crypto/hmac.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Cryptographic API.
   4  *
   5  * HMAC: Keyed-Hashing for Message Authentication (RFC2104).
   6  *
   7  * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
   8  * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
   9  *
  10  * The HMAC implementation is derived from USAGI.
  11  * Copyright (c) 2002 Kazunori Miyazawa <miyazawa@linux-ipv6.org> / USAGI
  12  */
  13
  14 #include <crypto/hmac.h>
  15 #include <crypto/internal/hash.h>
  16 #include <crypto/scatterwalk.h>
  17 #include <linux/err.h>
  18 #include <linux/init.h>
  19 #include <linux/kernel.h>
  20 #include <linux/module.h>
  21 #include <linux/scatterlist.h>
  22 #include <linux/string.h>
  23
  24 struct hmac_ctx {
  25         struct crypto_shash *hash;
  26 };
  27
  28 static inline void *align_ptr(void *p, unsigned int align)
  29 {
  30         return (void *)ALIGN((unsigned long)p, align);
  31 }
  32
  33 static inline struct hmac_ctx *hmac_ctx(struct crypto_shash *tfm)
  34 {
  35         return align_ptr(crypto_shash_ctx_aligned(tfm) +
  36                          crypto_shash_statesize(tfm) * 2,
  37                          crypto_tfm_ctx_alignment());
  38 }
  39
  40 static int hmac_setkey(struct crypto_shash *parent,
  41                        const u8 *inkey, unsigned int keylen)
  42 {
  43         int bs = crypto_shash_blocksize(parent);
  44         int ds = crypto_shash_digestsize(parent);
  45         int ss = crypto_shash_statesize(parent);
  46         char *ipad = crypto_shash_ctx_aligned(parent);
  47         char *opad = ipad + ss;
  48         struct hmac_ctx *ctx = align_ptr(opad + ss,
  49                                          crypto_tfm_ctx_alignment());
  50         struct crypto_shash *hash = ctx->hash;
  51         SHASH_DESC_ON_STACK(shash, hash);
  52         unsigned int i;
  53
  54         shash->tfm = hash;
  55
  56         if (keylen > bs) {
  57                 int err;
  58
  59                 err = crypto_shash_digest(shash, inkey, keylen, ipad);
  60                 if (err)
  61                         return err;
  62
  63                 keylen = ds;
  64         } else
  65                 memcpy(ipad, inkey, keylen);
  66
  67         memset(ipad + keylen, 0, bs - keylen);
  68         memcpy(opad, ipad, bs);
  69
  70         for (i = 0; i < bs; i++) {
  71                 ipad[i] ^= HMAC_IPAD_VALUE;
  72                 opad[i] ^= HMAC_OPAD_VALUE;
  73         }
  74
  75         return crypto_shash_init(shash) ?:
  76                crypto_shash_update(shash, ipad, bs) ?:
  77                crypto_shash_export(shash, ipad) ?:
  78                crypto_shash_init(shash) ?:
  79                crypto_shash_update(shash, opad, bs) ?:
  80                crypto_shash_export(shash, opad);
  81 }
  82
  83 static int hmac_export(struct shash_desc *pdesc, void *out)
  84 {
  85         struct shash_desc *desc = shash_desc_ctx(pdesc);
  86
  87         return crypto_shash_export(desc, out);
  88 }
  89
  90 static int hmac_import(struct shash_desc *pdesc, const void *in)
  91 {
  92         struct shash_desc *desc = shash_desc_ctx(pdesc);
  93         struct hmac_ctx *ctx = hmac_ctx(pdesc->tfm);
  94
  95         desc->tfm = ctx->hash;
  96
  97         return crypto_shash_import(desc, in);
  98 }
  99
 100 static int hmac_init(struct shash_desc *pdesc)
 101 {
 102         return hmac_import(pdesc, crypto_shash_ctx_aligned(pdesc->tfm));
 103 }
 104
 105 static int hmac_update(struct shash_desc *pdesc,
 106                        const u8 *data, unsigned int nbytes)
 107 {
 108         struct shash_desc *desc = shash_desc_ctx(pdesc);
 109
 110         return crypto_shash_update(desc, data, nbytes);
 111 }
 112
 113 static int hmac_final(struct shash_desc *pdesc, u8 *out)
 114 {
 115         struct crypto_shash *parent = pdesc->tfm;
 116         int ds = crypto_shash_digestsize(parent);
 117         int ss = crypto_shash_statesize(parent);
 118         char *opad = crypto_shash_ctx_aligned(parent) + ss;
 119         struct shash_desc *desc = shash_desc_ctx(pdesc);
 120
 121         return crypto_shash_final(desc, out) ?:
 122                crypto_shash_import(desc, opad) ?:
 123                crypto_shash_finup(desc, out, ds, out);
 124 }
 125
 126 static int hmac_finup(struct shash_desc *pdesc, const u8 *data,
 127                       unsigned int nbytes, u8 *out)
 128 {
 129
 130         struct crypto_shash *parent = pdesc->tfm;
 131         int ds = crypto_shash_digestsize(parent);
 132         int ss = crypto_shash_statesize(parent);
 133         char *opad = crypto_shash_ctx_aligned(parent) + ss;
 134         struct shash_desc *desc = shash_desc_ctx(pdesc);
 135
 136         return crypto_shash_finup(desc, data, nbytes, out) ?:
 137                crypto_shash_import(desc, opad) ?:
 138                crypto_shash_finup(desc, out, ds, out);
 139 }
 140
 141 static int hmac_init_tfm(struct crypto_tfm *tfm)
 142 {
 143         struct crypto_shash *parent = __crypto_shash_cast(tfm);
 144         struct crypto_shash *hash;
 145         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 146         struct crypto_shash_spawn *spawn = crypto_instance_ctx(inst);
 147         struct hmac_ctx *ctx = hmac_ctx(parent);
 148
 149         hash = crypto_spawn_shash(spawn);
 150         if (IS_ERR(hash))
 151                 return PTR_ERR(hash);
 152
 153         parent->descsize = sizeof(struct shash_desc) +
 154                            crypto_shash_descsize(hash);
 155         if (WARN_ON(parent->descsize > HASH_MAX_DESCSIZE)) {
 156                 crypto_free_shash(hash);
 157                 return -EINVAL;
 158         }
 159
 160         ctx->hash = hash;
 161         return 0;
 162 }
 163
 164 static void hmac_exit_tfm(struct crypto_tfm *tfm)
 165 {
 166         struct hmac_ctx *ctx = hmac_ctx(__crypto_shash_cast(tfm));
 167         crypto_free_shash(ctx->hash);
 168 }
 169
 170 static int hmac_create(struct crypto_template *tmpl, struct rtattr **tb)
 171 {
 172         struct shash_instance *inst;
 173         struct crypto_alg *alg;
 174         struct shash_alg *salg;
 175         int err;
 176         int ds;
 177         int ss;
 178
 179         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH);
 180         if (err)
 181                 return err;
 182
 183         salg = shash_attr_alg(tb[1], 0, 0);
 184         if (IS_ERR(salg))
 185                 return PTR_ERR(salg);
 186         alg = &salg->base;
 187
 188         /* The underlying hash algorithm must be unkeyed */
 189         err = -EINVAL;
 190         if (crypto_shash_alg_has_setkey(salg))
 191                 goto out_put_alg;
 192
 193         ds = salg->digestsize;
 194         ss = salg->statesize;
 195         if (ds > alg->cra_blocksize ||
 196             ss < alg->cra_blocksize)
 197                 goto out_put_alg;
 198
 199         inst = shash_alloc_instance("hmac", alg);
 200         err = PTR_ERR(inst);
 201         if (IS_ERR(inst))
 202                 goto out_put_alg;
 203
 204         err = crypto_init_shash_spawn(shash_instance_ctx(inst), salg,
 205                                       shash_crypto_instance(inst));
 206         if (err)
 207                 goto out_free_inst;
 208
 209         inst->alg.base.cra_priority = alg->cra_priority;
 210         inst->alg.base.cra_blocksize = alg->cra_blocksize;
 211         inst->alg.base.cra_alignmask = alg->cra_alignmask;
 212
 213         ss = ALIGN(ss, alg->cra_alignmask + 1);
 214         inst->alg.digestsize = ds;
 215         inst->alg.statesize = ss;
 216
 217         inst->alg.base.cra_ctxsize = sizeof(struct hmac_ctx) +
 218                                      ALIGN(ss * 2, crypto_tfm_ctx_alignment());
 219
 220         inst->alg.base.cra_init = hmac_init_tfm;
 221         inst->alg.base.cra_exit = hmac_exit_tfm;
 222
 223         inst->alg.init = hmac_init;
 224         inst->alg.update = hmac_update;
 225         inst->alg.final = hmac_final;
 226         inst->alg.finup = hmac_finup;
 227         inst->alg.export = hmac_export;
 228         inst->alg.import = hmac_import;
 229         inst->alg.setkey = hmac_setkey;
 230
 231         err = shash_register_instance(tmpl, inst);
 232         if (err) {
 233 out_free_inst:
 234                 shash_free_instance(shash_crypto_instance(inst));
 235         }
 236
 237 out_put_alg:
 238         crypto_mod_put(alg);
 239         return err;
 240 }
 241
 242 static struct crypto_template hmac_tmpl = {
 243         .name = "hmac",
 244         .create = hmac_create,
 245         .free = shash_free_instance,
 246         .module = THIS_MODULE,
 247 };
 248
 249 static int __init hmac_module_init(void)
 250 {
 251         return crypto_register_template(&hmac_tmpl);
 252 }
 253
 254 static void __exit hmac_module_exit(void)
 255 {
 256         crypto_unregister_template(&hmac_tmpl);
 257 }
 258
 259 subsys_initcall(hmac_module_init);
 260 module_exit(hmac_module_exit);
 261
 262 MODULE_LICENSE("GPL");
 263 MODULE_DESCRIPTION("HMAC hash algorithm");
 264 MODULE_ALIAS_CRYPTO("hmac");