KEYS: Implement asymmetric key type

Create a key type that can be used to represent an asymmetric key type for use
in appropriate cryptographic operations, such as encryption, decryption,
signature generation and signature verification.

The key type is "asymmetric" and can provide access to a variety of
cryptographic algorithms.

Possibly, this would be better as "public_key" - but that has the disadvantage
that "public key" is an overloaded term.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

6 files changed, 193 insertions, 0 deletions

diff --git a/crypto/Kconfig b/crypto/Kconfig
index a323805..1ca0b24 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -1043,5 +1043,6 @@ config CRYPTO_USER_API_SKCIPHER
 	  key cipher algorithms.
 
 source "drivers/crypto/Kconfig"
+source crypto/asymmetric_keys/Kconfig
 
 endif	# if CRYPTO
diff --git a/crypto/Makefile b/crypto/Makefile
index 30f33d6..ced472e 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -96,3 +96,4 @@ obj-$(CONFIG_CRYPTO_USER_API_SKCIPHER) += algif_skcipher.o
 #
 obj-$(CONFIG_XOR_BLOCKS) += xor.o
 obj-$(CONFIG_ASYNC_CORE) += async_tx/
+obj-$(CONFIG_ASYMMETRIC_KEY_TYPE) += asymmetric_keys/
diff --git a/crypto/asymmetric_keys/Kconfig b/crypto/asymmetric_keys/Kconfig
new file mode 100644
index 0000000..cad29b3
--- /dev/null
+++ b/crypto/asymmetric_keys/Kconfig
@@ -0,0 +1,13 @@
+menuconfig ASYMMETRIC_KEY_TYPE
+	tristate "Asymmetric (public-key cryptographic) key type"
+	depends on KEYS
+	help
+	  This option provides support for a key type that holds the data for
+	  the asymmetric keys used for public key cryptographic operations such
+	  as encryption, decryption, signature generation and signature
+	  verification.
+
+if ASYMMETRIC_KEY_TYPE
+
+
+endif # ASYMMETRIC_KEY_TYPE
diff --git a/crypto/asymmetric_keys/Makefile b/crypto/asymmetric_keys/Makefile
new file mode 100644
index 0000000..b725bcc
--- /dev/null
+++ b/crypto/asymmetric_keys/Makefile
@@ -0,0 +1,7 @@
+#
+# Makefile for asymmetric cryptographic keys
+#
+
+obj-$(CONFIG_ASYMMETRIC_KEY_TYPE) += asymmetric_keys.o
+
+asymmetric_keys-y := asymmetric_type.o
diff --git a/crypto/asymmetric_keys/asymmetric_keys.h b/crypto/asymmetric_keys/asymmetric_keys.h
new file mode 100644
index 0000000..515b634
--- /dev/null
+++ b/crypto/asymmetric_keys/asymmetric_keys.h
@@ -0,0 +1,15 @@
+/* Internal definitions for asymmetric key type
+ *
+ * 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.
+ */
+
+static inline const char *asymmetric_key_id(const struct key *key)
+{
+	return key->type_data.p[1];
+}
diff --git a/crypto/asymmetric_keys/asymmetric_type.c b/crypto/asymmetric_keys/asymmetric_type.c
new file mode 100644
index 0000000..bfb0424
--- /dev/null
+++ b/crypto/asymmetric_keys/asymmetric_type.c
@@ -0,0 +1,156 @@
+/* Asymmetric public-key cryptography key type
+ *
+ * See Documentation/security/asymmetric-keys.txt
+ *
+ * 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.
+ */
+#include <keys/asymmetric-subtype.h>
+#include <linux/seq_file.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include "asymmetric_keys.h"
+
+MODULE_LICENSE("GPL");
+
+/*
+ * Match asymmetric keys on (part of) their name
+ * We have some shorthand methods for matching keys.  We allow:
+ *
+ *	"<desc>"	- request a key by description
+ *	"id:<id>"	- request a key matching the ID
+ *	"<subtype>:<id>" - request a key of a subtype
+ */
+static int asymmetric_key_match(const struct key *key, const void *description)
+{
+	const struct asymmetric_key_subtype *subtype = asymmetric_key_subtype(key);
+	const char *spec = description;
+	const char *id, *kid;
+	ptrdiff_t speclen;
+	size_t idlen, kidlen;
+
+	if (!subtype || !spec || !*spec)
+		return 0;
+
+	/* See if the full key description matches as is */
+	if (key->description && strcmp(key->description, description) == 0)
+		return 1;
+
+	/* All tests from here on break the criterion description into a
+	 * specifier, a colon and then an identifier.
+	 */
+	id = strchr(spec, ':');
+	if (!id)
+		return 0;
+
+	speclen = id - spec;
+	id++;
+
+	/* Anything after here requires a partial match on the ID string */
+	kid = asymmetric_key_id(key);
+	if (!kid)
+		return 0;
+
+	idlen = strlen(id);
+	kidlen = strlen(kid);
+	if (idlen > kidlen)
+		return 0;
+
+	kid += kidlen - idlen;
+	if (strcasecmp(id, kid) != 0)
+		return 0;
+
+	if (speclen == 2 &&
+	    memcmp(spec, "id", 2) == 0)
+		return 1;
+
+	if (speclen == subtype->name_len &&
+	    memcmp(spec, subtype->name, speclen) == 0)
+		return 1;
+
+	return 0;
+}
+
+/*
+ * Describe the asymmetric key
+ */
+static void asymmetric_key_describe(const struct key *key, struct seq_file *m)
+{
+	const struct asymmetric_key_subtype *subtype = asymmetric_key_subtype(key);
+	const char *kid = asymmetric_key_id(key);
+	size_t n;
+
+	seq_puts(m, key->description);
+
+	if (subtype) {
+		seq_puts(m, ": ");
+		subtype->describe(key, m);
+
+		if (kid) {
+			seq_putc(m, ' ');
+			n = strlen(kid);
+			if (n <= 8)
+				seq_puts(m, kid);
+			else
+				seq_puts(m, kid + n - 8);
+		}
+
+		seq_puts(m, " [");
+		/* put something here to indicate the key's capabilities */
+		seq_putc(m, ']');
+	}
+}
+
+/*
+ * Instantiate a asymmetric_key defined key.  The key was preparsed, so we just
+ * have to transfer the data here.
+ */
+static int asymmetric_key_instantiate(struct key *key, struct key_preparsed_payload *prep)
+{
+	return -EOPNOTSUPP;
+}
+
+/*
+ * dispose of the data dangling from the corpse of a asymmetric key
+ */
+static void asymmetric_key_destroy(struct key *key)
+{
+	struct asymmetric_key_subtype *subtype = asymmetric_key_subtype(key);
+	if (subtype) {
+		subtype->destroy(key->payload.data);
+		module_put(subtype->owner);
+		key->type_data.p[0] = NULL;
+	}
+	kfree(key->type_data.p[1]);
+	key->type_data.p[1] = NULL;
+}
+
+struct key_type key_type_asymmetric = {
+	.name		= "asymmetric",
+	.instantiate	= asymmetric_key_instantiate,
+	.match		= asymmetric_key_match,
+	.destroy	= asymmetric_key_destroy,
+	.describe	= asymmetric_key_describe,
+};
+EXPORT_SYMBOL_GPL(key_type_asymmetric);
+
+/*
+ * Module stuff
+ */
+static int __init asymmetric_key_init(void)
+{
+	return register_key_type(&key_type_asymmetric);
+}
+
+static void __exit asymmetric_key_cleanup(void)
+{
+	unregister_key_type(&key_type_asymmetric);
+}
+
+module_init(asymmetric_key_init);
+module_exit(asymmetric_key_cleanup);