crypto/asymmetric_keys/restrict.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* Instantiate a public key crypto key from an X.509 Certificate
   3  *
   4  * Copyright (C) 2012, 2016 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #define pr_fmt(fmt) "ASYM: "fmt
   9 #include <linux/module.h>
  10 #include <linux/kernel.h>
  11 #include <linux/err.h>
  12 #include <crypto/public_key.h>
  13 #include "asymmetric_keys.h"
  14
  15 static bool use_builtin_keys;
  16 static struct asymmetric_key_id *ca_keyid;
  17
  18 #ifndef MODULE
  19 static struct {
  20         struct asymmetric_key_id id;
  21         unsigned char data[10];
  22 } cakey;
  23
  24 static int __init ca_keys_setup(char *str)
  25 {
  26         if (!str)               /* default system keyring */
  27                 return 1;
  28
  29         if (strncmp(str, "id:", 3) == 0) {
  30                 struct asymmetric_key_id *p = &cakey.id;
  31                 size_t hexlen = (strlen(str) - 3) / 2;
  32                 int ret;
  33
  34                 if (hexlen == 0 || hexlen > sizeof(cakey.data)) {
  35                         pr_err("Missing or invalid ca_keys id\n");
  36                         return 1;
  37                 }
  38
  39                 ret = __asymmetric_key_hex_to_key_id(str + 3, p, hexlen);
  40                 if (ret < 0)
  41                         pr_err("Unparsable ca_keys id hex string\n");
  42                 else
  43                         ca_keyid = p;   /* owner key 'id:xxxxxx' */
  44         } else if (strcmp(str, "builtin") == 0) {
  45                 use_builtin_keys = true;
  46         }
  47
  48         return 1;
  49 }
  50 __setup("ca_keys=", ca_keys_setup);
  51 #endif
  52
  53 /**
  54  * restrict_link_by_signature - Restrict additions to a ring of public keys
  55  * @dest_keyring: Keyring being linked to.
  56  * @type: The type of key being added.
  57  * @payload: The payload of the new key.
  58  * @trust_keyring: A ring of keys that can be used to vouch for the new cert.
  59  *
  60  * Check the new certificate against the ones in the trust keyring.  If one of
  61  * those is the signing key and validates the new certificate, then mark the
  62  * new certificate as being trusted.
  63  *
  64  * Returns 0 if the new certificate was accepted, -ENOKEY if we couldn't find a
  65  * matching parent certificate in the trusted list, -EKEYREJECTED if the
  66  * signature check fails or the key is blacklisted, -ENOPKG if the signature
  67  * uses unsupported crypto, or some other error if there is a matching
  68  * certificate but the signature check cannot be performed.
  69  */
  70 int restrict_link_by_signature(struct key *dest_keyring,
  71                                const struct key_type *type,
  72                                const union key_payload *payload,
  73                                struct key *trust_keyring)
  74 {
  75         const struct public_key_signature *sig;
  76         struct key *key;
  77         int ret;
  78
  79         pr_devel("==>%s()\n", __func__);
  80
  81         if (!trust_keyring)
  82                 return -ENOKEY;
  83
  84         if (type != &key_type_asymmetric)
  85                 return -EOPNOTSUPP;
  86
  87         sig = payload->data[asym_auth];
  88         if (!sig)
  89                 return -ENOPKG;
  90         if (!sig->auth_ids[0] && !sig->auth_ids[1] && !sig->auth_ids[2])
  91                 return -ENOKEY;
  92
  93         if (ca_keyid && !asymmetric_key_id_partial(sig->auth_ids[1], ca_keyid))
  94                 return -EPERM;
  95
  96         /* See if we have a key that signed this one. */
  97         key = find_asymmetric_key(trust_keyring,
  98                                   sig->auth_ids[0], sig->auth_ids[1],
  99                                   sig->auth_ids[2], false);
 100         if (IS_ERR(key))
 101                 return -ENOKEY;
 102
 103         if (use_builtin_keys && !test_bit(KEY_FLAG_BUILTIN, &key->flags))
 104                 ret = -ENOKEY;
 105         else if (IS_BUILTIN(CONFIG_SECONDARY_TRUSTED_KEYRING_SIGNED_BY_BUILTIN) &&
 106                  !strcmp(dest_keyring->description, ".secondary_trusted_keys") &&
 107                  !test_bit(KEY_FLAG_BUILTIN, &key->flags))
 108                 ret = -ENOKEY;
 109         else
 110                 ret = verify_signature(key, sig);
 111         key_put(key);
 112         return ret;
 113 }
 114
 115 /**
 116  * restrict_link_by_ca - Restrict additions to a ring of CA keys
 117  * @dest_keyring: Keyring being linked to.
 118  * @type: The type of key being added.
 119  * @payload: The payload of the new key.
 120  * @trust_keyring: Unused.
 121  *
 122  * Check if the new certificate is a CA. If it is a CA, then mark the new
 123  * certificate as being ok to link.
 124  *
 125  * Returns 0 if the new certificate was accepted, -ENOKEY if the
 126  * certificate is not a CA. -ENOPKG if the signature uses unsupported
 127  * crypto, or some other error if there is a matching certificate but
 128  * the signature check cannot be performed.
 129  */
 130 int restrict_link_by_ca(struct key *dest_keyring,
 131                         const struct key_type *type,
 132                         const union key_payload *payload,
 133                         struct key *trust_keyring)
 134 {
 135         const struct public_key *pkey;
 136
 137         if (type != &key_type_asymmetric)
 138                 return -EOPNOTSUPP;
 139
 140         pkey = payload->data[asym_crypto];
 141         if (!pkey)
 142                 return -ENOPKG;
 143         if (!test_bit(KEY_EFLAG_CA, &pkey->key_eflags))
 144                 return -ENOKEY;
 145         if (!test_bit(KEY_EFLAG_KEYCERTSIGN, &pkey->key_eflags))
 146                 return -ENOKEY;
 147         if (!IS_ENABLED(CONFIG_INTEGRITY_CA_MACHINE_KEYRING_MAX))
 148                 return 0;
 149         if (test_bit(KEY_EFLAG_DIGITALSIG, &pkey->key_eflags))
 150                 return -ENOKEY;
 151
 152         return 0;
 153 }
 154
 155 /**
 156  * restrict_link_by_digsig - Restrict additions to a ring of digsig keys
 157  * @dest_keyring: Keyring being linked to.
 158  * @type: The type of key being added.
 159  * @payload: The payload of the new key.
 160  * @trust_keyring: A ring of keys that can be used to vouch for the new cert.
 161  *
 162  * Check if the new certificate has digitalSignature usage set. If it is,
 163  * then mark the new certificate as being ok to link. Afterwards verify
 164  * the new certificate against the ones in the trust_keyring.
 165  *
 166  * Returns 0 if the new certificate was accepted, -ENOKEY if the
 167  * certificate is not a digsig. -ENOPKG if the signature uses unsupported
 168  * crypto, or some other error if there is a matching certificate but
 169  * the signature check cannot be performed.
 170  */
 171 int restrict_link_by_digsig(struct key *dest_keyring,
 172                             const struct key_type *type,
 173                             const union key_payload *payload,
 174                             struct key *trust_keyring)
 175 {
 176         const struct public_key *pkey;
 177
 178         if (type != &key_type_asymmetric)
 179                 return -EOPNOTSUPP;
 180
 181         pkey = payload->data[asym_crypto];
 182
 183         if (!pkey)
 184                 return -ENOPKG;
 185
 186         if (!test_bit(KEY_EFLAG_DIGITALSIG, &pkey->key_eflags))
 187                 return -ENOKEY;
 188
 189         if (test_bit(KEY_EFLAG_CA, &pkey->key_eflags))
 190                 return -ENOKEY;
 191
 192         if (test_bit(KEY_EFLAG_KEYCERTSIGN, &pkey->key_eflags))
 193                 return -ENOKEY;
 194
 195         return restrict_link_by_signature(dest_keyring, type, payload,
 196                                           trust_keyring);
 197 }
 198
 199 static bool match_either_id(const struct asymmetric_key_id **pair,
 200                             const struct asymmetric_key_id *single)
 201 {
 202         return (asymmetric_key_id_same(pair[0], single) ||
 203                 asymmetric_key_id_same(pair[1], single));
 204 }
 205
 206 static int key_or_keyring_common(struct key *dest_keyring,
 207                                  const struct key_type *type,
 208                                  const union key_payload *payload,
 209                                  struct key *trusted, bool check_dest)
 210 {
 211         const struct public_key_signature *sig;
 212         struct key *key = NULL;
 213         int ret;
 214
 215         pr_devel("==>%s()\n", __func__);
 216
 217         if (!dest_keyring)
 218                 return -ENOKEY;
 219         else if (dest_keyring->type != &key_type_keyring)
 220                 return -EOPNOTSUPP;
 221
 222         if (!trusted && !check_dest)
 223                 return -ENOKEY;
 224
 225         if (type != &key_type_asymmetric)
 226                 return -EOPNOTSUPP;
 227
 228         sig = payload->data[asym_auth];
 229         if (!sig)
 230                 return -ENOPKG;
 231         if (!sig->auth_ids[0] && !sig->auth_ids[1] && !sig->auth_ids[2])
 232                 return -ENOKEY;
 233
 234         if (trusted) {
 235                 if (trusted->type == &key_type_keyring) {
 236                         /* See if we have a key that signed this one. */
 237                         key = find_asymmetric_key(trusted, sig->auth_ids[0],
 238                                                   sig->auth_ids[1],
 239                                                   sig->auth_ids[2], false);
 240                         if (IS_ERR(key))
 241                                 key = NULL;
 242                 } else if (trusted->type == &key_type_asymmetric) {
 243                         const struct asymmetric_key_id **signer_ids;
 244
 245                         signer_ids = (const struct asymmetric_key_id **)
 246                                 asymmetric_key_ids(trusted)->id;
 247
 248                         /*
 249                          * The auth_ids come from the candidate key (the
 250                          * one that is being considered for addition to
 251                          * dest_keyring) and identify the key that was
 252                          * used to sign.
 253                          *
 254                          * The signer_ids are identifiers for the
 255                          * signing key specified for dest_keyring.
 256                          *
 257                          * The first auth_id is the preferred id, 2nd and
 258                          * 3rd are the fallbacks. If exactly one of
 259                          * auth_ids[0] and auth_ids[1] is present, it may
 260                          * match either signer_ids[0] or signed_ids[1].
 261                          * If both are present the first one may match
 262                          * either signed_id but the second one must match
 263                          * the second signer_id. If neither of them is
 264                          * available, auth_ids[2] is matched against
 265                          * signer_ids[2] as a fallback.
 266                          */
 267                         if (!sig->auth_ids[0] && !sig->auth_ids[1]) {
 268                                 if (asymmetric_key_id_same(signer_ids[2],
 269                                                            sig->auth_ids[2]))
 270                                         key = __key_get(trusted);
 271
 272                         } else if (!sig->auth_ids[0] || !sig->auth_ids[1]) {
 273                                 const struct asymmetric_key_id *auth_id;
 274
 275                                 auth_id = sig->auth_ids[0] ?: sig->auth_ids[1];
 276                                 if (match_either_id(signer_ids, auth_id))
 277                                         key = __key_get(trusted);
 278
 279                         } else if (asymmetric_key_id_same(signer_ids[1],
 280                                                           sig->auth_ids[1]) &&
 281                                    match_either_id(signer_ids,
 282                                                    sig->auth_ids[0])) {
 283                                 key = __key_get(trusted);
 284                         }
 285                 } else {
 286                         return -EOPNOTSUPP;
 287                 }
 288         }
 289
 290         if (check_dest && !key) {
 291                 /* See if the destination has a key that signed this one. */
 292                 key = find_asymmetric_key(dest_keyring, sig->auth_ids[0],
 293                                           sig->auth_ids[1], sig->auth_ids[2],
 294                                           false);
 295                 if (IS_ERR(key))
 296                         key = NULL;
 297         }
 298
 299         if (!key)
 300                 return -ENOKEY;
 301
 302         ret = key_validate(key);
 303         if (ret == 0)
 304                 ret = verify_signature(key, sig);
 305
 306         key_put(key);
 307         return ret;
 308 }
 309
 310 /**
 311  * restrict_link_by_key_or_keyring - Restrict additions to a ring of public
 312  * keys using the restrict_key information stored in the ring.
 313  * @dest_keyring: Keyring being linked to.
 314  * @type: The type of key being added.
 315  * @payload: The payload of the new key.
 316  * @trusted: A key or ring of keys that can be used to vouch for the new cert.
 317  *
 318  * Check the new certificate only against the key or keys passed in the data
 319  * parameter. If one of those is the signing key and validates the new
 320  * certificate, then mark the new certificate as being ok to link.
 321  *
 322  * Returns 0 if the new certificate was accepted, -ENOKEY if we
 323  * couldn't find a matching parent certificate in the trusted list,
 324  * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
 325  * unsupported crypto, or some other error if there is a matching certificate
 326  * but the signature check cannot be performed.
 327  */
 328 int restrict_link_by_key_or_keyring(struct key *dest_keyring,
 329                                     const struct key_type *type,
 330                                     const union key_payload *payload,
 331                                     struct key *trusted)
 332 {
 333         return key_or_keyring_common(dest_keyring, type, payload, trusted,
 334                                      false);
 335 }
 336
 337 /**
 338  * restrict_link_by_key_or_keyring_chain - Restrict additions to a ring of
 339  * public keys using the restrict_key information stored in the ring.
 340  * @dest_keyring: Keyring being linked to.
 341  * @type: The type of key being added.
 342  * @payload: The payload of the new key.
 343  * @trusted: A key or ring of keys that can be used to vouch for the new cert.
 344  *
 345  * Check the new certificate against the key or keys passed in the data
 346  * parameter and against the keys already linked to the destination keyring. If
 347  * one of those is the signing key and validates the new certificate, then mark
 348  * the new certificate as being ok to link.
 349  *
 350  * Returns 0 if the new certificate was accepted, -ENOKEY if we
 351  * couldn't find a matching parent certificate in the trusted list,
 352  * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
 353  * unsupported crypto, or some other error if there is a matching certificate
 354  * but the signature check cannot be performed.
 355  */
 356 int restrict_link_by_key_or_keyring_chain(struct key *dest_keyring,
 357                                           const struct key_type *type,
 358                                           const union key_payload *payload,
 359                                           struct key *trusted)
 360 {
 361         return key_or_keyring_common(dest_keyring, type, payload, trusted,
 362                                      true);
 363 }