1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* In-software asymmetric public-key crypto subtype 3 * 4 * See Documentation/crypto/asymmetric-keys.rst 5 * 6 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. 7 * Written by David Howells (dhowells@redhat.com) 8 */ 9 10 #define pr_fmt(fmt) "PKEY: "fmt 11 #include <crypto/akcipher.h> 12 #include <crypto/public_key.h> 13 #include <crypto/sig.h> 14 #include <keys/asymmetric-subtype.h> 15 #include <linux/asn1.h> 16 #include <linux/err.h> 17 #include <linux/kernel.h> 18 #include <linux/module.h> 19 #include <linux/seq_file.h> 20 #include <linux/slab.h> 21 #include <linux/string.h> 22 23 MODULE_DESCRIPTION("In-software asymmetric public-key subtype"); 24 MODULE_AUTHOR("Red Hat, Inc."); 25 MODULE_LICENSE("GPL"); 26 27 /* 28 * Provide a part of a description of the key for /proc/keys. 29 */ 30 static void public_key_describe(const struct key *asymmetric_key, 31 struct seq_file *m) 32 { 33 struct public_key *key = asymmetric_key->payload.data[asym_crypto]; 34 35 if (key) 36 seq_printf(m, "%s.%s", key->id_type, key->pkey_algo); 37 } 38 39 /* 40 * Destroy a public key algorithm key. 41 */ 42 void public_key_free(struct public_key *key) 43 { 44 if (key) { 45 kfree_sensitive(key->key); 46 kfree(key->params); 47 kfree(key); 48 } 49 } 50 EXPORT_SYMBOL_GPL(public_key_free); 51 52 /* 53 * Destroy a public key algorithm key. 54 */ 55 static void public_key_destroy(void *payload0, void *payload3) 56 { 57 public_key_free(payload0); 58 public_key_signature_free(payload3); 59 } 60 61 /* 62 * Given a public_key, and an encoding and hash_algo to be used for signing 63 * and/or verification with that key, determine the name of the corresponding 64 * akcipher algorithm. Also check that encoding and hash_algo are allowed. 65 */ 66 static int 67 software_key_determine_akcipher(const struct public_key *pkey, 68 const char *encoding, const char *hash_algo, 69 char alg_name[CRYPTO_MAX_ALG_NAME], bool *sig, 70 enum kernel_pkey_operation op) 71 { 72 int n; 73 74 *sig = true; 75 76 if (!encoding) 77 return -EINVAL; 78 79 if (strcmp(pkey->pkey_algo, "rsa") == 0) { 80 /* 81 * RSA signatures usually use EMSA-PKCS1-1_5 [RFC3447 sec 8.2]. 82 */ 83 if (strcmp(encoding, "pkcs1") == 0) { 84 *sig = op == kernel_pkey_sign || 85 op == kernel_pkey_verify; 86 if (!hash_algo) { 87 n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME, 88 "pkcs1pad(%s)", 89 pkey->pkey_algo); 90 } else { 91 n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME, 92 "pkcs1pad(%s,%s)", 93 pkey->pkey_algo, hash_algo); 94 } 95 return n >= CRYPTO_MAX_ALG_NAME ? -EINVAL : 0; 96 } 97 if (strcmp(encoding, "raw") != 0) 98 return -EINVAL; 99 /* 100 * Raw RSA cannot differentiate between different hash 101 * algorithms. 102 */ 103 if (hash_algo) 104 return -EINVAL; 105 *sig = false; 106 } else if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) { 107 if (strcmp(encoding, "x962") != 0) 108 return -EINVAL; 109 /* 110 * ECDSA signatures are taken over a raw hash, so they don't 111 * differentiate between different hash algorithms. That means 112 * that the verifier should hard-code a specific hash algorithm. 113 * Unfortunately, in practice ECDSA is used with multiple SHAs, 114 * so we have to allow all of them and not just one. 115 */ 116 if (!hash_algo) 117 return -EINVAL; 118 if (strcmp(hash_algo, "sha1") != 0 && 119 strcmp(hash_algo, "sha224") != 0 && 120 strcmp(hash_algo, "sha256") != 0 && 121 strcmp(hash_algo, "sha384") != 0 && 122 strcmp(hash_algo, "sha512") != 0 && 123 strcmp(hash_algo, "sha3-256") != 0 && 124 strcmp(hash_algo, "sha3-384") != 0 && 125 strcmp(hash_algo, "sha3-512") != 0) 126 return -EINVAL; 127 } else if (strcmp(pkey->pkey_algo, "sm2") == 0) { 128 if (strcmp(encoding, "raw") != 0) 129 return -EINVAL; 130 if (!hash_algo) 131 return -EINVAL; 132 if (strcmp(hash_algo, "sm3") != 0) 133 return -EINVAL; 134 } else if (strcmp(pkey->pkey_algo, "ecrdsa") == 0) { 135 if (strcmp(encoding, "raw") != 0) 136 return -EINVAL; 137 if (!hash_algo) 138 return -EINVAL; 139 if (strcmp(hash_algo, "streebog256") != 0 && 140 strcmp(hash_algo, "streebog512") != 0) 141 return -EINVAL; 142 } else { 143 /* Unknown public key algorithm */ 144 return -ENOPKG; 145 } 146 if (strscpy(alg_name, pkey->pkey_algo, CRYPTO_MAX_ALG_NAME) < 0) 147 return -EINVAL; 148 return 0; 149 } 150 151 static u8 *pkey_pack_u32(u8 *dst, u32 val) 152 { 153 memcpy(dst, &val, sizeof(val)); 154 return dst + sizeof(val); 155 } 156 157 /* 158 * Query information about a key. 159 */ 160 static int software_key_query(const struct kernel_pkey_params *params, 161 struct kernel_pkey_query *info) 162 { 163 struct crypto_akcipher *tfm; 164 struct public_key *pkey = params->key->payload.data[asym_crypto]; 165 char alg_name[CRYPTO_MAX_ALG_NAME]; 166 struct crypto_sig *sig; 167 u8 *key, *ptr; 168 int ret, len; 169 bool issig; 170 171 ret = software_key_determine_akcipher(pkey, params->encoding, 172 params->hash_algo, alg_name, 173 &issig, kernel_pkey_sign); 174 if (ret < 0) 175 return ret; 176 177 key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen, 178 GFP_KERNEL); 179 if (!key) 180 return -ENOMEM; 181 182 memcpy(key, pkey->key, pkey->keylen); 183 ptr = key + pkey->keylen; 184 ptr = pkey_pack_u32(ptr, pkey->algo); 185 ptr = pkey_pack_u32(ptr, pkey->paramlen); 186 memcpy(ptr, pkey->params, pkey->paramlen); 187 188 if (issig) { 189 sig = crypto_alloc_sig(alg_name, 0, 0); 190 if (IS_ERR(sig)) { 191 ret = PTR_ERR(sig); 192 goto error_free_key; 193 } 194 195 if (pkey->key_is_private) 196 ret = crypto_sig_set_privkey(sig, key, pkey->keylen); 197 else 198 ret = crypto_sig_set_pubkey(sig, key, pkey->keylen); 199 if (ret < 0) 200 goto error_free_tfm; 201 202 len = crypto_sig_maxsize(sig); 203 204 info->supported_ops = KEYCTL_SUPPORTS_VERIFY; 205 if (pkey->key_is_private) 206 info->supported_ops |= KEYCTL_SUPPORTS_SIGN; 207 208 if (strcmp(params->encoding, "pkcs1") == 0) { 209 info->supported_ops |= KEYCTL_SUPPORTS_ENCRYPT; 210 if (pkey->key_is_private) 211 info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT; 212 } 213 } else { 214 tfm = crypto_alloc_akcipher(alg_name, 0, 0); 215 if (IS_ERR(tfm)) { 216 ret = PTR_ERR(tfm); 217 goto error_free_key; 218 } 219 220 if (pkey->key_is_private) 221 ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen); 222 else 223 ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen); 224 if (ret < 0) 225 goto error_free_tfm; 226 227 len = crypto_akcipher_maxsize(tfm); 228 229 info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT; 230 if (pkey->key_is_private) 231 info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT; 232 } 233 234 info->key_size = len * 8; 235 236 if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) { 237 int slen = len; 238 /* 239 * ECDSA key sizes are much smaller than RSA, and thus could 240 * operate on (hashed) inputs that are larger than key size. 241 * For example SHA384-hashed input used with secp256r1 242 * based keys. Set max_data_size to be at least as large as 243 * the largest supported hash size (SHA512) 244 */ 245 info->max_data_size = 64; 246 247 /* 248 * Verify takes ECDSA-Sig (described in RFC 5480) as input, 249 * which is actually 2 'key_size'-bit integers encoded in 250 * ASN.1. Account for the ASN.1 encoding overhead here. 251 * 252 * NIST P192/256/384 may prepend a '0' to a coordinate to 253 * indicate a positive integer. NIST P521 never needs it. 254 */ 255 if (strcmp(pkey->pkey_algo, "ecdsa-nist-p521") != 0) 256 slen += 1; 257 /* Length of encoding the x & y coordinates */ 258 slen = 2 * (slen + 2); 259 /* 260 * If coordinate encoding takes at least 128 bytes then an 261 * additional byte for length encoding is needed. 262 */ 263 info->max_sig_size = 1 + (slen >= 128) + 1 + slen; 264 } else { 265 info->max_data_size = len; 266 info->max_sig_size = len; 267 } 268 269 info->max_enc_size = len; 270 info->max_dec_size = len; 271 272 ret = 0; 273 274 error_free_tfm: 275 if (issig) 276 crypto_free_sig(sig); 277 else 278 crypto_free_akcipher(tfm); 279 error_free_key: 280 kfree_sensitive(key); 281 pr_devel("<==%s() = %d\n", __func__, ret); 282 return ret; 283 } 284 285 /* 286 * Do encryption, decryption and signing ops. 287 */ 288 static int software_key_eds_op(struct kernel_pkey_params *params, 289 const void *in, void *out) 290 { 291 const struct public_key *pkey = params->key->payload.data[asym_crypto]; 292 char alg_name[CRYPTO_MAX_ALG_NAME]; 293 struct crypto_akcipher *tfm; 294 struct crypto_sig *sig; 295 char *key, *ptr; 296 bool issig; 297 int ksz; 298 int ret; 299 300 pr_devel("==>%s()\n", __func__); 301 302 ret = software_key_determine_akcipher(pkey, params->encoding, 303 params->hash_algo, alg_name, 304 &issig, params->op); 305 if (ret < 0) 306 return ret; 307 308 key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen, 309 GFP_KERNEL); 310 if (!key) 311 return -ENOMEM; 312 313 memcpy(key, pkey->key, pkey->keylen); 314 ptr = key + pkey->keylen; 315 ptr = pkey_pack_u32(ptr, pkey->algo); 316 ptr = pkey_pack_u32(ptr, pkey->paramlen); 317 memcpy(ptr, pkey->params, pkey->paramlen); 318 319 if (issig) { 320 sig = crypto_alloc_sig(alg_name, 0, 0); 321 if (IS_ERR(sig)) { 322 ret = PTR_ERR(sig); 323 goto error_free_key; 324 } 325 326 if (pkey->key_is_private) 327 ret = crypto_sig_set_privkey(sig, key, pkey->keylen); 328 else 329 ret = crypto_sig_set_pubkey(sig, key, pkey->keylen); 330 if (ret) 331 goto error_free_tfm; 332 333 ksz = crypto_sig_maxsize(sig); 334 } else { 335 tfm = crypto_alloc_akcipher(alg_name, 0, 0); 336 if (IS_ERR(tfm)) { 337 ret = PTR_ERR(tfm); 338 goto error_free_key; 339 } 340 341 if (pkey->key_is_private) 342 ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen); 343 else 344 ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen); 345 if (ret) 346 goto error_free_tfm; 347 348 ksz = crypto_akcipher_maxsize(tfm); 349 } 350 351 ret = -EINVAL; 352 353 /* Perform the encryption calculation. */ 354 switch (params->op) { 355 case kernel_pkey_encrypt: 356 if (issig) 357 break; 358 ret = crypto_akcipher_sync_encrypt(tfm, in, params->in_len, 359 out, params->out_len); 360 break; 361 case kernel_pkey_decrypt: 362 if (issig) 363 break; 364 ret = crypto_akcipher_sync_decrypt(tfm, in, params->in_len, 365 out, params->out_len); 366 break; 367 case kernel_pkey_sign: 368 if (!issig) 369 break; 370 ret = crypto_sig_sign(sig, in, params->in_len, 371 out, params->out_len); 372 break; 373 default: 374 BUG(); 375 } 376 377 if (ret == 0) 378 ret = ksz; 379 380 error_free_tfm: 381 if (issig) 382 crypto_free_sig(sig); 383 else 384 crypto_free_akcipher(tfm); 385 error_free_key: 386 kfree_sensitive(key); 387 pr_devel("<==%s() = %d\n", __func__, ret); 388 return ret; 389 } 390 391 /* 392 * Verify a signature using a public key. 393 */ 394 int public_key_verify_signature(const struct public_key *pkey, 395 const struct public_key_signature *sig) 396 { 397 char alg_name[CRYPTO_MAX_ALG_NAME]; 398 struct crypto_sig *tfm; 399 char *key, *ptr; 400 bool issig; 401 int ret; 402 403 pr_devel("==>%s()\n", __func__); 404 405 BUG_ON(!pkey); 406 BUG_ON(!sig); 407 BUG_ON(!sig->s); 408 409 /* 410 * If the signature specifies a public key algorithm, it *must* match 411 * the key's actual public key algorithm. 412 * 413 * Small exception: ECDSA signatures don't specify the curve, but ECDSA 414 * keys do. So the strings can mismatch slightly in that case: 415 * "ecdsa-nist-*" for the key, but "ecdsa" for the signature. 416 */ 417 if (sig->pkey_algo) { 418 if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 && 419 (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 || 420 strcmp(sig->pkey_algo, "ecdsa") != 0)) 421 return -EKEYREJECTED; 422 } 423 424 ret = software_key_determine_akcipher(pkey, sig->encoding, 425 sig->hash_algo, alg_name, 426 &issig, kernel_pkey_verify); 427 if (ret < 0) 428 return ret; 429 430 tfm = crypto_alloc_sig(alg_name, 0, 0); 431 if (IS_ERR(tfm)) 432 return PTR_ERR(tfm); 433 434 key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen, 435 GFP_KERNEL); 436 if (!key) { 437 ret = -ENOMEM; 438 goto error_free_tfm; 439 } 440 441 memcpy(key, pkey->key, pkey->keylen); 442 ptr = key + pkey->keylen; 443 ptr = pkey_pack_u32(ptr, pkey->algo); 444 ptr = pkey_pack_u32(ptr, pkey->paramlen); 445 memcpy(ptr, pkey->params, pkey->paramlen); 446 447 if (pkey->key_is_private) 448 ret = crypto_sig_set_privkey(tfm, key, pkey->keylen); 449 else 450 ret = crypto_sig_set_pubkey(tfm, key, pkey->keylen); 451 if (ret) 452 goto error_free_key; 453 454 ret = crypto_sig_verify(tfm, sig->s, sig->s_size, 455 sig->digest, sig->digest_size); 456 457 error_free_key: 458 kfree_sensitive(key); 459 error_free_tfm: 460 crypto_free_sig(tfm); 461 pr_devel("<==%s() = %d\n", __func__, ret); 462 if (WARN_ON_ONCE(ret > 0)) 463 ret = -EINVAL; 464 return ret; 465 } 466 EXPORT_SYMBOL_GPL(public_key_verify_signature); 467 468 static int public_key_verify_signature_2(const struct key *key, 469 const struct public_key_signature *sig) 470 { 471 const struct public_key *pk = key->payload.data[asym_crypto]; 472 return public_key_verify_signature(pk, sig); 473 } 474 475 /* 476 * Public key algorithm asymmetric key subtype 477 */ 478 struct asymmetric_key_subtype public_key_subtype = { 479 .owner = THIS_MODULE, 480 .name = "public_key", 481 .name_len = sizeof("public_key") - 1, 482 .describe = public_key_describe, 483 .destroy = public_key_destroy, 484 .query = software_key_query, 485 .eds_op = software_key_eds_op, 486 .verify_signature = public_key_verify_signature_2, 487 }; 488 EXPORT_SYMBOL_GPL(public_key_subtype); 489