crypto: digital signature verification support

This patch implements RSA digital signature verification using GnuPG library.

The format of the signature and the public key is defined by their respective
headers. The signature header contains version information, algorithm,
and keyid, which was used to generate the signature.
The key header contains version and algorythim type.
The payload of the signature and the key are multi-precision integers.

The signing and key management utilities evm-utils provide functionality
to generate signatures and load keys into the kernel keyring.
When the key is added to the kernel keyring, the keyid defines the name
of the key.

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Acked-by: Mimi Zohar <zohar@us.ibm.com>

1 files changed, 64 insertions, 0 deletions

diff --git a/include/linux/digsig.h b/include/linux/digsig.h
new file mode 100644
index 00000000000..efae755017d
--- /dev/null
+++ b/include/linux/digsig.h
@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2011 Nokia Corporation
+ * Copyright (C) 2011 Intel Corporation
+ *
+ * Author:
+ * Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
+ *                 <dmitry.kasatkin@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ */
+
+#ifndef _DIGSIG_H
+#define _DIGSIG_H
+
+#include <linux/key.h>
+
+enum pubkey_algo {
+	PUBKEY_ALGO_RSA,
+	PUBKEY_ALGO_MAX,
+};
+
+enum digest_algo {
+	DIGEST_ALGO_SHA1,
+	DIGEST_ALGO_SHA256,
+	DIGEST_ALGO_MAX
+};
+
+struct pubkey_hdr {
+	uint8_t		version;	/* key format version */
+	time_t		timestamp;	/* key made, always 0 for now */
+	uint8_t		algo;
+	uint8_t		nmpi;
+	char		mpi[0];
+} __packed;
+
+struct signature_hdr {
+	uint8_t		version;	/* signature format version */
+	time_t		timestamp;	/* signature made */
+	uint8_t		algo;
+	uint8_t		hash;
+	uint8_t		keyid[8];
+	uint8_t		nmpi;
+	char		mpi[0];
+} __packed;
+
+#if defined(CONFIG_DIGSIG) || defined(CONFIG_DIGSIG_MODULE)
+
+int digsig_verify(struct key *keyring, const char *sig, int siglen,
+					const char *digest, int digestlen);
+
+#else
+
+static inline int digsig_verify(struct key *keyring, const char *sig,
+				int siglen, const char *digest, int digestlen)
+{
+	return -EOPNOTSUPP;
+}
+
+#endif /* CONFIG_DIGSIG */
+
+#endif /* _DIGSIG_H */