KEYS: Implement PKCS#8 RSA Private Key parser [ver #2]

Implement PKCS#8 RSA Private Key format [RFC 5208] parser for the
asymmetric key type.  For the moment, this will only support unencrypted
DER blobs.  PEM and decryption can be added later.

PKCS#8 keys can be loaded like this:

	openssl pkcs8 -in private_key.pem -topk8 -nocrypt -outform DER | \
	  keyctl padd asymmetric foo @s

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Marcel Holtmann <marcel@holtmann.org>
Reviewed-by: Marcel Holtmann <marcel@holtmann.org>
Reviewed-by: Denis Kenzior <denkenz@gmail.com>
Tested-by: Denis Kenzior <denkenz@gmail.com>
Signed-off-by: James Morris <james.morris@microsoft.com>

5 files changed, 233 insertions, 0 deletions

diff --git a/Documentation/crypto/asymmetric-keys.txt b/Documentation/crypto/asymmetric-keys.txt
index deb656ef008b..8763866b11cf 100644
--- a/Documentation/crypto/asymmetric-keys.txt
+++ b/Documentation/crypto/asymmetric-keys.txt
@@ -248,6 +248,8 @@ Examples of blob formats for which parsers could be implemented include:
  - X.509 ASN.1 stream.
  - Pointer to TPM key.
  - Pointer to UEFI key.
+ - PKCS#8 private key [RFC 5208].
+ - PKCS#5 encrypted private key [RFC 2898].
 
 During key instantiation each parser in the list is tried until one doesn't
 return -EBADMSG.
diff --git a/crypto/asymmetric_keys/Kconfig b/crypto/asymmetric_keys/Kconfig
index f3702e533ff4..66a7dad7ed3d 100644
--- a/crypto/asymmetric_keys/Kconfig
+++ b/crypto/asymmetric_keys/Kconfig
@@ -31,6 +31,16 @@ config X509_CERTIFICATE_PARSER
           data and provides the ability to instantiate a crypto key from a
           public key packet found inside the certificate.
 
+config PKCS8_PRIVATE_KEY_PARSER
+        tristate "PKCS#8 private key parser"
+        depends on ASYMMETRIC_PUBLIC_KEY_SUBTYPE
+        select ASN1
+        select OID_REGISTRY
+        help
+          This option provides support for parsing PKCS#8 format blobs for
+          private key data and provides the ability to instantiate a crypto key
+          from that data.
+
 config PKCS7_MESSAGE_PARSER
         tristate "PKCS#7 message parser"
         depends on X509_CERTIFICATE_PARSER
diff --git a/crypto/asymmetric_keys/Makefile b/crypto/asymmetric_keys/Makefile
index d4b2e1b2dc65..c38424f55b08 100644
--- a/crypto/asymmetric_keys/Makefile
+++ b/crypto/asymmetric_keys/Makefile
@@ -30,6 +30,19 @@ $(obj)/x509.asn1.o: $(obj)/x509.asn1.c $(obj)/x509.asn1.h
 $(obj)/x509_akid.asn1.o: $(obj)/x509_akid.asn1.c $(obj)/x509_akid.asn1.h
 
 #
+# PKCS#8 private key handling
+#
+obj-$(CONFIG_PKCS8_PRIVATE_KEY_PARSER) += pkcs8_key_parser.o
+pkcs8_key_parser-y := \
+        pkcs8.asn1.o \
+        pkcs8_parser.o
+
+$(obj)/pkcs8_parser.o: $(obj)/pkcs8.asn1.h
+$(obj)/pkcs8-asn1.o: $(obj)/pkcs8.asn1.c $(obj)/pkcs8.asn1.h
+
+clean-files     += pkcs8.asn1.c pkcs8.asn1.h
+
+#
 # PKCS#7 message handling
 #
 obj-$(CONFIG_PKCS7_MESSAGE_PARSER) += pkcs7_message.o
diff --git a/crypto/asymmetric_keys/pkcs8.asn1 b/crypto/asymmetric_keys/pkcs8.asn1
new file mode 100644
index 000000000000..702c41a3c713
--- /dev/null
+++ b/crypto/asymmetric_keys/pkcs8.asn1
@@ -0,0 +1,24 @@
+--
+-- This is the unencrypted variant
+--
+PrivateKeyInfo ::= SEQUENCE {
+        version                 Version,
+        privateKeyAlgorithm     PrivateKeyAlgorithmIdentifier,
+        privateKey              PrivateKey,
+        attributes              [0] IMPLICIT Attributes OPTIONAL
+}
+
+Version ::= INTEGER  ({ pkcs8_note_version })
+
+PrivateKeyAlgorithmIdentifier ::= AlgorithmIdentifier ({ pkcs8_note_algo })
+
+PrivateKey ::= OCTET STRING ({ pkcs8_note_key })
+
+Attributes ::= SET OF Attribute
+
+Attribute ::= ANY
+
+AlgorithmIdentifier ::= SEQUENCE {
+        algorithm   OBJECT IDENTIFIER ({ pkcs8_note_OID }),
+        parameters  ANY OPTIONAL
+}
diff --git a/crypto/asymmetric_keys/pkcs8_parser.c b/crypto/asymmetric_keys/pkcs8_parser.c
new file mode 100644
index 000000000000..5f6a7ecc9765
--- /dev/null
+++ b/crypto/asymmetric_keys/pkcs8_parser.c
@@ -0,0 +1,184 @@
+/* PKCS#8 Private Key parser [RFC 5208].
+ *
+ * Copyright (C) 2016 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) "PKCS8: "fmt
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/oid_registry.h>
+#include <keys/asymmetric-subtype.h>
+#include <keys/asymmetric-parser.h>
+#include <crypto/public_key.h>
+#include "pkcs8.asn1.h"
+
+struct pkcs8_parse_context {
+        struct public_key *pub;
+        unsigned long   data;                   /* Start of data */
+        enum OID        last_oid;               /* Last OID encountered */
+        enum OID        algo_oid;               /* Algorithm OID */
+        u32             key_size;
+        const void      *key;
+};
+
+/*
+ * Note an OID when we find one for later processing when we know how to
+ * interpret it.
+ */
+int pkcs8_note_OID(void *context, size_t hdrlen,
+                   unsigned char tag,
+                   const void *value, size_t vlen)
+{
+        struct pkcs8_parse_context *ctx = context;
+
+        ctx->last_oid = look_up_OID(value, vlen);
+        if (ctx->last_oid == OID__NR) {
+                char buffer[50];
+
+                sprint_oid(value, vlen, buffer, sizeof(buffer));
+                pr_info("Unknown OID: [%lu] %s\n",
+                        (unsigned long)value - ctx->data, buffer);
+        }
+        return 0;
+}
+
+/*
+ * Note the version number of the ASN.1 blob.
+ */
+int pkcs8_note_version(void *context, size_t hdrlen,
+                       unsigned char tag,
+                       const void *value, size_t vlen)
+{
+        if (vlen != 1 || ((const u8 *)value)[0] != 0) {
+                pr_warn("Unsupported PKCS#8 version\n");
+                return -EBADMSG;
+        }
+        return 0;
+}
+
+/*
+ * Note the public algorithm.
+ */
+int pkcs8_note_algo(void *context, size_t hdrlen,
+                    unsigned char tag,
+                    const void *value, size_t vlen)
+{
+        struct pkcs8_parse_context *ctx = context;
+
+        if (ctx->last_oid != OID_rsaEncryption)
+                return -ENOPKG;
+
+        ctx->pub->pkey_algo = "rsa";
+        return 0;
+}
+
+/*
+ * Note the key data of the ASN.1 blob.
+ */
+int pkcs8_note_key(void *context, size_t hdrlen,
+                   unsigned char tag,
+                   const void *value, size_t vlen)
+{
+        struct pkcs8_parse_context *ctx = context;
+
+        ctx->key = value;
+        ctx->key_size = vlen;
+        return 0;
+}
+
+/*
+ * Parse a PKCS#8 private key blob.
+ */
+static struct public_key *pkcs8_parse(const void *data, size_t datalen)
+{
+        struct pkcs8_parse_context ctx;
+        struct public_key *pub;
+        long ret;
+
+        memset(&ctx, 0, sizeof(ctx));
+
+        ret = -ENOMEM;
+        ctx.pub = kzalloc(sizeof(struct public_key), GFP_KERNEL);
+        if (!ctx.pub)
+                goto error;
+
+        ctx.data = (unsigned long)data;
+
+        /* Attempt to decode the private key */
+        ret = asn1_ber_decoder(&pkcs8_decoder, &ctx, data, datalen);
+        if (ret < 0)
+                goto error_decode;
+
+        ret = -ENOMEM;
+        pub = ctx.pub;
+        pub->key = kmemdup(ctx.key, ctx.key_size, GFP_KERNEL);
+        if (!pub->key)
+                goto error_decode;
+
+        pub->keylen = ctx.key_size;
+        pub->key_is_private = true;
+        return pub;
+
+error_decode:
+        kfree(ctx.pub);
+error:
+        return ERR_PTR(ret);
+}
+
+/*
+ * Attempt to parse a data blob for a key as a PKCS#8 private key.
+ */
+static int pkcs8_key_preparse(struct key_preparsed_payload *prep)
+{
+        struct public_key *pub;
+
+        pub = pkcs8_parse(prep->data, prep->datalen);
+        if (IS_ERR(pub))
+                return PTR_ERR(pub);
+
+        pr_devel("Cert Key Algo: %s\n", pub->pkey_algo);
+        pub->id_type = "PKCS8";
+
+        /* We're pinning the module by being linked against it */
+        __module_get(public_key_subtype.owner);
+        prep->payload.data[asym_subtype] = &public_key_subtype;
+        prep->payload.data[asym_key_ids] = NULL;
+        prep->payload.data[asym_crypto] = pub;
+        prep->payload.data[asym_auth] = NULL;
+        prep->quotalen = 100;
+        return 0;
+}
+
+static struct asymmetric_key_parser pkcs8_key_parser = {
+        .owner  = THIS_MODULE,
+        .name   = "pkcs8",
+        .parse  = pkcs8_key_preparse,
+};
+
+/*
+ * Module stuff
+ */
+static int __init pkcs8_key_init(void)
+{
+        return register_asymmetric_key_parser(&pkcs8_key_parser);
+}
+
+static void __exit pkcs8_key_exit(void)
+{
+        unregister_asymmetric_key_parser(&pkcs8_key_parser);
+}
+
+module_init(pkcs8_key_init);
+module_exit(pkcs8_key_exit);
+
+MODULE_DESCRIPTION("PKCS#8 certificate parser");
+MODULE_LICENSE("GPL");