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Subject[PATCH 17/21] KEYS: PGP format signature parser [ver #3]
Date
Implement a signature parser that will attempt to parse a signature blob as a
PGP packet format message. If it can, it will find an appropriate crypto key
and set the public-key algorithm according to the data in the signature.

Signed-off-by: David Howells <dhowells@redhat.com>
---
security/keys/Makefile | 1
security/keys/pgp_key_parser.c | 1
security/keys/pgp_parser.h | 6 ++
security/keys/pgp_sig_parser.c | 104 ++++++++++++++++++++++++++++++++++++++++
4 files changed, 112 insertions(+), 0 deletions(-)
create mode 100644 security/keys/pgp_sig_parser.c

diff --git a/security/keys/Makefile b/security/keys/Makefile
index fc1968e..c7fa7ea 100644
--- a/security/keys/Makefile
+++ b/security/keys/Makefile
@@ -35,4 +35,5 @@ crypto_keys-y := crypto_type.o crypto_verify.o

pgp_parser-y := \
pgp_key_parser.o \
+ pgp_sig_parser.o \
pgp_pubkey_sig.o
diff --git a/security/keys/pgp_key_parser.c b/security/keys/pgp_key_parser.c
index d0d8a86..12a7644 100644
--- a/security/keys/pgp_key_parser.c
+++ b/security/keys/pgp_key_parser.c
@@ -323,6 +323,7 @@ static struct crypto_key_parser pgp_key_parser = {
.owner = THIS_MODULE,
.name = "pgp",
.instantiate = pgp_key_instantiate,
+ .verify_sig_begin = pgp_verify_sig_begin,
};

/*
diff --git a/security/keys/pgp_parser.h b/security/keys/pgp_parser.h
index a6192ce..73c900e 100644
--- a/security/keys/pgp_parser.h
+++ b/security/keys/pgp_parser.h
@@ -23,6 +23,12 @@ extern const
struct public_key_algorithm *pgp_public_key_algorithms[PGP_PUBKEY__LAST];

/*
+ * pgp_sig_parser.c
+ */
+extern struct crypto_key_verify_context *pgp_verify_sig_begin(
+ struct key *keyring, const u8 *sig, size_t siglen);
+
+/*
* pgp_pubkey_sig.c
*/
extern struct crypto_key_verify_context *pgp_pkey_verify_sig_begin(
diff --git a/security/keys/pgp_sig_parser.c b/security/keys/pgp_sig_parser.c
new file mode 100644
index 0000000..b72c505
--- /dev/null
+++ b/security/keys/pgp_sig_parser.c
@@ -0,0 +1,104 @@
+/* Handling for PGP public key signature data [RFC 4880]
+ *
+ * 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.
+ */
+
+#define pr_fmt(fmt) "PGPSIG: "fmt
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/pgp.h>
+#include "public_key.h"
+#include "pgp_parser.h"
+
+struct PGP_sig_parse_context {
+ struct pgp_parse_context pgp;
+ struct pgp_sig_parameters params;
+ bool found_sig;
+};
+
+/*
+ * Look inside signature sections for a key ID
+ */
+static int pgp_process_signature(struct pgp_parse_context *context,
+ enum pgp_packet_tag type,
+ u8 headerlen,
+ const u8 *data,
+ size_t datalen)
+{
+ struct PGP_sig_parse_context *ctx =
+ container_of(context, struct PGP_sig_parse_context, pgp);
+
+ ctx->found_sig = true;
+ return pgp_parse_sig_params(&data, &datalen, &ctx->params);
+}
+
+/*
+ * Attempt to find a key to use for PGP signature verification, starting off by
+ * looking in the supplied keyring.
+ *
+ * The function may also look for other key sources such as a TPM. If an
+ * alternative key is found it can be added to the keyring for future
+ * reference.
+ */
+static struct key *find_key_for_pgp_sig(struct key *keyring,
+ const u8 *sig, size_t siglen)
+{
+ struct PGP_sig_parse_context p;
+ key_ref_t key;
+ char criterion[3 + 8 * 2 + 1];
+ int ret;
+
+ if (!keyring)
+ return ERR_PTR(-ENOKEY);
+
+ /* Need to find the key ID */
+ p.pgp.types_of_interest = (1 << PGP_PKT_SIGNATURE);
+ p.pgp.process_packet = pgp_process_signature;
+ p.found_sig = false;
+ ret = pgp_parse_packets(sig, siglen, &p.pgp);
+ if (ret < 0)
+ return ERR_PTR(ret);
+
+ if (!p.found_sig)
+ return ERR_PTR(-EINVAL);
+
+ sprintf(criterion, "id:%08x%08x",
+ be32_to_cpu(p.params.issuer32[0]),
+ be32_to_cpu(p.params.issuer32[1]));
+
+ pr_debug("Look up: %s\n", criterion);
+
+ key = keyring_search(make_key_ref(keyring, 1),
+ &key_type_crypto, criterion);
+ if (IS_ERR(key))
+ return ERR_CAST(key);
+
+ pr_debug("Found key %x\n", key_serial(key_ref_to_ptr(key)));
+ return key_ref_to_ptr(key);
+}
+
+/*
+ * Attempt to parse a signature as a PGP packet format blob and find a
+ * matching key.
+ */
+struct crypto_key_verify_context *pgp_verify_sig_begin(
+ struct key *keyring, const u8 *sig, size_t siglen)
+{
+ struct crypto_key_verify_context *ctx;
+ struct key *key;
+
+ key = find_key_for_pgp_sig(keyring, sig, siglen);
+ if (IS_ERR(key))
+ return ERR_CAST(key);
+
+ /* We only handle in-kernel public key signatures for the moment */
+ ctx = pgp_pkey_verify_sig_begin(key, sig, siglen);
+ key_put(key);
+ return ctx;
+}


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