crypto/hmac.c

   1 /*
   2  * Cryptographic API.
   3  *
   4  * HMAC: Keyed-Hashing for Message Authentication (RFC2104).
   5  *
   6  * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
   7  * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
   8  *
   9  * The HMAC implementation is derived from USAGI.
  10  * Copyright (c) 2002 Kazunori Miyazawa <miyazawa@linux-ipv6.org> / USAGI
  11  *
  12  * This program is free software; you can redistribute it and/or modify it
  13  * under the terms of the GNU General Public License as published by the Free
  14  * Software Foundation; either version 2 of the License, or (at your option)
  15  * any later version.
  16  *
  17  */
  18
  19 #include <crypto/algapi.h>
  20 #include <linux/err.h>
  21 #include <linux/init.h>
  22 #include <linux/kernel.h>
  23 #include <linux/module.h>
  24 #include <linux/scatterlist.h>
  25 #include <linux/slab.h>
  26 #include <linux/string.h>
  27
  28 struct hmac_ctx {
  29         struct crypto_hash *child;
  30 };
  31
  32 static inline void *align_ptr(void *p, unsigned int align)
  33 {
  34         return (void *)ALIGN((unsigned long)p, align);
  35 }
  36
  37 static inline struct hmac_ctx *hmac_ctx(struct crypto_hash *tfm)
  38 {
  39         return align_ptr(crypto_hash_ctx_aligned(tfm) +
  40                          crypto_hash_blocksize(tfm) * 2 +
  41                          crypto_hash_digestsize(tfm), sizeof(void *));
  42 }
  43
  44 static int hmac_setkey(struct crypto_hash *parent,
  45                        const u8 *inkey, unsigned int keylen)
  46 {
  47         int bs = crypto_hash_blocksize(parent);
  48         int ds = crypto_hash_digestsize(parent);
  49         char *ipad = crypto_hash_ctx_aligned(parent);
  50         char *opad = ipad + bs;
  51         char *digest = opad + bs;
  52         struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
  53         struct crypto_hash *tfm = ctx->child;
  54         unsigned int i;
  55
  56         if (keylen > bs) {
  57                 struct hash_desc desc;
  58                 struct scatterlist tmp;
  59                 int err;
  60
  61                 desc.tfm = tfm;
  62                 desc.flags = crypto_hash_get_flags(parent);
  63                 desc.flags &= CRYPTO_TFM_REQ_MAY_SLEEP;
  64                 sg_set_buf(&tmp, inkey, keylen);
  65
  66                 err = crypto_hash_digest(&desc, &tmp, keylen, digest);
  67                 if (err)
  68                         return err;
  69
  70                 inkey = digest;
  71                 keylen = ds;
  72         }
  73
  74         memcpy(ipad, inkey, keylen);
  75         memset(ipad + keylen, 0, bs - keylen);
  76         memcpy(opad, ipad, bs);
  77
  78         for (i = 0; i < bs; i++) {
  79                 ipad[i] ^= 0x36;
  80                 opad[i] ^= 0x5c;
  81         }
  82
  83         return 0;
  84 }
  85
  86 static int hmac_init(struct hash_desc *pdesc)
  87 {
  88         struct crypto_hash *parent = pdesc->tfm;
  89         int bs = crypto_hash_blocksize(parent);
  90         int ds = crypto_hash_digestsize(parent);
  91         char *ipad = crypto_hash_ctx_aligned(parent);
  92         struct hmac_ctx *ctx = align_ptr(ipad + bs * 2 + ds, sizeof(void *));
  93         struct hash_desc desc;
  94         struct scatterlist tmp;
  95         int err;
  96
  97         desc.tfm = ctx->child;
  98         desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
  99         sg_set_buf(&tmp, ipad, bs);
 100
 101         err = crypto_hash_init(&desc);
 102         if (unlikely(err))
 103                 return err;
 104
 105         return crypto_hash_update(&desc, &tmp, bs);
 106 }
 107
 108 static int hmac_update(struct hash_desc *pdesc,
 109                        struct scatterlist *sg, unsigned int nbytes)
 110 {
 111         struct hmac_ctx *ctx = hmac_ctx(pdesc->tfm);
 112         struct hash_desc desc;
 113
 114         desc.tfm = ctx->child;
 115         desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 116
 117         return crypto_hash_update(&desc, sg, nbytes);
 118 }
 119
 120 static int hmac_final(struct hash_desc *pdesc, u8 *out)
 121 {
 122         struct crypto_hash *parent = pdesc->tfm;
 123         int bs = crypto_hash_blocksize(parent);
 124         int ds = crypto_hash_digestsize(parent);
 125         char *opad = crypto_hash_ctx_aligned(parent) + bs;
 126         char *digest = opad + bs;
 127         struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
 128         struct hash_desc desc;
 129         struct scatterlist tmp;
 130         int err;
 131
 132         desc.tfm = ctx->child;
 133         desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 134         sg_set_buf(&tmp, opad, bs + ds);
 135
 136         err = crypto_hash_final(&desc, digest);
 137         if (unlikely(err))
 138                 return err;
 139
 140         return crypto_hash_digest(&desc, &tmp, bs + ds, out);
 141 }
 142
 143 static int hmac_digest(struct hash_desc *pdesc, struct scatterlist *sg,
 144                        unsigned int nbytes, u8 *out)
 145 {
 146         struct crypto_hash *parent = pdesc->tfm;
 147         int bs = crypto_hash_blocksize(parent);
 148         int ds = crypto_hash_digestsize(parent);
 149         char *ipad = crypto_hash_ctx_aligned(parent);
 150         char *opad = ipad + bs;
 151         char *digest = opad + bs;
 152         struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
 153         struct hash_desc desc;
 154         struct scatterlist sg1[2];
 155         struct scatterlist sg2[1];
 156         int err;
 157
 158         desc.tfm = ctx->child;
 159         desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 160
 161         sg_set_buf(sg1, ipad, bs);
 162         sg1[1].page = (void *)sg;
 163         sg1[1].length = 0;
 164         sg_set_buf(sg2, opad, bs + ds);
 165
 166         err = crypto_hash_digest(&desc, sg1, nbytes + bs, digest);
 167         if (unlikely(err))
 168                 return err;
 169
 170         return crypto_hash_digest(&desc, sg2, bs + ds, out);
 171 }
 172
 173 static int hmac_init_tfm(struct crypto_tfm *tfm)
 174 {
 175         struct crypto_hash *hash;
 176         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 177         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 178         struct hmac_ctx *ctx = hmac_ctx(__crypto_hash_cast(tfm));
 179
 180         hash = crypto_spawn_hash(spawn);
 181         if (IS_ERR(hash))
 182                 return PTR_ERR(hash);
 183
 184         ctx->child = hash;
 185         return 0;
 186 }
 187
 188 static void hmac_exit_tfm(struct crypto_tfm *tfm)
 189 {
 190         struct hmac_ctx *ctx = hmac_ctx(__crypto_hash_cast(tfm));
 191         crypto_free_hash(ctx->child);
 192 }
 193
 194 static void hmac_free(struct crypto_instance *inst)
 195 {
 196         crypto_drop_spawn(crypto_instance_ctx(inst));
 197         kfree(inst);
 198 }
 199
 200 static struct crypto_instance *hmac_alloc(void *param, unsigned int len)
 201 {
 202         struct crypto_instance *inst;
 203         struct crypto_alg *alg;
 204
 205         alg = crypto_get_attr_alg(param, len, CRYPTO_ALG_TYPE_HASH,
 206                                   CRYPTO_ALG_TYPE_HASH_MASK | CRYPTO_ALG_ASYNC);
 207         if (IS_ERR(alg))
 208                 return ERR_PTR(PTR_ERR(alg));
 209
 210         inst = crypto_alloc_instance("hmac", alg);
 211         if (IS_ERR(inst))
 212                 goto out_put_alg;
 213
 214         inst->alg.cra_flags = CRYPTO_ALG_TYPE_HASH;
 215         inst->alg.cra_priority = alg->cra_priority;
 216         inst->alg.cra_blocksize = alg->cra_blocksize;
 217         inst->alg.cra_alignmask = alg->cra_alignmask;
 218         inst->alg.cra_type = &crypto_hash_type;
 219
 220         inst->alg.cra_hash.digestsize =
 221                 (alg->cra_flags & CRYPTO_ALG_TYPE_MASK) ==
 222                 CRYPTO_ALG_TYPE_HASH ? alg->cra_hash.digestsize :
 223                                        alg->cra_digest.dia_digestsize;
 224
 225         inst->alg.cra_ctxsize = sizeof(struct hmac_ctx) +
 226                                 ALIGN(inst->alg.cra_blocksize * 2 +
 227                                       inst->alg.cra_hash.digestsize,
 228                                       sizeof(void *));
 229
 230         inst->alg.cra_init = hmac_init_tfm;
 231         inst->alg.cra_exit = hmac_exit_tfm;
 232
 233         inst->alg.cra_hash.init = hmac_init;
 234         inst->alg.cra_hash.update = hmac_update;
 235         inst->alg.cra_hash.final = hmac_final;
 236         inst->alg.cra_hash.digest = hmac_digest;
 237         inst->alg.cra_hash.setkey = hmac_setkey;
 238
 239 out_put_alg:
 240         crypto_mod_put(alg);
 241         return inst;
 242 }
 243
 244 static struct crypto_template hmac_tmpl = {
 245         .name = "hmac",
 246         .alloc = hmac_alloc,
 247         .free = hmac_free,
 248         .module = THIS_MODULE,
 249 };
 250
 251 static int __init hmac_module_init(void)
 252 {
 253         return crypto_register_template(&hmac_tmpl);
 254 }
 255
 256 static void __exit hmac_module_exit(void)
 257 {
 258         crypto_unregister_template(&hmac_tmpl);
 259 }
 260
 261 module_init(hmac_module_init);
 262 module_exit(hmac_module_exit);
 263
 264 MODULE_LICENSE("GPL");
 265 MODULE_DESCRIPTION("HMAC hash algorithm");