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[FFmpeg-devel,1/2] avcodec/pngdec: use 8-bit sBIT cap for indexed PNGs per spec

Message ID 20240719160420.169775-1-leo.izen@gmail.com
State New
Headers show
Series [FFmpeg-devel,1/2] avcodec/pngdec: use 8-bit sBIT cap for indexed PNGs per spec | expand

Commit Message

Leo Izen July 19, 2024, 4:04 p.m. UTC
The PNG specification[1] says that sBIT entries must be at most the bit
depth specified in IHDR, unless the PNG is indexed-color, in which case
sBIT must be between 1 and 8. We should not reject valid sBITs on PNGs
with indexed color.

[1]: https://www.w3.org/TR/png-3/#11sBIT

Regression since 84b454935fae2633a8a5dd075e22393f3e8f932f.

Signed-off-by: Leo Izen <leo.izen@gmail.com>
Reported-by: Ramiro Polla <ramiro.polla@gmail.com>
---
 libavcodec/pngdec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Leo Izen July 28, 2024, 8:18 p.m. UTC | #1
On 7/19/24 12:04 PM, Leo Izen wrote:
> The PNG specification[1] says that sBIT entries must be at most the bit
> depth specified in IHDR, unless the PNG is indexed-color, in which case
> sBIT must be between 1 and 8. We should not reject valid sBITs on PNGs
> with indexed color.
> 
> [1]: https://www.w3.org/TR/png-3/#11sBIT
> 
> Regression since 84b454935fae2633a8a5dd075e22393f3e8f932f.
> 
> Signed-off-by: Leo Izen <leo.izen@gmail.com>
> Reported-by: Ramiro Polla <ramiro.polla@gmail.com>
> ---

Will merge soon.

- Leo Izen (Traneptora)
diff mbox series

Patch

diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
index cb861e5f60..c5b32c166d 100644
--- a/libavcodec/pngdec.c
+++ b/libavcodec/pngdec.c
@@ -1097,7 +1097,7 @@  static int decode_sbit_chunk(AVCodecContext *avctx, PNGDecContext *s,
         bits = FFMAX(b, bits);
     }
 
-    if (bits < 0 || bits > s->bit_depth) {
+    if (bits <= 0 || bits > (s->color_type & PNG_COLOR_MASK_PALETTE ? 8 : s->bit_depth)) {
         av_log(avctx, AV_LOG_ERROR, "Invalid significant bits: %d\n", bits);
         return AVERROR_INVALIDDATA;
     }