382 lines
12 KiB
C
382 lines
12 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) 2007-2013 Sourcefire, Inc.
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*
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* Authors: Nigel Horne
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*
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* Summary: Extract files compressed with TAR compression format.
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*
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* Acknowledgements: ClamAV untar code is based on a public domain minitar utility
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* by Charles G. Waldman.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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* MA 02110-1301, USA.
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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 <errno.h>
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#include <string.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 <sys/stat.h>
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#include <fcntl.h>
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#ifdef HAVE_SYS_PARAM_H
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#include <sys/param.h> /* for NAME_MAX */
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#endif
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#include "clamav.h"
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#include "others.h"
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#include "untar.h"
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#include "mbox.h"
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#include "blob.h"
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#include "scanners.h"
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#include "matcher.h"
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#define TARHEADERSIZE 512
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/* BLOCKSIZE must be >= TARHEADERSIZE */
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#define BLOCKSIZE TARHEADERSIZE
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#define TARSIZEOFFSET 124
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#define TARSIZELEN 12
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#define TARCHECKSUMOFFSET 148
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#define TARCHECKSUMLEN 8
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#define TARFILETYPEOFFSET 156
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static int
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octal(const char *str)
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{
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int ret;
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if (sscanf(str, "%o", (unsigned int *)&ret) != 1)
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return -1;
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return ret;
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}
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/**
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* Retrieve checksum values from a tar header block.
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* @param header Header data block, padded with zeroes to reach BLOCKSIZE
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* @return int value of checksum, -1 (from octal()) if bad value
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*/
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static int
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getchecksum(const char *header)
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{
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char ochecksum[TARCHECKSUMLEN + 1];
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int checksum = -1;
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strncpy(ochecksum, header + TARCHECKSUMOFFSET, TARCHECKSUMLEN);
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ochecksum[TARCHECKSUMLEN] = '\0';
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checksum = octal(ochecksum);
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return checksum;
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}
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/**
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* Calculate checksum values for tar header blocks.
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* @param header Header data block, padded with zeroes to reach BLOCKSIZE
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* @param targetsum Check value to match (as int not octal!)
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* @return 0 if checksum matches target, -1 if not
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*/
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static int
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testchecksum(const char *header, int targetsum)
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{
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const unsigned char *posix;
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const signed char *legacy;
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int posix_sum = 0, legacy_sum = 0;
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int i;
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// targetsum -1 represents an error from octal()
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if (targetsum == -1) {
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return -1;
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}
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/* Build checksums. POSIX is unsigned; some legacy tars use signed. */
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posix = (unsigned char *)header;
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legacy = (signed char *)header;
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for (i = 0; i < BLOCKSIZE; i++) {
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if ((i >= TARCHECKSUMOFFSET) && (i < TARCHECKSUMOFFSET + TARCHECKSUMLEN)) {
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/* Use ascii value of space in place of checksum value */
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posix_sum += 32;
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legacy_sum += 32;
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} else {
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posix_sum += posix[i];
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legacy_sum += legacy[i];
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}
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}
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if ((targetsum == posix_sum) || (targetsum == legacy_sum)) {
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return 0;
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}
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return -1;
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}
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cl_error_t cli_untar(const char *dir, unsigned int posix, cli_ctx *ctx)
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{
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cl_error_t ret;
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size_t size = 0;
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int size_int = 0;
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int fout = -1;
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int in_block = 0;
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int last_header_bad = 0;
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int limitnear = 0;
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unsigned int files = 0;
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char fullname[PATH_MAX + 1];
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char name[101];
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size_t pos = 0;
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size_t currsize = 0;
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char zero[BLOCKSIZE];
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cli_dbgmsg("In untar(%s)\n", dir);
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memset(zero, 0, sizeof(zero));
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for (;;) {
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const char *block;
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size_t nread;
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block = fmap_need_off_once_len(ctx->fmap, pos, BLOCKSIZE, &nread);
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cli_dbgmsg("cli_untar: pos = %lu\n", (unsigned long)pos);
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if (!in_block && !nread)
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break;
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if (!nread)
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block = zero;
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if (!block) {
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if (fout >= 0)
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close(fout);
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cli_errmsg("cli_untar: block read error\n");
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return CL_EREAD;
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}
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pos += nread;
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if (!in_block) {
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char type;
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int directory, skipEntry = 0;
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int checksum = -1;
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char magic[7], osize[TARSIZELEN + 1];
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currsize = 0;
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if (fout >= 0) {
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lseek(fout, 0, SEEK_SET);
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ret = cli_magic_scan_desc(fout, fullname, ctx, name, LAYER_ATTRIBUTES_NONE);
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close(fout);
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if (!ctx->engine->keeptmp) {
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if (cli_unlink(fullname)) {
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return CL_EUNLINK;
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}
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}
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if (ret != CL_SUCCESS) {
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return ret;
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}
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fout = -1;
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}
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if (block[0] == '\0') /* We're done */
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break;
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if ((ret = cli_checklimits("cli_untar", ctx, 0, 0, 0)) != CL_CLEAN)
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return ret;
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if (nread < TARHEADERSIZE) {
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return CL_CLEAN;
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}
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checksum = getchecksum(block);
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cli_dbgmsg("cli_untar: Candidate checksum = %d, [%o in octal]\n", checksum, checksum);
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if (testchecksum(block, checksum) != 0) {
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// If checksum is bad, dump and look for next header block
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cli_dbgmsg("cli_untar: Invalid checksum in tar header. Skip to next...\n");
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if (last_header_bad == 0) {
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last_header_bad++;
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cli_dbgmsg("cli_untar: Invalid checksum found inside archive!\n");
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}
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continue;
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} else {
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last_header_bad = 0;
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cli_dbgmsg("cli_untar: Checksum %d is valid.\n", checksum);
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}
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if (posix) {
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strncpy(magic, block + 257, 5);
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magic[5] = '\0';
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if (strcmp(magic, "ustar") != 0) {
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cli_dbgmsg("cli_untar: Incorrect magic string '%s' in tar header\n", magic);
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return CL_EFORMAT;
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}
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}
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type = block[TARFILETYPEOFFSET];
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switch (type) {
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default:
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cli_dbgmsg("cli_untar: unknown type flag %c\n", type);
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/* fall-through */
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case '0': /* plain file */
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case '\0': /* plain file */
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case '7': /* contiguous file */
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case 'M': /* continuation of a file from another volume; might as well scan it. */
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files++;
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directory = 0;
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break;
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case '1': /* Link to already archived file */
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case '5': /* directory */
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case '2': /* sym link */
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case '3': /* char device */
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case '4': /* block device */
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case '6': /* fifo special */
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case 'V': /* Volume header */
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directory = 1;
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break;
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case 'K':
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case 'L':
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/* GNU extension - ././@LongLink
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* Discard the blocks with the extended filename,
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* the last header will contain parts of it anyway
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*/
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case 'N': /* Old GNU format way of storing long filenames. */
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case 'A': /* Solaris ACL */
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case 'E': /* Solaris Extended attribute s*/
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case 'I': /* Inode only */
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case 'g': /* Global extended header */
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case 'x': /* Extended attributes */
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case 'X': /* Extended attributes (POSIX) */
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directory = 0;
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skipEntry = 1;
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break;
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}
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if (directory) {
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in_block = 0;
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continue;
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}
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strncpy(osize, block + TARSIZEOFFSET, TARSIZELEN);
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osize[TARSIZELEN] = '\0';
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size_int = octal(osize);
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if (size_int < 0) {
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cli_dbgmsg("cli_untar: Invalid size in tar header\n");
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skipEntry++;
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} else {
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size = (size_t)size_int;
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cli_dbgmsg("cli_untar: size = %zu\n", size);
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ret = cli_checklimits("cli_untar", ctx, size, 0, 0);
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switch (ret) {
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case CL_EMAXFILES: // Scan no more files
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skipEntry++;
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limitnear = 0;
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break;
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case CL_EMAXSIZE: // Either single file limit or total byte limit would be exceeded
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cli_dbgmsg("cli_untar: would exceed limit, will try up to max");
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limitnear = 1;
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break;
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default: // Ok based on reported content size
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limitnear = 0;
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break;
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}
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}
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if (skipEntry) {
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const int nskip = (size % BLOCKSIZE || !size) ? size + BLOCKSIZE - (size % BLOCKSIZE) : size;
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if (nskip < 0) {
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cli_dbgmsg("cli_untar: got negative skip size, giving up\n");
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return CL_CLEAN;
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}
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cli_dbgmsg("cli_untar: skipping entry\n");
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pos += nskip;
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continue;
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}
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strncpy(name, block, 100);
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name[100] = '\0';
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if (cli_matchmeta(ctx, name, size, size, 0, files, 0, NULL) == CL_VIRUS) {
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return CL_VIRUS;
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}
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snprintf(fullname, sizeof(fullname) - 1, "%s" PATHSEP "tar%02u", dir, files);
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fullname[sizeof(fullname) - 1] = '\0';
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fout = open(fullname, O_RDWR | O_CREAT | O_EXCL | O_TRUNC | O_BINARY, 0600);
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if (fout < 0) {
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char err[128];
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cli_errmsg("cli_untar: Can't create temporary file %s: %s\n", fullname, cli_strerror(errno, err, sizeof(err)));
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return CL_ETMPFILE;
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}
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cli_dbgmsg("cli_untar: extracting to %s\n", fullname);
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in_block = 1;
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} else { /* write or continue writing file contents */
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size_t nbytes, nwritten;
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int skipwrite = 0;
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char err[128];
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nbytes = (size > 512) ? 512 : size;
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if (nread && (nread < nbytes))
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nbytes = nread;
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if (limitnear > 0) {
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currsize += nbytes;
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cli_dbgmsg("cli_untar: Approaching limit...\n");
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if (cli_checklimits("cli_untar", ctx, (unsigned long)currsize, 0, 0) != CL_SUCCESS) {
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// Limit would be exceeded by this file, suppress writing beyond limit
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// Need to keep reading to get to end of file chunk
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skipwrite++;
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}
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}
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if (skipwrite == 0) {
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nwritten = cli_writen(fout, block, nbytes);
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if (nwritten != nbytes) {
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cli_errmsg("cli_untar: only wrote %zu bytes to file %s (out of disc space?): %s\n",
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nwritten, fullname, cli_strerror(errno, err, sizeof(err)));
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close(fout);
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return CL_EWRITE;
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}
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}
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if (nbytes > size) {
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cli_warnmsg("cli_untar: More bytes written than requested!\n");
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size = 0;
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} else {
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size -= nbytes;
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}
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if ((size != 0) && (nread == 0)) {
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// Truncated tar file, so end file content like tar behavior
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cli_dbgmsg("cli_untar: No bytes read! Forcing end of file content.\n");
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size = 0;
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}
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}
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if (size == 0)
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in_block = 0;
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}
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if (fout >= 0) {
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lseek(fout, 0, SEEK_SET);
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ret = cli_magic_scan_desc(fout, fullname, ctx, name, LAYER_ATTRIBUTES_NONE);
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close(fout);
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if (!ctx->engine->keeptmp) {
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if (cli_unlink(fullname)) {
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return CL_EUNLINK;
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}
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}
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if (ret != CL_SUCCESS) {
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return ret;
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}
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}
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return CL_CLEAN;
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}
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