linux/crypto/hmac.c
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   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/string.h>
  27
  28struct hmac_ctx {
  29        struct crypto_shash *hash;
  30};
  31
  32static inline void *align_ptr(void *p, unsigned int align)
  33{
  34        return (void *)ALIGN((unsigned long)p, align);
  35}
  36
  37static inline struct hmac_ctx *hmac_ctx(struct crypto_shash *tfm)
  38{
  39        return align_ptr(crypto_shash_ctx_aligned(tfm) +
  40                         crypto_shash_statesize(tfm) * 2,
  41                         crypto_tfm_ctx_alignment());
  42}
  43
  44static int hmac_setkey(struct crypto_shash *parent,
  45                       const u8 *inkey, unsigned int keylen)
  46{
  47        int bs = crypto_shash_blocksize(parent);
  48        int ds = crypto_shash_digestsize(parent);
  49        int ss = crypto_shash_statesize(parent);
  50        char *ipad = crypto_shash_ctx_aligned(parent);
  51        char *opad = ipad + ss;
  52        struct hmac_ctx *ctx = align_ptr(opad + ss,
  53                                         crypto_tfm_ctx_alignment());
  54        struct crypto_shash *hash = ctx->hash;
  55        struct {
  56                struct shash_desc shash;
  57                char ctx[crypto_shash_descsize(hash)];
  58        } desc;
  59        unsigned int i;
  60
  61        desc.shash.tfm = hash;
  62        desc.shash.flags = crypto_shash_get_flags(parent) &
  63                            CRYPTO_TFM_REQ_MAY_SLEEP;
  64
  65        if (keylen > bs) {
  66                int err;
  67
  68                err = crypto_shash_digest(&desc.shash, inkey, keylen, ipad);
  69                if (err)
  70                        return err;
  71
  72                keylen = ds;
  73        } else
  74                memcpy(ipad, inkey, keylen);
  75
  76        memset(ipad + keylen, 0, bs - keylen);
  77        memcpy(opad, ipad, bs);
  78
  79        for (i = 0; i < bs; i++) {
  80                ipad[i] ^= 0x36;
  81                opad[i] ^= 0x5c;
  82        }
  83
  84        return crypto_shash_init(&desc.shash) ?:
  85               crypto_shash_update(&desc.shash, ipad, bs) ?:
  86               crypto_shash_export(&desc.shash, ipad) ?:
  87               crypto_shash_init(&desc.shash) ?:
  88               crypto_shash_update(&desc.shash, opad, bs) ?:
  89               crypto_shash_export(&desc.shash, opad);
  90}
  91
  92static int hmac_export(struct shash_desc *pdesc, void *out)
  93{
  94        struct shash_desc *desc = shash_desc_ctx(pdesc);
  95
  96        desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
  97
  98        return crypto_shash_export(desc, out);
  99}
 100
 101static int hmac_import(struct shash_desc *pdesc, const void *in)
 102{
 103        struct shash_desc *desc = shash_desc_ctx(pdesc);
 104        struct hmac_ctx *ctx = hmac_ctx(pdesc->tfm);
 105
 106        desc->tfm = ctx->hash;
 107        desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 108
 109        return crypto_shash_import(desc, in);
 110}
 111
 112static int hmac_init(struct shash_desc *pdesc)
 113{
 114        return hmac_import(pdesc, crypto_shash_ctx_aligned(pdesc->tfm));
 115}
 116
 117static int hmac_update(struct shash_desc *pdesc,
 118                       const u8 *data, unsigned int nbytes)
 119{
 120        struct shash_desc *desc = shash_desc_ctx(pdesc);
 121
 122        desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 123
 124        return crypto_shash_update(desc, data, nbytes);
 125}
 126
 127static int hmac_final(struct shash_desc *pdesc, u8 *out)
 128{
 129        struct crypto_shash *parent = pdesc->tfm;
 130        int ds = crypto_shash_digestsize(parent);
 131        int ss = crypto_shash_statesize(parent);
 132        char *opad = crypto_shash_ctx_aligned(parent) + ss;
 133        struct shash_desc *desc = shash_desc_ctx(pdesc);
 134
 135        desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 136
 137        return crypto_shash_final(desc, out) ?:
 138               crypto_shash_import(desc, opad) ?:
 139               crypto_shash_finup(desc, out, ds, out);
 140}
 141
 142static int hmac_finup(struct shash_desc *pdesc, const u8 *data,
 143                      unsigned int nbytes, u8 *out)
 144{
 145
 146        struct crypto_shash *parent = pdesc->tfm;
 147        int ds = crypto_shash_digestsize(parent);
 148        int ss = crypto_shash_statesize(parent);
 149        char *opad = crypto_shash_ctx_aligned(parent) + ss;
 150        struct shash_desc *desc = shash_desc_ctx(pdesc);
 151
 152        desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 153
 154        return crypto_shash_finup(desc, data, nbytes, out) ?:
 155               crypto_shash_import(desc, opad) ?:
 156               crypto_shash_finup(desc, out, ds, out);
 157}
 158
 159static int hmac_init_tfm(struct crypto_tfm *tfm)
 160{
 161        struct crypto_shash *parent = __crypto_shash_cast(tfm);
 162        struct crypto_shash *hash;
 163        struct crypto_instance *inst = (void *)tfm->__crt_alg;
 164        struct crypto_shash_spawn *spawn = crypto_instance_ctx(inst);
 165        struct hmac_ctx *ctx = hmac_ctx(parent);
 166
 167        hash = crypto_spawn_shash(spawn);
 168        if (IS_ERR(hash))
 169                return PTR_ERR(hash);
 170
 171        parent->descsize = sizeof(struct shash_desc) +
 172                           crypto_shash_descsize(hash);
 173
 174        ctx->hash = hash;
 175        return 0;
 176}
 177
 178static void hmac_exit_tfm(struct crypto_tfm *tfm)
 179{
 180        struct hmac_ctx *ctx = hmac_ctx(__crypto_shash_cast(tfm));
 181        crypto_free_shash(ctx->hash);
 182}
 183
 184static int hmac_create(struct crypto_template *tmpl, struct rtattr **tb)
 185{
 186        struct shash_instance *inst;
 187        struct crypto_alg *alg;
 188        struct shash_alg *salg;
 189        int err;
 190        int ds;
 191        int ss;
 192
 193        err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH);
 194        if (err)
 195                return err;
 196
 197        salg = shash_attr_alg(tb[1], 0, 0);
 198        if (IS_ERR(salg))
 199                return PTR_ERR(salg);
 200
 201        err = -EINVAL;
 202        ds = salg->digestsize;
 203        ss = salg->statesize;
 204        alg = &salg->base;
 205        if (ds > alg->cra_blocksize ||
 206            ss < alg->cra_blocksize)
 207                goto out_put_alg;
 208
 209        inst = shash_alloc_instance("hmac", alg);
 210        err = PTR_ERR(inst);
 211        if (IS_ERR(inst))
 212                goto out_put_alg;
 213
 214        err = crypto_init_shash_spawn(shash_instance_ctx(inst), salg,
 215                                      shash_crypto_instance(inst));
 216        if (err)
 217                goto out_free_inst;
 218
 219        inst->alg.base.cra_priority = alg->cra_priority;
 220        inst->alg.base.cra_blocksize = alg->cra_blocksize;
 221        inst->alg.base.cra_alignmask = alg->cra_alignmask;
 222
 223        ss = ALIGN(ss, alg->cra_alignmask + 1);
 224        inst->alg.digestsize = ds;
 225        inst->alg.statesize = ss;
 226
 227        inst->alg.base.cra_ctxsize = sizeof(struct hmac_ctx) +
 228                                     ALIGN(ss * 2, crypto_tfm_ctx_alignment());
 229
 230        inst->alg.base.cra_init = hmac_init_tfm;
 231        inst->alg.base.cra_exit = hmac_exit_tfm;
 232
 233        inst->alg.init = hmac_init;
 234        inst->alg.update = hmac_update;
 235        inst->alg.final = hmac_final;
 236        inst->alg.finup = hmac_finup;
 237        inst->alg.export = hmac_export;
 238        inst->alg.import = hmac_import;
 239        inst->alg.setkey = hmac_setkey;
 240
 241        err = shash_register_instance(tmpl, inst);
 242        if (err) {
 243out_free_inst:
 244                shash_free_instance(shash_crypto_instance(inst));
 245        }
 246
 247out_put_alg:
 248        crypto_mod_put(alg);
 249        return err;
 250}
 251
 252static struct crypto_template hmac_tmpl = {
 253        .name = "hmac",
 254        .create = hmac_create,
 255        .free = shash_free_instance,
 256        .module = THIS_MODULE,
 257};
 258
 259static int __init hmac_module_init(void)
 260{
 261        return crypto_register_template(&hmac_tmpl);
 262}
 263
 264static void __exit hmac_module_exit(void)
 265{
 266        crypto_unregister_template(&hmac_tmpl);
 267}
 268
 269module_init(hmac_module_init);
 270module_exit(hmac_module_exit);
 271
 272MODULE_LICENSE("GPL");
 273MODULE_DESCRIPTION("HMAC hash algorithm");
 274
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