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                         if (!hash_algo) {
  85                                 *sig = false;
  86                                 n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
  87                                              "pkcs1pad(%s)",
  88                                              pkey->pkey_algo);
  89                         } else {
  90                                 *sig = op == kernel_pkey_sign ||
  91                                        op == kernel_pkey_verify;
  92                                 n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
  93                                              "pkcs1pad(%s,%s)",
  94                                              pkey->pkey_algo, hash_algo);
  95                         }
  96                         return n >= CRYPTO_MAX_ALG_NAME ? -EINVAL : 0;
  97                 }
  98                 if (strcmp(encoding, "raw") != 0)
  99                         return -EINVAL;
 100                 /*
 101                  * Raw RSA cannot differentiate between different hash
 102                  * algorithms.
 103                  */
 104                 if (hash_algo)
 105                         return -EINVAL;
 106                 *sig = false;
 107         } else if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
 108                 if (strcmp(encoding, "x962") != 0)
 109                         return -EINVAL;
 110                 /*
 111                  * ECDSA signatures are taken over a raw hash, so they don't
 112                  * differentiate between different hash algorithms.  That means
 113                  * that the verifier should hard-code a specific hash algorithm.
 114                  * Unfortunately, in practice ECDSA is used with multiple SHAs,
 115                  * so we have to allow all of them and not just one.
 116                  */
 117                 if (!hash_algo)
 118                         return -EINVAL;
 119                 if (strcmp(hash_algo, "sha1") != 0 &&
 120                     strcmp(hash_algo, "sha224") != 0 &&
 121                     strcmp(hash_algo, "sha256") != 0 &&
 122                     strcmp(hash_algo, "sha384") != 0 &&
 123                     strcmp(hash_algo, "sha512") != 0)
 124                         return -EINVAL;
 125         } else if (strcmp(pkey->pkey_algo, "sm2") == 0) {
 126                 if (strcmp(encoding, "raw") != 0)
 127                         return -EINVAL;
 128                 if (!hash_algo)
 129                         return -EINVAL;
 130                 if (strcmp(hash_algo, "sm3") != 0)
 131                         return -EINVAL;
 132         } else if (strcmp(pkey->pkey_algo, "ecrdsa") == 0) {
 133                 if (strcmp(encoding, "raw") != 0)
 134                         return -EINVAL;
 135                 if (!hash_algo)
 136                         return -EINVAL;
 137                 if (strcmp(hash_algo, "streebog256") != 0 &&
 138                     strcmp(hash_algo, "streebog512") != 0)
 139                         return -EINVAL;
 140         } else {
 141                 /* Unknown public key algorithm */
 142                 return -ENOPKG;
 143         }
 144         if (strscpy(alg_name, pkey->pkey_algo, CRYPTO_MAX_ALG_NAME) < 0)
 145                 return -EINVAL;
 146         return 0;
 147 }
 148
 149 static u8 *pkey_pack_u32(u8 *dst, u32 val)
 150 {
 151         memcpy(dst, &val, sizeof(val));
 152         return dst + sizeof(val);
 153 }
 154
 155 /*
 156  * Query information about a key.
 157  */
 158 static int software_key_query(const struct kernel_pkey_params *params,
 159                               struct kernel_pkey_query *info)
 160 {
 161         struct crypto_akcipher *tfm;
 162         struct public_key *pkey = params->key->payload.data[asym_crypto];
 163         char alg_name[CRYPTO_MAX_ALG_NAME];
 164         struct crypto_sig *sig;
 165         u8 *key, *ptr;
 166         int ret, len;
 167         bool issig;
 168
 169         ret = software_key_determine_akcipher(pkey, params->encoding,
 170                                               params->hash_algo, alg_name,
 171                                               &issig, kernel_pkey_sign);
 172         if (ret < 0)
 173                 return ret;
 174
 175         key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
 176                       GFP_KERNEL);
 177         if (!key)
 178                 return -ENOMEM;
 179
 180         memcpy(key, pkey->key, pkey->keylen);
 181         ptr = key + pkey->keylen;
 182         ptr = pkey_pack_u32(ptr, pkey->algo);
 183         ptr = pkey_pack_u32(ptr, pkey->paramlen);
 184         memcpy(ptr, pkey->params, pkey->paramlen);
 185
 186         if (issig) {
 187                 sig = crypto_alloc_sig(alg_name, 0, 0);
 188                 if (IS_ERR(sig)) {
 189                         ret = PTR_ERR(sig);
 190                         goto error_free_key;
 191                 }
 192
 193                 if (pkey->key_is_private)
 194                         ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
 195                 else
 196                         ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
 197                 if (ret < 0)
 198                         goto error_free_tfm;
 199
 200                 len = crypto_sig_maxsize(sig);
 201
 202                 info->supported_ops = KEYCTL_SUPPORTS_VERIFY;
 203                 if (pkey->key_is_private)
 204                         info->supported_ops |= KEYCTL_SUPPORTS_SIGN;
 205
 206                 if (strcmp(params->encoding, "pkcs1") == 0) {
 207                         info->supported_ops |= KEYCTL_SUPPORTS_ENCRYPT;
 208                         if (pkey->key_is_private)
 209                                 info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
 210                 }
 211         } else {
 212                 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
 213                 if (IS_ERR(tfm)) {
 214                         ret = PTR_ERR(tfm);
 215                         goto error_free_key;
 216                 }
 217
 218                 if (pkey->key_is_private)
 219                         ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
 220                 else
 221                         ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
 222                 if (ret < 0)
 223                         goto error_free_tfm;
 224
 225                 len = crypto_akcipher_maxsize(tfm);
 226
 227                 info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT;
 228                 if (pkey->key_is_private)
 229                         info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
 230         }
 231
 232         info->key_size = len * 8;
 233
 234         if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
 235                 /*
 236                  * ECDSA key sizes are much smaller than RSA, and thus could
 237                  * operate on (hashed) inputs that are larger than key size.
 238                  * For example SHA384-hashed input used with secp256r1
 239                  * based keys.  Set max_data_size to be at least as large as
 240                  * the largest supported hash size (SHA512)
 241                  */
 242                 info->max_data_size = 64;
 243
 244                 /*
 245                  * Verify takes ECDSA-Sig (described in RFC 5480) as input,
 246                  * which is actually 2 'key_size'-bit integers encoded in
 247                  * ASN.1.  Account for the ASN.1 encoding overhead here.
 248                  */
 249                 info->max_sig_size = 2 * (len + 3) + 2;
 250         } else {
 251                 info->max_data_size = len;
 252                 info->max_sig_size = len;
 253         }
 254
 255         info->max_enc_size = len;
 256         info->max_dec_size = len;
 257
 258         ret = 0;
 259
 260 error_free_tfm:
 261         if (issig)
 262                 crypto_free_sig(sig);
 263         else
 264                 crypto_free_akcipher(tfm);
 265 error_free_key:
 266         kfree_sensitive(key);
 267         pr_devel("<==%s() = %d\n", __func__, ret);
 268         return ret;
 269 }
 270
 271 /*
 272  * Do encryption, decryption and signing ops.
 273  */
 274 static int software_key_eds_op(struct kernel_pkey_params *params,
 275                                const void *in, void *out)
 276 {
 277         const struct public_key *pkey = params->key->payload.data[asym_crypto];
 278         char alg_name[CRYPTO_MAX_ALG_NAME];
 279         struct crypto_akcipher *tfm;
 280         struct crypto_sig *sig;
 281         char *key, *ptr;
 282         bool issig;
 283         int ksz;
 284         int ret;
 285
 286         pr_devel("==>%s()\n", __func__);
 287
 288         ret = software_key_determine_akcipher(pkey, params->encoding,
 289                                               params->hash_algo, alg_name,
 290                                               &issig, params->op);
 291         if (ret < 0)
 292                 return ret;
 293
 294         key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
 295                       GFP_KERNEL);
 296         if (!key)
 297                 return -ENOMEM;
 298
 299         memcpy(key, pkey->key, pkey->keylen);
 300         ptr = key + pkey->keylen;
 301         ptr = pkey_pack_u32(ptr, pkey->algo);
 302         ptr = pkey_pack_u32(ptr, pkey->paramlen);
 303         memcpy(ptr, pkey->params, pkey->paramlen);
 304
 305         if (issig) {
 306                 sig = crypto_alloc_sig(alg_name, 0, 0);
 307                 if (IS_ERR(sig)) {
 308                         ret = PTR_ERR(sig);
 309                         goto error_free_key;
 310                 }
 311
 312                 if (pkey->key_is_private)
 313                         ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
 314                 else
 315                         ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
 316                 if (ret)
 317                         goto error_free_tfm;
 318
 319                 ksz = crypto_sig_maxsize(sig);
 320         } else {
 321                 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
 322                 if (IS_ERR(tfm)) {
 323                         ret = PTR_ERR(tfm);
 324                         goto error_free_key;
 325                 }
 326
 327                 if (pkey->key_is_private)
 328                         ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
 329                 else
 330                         ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
 331                 if (ret)
 332                         goto error_free_tfm;
 333
 334                 ksz = crypto_akcipher_maxsize(tfm);
 335         }
 336
 337         ret = -EINVAL;
 338
 339         /* Perform the encryption calculation. */
 340         switch (params->op) {
 341         case kernel_pkey_encrypt:
 342                 if (issig)
 343                         break;
 344                 ret = crypto_akcipher_sync_encrypt(tfm, in, params->in_len,
 345                                                    out, params->out_len);
 346                 break;
 347         case kernel_pkey_decrypt:
 348                 if (issig)
 349                         break;
 350                 ret = crypto_akcipher_sync_decrypt(tfm, in, params->in_len,
 351                                                    out, params->out_len);
 352                 break;
 353         case kernel_pkey_sign:
 354                 if (!issig)
 355                         break;
 356                 ret = crypto_sig_sign(sig, in, params->in_len,
 357                                       out, params->out_len);
 358                 break;
 359         default:
 360                 BUG();
 361         }
 362
 363         if (ret == 0)
 364                 ret = ksz;
 365
 366 error_free_tfm:
 367         if (issig)
 368                 crypto_free_sig(sig);
 369         else
 370                 crypto_free_akcipher(tfm);
 371 error_free_key:
 372         kfree_sensitive(key);
 373         pr_devel("<==%s() = %d\n", __func__, ret);
 374         return ret;
 375 }
 376
 377 /*
 378  * Verify a signature using a public key.
 379  */
 380 int public_key_verify_signature(const struct public_key *pkey,
 381                                 const struct public_key_signature *sig)
 382 {
 383         char alg_name[CRYPTO_MAX_ALG_NAME];
 384         struct crypto_sig *tfm;
 385         char *key, *ptr;
 386         bool issig;
 387         int ret;
 388
 389         pr_devel("==>%s()\n", __func__);
 390
 391         BUG_ON(!pkey);
 392         BUG_ON(!sig);
 393         BUG_ON(!sig->s);
 394
 395         /*
 396          * If the signature specifies a public key algorithm, it *must* match
 397          * the key's actual public key algorithm.
 398          *
 399          * Small exception: ECDSA signatures don't specify the curve, but ECDSA
 400          * keys do.  So the strings can mismatch slightly in that case:
 401          * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
 402          */
 403         if (sig->pkey_algo) {
 404                 if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
 405                     (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
 406                      strcmp(sig->pkey_algo, "ecdsa") != 0))
 407                         return -EKEYREJECTED;
 408         }
 409
 410         ret = software_key_determine_akcipher(pkey, sig->encoding,
 411                                               sig->hash_algo, alg_name,
 412                                               &issig, kernel_pkey_verify);
 413         if (ret < 0)
 414                 return ret;
 415
 416         tfm = crypto_alloc_sig(alg_name, 0, 0);
 417         if (IS_ERR(tfm))
 418                 return PTR_ERR(tfm);
 419
 420         key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
 421                       GFP_KERNEL);
 422         if (!key) {
 423                 ret = -ENOMEM;
 424                 goto error_free_tfm;
 425         }
 426
 427         memcpy(key, pkey->key, pkey->keylen);
 428         ptr = key + pkey->keylen;
 429         ptr = pkey_pack_u32(ptr, pkey->algo);
 430         ptr = pkey_pack_u32(ptr, pkey->paramlen);
 431         memcpy(ptr, pkey->params, pkey->paramlen);
 432
 433         if (pkey->key_is_private)
 434                 ret = crypto_sig_set_privkey(tfm, key, pkey->keylen);
 435         else
 436                 ret = crypto_sig_set_pubkey(tfm, key, pkey->keylen);
 437         if (ret)
 438                 goto error_free_key;
 439
 440         ret = crypto_sig_verify(tfm, sig->s, sig->s_size,
 441                                 sig->digest, sig->digest_size);
 442
 443 error_free_key:
 444         kfree_sensitive(key);
 445 error_free_tfm:
 446         crypto_free_sig(tfm);
 447         pr_devel("<==%s() = %d\n", __func__, ret);
 448         if (WARN_ON_ONCE(ret > 0))
 449                 ret = -EINVAL;
 450         return ret;
 451 }
 452 EXPORT_SYMBOL_GPL(public_key_verify_signature);
 453
 454 static int public_key_verify_signature_2(const struct key *key,
 455                                          const struct public_key_signature *sig)
 456 {
 457         const struct public_key *pk = key->payload.data[asym_crypto];
 458         return public_key_verify_signature(pk, sig);
 459 }
 460
 461 /*
 462  * Public key algorithm asymmetric key subtype
 463  */
 464 struct asymmetric_key_subtype public_key_subtype = {
 465         .owner                  = THIS_MODULE,
 466         .name                   = "public_key",
 467         .name_len               = sizeof("public_key") - 1,
 468         .describe               = public_key_describe,
 469         .destroy                = public_key_destroy,
 470         .query                  = software_key_query,
 471         .eds_op                 = software_key_eds_op,
 472         .verify_signature       = public_key_verify_signature_2,
 473 };
 474 EXPORT_SYMBOL_GPL(public_key_subtype);