From 1d0aec2ee28e889a64d78f2b09d1bd7e2ffaa66e Mon Sep 17 00:00:00 2001 From: Vincent Rabaud Date: Thu, 7 Sep 2023 21:16:03 +0200 Subject: [PATCH] [libwebp] Fix OOB write in BuildHuffmanTable. First, BuildHuffmanTable is called to check if the data is valid. If it is and the table is not big enough, more memory is allocated. This will make sure that valid (but unoptimized because of unbalanced codes) streams are still decodable. Bug: chromium:1479274 Change-Id: I31c36dbf3aa78d35ecf38706b50464fd3d375741 --- media/libwebp/src/dec/vp8l_dec.c | 54 +++++++-------- media/libwebp/src/dec/vp8li_dec.h | 2 +- media/libwebp/src/utils/huffman_utils.c | 91 +++++++++++++++++++++---- media/libwebp/src/utils/huffman_utils.h | 25 ++++++- 4 files changed, 127 insertions(+), 45 deletions(-) diff --git a/media/libwebp/src/dec/vp8l_dec.c b/media/libwebp/src/dec/vp8l_dec.c index 333bb3e80..4948738cf 100644 --- a/media/libwebp/src/dec/vp8l_dec.c +++ b/media/libwebp/src/dec/vp8l_dec.c @@ -253,11 +253,11 @@ static int ReadHuffmanCodeLengths( int symbol; int max_symbol; int prev_code_len = DEFAULT_CODE_LENGTH; - HuffmanCode table[1 << LENGTHS_TABLE_BITS]; + HuffmanTables tables; - if (!VP8LBuildHuffmanTable(table, LENGTHS_TABLE_BITS, - code_length_code_lengths, - NUM_CODE_LENGTH_CODES)) { + if (!VP8LHuffmanTablesAllocate(1 << LENGTHS_TABLE_BITS, &tables) || + !VP8LBuildHuffmanTable(&tables, LENGTHS_TABLE_BITS, + code_length_code_lengths, NUM_CODE_LENGTH_CODES)) { goto End; } @@ -277,7 +277,7 @@ static int ReadHuffmanCodeLengths( int code_len; if (max_symbol-- == 0) break; VP8LFillBitWindow(br); - p = &table[VP8LPrefetchBits(br) & LENGTHS_TABLE_MASK]; + p = &tables.curr_segment->start[VP8LPrefetchBits(br) & LENGTHS_TABLE_MASK]; VP8LSetBitPos(br, br->bit_pos_ + p->bits); code_len = p->value; if (code_len < kCodeLengthLiterals) { @@ -300,6 +300,7 @@ static int ReadHuffmanCodeLengths( ok = 1; End: + VP8LHuffmanTablesDeallocate(&tables); if (!ok) dec->status_ = VP8_STATUS_BITSTREAM_ERROR; return ok; } @@ -307,7 +308,8 @@ static int ReadHuffmanCodeLengths( // 'code_lengths' is pre-allocated temporary buffer, used for creating Huffman // tree. static int ReadHuffmanCode(int alphabet_size, VP8LDecoder* const dec, - int* const code_lengths, HuffmanCode* const table) { + int* const code_lengths, + HuffmanTables* const table) { int ok = 0; int size = 0; VP8LBitReader* const br = &dec->br_; @@ -365,8 +367,7 @@ static int ReadHuffmanCodes(VP8LDecoder* const dec, int xsize, int ysize, // When reading htrees, some might be unused, as the format allows it. // We will still read them but put them in this htree_group_bogus. HTreeGroup htree_group_bogus; - HuffmanCode* huffman_tables = NULL; - HuffmanCode* huffman_tables_bogus = NULL; + HuffmanTables* huffman_tables = &hdr->huffman_tables_; HuffmanCode* next = NULL; int num_htree_groups = 1; int num_htree_groups_max = 1; @@ -376,6 +377,10 @@ static int ReadHuffmanCodes(VP8LDecoder* const dec, int xsize, int ysize, int* mapping = NULL; int ok = 0; + // Check the table has been 0 initialized (through InitMetadata). + assert(huffman_tables->root.start == NULL); + assert(huffman_tables->curr_segment == NULL); + if (allow_recursion && VP8LReadBits(br, 1)) { // use meta Huffman codes. const int huffman_precision = VP8LReadBits(br, 3) + 2; @@ -418,12 +423,6 @@ static int ReadHuffmanCodes(VP8LDecoder* const dec, int xsize, int ysize, if (*mapped_group == -1) *mapped_group = num_htree_groups++; huffman_image[i] = *mapped_group; } - huffman_tables_bogus = (HuffmanCode*)WebPSafeMalloc( - table_size, sizeof(*huffman_tables_bogus)); - if (huffman_tables_bogus == NULL) { - dec->status_ = VP8_STATUS_OUT_OF_MEMORY; - goto Error; - } } else { num_htree_groups = num_htree_groups_max; } @@ -444,16 +443,15 @@ static int ReadHuffmanCodes(VP8LDecoder* const dec, int xsize, int ysize, code_lengths = (int*)WebPSafeCalloc((uint64_t)max_alphabet_size, sizeof(*code_lengths)); - huffman_tables = (HuffmanCode*)WebPSafeMalloc(num_htree_groups * table_size, - sizeof(*huffman_tables)); htree_groups = VP8LHtreeGroupsNew(num_htree_groups); - if (htree_groups == NULL || code_lengths == NULL || huffman_tables == NULL) { + if (htree_groups == NULL || code_lengths == NULL || + !VP8LHuffmanTablesAllocate(num_htree_groups * table_size, + huffman_tables)) { dec->status_ = VP8_STATUS_OUT_OF_MEMORY; goto Error; } - next = huffman_tables; for (i = 0; i < num_htree_groups_max; ++i) { // If the index "i" is unused in the Huffman image, read the coefficients // but store them to a bogus htree_group. @@ -462,27 +460,26 @@ static int ReadHuffmanCodes(VP8LDecoder* const dec, int xsize, int ysize, is_bogus ? &htree_group_bogus : &htree_groups[(mapping == NULL) ? i : mapping[i]]; HuffmanCode** const htrees = htree_group->htrees; - HuffmanCode* huffman_tables_i = is_bogus ? huffman_tables_bogus : next; int size; int total_size = 0; int is_trivial_literal = 1; int max_bits = 0; for (j = 0; j < HUFFMAN_CODES_PER_META_CODE; ++j) { int alphabet_size = kAlphabetSize[j]; - htrees[j] = huffman_tables_i; if (j == 0 && color_cache_bits > 0) { alphabet_size += 1 << color_cache_bits; } size = - ReadHuffmanCode(alphabet_size, dec, code_lengths, huffman_tables_i); + ReadHuffmanCode(alphabet_size, dec, code_lengths, huffman_tables); + htrees[j] = huffman_tables->curr_segment->curr_table; if (size == 0) { goto Error; } if (is_trivial_literal && kLiteralMap[j] == 1) { - is_trivial_literal = (huffman_tables_i->bits == 0); + is_trivial_literal = (htrees[j]->bits == 0); } - total_size += huffman_tables_i->bits; - huffman_tables_i += size; + total_size += htrees[j]->bits; + huffman_tables->curr_segment->curr_table += size; if (j <= ALPHA) { int local_max_bits = code_lengths[0]; int k; @@ -494,7 +491,6 @@ static int ReadHuffmanCodes(VP8LDecoder* const dec, int xsize, int ysize, max_bits += local_max_bits; } } - if (!is_bogus) next = huffman_tables_i; htree_group->is_trivial_literal = is_trivial_literal; htree_group->is_trivial_code = 0; if (is_trivial_literal) { @@ -517,15 +513,13 @@ static int ReadHuffmanCodes(VP8LDecoder* const dec, int xsize, int ysize, hdr->huffman_image_ = huffman_image; hdr->num_htree_groups_ = num_htree_groups; hdr->htree_groups_ = htree_groups; - hdr->huffman_tables_ = huffman_tables; Error: WebPSafeFree(code_lengths); - WebPSafeFree(huffman_tables_bogus); WebPSafeFree(mapping); if (!ok) { WebPSafeFree(huffman_image); - WebPSafeFree(huffman_tables); + VP8LHuffmanTablesDeallocate(huffman_tables); VP8LHtreeGroupsFree(htree_groups); } return ok; @@ -1357,7 +1351,7 @@ static void ClearMetadata(VP8LMetadata* const hdr) { assert(hdr != NULL); WebPSafeFree(hdr->huffman_image_); - WebPSafeFree(hdr->huffman_tables_); + VP8LHuffmanTablesDeallocate(&hdr->huffman_tables_); VP8LHtreeGroupsFree(hdr->htree_groups_); VP8LColorCacheClear(&hdr->color_cache_); VP8LColorCacheClear(&hdr->saved_color_cache_); @@ -1673,7 +1667,7 @@ int VP8LDecodeImage(VP8LDecoder* const dec) { // Sanity checks. if (dec == NULL) return 0; - assert(dec->hdr_.huffman_tables_ != NULL); + assert(dec->hdr_.huffman_tables_.root.start != NULL); assert(dec->hdr_.htree_groups_ != NULL); assert(dec->hdr_.num_htree_groups_ > 0); diff --git a/media/libwebp/src/dec/vp8li_dec.h b/media/libwebp/src/dec/vp8li_dec.h index 0a4d613f9..4677de621 100644 --- a/media/libwebp/src/dec/vp8li_dec.h +++ b/media/libwebp/src/dec/vp8li_dec.h @@ -51,7 +51,7 @@ typedef struct { uint32_t *huffman_image_; int num_htree_groups_; HTreeGroup *htree_groups_; - HuffmanCode *huffman_tables_; + HuffmanTables huffman_tables_; } VP8LMetadata; typedef struct VP8LDecoder VP8LDecoder; diff --git a/media/libwebp/src/utils/huffman_utils.c b/media/libwebp/src/utils/huffman_utils.c index 7a69963c3..fa31898ce 100644 --- a/media/libwebp/src/utils/huffman_utils.c +++ b/media/libwebp/src/utils/huffman_utils.c @@ -172,17 +172,21 @@ static int BuildHuffmanTable(HuffmanCode* const root_table, int root_bits, for (; count[len] > 0; --count[len]) { HuffmanCode code; if ((key & mask) != low) { - table += table_size; + if (root_table != NULL) table += table_size; table_bits = NextTableBitSize(count, len, root_bits); table_size = 1 << table_bits; total_size += table_size; low = key & mask; - root_table[low].bits = (uint8_t)(table_bits + root_bits); - root_table[low].value = (uint16_t)((table - root_table) - low); + if (root_table != NULL) { + root_table[low].bits = (uint8_t)(table_bits + root_bits); + root_table[low].value = (uint16_t)((table - root_table) - low); + } + } + if (root_table != NULL) { + code.bits = (uint8_t)(len - root_bits); + code.value = (uint16_t)sorted[symbol++]; + ReplicateValue(&table[key >> root_bits], step, table_size, code); } - code.bits = (uint8_t)(len - root_bits); - code.value = (uint16_t)sorted[symbol++]; - ReplicateValue(&table[key >> root_bits], step, table_size, code); key = GetNextKey(key, len); } } @@ -202,22 +206,83 @@ static int BuildHuffmanTable(HuffmanCode* const root_table, int root_bits, ((1 << MAX_CACHE_BITS) + NUM_LITERAL_CODES + NUM_LENGTH_CODES) // Cut-off value for switching between heap and stack allocation. #define SORTED_SIZE_CUTOFF 512 -int VP8LBuildHuffmanTable(HuffmanCode* const root_table, int root_bits, +int VP8LBuildHuffmanTable(HuffmanTables* const root_table, int root_bits, const int code_lengths[], int code_lengths_size) { - int total_size; + const int total_size = + BuildHuffmanTable(NULL, root_bits, code_lengths, code_lengths_size, NULL); assert(code_lengths_size <= MAX_CODE_LENGTHS_SIZE); + if (total_size == 0 || root_table == NULL) return total_size; + + if (root_table->curr_segment->curr_table + total_size >= + root_table->curr_segment->start + root_table->curr_segment->size) { + // If 'root_table' does not have enough memory, allocate a new segment. + // The available part of root_table->curr_segment is left unused because we + // need a contiguous buffer. + const int segment_size = root_table->curr_segment->size; + struct HuffmanTablesSegment* next = + (HuffmanTablesSegment*)WebPSafeMalloc(1, sizeof(*next)); + if (next == NULL) return 0; + // Fill the new segment. + // We need at least 'total_size' but if that value is small, it is better to + // allocate a big chunk to prevent more allocations later. 'segment_size' is + // therefore chosen (any other arbitrary value could be chosen). + next->size = total_size > segment_size ? total_size : segment_size; + next->start = + (HuffmanCode*)WebPSafeMalloc(next->size, sizeof(*next->start)); + if (next->start == NULL) { + WebPSafeFree(next); + return 0; + } + next->curr_table = next->start; + next->next = NULL; + // Point to the new segment. + root_table->curr_segment->next = next; + root_table->curr_segment = next; + } if (code_lengths_size <= SORTED_SIZE_CUTOFF) { // use local stack-allocated array. uint16_t sorted[SORTED_SIZE_CUTOFF]; - total_size = BuildHuffmanTable(root_table, root_bits, - code_lengths, code_lengths_size, sorted); - } else { // rare case. Use heap allocation. + BuildHuffmanTable(root_table->curr_segment->curr_table, root_bits, + code_lengths, code_lengths_size, sorted); + } else { // rare case. Use heap allocation. uint16_t* const sorted = (uint16_t*)WebPSafeMalloc(code_lengths_size, sizeof(*sorted)); if (sorted == NULL) return 0; - total_size = BuildHuffmanTable(root_table, root_bits, - code_lengths, code_lengths_size, sorted); + BuildHuffmanTable(root_table->curr_segment->curr_table, root_bits, + code_lengths, code_lengths_size, sorted); WebPSafeFree(sorted); } return total_size; } + +int VP8LHuffmanTablesAllocate(int size, HuffmanTables* huffman_tables) { + // Have 'segment' point to the first segment for now, 'root'. + HuffmanTablesSegment* const root = &huffman_tables->root; + huffman_tables->curr_segment = root; + // Allocate root. + root->start = (HuffmanCode*)WebPSafeMalloc(size, sizeof(*root->start)); + if (root->start == NULL) return 0; + root->curr_table = root->start; + root->next = NULL; + root->size = size; + return 1; +} + +void VP8LHuffmanTablesDeallocate(HuffmanTables* const huffman_tables) { + HuffmanTablesSegment *current, *next; + if (huffman_tables == NULL) return; + // Free the root node. + current = &huffman_tables->root; + next = current->next; + WebPSafeFree(current->start); + current->start = NULL; + current->next = NULL; + current = next; + // Free the following nodes. + while (current != NULL) { + next = current->next; + WebPSafeFree(current->start); + WebPSafeFree(current); + current = next; + } +} diff --git a/media/libwebp/src/utils/huffman_utils.h b/media/libwebp/src/utils/huffman_utils.h index ff7ef17f3..98415c532 100644 --- a/media/libwebp/src/utils/huffman_utils.h +++ b/media/libwebp/src/utils/huffman_utils.h @@ -43,6 +43,29 @@ typedef struct { // or non-literal symbol otherwise } HuffmanCode32; +// Contiguous memory segment of HuffmanCodes. +typedef struct HuffmanTablesSegment { + HuffmanCode* start; + // Pointer to where we are writing into the segment. Starts at 'start' and + // cannot go beyond 'start' + 'size'. + HuffmanCode* curr_table; + // Pointer to the next segment in the chain. + struct HuffmanTablesSegment* next; + int size; +} HuffmanTablesSegment; + +// Chained memory segments of HuffmanCodes. +typedef struct HuffmanTables { + HuffmanTablesSegment root; + // Currently processed segment. At first, this is 'root'. + HuffmanTablesSegment* curr_segment; +} HuffmanTables; + +// Allocates a HuffmanTables with 'size' contiguous HuffmanCodes. Returns 0 on +// memory allocation error, 1 otherwise. +int VP8LHuffmanTablesAllocate(int size, HuffmanTables* huffman_tables); +void VP8LHuffmanTablesDeallocate(HuffmanTables* const huffman_tables); + #define HUFFMAN_PACKED_BITS 6 #define HUFFMAN_PACKED_TABLE_SIZE (1u << HUFFMAN_PACKED_BITS) @@ -78,7 +101,7 @@ void VP8LHtreeGroupsFree(HTreeGroup* const htree_groups); // the huffman table. // Returns built table size or 0 in case of error (invalid tree or // memory error). -int VP8LBuildHuffmanTable(HuffmanCode* const root_table, int root_bits, +int VP8LBuildHuffmanTable(HuffmanTables* const root_table, int root_bits, const int code_lengths[], int code_lengths_size); #ifdef __cplusplus