KEYS: Asymmetric public-key algorithm crypto key subtype

Add a subtype for supporting asymmetric public-key encryption algorithms such
as DSA (FIPS-186) and RSA (PKCS#1 / RFC1337).

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

4 files changed, 146 insertions, 0 deletions

diff --git a/crypto/asymmetric_keys/Kconfig b/crypto/asymmetric_keys/Kconfig
index cad29b3efa0e..bbfccaa35293 100644
--- a/crypto/asymmetric_keys/Kconfig
+++ b/crypto/asymmetric_keys/Kconfig
@@ -9,5 +9,13 @@ menuconfig ASYMMETRIC_KEY_TYPE
 
 if ASYMMETRIC_KEY_TYPE
 
+config ASYMMETRIC_PUBLIC_KEY_SUBTYPE
+        tristate "Asymmetric public-key crypto algorithm subtype"
+        select MPILIB
+        help
+          This option provides support for asymmetric public key type handling.
+          If signature generation and/or verification are to be used,
+          appropriate hash algorithms (such as SHA-1) must be available.
+          ENOPKG will be reported if the requisite algorithm is unavailable.
 
 endif # ASYMMETRIC_KEY_TYPE
diff --git a/crypto/asymmetric_keys/Makefile b/crypto/asymmetric_keys/Makefile
index b725bcce4cfd..5ed46eecb299 100644
--- a/crypto/asymmetric_keys/Makefile
+++ b/crypto/asymmetric_keys/Makefile
@@ -5,3 +5,5 @@
 obj-$(CONFIG_ASYMMETRIC_KEY_TYPE) += asymmetric_keys.o
 
 asymmetric_keys-y := asymmetric_type.o
+
+obj-$(CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE) += public_key.o
diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c
new file mode 100644
index 000000000000..cb2e29180a87
--- /dev/null
+++ b/crypto/asymmetric_keys/public_key.c
@@ -0,0 +1,108 @@
+/* In-software asymmetric public-key crypto subtype
+ *
+ * See Documentation/crypto/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.
+ */
+
+#define pr_fmt(fmt) "PKEY: "fmt
+#include <linux/module.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/seq_file.h>
+#include <keys/asymmetric-subtype.h>
+#include "public_key.h"
+
+MODULE_LICENSE("GPL");
+
+const char *const pkey_algo[PKEY_ALGO__LAST] = {
+        [PKEY_ALGO_DSA]         = "DSA",
+        [PKEY_ALGO_RSA]         = "RSA",
+};
+EXPORT_SYMBOL_GPL(pkey_algo);
+
+const char *const pkey_hash_algo[PKEY_HASH__LAST] = {
+        [PKEY_HASH_MD4]         = "md4",
+        [PKEY_HASH_MD5]         = "md5",
+        [PKEY_HASH_SHA1]        = "sha1",
+        [PKEY_HASH_RIPE_MD_160] = "rmd160",
+        [PKEY_HASH_SHA256]      = "sha256",
+        [PKEY_HASH_SHA384]      = "sha384",
+        [PKEY_HASH_SHA512]      = "sha512",
+        [PKEY_HASH_SHA224]      = "sha224",
+};
+EXPORT_SYMBOL_GPL(pkey_hash_algo);
+
+const char *const pkey_id_type[PKEY_ID_TYPE__LAST] = {
+        [PKEY_ID_PGP]           = "PGP",
+        [PKEY_ID_X509]          = "X509",
+};
+EXPORT_SYMBOL_GPL(pkey_id_type);
+
+/*
+ * Provide a part of a description of the key for /proc/keys.
+ */
+static void public_key_describe(const struct key *asymmetric_key,
+                                struct seq_file *m)
+{
+        struct public_key *key = asymmetric_key->payload.data;
+
+        if (key)
+                seq_printf(m, "%s.%s",
+                           pkey_id_type[key->id_type], key->algo->name);
+}
+
+/*
+ * Destroy a public key algorithm key.
+ */
+void public_key_destroy(void *payload)
+{
+        struct public_key *key = payload;
+        int i;
+
+        if (key) {
+                for (i = 0; i < ARRAY_SIZE(key->mpi); i++)
+                        mpi_free(key->mpi[i]);
+                kfree(key);
+        }
+}
+EXPORT_SYMBOL_GPL(public_key_destroy);
+
+/*
+ * Verify a signature using a public key.
+ */
+static int public_key_verify_signature(const struct key *key,
+                                       const struct public_key_signature *sig)
+{
+        const struct public_key *pk = key->payload.data;
+
+        if (!pk->algo->verify_signature)
+                return -ENOTSUPP;
+
+        if (sig->nr_mpi != pk->algo->n_sig_mpi) {
+                pr_debug("Signature has %u MPI not %u\n",
+                         sig->nr_mpi, pk->algo->n_sig_mpi);
+                return -EINVAL;
+        }
+
+        return pk->algo->verify_signature(pk, sig);
+}
+
+/*
+ * Public key algorithm asymmetric key subtype
+ */
+struct asymmetric_key_subtype public_key_subtype = {
+        .owner                  = THIS_MODULE,
+        .name                   = "public_key",
+        .describe               = public_key_describe,
+        .destroy                = public_key_destroy,
+        .verify_signature       = public_key_verify_signature,
+};
+EXPORT_SYMBOL_GPL(public_key_subtype);
diff --git a/crypto/asymmetric_keys/public_key.h b/crypto/asymmetric_keys/public_key.h
new file mode 100644
index 000000000000..1f86aad31003
--- /dev/null
+++ b/crypto/asymmetric_keys/public_key.h
@@ -0,0 +1,28 @@
+/* Public key algorithm internals
+ *
+ * See Documentation/crypto/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 <crypto/public_key.h>
+
+extern struct asymmetric_key_subtype public_key_subtype;
+
+/*
+ * Public key algorithm definition.
+ */
+struct public_key_algorithm {
+        const char      *name;
+        u8              n_pub_mpi;      /* Number of MPIs in public key */
+        u8              n_sec_mpi;      /* Number of MPIs in secret key */
+        u8              n_sig_mpi;      /* Number of MPIs in a signature */
+        int (*verify_signature)(const struct public_key *key,
+                                const struct public_key_signature *sig);
+};