diff --git a/stb_image.h b/stb_image.h index 5e807a0..d4fd2fc 100644 --- a/stb_image.h +++ b/stb_image.h @@ -4176,6 +4176,7 @@ typedef struct { stbi_uc *zbuffer, *zbuffer_end; int num_bits; + int hit_zeof_once; stbi__uint32 code_buffer; char *zout; @@ -4242,9 +4243,20 @@ stbi_inline static int stbi__zhuffman_decode(stbi__zbuf *a, stbi__zhuffman *z) int b,s; if (a->num_bits < 16) { if (stbi__zeof(a)) { - return -1; /* report error for unexpected end of data. */ + if (!a->hit_zeof_once) { + // This is the first time we hit eof, insert 16 extra padding btis + // to allow us to keep going; if we actually consume any of them + // though, that is invalid data. This is caught later. + a->hit_zeof_once = 1; + a->num_bits += 16; // add 16 implicit zero bits + } else { + // We already inserted our extra 16 padding bits and are again + // out, this stream is actually prematurely terminated. + return -1; + } + } else { + stbi__fill_bits(a); } - stbi__fill_bits(a); } b = z->fast[a->code_buffer & STBI__ZFAST_MASK]; if (b) { @@ -4309,6 +4321,13 @@ static int stbi__parse_huffman_block(stbi__zbuf *a) int len,dist; if (z == 256) { a->zout = zout; + if (a->hit_zeof_once && a->num_bits < 16) { + // The first time we hit zeof, we inserted 16 extra zero bits into our bit + // buffer so the decoder can just do its speculative decoding. But if we + // actually consumed any of those bits (which is the case when num_bits < 16), + // the stream actually read past the end so it is malformed. + return stbi__err("unexpected end","Corrupt PNG"); + } return 1; } if (z >= 286) return stbi__err("bad huffman code","Corrupt PNG"); // per DEFLATE, length codes 286 and 287 must not appear in compressed data @@ -4320,7 +4339,7 @@ static int stbi__parse_huffman_block(stbi__zbuf *a) dist = stbi__zdist_base[z]; if (stbi__zdist_extra[z]) dist += stbi__zreceive(a, stbi__zdist_extra[z]); if (zout - a->zout_start < dist) return stbi__err("bad dist","Corrupt PNG"); - if (zout + len > a->zout_end) { + if (len > a->zout_end - zout) { if (!stbi__zexpand(a, zout, len)) return 0; zout = a->zout; } @@ -4464,6 +4483,7 @@ static int stbi__parse_zlib(stbi__zbuf *a, int parse_header) if (!stbi__parse_zlib_header(a)) return 0; a->num_bits = 0; a->code_buffer = 0; + a->hit_zeof_once = 0; do { final = stbi__zreceive(a,1); type = stbi__zreceive(a,2);