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 static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen, 147 u8 *dst, unsigned int dlen, unsigned int zlen) 148 { 149 struct shash_desc *desc = &sdesc->shash; 150 unsigned int h = crypto_shash_digestsize(desc->tfm); 151 int err = 0; 152 u8 *dst_orig = dst; 153 __be32 counter = cpu_to_be32(1); 154 155 while (dlen) { 156 err = crypto_shash_init(desc); 157 if (err) 158 goto err; 159 160 err = crypto_shash_update(desc, (u8 *)&counter, sizeof(__be32)); 161 if (err) 162 goto err; 163 164 if (zlen && h) { 165 u8 tmpbuffer[h]; 166 size_t chunk = min_t(size_t, zlen, h); 167 memset(tmpbuffer, 0, chunk); 168 169 do { 170 err = crypto_shash_update(desc, tmpbuffer, 171 chunk); 172 if (err) 173 goto err; 174 175 zlen -= chunk; 176 chunk = min_t(size_t, zlen, h); 177 } while (zlen); 178 } 179 180 if (src && slen) { 181 err = crypto_shash_update(desc, src, slen); 182 if (err) 183 goto err; 184 } 185 186 if (dlen < h) { 187 u8 tmpbuffer[h]; 188 189 err = crypto_shash_final(desc, tmpbuffer); 190 if (err) 191 goto err; 192 memcpy(dst, tmpbuffer, dlen); 193 memzero_explicit(tmpbuffer, h); 194 return 0; 195 } else { 196 err = crypto_shash_final(desc, dst); 197 if (err) 198 goto err; 199 200 dlen -= h; 201 dst += h; 202 counter = cpu_to_be32(be32_to_cpu(counter) + 1); 203 } 204 } 205 206 return 0; 207 208 err: 209 memzero_explicit(dst_orig, dlen); 210 return err; 211 } 212 213 static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc, 214 char __user *buffer, size_t buflen, 215 uint8_t *kbuf, size_t kbuflen, size_t lzero) 216 { 217 uint8_t *outbuf = NULL; 218 int ret; 219 220 outbuf = kmalloc(buflen, GFP_KERNEL); 221 if (!outbuf) { 222 ret = -ENOMEM; 223 goto err; 224 } 225 226 ret = kdf_ctr(sdesc, kbuf, kbuflen, outbuf, buflen, lzero); 227 if (ret) 228 goto err; 229 230 ret = buflen; 231 if (copy_to_user(buffer, outbuf, buflen) != 0) 232 ret = -EFAULT; 233 234 err: 235 kzfree(outbuf); 236 return ret; 237 } 238 239 long __keyctl_dh_compute(struct keyctl_dh_params __user *params, 240 char __user *buffer, size_t buflen, 241 struct keyctl_kdf_params *kdfcopy) 242 { 243 long ret; 244 ssize_t dlen; 245 int secretlen; 246 int outlen; 247 struct keyctl_dh_params pcopy; 248 struct dh dh_inputs; 249 struct scatterlist outsg; 250 struct dh_completion compl; 251 struct crypto_kpp *tfm; 252 struct kpp_request *req; 253 uint8_t *secret; 254 uint8_t *outbuf; 255 struct kdf_sdesc *sdesc = NULL; 256 257 if (!params || (!buffer && buflen)) { 258 ret = -EINVAL; 259 goto out1; 260 } 261 if (copy_from_user(&pcopy, params, sizeof(pcopy)) != 0) { 262 ret = -EFAULT; 263 goto out1; 264 } 265 266 if (kdfcopy) { 267 char *hashname; 268 269 if (buflen > KEYCTL_KDF_MAX_OUTPUT_LEN || 270 kdfcopy->otherinfolen > KEYCTL_KDF_MAX_OI_LEN) { 271 ret = -EMSGSIZE; 272 goto out1; 273 } 274 275 /* get KDF name string */ 276 hashname = strndup_user(kdfcopy->hashname, CRYPTO_MAX_ALG_NAME); 277 if (IS_ERR(hashname)) { 278 ret = PTR_ERR(hashname); 279 goto out1; 280 } 281 282 /* allocate KDF from the kernel crypto API */ 283 ret = kdf_alloc(&sdesc, hashname); 284 kfree(hashname); 285 if (ret) 286 goto out1; 287 } 288 289 memset(&dh_inputs, 0, sizeof(dh_inputs)); 290 291 dlen = dh_data_from_key(pcopy.prime, &dh_inputs.p); 292 if (dlen < 0) { 293 ret = dlen; 294 goto out1; 295 } 296 dh_inputs.p_size = dlen; 297 298 dlen = dh_data_from_key(pcopy.base, &dh_inputs.g); 299 if (dlen < 0) { 300 ret = dlen; 301 goto out2; 302 } 303 dh_inputs.g_size = dlen; 304 305 dlen = dh_data_from_key(pcopy.private, &dh_inputs.key); 306 if (dlen < 0) { 307 ret = dlen; 308 goto out2; 309 } 310 dh_inputs.key_size = dlen; 311 312 secretlen = crypto_dh_key_len(&dh_inputs); 313 secret = kmalloc(secretlen, GFP_KERNEL); 314 if (!secret) { 315 ret = -ENOMEM; 316 goto out2; 317 } 318 ret = crypto_dh_encode_key(secret, secretlen, &dh_inputs); 319 if (ret) 320 goto out3; 321 322 tfm = crypto_alloc_kpp("dh", CRYPTO_ALG_TYPE_KPP, 0); 323 if (IS_ERR(tfm)) { 324 ret = PTR_ERR(tfm); 325 goto out3; 326 } 327 328 ret = crypto_kpp_set_secret(tfm, secret, secretlen); 329 if (ret) 330 goto out4; 331 332 outlen = crypto_kpp_maxsize(tfm); 333 334 if (!kdfcopy) { 335 /* 336 * When not using a KDF, buflen 0 is used to read the 337 * required buffer length 338 */ 339 if (buflen == 0) { 340 ret = outlen; 341 goto out4; 342 } else if (outlen > buflen) { 343 ret = -EOVERFLOW; 344 goto out4; 345 } 346 } 347 348 outbuf = kzalloc(kdfcopy ? (outlen + kdfcopy->otherinfolen) : outlen, 349 GFP_KERNEL); 350 if (!outbuf) { 351 ret = -ENOMEM; 352 goto out4; 353 } 354 355 sg_init_one(&outsg, outbuf, outlen); 356 357 req = kpp_request_alloc(tfm, GFP_KERNEL); 358 if (!req) { 359 ret = -ENOMEM; 360 goto out5; 361 } 362 363 kpp_request_set_input(req, NULL, 0); 364 kpp_request_set_output(req, &outsg, outlen); 365 init_completion(&compl.completion); 366 kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG | 367 CRYPTO_TFM_REQ_MAY_SLEEP, 368 dh_crypto_done, &compl); 369 370 /* 371 * For DH, generate_public_key and generate_shared_secret are 372 * the same calculation 373 */ 374 ret = crypto_kpp_generate_public_key(req); 375 if (ret == -EINPROGRESS) { 376 wait_for_completion(&compl.completion); 377 ret = compl.err; 378 if (ret) 379 goto out6; 380 } 381 382 if (kdfcopy) { 383 /* 384 * Concatenate SP800-56A otherinfo past DH shared secret -- the 385 * input to the KDF is (DH shared secret || otherinfo) 386 */ 387 if (copy_from_user(outbuf + req->dst_len, kdfcopy->otherinfo, 388 kdfcopy->otherinfolen) != 0) { 389 ret = -EFAULT; 390 goto out6; 391 } 392 393 ret = keyctl_dh_compute_kdf(sdesc, buffer, buflen, outbuf, 394 req->dst_len + kdfcopy->otherinfolen, 395 outlen - req->dst_len); 396 } else if (copy_to_user(buffer, outbuf, req->dst_len) == 0) { 397 ret = req->dst_len; 398 } else { 399 ret = -EFAULT; 400 } 401 402 out6: 403 kpp_request_free(req); 404 out5: 405 kzfree(outbuf); 406 out4: 407 crypto_free_kpp(tfm); 408 out3: 409 kzfree(secret); 410 out2: 411 dh_free_data(&dh_inputs); 412 out1: 413 kdf_dealloc(sdesc); 414 return ret; 415 } 416 417 long keyctl_dh_compute(struct keyctl_dh_params __user *params, 418 char __user *buffer, size_t buflen, 419 struct keyctl_kdf_params __user *kdf) 420 { 421 struct keyctl_kdf_params kdfcopy; 422 423 if (!kdf) 424 return __keyctl_dh_compute(params, buffer, buflen, NULL); 425 426 if (copy_from_user(&kdfcopy, kdf, sizeof(kdfcopy)) != 0) 427 return -EFAULT; 428 429 return __keyctl_dh_compute(params, buffer, buflen, &kdfcopy); 430 } 431