[PATCH 07/21] KEYS: Create a key type that can be used for general cryptographic operations [ver #3]

[David Howells <dhowells@redhat.com>]

Create a key type that can be used for general cryptographic operations, such
as encryption, decryption, signature generation and signature verification.

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

Signed-off-by: David Howells <dhowells@redhat.com>
---

 Documentation/security/keys-crypto.txt |  181 +++++++++++++++++++++++++
 include/keys/crypto-subtype.h          |   56 ++++++++
 include/keys/crypto-type.h             |   25 +++
 security/keys/Kconfig                  |    8 +
 security/keys/Makefile                 |    3 
 security/keys/crypto_keys.h            |   28 ++++
 security/keys/crypto_type.c            |  230 ++++++++++++++++++++++++++++++++
 7 files changed, 531 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/security/keys-crypto.txt
 create mode 100644 include/keys/crypto-subtype.h
 create mode 100644 include/keys/crypto-type.h
 create mode 100644 security/keys/crypto_keys.h
 create mode 100644 security/keys/crypto_type.c


diff --git a/Documentation/security/keys-crypto.txt b/Documentation/security/keys-crypto.txt
new file mode 100644
index 0000000..97dee80
--- /dev/null
+++ b/Documentation/security/keys-crypto.txt
@@ -0,0 +1,181 @@
+			    ======================
+			    CRYPTOGRAPHIC KEY TYPE
+			    ======================
+
+Contents:
+
+  - Overview.
+  - Key identification.
+  - Accessing crypto keys.
+  - Implementing crypto parsers.
+  - Implementing crypto subtypes.
+
+
+========
+OVERVIEW
+========
+
+The "crypto" key type is designed to be a container for cryptographic keys,
+without imposing any particular restrictions on the form of the cryptography or
+the key.
+
+The crypto key is given a subtype that defines what sort of data is associated
+with the key and provides operations to describe and destroy it.  However, no
+requirement is made that the key data actually be loaded into the key.
+
+The crypto key also has a number of data parsers registered with it.  The data
+parsers are responsible for extracing information the blobs of data passed to
+the instantiator function.  The first data parser that recognises the blob gets
+to set the subtype of the key and define the operations that can be done on
+that key.
+
+Completely in-kernel key retention and operation subtypes and parsers can be
+defined, but it would also be possible to provide access to cryptographic
+hardware (such as a TPM) that might be used to both retain the relevant key and
+perform operations using that key.  In such a case, the crypto key would then
+merely be an interface to the TPM driver.
+
+
+==================
+KEY IDENTIFICATION
+==================
+
+Because the identity of a key is not necessarily known and may not be easily
+calculated when a crypto key is allocated, it may not be a simple matter to set
+a key description to something that's useful for determining whether this is
+the key you're looking for.  Furthermore, it may be necessary to perform a
+partial match upon the key identity.
+
+To help with this, when a key is loaded, the parser calculates the key
+fingerprint and stores a copy in the key structure.
+
+The crypto key type's key matching function then performs more checks than just
+the straightforward comparison of the description with the criterion string:
+
+ (1) If the criterion string is of the form "id:<hexdigits>" then the match
+     function will examine a key's fingerprint to see if the hex digits given
+     after the "id:" match the tail.  For instance:
+
+	keyctl search @s crypto id:5acc2142
+
+     will match a key with fingerprint:
+
+	1A00 2040 7601 7889 DE11  882C 3823 04AD 5ACC 2142
+
+ (2) If the criterion string is of the form "<subtype>:<hexdigits>" then the
+     match will match the ID as in (1), but with the added restriction that
+     only keys of the specified subtype (e.g. dsa or rsa) will be matched.  For
+     instance:
+
+	keyctl search @s crypto dsa:5acc2142
+
+Looking in /proc/keys, the last 8 hex digits of the key fingerprint are
+displayed, along with the subtype:
+
+	1a39e171 I-----     1 perm 3f010000     0     0 crypto    modsign.0: DSA 5acc2142 []
+
+
+=====================
+ACCESSING CRYPTO KEYS
+=====================
+
+To access crypto keys from within the kernel, the following inclusion is
+required:
+
+	#include <keys/crypto-type.h>
+
+This gives access to the key type:
+
+	struct key_type key_type_crypto;
+
+
+===========================
+IMPLEMENTING CRYPTO PARSERS
+===========================
+
+The crypto key type keeps a list of registered data parsers.  An example of
+such a parser is one that parses OpenPGP packet formatted data [RFC 4880].
+
+During key instantiation each parser in the list is tried until one doesn't
+return -EBADMSG.
+
+The parser definition structure looks like the following:
+
+	struct crypto_key_parser {
+		struct module		*owner;
+		const char		*name;
+
+		int (*instantiate)(struct key *key,
+				   const void *data, size_t datalen);
+	};
+
+The owner and name fields should be set to the owning module and the name of
+the parser.
+
+There are a number of operations defined by the parser.  They are all optional,
+but it is expected that at least one will be defined.
+
+ (1) instantiate().
+
+     The arguments are the same as for the instantiate function in the key
+     type.  'key' is the crypto key being instantiated; data and datalen are
+     the instantiation data, presumably containing cryptographic key data, and
+     the length of that data.
+
+     If the data format is not recognised, -EBADMSG should be returned.  If it
+     is recognised, but the key cannot for some reason be set up, some other
+     negative error code should be returned.
+
+     If the key can be successfully set up, then key->payload should be set to
+     point to the retained data, key->type_data.p[0] should be set to point to
+     the subtype chosen and key->type_data.p[1] should be set to point to a
+     copy of the key's identity string and 0 should be returned.
+
+     The key's identity string may be partially matched upon.  For a public-key
+     algorithm such as RSA and DSA this will likely be a printable hex version
+     of the key's fingerprint.
+
+Functions are provided to register and unregister parsers:
+
+	int register_crypto_key_parser(struct crypto_key_parser *parser);
+	void unregister_crypto_key_parser(struct crypto_key_parser *subtype);
+
+Parsers may not have the same name.  The names are only used for displaying in
+debugging messages.
+
+
+============================
+IMPLEMENTING CRYPTO SUBTYPES
+============================
+
+The parser selects the appropriate subtype directly and sets it on the key; the
+crypto key then retains a reference on the subtype module (which means the
+parser can be removed thereafter).
+
+The subtype definition structure looks like the following:
+
+	struct crypto_key_subtype {
+		struct module		*owner;
+		const char		*name;
+
+		void (*describe)(const struct key *key, struct seq_file *m);
+		void (*destroy)(void *payload);
+	};
+
+The owner and name fields should be set to the owning module and the name of
+the subtype.
+
+There are a number of operations defined by the subtype:
+
+ (1) describe().
+
+     Mandatory.  This allows the subtype to display something in /proc/keys
+     against the key.  For instance the name of the public key algorithm type
+     could be displayed.  The key type will display the tail of the key
+     identity string after this.
+
+ (2) destroy().
+
+     Mandatory.  This should free the memory associated with the key.  The
+     crypto key will look after freeing the fingerprint and releasing the
+     reference on the subtype module.
diff --git a/include/keys/crypto-subtype.h b/include/keys/crypto-subtype.h
new file mode 100644
index 0000000..fa87555
--- /dev/null
+++ b/include/keys/crypto-subtype.h
@@ -0,0 +1,56 @@
+/* Cryptographic key subtype
+ *
+ * Copyright (C) 2011 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.
+ *
+ * See Documentation/security/keys-crypto.txt
+ */
+
+#ifndef _KEYS_CRYPTO_SUBTYPE_H
+#define _KEYS_CRYPTO_SUBTYPE_H
+
+#include <linux/seq_file.h>
+#include <keys/crypto-type.h>
+
+extern struct key_type key_type_crypto;
+
+/*
+ * Keys of this type declare a subtype that indicates the handlers and
+ * capabilities.
+ */
+struct crypto_key_subtype {
+	struct module		*owner;
+	const char		*name;
+	unsigned short		name_len;	/* length of name */
+
+	void (*describe)(const struct key *key, struct seq_file *m);
+
+	void (*destroy)(void *payload);
+};
+
+/*
+ * Data parser.  Called during instantiation and signature verification
+ * initiation.
+ */
+struct crypto_key_parser {
+	struct list_head	link;
+	struct module		*owner;
+	const char		*name;
+
+	/* Attempt to instantiate a key from the data blob passed to add_key()
+	 * or keyctl_instantiate().
+	 *
+	 * Return EBADMSG if not recognised.
+	 */
+	int (*instantiate)(struct key *key, const void *data, size_t datalen);
+};
+
+extern int register_crypto_key_parser(struct crypto_key_parser *);
+extern void unregister_crypto_key_parser(struct crypto_key_parser *);
+
+#endif /* _KEYS_CRYPTO_SUBTYPE_H */
diff --git a/include/keys/crypto-type.h b/include/keys/crypto-type.h
new file mode 100644
index 0000000..47c00c7
--- /dev/null
+++ b/include/keys/crypto-type.h
@@ -0,0 +1,25 @@
+/* Cryptographic key type interface
+ *
+ * Copyright (C) 2011 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.
+ *
+ * See Documentation/security/keys-crypto.txt
+ */
+
+#ifndef _KEYS_CRYPTO_TYPE_H
+#define _KEYS_CRYPTO_TYPE_H
+
+#include <linux/key-type.h>
+
+extern struct key_type key_type_crypto;
+
+/*
+ * The payload is at the discretion of the subtype.
+ */
+
+#endif /* _KEYS_CRYPTO_TYPE_H */
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index a90d6d3..290c9d3 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -69,3 +69,11 @@ config KEYS_DEBUG_PROC_KEYS
 	  the resulting table.
 
 	  If you are unsure as to whether this is required, answer N.
+
+config CRYPTO_KEY_TYPE
+	tristate "Cryptographic key type"
+	depends on KEYS
+	help
+	  This option provides support for a type of key that holds the keys
+	  required for cryptographic operations such as encryption, decryption,
+	  signature generation and signature verification.
diff --git a/security/keys/Makefile b/security/keys/Makefile
index 504aaa0..67fceaa 100644
--- a/security/keys/Makefile
+++ b/security/keys/Makefile
@@ -24,3 +24,6 @@ obj-$(CONFIG_SYSCTL) += sysctl.o
 #
 obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
 obj-$(CONFIG_ENCRYPTED_KEYS) += encrypted-keys/
+obj-$(CONFIG_CRYPTO_KEY_TYPE) += crypto_keys.o
+
+crypto_keys-y := crypto_type.o
diff --git a/security/keys/crypto_keys.h b/security/keys/crypto_keys.h
new file mode 100644
index 0000000..a339ce0
--- /dev/null
+++ b/security/keys/crypto_keys.h
@@ -0,0 +1,28 @@
+/* Internal crypto type stuff
+ *
+ * Copyright (C) 2011 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
+struct crypto_key_subtype *crypto_key_subtype(const struct key *key)
+{
+	return key->type_data.p[0];
+}
+
+static inline char *crypto_key_id(const struct key *key)
+{
+	return key->type_data.p[1];
+}
+
+
+/*
+ * crypto_type.c
+ */
+extern struct list_head crypto_key_parsers;
+extern struct rw_semaphore crypto_key_parsers_sem;
diff --git a/security/keys/crypto_type.c b/security/keys/crypto_type.c
new file mode 100644
index 0000000..a06413a
--- /dev/null
+++ b/security/keys/crypto_type.c
@@ -0,0 +1,230 @@
+/* Cryptographic key type
+ *
+ * Copyright (C) 2011 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.
+ *
+ * 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 "crypto_keys.h"
+
+MODULE_LICENSE("GPL");
+
+LIST_HEAD(crypto_key_parsers);
+DECLARE_RWSEM(crypto_key_parsers_sem);
+
+/*
+ * Match crypto_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 crypto_key_match(const struct key *key, const void *description)
+{
+	const struct crypto_key_subtype *subtype = crypto_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 = crypto_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 crypto key
+ */
+static void crypto_key_describe(const struct key *key, struct seq_file *m)
+{
+	const struct crypto_key_subtype *subtype = crypto_key_subtype(key);
+	const char *kid = crypto_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 crypto_key defined key
+ */
+static int crypto_key_instantiate(struct key *key,
+				  const void *data, size_t datalen)
+{
+	struct crypto_key_parser *parser;
+	int ret;
+
+	pr_devel("==>%s()\n", __func__);
+
+	if (datalen == 0)
+		return -EINVAL;
+
+	down_read(&crypto_key_parsers_sem);
+
+	ret = -EBADMSG;
+	list_for_each_entry(parser, &crypto_key_parsers, link) {
+		pr_debug("Trying parser '%s'\n", parser->name);
+
+		ret = parser->instantiate(key, data, datalen);
+		if (ret != -EBADMSG) {
+			pr_debug("Parser recognised the format (ret %d)\n",
+				 ret);
+			if (ret == 0)
+				module_get(crypto_key_subtype(key));
+			break;
+		}
+	}
+
+	up_read(&crypto_key_parsers_sem);
+	pr_devel("<==%s() = %d\n", __func__, ret);
+	return ret;
+}
+
+/*
+ * dispose of the data dangling from the corpse of a crypto key
+ */
+static void crypto_key_destroy(struct key *key)
+{
+	struct crypto_key_subtype *subtype = crypto_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_crypto = {
+	.name		= "crypto",
+	.instantiate	= crypto_key_instantiate,
+	.match		= crypto_key_match,
+	.destroy	= crypto_key_destroy,
+	.describe	= crypto_key_describe,
+};
+EXPORT_SYMBOL_GPL(key_type_crypto);
+
+/**
+ * register_crypto_key_parser - Register a crypto key blob parser
+ * @parser: The parser to register
+ */
+int register_crypto_key_parser(struct crypto_key_parser *parser)
+{
+	struct crypto_key_parser *cursor;
+	int ret;
+
+	down_write(&crypto_key_parsers_sem);
+
+	list_for_each_entry(cursor, &crypto_key_parsers, link) {
+		if (strcmp(cursor->name, parser->name) == 0) {
+			pr_err("Crypto key parser '%s' already registered\n",
+			       parser->name);
+			ret = -EEXIST;
+			goto out;
+		}
+	}
+
+	list_add_tail(&parser->link, &crypto_key_parsers);
+
+	pr_notice("Crypto key parser '%s' registered\n", parser->name);
+	ret = 0;
+
+out:
+	up_write(&crypto_key_parsers_sem);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(register_crypto_key_parser);
+
+/**
+ * unregister_crypto_key_parser - Unregister a crypto key blob parser
+ * @parser: The parser to unregister
+ */
+void unregister_crypto_key_parser(struct crypto_key_parser *parser)
+{
+	down_write(&crypto_key_parsers_sem);
+	list_del(&parser->link);
+	up_write(&crypto_key_parsers_sem);
+
+	pr_notice("Crypto key parser '%s' unregistered\n", parser->name);
+}
+EXPORT_SYMBOL_GPL(unregister_crypto_key_parser);
+
+/*
+ * Module stuff
+ */
+static int __init crypto_key_init(void)
+{
+	return register_key_type(&key_type_crypto);
+}
+
+static void __exit crypto_key_cleanup(void)
+{
+	unregister_key_type(&key_type_crypto);
+}
+
+module_init(crypto_key_init);
+module_exit(crypto_key_cleanup);