a511e1af8b
Move the point at which a key is determined to be trustworthy to __key_link() so that we use the contents of the keyring being linked in to to determine whether the key being linked in is trusted or not. What is 'trusted' then becomes a matter of what's in the keyring. Currently, the test is done when the key is parsed, but given that at that point we can only sensibly refer to the contents of the system trusted keyring, we can only use that as the basis for working out the trustworthiness of a new key. With this change, a trusted keyring is a set of keys that once the trusted-only flag is set cannot be added to except by verification through one of the contained keys. Further, adding a key into a trusted keyring, whilst it might grant trustworthiness in the context of that keyring, does not automatically grant trustworthiness in the context of a second keyring to which it could be secondarily linked. To accomplish this, the authentication data associated with the key source must now be retained. For an X.509 cert, this means the contents of the AuthorityKeyIdentifier and the signature data. If system keyrings are disabled then restrict_link_by_builtin_trusted() resolves to restrict_link_reject(). The integrity digital signature code still works correctly with this as it was previously using KEY_FLAG_TRUSTED_ONLY, which doesn't permit anything to be added if there is no system keyring against which trust can be determined. Signed-off-by: David Howells <dhowells@redhat.com>
109 lines
3 KiB
C
109 lines
3 KiB
C
/* Instantiate a public key crypto key from an X.509 Certificate
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*
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* Copyright (C) 2012, 2016 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#define pr_fmt(fmt) "ASYM: "fmt
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/err.h>
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#include <crypto/public_key.h>
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#include "asymmetric_keys.h"
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static bool use_builtin_keys;
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static struct asymmetric_key_id *ca_keyid;
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#ifndef MODULE
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static struct {
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struct asymmetric_key_id id;
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unsigned char data[10];
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} cakey;
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static int __init ca_keys_setup(char *str)
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{
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if (!str) /* default system keyring */
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return 1;
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if (strncmp(str, "id:", 3) == 0) {
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struct asymmetric_key_id *p = &cakey.id;
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size_t hexlen = (strlen(str) - 3) / 2;
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int ret;
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if (hexlen == 0 || hexlen > sizeof(cakey.data)) {
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pr_err("Missing or invalid ca_keys id\n");
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return 1;
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}
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ret = __asymmetric_key_hex_to_key_id(str + 3, p, hexlen);
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if (ret < 0)
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pr_err("Unparsable ca_keys id hex string\n");
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else
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ca_keyid = p; /* owner key 'id:xxxxxx' */
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} else if (strcmp(str, "builtin") == 0) {
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use_builtin_keys = true;
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}
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return 1;
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}
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__setup("ca_keys=", ca_keys_setup);
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#endif
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/**
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* restrict_link_by_signature - Restrict additions to a ring of public keys
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* @trust_keyring: A ring of keys that can be used to vouch for the new cert.
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* @type: The type of key being added.
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* @payload: The payload of the new key.
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*
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* Check the new certificate against the ones in the trust keyring. If one of
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* those is the signing key and validates the new certificate, then mark the
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* new certificate as being trusted.
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*
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* Returns 0 if the new certificate was accepted, -ENOKEY if we couldn't find a
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* matching parent certificate in the trusted list, -EKEYREJECTED if the
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* signature check fails or the key is blacklisted and some other error if
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* there is a matching certificate but the signature check cannot be performed.
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*/
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int restrict_link_by_signature(struct key *trust_keyring,
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const struct key_type *type,
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const union key_payload *payload)
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{
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const struct public_key_signature *sig;
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struct key *key;
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int ret;
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pr_devel("==>%s()\n", __func__);
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if (!trust_keyring)
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return -ENOKEY;
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if (type != &key_type_asymmetric)
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return -EOPNOTSUPP;
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sig = payload->data[asym_auth];
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if (!sig->auth_ids[0] && !sig->auth_ids[1])
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return 0;
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if (ca_keyid && !asymmetric_key_id_partial(sig->auth_ids[1], ca_keyid))
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return -EPERM;
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/* See if we have a key that signed this one. */
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key = find_asymmetric_key(trust_keyring,
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sig->auth_ids[0], sig->auth_ids[1],
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false);
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if (IS_ERR(key))
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return -ENOKEY;
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if (use_builtin_keys && !test_bit(KEY_FLAG_BUILTIN, &key->flags))
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ret = -ENOKEY;
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else
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ret = verify_signature(key, sig);
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key_put(key);
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return ret;
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}
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