449 lines
17 KiB
C
449 lines
17 KiB
C
/*
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* Copyright (C) 2013-2022 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
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* Copyright (C) 2011-2013 Sourcefire, Inc.
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* Copyright (C) 1995-2007 by Alexander Lehmann <lehmann@usa.net>,
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* Andreas Dilger <adilger@enel.ucalgary.ca>,
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* Glenn Randers-Pehrson <randeg@alum.rpi.edu>,
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* Greg Roelofs <newt@pobox.com>,
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* John Bowler <jbowler@acm.org>,
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* Tom Lane <tgl@sss.pgh.pa.us>
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*
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* Initial work derived from pngcheck: http://www.libpng.org/pub/png/apps/pngcheck.html
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*
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* Permission to use, copy, modify, and distribute this software and its
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* documentation for any purpose and without fee is hereby granted, provided
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* that the above copyright notice appear in all copies and that both that
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* copyright notice and this permission notice appear in supporting
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* documentation. This software is provided "as is" without express or
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* implied warranty.
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*
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*/
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#if HAVE_CONFIG_H
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#include "clamav-config.h"
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#endif
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#include <stdio.h>
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#include <stdlib.h>
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#include <ctype.h>
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#include <string.h>
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#include <fcntl.h>
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#include <stdbool.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#ifdef HAVE_UNISTD_H
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#include <unistd.h>
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#endif
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#include <zlib.h>
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#include "clamav.h"
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#include "others.h"
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#include "png.h"
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#include "scanners.h"
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#define PNG_CHUNK_LENGTH_SIZE (4)
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#define PNG_CHUNK_TYPE_SIZE (4)
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#define PNG_CHUNK_CRC_SIZE (4)
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/* Header Size does not include chunk data size */
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#define PNG_CHUNK_HEADER_SIZE (PNG_CHUNK_LENGTH_SIZE + \
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PNG_CHUNK_TYPE_SIZE + \
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PNG_CHUNK_CRC_SIZE)
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#ifndef HAVE_ATTRIB_PACKED
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#define __attribute__(x)
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#endif
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#ifdef HAVE_PRAGMA_PACK
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#pragma pack(1)
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#endif
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#ifdef HAVE_PRAGMA_PACK_HPPA
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#pragma pack 1
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#endif
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typedef struct __attribute__((packed)) {
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uint8_t red;
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uint8_t green;
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uint8_t blue;
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} png_palette_entry;
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#ifdef HAVE_PRAGMA_PACK
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#pragma pack()
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#endif
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#ifdef HAVE_PRAGMA_PACK_HPPA
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#pragma pack
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#endif
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#define BUFFER_SIZE 128000 /* size of read block */
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typedef enum {
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PNG_IDAT_NOT_FOUND_YET,
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PNG_IDAT_DECOMPRESSION_IN_PROGRESS,
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PNG_IDAT_DECOMPRESSION_COMPLETE,
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PNG_IDAT_DECOMPRESSION_FAILED,
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} png_idat_state;
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cl_error_t cli_parsepng(cli_ctx *ctx)
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{
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cl_error_t status = CL_ERROR;
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uint64_t chunk_data_length = 0;
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char chunk_type[5] = {'\0', '\0', '\0', '\0', '\0'};
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uint32_t chunk_crc;
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uint32_t chunk_data_length_u32 = 0;
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bool have_IEND = false;
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bool have_PLTE = false;
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uint64_t zhead = 1; /* 0x10000 indicates both zlib header bytes read */
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int64_t num_chunks = 0;
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uint64_t width = 0;
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uint64_t height = 0;
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uint32_t sample_depth = 0, bit_depth = 0, interlace_method = 0;
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uint64_t num_palette_entries = 0;
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uint32_t color_type = 1;
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uint32_t compression_method = 0;
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uint32_t filter_method = 0;
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uint8_t *ptr = NULL;
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uint64_t offset = 8;
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fmap_t *map = NULL;
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uint64_t image_size = 0;
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int err = Z_OK;
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uint8_t *decompressed_data = NULL;
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bool zstrm_initialized = false;
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z_stream zstrm;
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size_t decompressed_data_len = 0;
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png_idat_state idat_state = PNG_IDAT_NOT_FOUND_YET;
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cli_dbgmsg("in cli_parsepng()\n");
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if (NULL == ctx) {
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cli_dbgmsg("PNG: passed context was NULL\n");
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status = CL_EARG;
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goto done;
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}
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map = ctx->fmap;
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while (fmap_readn(map, (void *)&chunk_data_length_u32, offset, PNG_CHUNK_LENGTH_SIZE) == PNG_CHUNK_LENGTH_SIZE) {
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chunk_data_length = be32_to_host(chunk_data_length_u32);
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offset += PNG_CHUNK_LENGTH_SIZE;
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if (chunk_data_length > (uint64_t)0x7fffffff) {
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cli_dbgmsg("PNG: invalid chunk length (too large): 0x" STDx64 "\n", chunk_data_length);
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if (SCAN_HEURISTIC_BROKEN_MEDIA) {
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cli_append_possibly_unwanted(ctx, "Heuristics.Broken.Media.PNG.InvalidChunkLength");
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status = CL_EPARSE;
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}
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goto scan_overlay;
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}
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if (fmap_readn(map, chunk_type, offset, PNG_CHUNK_TYPE_SIZE) != PNG_CHUNK_TYPE_SIZE) {
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cli_dbgmsg("PNG: EOF while reading chunk type\n");
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if (SCAN_HEURISTIC_BROKEN_MEDIA) {
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cli_append_possibly_unwanted(ctx, "Heuristics.Broken.Media.PNG.EOFReadingChunkType");
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status = CL_EPARSE;
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}
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goto scan_overlay;
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}
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offset += PNG_CHUNK_TYPE_SIZE;
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/* GRR: add 4-character EBCDIC conversion here (chunk_type) */
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chunk_type[4] = '\0';
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++num_chunks;
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cli_dbgmsg("Chunk Type: %s, Data Length: " STDu64 " bytes\n", chunk_type, chunk_data_length);
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if (chunk_data_length > 0) {
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ptr = (uint8_t *)fmap_need_off_once(map, offset, chunk_data_length);
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if (NULL == ptr) {
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cli_warnmsg("PNG: Unexpected early end-of-file.\n");
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if (SCAN_HEURISTIC_BROKEN_MEDIA) {
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cli_append_possibly_unwanted(ctx, "Heuristics.Broken.Media.PNG.EOFReadingChunk");
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status = CL_EPARSE;
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}
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goto scan_overlay;
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}
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offset += chunk_data_length;
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}
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if (strcmp(chunk_type, "IHDR") == 0) {
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/*------*
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| IHDR |
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*------*/
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if (chunk_data_length != 13) {
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cli_dbgmsg("PNG: invalid IHDR length: " STDu64 "\n", chunk_data_length);
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break;
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} else {
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width = be32_to_host(*(uint32_t *)ptr);
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height = be32_to_host(*(uint32_t *)(ptr + 4));
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if (width == 0 || height == 0 || width > (uint64_t)0x7fffffff || height > (uint64_t)0x7fffffff) {
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cli_dbgmsg("PNG: invalid image dimensions: width = " STDu64 ", height = " STDu64 "\n", width, height);
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break;
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}
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sample_depth = bit_depth = (uint32_t)ptr[8];
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color_type = (uint32_t)ptr[9];
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compression_method = (uint32_t)ptr[10];
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filter_method = (uint32_t)ptr[11];
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interlace_method = (uint32_t)ptr[12];
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if (compression_method != 0) {
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cli_dbgmsg("PNG: invalid compression method (%u)\n", compression_method);
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}
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if (filter_method != 0) {
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cli_dbgmsg("PNG: invalid filter method (%u)\n", filter_method);
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}
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switch (bit_depth) {
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case 1:
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case 2:
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case 4:
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if (color_type == 2 || color_type == 4 || color_type == 6) { /* RGB or GA or RGBA */
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cli_dbgmsg("PNG: invalid sample depth (%u)\n", bit_depth);
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break;
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}
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break;
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case 8:
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break;
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case 16:
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if (color_type == 3) { /* palette */
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cli_dbgmsg("PNG: invalid sample depth (%u)\n", bit_depth);
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break;
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}
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break;
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default:
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cli_dbgmsg("PNG: invalid sample depth (%u)\n", bit_depth);
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break;
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}
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switch (color_type) {
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case 2:
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sample_depth = bit_depth * 3; /* RGB */
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break;
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case 4:
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sample_depth = bit_depth * 2; /* gray+alpha */
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break;
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case 6:
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sample_depth = bit_depth * 4; /* RGBA */
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break;
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}
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cli_dbgmsg(" Width: " STDu64 "\n", width);
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cli_dbgmsg(" Height: " STDu64 "\n", height);
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cli_dbgmsg(" Bit Depth: " STDu32 " (Sample Depth: " STDu32 ")\n", bit_depth, sample_depth);
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cli_dbgmsg(" Color Type: " STDu32 "\n", color_type);
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cli_dbgmsg(" Compression Method: " STDu32 "\n", compression_method);
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cli_dbgmsg(" Filter Method: " STDu32 "\n", filter_method);
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cli_dbgmsg(" Interlace Method: " STDu32 "\n", interlace_method);
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}
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} else if (strcmp(chunk_type, "PLTE") == 0) {
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/*------*
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| PLTE |
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*------*/
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if (have_PLTE) {
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cli_dbgmsg("PNG: More than one PTLE chunk found in a PNG file, which is not valid\n");
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}
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if (!(chunk_data_length > sizeof(png_palette_entry) * 256 || chunk_data_length % 3 != 0)) {
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num_palette_entries = chunk_data_length / 3;
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}
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if (color_type == 1) /* for MNG and tRNS */ {
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color_type = 3;
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}
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if (color_type == 0 || color_type == 4) {
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cli_dbgmsg("PNG: PTLE chunk found in a PNG file with color type set to (%u), which is not valid\n", color_type);
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}
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have_PLTE = true;
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cli_dbgmsg(" # palette entries: " STDu64 "\n", num_palette_entries);
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} else if (interlace_method == 0 && strcmp(chunk_type, "IDAT") == 0) {
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/*------*
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| IDAT |
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*------*/
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/*
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* Note from pngcheck:
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* GRR 20000304: data dump not yet compatible with interlaced images.
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*/
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if (idat_state == PNG_IDAT_NOT_FOUND_YET) {
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unsigned zlib_windowbits = 15;
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/* Dump the zlib header from the first two bytes. */
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if (zhead < 0x10000 && chunk_data_length > 0) {
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zhead = (zhead << 8) + ptr[0];
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if (chunk_data_length > 1 && zhead < 0x10000)
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zhead = (zhead << 8) + ptr[1];
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if (zhead >= 0x10000) {
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unsigned int CINFO = (zhead & 0xf000) >> 12;
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zlib_windowbits = CINFO + 8;
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}
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}
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decompressed_data = (uint8_t *)malloc(BUFFER_SIZE);
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if (NULL == decompressed_data) {
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cli_errmsg("Failed to allocation memory for decompressed PNG data.\n");
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goto done;
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}
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/* initialize zlib and bit/byte/line variables if not already done */
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zstrm.zalloc = (alloc_func)Z_NULL;
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zstrm.zfree = (free_func)Z_NULL;
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zstrm.opaque = (voidpf)Z_NULL;
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if ((err = inflateInit2(&zstrm, zlib_windowbits)) != Z_OK) {
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cli_dbgmsg("PNG: zlib: can't initialize (error = %d)\n", err);
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idat_state = PNG_IDAT_DECOMPRESSION_FAILED;
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} else {
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zstrm_initialized = true;
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uint64_t cur_width, cur_linebytes;
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int64_t cur_xoff = 0;
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int64_t cur_xskip = interlace_method ? 8 : 1;
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cur_width = (width - cur_xoff + cur_xskip - 1) / cur_xskip; /* round up */
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cur_linebytes = ((cur_width * sample_depth + 7) >> 3) + 1; /* round, fltr */
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image_size = cur_linebytes * height;
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cli_dbgmsg(" Image Size: " STDu64 "\n", image_size);
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idat_state = PNG_IDAT_DECOMPRESSION_IN_PROGRESS;
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}
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}
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/* skip scans of image data > max scan size. */
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if (image_size > ctx->engine->maxscansize) {
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idat_state = PNG_IDAT_DECOMPRESSION_COMPLETE;
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}
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if (idat_state == PNG_IDAT_DECOMPRESSION_IN_PROGRESS) {
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/*
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* We'll decompress the image data, but we don't _actually_ scan it.
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* We just want to know how much data comes out, so we can alert on the file
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* if it exceeds the image size calculated above (CVE-2010-1205).
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* Therefore, we'll use a static buffer and won't preserve the decompressed data.
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* This will prevent realloc errors from exceeding CLI_MAX_ALLOCATION,
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* will reduce RAM usage, and should be a wee bit faster.
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*/
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zstrm.next_in = ptr;
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zstrm.avail_in = chunk_data_length;
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while (err != Z_STREAM_END) {
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if (zstrm.avail_in == 0) {
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// Ran out of data before zstream ended... Additional IDAT chunks expected.
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idat_state = PNG_IDAT_DECOMPRESSION_IN_PROGRESS;
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break;
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}
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/* Just keep overwriting our buffer, we don't need to save the PNG image data. */
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zstrm.next_out = decompressed_data;
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zstrm.avail_out = BUFFER_SIZE;
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/* inflate! */
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err = inflate(&zstrm, Z_NO_FLUSH);
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decompressed_data_len += BUFFER_SIZE - zstrm.avail_out;
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if (err != Z_OK && err != Z_STREAM_END) {
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cli_dbgmsg("PNG: zlib: inflate error: %d, Image decompression failed!\n", err);
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inflateEnd(&zstrm);
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zstrm_initialized = false;
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idat_state = PNG_IDAT_DECOMPRESSION_FAILED;
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break;
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}
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}
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if (err == Z_STREAM_END) {
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cli_dbgmsg(" TOTAL decompressed: %zu\n", decompressed_data_len);
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inflateEnd(&zstrm);
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zstrm_initialized = false;
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idat_state = PNG_IDAT_DECOMPRESSION_COMPLETE;
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if ((decompressed_data_len > image_size) && (SCAN_HEURISTIC_BROKEN_MEDIA)) {
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status = cli_append_virus(ctx, "Heuristics.PNG.CVE-2010-1205");
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goto done;
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}
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} else {
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cli_dbgmsg(" Decompressed so far: %zu (Additional IDAT chunks expected)\n", decompressed_data_len);
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}
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}
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} else if (strcmp(chunk_type, "IEND") == 0) {
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/*------*
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| IEND |
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*------*/
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have_IEND = true;
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} else if (strcmp(chunk_type, "pHYs") == 0) {
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/*------*
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| pHYs |
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*------*/
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if (chunk_data_length != 9) {
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// Could it be CVE-2007-2365?
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cli_dbgmsg("PNG: invalid pHYs length\n");
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}
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} else if (strcmp(chunk_type, "tRNS") == 0) {
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/*------*
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| tRNS |
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*------*/
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if (color_type == 3) {
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if ((chunk_data_length > 256 || chunk_data_length > num_palette_entries) && !have_PLTE) {
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status = cli_append_virus(ctx, "Heuristics.PNG.CVE-2004-0597");
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goto done;
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}
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}
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}
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if (fmap_readn(map, &chunk_crc, offset, PNG_CHUNK_CRC_SIZE) != PNG_CHUNK_CRC_SIZE) {
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cli_dbgmsg("PNG: EOF while reading chunk crc\n");
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if (SCAN_HEURISTIC_BROKEN_MEDIA) {
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cli_append_possibly_unwanted(ctx, "Heuristics.Broken.Media.PNG.EOFReadingChunkCRC");
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status = CL_EPARSE;
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}
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goto scan_overlay;
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}
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chunk_crc = be32_to_host(chunk_crc);
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cli_dbgmsg(" Chunk CRC: 0x" STDx32 "\n", chunk_crc);
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offset += PNG_CHUNK_CRC_SIZE;
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if (have_IEND) {
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/*
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* That's all, folks!
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*/
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break;
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}
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}
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if (!have_IEND) {
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cli_dbgmsg("PNG: EOF before IEND chunk!\n");
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}
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if (idat_state == PNG_IDAT_DECOMPRESSION_IN_PROGRESS) {
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cli_dbgmsg("PNG: EOF before Image data decompression completed, truncated or malformed file?\n");
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}
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scan_overlay:
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if (status == CL_EPARSE) {
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/* We added with cli_append_possibly_unwanted so it will alert at the end if nothing else matches. */
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status = CL_CLEAN;
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}
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/* Check if there's an overlay, and scan it if one exists. */
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if (map->len - offset > 0) {
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cli_dbgmsg("PNG: Found " STDu64 " additional data after end of PNG! Scanning as a nested file.\n", map->len - offset);
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status = cli_magic_scan_nested_fmap_type(map, (size_t)offset, map->len - offset, ctx, CL_TYPE_ANY, NULL);
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goto done;
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}
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status = CL_CLEAN;
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done:
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if (NULL != decompressed_data) {
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free(decompressed_data);
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}
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if (zstrm_initialized) {
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inflateEnd(&zstrm);
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}
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return status;
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}
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