1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * RSA Signature Scheme with Appendix - PKCS #1 v1.5 (RFC 8017 sec 8.2) 4 * 5 * https://www.rfc-editor.org/rfc/rfc8017#section-8.2 6 * 7 * Copyright (c) 2015 - 2024 Intel Corporation 8 */ 9 10 #include <linux/module.h> 11 #include <linux/scatterlist.h> 12 #include <crypto/akcipher.h> 13 #include <crypto/algapi.h> 14 #include <crypto/hash.h> 15 #include <crypto/sig.h> 16 #include <crypto/internal/akcipher.h> 17 #include <crypto/internal/rsa.h> 18 #include <crypto/internal/sig.h> 19 20 /* 21 * Full Hash Prefix for EMSA-PKCS1-v1_5 encoding method (RFC 9580 table 24) 22 * 23 * RSA keys are usually much larger than the hash of the message to be signed. 24 * The hash is therefore prepended by the Full Hash Prefix and a 0xff padding. 25 * The Full Hash Prefix is an ASN.1 SEQUENCE containing the hash algorithm OID. 26 * 27 * https://www.rfc-editor.org/rfc/rfc9580#table-24 28 */ 29 30 static const u8 hash_prefix_none[] = { }; 31 32 static const u8 hash_prefix_md5[] = { 33 0x30, 0x20, 0x30, 0x0c, 0x06, 0x08, /* SEQUENCE (SEQUENCE (OID */ 34 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x02, 0x05, /* <algorithm>, */ 35 0x05, 0x00, 0x04, 0x10 /* NULL), OCTET STRING <hash>) */ 36 }; 37 38 static const u8 hash_prefix_sha1[] = { 39 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 40 0x2b, 0x0e, 0x03, 0x02, 0x1a, 41 0x05, 0x00, 0x04, 0x14 42 }; 43 44 static const u8 hash_prefix_rmd160[] = { 45 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 46 0x2b, 0x24, 0x03, 0x02, 0x01, 47 0x05, 0x00, 0x04, 0x14 48 }; 49 50 static const u8 hash_prefix_sha224[] = { 51 0x30, 0x2d, 0x30, 0x0d, 0x06, 0x09, 52 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04, 53 0x05, 0x00, 0x04, 0x1c 54 }; 55 56 static const u8 hash_prefix_sha256[] = { 57 0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 58 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 59 0x05, 0x00, 0x04, 0x20 60 }; 61 62 static const u8 hash_prefix_sha384[] = { 63 0x30, 0x41, 0x30, 0x0d, 0x06, 0x09, 64 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02, 65 0x05, 0x00, 0x04, 0x30 66 }; 67 68 static const u8 hash_prefix_sha512[] = { 69 0x30, 0x51, 0x30, 0x0d, 0x06, 0x09, 70 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, 71 0x05, 0x00, 0x04, 0x40 72 }; 73 74 static const u8 hash_prefix_sha3_256[] = { 75 0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 76 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x08, 77 0x05, 0x00, 0x04, 0x20 78 }; 79 80 static const u8 hash_prefix_sha3_384[] = { 81 0x30, 0x41, 0x30, 0x0d, 0x06, 0x09, 82 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x09, 83 0x05, 0x00, 0x04, 0x30 84 }; 85 86 static const u8 hash_prefix_sha3_512[] = { 87 0x30, 0x51, 0x30, 0x0d, 0x06, 0x09, 88 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x0a, 89 0x05, 0x00, 0x04, 0x40 90 }; 91 92 static const struct hash_prefix { 93 const char *name; 94 const u8 *data; 95 size_t size; 96 } hash_prefixes[] = { 97 #define _(X) { #X, hash_prefix_##X, sizeof(hash_prefix_##X) } 98 _(none), 99 _(md5), 100 _(sha1), 101 _(rmd160), 102 _(sha256), 103 _(sha384), 104 _(sha512), 105 _(sha224), 106 #undef _ 107 #define _(X) { "sha3-" #X, hash_prefix_sha3_##X, sizeof(hash_prefix_sha3_##X) } 108 _(256), 109 _(384), 110 _(512), 111 #undef _ 112 { NULL } 113 }; 114 115 static const struct hash_prefix *rsassa_pkcs1_find_hash_prefix(const char *name) 116 { 117 const struct hash_prefix *p; 118 119 for (p = hash_prefixes; p->name; p++) 120 if (strcmp(name, p->name) == 0) 121 return p; 122 return NULL; 123 } 124 125 static bool rsassa_pkcs1_invalid_hash_len(unsigned int len, 126 const struct hash_prefix *p) 127 { 128 /* 129 * Legacy protocols such as TLS 1.1 or earlier and IKE version 1 130 * do not prepend a Full Hash Prefix to the hash. In that case, 131 * the size of the Full Hash Prefix is zero. 132 */ 133 if (p->data == hash_prefix_none) 134 return false; 135 136 /* 137 * The final byte of the Full Hash Prefix encodes the hash length. 138 * 139 * This needs to be revisited should hash algorithms with more than 140 * 1016 bits (127 bytes * 8) ever be added. The length would then 141 * be encoded into more than one byte by ASN.1. 142 */ 143 static_assert(HASH_MAX_DIGESTSIZE <= 127); 144 145 return len != p->data[p->size - 1]; 146 } 147 148 struct rsassa_pkcs1_ctx { 149 struct crypto_akcipher *child; 150 unsigned int key_size; 151 }; 152 153 struct rsassa_pkcs1_inst_ctx { 154 struct crypto_akcipher_spawn spawn; 155 const struct hash_prefix *hash_prefix; 156 }; 157 158 static int rsassa_pkcs1_sign(struct crypto_sig *tfm, 159 const void *src, unsigned int slen, 160 void *dst, unsigned int dlen) 161 { 162 struct sig_instance *inst = sig_alg_instance(tfm); 163 struct rsassa_pkcs1_inst_ctx *ictx = sig_instance_ctx(inst); 164 const struct hash_prefix *hash_prefix = ictx->hash_prefix; 165 struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm); 166 unsigned int pad_len; 167 unsigned int ps_end; 168 unsigned int len; 169 u8 *in_buf; 170 int err; 171 172 if (!ctx->key_size) 173 return -EINVAL; 174 175 if (dlen < ctx->key_size) 176 return -EOVERFLOW; 177 178 if (rsassa_pkcs1_invalid_hash_len(slen, hash_prefix)) 179 return -EINVAL; 180 181 if (slen + hash_prefix->size > ctx->key_size - 11) 182 return -EOVERFLOW; 183 184 pad_len = ctx->key_size - slen - hash_prefix->size - 1; 185 186 /* RFC 8017 sec 8.2.1 step 1 - EMSA-PKCS1-v1_5 encoding generation */ 187 in_buf = dst; 188 memmove(in_buf + pad_len + hash_prefix->size, src, slen); 189 memcpy(in_buf + pad_len, hash_prefix->data, hash_prefix->size); 190 191 ps_end = pad_len - 1; 192 in_buf[0] = 0x01; 193 memset(in_buf + 1, 0xff, ps_end - 1); 194 in_buf[ps_end] = 0x00; 195 196 197 /* RFC 8017 sec 8.2.1 step 2 - RSA signature */ 198 err = crypto_akcipher_sync_decrypt(ctx->child, in_buf, 199 ctx->key_size - 1, in_buf, 200 ctx->key_size); 201 if (err < 0) 202 return err; 203 204 len = err; 205 pad_len = ctx->key_size - len; 206 207 /* Four billion to one */ 208 if (unlikely(pad_len)) { 209 memmove(dst + pad_len, dst, len); 210 memset(dst, 0, pad_len); 211 } 212 213 return 0; 214 } 215 216 static int rsassa_pkcs1_verify(struct crypto_sig *tfm, 217 const void *src, unsigned int slen, 218 const void *digest, unsigned int dlen) 219 { 220 struct sig_instance *inst = sig_alg_instance(tfm); 221 struct rsassa_pkcs1_inst_ctx *ictx = sig_instance_ctx(inst); 222 const struct hash_prefix *hash_prefix = ictx->hash_prefix; 223 struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm); 224 unsigned int child_reqsize = crypto_akcipher_reqsize(ctx->child); 225 struct akcipher_request *child_req __free(kfree_sensitive) = NULL; 226 struct crypto_wait cwait; 227 struct scatterlist sg; 228 unsigned int dst_len; 229 unsigned int pos; 230 u8 *out_buf; 231 int err; 232 233 /* RFC 8017 sec 8.2.2 step 1 - length checking */ 234 if (!ctx->key_size || 235 slen != ctx->key_size || 236 rsassa_pkcs1_invalid_hash_len(dlen, hash_prefix)) 237 return -EINVAL; 238 239 /* RFC 8017 sec 8.2.2 step 2 - RSA verification */ 240 child_req = kmalloc(sizeof(*child_req) + child_reqsize + ctx->key_size, 241 GFP_KERNEL); 242 if (!child_req) 243 return -ENOMEM; 244 245 out_buf = (u8 *)(child_req + 1) + child_reqsize; 246 memcpy(out_buf, src, slen); 247 248 crypto_init_wait(&cwait); 249 sg_init_one(&sg, out_buf, slen); 250 akcipher_request_set_tfm(child_req, ctx->child); 251 akcipher_request_set_crypt(child_req, &sg, &sg, slen, slen); 252 akcipher_request_set_callback(child_req, CRYPTO_TFM_REQ_MAY_SLEEP, 253 crypto_req_done, &cwait); 254 255 err = crypto_akcipher_encrypt(child_req); 256 err = crypto_wait_req(err, &cwait); 257 if (err) 258 return err; 259 260 /* RFC 8017 sec 8.2.2 step 3 - EMSA-PKCS1-v1_5 encoding verification */ 261 dst_len = child_req->dst_len; 262 if (dst_len < ctx->key_size - 1) 263 return -EINVAL; 264 265 if (dst_len == ctx->key_size) { 266 if (out_buf[0] != 0x00) 267 /* Encrypted value had no leading 0 byte */ 268 return -EINVAL; 269 270 dst_len--; 271 out_buf++; 272 } 273 274 if (out_buf[0] != 0x01) 275 return -EBADMSG; 276 277 for (pos = 1; pos < dst_len; pos++) 278 if (out_buf[pos] != 0xff) 279 break; 280 281 if (pos < 9 || pos == dst_len || out_buf[pos] != 0x00) 282 return -EBADMSG; 283 pos++; 284 285 if (hash_prefix->size > dst_len - pos) 286 return -EBADMSG; 287 if (crypto_memneq(out_buf + pos, hash_prefix->data, hash_prefix->size)) 288 return -EBADMSG; 289 pos += hash_prefix->size; 290 291 /* RFC 8017 sec 8.2.2 step 4 - comparison of digest with out_buf */ 292 if (dlen != dst_len - pos) 293 return -EKEYREJECTED; 294 if (memcmp(digest, out_buf + pos, dlen) != 0) 295 return -EKEYREJECTED; 296 297 return 0; 298 } 299 300 static unsigned int rsassa_pkcs1_key_size(struct crypto_sig *tfm) 301 { 302 struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm); 303 304 return ctx->key_size; 305 } 306 307 static int rsassa_pkcs1_set_pub_key(struct crypto_sig *tfm, 308 const void *key, unsigned int keylen) 309 { 310 struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm); 311 312 return rsa_set_key(ctx->child, &ctx->key_size, RSA_PUB, key, keylen); 313 } 314 315 static int rsassa_pkcs1_set_priv_key(struct crypto_sig *tfm, 316 const void *key, unsigned int keylen) 317 { 318 struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm); 319 320 return rsa_set_key(ctx->child, &ctx->key_size, RSA_PRIV, key, keylen); 321 } 322 323 static int rsassa_pkcs1_init_tfm(struct crypto_sig *tfm) 324 { 325 struct sig_instance *inst = sig_alg_instance(tfm); 326 struct rsassa_pkcs1_inst_ctx *ictx = sig_instance_ctx(inst); 327 struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm); 328 struct crypto_akcipher *child_tfm; 329 330 child_tfm = crypto_spawn_akcipher(&ictx->spawn); 331 if (IS_ERR(child_tfm)) 332 return PTR_ERR(child_tfm); 333 334 ctx->child = child_tfm; 335 336 return 0; 337 } 338 339 static void rsassa_pkcs1_exit_tfm(struct crypto_sig *tfm) 340 { 341 struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm); 342 343 crypto_free_akcipher(ctx->child); 344 } 345 346 static void rsassa_pkcs1_free(struct sig_instance *inst) 347 { 348 struct rsassa_pkcs1_inst_ctx *ctx = sig_instance_ctx(inst); 349 struct crypto_akcipher_spawn *spawn = &ctx->spawn; 350 351 crypto_drop_akcipher(spawn); 352 kfree(inst); 353 } 354 355 static int rsassa_pkcs1_create(struct crypto_template *tmpl, struct rtattr **tb) 356 { 357 struct rsassa_pkcs1_inst_ctx *ctx; 358 struct akcipher_alg *rsa_alg; 359 struct sig_instance *inst; 360 const char *hash_name; 361 u32 mask; 362 int err; 363 364 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SIG, &mask); 365 if (err) 366 return err; 367 368 inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL); 369 if (!inst) 370 return -ENOMEM; 371 372 ctx = sig_instance_ctx(inst); 373 374 err = crypto_grab_akcipher(&ctx->spawn, sig_crypto_instance(inst), 375 crypto_attr_alg_name(tb[1]), 0, mask); 376 if (err) 377 goto err_free_inst; 378 379 rsa_alg = crypto_spawn_akcipher_alg(&ctx->spawn); 380 381 if (strcmp(rsa_alg->base.cra_name, "rsa") != 0) { 382 err = -EINVAL; 383 goto err_free_inst; 384 } 385 386 hash_name = crypto_attr_alg_name(tb[2]); 387 if (IS_ERR(hash_name)) { 388 err = PTR_ERR(hash_name); 389 goto err_free_inst; 390 } 391 392 ctx->hash_prefix = rsassa_pkcs1_find_hash_prefix(hash_name); 393 if (!ctx->hash_prefix) { 394 err = -EINVAL; 395 goto err_free_inst; 396 } 397 398 err = -ENAMETOOLONG; 399 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME, 400 "pkcs1(%s,%s)", rsa_alg->base.cra_name, 401 hash_name) >= CRYPTO_MAX_ALG_NAME) 402 goto err_free_inst; 403 404 if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME, 405 "pkcs1(%s,%s)", rsa_alg->base.cra_driver_name, 406 hash_name) >= CRYPTO_MAX_ALG_NAME) 407 goto err_free_inst; 408 409 inst->alg.base.cra_priority = rsa_alg->base.cra_priority; 410 inst->alg.base.cra_ctxsize = sizeof(struct rsassa_pkcs1_ctx); 411 412 inst->alg.init = rsassa_pkcs1_init_tfm; 413 inst->alg.exit = rsassa_pkcs1_exit_tfm; 414 415 inst->alg.sign = rsassa_pkcs1_sign; 416 inst->alg.verify = rsassa_pkcs1_verify; 417 inst->alg.key_size = rsassa_pkcs1_key_size; 418 inst->alg.set_pub_key = rsassa_pkcs1_set_pub_key; 419 inst->alg.set_priv_key = rsassa_pkcs1_set_priv_key; 420 421 inst->free = rsassa_pkcs1_free; 422 423 err = sig_register_instance(tmpl, inst); 424 if (err) { 425 err_free_inst: 426 rsassa_pkcs1_free(inst); 427 } 428 return err; 429 } 430 431 struct crypto_template rsassa_pkcs1_tmpl = { 432 .name = "pkcs1", 433 .create = rsassa_pkcs1_create, 434 .module = THIS_MODULE, 435 }; 436 437 MODULE_ALIAS_CRYPTO("pkcs1"); 438