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TOMOYO Linux Cross Reference
Linux/security/keys/dh.c

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  1 /* Crypto operations using stored keys
  2  *
  3  * Copyright (c) 2016, Intel Corporation
  4  *
  5  * This program is free software; you can redistribute it and/or
  6  * modify it under the terms of the GNU General Public License
  7  * as published by the Free Software Foundation; either version
  8  * 2 of the License, or (at your option) any later version.
  9  */
 10 
 11 #include <linux/slab.h>
 12 #include <linux/uaccess.h>
 13 #include <linux/scatterlist.h>
 14 #include <linux/crypto.h>
 15 #include <crypto/hash.h>
 16 #include <crypto/kpp.h>
 17 #include <crypto/dh.h>
 18 #include <keys/user-type.h>
 19 #include "internal.h"
 20 
 21 static ssize_t dh_data_from_key(key_serial_t keyid, void **data)
 22 {
 23         struct key *key;
 24         key_ref_t key_ref;
 25         long status;
 26         ssize_t ret;
 27 
 28         key_ref = lookup_user_key(keyid, 0, KEY_NEED_READ);
 29         if (IS_ERR(key_ref)) {
 30                 ret = -ENOKEY;
 31                 goto error;
 32         }
 33 
 34         key = key_ref_to_ptr(key_ref);
 35 
 36         ret = -EOPNOTSUPP;
 37         if (key->type == &key_type_user) {
 38                 down_read(&key->sem);
 39                 status = key_validate(key);
 40                 if (status == 0) {
 41                         const struct user_key_payload *payload;
 42                         uint8_t *duplicate;
 43 
 44                         payload = user_key_payload_locked(key);
 45 
 46                         duplicate = kmemdup(payload->data, payload->datalen,
 47                                             GFP_KERNEL);
 48                         if (duplicate) {
 49                                 *data = duplicate;
 50                                 ret = payload->datalen;
 51                         } else {
 52                                 ret = -ENOMEM;
 53                         }
 54                 }
 55                 up_read(&key->sem);
 56         }
 57 
 58         key_put(key);
 59 error:
 60         return ret;
 61 }
 62 
 63 static void dh_free_data(struct dh *dh)
 64 {
 65         kzfree(dh->key);
 66         kzfree(dh->p);
 67         kzfree(dh->g);
 68 }
 69 
 70 struct dh_completion {
 71         struct completion completion;
 72         int err;
 73 };
 74 
 75 static void dh_crypto_done(struct crypto_async_request *req, int err)
 76 {
 77         struct dh_completion *compl = req->data;
 78 
 79         if (err == -EINPROGRESS)
 80                 return;
 81 
 82         compl->err = err;
 83         complete(&compl->completion);
 84 }
 85 
 86 struct kdf_sdesc {
 87         struct shash_desc shash;
 88         char ctx[];
 89 };
 90 
 91 static int kdf_alloc(struct kdf_sdesc **sdesc_ret, char *hashname)
 92 {
 93         struct crypto_shash *tfm;
 94         struct kdf_sdesc *sdesc;
 95         int size;
 96         int err;
 97 
 98         /* allocate synchronous hash */
 99         tfm = crypto_alloc_shash(hashname, 0, 0);
100         if (IS_ERR(tfm)) {
101                 pr_info("could not allocate digest TFM handle %s\n", hashname);
102                 return PTR_ERR(tfm);
103         }
104 
105         err = -EINVAL;
106         if (crypto_shash_digestsize(tfm) == 0)
107                 goto out_free_tfm;
108 
109         err = -ENOMEM;
110         size = sizeof(struct shash_desc) + crypto_shash_descsize(tfm);
111         sdesc = kmalloc(size, GFP_KERNEL);
112         if (!sdesc)
113                 goto out_free_tfm;
114         sdesc->shash.tfm = tfm;
115         sdesc->shash.flags = 0x0;
116 
117         *sdesc_ret = sdesc;
118 
119         return 0;
120 
121 out_free_tfm:
122         crypto_free_shash(tfm);
123         return err;
124 }
125 
126 static void kdf_dealloc(struct kdf_sdesc *sdesc)
127 {
128         if (!sdesc)
129                 return;
130 
131         if (sdesc->shash.tfm)
132                 crypto_free_shash(sdesc->shash.tfm);
133 
134         kzfree(sdesc);
135 }
136 
137 /*
138  * Implementation of the KDF in counter mode according to SP800-108 section 5.1
139  * as well as SP800-56A section 5.8.1 (Single-step KDF).
140  *
141  * SP800-56A:
142  * The src pointer is defined as Z || other info where Z is the shared secret
143  * from DH and other info is an arbitrary string (see SP800-56A section
144  * 5.8.1.2).
145  *
146  * 'dlen' must be a multiple of the digest size.
147  */
148 static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen,
149                    u8 *dst, unsigned int dlen, unsigned int zlen)
150 {
151         struct shash_desc *desc = &sdesc->shash;
152         unsigned int h = crypto_shash_digestsize(desc->tfm);
153         int err = 0;
154         u8 *dst_orig = dst;
155         __be32 counter = cpu_to_be32(1);
156 
157         while (dlen) {
158                 err = crypto_shash_init(desc);
159                 if (err)
160                         goto err;
161 
162                 err = crypto_shash_update(desc, (u8 *)&counter, sizeof(__be32));
163                 if (err)
164                         goto err;
165 
166                 if (zlen && h) {
167                         u8 tmpbuffer[32];
168                         size_t chunk = min_t(size_t, zlen, sizeof(tmpbuffer));
169                         memset(tmpbuffer, 0, chunk);
170 
171                         do {
172                                 err = crypto_shash_update(desc, tmpbuffer,
173                                                           chunk);
174                                 if (err)
175                                         goto err;
176 
177                                 zlen -= chunk;
178                                 chunk = min_t(size_t, zlen, sizeof(tmpbuffer));
179                         } while (zlen);
180                 }
181 
182                 if (src && slen) {
183                         err = crypto_shash_update(desc, src, slen);
184                         if (err)
185                                 goto err;
186                 }
187 
188                 err = crypto_shash_final(desc, dst);
189                 if (err)
190                         goto err;
191 
192                 dlen -= h;
193                 dst += h;
194                 counter = cpu_to_be32(be32_to_cpu(counter) + 1);
195         }
196 
197         return 0;
198 
199 err:
200         memzero_explicit(dst_orig, dlen);
201         return err;
202 }
203 
204 static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc,
205                                  char __user *buffer, size_t buflen,
206                                  uint8_t *kbuf, size_t kbuflen, size_t lzero)
207 {
208         uint8_t *outbuf = NULL;
209         int ret;
210         size_t outbuf_len = roundup(buflen,
211                                     crypto_shash_digestsize(sdesc->shash.tfm));
212 
213         outbuf = kmalloc(outbuf_len, GFP_KERNEL);
214         if (!outbuf) {
215                 ret = -ENOMEM;
216                 goto err;
217         }
218 
219         ret = kdf_ctr(sdesc, kbuf, kbuflen, outbuf, outbuf_len, lzero);
220         if (ret)
221                 goto err;
222 
223         ret = buflen;
224         if (copy_to_user(buffer, outbuf, buflen) != 0)
225                 ret = -EFAULT;
226 
227 err:
228         kzfree(outbuf);
229         return ret;
230 }
231 
232 long __keyctl_dh_compute(struct keyctl_dh_params __user *params,
233                          char __user *buffer, size_t buflen,
234                          struct keyctl_kdf_params *kdfcopy)
235 {
236         long ret;
237         ssize_t dlen;
238         int secretlen;
239         int outlen;
240         struct keyctl_dh_params pcopy;
241         struct dh dh_inputs;
242         struct scatterlist outsg;
243         struct dh_completion compl;
244         struct crypto_kpp *tfm;
245         struct kpp_request *req;
246         uint8_t *secret;
247         uint8_t *outbuf;
248         struct kdf_sdesc *sdesc = NULL;
249 
250         if (!params || (!buffer && buflen)) {
251                 ret = -EINVAL;
252                 goto out1;
253         }
254         if (copy_from_user(&pcopy, params, sizeof(pcopy)) != 0) {
255                 ret = -EFAULT;
256                 goto out1;
257         }
258 
259         if (kdfcopy) {
260                 char *hashname;
261 
262                 if (memchr_inv(kdfcopy->__spare, 0, sizeof(kdfcopy->__spare))) {
263                         ret = -EINVAL;
264                         goto out1;
265                 }
266 
267                 if (buflen > KEYCTL_KDF_MAX_OUTPUT_LEN ||
268                     kdfcopy->otherinfolen > KEYCTL_KDF_MAX_OI_LEN) {
269                         ret = -EMSGSIZE;
270                         goto out1;
271                 }
272 
273                 /* get KDF name string */
274                 hashname = strndup_user(kdfcopy->hashname, CRYPTO_MAX_ALG_NAME);
275                 if (IS_ERR(hashname)) {
276                         ret = PTR_ERR(hashname);
277                         goto out1;
278                 }
279 
280                 /* allocate KDF from the kernel crypto API */
281                 ret = kdf_alloc(&sdesc, hashname);
282                 kfree(hashname);
283                 if (ret)
284                         goto out1;
285         }
286 
287         memset(&dh_inputs, 0, sizeof(dh_inputs));
288 
289         dlen = dh_data_from_key(pcopy.prime, &dh_inputs.p);
290         if (dlen < 0) {
291                 ret = dlen;
292                 goto out1;
293         }
294         dh_inputs.p_size = dlen;
295 
296         dlen = dh_data_from_key(pcopy.base, &dh_inputs.g);
297         if (dlen < 0) {
298                 ret = dlen;
299                 goto out2;
300         }
301         dh_inputs.g_size = dlen;
302 
303         dlen = dh_data_from_key(pcopy.private, &dh_inputs.key);
304         if (dlen < 0) {
305                 ret = dlen;
306                 goto out2;
307         }
308         dh_inputs.key_size = dlen;
309 
310         secretlen = crypto_dh_key_len(&dh_inputs);
311         secret = kmalloc(secretlen, GFP_KERNEL);
312         if (!secret) {
313                 ret = -ENOMEM;
314                 goto out2;
315         }
316         ret = crypto_dh_encode_key(secret, secretlen, &dh_inputs);
317         if (ret)
318                 goto out3;
319 
320         tfm = crypto_alloc_kpp("dh", 0, 0);
321         if (IS_ERR(tfm)) {
322                 ret = PTR_ERR(tfm);
323                 goto out3;
324         }
325 
326         ret = crypto_kpp_set_secret(tfm, secret, secretlen);
327         if (ret)
328                 goto out4;
329 
330         outlen = crypto_kpp_maxsize(tfm);
331 
332         if (!kdfcopy) {
333                 /*
334                  * When not using a KDF, buflen 0 is used to read the
335                  * required buffer length
336                  */
337                 if (buflen == 0) {
338                         ret = outlen;
339                         goto out4;
340                 } else if (outlen > buflen) {
341                         ret = -EOVERFLOW;
342                         goto out4;
343                 }
344         }
345 
346         outbuf = kzalloc(kdfcopy ? (outlen + kdfcopy->otherinfolen) : outlen,
347                          GFP_KERNEL);
348         if (!outbuf) {
349                 ret = -ENOMEM;
350                 goto out4;
351         }
352 
353         sg_init_one(&outsg, outbuf, outlen);
354 
355         req = kpp_request_alloc(tfm, GFP_KERNEL);
356         if (!req) {
357                 ret = -ENOMEM;
358                 goto out5;
359         }
360 
361         kpp_request_set_input(req, NULL, 0);
362         kpp_request_set_output(req, &outsg, outlen);
363         init_completion(&compl.completion);
364         kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
365                                  CRYPTO_TFM_REQ_MAY_SLEEP,
366                                  dh_crypto_done, &compl);
367 
368         /*
369          * For DH, generate_public_key and generate_shared_secret are
370          * the same calculation
371          */
372         ret = crypto_kpp_generate_public_key(req);
373         if (ret == -EINPROGRESS) {
374                 wait_for_completion(&compl.completion);
375                 ret = compl.err;
376                 if (ret)
377                         goto out6;
378         }
379 
380         if (kdfcopy) {
381                 /*
382                  * Concatenate SP800-56A otherinfo past DH shared secret -- the
383                  * input to the KDF is (DH shared secret || otherinfo)
384                  */
385                 if (copy_from_user(outbuf + req->dst_len, kdfcopy->otherinfo,
386                                    kdfcopy->otherinfolen) != 0) {
387                         ret = -EFAULT;
388                         goto out6;
389                 }
390 
391                 ret = keyctl_dh_compute_kdf(sdesc, buffer, buflen, outbuf,
392                                             req->dst_len + kdfcopy->otherinfolen,
393                                             outlen - req->dst_len);
394         } else if (copy_to_user(buffer, outbuf, req->dst_len) == 0) {
395                 ret = req->dst_len;
396         } else {
397                 ret = -EFAULT;
398         }
399 
400 out6:
401         kpp_request_free(req);
402 out5:
403         kzfree(outbuf);
404 out4:
405         crypto_free_kpp(tfm);
406 out3:
407         kzfree(secret);
408 out2:
409         dh_free_data(&dh_inputs);
410 out1:
411         kdf_dealloc(sdesc);
412         return ret;
413 }
414 
415 long keyctl_dh_compute(struct keyctl_dh_params __user *params,
416                        char __user *buffer, size_t buflen,
417                        struct keyctl_kdf_params __user *kdf)
418 {
419         struct keyctl_kdf_params kdfcopy;
420 
421         if (!kdf)
422                 return __keyctl_dh_compute(params, buffer, buflen, NULL);
423 
424         if (copy_from_user(&kdfcopy, kdf, sizeof(kdfcopy)) != 0)
425                 return -EFAULT;
426 
427         return __keyctl_dh_compute(params, buffer, buflen, &kdfcopy);
428 }
429 

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