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
  96         desc.tfm = ctx->child;
  97         desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
  98         sg_set_buf(&tmp, ipad, bs);
  99
 100         return unlikely(crypto_hash_init(&desc)) ?:
 101                crypto_hash_update(&desc, &tmp, 1);
 102 }
 103
 104 static int hmac_update(struct hash_desc *pdesc,
 105                        struct scatterlist *sg, unsigned int nbytes)
 106 {
 107         struct hmac_ctx *ctx = hmac_ctx(pdesc->tfm);
 108         struct hash_desc desc;
 109
 110         desc.tfm = ctx->child;
 111         desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 112
 113         return crypto_hash_update(&desc, sg, nbytes);
 114 }
 115
 116 static int hmac_final(struct hash_desc *pdesc, u8 *out)
 117 {
 118         struct crypto_hash *parent = pdesc->tfm;
 119         int bs = crypto_hash_blocksize(parent);
 120         int ds = crypto_hash_digestsize(parent);
 121         char *opad = crypto_hash_ctx_aligned(parent) + bs;
 122         char *digest = opad + bs;
 123         struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
 124         struct hash_desc desc;
 125         struct scatterlist tmp;
 126
 127         desc.tfm = ctx->child;
 128         desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 129         sg_set_buf(&tmp, opad, bs + ds);
 130
 131         return unlikely(crypto_hash_final(&desc, digest)) ?:
 132                crypto_hash_digest(&desc, &tmp, bs + ds, out);
 133 }
 134
 135 static int hmac_digest(struct hash_desc *pdesc, struct scatterlist *sg,
 136                        unsigned int nbytes, u8 *out)
 137 {
 138         struct crypto_hash *parent = pdesc->tfm;
 139         int bs = crypto_hash_blocksize(parent);
 140         int ds = crypto_hash_digestsize(parent);
 141         char *ipad = crypto_hash_ctx_aligned(parent);
 142         char *opad = ipad + bs;
 143         char *digest = opad + bs;
 144         struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
 145         struct hash_desc desc;
 146         struct scatterlist sg1[2];
 147         struct scatterlist sg2[1];
 148
 149         desc.tfm = ctx->child;
 150         desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 151
 152         sg_set_buf(sg1, ipad, bs);
 153         sg1[1].page = (void *)sg;
 154         sg1[1].length = 0;
 155         sg_set_buf(sg2, opad, bs + ds);
 156
 157         return unlikely(crypto_hash_digest(&desc, sg1, nbytes + bs, digest)) ?:
 158                crypto_hash_digest(&desc, sg2, bs + ds, out);
 159 }
 160
 161 static int hmac_init_tfm(struct crypto_tfm *tfm)
 162 {
 163         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 164         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 165         struct hmac_ctx *ctx = hmac_ctx(__crypto_hash_cast(tfm));
 166
 167         tfm = crypto_spawn_tfm(spawn);
 168         if (IS_ERR(tfm))
 169                 return PTR_ERR(tfm);
 170
 171         ctx->child = crypto_hash_cast(tfm);
 172         return 0;
 173 }
 174
 175 static void hmac_exit_tfm(struct crypto_tfm *tfm)
 176 {
 177         struct hmac_ctx *ctx = hmac_ctx(__crypto_hash_cast(tfm));
 178         crypto_free_hash(ctx->child);
 179 }
 180
 181 static void hmac_free(struct crypto_instance *inst)
 182 {
 183         crypto_drop_spawn(crypto_instance_ctx(inst));
 184         kfree(inst);
 185 }
 186
 187 static struct crypto_instance *hmac_alloc(void *param, unsigned int len)
 188 {
 189         struct crypto_instance *inst;
 190         struct crypto_alg *alg;
 191
 192         alg = crypto_get_attr_alg(param, len, CRYPTO_ALG_TYPE_HASH,
 193                                   CRYPTO_ALG_TYPE_HASH_MASK | CRYPTO_ALG_ASYNC);
 194         if (IS_ERR(alg))
 195                 return ERR_PTR(PTR_ERR(alg));
 196
 197         inst = crypto_alloc_instance("hmac", alg);
 198         if (IS_ERR(inst))
 199                 goto out_put_alg;
 200
 201         inst->alg.cra_flags = CRYPTO_ALG_TYPE_HASH;
 202         inst->alg.cra_priority = alg->cra_priority;
 203         inst->alg.cra_blocksize = alg->cra_blocksize;
 204         inst->alg.cra_alignmask = alg->cra_alignmask;
 205         inst->alg.cra_type = &crypto_hash_type;
 206
 207         inst->alg.cra_hash.digestsize =
 208                 (alg->cra_flags & CRYPTO_ALG_TYPE_MASK) ==
 209                 CRYPTO_ALG_TYPE_HASH ? alg->cra_hash.digestsize :
 210                                        alg->cra_digest.dia_digestsize;
 211
 212         inst->alg.cra_ctxsize = sizeof(struct hmac_ctx) +
 213                                 ALIGN(inst->alg.cra_blocksize * 2 +
 214                                       inst->alg.cra_hash.digestsize,
 215                                       sizeof(void *));
 216
 217         inst->alg.cra_init = hmac_init_tfm;
 218         inst->alg.cra_exit = hmac_exit_tfm;
 219
 220         inst->alg.cra_hash.init = hmac_init;
 221         inst->alg.cra_hash.update = hmac_update;
 222         inst->alg.cra_hash.final = hmac_final;
 223         inst->alg.cra_hash.digest = hmac_digest;
 224         inst->alg.cra_hash.setkey = hmac_setkey;
 225
 226 out_put_alg:
 227         crypto_mod_put(alg);
 228         return inst;
 229 }
 230
 231 static struct crypto_template hmac_tmpl = {
 232         .name = "hmac",
 233         .alloc = hmac_alloc,
 234         .free = hmac_free,
 235         .module = THIS_MODULE,
 236 };
 237
 238 static int __init hmac_module_init(void)
 239 {
 240         return crypto_register_template(&hmac_tmpl);
 241 }
 242
 243 static void __exit hmac_module_exit(void)
 244 {
 245         crypto_unregister_template(&hmac_tmpl);
 246 }
 247
 248 module_init(hmac_module_init);
 249 module_exit(hmac_module_exit);
 250
 251 MODULE_LICENSE("GPL");
 252 MODULE_DESCRIPTION("HMAC hash algorithm");