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/hmac.h>
  20 #include <crypto/internal/hash.h>
  21 #include <crypto/scatterwalk.h>
  22 #include <linux/err.h>
  23 #include <linux/init.h>
  24 #include <linux/kernel.h>
  25 #include <linux/module.h>
  26 #include <linux/scatterlist.h>
  27 #include <linux/string.h>
  28
  29 struct hmac_ctx {
  30         struct crypto_shash *hash;
  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_shash *tfm)
  39 {
  40         return align_ptr(crypto_shash_ctx_aligned(tfm) +
  41                          crypto_shash_statesize(tfm) * 2,
  42                          crypto_tfm_ctx_alignment());
  43 }
  44
  45 static int hmac_setkey(struct crypto_shash *parent,
  46                        const u8 *inkey, unsigned int keylen)
  47 {
  48         int bs = crypto_shash_blocksize(parent);
  49         int ds = crypto_shash_digestsize(parent);
  50         int ss = crypto_shash_statesize(parent);
  51         char *ipad = crypto_shash_ctx_aligned(parent);
  52         char *opad = ipad + ss;
  53         struct hmac_ctx *ctx = align_ptr(opad + ss,
  54                                          crypto_tfm_ctx_alignment());
  55         struct crypto_shash *hash = ctx->hash;
  56         SHASH_DESC_ON_STACK(shash, hash);
  57         unsigned int i;
  58
  59         shash->tfm = hash;
  60         shash->flags = crypto_shash_get_flags(parent)
  61                 & CRYPTO_TFM_REQ_MAY_SLEEP;
  62
  63         if (keylen > bs) {
  64                 int err;
  65
  66                 err = crypto_shash_digest(shash, inkey, keylen, ipad);
  67                 if (err)
  68                         return err;
  69
  70                 keylen = ds;
  71         } else
  72                 memcpy(ipad, inkey, keylen);
  73
  74         memset(ipad + keylen, 0, bs - keylen);
  75         memcpy(opad, ipad, bs);
  76
  77         for (i = 0; i < bs; i++) {
  78                 ipad[i] ^= HMAC_IPAD_VALUE;
  79                 opad[i] ^= HMAC_OPAD_VALUE;
  80         }
  81
  82         return crypto_shash_init(shash) ?:
  83                crypto_shash_update(shash, ipad, bs) ?:
  84                crypto_shash_export(shash, ipad) ?:
  85                crypto_shash_init(shash) ?:
  86                crypto_shash_update(shash, opad, bs) ?:
  87                crypto_shash_export(shash, opad);
  88 }
  89
  90 static int hmac_export(struct shash_desc *pdesc, void *out)
  91 {
  92         struct shash_desc *desc = shash_desc_ctx(pdesc);
  93
  94         desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
  95
  96         return crypto_shash_export(desc, out);
  97 }
  98
  99 static int hmac_import(struct shash_desc *pdesc, const void *in)
 100 {
 101         struct shash_desc *desc = shash_desc_ctx(pdesc);
 102         struct hmac_ctx *ctx = hmac_ctx(pdesc->tfm);
 103
 104         desc->tfm = ctx->hash;
 105         desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 106
 107         return crypto_shash_import(desc, in);
 108 }
 109
 110 static int hmac_init(struct shash_desc *pdesc)
 111 {
 112         return hmac_import(pdesc, crypto_shash_ctx_aligned(pdesc->tfm));
 113 }
 114
 115 static int hmac_update(struct shash_desc *pdesc,
 116                        const u8 *data, unsigned int nbytes)
 117 {
 118         struct shash_desc *desc = shash_desc_ctx(pdesc);
 119
 120         desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 121
 122         return crypto_shash_update(desc, data, nbytes);
 123 }
 124
 125 static int hmac_final(struct shash_desc *pdesc, u8 *out)
 126 {
 127         struct crypto_shash *parent = pdesc->tfm;
 128         int ds = crypto_shash_digestsize(parent);
 129         int ss = crypto_shash_statesize(parent);
 130         char *opad = crypto_shash_ctx_aligned(parent) + ss;
 131         struct shash_desc *desc = shash_desc_ctx(pdesc);
 132
 133         desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 134
 135         return crypto_shash_final(desc, out) ?:
 136                crypto_shash_import(desc, opad) ?:
 137                crypto_shash_finup(desc, out, ds, out);
 138 }
 139
 140 static int hmac_finup(struct shash_desc *pdesc, const u8 *data,
 141                       unsigned int nbytes, u8 *out)
 142 {
 143
 144         struct crypto_shash *parent = pdesc->tfm;
 145         int ds = crypto_shash_digestsize(parent);
 146         int ss = crypto_shash_statesize(parent);
 147         char *opad = crypto_shash_ctx_aligned(parent) + ss;
 148         struct shash_desc *desc = shash_desc_ctx(pdesc);
 149
 150         desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 151
 152         return crypto_shash_finup(desc, data, nbytes, out) ?:
 153                crypto_shash_import(desc, opad) ?:
 154                crypto_shash_finup(desc, out, ds, out);
 155 }
 156
 157 static int hmac_init_tfm(struct crypto_tfm *tfm)
 158 {
 159         struct crypto_shash *parent = __crypto_shash_cast(tfm);
 160         struct crypto_shash *hash;
 161         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 162         struct crypto_shash_spawn *spawn = crypto_instance_ctx(inst);
 163         struct hmac_ctx *ctx = hmac_ctx(parent);
 164
 165         hash = crypto_spawn_shash(spawn);
 166         if (IS_ERR(hash))
 167                 return PTR_ERR(hash);
 168
 169         parent->descsize = sizeof(struct shash_desc) +
 170                            crypto_shash_descsize(hash);
 171
 172         ctx->hash = hash;
 173         return 0;
 174 }
 175
 176 static void hmac_exit_tfm(struct crypto_tfm *tfm)
 177 {
 178         struct hmac_ctx *ctx = hmac_ctx(__crypto_shash_cast(tfm));
 179         crypto_free_shash(ctx->hash);
 180 }
 181
 182 static int hmac_create(struct crypto_template *tmpl, struct rtattr **tb)
 183 {
 184         struct shash_instance *inst;
 185         struct crypto_alg *alg;
 186         struct shash_alg *salg;
 187         int err;
 188         int ds;
 189         int ss;
 190
 191         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH);
 192         if (err)
 193                 return err;
 194
 195         salg = shash_attr_alg(tb[1], 0, 0);
 196         if (IS_ERR(salg))
 197                 return PTR_ERR(salg);
 198         alg = &salg->base;
 199
 200         /* The underlying hash algorithm must be unkeyed */
 201         err = -EINVAL;
 202         if (crypto_shash_alg_has_setkey(salg))
 203                 goto out_put_alg;
 204
 205         ds = salg->digestsize;
 206         ss = salg->statesize;
 207         if (ds > alg->cra_blocksize ||
 208             ss < alg->cra_blocksize)
 209                 goto out_put_alg;
 210
 211         inst = shash_alloc_instance("hmac", alg);
 212         err = PTR_ERR(inst);
 213         if (IS_ERR(inst))
 214                 goto out_put_alg;
 215
 216         err = crypto_init_shash_spawn(shash_instance_ctx(inst), salg,
 217                                       shash_crypto_instance(inst));
 218         if (err)
 219                 goto out_free_inst;
 220
 221         inst->alg.base.cra_priority = alg->cra_priority;
 222         inst->alg.base.cra_blocksize = alg->cra_blocksize;
 223         inst->alg.base.cra_alignmask = alg->cra_alignmask;
 224
 225         ss = ALIGN(ss, alg->cra_alignmask + 1);
 226         inst->alg.digestsize = ds;
 227         inst->alg.statesize = ss;
 228
 229         inst->alg.base.cra_ctxsize = sizeof(struct hmac_ctx) +
 230                                      ALIGN(ss * 2, crypto_tfm_ctx_alignment());
 231
 232         inst->alg.base.cra_init = hmac_init_tfm;
 233         inst->alg.base.cra_exit = hmac_exit_tfm;
 234
 235         inst->alg.init = hmac_init;
 236         inst->alg.update = hmac_update;
 237         inst->alg.final = hmac_final;
 238         inst->alg.finup = hmac_finup;
 239         inst->alg.export = hmac_export;
 240         inst->alg.import = hmac_import;
 241         inst->alg.setkey = hmac_setkey;
 242
 243         err = shash_register_instance(tmpl, inst);
 244         if (err) {
 245 out_free_inst:
 246                 shash_free_instance(shash_crypto_instance(inst));
 247         }
 248
 249 out_put_alg:
 250         crypto_mod_put(alg);
 251         return err;
 252 }
 253
 254 static struct crypto_template hmac_tmpl = {
 255         .name = "hmac",
 256         .create = hmac_create,
 257         .free = shash_free_instance,
 258         .module = THIS_MODULE,
 259 };
 260
 261 static int __init hmac_module_init(void)
 262 {
 263         return crypto_register_template(&hmac_tmpl);
 264 }
 265
 266 static void __exit hmac_module_exit(void)
 267 {
 268         crypto_unregister_template(&hmac_tmpl);
 269 }
 270
 271 module_init(hmac_module_init);
 272 module_exit(hmac_module_exit);
 273
 274 MODULE_LICENSE("GPL");
 275 MODULE_DESCRIPTION("HMAC hash algorithm");
 276 MODULE_ALIAS_CRYPTO("hmac");