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/* SPDX-License-Identifier: GPL-3.0-or-later */
/*
* read_header.c
*
* Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
*/
#include "config.h"
#include "internal.h"
static bool is_zero_block(const tar_header_t *hdr)
{
const unsigned char *ptr = (const unsigned char *)hdr;
return ptr[0] == '\0' && memcmp(ptr, ptr + 1, sizeof(*hdr) - 1) == 0;
}
static int check_version(const tar_header_t *hdr)
{
char buffer[sizeof(hdr->magic) + sizeof(hdr->version)];
memset(buffer, '\0', sizeof(buffer));
if (memcmp(hdr->magic, buffer, sizeof(hdr->magic)) == 0 &&
memcmp(hdr->version, buffer, sizeof(hdr->version)) == 0)
return ETV_V7_UNIX;
if (memcmp(hdr->magic, TAR_MAGIC, sizeof(hdr->magic)) == 0 &&
memcmp(hdr->version, TAR_VERSION, sizeof(hdr->version)) == 0)
return ETV_POSIX;
if (memcmp(hdr->magic, TAR_MAGIC_OLD, sizeof(hdr->magic)) == 0 &&
memcmp(hdr->version, TAR_VERSION_OLD, sizeof(hdr->version)) == 0)
return ETV_PRE_POSIX;
return ETV_UNKNOWN;
}
static int decode_header(const tar_header_t *hdr, unsigned int set_by_pax,
tar_header_decoded_t *out, int version)
{
size_t len1, len2;
sqfs_u64 field;
if (!(set_by_pax & PAX_NAME)) {
if (hdr->tail.posix.prefix[0] != '\0' &&
version == ETV_POSIX) {
len1 = strnlen(hdr->name, sizeof(hdr->name));
len2 = strnlen(hdr->tail.posix.prefix,
sizeof(hdr->tail.posix.prefix));
out->name = malloc(len1 + 1 + len2 + 1);
if (out->name != NULL) {
memcpy(out->name, hdr->tail.posix.prefix, len2);
out->name[len2] = '/';
memcpy(out->name + len2 + 1, hdr->name, len1);
out->name[len1 + 1 + len2] = '\0';
}
} else {
out->name = strndup(hdr->name, sizeof(hdr->name));
}
if (out->name == NULL) {
perror("decoding filename");
return -1;
}
}
if (!(set_by_pax & PAX_SIZE)) {
if (read_number(hdr->size, sizeof(hdr->size), &out->record_size))
return -1;
}
if (!(set_by_pax & PAX_UID)) {
if (read_number(hdr->uid, sizeof(hdr->uid), &field))
return -1;
out->sb.st_uid = field;
}
if (!(set_by_pax & PAX_GID)) {
if (read_number(hdr->gid, sizeof(hdr->gid), &field))
return -1;
out->sb.st_gid = field;
}
if (!(set_by_pax & PAX_DEV_MAJ)) {
if (read_number(hdr->devmajor, sizeof(hdr->devmajor), &field))
return -1;
out->sb.st_rdev = makedev(field, minor(out->sb.st_rdev));
}
if (!(set_by_pax & PAX_DEV_MIN)) {
if (read_number(hdr->devminor, sizeof(hdr->devminor), &field))
return -1;
out->sb.st_rdev = makedev(major(out->sb.st_rdev), field);
}
if (!(set_by_pax & PAX_MTIME)) {
if (read_number(hdr->mtime, sizeof(hdr->mtime), &field))
return -1;
if (field & 0x8000000000000000UL) {
field = ~field + 1;
out->mtime = -((sqfs_s64)field);
} else {
out->mtime = field;
}
}
if (read_octal(hdr->mode, sizeof(hdr->mode), &field))
return -1;
out->sb.st_mode = field & 07777;
if (hdr->typeflag == TAR_TYPE_LINK ||
hdr->typeflag == TAR_TYPE_SLINK) {
if (!(set_by_pax & PAX_SLINK_TARGET)) {
out->link_target = strndup(hdr->linkname,
sizeof(hdr->linkname));
if (out->link_target == NULL) {
perror("decoding symlink target");
return -1;
}
}
}
out->unknown_record = false;
switch (hdr->typeflag) {
case '\0':
case TAR_TYPE_FILE:
case TAR_TYPE_GNU_SPARSE:
out->sb.st_mode |= S_IFREG;
break;
case TAR_TYPE_LINK:
out->is_hard_link = true;
break;
case TAR_TYPE_SLINK:
out->sb.st_mode = S_IFLNK | 0777;
break;
case TAR_TYPE_CHARDEV:
out->sb.st_mode |= S_IFCHR;
break;
case TAR_TYPE_BLOCKDEV:
out->sb.st_mode |= S_IFBLK;
break;
case TAR_TYPE_DIR:
out->sb.st_mode |= S_IFDIR;
break;
case TAR_TYPE_FIFO:
out->sb.st_mode |= S_IFIFO;
break;
default:
out->unknown_record = true;
break;
}
if (sizeof(time_t) * CHAR_BIT < 64) {
if (out->mtime > (sqfs_s64)INT32_MAX) {
out->sb.st_mtime = INT32_MAX;
} else if (out->mtime < (sqfs_s64)INT32_MIN) {
out->sb.st_mtime = INT32_MIN;
} else {
out->sb.st_mtime = out->mtime;
}
} else {
out->sb.st_mtime = out->mtime;
}
return 0;
}
int read_header(FILE *fp, tar_header_decoded_t *out)
{
unsigned int set_by_pax = 0;
bool prev_was_zero = false;
sqfs_u64 pax_size;
tar_header_t hdr;
int version;
memset(out, 0, sizeof(*out));
for (;;) {
if (read_retry("reading tar header", fp, &hdr, sizeof(hdr)))
goto fail;
if (is_zero_block(&hdr)) {
if (prev_was_zero)
goto out_eof;
prev_was_zero = true;
continue;
}
prev_was_zero = false;
version = check_version(&hdr);
if (version == ETV_UNKNOWN)
goto fail_magic;
if (!is_checksum_valid(&hdr))
goto fail_chksum;
switch (hdr.typeflag) {
case TAR_TYPE_GNU_SLINK:
if (read_number(hdr.size, sizeof(hdr.size), &pax_size))
goto fail;
if (pax_size < 1 || pax_size > TAR_MAX_SYMLINK_LEN)
goto fail_slink_len;
free(out->link_target);
out->link_target = record_to_memory(fp, pax_size);
if (out->link_target == NULL)
goto fail;
set_by_pax |= PAX_SLINK_TARGET;
continue;
case TAR_TYPE_GNU_PATH:
if (read_number(hdr.size, sizeof(hdr.size), &pax_size))
goto fail;
if (pax_size < 1 || pax_size > TAR_MAX_PATH_LEN)
goto fail_path_len;
free(out->name);
out->name = record_to_memory(fp, pax_size);
if (out->name == NULL)
goto fail;
set_by_pax |= PAX_NAME;
continue;
case TAR_TYPE_PAX_GLOBAL:
if (read_number(hdr.size, sizeof(hdr.size), &pax_size))
goto fail;
skip_entry(fp, pax_size);
continue;
case TAR_TYPE_PAX:
clear_header(out);
if (read_number(hdr.size, sizeof(hdr.size), &pax_size))
goto fail;
if (pax_size < 1 || pax_size > TAR_MAX_PAX_LEN)
goto fail_pax_len;
set_by_pax = 0;
if (read_pax_header(fp, pax_size, &set_by_pax, out))
goto fail;
continue;
case TAR_TYPE_GNU_SPARSE:
free_sparse_list(out->sparse);
out->sparse = read_gnu_old_sparse(fp, &hdr);
if (out->sparse == NULL)
goto fail;
if (read_number(hdr.tail.gnu.realsize,
sizeof(hdr.tail.gnu.realsize),
&out->actual_size))
goto fail;
break;
}
break;
}
if (decode_header(&hdr, set_by_pax, out, version))
goto fail;
if (out->sparse != NULL) {
out->sb.st_size = out->actual_size;
} else {
out->sb.st_size = out->record_size;
out->actual_size = out->record_size;
}
return 0;
out_eof:
clear_header(out);
return 1;
fail_slink_len:
fprintf(stderr, "rejecting GNU symlink header with size %lu\n",
(unsigned long)pax_size);
goto fail;
fail_path_len:
fprintf(stderr, "rejecting GNU long path header with size %lu\n",
(unsigned long)pax_size);
goto fail;
fail_pax_len:
fprintf(stderr, "rejecting PAX header with size %lu\n",
(unsigned long)pax_size);
goto fail;
fail_magic:
fputs("input is not a ustar tar archive!\n", stderr);
goto fail;
fail_chksum:
fputs("invalid tar header checksum!\n", stderr);
goto fail;
fail:
clear_header(out);
return -1;
}
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