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[CRYPTO] hmac: Add crypto template implementation
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This patch rewrites HMAC as a crypto template.  This means that HMAC is no
longer a hard-coded part of the API.  It's now a template that generates
standard digest algorithms like any other.

The old HMAC is preserved until all current users are converted.

The same structure can be used by other MACs such as AES-XCBC-MAC.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
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@herbertx
herbertx committed Sep 21, 2006
1 parent 055bcee commit 0796ae0
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Showing 2 changed files with 236 additions and 6 deletions.
1 change: 1 addition & 0 deletions crypto/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@ config CRYPTO_MANAGER

config CRYPTO_HMAC
bool "HMAC support"
select CRYPTO_HASH
help
HMAC: Keyed-Hashing for Message Authentication (RFC2104).
This is required for IPSec.
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241 changes: 235 additions & 6 deletions crypto/hmac.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4,22 +4,30 @@
* 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)
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
*/
#include <linux/crypto.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/slab.h>

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

struct hmac_ctx {
struct crypto_hash *child;
};

static void hash_key(struct crypto_tfm *tfm, u8 *key, unsigned int keylen)
{
Expand Down Expand Up @@ -122,3 +130,224 @@ EXPORT_SYMBOL_GPL(crypto_hmac_update);
EXPORT_SYMBOL_GPL(crypto_hmac_final);
EXPORT_SYMBOL_GPL(crypto_hmac);

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 err;

desc.tfm = tfm;
desc.flags = crypto_hash_get_flags(parent);
desc.flags &= CRYPTO_TFM_REQ_MAY_SLEEP;
sg_set_buf(&tmp, inkey, keylen);

err = crypto_hash_digest(&desc, &tmp, keylen, 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;

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

return unlikely(crypto_hash_init(&desc)) ?:
crypto_hash_update(&desc, &tmp, 1);
}

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;

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

return unlikely(crypto_hash_final(&desc, digest)) ?:
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];

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

sg_set_buf(sg1, ipad, bs);
sg1[1].page = (void *)sg;
sg1[1].length = 0;
sg_set_buf(sg2, opad, bs + ds);

return unlikely(crypto_hash_digest(&desc, sg1, nbytes + bs, digest)) ?:
crypto_hash_digest(&desc, sg2, bs + ds, out);
}

static int hmac_init_tfm(struct crypto_tfm *tfm)
{
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));

tfm = crypto_spawn_tfm(spawn);
if (IS_ERR(tfm))
return PTR_ERR(tfm);

ctx->child = crypto_hash_cast(tfm);
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(void *param, unsigned int len)
{
struct crypto_instance *inst;
struct crypto_alg *alg;

alg = crypto_get_attr_alg(param, len, CRYPTO_ALG_TYPE_HASH,
CRYPTO_ALG_TYPE_HASH_MASK | CRYPTO_ALG_ASYNC);
if (IS_ERR(alg))
return ERR_PTR(PTR_ERR(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 =
(alg->cra_flags & CRYPTO_ALG_TYPE_MASK) ==
CRYPTO_ALG_TYPE_HASH ? alg->cra_hash.digestsize :
alg->cra_digest.dia_digestsize;

inst->alg.cra_ctxsize = sizeof(struct hmac_ctx) +
ALIGN(inst->alg.cra_blocksize * 2 +
inst->alg.cra_hash.digestsize,
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");

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