deflate.c

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/*
 * Cryptographic API.
 *
 * Deflate algorithm (RFC 1951), implemented here primarily for use
 * by IPCOMP (RFC 3173 & RFC 2394).
 *
 * Copyright (c) 2003 James Morris <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * FIXME: deflate transforms will require up to a total of about 436k of kernel
 * memory on i386 (390k for compression, the rest for decompression), as the
 * current zlib kernel code uses a worst case pre-allocation system by default.
 * This needs to be fixed so that the amount of memory required is properly
 * related to the  winbits and memlevel parameters.
 *
 * The default winbits of 11 should suit most packets, and it may be something
 * to configure on a per-tfm basis in the future.
 *
 * Currently, compression history is not maintained between tfm calls, as
 * it is not needed for IPCOMP and keeps the code simpler.  It can be
 * implemented if someone wants it.
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/crypto.h>
#include <linux/zlib.h>
#include <linux/vmalloc.h>
#include <linux/interrupt.h>
#include <linux/mm.h>
#include <linux/net.h>

#define DEFLATE_DEF_LEVEL       Z_DEFAULT_COMPRESSION
#define DEFLATE_DEF_WINBITS     11
#define DEFLATE_DEF_MEMLEVEL        MAX_MEM_LEVEL

struct deflate_ctx {
    struct z_stream_s comp_stream;
    struct z_stream_s decomp_stream;
};

static int deflate_comp_init(struct deflate_ctx *ctx)
{
    int ret = 0;
    struct z_stream_s *stream = &ctx->comp_stream;

    stream->workspace = vzalloc(zlib_deflate_workspacesize(
                -DEFLATE_DEF_WINBITS, DEFLATE_DEF_MEMLEVEL));
    if (!stream->workspace) {
        ret = -ENOMEM;
        goto out;
    }
    ret = zlib_deflateInit2(stream, DEFLATE_DEF_LEVEL, Z_DEFLATED,
                            -DEFLATE_DEF_WINBITS, DEFLATE_DEF_MEMLEVEL,
                            Z_DEFAULT_STRATEGY);
    if (ret != Z_OK) {
        ret = -EINVAL;
        goto out_free;
    }
out:
    return ret;
out_free:
    vfree(stream->workspace);
    goto out;
}

static int deflate_decomp_init(struct deflate_ctx *ctx)
{
    int ret = 0;
    struct z_stream_s *stream = &ctx->decomp_stream;

    stream->workspace = vzalloc(zlib_inflate_workspacesize());
    if (!stream->workspace) {
        ret = -ENOMEM;
        goto out;
    }
    ret = zlib_inflateInit2(stream, -DEFLATE_DEF_WINBITS);
    if (ret != Z_OK) {
        ret = -EINVAL;
        goto out_free;
    }
out:
    return ret;
out_free:
    vfree(stream->workspace);
    goto out;
}

static void deflate_comp_exit(struct deflate_ctx *ctx)
{
    zlib_deflateEnd(&ctx->comp_stream);
    vfree(ctx->comp_stream.workspace);
}

static void deflate_decomp_exit(struct deflate_ctx *ctx)
{
    zlib_inflateEnd(&ctx->decomp_stream);
    vfree(ctx->decomp_stream.workspace);
}

static int deflate_init(struct crypto_tfm *tfm)
{
    struct deflate_ctx *ctx = crypto_tfm_ctx(tfm);
    int ret;

    ret = deflate_comp_init(ctx);
    if (ret)
        goto out;
    ret = deflate_decomp_init(ctx);
    if (ret)
        deflate_comp_exit(ctx);
out:
    return ret;
}

static void deflate_exit(struct crypto_tfm *tfm)
{
    struct deflate_ctx *ctx = crypto_tfm_ctx(tfm);

    deflate_comp_exit(ctx);
    deflate_decomp_exit(ctx);
}

static int deflate_compress(struct crypto_tfm *tfm, const u8 *src,
                unsigned int slen, u8 *dst, unsigned int *dlen)
{
    int ret = 0;
    struct deflate_ctx *dctx = crypto_tfm_ctx(tfm);
    struct z_stream_s *stream = &dctx->comp_stream;

    ret = zlib_deflateReset(stream);
    if (ret != Z_OK) {
        ret = -EINVAL;
        goto out;
    }

    stream->next_in = (u8 *)src;
    stream->avail_in = slen;
    stream->next_out = (u8 *)dst;
    stream->avail_out = *dlen;

    ret = zlib_deflate(stream, Z_FINISH);
    if (ret != Z_STREAM_END) {
        ret = -EINVAL;
        goto out;
    }
    ret = 0;
    *dlen = stream->total_out;
out:
    return ret;
}

static int deflate_decompress(struct crypto_tfm *tfm, const u8 *src,
                  unsigned int slen, u8 *dst, unsigned int *dlen)
{

    int ret = 0;
    struct deflate_ctx *dctx = crypto_tfm_ctx(tfm);
    struct z_stream_s *stream = &dctx->decomp_stream;

    ret = zlib_inflateReset(stream);
    if (ret != Z_OK) {
        ret = -EINVAL;
        goto out;
    }

    stream->next_in = (u8 *)src;
    stream->avail_in = slen;
    stream->next_out = (u8 *)dst;
    stream->avail_out = *dlen;

    ret = zlib_inflate(stream, Z_SYNC_FLUSH);
    /*
     * Work around a bug in zlib, which sometimes wants to taste an extra
     * byte when being used in the (undocumented) raw deflate mode.
     * (From USAGI).
     */
    if (ret == Z_OK && !stream->avail_in && stream->avail_out) {
        u8 zerostuff = 0;
        stream->next_in = &zerostuff;
        stream->avail_in = 1;
        ret = zlib_inflate(stream, Z_FINISH);
    }
    if (ret != Z_STREAM_END) {
        ret = -EINVAL;
        goto out;
    }
    ret = 0;
    *dlen = stream->total_out;
out:
    return ret;
}

static struct crypto_alg alg = {
    .cra_name       = "deflate",
    .cra_flags      = CRYPTO_ALG_TYPE_COMPRESS,
    .cra_ctxsize        = sizeof(struct deflate_ctx),
    .cra_module     = THIS_MODULE,
    .cra_init       = deflate_init,
    .cra_exit       = deflate_exit,
    .cra_u          = { .compress = {
    .coa_compress       = deflate_compress,
    .coa_decompress     = deflate_decompress } }
};

static int __init deflate_mod_init(void)
{
    return crypto_register_alg(&alg);
}

static void __exit deflate_mod_fini(void)
{
    crypto_unregister_alg(&alg);
}

module_init(deflate_mod_init);
module_exit(deflate_mod_fini);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Deflate Compression Algorithm for IPCOMP");
MODULE_AUTHOR("James Morris <[email protected]>");