root/crypto/hmac.c

DEFINITIONS

1. align_ptr
2. hmac_setkey
3. hmac_init
4. hmac_update
5. hmac_final
6. hmac_digest
7. hmac_init_tfm
8. hmac_exit_tfm
9. hmac_free
10. hmac_alloc
11. hmac_module_init
12. hmac_module_exit

/*
 * Cryptographic API.
 *
 * HMAC: Keyed-Hashing for Message Authentication (RFC2104).
 *
 * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
 *
 * The HMAC implementation is derived from USAGI.
 * Copyright (c) 2002 Kazunori Miyazawa <miyazawa@linux-ipv6.org> / USAGI
 *
 * 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.
 *
 */

#include <crypto/algapi.h>
#include <crypto/scatterwalk.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>
#include <linux/string.h>

struct hmac_ctx {
        struct crypto_hash *child;
};

static inline void *align_ptr(void *p, unsigned int align)
{
        return (void *)ALIGN((unsigned long)p, align);
}

static inline struct hmac_ctx *hmac_ctx(struct crypto_hash *tfm)
{
        return align_ptr(crypto_hash_ctx_aligned(tfm) +
                         crypto_hash_blocksize(tfm) * 2 +
                         crypto_hash_digestsize(tfm), sizeof(void *));
}

static int hmac_setkey(struct crypto_hash *parent,
                       const u8 *inkey, unsigned int keylen)
{
        int bs = crypto_hash_blocksize(parent);
        int ds = crypto_hash_digestsize(parent);
        char *ipad = crypto_hash_ctx_aligned(parent);
        char *opad = ipad + bs;
        char *digest = opad + bs;
        struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
        struct crypto_hash *tfm = ctx->child;
        unsigned int i;

        if (keylen > bs) {
                struct hash_desc desc;
                struct scatterlist tmp;
                int tmplen;
                int err;

                desc.tfm = tfm;
                desc.flags = crypto_hash_get_flags(parent);
                desc.flags &= CRYPTO_TFM_REQ_MAY_SLEEP;

                err = crypto_hash_init(&desc);
                if (err)
                        return err;

                tmplen = bs * 2 + ds;
                sg_init_one(&tmp, ipad, tmplen);

                for (; keylen > tmplen; inkey += tmplen, keylen -= tmplen) {
                        memcpy(ipad, inkey, tmplen);
                        err = crypto_hash_update(&desc, &tmp, tmplen);
                        if (err)
                                return err;
                }

                if (keylen) {
                        memcpy(ipad, inkey, keylen);
                        err = crypto_hash_update(&desc, &tmp, keylen);
                        if (err)
                                return err;
                }

                err = crypto_hash_final(&desc, digest);
                if (err)
                        return err;

                inkey = digest;
                keylen = ds;
        }

        memcpy(ipad, inkey, keylen);
        memset(ipad + keylen, 0, bs - keylen);
        memcpy(opad, ipad, bs);

        for (i = 0; i < bs; i++) {
                ipad[i] ^= 0x36;
                opad[i] ^= 0x5c;
        }

        return 0;
}

static int hmac_init(struct hash_desc *pdesc)
{
        struct crypto_hash *parent = pdesc->tfm;
        int bs = crypto_hash_blocksize(parent);
        int ds = crypto_hash_digestsize(parent);
        char *ipad = crypto_hash_ctx_aligned(parent);
        struct hmac_ctx *ctx = align_ptr(ipad + bs * 2 + ds, sizeof(void *));
        struct hash_desc desc;
        struct scatterlist tmp;
        int err;

        desc.tfm = ctx->child;
        desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
        sg_init_one(&tmp, ipad, bs);

        err = crypto_hash_init(&desc);
        if (unlikely(err))
                return err;

        return crypto_hash_update(&desc, &tmp, bs);
}

static int hmac_update(struct hash_desc *pdesc,
                       struct scatterlist *sg, unsigned int nbytes)
{
        struct hmac_ctx *ctx = hmac_ctx(pdesc->tfm);
        struct hash_desc desc;

        desc.tfm = ctx->child;
        desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;

        return crypto_hash_update(&desc, sg, nbytes);
}

static int hmac_final(struct hash_desc *pdesc, u8 *out)
{
        struct crypto_hash *parent = pdesc->tfm;
        int bs = crypto_hash_blocksize(parent);
        int ds = crypto_hash_digestsize(parent);
        char *opad = crypto_hash_ctx_aligned(parent) + bs;
        char *digest = opad + bs;
        struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
        struct hash_desc desc;
        struct scatterlist tmp;
        int err;

        desc.tfm = ctx->child;
        desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
        sg_init_one(&tmp, opad, bs + ds);

        err = crypto_hash_final(&desc, digest);
        if (unlikely(err))
                return err;

        return crypto_hash_digest(&desc, &tmp, bs + ds, out);
}

static int hmac_digest(struct hash_desc *pdesc, struct scatterlist *sg,
                       unsigned int nbytes, u8 *out)
{
        struct crypto_hash *parent = pdesc->tfm;
        int bs = crypto_hash_blocksize(parent);
        int ds = crypto_hash_digestsize(parent);
        char *ipad = crypto_hash_ctx_aligned(parent);
        char *opad = ipad + bs;
        char *digest = opad + bs;
        struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
        struct hash_desc desc;
        struct scatterlist sg1[2];
        struct scatterlist sg2[1];
        int err;

        desc.tfm = ctx->child;
        desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;

        sg_init_table(sg1, 2);
        sg_set_buf(sg1, ipad, bs);
        scatterwalk_sg_chain(sg1, 2, sg);

        sg_init_table(sg2, 1);
        sg_set_buf(sg2, opad, bs + ds);

        err = crypto_hash_digest(&desc, sg1, nbytes + bs, digest);
        if (unlikely(err))
                return err;

        return crypto_hash_digest(&desc, sg2, bs + ds, out);
}

static int hmac_init_tfm(struct crypto_tfm *tfm)
{
        struct crypto_hash *hash;
        struct crypto_instance *inst = (void *)tfm->__crt_alg;
        struct crypto_spawn *spawn = crypto_instance_ctx(inst);
        struct hmac_ctx *ctx = hmac_ctx(__crypto_hash_cast(tfm));

        hash = crypto_spawn_hash(spawn);
        if (IS_ERR(hash))
                return PTR_ERR(hash);

        ctx->child = hash;
        return 0;
}

static void hmac_exit_tfm(struct crypto_tfm *tfm)
{
        struct hmac_ctx *ctx = hmac_ctx(__crypto_hash_cast(tfm));
        crypto_free_hash(ctx->child);
}

static void hmac_free(struct crypto_instance *inst)
{
        crypto_drop_spawn(crypto_instance_ctx(inst));
        kfree(inst);
}

static struct crypto_instance *hmac_alloc(struct rtattr **tb)
{
        struct crypto_instance *inst;
        struct crypto_alg *alg;
        int err;
        int ds;

        err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_HASH);
        if (err)
                return ERR_PTR(err);

        alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_HASH,
                                  CRYPTO_ALG_TYPE_HASH_MASK);
        if (IS_ERR(alg))
                return ERR_CAST(alg);

        inst = ERR_PTR(-EINVAL);
        ds = (alg->cra_flags & CRYPTO_ALG_TYPE_MASK) ==
             CRYPTO_ALG_TYPE_HASH ? alg->cra_hash.digestsize :
                                    alg->cra_digest.dia_digestsize;
        if (ds > alg->cra_blocksize)
                goto out_put_alg;

        inst = crypto_alloc_instance("hmac", alg);
        if (IS_ERR(inst))
                goto out_put_alg;

        inst->alg.cra_flags = CRYPTO_ALG_TYPE_HASH;
        inst->alg.cra_priority = alg->cra_priority;
        inst->alg.cra_blocksize = alg->cra_blocksize;
        inst->alg.cra_alignmask = alg->cra_alignmask;
        inst->alg.cra_type = &crypto_hash_type;

        inst->alg.cra_hash.digestsize = ds;

        inst->alg.cra_ctxsize = sizeof(struct hmac_ctx) +
                                ALIGN(inst->alg.cra_blocksize * 2 + ds,
                                      sizeof(void *));

        inst->alg.cra_init = hmac_init_tfm;
        inst->alg.cra_exit = hmac_exit_tfm;

        inst->alg.cra_hash.init = hmac_init;
        inst->alg.cra_hash.update = hmac_update;
        inst->alg.cra_hash.final = hmac_final;
        inst->alg.cra_hash.digest = hmac_digest;
        inst->alg.cra_hash.setkey = hmac_setkey;

out_put_alg:
        crypto_mod_put(alg);
        return inst;
}

static struct crypto_template hmac_tmpl = {
        .name = "hmac",
        .alloc = hmac_alloc,
        .free = hmac_free,
        .module = THIS_MODULE,
};

static int __init hmac_module_init(void)
{
        return crypto_register_template(&hmac_tmpl);
}

static void __exit hmac_module_exit(void)
{
        crypto_unregister_template(&hmac_tmpl);
}

module_init(hmac_module_init);
module_exit(hmac_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("HMAC hash algorithm");