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