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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/hmac.h>
 20 #include <crypto/internal/hash.h>
 21 #include <crypto/scatterwalk.h>
 22 #include <linux/err.h>
 23 #include <linux/init.h>
 24 #include <linux/kernel.h>
 25 #include <linux/module.h>
 26 #include <linux/scatterlist.h>
 27 #include <linux/string.h>
 28 
 29 struct hmac_ctx {
 30         struct crypto_shash *hash;
 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_statesize(tfm) * 2,
 42                          crypto_tfm_ctx_alignment());
 43 }
 44 
 45 static int hmac_setkey(struct crypto_shash *parent,
 46                        const u8 *inkey, unsigned int keylen)
 47 {
 48         int bs = crypto_shash_blocksize(parent);
 49         int ds = crypto_shash_digestsize(parent);
 50         int ss = crypto_shash_statesize(parent);
 51         char *ipad = crypto_shash_ctx_aligned(parent);
 52         char *opad = ipad + ss;
 53         struct hmac_ctx *ctx = align_ptr(opad + ss,
 54                                          crypto_tfm_ctx_alignment());
 55         struct crypto_shash *hash = ctx->hash;
 56         SHASH_DESC_ON_STACK(shash, hash);
 57         unsigned int i;
 58 
 59         shash->tfm = hash;
 60         shash->flags = crypto_shash_get_flags(parent)
 61                 & CRYPTO_TFM_REQ_MAY_SLEEP;
 62 
 63         if (keylen > bs) {
 64                 int err;
 65 
 66                 err = crypto_shash_digest(shash, inkey, keylen, ipad);
 67                 if (err)
 68                         return err;
 69 
 70                 keylen = ds;
 71         } else
 72                 memcpy(ipad, inkey, keylen);
 73 
 74         memset(ipad + keylen, 0, bs - keylen);
 75         memcpy(opad, ipad, bs);
 76 
 77         for (i = 0; i < bs; i++) {
 78                 ipad[i] ^= HMAC_IPAD_VALUE;
 79                 opad[i] ^= HMAC_OPAD_VALUE;
 80         }
 81 
 82         return crypto_shash_init(shash) ?:
 83                crypto_shash_update(shash, ipad, bs) ?:
 84                crypto_shash_export(shash, ipad) ?:
 85                crypto_shash_init(shash) ?:
 86                crypto_shash_update(shash, opad, bs) ?:
 87                crypto_shash_export(shash, opad);
 88 }
 89 
 90 static int hmac_export(struct shash_desc *pdesc, void *out)
 91 {
 92         struct shash_desc *desc = shash_desc_ctx(pdesc);
 93 
 94         desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 95 
 96         return crypto_shash_export(desc, out);
 97 }
 98 
 99 static int hmac_import(struct shash_desc *pdesc, const void *in)
100 {
101         struct shash_desc *desc = shash_desc_ctx(pdesc);
102         struct hmac_ctx *ctx = hmac_ctx(pdesc->tfm);
103 
104         desc->tfm = ctx->hash;
105         desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
106 
107         return crypto_shash_import(desc, in);
108 }
109 
110 static int hmac_init(struct shash_desc *pdesc)
111 {
112         return hmac_import(pdesc, crypto_shash_ctx_aligned(pdesc->tfm));
113 }
114 
115 static int hmac_update(struct shash_desc *pdesc,
116                        const u8 *data, unsigned int nbytes)
117 {
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_update(desc, data, nbytes);
123 }
124 
125 static int hmac_final(struct shash_desc *pdesc, u8 *out)
126 {
127         struct crypto_shash *parent = pdesc->tfm;
128         int ds = crypto_shash_digestsize(parent);
129         int ss = crypto_shash_statesize(parent);
130         char *opad = crypto_shash_ctx_aligned(parent) + ss;
131         struct shash_desc *desc = shash_desc_ctx(pdesc);
132 
133         desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
134 
135         return crypto_shash_final(desc, out) ?:
136                crypto_shash_import(desc, opad) ?:
137                crypto_shash_finup(desc, out, ds, out);
138 }
139 
140 static int hmac_finup(struct shash_desc *pdesc, const u8 *data,
141                       unsigned int nbytes, u8 *out)
142 {
143 
144         struct crypto_shash *parent = pdesc->tfm;
145         int ds = crypto_shash_digestsize(parent);
146         int ss = crypto_shash_statesize(parent);
147         char *opad = crypto_shash_ctx_aligned(parent) + ss;
148         struct shash_desc *desc = shash_desc_ctx(pdesc);
149 
150         desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
151 
152         return crypto_shash_finup(desc, data, nbytes, out) ?:
153                crypto_shash_import(desc, opad) ?:
154                crypto_shash_finup(desc, out, ds, out);
155 }
156 
157 static int hmac_init_tfm(struct crypto_tfm *tfm)
158 {
159         struct crypto_shash *parent = __crypto_shash_cast(tfm);
160         struct crypto_shash *hash;
161         struct crypto_instance *inst = (void *)tfm->__crt_alg;
162         struct crypto_shash_spawn *spawn = crypto_instance_ctx(inst);
163         struct hmac_ctx *ctx = hmac_ctx(parent);
164 
165         hash = crypto_spawn_shash(spawn);
166         if (IS_ERR(hash))
167                 return PTR_ERR(hash);
168 
169         parent->descsize = sizeof(struct shash_desc) +
170                            crypto_shash_descsize(hash);
171         if (WARN_ON(parent->descsize > HASH_MAX_DESCSIZE)) {
172                 crypto_free_shash(hash);
173                 return -EINVAL;
174         }
175 
176         ctx->hash = hash;
177         return 0;
178 }
179 
180 static void hmac_exit_tfm(struct crypto_tfm *tfm)
181 {
182         struct hmac_ctx *ctx = hmac_ctx(__crypto_shash_cast(tfm));
183         crypto_free_shash(ctx->hash);
184 }
185 
186 static int hmac_create(struct crypto_template *tmpl, struct rtattr **tb)
187 {
188         struct shash_instance *inst;
189         struct crypto_alg *alg;
190         struct shash_alg *salg;
191         int err;
192         int ds;
193         int ss;
194 
195         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH);
196         if (err)
197                 return err;
198 
199         salg = shash_attr_alg(tb[1], 0, 0);
200         if (IS_ERR(salg))
201                 return PTR_ERR(salg);
202         alg = &salg->base;
203 
204         /* The underlying hash algorithm must be unkeyed */
205         err = -EINVAL;
206         if (crypto_shash_alg_has_setkey(salg))
207                 goto out_put_alg;
208 
209         ds = salg->digestsize;
210         ss = salg->statesize;
211         if (ds > alg->cra_blocksize ||
212             ss < alg->cra_blocksize)
213                 goto out_put_alg;
214 
215         inst = shash_alloc_instance("hmac", alg);
216         err = PTR_ERR(inst);
217         if (IS_ERR(inst))
218                 goto out_put_alg;
219 
220         err = crypto_init_shash_spawn(shash_instance_ctx(inst), salg,
221                                       shash_crypto_instance(inst));
222         if (err)
223                 goto out_free_inst;
224 
225         inst->alg.base.cra_priority = alg->cra_priority;
226         inst->alg.base.cra_blocksize = alg->cra_blocksize;
227         inst->alg.base.cra_alignmask = alg->cra_alignmask;
228 
229         ss = ALIGN(ss, alg->cra_alignmask + 1);
230         inst->alg.digestsize = ds;
231         inst->alg.statesize = ss;
232 
233         inst->alg.base.cra_ctxsize = sizeof(struct hmac_ctx) +
234                                      ALIGN(ss * 2, crypto_tfm_ctx_alignment());
235 
236         inst->alg.base.cra_init = hmac_init_tfm;
237         inst->alg.base.cra_exit = hmac_exit_tfm;
238 
239         inst->alg.init = hmac_init;
240         inst->alg.update = hmac_update;
241         inst->alg.final = hmac_final;
242         inst->alg.finup = hmac_finup;
243         inst->alg.export = hmac_export;
244         inst->alg.import = hmac_import;
245         inst->alg.setkey = hmac_setkey;
246 
247         err = shash_register_instance(tmpl, inst);
248         if (err) {
249 out_free_inst:
250                 shash_free_instance(shash_crypto_instance(inst));
251         }
252 
253 out_put_alg:
254         crypto_mod_put(alg);
255         return err;
256 }
257 
258 static struct crypto_template hmac_tmpl = {
259         .name = "hmac",
260         .create = hmac_create,
261         .free = shash_free_instance,
262         .module = THIS_MODULE,
263 };
264 
265 static int __init hmac_module_init(void)
266 {
267         return crypto_register_template(&hmac_tmpl);
268 }
269 
270 static void __exit hmac_module_exit(void)
271 {
272         crypto_unregister_template(&hmac_tmpl);
273 }
274 
275 module_init(hmac_module_init);
276 module_exit(hmac_module_exit);
277 
278 MODULE_LICENSE("GPL");
279 MODULE_DESCRIPTION("HMAC hash algorithm");
280 MODULE_ALIAS_CRYPTO("hmac");
281 

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