linux/crypto/hmac.c
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   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
  24struct hmac_ctx {
  25        struct crypto_shash *hash;
  26};
  27
  28static inline void *align_ptr(void *p, unsigned int align)
  29{
  30        return (void *)ALIGN((unsigned long)p, align);
  31}
  32
  33static 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
  40static 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
  83static 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
  90static 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
 100static int hmac_init(struct shash_desc *pdesc)
 101{
 102        return hmac_import(pdesc, crypto_shash_ctx_aligned(pdesc->tfm));
 103}
 104
 105static 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
 113static 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
 126static 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
 141static int hmac_init_tfm(struct crypto_shash *parent)
 142{
 143        struct crypto_shash *hash;
 144        struct shash_instance *inst = shash_alg_instance(parent);
 145        struct crypto_shash_spawn *spawn = shash_instance_ctx(inst);
 146        struct hmac_ctx *ctx = hmac_ctx(parent);
 147
 148        hash = crypto_spawn_shash(spawn);
 149        if (IS_ERR(hash))
 150                return PTR_ERR(hash);
 151
 152        parent->descsize = sizeof(struct shash_desc) +
 153                           crypto_shash_descsize(hash);
 154
 155        ctx->hash = hash;
 156        return 0;
 157}
 158
 159static void hmac_exit_tfm(struct crypto_shash *parent)
 160{
 161        struct hmac_ctx *ctx = hmac_ctx(parent);
 162        crypto_free_shash(ctx->hash);
 163}
 164
 165static int hmac_create(struct crypto_template *tmpl, struct rtattr **tb)
 166{
 167        struct shash_instance *inst;
 168        struct crypto_shash_spawn *spawn;
 169        struct crypto_alg *alg;
 170        struct shash_alg *salg;
 171        u32 mask;
 172        int err;
 173        int ds;
 174        int ss;
 175
 176        err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH, &mask);
 177        if (err)
 178                return err;
 179
 180        inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
 181        if (!inst)
 182                return -ENOMEM;
 183        spawn = shash_instance_ctx(inst);
 184
 185        err = crypto_grab_shash(spawn, shash_crypto_instance(inst),
 186                                crypto_attr_alg_name(tb[1]), 0, mask);
 187        if (err)
 188                goto err_free_inst;
 189        salg = crypto_spawn_shash_alg(spawn);
 190        alg = &salg->base;
 191
 192        /* The underlying hash algorithm must not require a key */
 193        err = -EINVAL;
 194        if (crypto_shash_alg_needs_key(salg))
 195                goto err_free_inst;
 196
 197        ds = salg->digestsize;
 198        ss = salg->statesize;
 199        if (ds > alg->cra_blocksize ||
 200            ss < alg->cra_blocksize)
 201                goto err_free_inst;
 202
 203        err = crypto_inst_setname(shash_crypto_instance(inst), tmpl->name, alg);
 204        if (err)
 205                goto err_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        ss = ALIGN(ss, alg->cra_alignmask + 1);
 212        inst->alg.digestsize = ds;
 213        inst->alg.statesize = ss;
 214
 215        inst->alg.base.cra_ctxsize = sizeof(struct hmac_ctx) +
 216                                     ALIGN(ss * 2, crypto_tfm_ctx_alignment());
 217
 218        inst->alg.init = hmac_init;
 219        inst->alg.update = hmac_update;
 220        inst->alg.final = hmac_final;
 221        inst->alg.finup = hmac_finup;
 222        inst->alg.export = hmac_export;
 223        inst->alg.import = hmac_import;
 224        inst->alg.setkey = hmac_setkey;
 225        inst->alg.init_tfm = hmac_init_tfm;
 226        inst->alg.exit_tfm = hmac_exit_tfm;
 227
 228        inst->free = shash_free_singlespawn_instance;
 229
 230        err = shash_register_instance(tmpl, inst);
 231        if (err) {
 232err_free_inst:
 233                shash_free_singlespawn_instance(inst);
 234        }
 235        return err;
 236}
 237
 238static struct crypto_template hmac_tmpl = {
 239        .name = "hmac",
 240        .create = hmac_create,
 241        .module = THIS_MODULE,
 242};
 243
 244static int __init hmac_module_init(void)
 245{
 246        return crypto_register_template(&hmac_tmpl);
 247}
 248
 249static void __exit hmac_module_exit(void)
 250{
 251        crypto_unregister_template(&hmac_tmpl);
 252}
 253
 254subsys_initcall(hmac_module_init);
 255module_exit(hmac_module_exit);
 256
 257MODULE_LICENSE("GPL");
 258MODULE_DESCRIPTION("HMAC hash algorithm");
 259MODULE_ALIAS_CRYPTO("hmac");
 260
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