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; 115 116 *sdesc_ret = sdesc; 117 118 return 0; 119 120 out_free_tfm: 121 crypto_free_shash(tfm); 122 return err; 123 } 124 125 static void kdf_dealloc(struct kdf_sdesc *sdesc) 126 { 127 if (!sdesc) 128 return; 129 130 if (sdesc->shash.tfm) 131 crypto_free_shash(sdesc->shash.tfm); 132 133 kzfree(sdesc); 134 } 135 136 /* 137 * Implementation of the KDF in counter mode according to SP800-108 section 5.1 138 * as well as SP800-56A section 5.8.1 (Single-step KDF). 139 * 140 * SP800-56A: 141 * The src pointer is defined as Z || other info where Z is the shared secret 142 * from DH and other info is an arbitrary string (see SP800-56A section 143 * 5.8.1.2). 144 * 145 * 'dlen' must be a multiple of the digest size. 146 */ 147 static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen, 148 u8 *dst, unsigned int dlen, unsigned int zlen) 149 { 150 struct shash_desc *desc = &sdesc->shash; 151 unsigned int h = crypto_shash_digestsize(desc->tfm); 152 int err = 0; 153 u8 *dst_orig = dst; 154 __be32 counter = cpu_to_be32(1); 155 156 while (dlen) { 157 err = crypto_shash_init(desc); 158 if (err) 159 goto err; 160 161 err = crypto_shash_update(desc, (u8 *)&counter, sizeof(__be32)); 162 if (err) 163 goto err; 164 165 if (zlen && h) { 166 u8 tmpbuffer[32]; 167 size_t chunk = min_t(size_t, zlen, sizeof(tmpbuffer)); 168 memset(tmpbuffer, 0, chunk); 169 170 do { 171 err = crypto_shash_update(desc, tmpbuffer, 172 chunk); 173 if (err) 174 goto err; 175 176 zlen -= chunk; 177 chunk = min_t(size_t, zlen, sizeof(tmpbuffer)); 178 } while (zlen); 179 } 180 181 if (src && slen) { 182 err = crypto_shash_update(desc, src, slen); 183 if (err) 184 goto err; 185 } 186 187 err = crypto_shash_final(desc, dst); 188 if (err) 189 goto err; 190 191 dlen -= h; 192 dst += h; 193 counter = cpu_to_be32(be32_to_cpu(counter) + 1); 194 } 195 196 return 0; 197 198 err: 199 memzero_explicit(dst_orig, dlen); 200 return err; 201 } 202 203 static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc, 204 char __user *buffer, size_t buflen, 205 uint8_t *kbuf, size_t kbuflen, size_t lzero) 206 { 207 uint8_t *outbuf = NULL; 208 int ret; 209 size_t outbuf_len = roundup(buflen, 210 crypto_shash_digestsize(sdesc->shash.tfm)); 211 212 outbuf = kmalloc(outbuf_len, GFP_KERNEL); 213 if (!outbuf) { 214 ret = -ENOMEM; 215 goto err; 216 } 217 218 ret = kdf_ctr(sdesc, kbuf, kbuflen, outbuf, outbuf_len, lzero); 219 if (ret) 220 goto err; 221 222 ret = buflen; 223 if (copy_to_user(buffer, outbuf, buflen) != 0) 224 ret = -EFAULT; 225 226 err: 227 kzfree(outbuf); 228 return ret; 229 } 230 231 long __keyctl_dh_compute(struct keyctl_dh_params __user *params, 232 char __user *buffer, size_t buflen, 233 struct keyctl_kdf_params *kdfcopy) 234 { 235 long ret; 236 ssize_t dlen; 237 int secretlen; 238 int outlen; 239 struct keyctl_dh_params pcopy; 240 struct dh dh_inputs; 241 struct scatterlist outsg; 242 struct dh_completion compl; 243 struct crypto_kpp *tfm; 244 struct kpp_request *req; 245 uint8_t *secret; 246 uint8_t *outbuf; 247 struct kdf_sdesc *sdesc = NULL; 248 249 if (!params || (!buffer && buflen)) { 250 ret = -EINVAL; 251 goto out1; 252 } 253 if (copy_from_user(&pcopy, params, sizeof(pcopy)) != 0) { 254 ret = -EFAULT; 255 goto out1; 256 } 257 258 if (kdfcopy) { 259 char *hashname; 260 261 if (memchr_inv(kdfcopy->__spare, 0, sizeof(kdfcopy->__spare))) { 262 ret = -EINVAL; 263 goto out1; 264 } 265 266 if (buflen > KEYCTL_KDF_MAX_OUTPUT_LEN || 267 kdfcopy->otherinfolen > KEYCTL_KDF_MAX_OI_LEN) { 268 ret = -EMSGSIZE; 269 goto out1; 270 } 271 272 /* get KDF name string */ 273 hashname = strndup_user(kdfcopy->hashname, CRYPTO_MAX_ALG_NAME); 274 if (IS_ERR(hashname)) { 275 ret = PTR_ERR(hashname); 276 goto out1; 277 } 278 279 /* allocate KDF from the kernel crypto API */ 280 ret = kdf_alloc(&sdesc, hashname); 281 kfree(hashname); 282 if (ret) 283 goto out1; 284 } 285 286 memset(&dh_inputs, 0, sizeof(dh_inputs)); 287 288 dlen = dh_data_from_key(pcopy.prime, &dh_inputs.p); 289 if (dlen < 0) { 290 ret = dlen; 291 goto out1; 292 } 293 dh_inputs.p_size = dlen; 294 295 dlen = dh_data_from_key(pcopy.base, &dh_inputs.g); 296 if (dlen < 0) { 297 ret = dlen; 298 goto out2; 299 } 300 dh_inputs.g_size = dlen; 301 302 dlen = dh_data_from_key(pcopy.private, &dh_inputs.key); 303 if (dlen < 0) { 304 ret = dlen; 305 goto out2; 306 } 307 dh_inputs.key_size = dlen; 308 309 secretlen = crypto_dh_key_len(&dh_inputs); 310 secret = kmalloc(secretlen, GFP_KERNEL); 311 if (!secret) { 312 ret = -ENOMEM; 313 goto out2; 314 } 315 ret = crypto_dh_encode_key(secret, secretlen, &dh_inputs); 316 if (ret) 317 goto out3; 318 319 tfm = crypto_alloc_kpp("dh", 0, 0); 320 if (IS_ERR(tfm)) { 321 ret = PTR_ERR(tfm); 322 goto out3; 323 } 324 325 ret = crypto_kpp_set_secret(tfm, secret, secretlen); 326 if (ret) 327 goto out4; 328 329 outlen = crypto_kpp_maxsize(tfm); 330 331 if (!kdfcopy) { 332 /* 333 * When not using a KDF, buflen 0 is used to read the 334 * required buffer length 335 */ 336 if (buflen == 0) { 337 ret = outlen; 338 goto out4; 339 } else if (outlen > buflen) { 340 ret = -EOVERFLOW; 341 goto out4; 342 } 343 } 344 345 outbuf = kzalloc(kdfcopy ? (outlen + kdfcopy->otherinfolen) : outlen, 346 GFP_KERNEL); 347 if (!outbuf) { 348 ret = -ENOMEM; 349 goto out4; 350 } 351 352 sg_init_one(&outsg, outbuf, outlen); 353 354 req = kpp_request_alloc(tfm, GFP_KERNEL); 355 if (!req) { 356 ret = -ENOMEM; 357 goto out5; 358 } 359 360 kpp_request_set_input(req, NULL, 0); 361 kpp_request_set_output(req, &outsg, outlen); 362 init_completion(&compl.completion); 363 kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG | 364 CRYPTO_TFM_REQ_MAY_SLEEP, 365 dh_crypto_done, &compl); 366 367 /* 368 * For DH, generate_public_key and generate_shared_secret are 369 * the same calculation 370 */ 371 ret = crypto_kpp_generate_public_key(req); 372 if (ret == -EINPROGRESS) { 373 wait_for_completion(&compl.completion); 374 ret = compl.err; 375 if (ret) 376 goto out6; 377 } 378 379 if (kdfcopy) { 380 /* 381 * Concatenate SP800-56A otherinfo past DH shared secret -- the 382 * input to the KDF is (DH shared secret || otherinfo) 383 */ 384 if (copy_from_user(outbuf + req->dst_len, kdfcopy->otherinfo, 385 kdfcopy->otherinfolen) != 0) { 386 ret = -EFAULT; 387 goto out6; 388 } 389 390 ret = keyctl_dh_compute_kdf(sdesc, buffer, buflen, outbuf, 391 req->dst_len + kdfcopy->otherinfolen, 392 outlen - req->dst_len); 393 } else if (copy_to_user(buffer, outbuf, req->dst_len) == 0) { 394 ret = req->dst_len; 395 } else { 396 ret = -EFAULT; 397 } 398 399 out6: 400 kpp_request_free(req); 401 out5: 402 kzfree(outbuf); 403 out4: 404 crypto_free_kpp(tfm); 405 out3: 406 kzfree(secret); 407 out2: 408 dh_free_data(&dh_inputs); 409 out1: 410 kdf_dealloc(sdesc); 411 return ret; 412 } 413 414 long keyctl_dh_compute(struct keyctl_dh_params __user *params, 415 char __user *buffer, size_t buflen, 416 struct keyctl_kdf_params __user *kdf) 417 { 418 struct keyctl_kdf_params kdfcopy; 419 420 if (!kdf) 421 return __keyctl_dh_compute(params, buffer, buflen, NULL); 422 423 if (copy_from_user(&kdfcopy, kdf, sizeof(kdfcopy)) != 0) 424 return -EFAULT; 425 426 return __keyctl_dh_compute(params, buffer, buflen, &kdfcopy); 427 } 428