Patch v2, now handles more malformed cases. Original patch was for a file for which I had a sample from a user but this allows handling some manually broken test cases.

On 25.9.2014 21:53, Janne Hyvärinen wrote:
Here's a patch to allow flac and metaflac handle files with malformed vorbiscomment metadata block.


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diff --git a/src/libFLAC/metadata_iterators.c b/src/libFLAC/metadata_iterators.c
index d50df39..cba864c 100644
--- a/src/libFLAC/metadata_iterators.c
+++ b/src/libFLAC/metadata_iterators.c
@@ -77,8 +77,8 @@ static FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_streaminfo_c
 static FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_padding_cb_(FLAC__IOHandle handle, 
FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata_Padding *block, unsigned 
block_length);
 static FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_application_cb_(FLAC__IOHandle handle, 
FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Application *block, 
unsigned block_length);
 static FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_seektable_cb_(FLAC__IOHandle handle, 
FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_SeekTable *block, unsigned 
block_length);
-static FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_vorbis_comment_entry_cb_(FLAC__IOHandle handle, 
FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_VorbisComment_Entry *entry);
-static FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, 
FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_VorbisComment *block);
+static FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_vorbis_comment_entry_cb_(FLAC__IOHandle handle, 
FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_VorbisComment_Entry *entry, 
unsigned max_length);
+static FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, 
FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, 
FLAC__StreamMetadata_VorbisComment *block, unsigned block_length);
 static FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_cuesheet_track_cb_(FLAC__IOHandle handle, 
FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_CueSheet_Track *track);
 static FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_cuesheet_cb_(FLAC__IOHandle handle, 
FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_CueSheet *block);
 static FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_picture_cb_(FLAC__IOHandle handle, 
FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Picture *block);
@@ -2091,7 +2091,7 @@ FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_cb_(FLAC__IOHandle
                case FLAC__METADATA_TYPE_SEEKTABLE:
                        return read_metadata_block_data_seektable_cb_(handle, 
read_cb, &block->data.seek_table, block->length);
                case FLAC__METADATA_TYPE_VORBIS_COMMENT:
-                       return 
read_metadata_block_data_vorbis_comment_cb_(handle, read_cb, 
&block->data.vorbis_comment);
+                       return 
read_metadata_block_data_vorbis_comment_cb_(handle, read_cb, seek_cb, 
&block->data.vorbis_comment, block->length);
                case FLAC__METADATA_TYPE_CUESHEET:
                        return read_metadata_block_data_cuesheet_cb_(handle, 
read_cb, &block->data.cue_sheet);
                case FLAC__METADATA_TYPE_PICTURE:
@@ -2189,16 +2189,21 @@ FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_seektable_cb_(FLAC_
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
 }
 
-FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_vorbis_comment_entry_cb_(FLAC__IOHandle handle, 
FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_VorbisComment_Entry *entry)
+FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_vorbis_comment_entry_cb_(FLAC__IOHandle handle, 
FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_VorbisComment_Entry *entry, 
unsigned max_length)
 {
        const unsigned entry_length_len = 
FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN / 8;
        FLAC__byte buffer[4]; /* magic number is asserted below */
 
        FLAC__ASSERT(FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN / 8 
== sizeof(buffer));
 
+       if(max_length < entry_length_len) return 
FLAC__METADATA_CHAIN_STATUS_BAD_METADATA; else max_length -= entry_length_len;
        if(read_cb(buffer, 1, entry_length_len, handle) != entry_length_len)
                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
        entry->length = unpack_uint32_little_endian_(buffer, entry_length_len);
+       if(max_length < entry->length) {
+               entry->length = 0;
+               return FLAC__METADATA_CHAIN_STATUS_BAD_METADATA;
+       } else max_length -= entry->length;
 
        if(0 != entry->entry)
                free(entry->entry);
@@ -2219,7 +2224,7 @@ FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_vorbis_comment_entr
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
 }
 
-FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, 
FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_VorbisComment *block)
+FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, 
FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, 
FLAC__StreamMetadata_VorbisComment *block, unsigned block_length)
 {
        unsigned i;
        FLAC__Metadata_SimpleIteratorStatus status;
@@ -2228,9 +2233,13 @@ FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_vorbis_comment_cb_(
 
        FLAC__ASSERT(FLAC__STREAM_METADATA_VORBIS_COMMENT_NUM_COMMENTS_LEN / 8 
== sizeof(buffer));
 
-       if(FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK != (status = 
read_metadata_block_data_vorbis_comment_entry_cb_(handle, read_cb, 
&(block->vendor_string))))
-               return status;
+       status = read_metadata_block_data_vorbis_comment_entry_cb_(handle, 
read_cb, &(block->vendor_string), block_length);
+       if(block_length >= 4) block_length -= 4;
+       if(status == FLAC__METADATA_CHAIN_STATUS_BAD_METADATA) goto skip;
+       else if(status != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK) return 
status;
+       block_length -= block->vendor_string.length;
 
+       if(block_length < num_comments_len) goto skip; else block_length -= 
num_comments_len;
        if(read_cb(buffer, 1, num_comments_len, handle) != num_comments_len)
                return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
        block->num_comments = unpack_uint32_little_endian_(buffer, 
num_comments_len);
@@ -2242,8 +2251,21 @@ FLAC__Metadata_SimpleIteratorStatus 
read_metadata_block_data_vorbis_comment_cb_(
                return 
FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
 
        for(i = 0; i < block->num_comments; i++) {
-               if(FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK != (status = 
read_metadata_block_data_vorbis_comment_entry_cb_(handle, read_cb, 
block->comments + i)))
-                       return status;
+               status = 
read_metadata_block_data_vorbis_comment_entry_cb_(handle, read_cb, 
block->comments + i, block_length);
+               if(block_length >= 4) block_length -= 4;
+               if(status == FLAC__METADATA_CHAIN_STATUS_BAD_METADATA) {
+                       block->num_comments = i;
+                       goto skip;
+               }
+               else if(status != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK) 
return status;
+               block_length -= block->comments[i].length;
+       }
+
+       skip:
+       if(block_length > 0) {
+               /* bad metadata */
+               if(0 != seek_cb(handle, block_length, SEEK_CUR))
+                       return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
        }
 
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
diff --git a/src/libFLAC/stream_decoder.c b/src/libFLAC/stream_decoder.c
index fac73f3..3c68fd8 100644
--- a/src/libFLAC/stream_decoder.c
+++ b/src/libFLAC/stream_decoder.c
@@ -87,7 +87,7 @@ static FLAC__bool find_metadata_(FLAC__StreamDecoder 
*decoder);
 static FLAC__bool read_metadata_(FLAC__StreamDecoder *decoder);
 static FLAC__bool read_metadata_streaminfo_(FLAC__StreamDecoder *decoder, 
FLAC__bool is_last, unsigned length);
 static FLAC__bool read_metadata_seektable_(FLAC__StreamDecoder *decoder, 
FLAC__bool is_last, unsigned length);
-static FLAC__bool read_metadata_vorbiscomment_(FLAC__StreamDecoder *decoder, 
FLAC__StreamMetadata_VorbisComment *obj);
+static FLAC__bool read_metadata_vorbiscomment_(FLAC__StreamDecoder *decoder, 
FLAC__StreamMetadata_VorbisComment *obj, unsigned length);
 static FLAC__bool read_metadata_cuesheet_(FLAC__StreamDecoder *decoder, 
FLAC__StreamMetadata_CueSheet *obj);
 static FLAC__bool read_metadata_picture_(FLAC__StreamDecoder *decoder, 
FLAC__StreamMetadata_Picture *obj);
 static FLAC__bool skip_id3v2_tag_(FLAC__StreamDecoder *decoder);
@@ -1485,7 +1485,7 @@ FLAC__bool read_metadata_(FLAC__StreamDecoder *decoder)
                                                block.data.application.data = 0;
                                        break;
                                case FLAC__METADATA_TYPE_VORBIS_COMMENT:
-                                       
if(!read_metadata_vorbiscomment_(decoder, &block.data.vorbis_comment))
+                                       
if(!read_metadata_vorbiscomment_(decoder, &block.data.vorbis_comment, 
real_length))
                                                ok = false;
                                        break;
                                case FLAC__METADATA_TYPE_CUESHEET:
@@ -1687,17 +1687,23 @@ FLAC__bool read_metadata_seektable_(FLAC__StreamDecoder 
*decoder, FLAC__bool is_
        return true;
 }
 
-FLAC__bool read_metadata_vorbiscomment_(FLAC__StreamDecoder *decoder, 
FLAC__StreamMetadata_VorbisComment *obj)
+FLAC__bool read_metadata_vorbiscomment_(FLAC__StreamDecoder *decoder, 
FLAC__StreamMetadata_VorbisComment *obj, unsigned length)
 {
        FLAC__uint32 i;
 
        
FLAC__ASSERT(FLAC__bitreader_is_consumed_byte_aligned(decoder->private_->input));
 
+       if(length < 8) goto skip; else length -= 8; /* vendor string length + 
num comments entries alone take 8 bytes */
        /* read vendor string */
        FLAC__ASSERT(FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN == 
32);
        if(!FLAC__bitreader_read_uint32_little_endian(decoder->private_->input, 
&obj->vendor_string.length))
                return false; /* read_callback_ sets the state for us */
        if(obj->vendor_string.length > 0) {
+               if(length < obj->vendor_string.length) {
+                       obj->vendor_string.length = 0;
+                       obj->vendor_string.entry = 0;
+                       goto skip;
+               } else length -= obj->vendor_string.length;
                if(0 == (obj->vendor_string.entry = 
safe_malloc_add_2op_(obj->vendor_string.length, /*+*/1))) {
                        decoder->protected_->state = 
FLAC__STREAM_DECODER_MEMORY_ALLOCATION_ERROR;
                        return false;
@@ -1722,9 +1728,19 @@ FLAC__bool 
read_metadata_vorbiscomment_(FLAC__StreamDecoder *decoder, FLAC__Stre
                }
                for(i = 0; i < obj->num_comments; i++) {
                        
FLAC__ASSERT(FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN == 32);
+                       if(length < 4) {
+                               obj->num_comments = i;
+                               goto skip;
+                       } else length -= 4;
                        
if(!FLAC__bitreader_read_uint32_little_endian(decoder->private_->input, 
&obj->comments[i].length))
                                return false; /* read_callback_ sets the state 
for us */
                        if(obj->comments[i].length > 0) {
+                               if(length < obj->comments[i].length) {
+                                       obj->comments[i].length = 0;
+                                       obj->comments[i].entry = 0;
+                                       obj->num_comments = i;
+                                       goto skip;
+                               } else length -= obj->comments[i].length;
                                if(0 == (obj->comments[i].entry = 
safe_malloc_add_2op_(obj->comments[i].length, /*+*/1))) {
                                        decoder->protected_->state = 
FLAC__STREAM_DECODER_MEMORY_ALLOCATION_ERROR;
                                        return false;
@@ -1741,6 +1757,13 @@ FLAC__bool 
read_metadata_vorbiscomment_(FLAC__StreamDecoder *decoder, FLAC__Stre
                obj->comments = 0;
        }
 
+       skip:
+       if(length > 0) {
+               /* This will only happen on files with invalid data in comments 
*/
+               
if(!FLAC__bitreader_skip_byte_block_aligned_no_crc(decoder->private_->input, 
length))
+                       return false; /* read_callback_ sets the state for us */
+       }
+
        return true;
 }
 
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