Find the intersection between the X.509 certificate chain contained in a PKCS#7
message and a set of keys that we already know and trust.
Signed-off-by: David Howells <dhowe...@redhat.com>
---
crypto/asymmetric_keys/Makefile | 1
crypto/asymmetric_keys/pefile_parser.c | 6 +
crypto/asymmetric_keys/pkcs7_parser.h | 6 +
crypto/asymmetric_keys/pkcs7_trust.c | 145 ++++++++++++++++++++++++++++++++
kernel/modsign_pubkey.c | 1
5 files changed, 159 insertions(+)
create mode 100644 crypto/asymmetric_keys/pkcs7_trust.c
diff --git a/crypto/asymmetric_keys/Makefile b/crypto/asymmetric_keys/Makefile
index 566dd45..ddc64bb 100644
--- a/crypto/asymmetric_keys/Makefile
+++ b/crypto/asymmetric_keys/Makefile
@@ -33,6 +33,7 @@ obj-$(CONFIG_PKCS7_MESSAGE_PARSER) += pkcs7_message.o
pkcs7_message-y := \
pkcs7-asn1.o \
pkcs7_parser.o \
+ pkcs7_trust.o \
pkcs7_verify.o
$(obj)/pkcs7_parser.o: $(obj)/pkcs7-asn1.h
diff --git a/crypto/asymmetric_keys/pefile_parser.c
b/crypto/asymmetric_keys/pefile_parser.c
index 9ede195..1ab1890 100644
--- a/crypto/asymmetric_keys/pefile_parser.c
+++ b/crypto/asymmetric_keys/pefile_parser.c
@@ -23,6 +23,8 @@
#include "public_key.h"
#include "pefile_parser.h"
+extern struct key *modsign_keyring;
+
/*
* Parse a PE binary.
*/
@@ -428,6 +430,10 @@ static int pefile_key_preparse(struct
key_preparsed_payload *prep)
if (ret < 0)
goto error;
+ ret = pkcs7_validate_trust(pkcs7, modsign_keyring);
+ if (ret < 0)
+ goto error;
+
ret = -ENOANO; // Not yet complete
error:
diff --git a/crypto/asymmetric_keys/pkcs7_parser.h
b/crypto/asymmetric_keys/pkcs7_parser.h
index 5415857..f6df500 100644
--- a/crypto/asymmetric_keys/pkcs7_parser.h
+++ b/crypto/asymmetric_keys/pkcs7_parser.h
@@ -60,6 +60,12 @@ extern struct pkcs7_message *pkcs7_parse_message(const void
*data,
extern void pkcs7_free_message(struct pkcs7_message *pkcs7);
/*
+ * pkcs7_trust.c
+ */
+extern int pkcs7_validate_trust(struct pkcs7_message *pkcs7,
+ struct key *trust_keyring);
+
+/*
* pkcs7_verify.c
*/
extern int pkcs7_verify(struct pkcs7_message *pkcs7);
diff --git a/crypto/asymmetric_keys/pkcs7_trust.c
b/crypto/asymmetric_keys/pkcs7_trust.c
new file mode 100644
index 0000000..9abcb39
--- /dev/null
+++ b/crypto/asymmetric_keys/pkcs7_trust.c
@@ -0,0 +1,145 @@
+/* Validate the trust chain of a PKCS#7 message.
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowe...@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"
+
+/*
+ * Request an asymmetric key.
+ */
+static struct key *pkcs7_request_asymmetric_key(
+ struct key *keyring,
+ const char *signer, size_t signer_len,
+ const char *authority, size_t auth_len)
+{
+ key_ref_t key;
+ char *id;
+
+ kenter(",%zu,,%zu", signer_len, auth_len);
+
+ /* Construct an identifier. */
+ id = kmalloc(signer_len + 2 + auth_len + 1, GFP_KERNEL);
+ if (!id)
+ return ERR_PTR(-ENOMEM);
+
+ memcpy(id, signer, signer_len);
+ id[signer_len + 0] = ':';
+ id[signer_len + 1] = ' ';
+ memcpy(id + signer_len + 2, authority, auth_len);
+ id[signer_len + 2 + auth_len] = 0;
+
+ pr_debug("Look up: \"%s\"\n", id);
+
+ key = keyring_search(make_key_ref(keyring, 1),
+ &key_type_asymmetric, id);
+ if (IS_ERR(key))
+ pr_debug("Request for module key '%s' err %ld\n",
+ id, PTR_ERR(key));
+ kfree(id);
+
+ if (IS_ERR(key)) {
+ switch (PTR_ERR(key)) {
+ /* Hide some search errors */
+ case -EACCES:
+ case -ENOTDIR:
+ case -EAGAIN:
+ return ERR_PTR(-ENOKEY);
+ default:
+ return ERR_CAST(key);
+ }
+ }
+
+ pr_devel("<==%s() = 0 [%x]\n", __func__,
key_serial(key_ref_to_ptr(key)));
+ return key_ref_to_ptr(key);
+}
+
+/*
+ * Validate that the certificate chain inside the PKCS#7 message intersects
+ * keys we already know and trust.
+ */
+int pkcs7_validate_trust(struct pkcs7_message *pkcs7,
+ struct key *trust_keyring)
+{
+ struct public_key_signature *sig = &pkcs7->sig;
+ struct x509_certificate *x509, *last = NULL;
+ struct key *key;
+ int ret;
+
+ kenter("");
+
+ for (x509 = pkcs7->signer; x509; x509 = x509->next) {
+ /* Look to see if this certificate is present in the trusted
+ * keys.
+ */
+ key = pkcs7_request_asymmetric_key(
+ trust_keyring,
+ x509->subject, strlen(x509->subject),
+ x509->fingerprint, strlen(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 descendent.
+ */
+ 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(" = -EKEYREJECTED [unknown self-signed]");
+ return -EKEYREJECTED;
+ }
+
+ 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(" = -EKEYREJECTED [no backref]");
+ return -EKEYREJECTED;
+ }
+
+ key = pkcs7_request_asymmetric_key(
+ trust_keyring,
+ last->issuer, strlen(last->issuer),
+ last->authority, strlen(last->authority));
+ if (IS_ERR(key))
+ return PTR_ERR(key) == -ENOMEM ? -ENOMEM : -EKEYREJECTED;
+
+matched:
+ ret = verify_signature(key, sig);
+ key_put(key);
+ if (ret < 0) {
+ if (ret == -ENOMEM)
+ return ret;
+ kleave(" = -EKEYREJECTED [verify %d]", ret);
+ return -EKEYREJECTED;
+ }
+
+ kleave(" = 0");
+ return 0;
+}
+EXPORT_SYMBOL_GPL(pkcs7_validate_trust);
diff --git a/kernel/modsign_pubkey.c b/kernel/modsign_pubkey.c
index 4646eb2..602be22 100644
--- a/kernel/modsign_pubkey.c
+++ b/kernel/modsign_pubkey.c
@@ -17,6 +17,7 @@
#include "module-internal.h"
struct key *modsign_keyring;
+EXPORT_SYMBOL_GPL(modsign_keyring);
extern __initdata const u8 modsign_certificate_list[];
extern __initdata const u8 modsign_certificate_list_end[];
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
