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 ([email protected])
   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, "sha224") != 0 &&
 119                     strcmp(hash_algo, "sha256") != 0 &&
 120                     strcmp(hash_algo, "sha384") != 0 &&
 121                     strcmp(hash_algo, "sha512") != 0 &&
 122                     strcmp(hash_algo, "sha3-256") != 0 &&
 123                     strcmp(hash_algo, "sha3-384") != 0 &&
 124                     strcmp(hash_algo, "sha3-512") != 0)
 125                         return -EINVAL;
 126         } else if (strcmp(pkey->pkey_algo, "sm2") == 0) {
 127                 if (strcmp(encoding, "raw") != 0)
 128                         return -EINVAL;
 129                 if (!hash_algo)
 130                         return -EINVAL;
 131                 if (strcmp(hash_algo, "sm3") != 0)
 132                         return -EINVAL;
 133         } else if (strcmp(pkey->pkey_algo, "ecrdsa") == 0) {
 134                 if (strcmp(encoding, "raw") != 0)
 135                         return -EINVAL;
 136                 if (!hash_algo)
 137                         return -EINVAL;
 138                 if (strcmp(hash_algo, "streebog256") != 0 &&
 139                     strcmp(hash_algo, "streebog512") != 0)
 140                         return -EINVAL;
 141         } else {
 142                 /* Unknown public key algorithm */
 143                 return -ENOPKG;
 144         }
 145         if (strscpy(alg_name, pkey->pkey_algo, CRYPTO_MAX_ALG_NAME) < 0)
 146                 return -EINVAL;
 147         return 0;
 148 }
 149
 150 static u8 *pkey_pack_u32(u8 *dst, u32 val)
 151 {
 152         memcpy(dst, &val, sizeof(val));
 153         return dst + sizeof(val);
 154 }
 155
 156 /*
 157  * Query information about a key.
 158  */
 159 static int software_key_query(const struct kernel_pkey_params *params,
 160                               struct kernel_pkey_query *info)
 161 {
 162         struct crypto_akcipher *tfm;
 163         struct public_key *pkey = params->key->payload.data[asym_crypto];
 164         char alg_name[CRYPTO_MAX_ALG_NAME];
 165         struct crypto_sig *sig;
 166         u8 *key, *ptr;
 167         int ret, len;
 168         bool issig;
 169
 170         ret = software_key_determine_akcipher(pkey, params->encoding,
 171                                               params->hash_algo, alg_name,
 172                                               &issig, kernel_pkey_sign);
 173         if (ret < 0)
 174                 return ret;
 175
 176         key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
 177                       GFP_KERNEL);
 178         if (!key)
 179                 return -ENOMEM;
 180
 181         memcpy(key, pkey->key, pkey->keylen);
 182         ptr = key + pkey->keylen;
 183         ptr = pkey_pack_u32(ptr, pkey->algo);
 184         ptr = pkey_pack_u32(ptr, pkey->paramlen);
 185         memcpy(ptr, pkey->params, pkey->paramlen);
 186
 187         if (issig) {
 188                 sig = crypto_alloc_sig(alg_name, 0, 0);
 189                 if (IS_ERR(sig)) {
 190                         ret = PTR_ERR(sig);
 191                         goto error_free_key;
 192                 }
 193
 194                 if (pkey->key_is_private)
 195                         ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
 196                 else
 197                         ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
 198                 if (ret < 0)
 199                         goto error_free_tfm;
 200
 201                 len = crypto_sig_maxsize(sig);
 202
 203                 info->supported_ops = KEYCTL_SUPPORTS_VERIFY;
 204                 if (pkey->key_is_private)
 205                         info->supported_ops |= KEYCTL_SUPPORTS_SIGN;
 206
 207                 if (strcmp(params->encoding, "pkcs1") == 0) {
 208                         info->supported_ops |= KEYCTL_SUPPORTS_ENCRYPT;
 209                         if (pkey->key_is_private)
 210                                 info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
 211                 }
 212         } else {
 213                 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
 214                 if (IS_ERR(tfm)) {
 215                         ret = PTR_ERR(tfm);
 216                         goto error_free_key;
 217                 }
 218
 219                 if (pkey->key_is_private)
 220                         ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
 221                 else
 222                         ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
 223                 if (ret < 0)
 224                         goto error_free_tfm;
 225
 226                 len = crypto_akcipher_maxsize(tfm);
 227
 228                 info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT;
 229                 if (pkey->key_is_private)
 230                         info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
 231         }
 232
 233         info->key_size = len * 8;
 234
 235         if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
 236                 /*
 237                  * ECDSA key sizes are much smaller than RSA, and thus could
 238                  * operate on (hashed) inputs that are larger than key size.
 239                  * For example SHA384-hashed input used with secp256r1
 240                  * based keys.  Set max_data_size to be at least as large as
 241                  * the largest supported hash size (SHA512)
 242                  */
 243                 info->max_data_size = 64;
 244
 245                 /*
 246                  * Verify takes ECDSA-Sig (described in RFC 5480) as input,
 247                  * which is actually 2 'key_size'-bit integers encoded in
 248                  * ASN.1.  Account for the ASN.1 encoding overhead here.
 249                  */
 250                 info->max_sig_size = 2 * (len + 3) + 2;
 251         } else {
 252                 info->max_data_size = len;
 253                 info->max_sig_size = len;
 254         }
 255
 256         info->max_enc_size = len;
 257         info->max_dec_size = len;
 258
 259         ret = 0;
 260
 261 error_free_tfm:
 262         if (issig)
 263                 crypto_free_sig(sig);
 264         else
 265                 crypto_free_akcipher(tfm);
 266 error_free_key:
 267         kfree_sensitive(key);
 268         pr_devel("<==%s() = %d\n", __func__, ret);
 269         return ret;
 270 }
 271
 272 /*
 273  * Do encryption, decryption and signing ops.
 274  */
 275 static int software_key_eds_op(struct kernel_pkey_params *params,
 276                                const void *in, void *out)
 277 {
 278         const struct public_key *pkey = params->key->payload.data[asym_crypto];
 279         char alg_name[CRYPTO_MAX_ALG_NAME];
 280         struct crypto_akcipher *tfm;
 281         struct crypto_sig *sig;
 282         char *key, *ptr;
 283         bool issig;
 284         int ksz;
 285         int ret;
 286
 287         pr_devel("==>%s()\n", __func__);
 288
 289         ret = software_key_determine_akcipher(pkey, params->encoding,
 290                                               params->hash_algo, alg_name,
 291                                               &issig, params->op);
 292         if (ret < 0)
 293                 return ret;
 294
 295         key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
 296                       GFP_KERNEL);
 297         if (!key)
 298                 return -ENOMEM;
 299
 300         memcpy(key, pkey->key, pkey->keylen);
 301         ptr = key + pkey->keylen;
 302         ptr = pkey_pack_u32(ptr, pkey->algo);
 303         ptr = pkey_pack_u32(ptr, pkey->paramlen);
 304         memcpy(ptr, pkey->params, pkey->paramlen);
 305
 306         if (issig) {
 307                 sig = crypto_alloc_sig(alg_name, 0, 0);
 308                 if (IS_ERR(sig)) {
 309                         ret = PTR_ERR(sig);
 310                         goto error_free_key;
 311                 }
 312
 313                 if (pkey->key_is_private)
 314                         ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
 315                 else
 316                         ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
 317                 if (ret)
 318                         goto error_free_tfm;
 319
 320                 ksz = crypto_sig_maxsize(sig);
 321         } else {
 322                 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
 323                 if (IS_ERR(tfm)) {
 324                         ret = PTR_ERR(tfm);
 325                         goto error_free_key;
 326                 }
 327
 328                 if (pkey->key_is_private)
 329                         ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
 330                 else
 331                         ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
 332                 if (ret)
 333                         goto error_free_tfm;
 334
 335                 ksz = crypto_akcipher_maxsize(tfm);
 336         }
 337
 338         ret = -EINVAL;
 339
 340         /* Perform the encryption calculation. */
 341         switch (params->op) {
 342         case kernel_pkey_encrypt:
 343                 if (issig)
 344                         break;
 345                 ret = crypto_akcipher_sync_encrypt(tfm, in, params->in_len,
 346                                                    out, params->out_len);
 347                 break;
 348         case kernel_pkey_decrypt:
 349                 if (issig)
 350                         break;
 351                 ret = crypto_akcipher_sync_decrypt(tfm, in, params->in_len,
 352                                                    out, params->out_len);
 353                 break;
 354         case kernel_pkey_sign:
 355                 if (!issig)
 356                         break;
 357                 ret = crypto_sig_sign(sig, in, params->in_len,
 358                                       out, params->out_len);
 359                 break;
 360         default:
 361                 BUG();
 362         }
 363
 364         if (ret == 0)
 365                 ret = ksz;
 366
 367 error_free_tfm:
 368         if (issig)
 369                 crypto_free_sig(sig);
 370         else
 371                 crypto_free_akcipher(tfm);
 372 error_free_key:
 373         kfree_sensitive(key);
 374         pr_devel("<==%s() = %d\n", __func__, ret);
 375         return ret;
 376 }
 377
 378 /*
 379  * Verify a signature using a public key.
 380  */
 381 int public_key_verify_signature(const struct public_key *pkey,
 382                                 const struct public_key_signature *sig)
 383 {
 384         char alg_name[CRYPTO_MAX_ALG_NAME];
 385         struct crypto_sig *tfm;
 386         char *key, *ptr;
 387         bool issig;
 388         int ret;
 389
 390         pr_devel("==>%s()\n", __func__);
 391
 392         BUG_ON(!pkey);
 393         BUG_ON(!sig);
 394         BUG_ON(!sig->s);
 395
 396         /*
 397          * If the signature specifies a public key algorithm, it *must* match
 398          * the key's actual public key algorithm.
 399          *
 400          * Small exception: ECDSA signatures don't specify the curve, but ECDSA
 401          * keys do.  So the strings can mismatch slightly in that case:
 402          * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
 403          */
 404         if (sig->pkey_algo) {
 405                 if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
 406                     (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
 407                      strcmp(sig->pkey_algo, "ecdsa") != 0))
 408                         return -EKEYREJECTED;
 409         }
 410
 411         ret = software_key_determine_akcipher(pkey, sig->encoding,
 412                                               sig->hash_algo, alg_name,
 413                                               &issig, kernel_pkey_verify);
 414         if (ret < 0)
 415                 return ret;
 416
 417         tfm = crypto_alloc_sig(alg_name, 0, 0);
 418         if (IS_ERR(tfm))
 419                 return PTR_ERR(tfm);
 420
 421         key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
 422                       GFP_KERNEL);
 423         if (!key) {
 424                 ret = -ENOMEM;
 425                 goto error_free_tfm;
 426         }
 427
 428         memcpy(key, pkey->key, pkey->keylen);
 429         ptr = key + pkey->keylen;
 430         ptr = pkey_pack_u32(ptr, pkey->algo);
 431         ptr = pkey_pack_u32(ptr, pkey->paramlen);
 432         memcpy(ptr, pkey->params, pkey->paramlen);
 433
 434         if (pkey->key_is_private)
 435                 ret = crypto_sig_set_privkey(tfm, key, pkey->keylen);
 436         else
 437                 ret = crypto_sig_set_pubkey(tfm, key, pkey->keylen);
 438         if (ret)
 439                 goto error_free_key;
 440
 441         ret = crypto_sig_verify(tfm, sig->s, sig->s_size,
 442                                 sig->digest, sig->digest_size);
 443
 444 error_free_key:
 445         kfree_sensitive(key);
 446 error_free_tfm:
 447         crypto_free_sig(tfm);
 448         pr_devel("<==%s() = %d\n", __func__, ret);
 449         if (WARN_ON_ONCE(ret > 0))
 450                 ret = -EINVAL;
 451         return ret;
 452 }
 453 EXPORT_SYMBOL_GPL(public_key_verify_signature);
 454
 455 static int public_key_verify_signature_2(const struct key *key,
 456                                          const struct public_key_signature *sig)
 457 {
 458         const struct public_key *pk = key->payload.data[asym_crypto];
 459         return public_key_verify_signature(pk, sig);
 460 }
 461
 462 /*
 463  * Public key algorithm asymmetric key subtype
 464  */
 465 struct asymmetric_key_subtype public_key_subtype = {
 466         .owner                  = THIS_MODULE,
 467         .name                   = "public_key",
 468         .name_len               = sizeof("public_key") - 1,
 469         .describe               = public_key_describe,
 470         .destroy                = public_key_destroy,
 471         .query                  = software_key_query,
 472         .eds_op                 = software_key_eds_op,
 473         .verify_signature       = public_key_verify_signature_2,
 474 };
 475 EXPORT_SYMBOL_GPL(public_key_subtype);