[deliverable/linux.git] / crypto / asymmetric_keys / pkcs7_trust.c

/* Validate the trust chain of a PKCS#7 message.
 *
 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#define pr_fmt(fmt) "PKCS7: "fmt
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/asn1.h>
#include <linux/key.h>
#include <keys/asymmetric-type.h>
#include "public_key.h"
#include "pkcs7_parser.h"

/**
 * Check the trust on one PKCS#7 SignedInfo block.
 */
static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,
				    struct pkcs7_signed_info *sinfo,
				    struct key *trust_keyring)
{
	struct public_key_signature *sig = &sinfo->sig;
	struct x509_certificate *x509, *last = NULL, *p;
	struct key *key;
	bool trusted;
	int ret;

	kenter(",%u,", sinfo->index);

	if (sinfo->unsupported_crypto) {
		kleave(" = -ENOPKG [cached]");
		return -ENOPKG;
	}

	for (x509 = sinfo->signer; x509; x509 = x509->signer) {
		if (x509->seen) {
			if (x509->verified) {
				trusted = x509->trusted;
				goto verified;
			}
			kleave(" = -ENOKEY [cached]");
			return -ENOKEY;
		}
		x509->seen = true;

		/* Look to see if this certificate is present in the trusted
		 * keys.
		 */
		key = x509_request_asymmetric_key(trust_keyring, x509->id);
		if (!IS_ERR(key))
			/* One of the X.509 certificates in the PKCS#7 message
			 * is apparently the same as one we already trust.
			 * Verify that the trusted variant can also validate
			 * the signature on the descendant.
			 */
			goto matched;
		if (key == ERR_PTR(-ENOMEM))
			return -ENOMEM;

		 /* Self-signed certificates form roots of their own, and if we
		  * don't know them, then we can't accept them.
		  */
		if (x509->next == x509) {
			kleave(" = -ENOKEY [unknown self-signed]");
			return -ENOKEY;
		}

		might_sleep();
		last = x509;
		sig = &last->sig;
	}

	/* No match - see if the root certificate has a signer amongst the
	 * trusted keys.
	 */
	if (!last || !last->issuer || !last->authority) {
		kleave(" = -ENOKEY [no backref]");
		return -ENOKEY;
	}

	key = x509_request_asymmetric_key(trust_keyring, last->authority);
	if (IS_ERR(key))
		return PTR_ERR(key) == -ENOMEM ? -ENOMEM : -ENOKEY;
	x509 = last;

matched:
	ret = verify_signature(key, sig);
	trusted = test_bit(KEY_FLAG_TRUSTED, &key->flags);
	key_put(key);
	if (ret < 0) {
		if (ret == -ENOMEM)
			return ret;
		kleave(" = -EKEYREJECTED [verify %d]", ret);
		return -EKEYREJECTED;
	}

verified:
	x509->verified = true;
	for (p = sinfo->signer; p != x509; p = p->signer) {
		p->verified = true;
		p->trusted = trusted;
	}
	sinfo->trusted = trusted;
	kleave(" = 0");
	return 0;
}

/**
 * pkcs7_validate_trust - Validate PKCS#7 trust chain
 * @pkcs7: The PKCS#7 certificate to validate
 * @trust_keyring: Signing certificates to use as starting points
 * @_trusted: Set to true if trustworth, false otherwise
 *
 * Validate that the certificate chain inside the PKCS#7 message intersects
 * keys we already know and trust.
 *
 * Returns, in order of descending priority:
 *
 *  (*) -EKEYREJECTED if a signature failed to match for which we have a valid
 *	key, or:
 *
 *  (*) 0 if at least one signature chain intersects with the keys in the trust
 *	keyring, or:
 *
 *  (*) -ENOPKG if a suitable crypto module couldn't be found for a check on a
 *	chain.
 *
 *  (*) -ENOKEY if we couldn't find a match for any of the signature chains in
 *	the message.
 *
 * May also return -ENOMEM.
 */
int pkcs7_validate_trust(struct pkcs7_message *pkcs7,
			 struct key *trust_keyring,
			 bool *_trusted)
{
	struct pkcs7_signed_info *sinfo;
	struct x509_certificate *p;
	int cached_ret = -ENOKEY;
	int ret;

	for (p = pkcs7->certs; p; p = p->next)
		p->seen = false;

	for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
		ret = pkcs7_validate_trust_one(pkcs7, sinfo, trust_keyring);
		switch (ret) {
		case -ENOKEY:
			continue;
		case -ENOPKG:
			if (cached_ret == -ENOKEY)
				cached_ret = -ENOPKG;
			continue;
		case 0:
			*_trusted |= sinfo->trusted;
			cached_ret = 0;
			continue;
		default:
			return ret;
		}
	}

	return cached_ret;
}
EXPORT_SYMBOL_GPL(pkcs7_validate_trust);
Commit	Line	Data
08815b62 DH	1	/* Validate the trust chain of a PKCS#7 message.
	2	*
	3	* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
	4	* Written by David Howells (dhowells@redhat.com)
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public Licence
	8	* as published by the Free Software Foundation; either version
	9	* 2 of the Licence, or (at your option) any later version.
	10	*/
	11
	12	#define pr_fmt(fmt) "PKCS7: "fmt
	13	#include <linux/kernel.h>
	14	#include <linux/export.h>
	15	#include <linux/slab.h>
	16	#include <linux/err.h>
	17	#include <linux/asn1.h>
	18	#include <linux/key.h>
	19	#include <keys/asymmetric-type.h>
	20	#include "public_key.h"
	21	#include "pkcs7_parser.h"
	22
08815b62 DH	23	/**
	24	* Check the trust on one PKCS#7 SignedInfo block.
	25	*/
15155b9a DH	26	static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,
	27	struct pkcs7_signed_info *sinfo,
	28	struct key *trust_keyring)
08815b62 DH	29	{
	30	struct public_key_signature *sig = &sinfo->sig;
	31	struct x509_certificate x509, last = NULL, *p;
	32	struct key *key;
	33	bool trusted;
	34	int ret;
	35
	36	kenter(",%u,", sinfo->index);
	37
41559420 DH	38	if (sinfo->unsupported_crypto) {
	39	kleave(" = -ENOPKG [cached]");
	40	return -ENOPKG;
	41	}
	42
08815b62 DH	43	for (x509 = sinfo->signer; x509; x509 = x509->signer) {
	44	if (x509->seen) {
	45	if (x509->verified) {
	46	trusted = x509->trusted;
	47	goto verified;
	48	}
	49	kleave(" = -ENOKEY [cached]");
	50	return -ENOKEY;
	51	}
	52	x509->seen = true;
	53
	54	/* Look to see if this certificate is present in the trusted
	55	* keys.
	56	*/
46963b77	57	key = x509_request_asymmetric_key(trust_keyring, x509->id);
08815b62 DH	58	if (!IS_ERR(key))
	59	/* One of the X.509 certificates in the PKCS#7 message
	60	* is apparently the same as one we already trust.
	61	* Verify that the trusted variant can also validate
	62	* the signature on the descendant.
	63	*/
	64	goto matched;
	65	if (key == ERR_PTR(-ENOMEM))
	66	return -ENOMEM;
	67
	68	/* Self-signed certificates form roots of their own, and if we
	69	* don't know them, then we can't accept them.
	70	*/
	71	if (x509->next == x509) {
	72	kleave(" = -ENOKEY [unknown self-signed]");
	73	return -ENOKEY;
	74	}
	75
	76	might_sleep();
	77	last = x509;
	78	sig = &last->sig;
	79	}
	80
	81	/* No match - see if the root certificate has a signer amongst the
	82	* trusted keys.
	83	*/
	84	if (!last \|\| !last->issuer \|\| !last->authority) {
	85	kleave(" = -ENOKEY [no backref]");
	86	return -ENOKEY;
	87	}
	88
46963b77	89	key = x509_request_asymmetric_key(trust_keyring, last->authority);
08815b62 DH	90	if (IS_ERR(key))
	91	return PTR_ERR(key) == -ENOMEM ? -ENOMEM : -ENOKEY;
	92	x509 = last;
	93
	94	matched:
	95	ret = verify_signature(key, sig);
	96	trusted = test_bit(KEY_FLAG_TRUSTED, &key->flags);
	97	key_put(key);
	98	if (ret < 0) {
	99	if (ret == -ENOMEM)
	100	return ret;
	101	kleave(" = -EKEYREJECTED [verify %d]", ret);
	102	return -EKEYREJECTED;
	103	}
	104
	105	verified:
	106	x509->verified = true;
	107	for (p = sinfo->signer; p != x509; p = p->signer) {
	108	p->verified = true;
	109	p->trusted = trusted;
	110	}
	111	sinfo->trusted = trusted;
	112	kleave(" = 0");
	113	return 0;
	114	}
	115
	116	/**
	117	* pkcs7_validate_trust - Validate PKCS#7 trust chain
	118	* @pkcs7: The PKCS#7 certificate to validate
	119	* @trust_keyring: Signing certificates to use as starting points
	120	* @_trusted: Set to true if trustworth, false otherwise
	121	*
	122	* Validate that the certificate chain inside the PKCS#7 message intersects
	123	* keys we already know and trust.
	124	*
	125	* Returns, in order of descending priority:
	126	*
	127	* (*) -EKEYREJECTED if a signature failed to match for which we have a valid
	128	* key, or:
	129	*
	130	* (*) 0 if at least one signature chain intersects with the keys in the trust
	131	* keyring, or:
	132	*
	133	* (*) -ENOPKG if a suitable crypto module couldn't be found for a check on a
	134	* chain.
	135	*
	136	* (*) -ENOKEY if we couldn't find a match for any of the signature chains in
	137	* the message.
	138	*
	139	* May also return -ENOMEM.
	140	*/
	141	int pkcs7_validate_trust(struct pkcs7_message *pkcs7,
	142	struct key *trust_keyring,
	143	bool *_trusted)
	144	{
	145	struct pkcs7_signed_info *sinfo;
	146	struct x509_certificate *p;
41559420 DH	147	int cached_ret = -ENOKEY;
41559420 DH	148	int ret;
08815b62 DH	149
	150	for (p = pkcs7->certs; p; p = p->next)
	151	p->seen = false;
	152
	153	for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
	154	ret = pkcs7_validate_trust_one(pkcs7, sinfo, trust_keyring);
41559420 DH	155	switch (ret) {
	156	case -ENOKEY:
	157	continue;
	158	case -ENOPKG:
	159	if (cached_ret == -ENOKEY)
08815b62	160	cached_ret = -ENOPKG;
41559420 DH	161	continue;
	162	case 0:
	163	*_trusted \|= sinfo->trusted;
	164	cached_ret = 0;
	165	continue;
	166	default:
	167	return ret;
08815b62	168	}
08815b62 DH	169	}
	170
	171	return cached_ret;
	172	}
	173	EXPORT_SYMBOL_GPL(pkcs7_validate_trust);