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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/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 
 28 struct hmac_ctx {
 29         struct crypto_shash *hash;
 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_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 
 44 static 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 
 92 static 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 
101 static 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 
112 static int hmac_init(struct shash_desc *pdesc)
113 {
114         return hmac_import(pdesc, crypto_shash_ctx_aligned(pdesc->tfm));
115 }
116 
117 static 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 
127 static 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 
142 static 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 
159 static 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 
178 static 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 
184 static 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         alg = &salg->base;
201 
202         /* The underlying hash algorithm must be unkeyed */
203         err = -EINVAL;
204         if (crypto_shash_alg_has_setkey(salg))
205                 goto out_put_alg;
206 
207         ds = salg->digestsize;
208         ss = salg->statesize;
209         if (ds > alg->cra_blocksize ||
210             ss < alg->cra_blocksize)
211                 goto out_put_alg;
212 
213         inst = shash_alloc_instance("hmac", alg);
214         err = PTR_ERR(inst);
215         if (IS_ERR(inst))
216                 goto out_put_alg;
217 
218         err = crypto_init_shash_spawn(shash_instance_ctx(inst), salg,
219                                       shash_crypto_instance(inst));
220         if (err)
221                 goto out_free_inst;
222 
223         inst->alg.base.cra_priority = alg->cra_priority;
224         inst->alg.base.cra_blocksize = alg->cra_blocksize;
225         inst->alg.base.cra_alignmask = alg->cra_alignmask;
226 
227         ss = ALIGN(ss, alg->cra_alignmask + 1);
228         inst->alg.digestsize = ds;
229         inst->alg.statesize = ss;
230 
231         inst->alg.base.cra_ctxsize = sizeof(struct hmac_ctx) +
232                                      ALIGN(ss * 2, crypto_tfm_ctx_alignment());
233 
234         inst->alg.base.cra_init = hmac_init_tfm;
235         inst->alg.base.cra_exit = hmac_exit_tfm;
236 
237         inst->alg.init = hmac_init;
238         inst->alg.update = hmac_update;
239         inst->alg.final = hmac_final;
240         inst->alg.finup = hmac_finup;
241         inst->alg.export = hmac_export;
242         inst->alg.import = hmac_import;
243         inst->alg.setkey = hmac_setkey;
244 
245         err = shash_register_instance(tmpl, inst);
246         if (err) {
247 out_free_inst:
248                 shash_free_instance(shash_crypto_instance(inst));
249         }
250 
251 out_put_alg:
252         crypto_mod_put(alg);
253         return err;
254 }
255 
256 static struct crypto_template hmac_tmpl = {
257         .name = "hmac",
258         .create = hmac_create,
259         .free = shash_free_instance,
260         .module = THIS_MODULE,
261 };
262 
263 static int __init hmac_module_init(void)
264 {
265         return crypto_register_template(&hmac_tmpl);
266 }
267 
268 static void __exit hmac_module_exit(void)
269 {
270         crypto_unregister_template(&hmac_tmpl);
271 }
272 
273 module_init(hmac_module_init);
274 module_exit(hmac_module_exit);
275 
276 MODULE_LICENSE("GPL");
277 MODULE_DESCRIPTION("HMAC hash algorithm");
278 MODULE_ALIAS_CRYPTO("hmac");
279 

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