[PATCH 13/23] KEYS: PGP data parser

[David Howells]

Implement a PGP data parser for the crypto key type to use when instantiating a
key.

This parser attempts to parse the instantiation data as a PGP packet sequence
(RFC 4880) and if it parses okay, attempts to extract a public-key algorithm
key or subkey from it.

If it finds such a key, it will set up a public_key subtype payload with
appropriate handler routines (DSA or RSA) and attach it to the key.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---

 security/keys/crypto/Kconfig          |   12 +
 security/keys/crypto/Makefile         |    4 
 security/keys/crypto/pgp_key_parser.c |  346 +++++++++++++++++++++++++++++++++
 security/keys/crypto/pgp_parser.h     |   23 ++
 4 files changed, 385 insertions(+), 0 deletions(-)
 create mode 100644 security/keys/crypto/pgp_key_parser.c
 create mode 100644 security/keys/crypto/pgp_parser.h


diff --git a/security/keys/crypto/Kconfig b/security/keys/crypto/Kconfig
index 88ce0e2..1c2ae55 100644
--- a/security/keys/crypto/Kconfig
+++ b/security/keys/crypto/Kconfig
@@ -28,3 +28,15 @@ config PGP_LIBRARY
 	help
 	  This option enables a library that provides a number of simple
 	  utility functions for parsing PGP (RFC 4880) packet-based messages.
+
+config CRYPTO_KEY_PGP_PARSER
+	tristate "PGP key blob parser"
+	depends on CRYPTO_KEY_TYPE
+	select CRYPTO_KEY_PUBLIC_KEY_SUBTYPE
+	select PGP_LIBRARY
+	select MD5 # V3 fingerprint generation
+	select SHA1 # V4 fingerprint generation
+	help
+	  This option provides support for parsing PGP (RFC 4880) format blobs
+	  for key data and provides the ability to instantiate a crypto key
+	  from a public key packet found inside the blob.
diff --git a/security/keys/crypto/Makefile b/security/keys/crypto/Makefile
index 5fbe54e..3bb2e61 100644
--- a/security/keys/crypto/Makefile
+++ b/security/keys/crypto/Makefile
@@ -8,3 +8,7 @@ crypto_keys-y := crypto_type.o crypto_verify.o
 obj-$(CONFIG_CRYPTO_KEY_PUBLIC_KEY_SUBTYPE) += public_key.o
 obj-$(CONFIG_CRYPTO_KEY_PKEY_ALGO_RSA) += crypto_rsa.o
 obj-$(CONFIG_PGP_LIBRARY) += pgp_library.o
+
+obj-$(CONFIG_CRYPTO_KEY_PGP_PARSER) += pgp_parser.o
+pgp_parser-y := \
+	pgp_key_parser.o
diff --git a/security/keys/crypto/pgp_key_parser.c b/security/keys/crypto/pgp_key_parser.c
new file mode 100644
index 0000000..9cfedc2
--- /dev/null
+++ b/security/keys/crypto/pgp_key_parser.c
@@ -0,0 +1,346 @@
+/* Parser for PGP format key data [RFC 4880]
+ *
+ * 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.
+ */
+
+#define pr_fmt(fmt) "PGP: "fmt
+#include <keys/crypto-subtype.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/mpi.h>
+#include <linux/pgp.h>
+#include <crypto/hash.h>
+#include "public_key.h"
+#include "pgp_parser.h"
+
+MODULE_LICENSE("GPL");
+
+const
+struct public_key_algorithm *pgp_public_key_algorithms[PGP_PUBKEY__LAST] = {
+#if defined(CONFIG_CRYPTO_KEY_PKEY_ALGO_RSA) || \
+	defined(CONFIG_CRYPTO_KEY_PKEY_ALGO_RSA_MODULE)
+	[PGP_PUBKEY_RSA_ENC_OR_SIG]	= &RSA_public_key_algorithm,
+	[PGP_PUBKEY_RSA_ENC_ONLY]	= &RSA_public_key_algorithm,
+	[PGP_PUBKEY_RSA_SIG_ONLY]	= &RSA_public_key_algorithm,
+#endif
+	[PGP_PUBKEY_ELGAMAL]		= NULL,
+	[PGP_PUBKEY_DSA]		= NULL,
+};
+
+static const u8 pgp_public_key_capabilities[PGP_PUBKEY__LAST] = {
+	[PGP_PUBKEY_RSA_ENC_OR_SIG]	= PKEY_CAN_ENCDEC | PKEY_CAN_SIGVER,
+	[PGP_PUBKEY_RSA_ENC_ONLY]	= PKEY_CAN_ENCDEC,
+	[PGP_PUBKEY_RSA_SIG_ONLY]	= PKEY_CAN_SIGVER,
+	[PGP_PUBKEY_ELGAMAL]		= 0,
+	[PGP_PUBKEY_DSA]		= 0,
+};
+
+static inline void digest_putc(struct shash_desc *digest, uint8_t ch)
+{
+	crypto_shash_update(digest, &ch, 1);
+}
+
+struct pgp_key_data_parse_context {
+	struct pgp_parse_context pgp;
+	struct crypto_key_subtype *subtype;
+	char *fingerprint;
+	void *payload;
+};
+
+/*
+ * Calculate the public key ID (RFC4880 12.2)
+ */
+static int pgp_calc_pkey_keyid(struct shash_desc *digest,
+			       struct pgp_parse_pubkey *pgp,
+			       struct public_key *key)
+{
+	unsigned nb[ARRAY_SIZE(key->mpi)];
+	unsigned nn[ARRAY_SIZE(key->mpi)];
+	unsigned n;
+	u8 *pp[ARRAY_SIZE(key->mpi)];
+	u32 a32;
+	int npkey = key->algo->n_pub_mpi;
+	int i, ret = -ENOMEM;
+
+	kenter("");
+
+	for (i = 0; i < ARRAY_SIZE(pp); i++)
+		pp[i] = NULL;
+
+	n = (pgp->version < PGP_KEY_VERSION_4) ? 8 : 6;
+	for (i = 0; i < npkey; i++) {
+		nb[i] = mpi_get_nbits(key->mpi[i]);
+		pp[i] = mpi_get_buffer(key->mpi[i], nn + i, NULL);
+		if (!pp[i])
+			goto error;
+		n += 2 + nn[i];
+	}
+
+	digest_putc(digest, 0x99);     /* ctb */
+	digest_putc(digest, n >> 8);   /* 16-bit header length */
+	digest_putc(digest, n);
+	digest_putc(digest, pgp->version);
+
+	a32 = pgp->creation_time;
+	digest_putc(digest, a32 >> 24);
+	digest_putc(digest, a32 >> 16);
+	digest_putc(digest, a32 >>  8);
+	digest_putc(digest, a32 >>  0);
+
+	if (pgp->version < PGP_KEY_VERSION_4) {
+		u16 a16;
+
+		if (pgp->expires_at)
+			a16 = (pgp->expires_at - pgp->creation_time) / 86400UL;
+		else
+			a16 = 0;
+		digest_putc(digest, a16 >> 8);
+		digest_putc(digest, a16 >> 0);
+	}
+
+	digest_putc(digest, pgp->pubkey_algo);
+
+	for (i = 0; i < npkey; i++) {
+		digest_putc(digest, nb[i] >> 8);
+		digest_putc(digest, nb[i]);
+		crypto_shash_update(digest, pp[i], nn[i]);
+	}
+	ret = 0;
+
+error:
+	for (i = 0; i < npkey; i++)
+		kfree(pp[i]);
+	kleave(" = %d", ret);
+	return ret;
+}
+
+/*
+ * Calculate the public key ID fingerprint
+ */
+static int pgp_generate_fingerprint(struct pgp_key_data_parse_context *ctx,
+				    struct pgp_parse_pubkey *pgp,
+				    struct public_key *key)
+{
+	struct crypto_shash *tfm;
+	struct shash_desc *digest;
+	char *fingerprint;
+	u8 *raw_fingerprint;
+	int digest_size, offset;
+	int ret, i;
+
+	ret = -ENOMEM;
+	tfm = crypto_alloc_shash(pgp->version < PGP_KEY_VERSION_4 ?
+				 "md5" : "sha1", 0, 0);
+	if (!tfm)
+		goto cleanup;
+
+	digest = kmalloc(sizeof(*digest) + crypto_shash_descsize(tfm),
+			 GFP_KERNEL);
+	if (!digest)
+		goto cleanup_tfm;
+
+	digest->tfm = tfm;
+	digest->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
+	ret = crypto_shash_init(digest);
+	if (ret < 0)
+		goto cleanup_hash;
+
+	ret = pgp_calc_pkey_keyid(digest, pgp, key);
+	if (ret < 0)
+		goto cleanup_hash;
+
+	digest_size = crypto_shash_digestsize(tfm);
+
+	raw_fingerprint = kmalloc(digest_size, GFP_KERNEL);
+	if (!raw_fingerprint)
+		goto cleanup_hash;
+
+	ret = crypto_shash_final(digest, raw_fingerprint);
+	if (ret < 0)
+		goto cleanup_raw_fingerprint;
+
+	fingerprint = kmalloc(digest_size * 2 + 1, GFP_KERNEL);
+	if (!fingerprint)
+		goto cleanup_raw_fingerprint;
+
+	offset = digest_size - 8;
+	pr_debug("offset %u/%u\n", offset, digest_size);
+
+	for (i = 0; i < digest_size; i++)
+		sprintf(fingerprint + i * 2, "%02x", raw_fingerprint[i]);
+	pr_debug("fingerprint %s\n", fingerprint);
+
+	memcpy(&key->key_id, raw_fingerprint + offset, 8);
+	key->key_id_size = 8;
+
+	ctx->fingerprint = fingerprint;
+	ret = 0;
+cleanup_raw_fingerprint:
+	kfree(raw_fingerprint);
+cleanup_hash:
+	kfree(digest);
+cleanup_tfm:
+	crypto_free_shash(tfm);
+cleanup:
+	kleave(" = %d", ret);
+	return ret;
+}
+
+/*
+ * Extract a public key or public subkey from the PGP stream.
+ */
+static int pgp_process_public_key(struct pgp_parse_context *context,
+				  enum pgp_packet_tag type,
+				  u8 headerlen,
+				  const u8 *data,
+				  size_t datalen)
+{
+	const struct public_key_algorithm *algo;
+	struct pgp_key_data_parse_context *ctx =
+		container_of(context, struct pgp_key_data_parse_context, pgp);
+	struct pgp_parse_pubkey pgp;
+	struct public_key *key;
+	int i, ret;
+
+	kenter(",%u,%u,,%zu", type, headerlen, datalen);
+
+	if (ctx->subtype) {
+		kleave(" = -ENOKEY [already]");
+		return -EBADMSG;
+	}
+
+	key = kzalloc(sizeof(struct public_key), GFP_KERNEL);
+	if (!key)
+		return -ENOMEM;
+
+	ret = pgp_parse_public_key(&data, &datalen, &pgp);
+	if (ret < 0)
+		goto cleanup;
+
+	if (pgp.pubkey_algo >= PGP_PUBKEY__LAST ||
+	    !pgp_public_key_algorithms[pgp.pubkey_algo]) {
+		pr_debug("Unsupported public key algorithm %u\n",
+			 pgp.pubkey_algo);
+		ret = -ENOPKG;
+		goto cleanup;
+	}
+
+	algo = key->algo = pgp_public_key_algorithms[pgp.pubkey_algo];
+
+	/* It's a public key, so that only gives us encrypt and verify
+	 * capabilities.
+	 */
+	key->capabilities = pgp_public_key_capabilities[pgp.pubkey_algo] &
+		(PKEY_CAN_ENCRYPT | PKEY_CAN_VERIFY);
+
+	ret = -ENOMEM;
+	for (i = 0; i < algo->n_pub_mpi; i++) {
+		unsigned int remaining = datalen;
+		ret = -EBADMSG;
+		if (remaining == 0) {
+			pr_debug("short %zu mpi %d\n", datalen, i);
+			goto cleanup;
+		}
+		key->mpi[i] = mpi_read_from_buffer(data, &remaining);
+		if (!key->mpi[i])
+			goto cleanup;
+		data += remaining;
+		datalen -= remaining;
+	}
+
+	ret = -EBADMSG;
+	if (datalen != 0) {
+		pr_debug("excess %zu\n", datalen);
+		goto cleanup;
+	}
+
+	ret = pgp_generate_fingerprint(ctx, &pgp, key);
+	if (ret < 0)
+		goto cleanup;
+
+	/* We're pinning the module by being linked against it */
+	__module_get(public_key_crypto_key_subtype.owner);
+	ctx->subtype = &public_key_crypto_key_subtype;
+	ctx->payload = key;
+	kleave(" = 0 [use]");
+	return 0;
+
+cleanup:
+	pr_devel("cleanup");
+	if (key) {
+		for (i = 0; i < ARRAY_SIZE(key->mpi); i++)
+			mpi_free(key->mpi[i]);
+		kfree(key);
+	}
+	kleave(" = %d", ret);
+	return ret;
+}
+
+/*
+ * Attempt to parse the instantiation data blob for a key as a PGP packet
+ * message holding a key.
+ */
+static int pgp_key_instantiate(struct key *key,
+			       const void *data, size_t datalen)
+{
+	struct pgp_key_data_parse_context ctx;
+	int ret;
+
+	kenter("");
+
+	ret = key_payload_reserve(key, datalen);
+	if (ret < 0)
+		return ret;
+
+	ctx.pgp.types_of_interest =
+		(1 << PGP_PKT_PUBLIC_KEY) | (1 << PGP_PKT_PUBLIC_SUBKEY);
+	ctx.pgp.process_packet = pgp_process_public_key;
+	ctx.subtype = NULL;
+	ctx.fingerprint = NULL;
+	ctx.payload = NULL;
+
+	ret = pgp_parse_packets(data, datalen, &ctx.pgp);
+	if (ret < 0) {
+		if (ctx.payload)
+			ctx.subtype->destroy(ctx.payload);
+		if (ctx.subtype)
+			module_put(ctx.subtype->owner);
+		kfree(ctx.fingerprint);
+		key_payload_reserve(key, 0);
+		return ret;
+	}
+
+	key->type_data.p[0] = ctx.subtype;
+	key->type_data.p[1] = ctx.fingerprint;
+	key->payload.data = ctx.payload;
+	return 0;
+}
+
+static struct crypto_key_parser pgp_key_parser = {
+	.owner		= THIS_MODULE,
+	.name		= "pgp",
+	.instantiate	= pgp_key_instantiate,
+};
+
+/*
+ * Module stuff
+ */
+static int __init pgp_key_init(void)
+{
+	return register_crypto_key_parser(&pgp_key_parser);
+}
+
+static void __exit pgp_key_exit(void)
+{
+	unregister_crypto_key_parser(&pgp_key_parser);
+}
+
+module_init(pgp_key_init);
+module_exit(pgp_key_exit);
diff --git a/security/keys/crypto/pgp_parser.h b/security/keys/crypto/pgp_parser.h
new file mode 100644
index 0000000..1cda231
--- /dev/null
+++ b/security/keys/crypto/pgp_parser.h
@@ -0,0 +1,23 @@
+/* PGP crypto data parser internal definitions
+ *
+ * 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.
+ */
+
+#include <linux/pgp.h>
+
+#define kenter(FMT, ...) \
+	pr_devel("==> %s("FMT")\n", __func__, ##__VA_ARGS__)
+#define kleave(FMT, ...) \
+	pr_devel("<== %s()"FMT"\n", __func__, ##__VA_ARGS__)
+
+/*
+ * pgp_key_parser.c
+ */
+extern const
+struct public_key_algorithm *pgp_public_key_algorithms[PGP_PUBKEY__LAST];

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