ESP packet wrapper added, handles encryption/decryption/verification etc.

4 files changed, 554 insertions, 2 deletions

diff --git a/src/libipsec/Android.mk b/src/libipsec/Android.mk
index d452793c4..7292bff59 100644
--- a/src/libipsec/Android.mk
+++ b/src/libipsec/Android.mk
@@ -4,7 +4,8 @@ include $(CLEAR_VARS)
 # copy-n-paste from Makefile.am
 LOCAL_SRC_FILES := \
 ipsec.c ipsec.h \
-esp_context.c esp_context.h
+esp_context.c esp_context.h \
+esp_packet.c esp_packet.h
 
 # build libipsec ---------------------------------------------------------------
 
diff --git a/src/libipsec/Makefile.am b/src/libipsec/Makefile.am
index df0c9acfa..b9ae6d336 100644
--- a/src/libipsec/Makefile.am
+++ b/src/libipsec/Makefile.am
@@ -2,7 +2,8 @@ ipseclib_LTLIBRARIES = libipsec.la
 
 libipsec_la_SOURCES = \
 ipsec.c ipsec.h \
-esp_context.c esp_context.h
+esp_context.c esp_context.h \
+esp_packet.c esp_packet.h
 
 libipsec_la_LIBADD =
 
diff --git a/src/libipsec/esp_packet.c b/src/libipsec/esp_packet.c
new file mode 100644
index 000000000..193bc621d
--- /dev/null
+++ b/src/libipsec/esp_packet.c
@@ -0,0 +1,402 @@
+/*
+ * Copyright (C) 2012 Tobias Brunner
+ * Copyright (C) 2012 Giuliano Grassi
+ * Copyright (C) 2012 Ralf Sager
+ * Hochschule fuer Technik Rapperswil
+ *
+ * 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; either version 2 of the License, or (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ */
+
+
+#include "esp_packet.h"
+
+#include <library.h>
+#include <debug.h>
+#include <crypto/crypters/crypter.h>
+#include <crypto/signers/signer.h>
+#include <bio/bio_reader.h>
+#include <bio/bio_writer.h>
+
+#include <netinet/in.h>
+
+typedef struct private_esp_packet_t private_esp_packet_t;
+
+/**
+ * Private additions to esp_packet_t.
+ */
+struct private_esp_packet_t {
+
+	/**
+	 * Public members
+	 */
+	esp_packet_t public;
+
+	/**
+	 * Source address
+	 */
+	host_t *src;
+
+	/**
+	 * Destination address
+	 */
+	host_t *dst;
+
+	/**
+	 * Payload of this packet
+	 */
+	chunk_t payload;
+
+	/**
+	 * Next Header info (e.g. IPPROTO_IPIP)
+	 */
+	u_int8_t next_header;
+
+	/**
+	 * Raw packet data
+	 */
+	chunk_t packet_data;
+};
+
+METHOD(esp_packet_t, parse_header, bool,
+	private_esp_packet_t *this, u_int32_t *spi)
+{
+	bio_reader_t *reader;
+	u_int32_t seq;
+
+	reader = bio_reader_create(this->packet_data);
+	if (!reader->read_uint32(reader, spi) ||
+		!reader->read_uint32(reader, &seq))
+	{
+		DBG1(DBG_ESP, "failed to parse ESP header: invalid length");
+		reader->destroy(reader);
+		return FALSE;
+	}
+	reader->destroy(reader);
+
+	DBG2(DBG_ESP, "parsed ESP header with SPI %.8x [seq %u]", *spi, seq);
+	*spi = htonl(*spi);
+	return TRUE;
+}
+
+/**
+ * Check padding as specified in RFC 4303
+ */
+static bool check_padding(chunk_t padding)
+{
+	size_t i;
+
+	for (i = 0; i < padding.len; ++i)
+	{
+		if (padding.ptr[i] != (u_int8_t)(i + 1))
+		{
+			return FALSE;
+		}
+	}
+	return TRUE;
+}
+
+/**
+ * Remove the padding from the payload and set the next header info
+ */
+static bool remove_padding(private_esp_packet_t *this)
+{
+	u_int8_t next_header, pad_length;
+	chunk_t padding;
+	bio_reader_t *reader;
+
+	reader = bio_reader_create(this->payload);
+	if (!reader->read_uint8_end(reader, &next_header) ||
+		!reader->read_uint8_end(reader, &pad_length))
+	{
+		DBG1(DBG_ESP, "parsing ESP payload failed: invalid length");
+		reader->destroy(reader);
+		return FALSE;
+	}
+	if (!reader->read_data_end(reader, pad_length, &padding) ||
+		!check_padding(padding))
+	{
+		DBG1(DBG_ESP, "parsing ESP payload failed: invalid padding");
+		reader->destroy(reader);
+		return FALSE;
+	}
+	this->payload = reader->peek(reader);
+	this->next_header = next_header;
+	reader->destroy(reader);
+
+	DBG3(DBG_ESP, "ESP payload:\n  payload %B\n  padding %B\n  "
+		 "padding length = %hhu, next header = %hhu", &this->payload,
+		 &padding, pad_length, this->next_header);
+	return TRUE;
+}
+
+METHOD(esp_packet_t, decrypt, status_t,
+	private_esp_packet_t *this, esp_context_t *esp_context)
+{
+	bio_reader_t *reader;
+	u_int32_t spi, seq;
+	chunk_t spi_seq, iv, icv, ciphertext;
+	crypter_t *crypter;
+	signer_t *signer;
+
+	chunk_free(&this->payload);
+
+	crypter = esp_context->get_crypter(esp_context);
+	signer = esp_context->get_signer(esp_context);
+
+	reader = bio_reader_create(this->packet_data);
+	if (!reader->read_uint32(reader, &spi) ||
+		!reader->read_uint32(reader, &seq) ||
+		!reader->read_data(reader, crypter->get_iv_size(crypter), &iv) ||
+		!reader->read_data_end(reader, signer->get_block_size(signer), &icv) ||
+		reader->remaining(reader) % crypter->get_block_size(crypter))
+	{
+		DBG1(DBG_ESP, "ESP decryption failed: invalid length");
+		return PARSE_ERROR;
+	}
+	ciphertext = reader->peek(reader);
+	reader->destroy(reader);
+
+	if (!esp_context->verify_seqno(esp_context, seq))
+	{
+		DBG1(DBG_ESP, "ESP sequence number verification failed:\n  "
+			 "src %H, dst %H, SPI %.8x [seq %u]",
+			 this->src, this->dst, spi, seq);
+		return VERIFY_ERROR;
+	}
+	DBG3(DBG_ESP, "ESP decryption:\n  SPI %.8x [seq %u]\n  IV %B\n  "
+		 "encrypted %B\n  ICV %B", spi, seq, &iv, &ciphertext, &icv);
+
+	spi_seq = chunk_create(this->packet_data.ptr, 8);
+	if (!signer->get_signature(signer, spi_seq, NULL) ||
+		!signer->get_signature(signer, iv, NULL) ||
+		!signer->verify_signature(signer, ciphertext, icv))
+	{
+		DBG1(DBG_ESP, "ICV verification failed!");
+		return FAILED;
+	}
+	esp_context->set_authenticated_seqno(esp_context, seq);
+
+	if (!crypter->decrypt(crypter, ciphertext, iv, &this->payload))
+	{
+		DBG1(DBG_ESP, "ESP decryption failed");
+		return FAILED;
+	}
+
+	if (!remove_padding(this))
+	{
+		chunk_free(&this->payload);
+		return PARSE_ERROR;
+	}
+	return SUCCESS;
+}
+
+/**
+ * Generate the padding as specified in RFC4303
+ */
+static void generate_padding(chunk_t padding)
+{
+	size_t i;
+
+	for (i = 0; i < padding.len; ++i)
+	{
+		padding.ptr[i] = (u_int8_t)(i + 1);
+	}
+}
+
+METHOD(esp_packet_t, encrypt, status_t,
+	private_esp_packet_t *this, esp_context_t *esp_context, u_int32_t spi)
+{
+	chunk_t iv, icv, padding, ciphertext, auth_data;
+	bio_writer_t *writer;
+	u_int32_t next_seqno;
+	size_t blocksize, plainlen;
+	crypter_t *crypter;
+	signer_t *signer;
+	rng_t *rng;
+
+	chunk_free(&this->packet_data);
+
+	if (!esp_context->next_seqno(esp_context, &next_seqno))
+	{
+		DBG1(DBG_ESP, "ESP encapsulation failed: sequence numbers cycled");
+		return FAILED;
+	}
+
+	rng = lib->crypto->create_rng(lib->crypto, RNG_WEAK);
+	if (!rng)
+	{
+		DBG1(DBG_ESP, "ESP encryption failed: could not find RNG");
+		return NOT_FOUND;
+	}
+	crypter = esp_context->get_crypter(esp_context);
+	signer = esp_context->get_signer(esp_context);
+
+	blocksize = crypter->get_block_size(crypter);
+	iv.len = crypter->get_iv_size(crypter);
+	icv.len = signer->get_block_size(signer);
+
+	/* plaintext = payload, padding, pad_length, next_header */
+	plainlen = this->payload.len + 2;
+	padding.len = blocksize - (plainlen % blocksize);
+	plainlen += padding.len;
+
+	/* len = spi, seq, IV, plaintext, ICV */
+	writer = bio_writer_create(2 * sizeof(u_int32_t) + iv.len + plainlen +
+							   icv.len);
+	writer->write_uint32(writer, ntohl(spi));
+	writer->write_uint32(writer, next_seqno);
+
+	iv = writer->skip(writer, iv.len);
+	if (!rng->get_bytes(rng, iv.len, iv.ptr))
+	{
+		DBG1(DBG_ESP, "ESP encryption failed: could not generate IV");
+		writer->destroy(writer);
+		rng->destroy(rng);
+		return FAILED;
+	}
+	rng->destroy(rng);
+
+	/* plain-/ciphertext will start here */
+	ciphertext = writer->get_buf(writer);
+	ciphertext.ptr += ciphertext.len;
+	ciphertext.len = plainlen;
+
+	writer->write_data(writer, this->payload);
+
+	padding = writer->skip(writer, padding.len);
+	generate_padding(padding);
+
+	writer->write_uint8(writer, padding.len);
+	writer->write_uint8(writer, this->next_header);
+
+	DBG3(DBG_ESP, "ESP before encryption:\n  payload = %B\n  padding = %B\n  "
+		 "padding length = %hhu, next header = %hhu", &this->payload, &padding,
+		 (u_int8_t)padding.len, this->next_header);
+
+	/* encrypt the content inline */
+	if (!crypter->encrypt(crypter, ciphertext, iv, NULL))
+	{
+		DBG1(DBG_ESP, "ESP encryption failed");
+		writer->destroy(writer);
+		return FAILED;
+	}
+
+	/* calculate signature */
+	auth_data = writer->get_buf(writer);
+	icv = writer->skip(writer, icv.len);
+	if (!signer->get_signature(signer, auth_data, icv.ptr))
+	{
+		DBG1(DBG_ESP, "ESP encryption failed: signature generation failed");
+		writer->destroy(writer);
+		return FAILED;
+	}
+
+	DBG3(DBG_ESP, "ESP packet:\n  SPI %.8x [seq %u]\n  IV %B\n  "
+		 "encrypted %B\n  ICV %B", ntohl(spi), next_seqno, &iv,
+		 &ciphertext, &icv);
+
+	this->packet_data = writer->extract_buf(writer);
+	writer->destroy(writer);
+	return SUCCESS;
+}
+
+METHOD(esp_packet_t, get_next_header, u_int8_t,
+	private_esp_packet_t *this)
+{
+	return this->next_header;
+}
+
+METHOD(esp_packet_t, get_payload, chunk_t,
+	private_esp_packet_t *this)
+{
+	return this->payload;
+}
+
+METHOD(esp_packet_t, get_packet_data, chunk_t,
+	private_esp_packet_t *this)
+{
+	return this->packet_data;
+}
+
+METHOD(esp_packet_t, get_source, host_t*,
+	private_esp_packet_t *this)
+{
+	return this->src;
+}
+
+METHOD(esp_packet_t, get_destination, host_t*,
+	private_esp_packet_t *this)
+{
+	return this->dst;
+}
+
+METHOD(esp_packet_t, destroy, void,
+	private_esp_packet_t *this)
+{
+	chunk_free(&this->payload);
+	chunk_free(&this->packet_data);
+	this->src->destroy(this->src);
+	this->dst->destroy(this->dst);
+	free(this);
+}
+
+static private_esp_packet_t *esp_packet_create_empty(host_t *src, host_t *dst)
+{
+	private_esp_packet_t *this;
+
+	INIT(this,
+		.public = {
+			.get_source = _get_source,
+			.get_destination = _get_destination,
+			.get_packet_data = _get_packet_data,
+			.get_payload = _get_payload,
+			.get_next_header = _get_next_header,
+			.parse_header = _parse_header,
+			.decrypt = _decrypt,
+			.encrypt = _encrypt,
+			.destroy = _destroy,
+		},
+		.src = src,
+		.dst = dst,
+		.next_header = IPPROTO_NONE,
+	);
+	return this;
+}
+
+/**
+ * Described in header.
+ */
+esp_packet_t *esp_packet_create_from_packet(host_t *src, host_t *dst,
+											chunk_t packet_data)
+{
+	private_esp_packet_t *this;
+
+	this = esp_packet_create_empty(src, dst);
+	this->packet_data = packet_data;
+
+	return &this->public;
+}
+
+/**
+ * Described in header.
+ */
+esp_packet_t *esp_packet_create_from_payload(host_t *src, host_t *dst,
+										chunk_t payload, u_int8_t next_header)
+{
+	private_esp_packet_t *this;
+
+	this = esp_packet_create_empty(src, dst);
+	this->next_header = next_header;
+	this->payload = payload;
+
+	return &this->public;
+}
+
diff --git a/src/libipsec/esp_packet.h b/src/libipsec/esp_packet.h
new file mode 100644
index 000000000..473eeb4e5
--- /dev/null
+++ b/src/libipsec/esp_packet.h
@@ -0,0 +1,148 @@
+/*
+ * Copyright (C) 2012 Tobias Brunner
+ * Copyright (C) 2012 Giuliano Grassi
+ * Copyright (C) 2012 Ralf Sager
+ * Hochschule fuer Technik Rapperswil
+ *
+ * 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; either version 2 of the License, or (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ */
+
+/**
+ * @defgroup esp_packet esp_packet
+ * @{ @ingroup libipsec
+ */
+
+#ifndef ESP_PACKET_H_
+#define ESP_PACKET_H_
+
+#include "esp_context.h"
+
+#include <library.h>
+#include <utils/host.h>
+
+typedef struct esp_packet_t esp_packet_t;
+
+/**
+ *  ESP packet
+ */
+struct esp_packet_t {
+
+	/**
+	 * Get the source address of this packet
+	 *
+	 * @return				source host
+	 */
+	host_t *(*get_source)(esp_packet_t *this);
+
+	/**
+	 * Get the destination address of this packet
+	 *
+	 * @return				destination host
+	 */
+	host_t *(*get_destination)(esp_packet_t *this);
+
+	/**
+	 * Parse the packet header before decryption. Tries to read the SPI
+	 * from the packet to find a corresponding SA.
+	 *
+	 * @param spi			parsed SPI, in network byte order
+	 * @return				TRUE when successful, FALSE otherwise (e.g. when the
+	 *						length of the packet is invalid)
+	 */
+	bool (*parse_header)(esp_packet_t *this, u_int32_t *spi);
+
+	/**
+	 * Authenticate and decrypt the packet. Also verifies the sequence number
+	 * using the supplied ESP context and updates the anti-replay window.
+	 *
+	 * @param esp_context		ESP context of corresponding inbound IPsec SA
+	 * @return					- SUCCESS if successfully authenticated,
+	 *							  decrypted and parsed
+	 *							- PARSE_ERROR if the length of the packet or the
+	 *							  padding is invalid
+	 *							- VERIFY_ERROR if the sequence number
+	 *							  verification failed
+	 *							- FAILED if the ICV (MAC) check or the actual
+	 *							  decryption failed
+	 */
+	status_t (*decrypt)(esp_packet_t *this, esp_context_t *esp_context);
+
+	/**
+	 * Encapsulate and encrypt the packet. The sequence number will be generated
+	 * using the supplied ESP context.
+	 *
+	 * @param esp_context		ESP context of corresponding outbound IPsec SA
+	 * @param spi				SPI value to use, in network byte order
+	 * @return					- SUCCESS if encrypted
+	 *							- FAILED if sequence number cycled or any of the
+	 *							  cryptographic functions failed
+	 *							- NOT_FOUND if no suitable RNG could be found
+	 */
+	status_t (*encrypt)(esp_packet_t *this, esp_context_t *esp_context,
+						u_int32_t spi);
+
+	/**
+	 * Get the next header field of a packet.
+	 *
+	 * @note Packet has to be in the decrypted state.
+	 *
+	 * @return					next header field
+	 */
+	u_int8_t (*get_next_header)(esp_packet_t *this);
+
+	/**
+	 * Get the plaintext payload of this packet (e.g. inner IP packet).
+	 *
+	 * @return					plaintext payload (internal data),
+	 * 							chunk_empty if not decrypted
+	 */
+	chunk_t (*get_payload)(esp_packet_t *this);
+
+	/**
+	 * Get the packet data to send / as received on the wire.
+	 *
+	 * @return					encrypted packet data (internal data),
+	 * 							chunk_empty if not encrypted
+	 */
+	chunk_t (*get_packet_data)(esp_packet_t *this);
+
+	/**
+	 * Destroy an esp_packet_t
+	 */
+	void (*destroy)(esp_packet_t *this);
+
+};
+
+/**
+ * Create an ESP packet out of data from the wire.
+ *
+ * @param src			source address from which the packet was sent, owned
+ * @param dst			destination address to which the packet was sent, owned
+ * @param data			the packet data as received, gets owned
+ * @return				esp_packet_t instance
+ */
+esp_packet_t *esp_packet_create_from_packet(host_t *src, host_t *dst,
+											chunk_t data);
+
+/**
+ * Create an ESP packet from a plaintext payload (e.g. inner IP packet)
+ *
+ * @param src			source address
+ * @param dst			destination address
+ * @param payload		plaintext payload (e.g. inner IP packet), gets owned
+ * @param next_header	next header type of the payload (e.g IPPROTO_IPIP)
+ * @return				esp_packet_t instance
+ */
+esp_packet_t *esp_packet_create_from_payload(host_t *src, host_t *dst,
+										chunk_t payload, u_int8_t next_header);
+
+#endif /** ESP_PACKET_H_ @}*/
+