[FFmpeg-devel] [PATCH 1/4] aacdec_usac: prevent get_bits(0) in get_escaped_value

[FFmpeg-devel] [PATCH 1/4] aacdec_usac: prevent get_bits(0) in get_escaped_value

[Lynne via ffmpeg-devel]

Some calls to get_escaped_value() specify 0 bits as the third value.
This would result in get_bits(0), which is not a correct usage of the
get_bits API.
---
 libavcodec/aac/aacdec_usac.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/aac/aacdec_usac.c b/libavcodec/aac/aacdec_usac.c
index 00ec74718b..d98c014cf8 100644
--- a/libavcodec/aac/aacdec_usac.c
+++ b/libavcodec/aac/aacdec_usac.c
@@ -38,7 +38,7 @@ static inline uint32_t get_escaped_value(GetBitContext *gb, int nb1, int nb2, in
         return val;
 
     val += val2 = get_bits(gb, nb2);
-    if (val2 == ((1 << nb2) - 1))
+    if (nb3 && (val2 == ((1 << nb2) - 1)))
         val += get_bits(gb, nb3);
 
     return val;
-- 
2.43.0.381.gb435a96ce8
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[FFmpeg-devel] [PATCH 2/4] aacdec_usac: error out on too many elements

[Lynne via ffmpeg-devel]

USAC supports up to 64 audio channels, but puts no limit on the total
number of extensions that may be present. Which may mean that there's
a single audio channel, with 65 thousand extension elements.

We assume that 64 elements is the maximum for now. So check the value.
---
 libavcodec/aac/aacdec_usac.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libavcodec/aac/aacdec_usac.c b/libavcodec/aac/aacdec_usac.c
index d98c014cf8..af3df3b449 100644
--- a/libavcodec/aac/aacdec_usac.c
+++ b/libavcodec/aac/aacdec_usac.c
@@ -393,6 +393,11 @@ int ff_aac_usac_config_decode(AACDecContext *ac, AVCodecContext *avctx,
     /* UsacDecoderConfig */
     elem_id[0] = elem_id[1] = elem_id[2] = 0;
     usac->nb_elems = get_escaped_value(gb, 4, 8, 16) + 1;
+    if (usac->nb_elems > 64) {
+        av_log(ac->avctx, AV_LOG_ERROR, "Too many elements: %i\n",
+               usac->nb_elems);
+        return AVERROR(EINVAL);
+    }
 
     for (int i = 0; i < usac->nb_elems; i++) {
         AACUsacElemConfig *e = &usac->elems[i];
-- 
2.43.0.381.gb435a96ce8
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[FFmpeg-devel] [PATCH 3/4] aacdec_usac: error out on receiving too many channels for the current layout

[Lynne via ffmpeg-devel]

Verify that we have a correct number of channels.
---
 libavcodec/aac/aacdec_usac.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/libavcodec/aac/aacdec_usac.c b/libavcodec/aac/aacdec_usac.c
index af3df3b449..0d5eb59de5 100644
--- a/libavcodec/aac/aacdec_usac.c
+++ b/libavcodec/aac/aacdec_usac.c
@@ -311,7 +311,7 @@ int ff_aac_usac_config_decode(AACDecContext *ac, AVCodecContext *avctx,
     int ret, idx;
     uint8_t freq_idx;
     uint8_t channel_config_idx;
-    int nb_elements;
+    int nb_channels = 0;
     int samplerate;
     int sbr_ratio;
     MPEG4AudioConfig *m4ac = &oc->m4ac;
@@ -358,7 +358,7 @@ int ff_aac_usac_config_decode(AACDecContext *ac, AVCodecContext *avctx,
     channel_config_idx = get_bits(gb, 5); /* channelConfigurationIndex */
     if (!channel_config_idx) {
         /* UsacChannelConfig() */
-        uint8_t nb_channels = get_escaped_value(gb, 5, 8, 16); /* numOutChannels */
+        nb_channels = get_escaped_value(gb, 5, 8, 16); /* numOutChannels */
         if (nb_channels >= 64)
             return AVERROR(EINVAL);
 
@@ -385,9 +385,14 @@ int ff_aac_usac_config_decode(AACDecContext *ac, AVCodecContext *avctx,
         if (ret < 0)
             return ret;
     } else {
+        int nb_elements;
         if ((ret = ff_aac_set_default_channel_config(ac, avctx, layout_map,
                                                      &nb_elements, channel_config_idx)))
             return ret;
+
+        /* Fill in the number of expected channels */
+        for (int i = 0; i < nb_elements; i++)
+            nb_channels += layout_map[i][0] == TYPE_CPE ? 2 : 1;
     }
 
     /* UsacDecoderConfig */
@@ -404,6 +409,13 @@ int ff_aac_usac_config_decode(AACDecContext *ac, AVCodecContext *avctx,
         memset(e, 0, sizeof(*e));
 
         e->type = get_bits(gb, 2); /* usacElementType */
+        if (e->type != ID_USAC_EXT &&
+            elem_id[0] + elem_id[1] + elem_id[2] + 1 > nb_channels) {
+            av_log(ac->avctx, AV_LOG_ERROR, "Too many channels for the channel "
+                                            "configuration\n");
+            return AVERROR(EINVAL);
+        }
+
         av_log(ac->avctx, AV_LOG_DEBUG, "Element present: idx %i, type %i\n",
                i, e->type);
 
-- 
2.43.0.381.gb435a96ce8
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[FFmpeg-devel] [PATCH 4/4] aacdec_usac: fix off by one error check on channel numbers

[Lynne via ffmpeg-devel]

---
 libavcodec/aac/aacdec_usac.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/aac/aacdec_usac.c b/libavcodec/aac/aacdec_usac.c
index 0d5eb59de5..80c6ab4e65 100644
--- a/libavcodec/aac/aacdec_usac.c
+++ b/libavcodec/aac/aacdec_usac.c
@@ -359,7 +359,7 @@ int ff_aac_usac_config_decode(AACDecContext *ac, AVCodecContext *avctx,
     if (!channel_config_idx) {
         /* UsacChannelConfig() */
         nb_channels = get_escaped_value(gb, 5, 8, 16); /* numOutChannels */
-        if (nb_channels >= 64)
+        if (nb_channels > 64)
             return AVERROR(EINVAL);
 
         av_channel_layout_uninit(&ac->oc[1].ch_layout);
-- 
2.43.0.381.gb435a96ce8
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