source: mainline/boot/generic/src/gzip.c@ 39916d6

/*
 * SPDX-FileCopyrightText: 2014 Martin Decky
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

// XXX: This file is a duplicate of the same in uspace/lib/compress

#include <stdint.h>
#include <stddef.h>
#include <errno.h>
#include <memstr.h>
#include <byteorder.h>
#include <gzip.h>
#include <inflate.h>

#define GZIP_ID1  UINT8_C(0x1f)
#define GZIP_ID2  UINT8_C(0x8b)

#define GZIP_METHOD_DEFLATE  UINT8_C(0x08)

#define GZIP_FLAGS_MASK     UINT8_C(0x1f)
#define GZIP_FLAG_FHCRC     UINT8_C(1 << 1)
#define GZIP_FLAG_FEXTRA    UINT8_C(1 << 2)
#define GZIP_FLAG_FNAME     UINT8_C(1 << 3)
#define GZIP_FLAG_FCOMMENT  UINT8_C(1 << 4)

typedef struct {
        uint8_t id1;
        uint8_t id2;
        uint8_t method;
        uint8_t flags;
        uint32_t mtime;
        uint8_t extra_flags;
        uint8_t os;
} __attribute__((packed)) gzip_header_t;

typedef struct {
        uint32_t crc32;
        uint32_t size;
} __attribute__((packed)) gzip_footer_t;

/** Check GZIP signature
 *
 * Checks whether the source buffer start with a GZIP signature.
 *
 * @param[in] src    Source data buffer.
 * @param[in] srclen Source buffer size (bytes).
 *
 * @return True if GZIP signature found.
 * @return False if no GZIP signature found.
 *
 */
bool gzip_check(const void *src, size_t srclen)
{
        if ((srclen < (sizeof(gzip_header_t) + sizeof(gzip_footer_t))))
                return false;

        gzip_header_t header;
        memcpy(&header, src, sizeof(header));

        if ((header.id1 != GZIP_ID1) ||
            (header.id2 != GZIP_ID2) ||
            (header.method != GZIP_METHOD_DEFLATE) ||
            ((header.flags & (~GZIP_FLAGS_MASK)) != 0))
                return false;

        return true;
}

/** Get uncompressed size
 *
 * Note that the uncompressed size is read from the GZIP footer
 * (and not calculated by acutally decompressing the GZip archive).
 * Thus the source of the GZip archive needs to be trusted.
 *
 * @param[in]  src    Source data buffer.
 * @param[out] srclen Source buffer size (bytes).
 *
 * @return Uncompressed size.
 *
 */
size_t gzip_size(const void *src, size_t srclen)
{
        if (!gzip_check(src, srclen))
                return 0;

        gzip_footer_t footer;
        memcpy(&footer, src + srclen - sizeof(footer), sizeof(footer));

        return uint32_t_le2host(footer.size);
}

/** Expand GZIP compressed data
 *
 * The routine compares the output buffer size with
 * the size encoded in the input stream. This
 * effectively limits the size of the uncompressed
 * data to 4 GiB (expanding input streams that actually
 * encode more data will always fail).
 *
 * So far, no CRC is perfomed.
 *
 * @param[in]  src     Source data buffer.
 * @param[in]  srclen  Source buffer size (bytes).
 * @param[out] dest    Destination data buffer.
 * @param[out] destlen Destination buffer size (bytes).
 *
 * @return EOK on success.
 * @return ENOENT on distance too large.
 * @return EINVAL on invalid Huffman code, invalid deflate data,
 *                   invalid compression method or invalid stream.
 * @return ELIMIT on input buffer overrun.
 * @return ENOMEM on output buffer overrun.
 *
 */
int gzip_expand(const void *src, size_t srclen, void *dest, size_t destlen)
{
        if (!gzip_check(src, srclen))
                return EINVAL;

        /* Decode header and footer */

        gzip_header_t header;
        memcpy(&header, src, sizeof(header));

        gzip_footer_t footer;
        memcpy(&footer, src + srclen - sizeof(footer), sizeof(footer));

        if (destlen != uint32_t_le2host(footer.size))
                return EINVAL;

        /* Ignore extra metadata */

        const void *stream = src + sizeof(header);
        size_t stream_length = srclen - sizeof(header) - sizeof(footer);

        if ((header.flags & GZIP_FLAG_FEXTRA) != 0) {
                uint16_t extra_length;

                if (stream_length < sizeof(extra_length))
                        return EINVAL;

                memcpy(&extra_length, stream, sizeof(extra_length));
                stream += sizeof(extra_length);
                stream_length -= sizeof(extra_length);

                if (stream_length < extra_length)
                        return EINVAL;

                stream += extra_length;
                stream_length -= extra_length;
        }

        if ((header.flags & GZIP_FLAG_FNAME) != 0) {
                while (*((uint8_t *) stream) != 0) {
                        if (stream_length == 0)
                                return EINVAL;

                        stream++;
                        stream_length--;
                }

                if (stream_length == 0)
                        return EINVAL;

                stream++;
                stream_length--;
        }

        if ((header.flags & GZIP_FLAG_FCOMMENT) != 0) {
                while (*((uint8_t *) stream) != 0) {
                        if (stream_length == 0)
                                return EINVAL;

                        stream++;
                        stream_length--;
                }

                if (stream_length == 0)
                        return EINVAL;

                stream++;
                stream_length--;
        }

        if ((header.flags & GZIP_FLAG_FHCRC) != 0) {
                if (stream_length < 2)
                        return EINVAL;

                stream += 2;
                stream_length -= 2;
        }

        /* Inflate the data */
        return inflate(stream, stream_length, dest, destlen);
}