// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
/*
* Routines for dealing with .zip archives.
*
* Copyright (c) Meta Platforms, Inc. and affiliates.
*/
#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>
#include "libbpf_internal.h"
#include "zip.h"
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wpacked"
#pragma GCC diagnostic ignored "-Wattributes"
/* Specification of ZIP file format can be found here:
* https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT
* For a high level overview of the structure of a ZIP file see
* sections 4.3.1 - 4.3.6.
*
* Data structures appearing in ZIP files do not contain any
* padding and they might be misaligned. To allow us to safely
* operate on pointers to such structures and their members, we
* declare the types as packed.
*/
#define END_OF_CD_RECORD_MAGIC 0x06054b50
/* See section 4.3.16 of the spec. */
struct end_of_cd_record {
/* Magic value equal to END_OF_CD_RECORD_MAGIC */
__u32 magic;
/* Number of the file containing this structure or 0xFFFF if ZIP64 archive.
* Zip archive might span multiple files (disks).
*/
__u16 this_disk;
/* Number of the file containing the beginning of the central directory or
* 0xFFFF if ZIP64 archive.
*/
__u16 cd_disk;
/* Number of central directory records on this disk or 0xFFFF if ZIP64
* archive.
*/
__u16 cd_records;
/* Number of central directory records on all disks or 0xFFFF if ZIP64
* archive.
*/
__u16 cd_records_total;
/* Size of the central directory record or 0xFFFFFFFF if ZIP64 archive. */
__u32 cd_size;
/* Offset of the central directory from the beginning of the archive or
* 0xFFFFFFFF if ZIP64 archive.
*/
__u32 cd_offset;
/* Length of comment data following end of central directory record. */
__u16 comment_length;
/* Up to 64k of arbitrary bytes. */
/* uint8_t comment[comment_length] */
} __attribute__((packed));
#define CD_FILE_HEADER_MAGIC 0x02014b50
#define FLAG_ENCRYPTED (1 << 0)
#define FLAG_HAS_DATA_DESCRIPTOR (1 << 3)
/* See section 4.3.12 of the spec. */
struct cd_file_header {
/* Magic value equal to CD_FILE_HEADER_MAGIC. */
__u32 magic;
__u16 version;
/* Minimum zip version needed to extract the file. */
__u16 min_version;
__u16 flags;
__u16 compression;
__u16 last_modified_time;
__u16 last_modified_date;
__u32 crc;
__u32 compressed_size;
__u32 uncompressed_size;
__u16 file_name_length;
__u16 extra_field_length;
__u16 file_comment_length;
/* Number of the disk where the file starts or 0xFFFF if ZIP64 archive. */
__u16 disk;
__u16 internal_attributes;
__u32 external_attributes;
/* Offset from the start of the disk containing the local file header to the
* start of the local file header.
*/
__u32 offset;
} __attribute__((packed));
#define LOCAL_FILE_HEADER_MAGIC 0x04034b50
/* See section 4.3.7 of the spec. */
struct local_file_header {
/* Magic value equal to LOCAL_FILE_HEADER_MAGIC. */
__u32 magic;
/* Minimum zip version needed to extract the file. */
__u16 min_version;
__u16 flags;
__u16 compression;
__u16 last_modified_time;
__u16 last_modified_date;
__u32 crc;
__u32 compressed_size;
__u32 uncompressed_size;
__u16 file_name_length;
__u16 extra_field_length;
} __attribute__((packed));
#pragma GCC diagnostic pop
struct zip_archive {
void *data;
__u32 size;
__u32 cd_offset;
__u32 cd_records;
};
static void *check_access(struct zip_archive *archive, __u32 offset, __u32 size)
{
if (offset + size > archive->size || offset > offset + size)
return NULL;
return archive->data + offset;
}
/* Returns 0 on success, -EINVAL on error and -ENOTSUP if the eocd indicates the
* archive uses features which are not supported.
*/
static int try_parse_end_of_cd(struct zip_archive *archive, __u32 offset)
{
__u16 comment_length, cd_records;
struct end_of_cd_record *eocd;
__u32 cd_offset, cd_size;
eocd = check_access(archive, offset, sizeof(*eocd));
if (!eocd || eocd->magic != END_OF_CD_RECORD_MAGIC)
return -EINVAL;
comment_length = eocd->comment_length;
if (offset + sizeof(*eocd) + comment_length != archive->size)
return -EINVAL;
cd_records = eocd->cd_records;
if (eocd->this_disk != 0 || eocd->cd_disk != 0 || eocd->cd_records_total != cd_records)
/* This is a valid eocd, but we only support single-file non-ZIP64 archives. */
return -ENOTSUP;
cd_offset = eocd->cd_offset;
cd_size = eocd->cd_size;
if (!check_access(archive, cd_offset, cd_size))
return -EINVAL;
archive->cd_offset = cd_offset;
archive->cd_records = cd_records;
return 0;
}
static int find_cd(struct zip_archive *archive)
{
int64_t limit, offset;
int rc = -EINVAL;
if (archive->size <= sizeof(struct end_of_cd_record))
return -EINVAL;
/* Because the end of central directory ends with a variable length array of
* up to 0xFFFF bytes we can't know exactly where it starts and need to
* search for it at the end of the file, scanning the (limit, offset] range.
*/
offset = archive->size - sizeof(struct end_of_cd_record);
limit = (int64_t)offset - (1 << 16);
for (; offset >= 0 && offset > limit && rc != 0; offset--) {
rc = try_parse_end_of_cd(archive, offset);
if (rc == -ENOTSUP)
break;
}
return rc;
}
struct zip_archive *zip_archive_open(const char *path)
{
struct zip_archive *archive;
int err, fd;
off_t size;
void *data;
fd = open(path, O_RDONLY | O_CLOEXEC);
if (fd < 0)
return ERR_PTR(-errno);
size = lseek(fd, 0, SEEK_END);
if (size == (off_t)-1 || size > UINT32_MAX) {
close(fd);
return ERR_PTR(-EINVAL);
}
data = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
err = -errno;
close(fd);
if (data == MAP_FAILED)
return ERR_PTR(err);
archive = malloc(sizeof(*archive));
if (!archive) {
munmap(data, size);
return ERR_PTR(-ENOMEM);
};
archive->data = data;
archive->size = size;
err = find_cd(archive);
if (err) {
munmap(data, size);
free(archive);
return ERR_PTR(err);
}
return archive;
}
void zip_archive_close(struct zip_archive *archive)
{
munmap(archive->data, archive->size);
free(archive);
}
static struct local_file_header *local_file_header_at_offset(struct zip_archive *archive,
__u32 offset)
{
struct local_file_header *lfh;
lfh = check_access(archive, offset, sizeof(*lfh));
if (!lfh || lfh->magic != LOCAL_FILE_HEADER_MAGIC)
return NULL;
return lfh;
}
static int get_entry_at_offset(struct zip_archive *archive, __u32 offset, struct zip_entry *out)
{
struct local_file_header *lfh;
__u32 compressed_size;
const char *name;
void *data;
lfh = local_file_header_at_offset(archive, offset);
if (!lfh)
return -EINVAL;
offset += sizeof(*lfh);
if ((lfh->flags & FLAG_ENCRYPTED) || (lfh->flags & FLAG_HAS_DATA_DESCRIPTOR))
return -EINVAL;
name = check_access(archive, offset, lfh->file_name_length);
if (!name)
return -EINVAL;
offset += lfh->file_name_length;
if (!check_access(archive, offset, lfh->extra_field_length))
return -EINVAL;
offset += lfh->extra_field_length;
compressed_size = lfh->compressed_size;
data = check_access(archive, offset, compressed_size);
if (!data)
return -EINVAL;
out->compression = lfh->compression;
out->name_length = lfh->file_name_length;
out->name = name;
out->data = data;
out->data_length = compressed_size;
out->data_offset = offset;
return 0;
}
int zip_archive_find_entry(struct zip_archive *archive, const char *file_name,
struct zip_entry *out)
{
size_t file_name_length = strlen(file_name);
__u32 i, offset = archive->cd_offset;
for (i = 0; i < archive->cd_records; ++i) {
__u16 cdfh_name_length, cdfh_flags;
struct cd_file_header *cdfh;
const char *cdfh_name;
cdfh = check_access(archive, offset, sizeof(*cdfh));
if (!cdfh || cdfh->magic != CD_FILE_HEADER_MAGIC)
return -EINVAL;
offset += sizeof(*cdfh);
cdfh_name_length = cdfh->file_name_length;
cdfh_name = check_access(archive, offset, cdfh_name_length);
if (!cdfh_name)
return -EINVAL;
cdfh_flags = cdfh->flags;
if ((cdfh_flags & FLAG_ENCRYPTED) == 0 &&
(cdfh_flags & FLAG_HAS_DATA_DESCRIPTOR) == 0 &&
file_name_length == cdfh_name_length &&
memcmp(file_name, archive->data + offset, file_name_length) == 0) {
return get_entry_at_offset(archive, cdfh->offset, out);
}
offset += cdfh_name_length;
offset += cdfh->extra_field_length;
offset += cdfh->file_comment_length;
}
return -ENOENT;
}
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