Initial import

1 files changed, 200 insertions, 0 deletions

diff --git a/crypto/asymmetric_keys/pkcs7_trust.c b/crypto/asymmetric_keys/pkcs7_trust.c
new file mode 100644
index 000000000..1d2937607
--- /dev/null
+++ b/crypto/asymmetric_keys/pkcs7_trust.c
@@ -0,0 +1,200 @@
+/* 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,
+						  false);
+		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.
+			 */
+			pr_devel("sinfo %u: Cert %u as key %x\n",
+				 sinfo->index, x509->index, key_serial(key));
+			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->authority) {
+		key = x509_request_asymmetric_key(trust_keyring, last->authority,
+						  false);
+		if (!IS_ERR(key)) {
+			x509 = last;
+			pr_devel("sinfo %u: Root cert %u signer is key %x\n",
+				 sinfo->index, x509->index, key_serial(key));
+			goto matched;
+		}
+		if (PTR_ERR(key) != -ENOKEY)
+			return PTR_ERR(key);
+	}
+
+	/* As a last resort, see if we have a trusted public key that matches
+	 * the signed info directly.
+	 */
+	key = x509_request_asymmetric_key(trust_keyring,
+					  sinfo->signing_cert_id,
+					  false);
+	if (!IS_ERR(key)) {
+		pr_devel("sinfo %u: Direct signer is key %x\n",
+			 sinfo->index, key_serial(key));
+		x509 = NULL;
+		goto matched;
+	}
+	if (PTR_ERR(key) != -ENOKEY)
+		return PTR_ERR(key);
+
+	kleave(" = -ENOKEY [no backref]");
+	return -ENOKEY;
+
+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:
+	if (x509) {
+		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);