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![Herbert Xu](/assets/img/avatar_default.png)
The digest size check on hash algorithms is incorrect. It's perfectly valid for hash algorithms to have a digest length longer than their block size. For example crc32c has a block size of 1 and a digest size of 4. Rather than having it lie about its block size, this patch fixes the checks to do what they really should which is to bound the digest size so that code placing the digest on the stack continue to work. HMAC however still needs to check this as it's only defined for such algorithms. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
298 lines
7.2 KiB
C
298 lines
7.2 KiB
C
/*
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* Cryptographic API.
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*
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* HMAC: Keyed-Hashing for Message Authentication (RFC2104).
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*
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* Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
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* Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
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*
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* The HMAC implementation is derived from USAGI.
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* Copyright (c) 2002 Kazunori Miyazawa <miyazawa@linux-ipv6.org> / USAGI
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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*/
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#include <crypto/algapi.h>
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#include <crypto/scatterwalk.h>
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#include <linux/err.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/scatterlist.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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struct hmac_ctx {
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struct crypto_hash *child;
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};
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static inline void *align_ptr(void *p, unsigned int align)
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{
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return (void *)ALIGN((unsigned long)p, align);
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}
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static inline struct hmac_ctx *hmac_ctx(struct crypto_hash *tfm)
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{
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return align_ptr(crypto_hash_ctx_aligned(tfm) +
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crypto_hash_blocksize(tfm) * 2 +
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crypto_hash_digestsize(tfm), sizeof(void *));
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}
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static int hmac_setkey(struct crypto_hash *parent,
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const u8 *inkey, unsigned int keylen)
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{
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int bs = crypto_hash_blocksize(parent);
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int ds = crypto_hash_digestsize(parent);
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char *ipad = crypto_hash_ctx_aligned(parent);
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char *opad = ipad + bs;
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char *digest = opad + bs;
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struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
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struct crypto_hash *tfm = ctx->child;
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unsigned int i;
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if (keylen > bs) {
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struct hash_desc desc;
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struct scatterlist tmp;
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int tmplen;
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int err;
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desc.tfm = tfm;
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desc.flags = crypto_hash_get_flags(parent);
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desc.flags &= CRYPTO_TFM_REQ_MAY_SLEEP;
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err = crypto_hash_init(&desc);
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if (err)
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return err;
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tmplen = bs * 2 + ds;
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sg_init_one(&tmp, ipad, tmplen);
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for (; keylen > tmplen; inkey += tmplen, keylen -= tmplen) {
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memcpy(ipad, inkey, tmplen);
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err = crypto_hash_update(&desc, &tmp, tmplen);
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if (err)
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return err;
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}
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if (keylen) {
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memcpy(ipad, inkey, keylen);
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err = crypto_hash_update(&desc, &tmp, keylen);
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if (err)
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return err;
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}
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err = crypto_hash_final(&desc, digest);
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if (err)
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return err;
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inkey = digest;
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keylen = ds;
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}
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memcpy(ipad, inkey, keylen);
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memset(ipad + keylen, 0, bs - keylen);
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memcpy(opad, ipad, bs);
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for (i = 0; i < bs; i++) {
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ipad[i] ^= 0x36;
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opad[i] ^= 0x5c;
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}
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return 0;
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}
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static int hmac_init(struct hash_desc *pdesc)
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{
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struct crypto_hash *parent = pdesc->tfm;
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int bs = crypto_hash_blocksize(parent);
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int ds = crypto_hash_digestsize(parent);
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char *ipad = crypto_hash_ctx_aligned(parent);
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struct hmac_ctx *ctx = align_ptr(ipad + bs * 2 + ds, sizeof(void *));
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struct hash_desc desc;
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struct scatterlist tmp;
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int err;
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desc.tfm = ctx->child;
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desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
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sg_init_one(&tmp, ipad, bs);
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err = crypto_hash_init(&desc);
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if (unlikely(err))
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return err;
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return crypto_hash_update(&desc, &tmp, bs);
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}
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static int hmac_update(struct hash_desc *pdesc,
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struct scatterlist *sg, unsigned int nbytes)
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{
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struct hmac_ctx *ctx = hmac_ctx(pdesc->tfm);
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struct hash_desc desc;
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desc.tfm = ctx->child;
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desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
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return crypto_hash_update(&desc, sg, nbytes);
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}
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static int hmac_final(struct hash_desc *pdesc, u8 *out)
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{
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struct crypto_hash *parent = pdesc->tfm;
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int bs = crypto_hash_blocksize(parent);
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int ds = crypto_hash_digestsize(parent);
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char *opad = crypto_hash_ctx_aligned(parent) + bs;
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char *digest = opad + bs;
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struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
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struct hash_desc desc;
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struct scatterlist tmp;
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int err;
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desc.tfm = ctx->child;
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desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
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sg_init_one(&tmp, opad, bs + ds);
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err = crypto_hash_final(&desc, digest);
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if (unlikely(err))
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return err;
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return crypto_hash_digest(&desc, &tmp, bs + ds, out);
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}
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static int hmac_digest(struct hash_desc *pdesc, struct scatterlist *sg,
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unsigned int nbytes, u8 *out)
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{
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struct crypto_hash *parent = pdesc->tfm;
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int bs = crypto_hash_blocksize(parent);
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int ds = crypto_hash_digestsize(parent);
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char *ipad = crypto_hash_ctx_aligned(parent);
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char *opad = ipad + bs;
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char *digest = opad + bs;
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struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
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struct hash_desc desc;
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struct scatterlist sg1[2];
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struct scatterlist sg2[1];
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int err;
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desc.tfm = ctx->child;
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desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
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sg_init_table(sg1, 2);
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sg_set_buf(sg1, ipad, bs);
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scatterwalk_sg_chain(sg1, 2, sg);
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sg_init_table(sg2, 1);
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sg_set_buf(sg2, opad, bs + ds);
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err = crypto_hash_digest(&desc, sg1, nbytes + bs, digest);
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if (unlikely(err))
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return err;
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return crypto_hash_digest(&desc, sg2, bs + ds, out);
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}
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static int hmac_init_tfm(struct crypto_tfm *tfm)
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{
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struct crypto_hash *hash;
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struct crypto_instance *inst = (void *)tfm->__crt_alg;
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struct crypto_spawn *spawn = crypto_instance_ctx(inst);
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struct hmac_ctx *ctx = hmac_ctx(__crypto_hash_cast(tfm));
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hash = crypto_spawn_hash(spawn);
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if (IS_ERR(hash))
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return PTR_ERR(hash);
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ctx->child = hash;
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return 0;
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}
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static void hmac_exit_tfm(struct crypto_tfm *tfm)
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{
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struct hmac_ctx *ctx = hmac_ctx(__crypto_hash_cast(tfm));
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crypto_free_hash(ctx->child);
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}
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static void hmac_free(struct crypto_instance *inst)
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{
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crypto_drop_spawn(crypto_instance_ctx(inst));
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kfree(inst);
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}
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static struct crypto_instance *hmac_alloc(struct rtattr **tb)
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{
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struct crypto_instance *inst;
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struct crypto_alg *alg;
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int err;
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int ds;
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err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_HASH);
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if (err)
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return ERR_PTR(err);
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alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_HASH,
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CRYPTO_ALG_TYPE_HASH_MASK);
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if (IS_ERR(alg))
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return ERR_CAST(alg);
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inst = ERR_PTR(-EINVAL);
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ds = (alg->cra_flags & CRYPTO_ALG_TYPE_MASK) ==
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CRYPTO_ALG_TYPE_HASH ? alg->cra_hash.digestsize :
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alg->cra_digest.dia_digestsize;
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if (ds > alg->cra_blocksize)
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goto out_put_alg;
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inst = crypto_alloc_instance("hmac", alg);
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if (IS_ERR(inst))
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goto out_put_alg;
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inst->alg.cra_flags = CRYPTO_ALG_TYPE_HASH;
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inst->alg.cra_priority = alg->cra_priority;
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inst->alg.cra_blocksize = alg->cra_blocksize;
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inst->alg.cra_alignmask = alg->cra_alignmask;
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inst->alg.cra_type = &crypto_hash_type;
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inst->alg.cra_hash.digestsize = ds;
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inst->alg.cra_ctxsize = sizeof(struct hmac_ctx) +
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ALIGN(inst->alg.cra_blocksize * 2 + ds,
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sizeof(void *));
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inst->alg.cra_init = hmac_init_tfm;
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inst->alg.cra_exit = hmac_exit_tfm;
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inst->alg.cra_hash.init = hmac_init;
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inst->alg.cra_hash.update = hmac_update;
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inst->alg.cra_hash.final = hmac_final;
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inst->alg.cra_hash.digest = hmac_digest;
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inst->alg.cra_hash.setkey = hmac_setkey;
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out_put_alg:
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crypto_mod_put(alg);
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return inst;
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}
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static struct crypto_template hmac_tmpl = {
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.name = "hmac",
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.alloc = hmac_alloc,
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.free = hmac_free,
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.module = THIS_MODULE,
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};
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static int __init hmac_module_init(void)
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{
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return crypto_register_template(&hmac_tmpl);
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}
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static void __exit hmac_module_exit(void)
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{
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crypto_unregister_template(&hmac_tmpl);
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}
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module_init(hmac_module_init);
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module_exit(hmac_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("HMAC hash algorithm");
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