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 <crypto/scatterwalk.h>
  21 #include <linux/err.h>
  22 #include <linux/init.h>
  23 #include <linux/kernel.h>
  24 #include <linux/module.h>
  25 #include <linux/scatterlist.h>
  26 #include <linux/slab.h>
  27 #include <linux/string.h>
  28
  29 struct hmac_ctx {
  30         struct crypto_hash *child;
  31 };
  32
  33 static inline void *align_ptr(void *p, unsigned int align)
  34 {
  35         return (void *)ALIGN((unsigned long)p, align);
  36 }
  37
  38 static inline struct hmac_ctx *hmac_ctx(struct crypto_hash *tfm)
  39 {
  40         return align_ptr(crypto_hash_ctx_aligned(tfm) +
  41                          crypto_hash_blocksize(tfm) * 2 +
  42                          crypto_hash_digestsize(tfm), sizeof(void *));
  43 }
  44
  45 static int hmac_setkey(struct crypto_hash *parent,
  46                        const u8 *inkey, unsigned int keylen)
  47 {
  48         int bs = crypto_hash_blocksize(parent);
  49         int ds = crypto_hash_digestsize(parent);
  50         char *ipad = crypto_hash_ctx_aligned(parent);
  51         char *opad = ipad + bs;
  52         char *digest = opad + bs;
  53         struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
  54         struct crypto_hash *tfm = ctx->child;
  55         unsigned int i;
  56
  57         if (keylen > bs) {
  58                 struct hash_desc desc;
  59                 struct scatterlist tmp;
  60                 int tmplen;
  61                 int err;
  62
  63                 desc.tfm = tfm;
  64                 desc.flags = crypto_hash_get_flags(parent);
  65                 desc.flags &= CRYPTO_TFM_REQ_MAY_SLEEP;
  66
  67                 err = crypto_hash_init(&desc);
  68                 if (err)
  69                         return err;
  70
  71                 tmplen = bs * 2 + ds;
  72                 sg_init_one(&tmp, ipad, tmplen);
  73
  74                 for (; keylen > tmplen; inkey += tmplen, keylen -= tmplen) {
  75                         memcpy(ipad, inkey, tmplen);
  76                         err = crypto_hash_update(&desc, &tmp, tmplen);
  77                         if (err)
  78                                 return err;
  79                 }
  80
  81                 if (keylen) {
  82                         memcpy(ipad, inkey, keylen);
  83                         err = crypto_hash_update(&desc, &tmp, keylen);
  84                         if (err)
  85                                 return err;
  86                 }
  87
  88                 err = crypto_hash_final(&desc, digest);
  89                 if (err)
  90                         return err;
  91
  92                 inkey = digest;
  93                 keylen = ds;
  94         }
  95
  96         memcpy(ipad, inkey, keylen);
  97         memset(ipad + keylen, 0, bs - keylen);
  98         memcpy(opad, ipad, bs);
  99
 100         for (i = 0; i < bs; i++) {
 101                 ipad[i] ^= 0x36;
 102                 opad[i] ^= 0x5c;
 103         }
 104
 105         return 0;
 106 }
 107
 108 static int hmac_init(struct hash_desc *pdesc)
 109 {
 110         struct crypto_hash *parent = pdesc->tfm;
 111         int bs = crypto_hash_blocksize(parent);
 112         int ds = crypto_hash_digestsize(parent);
 113         char *ipad = crypto_hash_ctx_aligned(parent);
 114         struct hmac_ctx *ctx = align_ptr(ipad + bs * 2 + ds, sizeof(void *));
 115         struct hash_desc desc;
 116         struct scatterlist tmp;
 117         int err;
 118
 119         desc.tfm = ctx->child;
 120         desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 121         sg_init_one(&tmp, ipad, bs);
 122
 123         err = crypto_hash_init(&desc);
 124         if (unlikely(err))
 125                 return err;
 126
 127         return crypto_hash_update(&desc, &tmp, bs);
 128 }
 129
 130 static int hmac_update(struct hash_desc *pdesc,
 131                        struct scatterlist *sg, unsigned int nbytes)
 132 {
 133         struct hmac_ctx *ctx = hmac_ctx(pdesc->tfm);
 134         struct hash_desc desc;
 135
 136         desc.tfm = ctx->child;
 137         desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 138
 139         return crypto_hash_update(&desc, sg, nbytes);
 140 }
 141
 142 static int hmac_final(struct hash_desc *pdesc, u8 *out)
 143 {
 144         struct crypto_hash *parent = pdesc->tfm;
 145         int bs = crypto_hash_blocksize(parent);
 146         int ds = crypto_hash_digestsize(parent);
 147         char *opad = crypto_hash_ctx_aligned(parent) + bs;
 148         char *digest = opad + bs;
 149         struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
 150         struct hash_desc desc;
 151         struct scatterlist tmp;
 152         int err;
 153
 154         desc.tfm = ctx->child;
 155         desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 156         sg_init_one(&tmp, opad, bs + ds);
 157
 158         err = crypto_hash_final(&desc, digest);
 159         if (unlikely(err))
 160                 return err;
 161
 162         return crypto_hash_digest(&desc, &tmp, bs + ds, out);
 163 }
 164
 165 static int hmac_digest(struct hash_desc *pdesc, struct scatterlist *sg,
 166                        unsigned int nbytes, u8 *out)
 167 {
 168         struct crypto_hash *parent = pdesc->tfm;
 169         int bs = crypto_hash_blocksize(parent);
 170         int ds = crypto_hash_digestsize(parent);
 171         char *ipad = crypto_hash_ctx_aligned(parent);
 172         char *opad = ipad + bs;
 173         char *digest = opad + bs;
 174         struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
 175         struct hash_desc desc;
 176         struct scatterlist sg1[2];
 177         struct scatterlist sg2[1];
 178         int err;
 179
 180         desc.tfm = ctx->child;
 181         desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 182
 183         sg_init_table(sg1, 2);
 184         sg_set_buf(sg1, ipad, bs);
 185         scatterwalk_sg_chain(sg1, 2, sg);
 186
 187         sg_init_table(sg2, 1);
 188         sg_set_buf(sg2, opad, bs + ds);
 189
 190         err = crypto_hash_digest(&desc, sg1, nbytes + bs, digest);
 191         if (unlikely(err))
 192                 return err;
 193
 194         return crypto_hash_digest(&desc, sg2, bs + ds, out);
 195 }
 196
 197 static int hmac_init_tfm(struct crypto_tfm *tfm)
 198 {
 199         struct crypto_hash *hash;
 200         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 201         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 202         struct hmac_ctx *ctx = hmac_ctx(__crypto_hash_cast(tfm));
 203
 204         hash = crypto_spawn_hash(spawn);
 205         if (IS_ERR(hash))
 206                 return PTR_ERR(hash);
 207
 208         ctx->child = hash;
 209         return 0;
 210 }
 211
 212 static void hmac_exit_tfm(struct crypto_tfm *tfm)
 213 {
 214         struct hmac_ctx *ctx = hmac_ctx(__crypto_hash_cast(tfm));
 215         crypto_free_hash(ctx->child);
 216 }
 217
 218 static void hmac_free(struct crypto_instance *inst)
 219 {
 220         crypto_drop_spawn(crypto_instance_ctx(inst));
 221         kfree(inst);
 222 }
 223
 224 static struct crypto_instance *hmac_alloc(struct rtattr **tb)
 225 {
 226         struct crypto_instance *inst;
 227         struct crypto_alg *alg;
 228         int err;
 229         int ds;
 230
 231         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_HASH);
 232         if (err)
 233                 return ERR_PTR(err);
 234
 235         alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_HASH,
 236                                   CRYPTO_ALG_TYPE_HASH_MASK);
 237         if (IS_ERR(alg))
 238                 return ERR_CAST(alg);
 239
 240         inst = ERR_PTR(-EINVAL);
 241         ds = (alg->cra_flags & CRYPTO_ALG_TYPE_MASK) ==
 242              CRYPTO_ALG_TYPE_HASH ? alg->cra_hash.digestsize :
 243                                     alg->cra_digest.dia_digestsize;
 244         if (ds > alg->cra_blocksize)
 245                 goto out_put_alg;
 246
 247         inst = crypto_alloc_instance("hmac", alg);
 248         if (IS_ERR(inst))
 249                 goto out_put_alg;
 250
 251         inst->alg.cra_flags = CRYPTO_ALG_TYPE_HASH;
 252         inst->alg.cra_priority = alg->cra_priority;
 253         inst->alg.cra_blocksize = alg->cra_blocksize;
 254         inst->alg.cra_alignmask = alg->cra_alignmask;
 255         inst->alg.cra_type = &crypto_hash_type;
 256
 257         inst->alg.cra_hash.digestsize = ds;
 258
 259         inst->alg.cra_ctxsize = sizeof(struct hmac_ctx) +
 260                                 ALIGN(inst->alg.cra_blocksize * 2 + ds,
 261                                       sizeof(void *));
 262
 263         inst->alg.cra_init = hmac_init_tfm;
 264         inst->alg.cra_exit = hmac_exit_tfm;
 265
 266         inst->alg.cra_hash.init = hmac_init;
 267         inst->alg.cra_hash.update = hmac_update;
 268         inst->alg.cra_hash.final = hmac_final;
 269         inst->alg.cra_hash.digest = hmac_digest;
 270         inst->alg.cra_hash.setkey = hmac_setkey;
 271
 272 out_put_alg:
 273         crypto_mod_put(alg);
 274         return inst;
 275 }
 276
 277 static struct crypto_template hmac_tmpl = {
 278         .name = "hmac",
 279         .alloc = hmac_alloc,
 280         .free = hmac_free,
 281         .module = THIS_MODULE,
 282 };
 283
 284 static int __init hmac_module_init(void)
 285 {
 286         return crypto_register_template(&hmac_tmpl);
 287 }
 288
 289 static void __exit hmac_module_exit(void)
 290 {
 291         crypto_unregister_template(&hmac_tmpl);
 292 }
 293
 294 module_init(hmac_module_init);
 295 module_exit(hmac_module_exit);
 296
 297 MODULE_LICENSE("GPL");
 298 MODULE_DESCRIPTION("HMAC hash algorithm");