ESP packet wrapper added, handles encryption/decryption/verification etc.
This commit is contained in:
Tobias Brunner
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/*
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* Copyright (C) 2012 Tobias Brunner
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* Copyright (C) 2012 Giuliano Grassi
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* Copyright (C) 2012 Ralf Sager
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* Hochschule fuer Technik Rapperswil
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*/
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#include "esp_packet.h"
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#include <library.h>
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#include <debug.h>
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#include <crypto/crypters/crypter.h>
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#include <crypto/signers/signer.h>
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#include <bio/bio_reader.h>
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#include <bio/bio_writer.h>
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#include <netinet/in.h>
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typedef struct private_esp_packet_t private_esp_packet_t;
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/**
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* Private additions to esp_packet_t.
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*/
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struct private_esp_packet_t {
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/**
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* Public members
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*/
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esp_packet_t public;
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/**
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* Source address
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*/
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host_t *src;
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/**
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* Destination address
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*/
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host_t *dst;
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/**
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* Payload of this packet
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*/
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chunk_t payload;
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/**
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* Next Header info (e.g. IPPROTO_IPIP)
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*/
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u_int8_t next_header;
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/**
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* Raw packet data
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*/
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chunk_t packet_data;
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};
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METHOD(esp_packet_t, parse_header, bool,
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private_esp_packet_t *this, u_int32_t *spi)
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{
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bio_reader_t *reader;
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u_int32_t seq;
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reader = bio_reader_create(this->packet_data);
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if (!reader->read_uint32(reader, spi) ||
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!reader->read_uint32(reader, &seq))
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{
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DBG1(DBG_ESP, "failed to parse ESP header: invalid length");
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reader->destroy(reader);
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return FALSE;
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}
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reader->destroy(reader);
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DBG2(DBG_ESP, "parsed ESP header with SPI %.8x [seq %u]", *spi, seq);
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*spi = htonl(*spi);
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return TRUE;
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}
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/**
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* Check padding as specified in RFC 4303
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*/
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static bool check_padding(chunk_t padding)
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{
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size_t i;
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for (i = 0; i < padding.len; ++i)
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{
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if (padding.ptr[i] != (u_int8_t)(i + 1))
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{
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return FALSE;
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}
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}
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return TRUE;
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}
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/**
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* Remove the padding from the payload and set the next header info
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*/
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static bool remove_padding(private_esp_packet_t *this)
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{
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u_int8_t next_header, pad_length;
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chunk_t padding;
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bio_reader_t *reader;
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reader = bio_reader_create(this->payload);
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if (!reader->read_uint8_end(reader, &next_header) ||
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!reader->read_uint8_end(reader, &pad_length))
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{
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DBG1(DBG_ESP, "parsing ESP payload failed: invalid length");
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reader->destroy(reader);
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return FALSE;
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}
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if (!reader->read_data_end(reader, pad_length, &padding) ||
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!check_padding(padding))
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{
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DBG1(DBG_ESP, "parsing ESP payload failed: invalid padding");
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reader->destroy(reader);
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return FALSE;
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}
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this->payload = reader->peek(reader);
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this->next_header = next_header;
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reader->destroy(reader);
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DBG3(DBG_ESP, "ESP payload:\n payload %B\n padding %B\n "
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"padding length = %hhu, next header = %hhu", &this->payload,
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&padding, pad_length, this->next_header);
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return TRUE;
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}
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METHOD(esp_packet_t, decrypt, status_t,
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private_esp_packet_t *this, esp_context_t *esp_context)
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{
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bio_reader_t *reader;
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u_int32_t spi, seq;
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chunk_t spi_seq, iv, icv, ciphertext;
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crypter_t *crypter;
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signer_t *signer;
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chunk_free(&this->payload);
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crypter = esp_context->get_crypter(esp_context);
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signer = esp_context->get_signer(esp_context);
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reader = bio_reader_create(this->packet_data);
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if (!reader->read_uint32(reader, &spi) ||
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!reader->read_uint32(reader, &seq) ||
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!reader->read_data(reader, crypter->get_iv_size(crypter), &iv) ||
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!reader->read_data_end(reader, signer->get_block_size(signer), &icv) ||
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reader->remaining(reader) % crypter->get_block_size(crypter))
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{
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DBG1(DBG_ESP, "ESP decryption failed: invalid length");
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return PARSE_ERROR;
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}
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ciphertext = reader->peek(reader);
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reader->destroy(reader);
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if (!esp_context->verify_seqno(esp_context, seq))
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{
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DBG1(DBG_ESP, "ESP sequence number verification failed:\n "
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"src %H, dst %H, SPI %.8x [seq %u]",
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this->src, this->dst, spi, seq);
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return VERIFY_ERROR;
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}
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DBG3(DBG_ESP, "ESP decryption:\n SPI %.8x [seq %u]\n IV %B\n "
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"encrypted %B\n ICV %B", spi, seq, &iv, &ciphertext, &icv);
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spi_seq = chunk_create(this->packet_data.ptr, 8);
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if (!signer->get_signature(signer, spi_seq, NULL) ||
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!signer->get_signature(signer, iv, NULL) ||
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!signer->verify_signature(signer, ciphertext, icv))
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{
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DBG1(DBG_ESP, "ICV verification failed!");
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return FAILED;
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}
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esp_context->set_authenticated_seqno(esp_context, seq);
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if (!crypter->decrypt(crypter, ciphertext, iv, &this->payload))
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{
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DBG1(DBG_ESP, "ESP decryption failed");
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return FAILED;
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}
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if (!remove_padding(this))
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{
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chunk_free(&this->payload);
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return PARSE_ERROR;
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}
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return SUCCESS;
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}
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/**
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* Generate the padding as specified in RFC4303
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*/
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static void generate_padding(chunk_t padding)
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{
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size_t i;
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for (i = 0; i < padding.len; ++i)
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{
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padding.ptr[i] = (u_int8_t)(i + 1);
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}
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}
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METHOD(esp_packet_t, encrypt, status_t,
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private_esp_packet_t *this, esp_context_t *esp_context, u_int32_t spi)
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{
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chunk_t iv, icv, padding, ciphertext, auth_data;
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bio_writer_t *writer;
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u_int32_t next_seqno;
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size_t blocksize, plainlen;
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crypter_t *crypter;
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signer_t *signer;
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rng_t *rng;
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chunk_free(&this->packet_data);
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if (!esp_context->next_seqno(esp_context, &next_seqno))
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{
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DBG1(DBG_ESP, "ESP encapsulation failed: sequence numbers cycled");
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return FAILED;
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}
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rng = lib->crypto->create_rng(lib->crypto, RNG_WEAK);
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if (!rng)
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{
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DBG1(DBG_ESP, "ESP encryption failed: could not find RNG");
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return NOT_FOUND;
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}
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crypter = esp_context->get_crypter(esp_context);
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signer = esp_context->get_signer(esp_context);
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blocksize = crypter->get_block_size(crypter);
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iv.len = crypter->get_iv_size(crypter);
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icv.len = signer->get_block_size(signer);
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/* plaintext = payload, padding, pad_length, next_header */
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plainlen = this->payload.len + 2;
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padding.len = blocksize - (plainlen % blocksize);
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plainlen += padding.len;
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/* len = spi, seq, IV, plaintext, ICV */
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writer = bio_writer_create(2 * sizeof(u_int32_t) + iv.len + plainlen +
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icv.len);
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writer->write_uint32(writer, ntohl(spi));
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writer->write_uint32(writer, next_seqno);
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iv = writer->skip(writer, iv.len);
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if (!rng->get_bytes(rng, iv.len, iv.ptr))
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{
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DBG1(DBG_ESP, "ESP encryption failed: could not generate IV");
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writer->destroy(writer);
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rng->destroy(rng);
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return FAILED;
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}
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rng->destroy(rng);
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/* plain-/ciphertext will start here */
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ciphertext = writer->get_buf(writer);
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ciphertext.ptr += ciphertext.len;
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ciphertext.len = plainlen;
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writer->write_data(writer, this->payload);
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padding = writer->skip(writer, padding.len);
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generate_padding(padding);
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writer->write_uint8(writer, padding.len);
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writer->write_uint8(writer, this->next_header);
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DBG3(DBG_ESP, "ESP before encryption:\n payload = %B\n padding = %B\n "
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"padding length = %hhu, next header = %hhu", &this->payload, &padding,
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(u_int8_t)padding.len, this->next_header);
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/* encrypt the content inline */
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if (!crypter->encrypt(crypter, ciphertext, iv, NULL))
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{
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DBG1(DBG_ESP, "ESP encryption failed");
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writer->destroy(writer);
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return FAILED;
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}
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/* calculate signature */
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auth_data = writer->get_buf(writer);
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icv = writer->skip(writer, icv.len);
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if (!signer->get_signature(signer, auth_data, icv.ptr))
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{
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DBG1(DBG_ESP, "ESP encryption failed: signature generation failed");
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writer->destroy(writer);
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return FAILED;
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}
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DBG3(DBG_ESP, "ESP packet:\n SPI %.8x [seq %u]\n IV %B\n "
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"encrypted %B\n ICV %B", ntohl(spi), next_seqno, &iv,
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&ciphertext, &icv);
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this->packet_data = writer->extract_buf(writer);
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writer->destroy(writer);
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return SUCCESS;
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}
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METHOD(esp_packet_t, get_next_header, u_int8_t,
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private_esp_packet_t *this)
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{
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return this->next_header;
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}
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METHOD(esp_packet_t, get_payload, chunk_t,
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private_esp_packet_t *this)
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{
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return this->payload;
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}
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METHOD(esp_packet_t, get_packet_data, chunk_t,
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private_esp_packet_t *this)
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{
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return this->packet_data;
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}
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METHOD(esp_packet_t, get_source, host_t*,
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private_esp_packet_t *this)
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{
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return this->src;
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}
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METHOD(esp_packet_t, get_destination, host_t*,
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private_esp_packet_t *this)
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{
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return this->dst;
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}
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METHOD(esp_packet_t, destroy, void,
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private_esp_packet_t *this)
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{
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chunk_free(&this->payload);
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chunk_free(&this->packet_data);
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this->src->destroy(this->src);
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this->dst->destroy(this->dst);
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free(this);
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}
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static private_esp_packet_t *esp_packet_create_empty(host_t *src, host_t *dst)
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{
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private_esp_packet_t *this;
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INIT(this,
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.public = {
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.get_source = _get_source,
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.get_destination = _get_destination,
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.get_packet_data = _get_packet_data,
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.get_payload = _get_payload,
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.get_next_header = _get_next_header,
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.parse_header = _parse_header,
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.decrypt = _decrypt,
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.encrypt = _encrypt,
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.destroy = _destroy,
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},
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.src = src,
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.dst = dst,
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.next_header = IPPROTO_NONE,
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);
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return this;
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}
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/**
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* Described in header.
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*/
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esp_packet_t *esp_packet_create_from_packet(host_t *src, host_t *dst,
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chunk_t packet_data)
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{
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private_esp_packet_t *this;
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this = esp_packet_create_empty(src, dst);
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this->packet_data = packet_data;
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return &this->public;
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}
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/**
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* Described in header.
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*/
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esp_packet_t *esp_packet_create_from_payload(host_t *src, host_t *dst,
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chunk_t payload, u_int8_t next_header)
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{
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private_esp_packet_t *this;
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this = esp_packet_create_empty(src, dst);
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this->next_header = next_header;
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this->payload = payload;
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return &this->public;
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}
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