crypto/asymmetric_keys/public_key.c

   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                         return -EINVAL;
 124         } else if (strcmp(pkey->pkey_algo, "sm2") == 0) {
 125                 if (strcmp(encoding, "raw") != 0)
 126                         return -EINVAL;
 127                 if (!hash_algo)
 128                         return -EINVAL;
 129                 if (strcmp(hash_algo, "sm3") != 0)
 130                         return -EINVAL;
 131         } else if (strcmp(pkey->pkey_algo, "ecrdsa") == 0) {
 132                 if (strcmp(encoding, "raw") != 0)
 133                         return -EINVAL;
 134                 if (!hash_algo)
 135                         return -EINVAL;
 136                 if (strcmp(hash_algo, "streebog256") != 0 &&
 137                     strcmp(hash_algo, "streebog512") != 0)
 138                         return -EINVAL;
 139         } else {
 140                 /* Unknown public key algorithm */
 141                 return -ENOPKG;
 142         }
 143         if (strscpy(alg_name, pkey->pkey_algo, CRYPTO_MAX_ALG_NAME) < 0)
 144                 return -EINVAL;
 145         return 0;
 146 }
 147
 148 static u8 *pkey_pack_u32(u8 *dst, u32 val)
 149 {
 150         memcpy(dst, &val, sizeof(val));
 151         return dst + sizeof(val);
 152 }
 153
 154 /*
 155  * Query information about a key.
 156  */
 157 static int software_key_query(const struct kernel_pkey_params *params,
 158                               struct kernel_pkey_query *info)
 159 {
 160         struct crypto_akcipher *tfm;
 161         struct public_key *pkey = params->key->payload.data[asym_crypto];
 162         char alg_name[CRYPTO_MAX_ALG_NAME];
 163         struct crypto_sig *sig;
 164         u8 *key, *ptr;
 165         int ret, len;
 166         bool issig;
 167
 168         ret = software_key_determine_akcipher(pkey, params->encoding,
 169                                               params->hash_algo, alg_name,
 170                                               &issig, kernel_pkey_sign);
 171         if (ret < 0)
 172                 return ret;
 173
 174         key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
 175                       GFP_KERNEL);
 176         if (!key)
 177                 return -ENOMEM;
 178
 179         memcpy(key, pkey->key, pkey->keylen);
 180         ptr = key + pkey->keylen;
 181         ptr = pkey_pack_u32(ptr, pkey->algo);
 182         ptr = pkey_pack_u32(ptr, pkey->paramlen);
 183         memcpy(ptr, pkey->params, pkey->paramlen);
 184
 185         if (issig) {
 186                 sig = crypto_alloc_sig(alg_name, 0, 0);
 187                 if (IS_ERR(sig)) {
 188                         ret = PTR_ERR(sig);
 189                         goto error_free_key;
 190                 }
 191
 192                 if (pkey->key_is_private)
 193                         ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
 194                 else
 195                         ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
 196                 if (ret < 0)
 197                         goto error_free_tfm;
 198
 199                 len = crypto_sig_maxsize(sig);
 200
 201                 info->supported_ops = KEYCTL_SUPPORTS_VERIFY;
 202                 if (pkey->key_is_private)
 203                         info->supported_ops |= KEYCTL_SUPPORTS_SIGN;
 204
 205                 if (strcmp(params->encoding, "pkcs1") == 0) {
 206                         info->supported_ops |= KEYCTL_SUPPORTS_ENCRYPT;
 207                         if (pkey->key_is_private)
 208                                 info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
 209                 }
 210         } else {
 211                 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
 212                 if (IS_ERR(tfm)) {
 213                         ret = PTR_ERR(tfm);
 214                         goto error_free_key;
 215                 }
 216
 217                 if (pkey->key_is_private)
 218                         ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
 219                 else
 220                         ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
 221                 if (ret < 0)
 222                         goto error_free_tfm;
 223
 224                 len = crypto_akcipher_maxsize(tfm);
 225
 226                 info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT;
 227                 if (pkey->key_is_private)
 228                         info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
 229         }
 230
 231         info->key_size = len * 8;
 232
 233         if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
 234                 /*
 235                  * ECDSA key sizes are much smaller than RSA, and thus could
 236                  * operate on (hashed) inputs that are larger than key size.
 237                  * For example SHA384-hashed input used with secp256r1
 238                  * based keys.  Set max_data_size to be at least as large as
 239                  * the largest supported hash size (SHA512)
 240                  */
 241                 info->max_data_size = 64;
 242
 243                 /*
 244                  * Verify takes ECDSA-Sig (described in RFC 5480) as input,
 245                  * which is actually 2 'key_size'-bit integers encoded in
 246                  * ASN.1.  Account for the ASN.1 encoding overhead here.
 247                  */
 248                 info->max_sig_size = 2 * (len + 3) + 2;
 249         } else {
 250                 info->max_data_size = len;
 251                 info->max_sig_size = len;
 252         }
 253
 254         info->max_enc_size = len;
 255         info->max_dec_size = len;
 256
 257         ret = 0;
 258
 259 error_free_tfm:
 260         if (issig)
 261                 crypto_free_sig(sig);
 262         else
 263                 crypto_free_akcipher(tfm);
 264 error_free_key:
 265         kfree_sensitive(key);
 266         pr_devel("<==%s() = %d\n", __func__, ret);
 267         return ret;
 268 }
 269
 270 /*
 271  * Do encryption, decryption and signing ops.
 272  */
 273 static int software_key_eds_op(struct kernel_pkey_params *params,
 274                                const void *in, void *out)
 275 {
 276         const struct public_key *pkey = params->key->payload.data[asym_crypto];
 277         char alg_name[CRYPTO_MAX_ALG_NAME];
 278         struct crypto_akcipher *tfm;
 279         struct crypto_sig *sig;
 280         char *key, *ptr;
 281         bool issig;
 282         int ksz;
 283         int ret;
 284
 285         pr_devel("==>%s()\n", __func__);
 286
 287         ret = software_key_determine_akcipher(pkey, params->encoding,
 288                                               params->hash_algo, alg_name,
 289                                               &issig, params->op);
 290         if (ret < 0)
 291                 return ret;
 292
 293         key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
 294                       GFP_KERNEL);
 295         if (!key)
 296                 return -ENOMEM;
 297
 298         memcpy(key, pkey->key, pkey->keylen);
 299         ptr = key + pkey->keylen;
 300         ptr = pkey_pack_u32(ptr, pkey->algo);
 301         ptr = pkey_pack_u32(ptr, pkey->paramlen);
 302         memcpy(ptr, pkey->params, pkey->paramlen);
 303
 304         if (issig) {
 305                 sig = crypto_alloc_sig(alg_name, 0, 0);
 306                 if (IS_ERR(sig)) {
 307                         ret = PTR_ERR(sig);
 308                         goto error_free_key;
 309                 }
 310
 311                 if (pkey->key_is_private)
 312                         ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
 313                 else
 314                         ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
 315                 if (ret)
 316                         goto error_free_tfm;
 317
 318                 ksz = crypto_sig_maxsize(sig);
 319         } else {
 320                 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
 321                 if (IS_ERR(tfm)) {
 322                         ret = PTR_ERR(tfm);
 323                         goto error_free_key;
 324                 }
 325
 326                 if (pkey->key_is_private)
 327                         ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
 328                 else
 329                         ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
 330                 if (ret)
 331                         goto error_free_tfm;
 332
 333                 ksz = crypto_akcipher_maxsize(tfm);
 334         }
 335
 336         ret = -EINVAL;
 337
 338         /* Perform the encryption calculation. */
 339         switch (params->op) {
 340         case kernel_pkey_encrypt:
 341                 if (issig)
 342                         break;
 343                 ret = crypto_akcipher_sync_encrypt(tfm, in, params->in_len,
 344                                                    out, params->out_len);
 345                 break;
 346         case kernel_pkey_decrypt:
 347                 if (issig)
 348                         break;
 349                 ret = crypto_akcipher_sync_decrypt(tfm, in, params->in_len,
 350                                                    out, params->out_len);
 351                 break;
 352         case kernel_pkey_sign:
 353                 if (!issig)
 354                         break;
 355                 ret = crypto_sig_sign(sig, in, params->in_len,
 356                                       out, params->out_len);
 357                 break;
 358         default:
 359                 BUG();
 360         }
 361
 362         if (ret == 0)
 363                 ret = ksz;
 364
 365 error_free_tfm:
 366         if (issig)
 367                 crypto_free_sig(sig);
 368         else
 369                 crypto_free_akcipher(tfm);
 370 error_free_key:
 371         kfree_sensitive(key);
 372         pr_devel("<==%s() = %d\n", __func__, ret);
 373         return ret;
 374 }
 375
 376 /*
 377  * Verify a signature using a public key.
 378  */
 379 int public_key_verify_signature(const struct public_key *pkey,
 380                                 const struct public_key_signature *sig)
 381 {
 382         char alg_name[CRYPTO_MAX_ALG_NAME];
 383         struct crypto_sig *tfm;
 384         char *key, *ptr;
 385         bool issig;
 386         int ret;
 387
 388         pr_devel("==>%s()\n", __func__);
 389
 390         BUG_ON(!pkey);
 391         BUG_ON(!sig);
 392         BUG_ON(!sig->s);
 393
 394         /*
 395          * If the signature specifies a public key algorithm, it *must* match
 396          * the key's actual public key algorithm.
 397          *
 398          * Small exception: ECDSA signatures don't specify the curve, but ECDSA
 399          * keys do.  So the strings can mismatch slightly in that case:
 400          * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
 401          */
 402         if (sig->pkey_algo) {
 403                 if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
 404                     (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
 405                      strcmp(sig->pkey_algo, "ecdsa") != 0))
 406                         return -EKEYREJECTED;
 407         }
 408
 409         ret = software_key_determine_akcipher(pkey, sig->encoding,
 410                                               sig->hash_algo, alg_name,
 411                                               &issig, kernel_pkey_verify);
 412         if (ret < 0)
 413                 return ret;
 414
 415         tfm = crypto_alloc_sig(alg_name, 0, 0);
 416         if (IS_ERR(tfm))
 417                 return PTR_ERR(tfm);
 418
 419         key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
 420                       GFP_KERNEL);
 421         if (!key) {
 422                 ret = -ENOMEM;
 423                 goto error_free_tfm;
 424         }
 425
 426         memcpy(key, pkey->key, pkey->keylen);
 427         ptr = key + pkey->keylen;
 428         ptr = pkey_pack_u32(ptr, pkey->algo);
 429         ptr = pkey_pack_u32(ptr, pkey->paramlen);
 430         memcpy(ptr, pkey->params, pkey->paramlen);
 431
 432         if (pkey->key_is_private)
 433                 ret = crypto_sig_set_privkey(tfm, key, pkey->keylen);
 434         else
 435                 ret = crypto_sig_set_pubkey(tfm, key, pkey->keylen);
 436         if (ret)
 437                 goto error_free_key;
 438
 439         ret = crypto_sig_verify(tfm, sig->s, sig->s_size,
 440                                 sig->digest, sig->digest_size);
 441
 442 error_free_key:
 443         kfree_sensitive(key);
 444 error_free_tfm:
 445         crypto_free_sig(tfm);
 446         pr_devel("<==%s() = %d\n", __func__, ret);
 447         if (WARN_ON_ONCE(ret > 0))
 448                 ret = -EINVAL;
 449         return ret;
 450 }
 451 EXPORT_SYMBOL_GPL(public_key_verify_signature);
 452
 453 static int public_key_verify_signature_2(const struct key *key,
 454                                          const struct public_key_signature *sig)
 455 {
 456         const struct public_key *pk = key->payload.data[asym_crypto];
 457         return public_key_verify_signature(pk, sig);
 458 }
 459
 460 /*
 461  * Public key algorithm asymmetric key subtype
 462  */
 463 struct asymmetric_key_subtype public_key_subtype = {
 464         .owner                  = THIS_MODULE,
 465         .name                   = "public_key",
 466         .name_len               = sizeof("public_key") - 1,
 467         .describe               = public_key_describe,
 468         .destroy                = public_key_destroy,
 469         .query                  = software_key_query,
 470         .eds_op                 = software_key_eds_op,
 471         .verify_signature       = public_key_verify_signature_2,
 472 };
 473 EXPORT_SYMBOL_GPL(public_key_subtype);