2014-07-01 17:40:20 +02:00
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/* Validate the trust chain of a PKCS#7 message.
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*
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* Copyright (C) 2012 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) "PKCS7: "fmt
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#include <linux/kernel.h>
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#include <linux/export.h>
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#include <linux/slab.h>
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#include <linux/err.h>
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#include <linux/asn1.h>
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#include <linux/key.h>
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#include <keys/asymmetric-type.h>
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2016-02-02 19:08:53 +01:00
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#include <crypto/public_key.h>
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2014-07-01 17:40:20 +02:00
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#include "pkcs7_parser.h"
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/**
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* Check the trust on one PKCS#7 SignedInfo block.
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*/
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2014-09-16 18:07:07 +02:00
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static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,
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struct pkcs7_signed_info *sinfo,
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struct key *trust_keyring)
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2014-07-01 17:40:20 +02:00
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{
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struct public_key_signature *sig = &sinfo->sig;
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struct x509_certificate *x509, *last = NULL, *p;
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struct key *key;
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bool trusted;
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int ret;
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kenter(",%u,", sinfo->index);
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2014-09-16 18:36:15 +02:00
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if (sinfo->unsupported_crypto) {
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kleave(" = -ENOPKG [cached]");
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return -ENOPKG;
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}
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2014-07-01 17:40:20 +02:00
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for (x509 = sinfo->signer; x509; x509 = x509->signer) {
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if (x509->seen) {
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if (x509->verified) {
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trusted = x509->trusted;
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goto verified;
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}
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kleave(" = -ENOKEY [cached]");
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return -ENOKEY;
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}
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x509->seen = true;
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/* Look to see if this certificate is present in the trusted
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* keys.
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*/
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2015-07-20 22:16:26 +02:00
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key = x509_request_asymmetric_key(trust_keyring,
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x509->id, x509->skid,
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2014-10-06 16:21:05 +02:00
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false);
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2014-09-16 18:36:17 +02:00
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if (!IS_ERR(key)) {
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2014-07-01 17:40:20 +02:00
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/* One of the X.509 certificates in the PKCS#7 message
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* is apparently the same as one we already trust.
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* Verify that the trusted variant can also validate
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* the signature on the descendant.
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*/
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2014-09-16 18:36:17 +02:00
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pr_devel("sinfo %u: Cert %u as key %x\n",
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sinfo->index, x509->index, key_serial(key));
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2014-07-01 17:40:20 +02:00
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goto matched;
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2014-09-16 18:36:17 +02:00
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}
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2014-07-01 17:40:20 +02:00
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if (key == ERR_PTR(-ENOMEM))
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return -ENOMEM;
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/* Self-signed certificates form roots of their own, and if we
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* don't know them, then we can't accept them.
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*/
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if (x509->next == x509) {
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kleave(" = -ENOKEY [unknown self-signed]");
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return -ENOKEY;
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}
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might_sleep();
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last = x509;
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sig = &last->sig;
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}
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/* No match - see if the root certificate has a signer amongst the
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* trusted keys.
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*/
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2015-07-20 22:16:26 +02:00
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if (last && (last->akid_id || last->akid_skid)) {
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key = x509_request_asymmetric_key(trust_keyring,
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last->akid_id,
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last->akid_skid,
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2014-10-06 16:21:05 +02:00
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false);
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2014-09-16 18:36:17 +02:00
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if (!IS_ERR(key)) {
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x509 = last;
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pr_devel("sinfo %u: Root cert %u signer is key %x\n",
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sinfo->index, x509->index, key_serial(key));
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goto matched;
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}
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if (PTR_ERR(key) != -ENOKEY)
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return PTR_ERR(key);
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2014-07-01 17:40:20 +02:00
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}
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2014-09-16 18:36:17 +02:00
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/* As a last resort, see if we have a trusted public key that matches
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* the signed info directly.
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*/
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key = x509_request_asymmetric_key(trust_keyring,
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2014-10-06 16:21:05 +02:00
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sinfo->signing_cert_id,
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2015-07-20 22:16:26 +02:00
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NULL,
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2014-10-06 16:21:05 +02:00
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false);
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2014-09-16 18:36:17 +02:00
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if (!IS_ERR(key)) {
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pr_devel("sinfo %u: Direct signer is key %x\n",
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sinfo->index, key_serial(key));
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x509 = NULL;
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goto matched;
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}
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if (PTR_ERR(key) != -ENOKEY)
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return PTR_ERR(key);
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kleave(" = -ENOKEY [no backref]");
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return -ENOKEY;
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2014-07-01 17:40:20 +02:00
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matched:
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ret = verify_signature(key, sig);
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trusted = test_bit(KEY_FLAG_TRUSTED, &key->flags);
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key_put(key);
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if (ret < 0) {
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if (ret == -ENOMEM)
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return ret;
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kleave(" = -EKEYREJECTED [verify %d]", ret);
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return -EKEYREJECTED;
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}
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verified:
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2014-09-16 18:36:17 +02:00
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if (x509) {
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x509->verified = true;
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for (p = sinfo->signer; p != x509; p = p->signer) {
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p->verified = true;
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p->trusted = trusted;
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}
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2014-07-01 17:40:20 +02:00
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}
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sinfo->trusted = trusted;
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kleave(" = 0");
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return 0;
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}
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/**
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* pkcs7_validate_trust - Validate PKCS#7 trust chain
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* @pkcs7: The PKCS#7 certificate to validate
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* @trust_keyring: Signing certificates to use as starting points
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* @_trusted: Set to true if trustworth, false otherwise
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*
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* Validate that the certificate chain inside the PKCS#7 message intersects
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* keys we already know and trust.
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*
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* Returns, in order of descending priority:
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*
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* (*) -EKEYREJECTED if a signature failed to match for which we have a valid
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* key, or:
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*
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* (*) 0 if at least one signature chain intersects with the keys in the trust
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* keyring, or:
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*
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* (*) -ENOPKG if a suitable crypto module couldn't be found for a check on a
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* chain.
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*
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* (*) -ENOKEY if we couldn't find a match for any of the signature chains in
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* the message.
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*
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* May also return -ENOMEM.
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*/
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int pkcs7_validate_trust(struct pkcs7_message *pkcs7,
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struct key *trust_keyring,
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bool *_trusted)
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{
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struct pkcs7_signed_info *sinfo;
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struct x509_certificate *p;
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2014-09-16 18:36:15 +02:00
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int cached_ret = -ENOKEY;
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int ret;
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2014-07-01 17:40:20 +02:00
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2016-03-20 23:23:46 +01:00
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*_trusted = false;
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2014-07-01 17:40:20 +02:00
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for (p = pkcs7->certs; p; p = p->next)
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p->seen = false;
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for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
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ret = pkcs7_validate_trust_one(pkcs7, sinfo, trust_keyring);
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2014-09-16 18:36:15 +02:00
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switch (ret) {
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case -ENOKEY:
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continue;
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case -ENOPKG:
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if (cached_ret == -ENOKEY)
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2014-07-01 17:40:20 +02:00
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cached_ret = -ENOPKG;
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2014-09-16 18:36:15 +02:00
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continue;
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case 0:
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*_trusted |= sinfo->trusted;
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cached_ret = 0;
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continue;
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default:
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return ret;
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2014-07-01 17:40:20 +02:00
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}
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}
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return cached_ret;
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}
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EXPORT_SYMBOL_GPL(pkcs7_validate_trust);
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