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