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/internal/hash.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 shash_desc *desc;
  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_blocksize(tfm) * 2 +
  42                          crypto_shash_digestsize(tfm),
  43                          crypto_tfm_ctx_alignment());
  44 }
  45
  46 static int hmac_setkey(struct crypto_shash *parent,
  47                        const u8 *inkey, unsigned int keylen)
  48 {
  49         int bs = crypto_shash_blocksize(parent);
  50         int ds = crypto_shash_digestsize(parent);
  51         char *ipad = crypto_shash_ctx_aligned(parent);
  52         char *opad = ipad + bs;
  53         char *digest = opad + bs;
  54         struct hmac_ctx *ctx = align_ptr(digest + ds,
  55                                          crypto_tfm_ctx_alignment());
  56         unsigned int i;
  57
  58         if (keylen > bs) {
  59                 int err;
  60
  61                 ctx->desc->flags = crypto_shash_get_flags(parent) &
  62                                    CRYPTO_TFM_REQ_MAY_SLEEP;
  63
  64                 err = crypto_shash_digest(ctx->desc, inkey, keylen, digest);
  65                 if (err)
  66                         return err;
  67
  68                 inkey = digest;
  69                 keylen = ds;
  70         }
  71
  72         memcpy(ipad, inkey, keylen);
  73         memset(ipad + keylen, 0, bs - keylen);
  74         memcpy(opad, ipad, bs);
  75
  76         for (i = 0; i < bs; i++) {
  77                 ipad[i] ^= 0x36;
  78                 opad[i] ^= 0x5c;
  79         }
  80
  81         return 0;
  82 }
  83
  84 static int hmac_init(struct shash_desc *pdesc)
  85 {
  86         struct crypto_shash *parent = pdesc->tfm;
  87         int bs = crypto_shash_blocksize(parent);
  88         int ds = crypto_shash_digestsize(parent);
  89         char *ipad = crypto_shash_ctx_aligned(parent);
  90         struct hmac_ctx *ctx = align_ptr(ipad + bs * 2 + ds,
  91                                          crypto_tfm_ctx_alignment());
  92         struct shash_desc *desc = shash_desc_ctx(pdesc);
  93
  94         desc->tfm = ctx->desc->tfm;
  95         desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
  96
  97         return crypto_shash_init(desc) ?:
  98                crypto_shash_update(desc, ipad, bs);
  99 }
 100
 101 static int hmac_update(struct shash_desc *pdesc,
 102                        const u8 *data, unsigned int nbytes)
 103 {
 104         struct shash_desc *desc = shash_desc_ctx(pdesc);
 105
 106         desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 107
 108         return crypto_shash_update(desc, data, nbytes);
 109 }
 110
 111 static int hmac_final(struct shash_desc *pdesc, u8 *out)
 112 {
 113         struct crypto_shash *parent = pdesc->tfm;
 114         int bs = crypto_shash_blocksize(parent);
 115         int ds = crypto_shash_digestsize(parent);
 116         char *opad = crypto_shash_ctx_aligned(parent) + bs;
 117         char *digest = opad + bs;
 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_final(desc, digest) ?:
 123                crypto_shash_digest(desc, opad, bs + 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 bs = crypto_shash_blocksize(parent);
 132         int ds = crypto_shash_digestsize(parent);
 133         char *opad = crypto_shash_ctx_aligned(parent) + bs;
 134         char *digest = opad + bs;
 135         struct shash_desc *desc = shash_desc_ctx(pdesc);
 136
 137         desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 138
 139         return crypto_shash_finup(desc, data, nbytes, digest) ?:
 140                crypto_shash_digest(desc, opad, bs + ds, out);
 141 }
 142
 143 static int hmac_init_tfm(struct crypto_tfm *tfm)
 144 {
 145         struct crypto_shash *parent = __crypto_shash_cast(tfm);
 146         struct crypto_shash *hash;
 147         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 148         struct crypto_shash_spawn *spawn = crypto_instance_ctx(inst);
 149         struct hmac_ctx *ctx = hmac_ctx(parent);
 150
 151         hash = crypto_spawn_shash(spawn);
 152         if (IS_ERR(hash))
 153                 return PTR_ERR(hash);
 154
 155         parent->descsize = sizeof(struct shash_desc) +
 156                            crypto_shash_descsize(hash);
 157
 158         ctx->desc = kmalloc(parent->descsize, GFP_KERNEL);
 159         if (!ctx->desc) {
 160                 crypto_free_shash(hash);
 161                 return -ENOMEM;
 162         }
 163
 164         ctx->desc->tfm = hash;
 165         return 0;
 166 }
 167
 168 static void hmac_exit_tfm(struct crypto_tfm *tfm)
 169 {
 170         struct hmac_ctx *ctx = hmac_ctx(__crypto_shash_cast(tfm));
 171         crypto_free_shash(ctx->desc->tfm);
 172         kzfree(ctx->desc);
 173 }
 174
 175 static int hmac_create(struct crypto_template *tmpl, struct rtattr **tb)
 176 {
 177         struct shash_instance *inst;
 178         struct crypto_alg *alg;
 179         struct shash_alg *salg;
 180         int err;
 181         int ds;
 182
 183         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH);
 184         if (err)
 185                 return err;
 186
 187         salg = shash_attr_alg(tb[1], 0, 0);
 188         if (IS_ERR(salg))
 189                 return PTR_ERR(salg);
 190
 191         err = -EINVAL;
 192         ds = salg->digestsize;
 193         alg = &salg->base;
 194         if (ds > alg->cra_blocksize)
 195                 goto out_put_alg;
 196
 197         inst = shash_alloc_instance("hmac", alg);
 198         err = PTR_ERR(inst);
 199         if (IS_ERR(inst))
 200                 goto out_put_alg;
 201
 202         err = crypto_init_shash_spawn(shash_instance_ctx(inst), salg,
 203                                       shash_crypto_instance(inst));
 204         if (err)
 205                 goto out_free_inst;
 206
 207         inst->alg.base.cra_priority = alg->cra_priority;
 208         inst->alg.base.cra_blocksize = alg->cra_blocksize;
 209         inst->alg.base.cra_alignmask = alg->cra_alignmask;
 210
 211         inst->alg.digestsize = ds;
 212
 213         inst->alg.base.cra_ctxsize = sizeof(struct hmac_ctx) +
 214                                      ALIGN(alg->cra_blocksize * 2 + ds,
 215                                            crypto_tfm_ctx_alignment());
 216
 217         inst->alg.base.cra_init = hmac_init_tfm;
 218         inst->alg.base.cra_exit = hmac_exit_tfm;
 219
 220         inst->alg.init = hmac_init;
 221         inst->alg.update = hmac_update;
 222         inst->alg.final = hmac_final;
 223         inst->alg.finup = hmac_finup;
 224         inst->alg.setkey = hmac_setkey;
 225
 226         err = shash_register_instance(tmpl, inst);
 227         if (err) {
 228 out_free_inst:
 229                 shash_free_instance(shash_crypto_instance(inst));
 230         }
 231
 232 out_put_alg:
 233         crypto_mod_put(alg);
 234         return err;
 235 }
 236
 237 static struct crypto_template hmac_tmpl = {
 238         .name = "hmac",
 239         .create = hmac_create,
 240         .free = shash_free_instance,
 241         .module = THIS_MODULE,
 242 };
 243
 244 static int __init hmac_module_init(void)
 245 {
 246         return crypto_register_template(&hmac_tmpl);
 247 }
 248
 249 static void __exit hmac_module_exit(void)
 250 {
 251         crypto_unregister_template(&hmac_tmpl);
 252 }
 253
 254 module_init(hmac_module_init);
 255 module_exit(hmac_module_exit);
 256
 257 MODULE_LICENSE("GPL");
 258 MODULE_DESCRIPTION("HMAC hash algorithm");