[PATCH 13/21] PGPLIB: Basic packet parser [ver #3]

[David Howells <dhowells@redhat.com>]

Provide a simple parser that extracts the packets from a PGP packet blob and
passes the desirous ones to the given processor function:

	struct pgp_parse_context {
		u64 types_of_interest;
		int (*process_packet)(struct pgp_parse_context *context,
				      enum pgp_packet_tag type,
				      u8 headerlen,
				      const u8 *data,
				      size_t datalen);
	};

	int pgp_parse_packets(const u8 *data, size_t datalen,
			      struct pgp_parse_context *ctx);

This is configured on with CONFIG_PGP_LIBRARY.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 include/linux/pgp.h         |   25 ++++
 security/keys/Kconfig       |    6 +
 security/keys/Makefile      |    1 
 security/keys/pgp_library.c |  254 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 286 insertions(+), 0 deletions(-)
 create mode 100644 security/keys/pgp_library.c


diff --git a/include/linux/pgp.h b/include/linux/pgp.h
index 5d4b372..06f5aaa 100644
--- a/include/linux/pgp.h
+++ b/include/linux/pgp.h
@@ -203,4 +203,29 @@ struct pgp_key_v4_packet {
 	u8 key_material[0];
 };
 
+/*
+ * PGP library packet parser
+ */
+struct pgp_parse_context {
+	u64 types_of_interest;
+	int (*process_packet)(struct pgp_parse_context *context,
+			      enum pgp_packet_tag type,
+			      u8 headerlen,
+			      const u8 *data,
+			      size_t datalen);
+};
+
+extern int pgp_parse_packets(const u8 *data, size_t datalen,
+			     struct pgp_parse_context *ctx);
+
+struct pgp_parse_pubkey {
+	enum pgp_key_version version : 8;
+	enum pgp_pubkey_algo pubkey_algo : 8;
+	time_t		creation_time;
+	time_t		expires_at;
+};
+
+extern int pgp_parse_public_key(const u8 **_data, size_t *_datalen,
+				struct pgp_parse_pubkey *pk);
+
 #endif /* _LINUX_PGP_H */
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index 0090cd5..3196ba8 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -99,3 +99,9 @@ config CRYPTO_KEY_PKEY_ALGO_RSA
 	depends on CRYPTO_KEY_PUBLIC_KEY_SUBTYPE
 	help
 	  This option enables support for the RSA algorithm (PKCS#1, RFC3447).
+
+config PGP_LIBRARY
+	tristate "PGP parsing library"
+	help
+	  This option enables a library that provides a number of simple
+	  utility functions for parsing PGP (RFC 4880) packet-based messages.
diff --git a/security/keys/Makefile b/security/keys/Makefile
index 7245a20..3c3918a 100644
--- a/security/keys/Makefile
+++ b/security/keys/Makefile
@@ -28,5 +28,6 @@ obj-$(CONFIG_CRYPTO_KEY_TYPE) += crypto_keys.o
 obj-$(CONFIG_CRYPTO_KEY_PUBLIC_KEY_SUBTYPE) += public_key.o
 obj-$(CONFIG_CRYPTO_KEY_PKEY_ALGO_DSA) += crypto_dsa.o
 obj-$(CONFIG_CRYPTO_KEY_PKEY_ALGO_RSA) += crypto_rsa.o
+obj-$(CONFIG_PGP_LIBRARY) += pgp_library.o
 
 crypto_keys-y := crypto_type.o crypto_verify.o
diff --git a/security/keys/pgp_library.c b/security/keys/pgp_library.c
new file mode 100644
index 0000000..685660f
--- /dev/null
+++ b/security/keys/pgp_library.c
@@ -0,0 +1,254 @@
+/* PGP packet parser (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) "PGP: "fmt
+#include <linux/pgp.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+MODULE_LICENSE("GPL");
+
+const char *const pgp_hash_algorithms[PGP_HASH__LAST] = {
+	[PGP_HASH_MD5]			= "md5",
+	[PGP_HASH_SHA1]			= "sha1",
+	[PGP_HASH_RIPE_MD_160]		= "rmd160",
+	[PGP_HASH_SHA256]		= "sha256",
+	[PGP_HASH_SHA384]		= "sha384",
+	[PGP_HASH_SHA512]		= "sha512",
+	[PGP_HASH_SHA224]		= "sha224",
+};
+EXPORT_SYMBOL_GPL(pgp_hash_algorithms);
+
+/**
+ * pgp_parse_packet_header - Parse a PGP packet header
+ * @_data: Start of the PGP packet (updated to PGP packet data)
+ * @_datalen: Amount of data remaining in buffer (decreased)
+ * @_type: Where the packet type will be returned
+ * @_headerlen: Where the header length will be returned
+ *
+ * Parse a set of PGP packet header [RFC 4880: 4.2].
+ *
+ * Returns packet data size on success; non-zero on error.  If successful,
+ * *_data and *_datalen will have been updated and *_headerlen will be set to
+ * hold the length of the packet header.
+ */
+ssize_t pgp_parse_packet_header(const u8 **_data, size_t *_datalen,
+				enum pgp_packet_tag *_type,
+				u8 *_headerlen)
+{
+	enum pgp_packet_tag type;
+	const u8 *data = *_data;
+	size_t size, datalen = *_datalen;
+
+	pr_devel("-->pgp_parse_packet_header(,%zu,,)", datalen);
+
+	if (datalen < 2)
+		goto short_packet;
+
+	pr_devel("pkthdr %02x, %02x\n", data[0], data[1]);
+
+	type = *data++;
+	datalen--;
+	if (!(type & 0x80)) {
+		pr_debug("Packet type does not have MSB set\n");
+		return -EBADMSG;
+	}
+	type &= ~0x80;
+
+	if (type & 0x40) {
+		/* New packet length format */
+		type &= ~0x40;
+		pr_devel("new format: t=%u\n", type);
+		switch (data[0]) {
+		case 0x00 ... 0xbf:
+			/* One-byte length */
+			size = data[0];
+			data++;
+			datalen--;
+			*_headerlen = 2;
+			break;
+		case 0xc0 ... 0xdf:
+			/* Two-byte length */
+			if (datalen < 2)
+				goto short_packet;
+			size = (data[0] - 192) * 256;
+			size += data[1] + 192;
+			data += 2;
+			datalen -= 2;
+			*_headerlen = 3;
+			break;
+		case 0xff:
+			pr_debug("Five-byte packet length not supported\n");
+			return -EBADMSG;
+		default:
+			pr_debug("Error parsing packet length\n");
+			return -EBADMSG;
+		}
+	} else {
+		/* Old packet length format */
+		u8 length_type = type & 0x03;
+		type >>= 2;
+		pr_devel("old format: t=%u lt=%u\n", type, length_type);
+
+		switch (length_type) {
+		case 0:
+			/* One-byte length */
+			size = data[0];
+			data++;
+			datalen--;
+			*_headerlen = 2;
+			break;
+		case 1:
+			/* Two-byte length */
+			if (datalen < 2)
+				goto short_packet;
+			size  = data[0] << 8;
+			size |= data[1];
+			data += 2;
+			datalen -= 2;
+			*_headerlen = 3;
+			break;
+		case 2:
+			/* Four-byte length */
+			if (datalen < 4)
+				goto short_packet;
+			size  = data[0] << 24;
+			size |= data[1] << 16;
+			size |= data[2] << 8;
+			size |= data[3];
+			data += 4;
+			datalen -= 4;
+			*_headerlen = 5;
+			break;
+		default:
+			pr_debug("Indefinite length packet not supported\n");
+			return -EBADMSG;
+		}
+	}
+
+	pr_devel("datalen=%zu size=%zu", datalen, size);
+	if (datalen < size)
+		goto short_packet;
+
+	*_data = data;
+	*_datalen = datalen;
+	*_type = type;
+	pr_devel("Found packet type=%u size=%zd\n", type, size);
+	return size;
+
+short_packet:
+	pr_debug("Attempt to parse short packet\n");
+	return -EBADMSG;
+}
+
+/**
+ * pgp_parse_packets - Parse a set of PGP packets
+ * @_data: Data to be parsed (updated)
+ * @_datalen: Amount of data (updated)
+ * @ctx: Parsing context
+ *
+ * Parse a set of PGP packets [RFC 4880: 4].
+ */
+int pgp_parse_packets(const u8 *data, size_t datalen,
+		      struct pgp_parse_context *ctx)
+{
+	enum pgp_packet_tag type;
+	ssize_t pktlen;
+	u8 headerlen;
+	int ret;
+
+	while (datalen > 2) {
+		pktlen = pgp_parse_packet_header(&data, &datalen, &type,
+						 &headerlen);
+		if (pktlen < 0)
+			return pktlen;
+
+		if ((ctx->types_of_interest >> type) & 1) {
+			ret = ctx->process_packet(ctx, type, headerlen,
+						  data, pktlen);
+			if (ret < 0)
+				return ret;
+		}
+		data += pktlen;
+		datalen -= pktlen;
+	}
+
+	if (datalen != 0) {
+		pr_debug("Excess octets in packet stream\n");
+		return -EBADMSG;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pgp_parse_packets);
+
+/**
+ * pgp_parse_public_key - Parse the common part of a PGP pubkey packet
+ * @_data: Content of packet (updated)
+ * @_datalen: Length of packet remaining (updated)
+ * @pk: Public key data
+ *
+ * Parse the common data struct for a PGP pubkey packet [RFC 4880: 5.5.2].
+ */
+int pgp_parse_public_key(const u8 **_data, size_t *_datalen,
+			 struct pgp_parse_pubkey *pk)
+{
+	const u8 *data = *_data;
+	size_t datalen = *_datalen;
+	__be32 tmp;
+
+	if (datalen < 12) {
+		pr_debug("Public key packet too short\n");
+		return -EBADMSG;
+	}
+
+	pk->version = *data++;
+	switch (pk->version) {
+	case PGP_KEY_VERSION_2:
+	case PGP_KEY_VERSION_3:
+	case PGP_KEY_VERSION_4:
+		break;
+	default:
+		pr_debug("Public key packet with unhandled version %d\n",
+			   pk->version);
+		return -EBADMSG;
+	}
+
+	tmp  = *data++ << 24;
+	tmp |= *data++ << 16;
+	tmp |= *data++ << 8;
+	tmp |= *data++;
+	pk->creation_time = tmp;
+	if (pk->version == PGP_KEY_VERSION_4) {
+		pk->expires_at = 0; /* Have to get it from the selfsignature */
+	} else {
+		unsigned short ndays;
+		ndays  = *data++ << 8;
+		ndays |= *data++;
+		if (ndays)
+			pk->expires_at = pk->creation_time + ndays * 86400UL;
+		else
+			pk->expires_at = 0;
+		datalen -= 2;
+	}
+
+	pk->pubkey_algo = *data++;
+	datalen -= 6;
+
+	pr_devel("%x,%x,%lx,%lx",
+		 pk->version, pk->pubkey_algo, pk->creation_time,
+		 pk->expires_at);
+
+	*_data = data;
+	*_datalen = datalen;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pgp_parse_public_key);