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                     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                 /*
 238                  * ECDSA key sizes are much smaller than RSA, and thus could
 239                  * operate on (hashed) inputs that are larger than key size.
 240                  * For example SHA384-hashed input used with secp256r1
 241                  * based keys.  Set max_data_size to be at least as large as
 242                  * the largest supported hash size (SHA512)
 243                  */
 244                 info->max_data_size = 64;
 245
 246                 /*
 247                  * Verify takes ECDSA-Sig (described in RFC 5480) as input,
 248                  * which is actually 2 'key_size'-bit integers encoded in
 249                  * ASN.1.  Account for the ASN.1 encoding overhead here.
 250                  */
 251                 info->max_sig_size = 2 * (len + 3) + 2;
 252         } else {
 253                 info->max_data_size = len;
 254                 info->max_sig_size = len;
 255         }
 256
 257         info->max_enc_size = len;
 258         info->max_dec_size = len;
 259
 260         ret = 0;
 261
 262 error_free_tfm:
 263         if (issig)
 264                 crypto_free_sig(sig);
 265         else
 266                 crypto_free_akcipher(tfm);
 267 error_free_key:
 268         kfree_sensitive(key);
 269         pr_devel("<==%s() = %d\n", __func__, ret);
 270         return ret;
 271 }
 272
 273 /*
 274  * Do encryption, decryption and signing ops.
 275  */
 276 static int software_key_eds_op(struct kernel_pkey_params *params,
 277                                const void *in, void *out)
 278 {
 279         const struct public_key *pkey = params->key->payload.data[asym_crypto];
 280         char alg_name[CRYPTO_MAX_ALG_NAME];
 281         struct crypto_akcipher *tfm;
 282         struct crypto_sig *sig;
 283         char *key, *ptr;
 284         bool issig;
 285         int ksz;
 286         int ret;
 287
 288         pr_devel("==>%s()\n", __func__);
 289
 290         ret = software_key_determine_akcipher(pkey, params->encoding,
 291                                               params->hash_algo, alg_name,
 292                                               &issig, params->op);
 293         if (ret < 0)
 294                 return ret;
 295
 296         key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
 297                       GFP_KERNEL);
 298         if (!key)
 299                 return -ENOMEM;
 300
 301         memcpy(key, pkey->key, pkey->keylen);
 302         ptr = key + pkey->keylen;
 303         ptr = pkey_pack_u32(ptr, pkey->algo);
 304         ptr = pkey_pack_u32(ptr, pkey->paramlen);
 305         memcpy(ptr, pkey->params, pkey->paramlen);
 306
 307         if (issig) {
 308                 sig = crypto_alloc_sig(alg_name, 0, 0);
 309                 if (IS_ERR(sig)) {
 310                         ret = PTR_ERR(sig);
 311                         goto error_free_key;
 312                 }
 313
 314                 if (pkey->key_is_private)
 315                         ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
 316                 else
 317                         ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
 318                 if (ret)
 319                         goto error_free_tfm;
 320
 321                 ksz = crypto_sig_maxsize(sig);
 322         } else {
 323                 tfm = crypto_alloc_akcipher(alg_name, 0, 0);
 324                 if (IS_ERR(tfm)) {
 325                         ret = PTR_ERR(tfm);
 326                         goto error_free_key;
 327                 }
 328
 329                 if (pkey->key_is_private)
 330                         ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
 331                 else
 332                         ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
 333                 if (ret)
 334                         goto error_free_tfm;
 335
 336                 ksz = crypto_akcipher_maxsize(tfm);
 337         }
 338
 339         ret = -EINVAL;
 340
 341         /* Perform the encryption calculation. */
 342         switch (params->op) {
 343         case kernel_pkey_encrypt:
 344                 if (issig)
 345                         break;
 346                 ret = crypto_akcipher_sync_encrypt(tfm, in, params->in_len,
 347                                                    out, params->out_len);
 348                 break;
 349         case kernel_pkey_decrypt:
 350                 if (issig)
 351                         break;
 352                 ret = crypto_akcipher_sync_decrypt(tfm, in, params->in_len,
 353                                                    out, params->out_len);
 354                 break;
 355         case kernel_pkey_sign:
 356                 if (!issig)
 357                         break;
 358                 ret = crypto_sig_sign(sig, in, params->in_len,
 359                                       out, params->out_len);
 360                 break;
 361         default:
 362                 BUG();
 363         }
 364
 365         if (ret == 0)
 366                 ret = ksz;
 367
 368 error_free_tfm:
 369         if (issig)
 370                 crypto_free_sig(sig);
 371         else
 372                 crypto_free_akcipher(tfm);
 373 error_free_key:
 374         kfree_sensitive(key);
 375         pr_devel("<==%s() = %d\n", __func__, ret);
 376         return ret;
 377 }
 378
 379 /*
 380  * Verify a signature using a public key.
 381  */
 382 int public_key_verify_signature(const struct public_key *pkey,
 383                                 const struct public_key_signature *sig)
 384 {
 385         char alg_name[CRYPTO_MAX_ALG_NAME];
 386         struct crypto_sig *tfm;
 387         char *key, *ptr;
 388         bool issig;
 389         int ret;
 390
 391         pr_devel("==>%s()\n", __func__);
 392
 393         BUG_ON(!pkey);
 394         BUG_ON(!sig);
 395         BUG_ON(!sig->s);
 396
 397         /*
 398          * If the signature specifies a public key algorithm, it *must* match
 399          * the key's actual public key algorithm.
 400          *
 401          * Small exception: ECDSA signatures don't specify the curve, but ECDSA
 402          * keys do.  So the strings can mismatch slightly in that case:
 403          * "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
 404          */
 405         if (sig->pkey_algo) {
 406                 if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
 407                     (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
 408                      strcmp(sig->pkey_algo, "ecdsa") != 0))
 409                         return -EKEYREJECTED;
 410         }
 411
 412         ret = software_key_determine_akcipher(pkey, sig->encoding,
 413                                               sig->hash_algo, alg_name,
 414                                               &issig, kernel_pkey_verify);
 415         if (ret < 0)
 416                 return ret;
 417
 418         tfm = crypto_alloc_sig(alg_name, 0, 0);
 419         if (IS_ERR(tfm))
 420                 return PTR_ERR(tfm);
 421
 422         key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
 423                       GFP_KERNEL);
 424         if (!key) {
 425                 ret = -ENOMEM;
 426                 goto error_free_tfm;
 427         }
 428
 429         memcpy(key, pkey->key, pkey->keylen);
 430         ptr = key + pkey->keylen;
 431         ptr = pkey_pack_u32(ptr, pkey->algo);
 432         ptr = pkey_pack_u32(ptr, pkey->paramlen);
 433         memcpy(ptr, pkey->params, pkey->paramlen);
 434
 435         if (pkey->key_is_private)
 436                 ret = crypto_sig_set_privkey(tfm, key, pkey->keylen);
 437         else
 438                 ret = crypto_sig_set_pubkey(tfm, key, pkey->keylen);
 439         if (ret)
 440                 goto error_free_key;
 441
 442         ret = crypto_sig_verify(tfm, sig->s, sig->s_size,
 443                                 sig->digest, sig->digest_size);
 444
 445 error_free_key:
 446         kfree_sensitive(key);
 447 error_free_tfm:
 448         crypto_free_sig(tfm);
 449         pr_devel("<==%s() = %d\n", __func__, ret);
 450         if (WARN_ON_ONCE(ret > 0))
 451                 ret = -EINVAL;
 452         return ret;
 453 }
 454 EXPORT_SYMBOL_GPL(public_key_verify_signature);
 455
 456 static int public_key_verify_signature_2(const struct key *key,
 457                                          const struct public_key_signature *sig)
 458 {
 459         const struct public_key *pk = key->payload.data[asym_crypto];
 460         return public_key_verify_signature(pk, sig);
 461 }
 462
 463 /*
 464  * Public key algorithm asymmetric key subtype
 465  */
 466 struct asymmetric_key_subtype public_key_subtype = {
 467         .owner                  = THIS_MODULE,
 468         .name                   = "public_key",
 469         .name_len               = sizeof("public_key") - 1,
 470         .describe               = public_key_describe,
 471         .destroy                = public_key_destroy,
 472         .query                  = software_key_query,
 473         .eds_op                 = software_key_eds_op,
 474         .verify_signature       = public_key_verify_signature_2,
 475 };
 476 EXPORT_SYMBOL_GPL(public_key_subtype);