb_size;
}
} else
text_to_ass(&buf, ptr, end, NULL, NULL, 0, 0);
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