Add a function by which crypto keys can be requested. A keyring is supplied
for the function to search (which can be, say, a system keyring containing keys
for kernel module signature checking). The function also provides a point at
which hardware key caches, such as a TPM, can be consulted.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---
Documentation/security/keys-crypto.txt | 12 ++++
include/keys/crypto-type.h | 3 +
security/keys/Makefile | 2 -
security/keys/crypto_request.c | 87 ++++++++++++++++++++++++++++++++
4 files changed, 103 insertions(+), 1 deletions(-)
create mode 100644 security/keys/crypto_request.c
diff --git a/Documentation/security/keys-crypto.txt b/Documentation/security/keys-crypto.txt
index 236d750..e1c19ea 100644
--- a/Documentation/security/keys-crypto.txt
+++ b/Documentation/security/keys-crypto.txt
@@ -158,6 +158,18 @@ using a key to provide the public key:
not necessary if verify_sig_end() was called.
+To find a key to use for signature verification, the following function may be
+called:
+
+ struct key *request_crypto_key_for_PGP_sig(struct key *keyring,
+ const u8 *sig, size_t siglen);
+
+This parses the specified signature blob to find the signing key identity and
+then searches the given keyring for a matching key. It may also examine a
+hardware keystore (such as a TPM) for a usable signature matching service and
+generate a key to provide an access method to that service.
+
+
============================
IMPLEMENTING CRYPTO SUBTYPES
============================
diff --git a/include/keys/crypto-type.h b/include/keys/crypto-type.h
index 6b93366..142611b 100644
--- a/include/keys/crypto-type.h
+++ b/include/keys/crypto-type.h
@@ -31,4 +31,7 @@ extern void verify_sig_cancel(struct crypto_key_verify_context *ctx);
* The payload is at the discretion of the subtype.
*/
+extern struct key *request_crypto_key_for_PGP_sig(struct key *keyring,
+ const u8 *sig, size_t siglen);
+
#endif /* _KEYS_CRYPTO_TYPE_H */
diff --git a/security/keys/Makefile b/security/keys/Makefile
index 78a3aa6..722be34 100644
--- a/security/keys/Makefile
+++ b/security/keys/Makefile
@@ -22,6 +22,6 @@ obj-$(CONFIG_KEYS_COMPAT) += compat.o
obj-$(CONFIG_PROC_FS) += proc.o
obj-$(CONFIG_SYSCTL) += sysctl.o
-crypto_keys-y := crypto_type.o pgp_parse.o crypto_verify.o
+crypto_keys-y := crypto_type.o pgp_parse.o crypto_verify.o crypto_request.o
crypto_dsa-y := crypto_dsa_subtype.o crypto_dsa_verify.o
crypto_rsa-y := crypto_rsa_subtype.o crypto_rsa_verify.o
diff --git a/security/keys/crypto_request.c b/security/keys/crypto_request.c
new file mode 100644
index 0000000..0a1819a3
--- /dev/null
+++ b/security/keys/crypto_request.c
@@ -0,0 +1,87 @@
+/* Cryptographic key request handling
+ *
+ * Copyright (C) 2011 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@xxxxxxxxxx)
+ *
+ * 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.
+ *
+ * See Documentation/security/keys-crypto.txt
+ */
+
+#include <keys/crypto-subtype.h>
+#include <linux/seq_file.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/pgp.h>
+#include "crypto_keys.h"
+
+struct PGP_sig_parse_context {
+ struct pgp_parse_context pgp;
+ struct pgp_sig_parameters params;
+ bool found_sig;
+};
+
+/*
+ * Look inside signature sections for a key ID
+ */
+static int PGP_sig_parse_signature(struct pgp_parse_context *context,
+ enum pgp_packet_tag type,
+ u8 headerlen,
+ const u8 *data,
+ size_t datalen)
+{
+ struct PGP_sig_parse_context *ctx =
+ container_of(context, struct PGP_sig_parse_context, pgp);
+
+ ctx->found_sig = true;
+ return pgp_parse_sig_params(&data, &datalen, &ctx->params);
+}
+
+/**
+ * request_crypto_key_for_PGP_sig - Request a key matching a PGP signature
+ * @keyring: The keyring that might contain the key.
+ * @sig: The PGP signature blob.
+ * @siglen: The size of the PGP signature blob.
+ *
+ * Attempt to find a key to use for PGP signature verification, starting off by
+ * looking in the supplied keyring. The function may also look for other key
+ * sources such as a TPM. If an alternative key is found it will be added to
+ * the keyring for future reference.
+ */
+struct key *request_crypto_key_for_PGP_sig(struct key *keyring,
+ const u8 *sig, size_t siglen)
+{
+ struct PGP_sig_parse_context p;
+ key_ref_t key;
+ char criterion[3 + 8 * 2 + 1];
+ int ret;
+
+ if (!keyring)
+ return ERR_PTR(-ENOKEY);
+
+ /* Need to find the key ID */
+ p.pgp.types_of_interest = (1 << PGP_PKT_SIGNATURE);
+ p.pgp.process_packet = PGP_sig_parse_signature;
+ p.found_sig = false;
+ ret = pgp_parse_packets(sig, siglen, &p.pgp);
+ if (ret < 0)
+ return ERR_PTR(ret);
+
+ if (!p.found_sig)
+ return ERR_PTR(-EINVAL);
+
+ sprintf(criterion, "id:%08x%08x",
+ be32_to_cpu(p.params.issuer32[0]),
+ be32_to_cpu(p.params.issuer32[1]));
+
+ pr_debug("Look up: %s", criterion);
+
+ key = keyring_search(make_key_ref(keyring, 1),
+ &key_type_crypto, criterion);
+ if (IS_ERR(key))
+ return ERR_CAST(key);
+ return key_ref_to_ptr(key);
+}
--
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