diff --git a/stb_image.h b/stb_image.h index 800c83d..9d10099 100644 --- a/stb_image.h +++ b/stb_image.h @@ -1063,6 +1063,23 @@ static void *stbi__malloc_mad4(int a, int b, int c, int d, int add) } #endif +// returns 1 if the sum of two signed ints is valid (between -2^31 and 2^31-1 inclusive), 0 on overflow. +static int stbi__addints_valid(int a, int b) +{ + if ((a >= 0) != (b >= 0)) return 1; // a and b have different signs, so no overflow + if (a < 0 && b < 0) return a >= INT_MIN - b; // same as a + b >= INT_MIN; INT_MIN - b cannot overflow since b < 0. + return a <= INT_MAX - b; +} + +// returns 1 if the product of two signed shorts is valid, 0 on overflow. +static int stbi__mul2shorts_valid(short a, short b) +{ + if (b == 0 || b == -1) return 1; // multiplication by 0 is always 0; check for -1 so SHRT_MIN/b doesn't overflow + if ((a >= 0) == (b >= 0)) return a <= SHRT_MAX/b; // product is positive, so similar to mul2sizes_valid + if (b < 0) return a <= SHRT_MIN / b; // same as a * b >= SHRT_MIN + return a >= SHRT_MIN / b; +} + // stbi__err - error // stbi__errpf - error returning pointer to float // stbi__errpuc - error returning pointer to unsigned char @@ -2135,6 +2152,7 @@ stbi_inline static int stbi__extend_receive(stbi__jpeg *j, int n) unsigned int k; int sgn; if (j->code_bits < n) stbi__grow_buffer_unsafe(j); + if (j->code_bits < n) return 0; // ran out of bits from stream, return 0s intead of continuing sgn = j->code_buffer >> 31; // sign bit always in MSB; 0 if MSB clear (positive), 1 if MSB set (negative) k = stbi_lrot(j->code_buffer, n); @@ -2149,6 +2167,7 @@ stbi_inline static int stbi__jpeg_get_bits(stbi__jpeg *j, int n) { unsigned int k; if (j->code_bits < n) stbi__grow_buffer_unsafe(j); + if (j->code_bits < n) return 0; // ran out of bits from stream, return 0s intead of continuing k = stbi_lrot(j->code_buffer, n); j->code_buffer = k & ~stbi__bmask[n]; k &= stbi__bmask[n]; @@ -2160,6 +2179,7 @@ stbi_inline static int stbi__jpeg_get_bit(stbi__jpeg *j) { unsigned int k; if (j->code_bits < 1) stbi__grow_buffer_unsafe(j); + if (j->code_bits < 1) return 0; // ran out of bits from stream, return 0s intead of continuing k = j->code_buffer; j->code_buffer <<= 1; --j->code_bits; @@ -2197,8 +2217,10 @@ static int stbi__jpeg_decode_block(stbi__jpeg *j, short data[64], stbi__huffman memset(data,0,64*sizeof(data[0])); diff = t ? stbi__extend_receive(j, t) : 0; + if (!stbi__addints_valid(j->img_comp[b].dc_pred, diff)) return stbi__err("bad delta","Corrupt JPEG"); dc = j->img_comp[b].dc_pred + diff; j->img_comp[b].dc_pred = dc; + if (!stbi__mul2shorts_valid(dc, dequant[0])) return stbi__err("can't merge dc and ac", "Corrupt JPEG"); data[0] = (short) (dc * dequant[0]); // decode AC components, see JPEG spec @@ -2212,6 +2234,7 @@ static int stbi__jpeg_decode_block(stbi__jpeg *j, short data[64], stbi__huffman if (r) { // fast-AC path k += (r >> 4) & 15; // run s = r & 15; // combined length + if (s > j->code_bits) return stbi__err("bad huffman code", "Combined length longer than code bits available"); j->code_buffer <<= s; j->code_bits -= s; // decode into unzigzag'd location @@ -2251,8 +2274,10 @@ static int stbi__jpeg_decode_block_prog_dc(stbi__jpeg *j, short data[64], stbi__ if (t < 0 || t > 15) return stbi__err("can't merge dc and ac", "Corrupt JPEG"); diff = t ? stbi__extend_receive(j, t) : 0; + if (!stbi__addints_valid(j->img_comp[b].dc_pred, diff)) return stbi__err("bad delta", "Corrupt JPEG"); dc = j->img_comp[b].dc_pred + diff; j->img_comp[b].dc_pred = dc; + if (!stbi__mul2shorts_valid(dc, 1 << j->succ_low)) return stbi__err("can't merge dc and ac", "Corrupt JPEG"); data[0] = (short) (dc * (1 << j->succ_low)); } else { // refinement scan for DC coefficient @@ -2287,8 +2312,8 @@ static int stbi__jpeg_decode_block_prog_ac(stbi__jpeg *j, short data[64], stbi__ if (r) { // fast-AC path k += (r >> 4) & 15; // run s = r & 15; // combined length + if (s > j->code_bits) return stbi__err("bad huffman code", "Combined length longer than code bits available"); j->code_buffer <<= s; - if (s > j->code_bits) return stbi__err("bad huffman code","Combined length longer than code bits available"); j->code_bits -= s; zig = stbi__jpeg_dezigzag[k++]; data[zig] = (short) ((r >> 8) * (1 << shift));