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Diffstat (limited to 'crypto/asymmetric_keys/pkcs7_trust.c')
-rw-r--r--crypto/asymmetric_keys/pkcs7_trust.c166
1 files changed, 166 insertions, 0 deletions
diff --git a/crypto/asymmetric_keys/pkcs7_trust.c b/crypto/asymmetric_keys/pkcs7_trust.c
new file mode 100644
index 000000000000..e666eb011a85
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+++ b/crypto/asymmetric_keys/pkcs7_trust.c
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+/* 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.
+ */
+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);
+
+ 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->subject,
+ x509->fingerprint);
+ 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->issuer,
+ 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 = 0, 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);
+ if (ret < 0) {
+ if (ret == -ENOPKG) {
+ cached_ret = -ENOPKG;
+ } else if (ret == -ENOKEY) {
+ if (cached_ret == 0)
+ cached_ret = -ENOKEY;
+ } else {
+ return ret;
+ }
+ }
+ *_trusted |= sinfo->trusted;
+ }
+
+ return cached_ret;
+}
+EXPORT_SYMBOL_GPL(pkcs7_validate_trust);