SecurityBlock.cpp

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/*
 * SecurityBlock.cpp
 *
 * Copyright (C) 2011 IBR, TU Braunschweig
 *
 * Written-by: Johannes Morgenroth <morgenroth@ibr.cs.tu-bs.de>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

#include "ibrdtn/config.h"
#include "ibrdtn/security/SecurityBlock.h"
#include "ibrdtn/security/MutableSerializer.h"
#include "ibrdtn/data/Bundle.h"
#include "ibrdtn/data/PayloadBlock.h"
#include "ibrdtn/data/ExtensionBlock.h"

#include <ibrcommon/Logger.h>
#include <cstdlib>
#include <openssl/rand.h>
#include <openssl/err.h>
#include <openssl/rsa.h>
#include <vector>

#ifdef __DEVELOPMENT_ASSERTIONS__
#include <cassert>
#endif

// include code for platform-independent endianess conversion
#include "ibrdtn/data/Endianess.h"

namespace dtn
{
        namespace security
        {
                const std::string SecurityBlock::TLVList::toString() const
                {
                        std::stringstream ss;

                        for (std::set<TLV>::const_iterator iter = begin(); iter != end(); ++iter)
                        {
                                ss << (*iter);
                        }

                        return ss.str();
                }

                dtn::data::Length SecurityBlock::TLVList::getLength() const
                {
                        return getPayloadLength();
                }

                dtn::data::Length SecurityBlock::TLVList::getPayloadLength() const
                {
                        dtn::data::Length len = 0;

                        for (std::set<SecurityBlock::TLV>::const_iterator iter = begin(); iter != end(); ++iter)
                        {
                                len += (*iter).getLength();
                        }

                        return len;
                }

                const std::string SecurityBlock::TLVList::get(SecurityBlock::TLV_TYPES type) const
                {
                        for (std::set<SecurityBlock::TLV>::const_iterator iter = begin(); iter != end(); ++iter)
                        {
                                if ((*iter).getType() == type)
                                {
                                        return (*iter).getValue();
                                }
                        }

                        throw ElementMissingException();
                }

                void SecurityBlock::TLVList::get(TLV_TYPES type, unsigned char *value, dtn::data::Length length) const
                {
                        const std::string data = get(type);

                        if (length < data.size())
                        {
                                ::memcpy(value, data.c_str(), length);
                        }
                        else
                        {
                                ::memcpy(value, data.c_str(), data.size());
                        }
                }

                void SecurityBlock::TLVList::set(SecurityBlock::TLV_TYPES type, std::string value)
                {
                        SecurityBlock::TLV tlv(type, value);

                        erase(tlv);
                        insert(tlv);
                }

                void SecurityBlock::TLVList::set(TLV_TYPES type, const unsigned char *value, dtn::data::Length length)
                {
                        const std::string data(reinterpret_cast<const char *>(value), length);
                        set(type, data);
                }

                void SecurityBlock::TLVList::remove(SecurityBlock::TLV_TYPES type)
                {
                        erase(SecurityBlock::TLV(type, ""));
                }

                const std::string SecurityBlock::TLV::getValue() const
                {
                        return _value;
                }

                SecurityBlock::TLV_TYPES SecurityBlock::TLV::getType() const
                {
                        return _type;
                }

                dtn::data::Length SecurityBlock::TLV::getLength() const
                {
                        return _value.getLength() + sizeof(char);
                }

                std::ostream& operator<<(std::ostream &stream, const SecurityBlock::TLVList &tlvlist)
                {
                        dtn::data::Number length(tlvlist.getPayloadLength());
                        stream << length;

                        for (std::set<SecurityBlock::TLV>::const_iterator iter = tlvlist.begin(); iter != tlvlist.end(); ++iter)
                        {
                                stream << (*iter);
                        }
                        return stream;
                }

                std::istream& operator>>(std::istream &stream, SecurityBlock::TLVList &tlvlist)
                {
                        dtn::data::Number length;
                        stream >> length;
                        dtn::data::Length read_length = 0;

                        while (length > read_length)
                        {
                                SecurityBlock::TLV tlv;
                                stream >> tlv;
                                tlvlist.insert(tlv);
                                read_length += tlv.getLength();
                        }

                        return stream;
                }

                bool SecurityBlock::TLV::operator<(const SecurityBlock::TLV &tlv) const
                {
                        return (_type < tlv._type);
                }

                bool SecurityBlock::TLV::operator==(const SecurityBlock::TLV &tlv) const
                {
                        return (_type == tlv._type);
                }

                std::ostream& operator<<(std::ostream &stream, const SecurityBlock::TLV &tlv)
                {
                        stream.put((char)tlv._type);
                        stream << tlv._value;
                        return stream;
                }

                std::istream& operator>>(std::istream &stream, SecurityBlock::TLV &tlv)
                {
                        char tlv_type;
                        stream.get(tlv_type); tlv._type = SecurityBlock::TLV_TYPES(tlv_type);
                        stream >> tlv._value;
                        return stream;
                }

                SecurityBlock::SecurityBlock(const dtn::security::SecurityBlock::BLOCK_TYPES type, const dtn::security::SecurityBlock::CIPHERSUITE_IDS id)
                : Block(type), _ciphersuite_id(id), _ciphersuite_flags(0), _correlator(0)
                {

                }

                SecurityBlock::SecurityBlock(const dtn::security::SecurityBlock::BLOCK_TYPES type)
                : Block(type), _ciphersuite_id(0), _ciphersuite_flags(0), _correlator(0)
                {

                }

                SecurityBlock::~SecurityBlock()
                {
                }

                void SecurityBlock::store_security_references()
                {
                        // clear the EID list
                        _eids.clear();

                        // first the security source
                        if (_security_source == dtn::data::EID())
                        {
                                _ciphersuite_flags &= ~(SecurityBlock::CONTAINS_SECURITY_SOURCE);
                        }
                        else
                        {
                                _ciphersuite_flags |= SecurityBlock::CONTAINS_SECURITY_SOURCE;
                                _eids.push_back(_security_source);
                        }

                        // then the destination
                        if (_security_destination == dtn::data::EID())
                        {
                                _ciphersuite_flags &= ~(SecurityBlock::CONTAINS_SECURITY_DESTINATION);
                        }
                        else
                        {
                                _ciphersuite_flags |= SecurityBlock::CONTAINS_SECURITY_DESTINATION;
                                _eids.push_back(_security_destination);
                        }

                        if (_eids.size() > 0)
                        {
                                set(Block::BLOCK_CONTAINS_EIDS, true);
                        }
                        else
                        {
                                set(Block::BLOCK_CONTAINS_EIDS, false);
                        }
                }

                const dtn::data::EID SecurityBlock::getSecuritySource() const
                {
                        return _security_source;
                }

                const dtn::data::EID SecurityBlock::getSecurityDestination() const
                {
                        return _security_destination;
                }

                void SecurityBlock::setSecuritySource(const dtn::data::EID &source)
                {
                        _security_source = source;
                        store_security_references();
                }

                void SecurityBlock::setSecurityDestination(const dtn::data::EID &destination)
                {
                        _security_destination = destination;
                        store_security_references();
                }

                void SecurityBlock::setCiphersuiteId(const CIPHERSUITE_IDS id)
                {
                        _ciphersuite_id = static_cast<uint64_t>(id);
                }

                void SecurityBlock::setCorrelator(const dtn::data::Number &corr)
                {
                        _correlator = corr;
                        _ciphersuite_flags |= SecurityBlock::CONTAINS_CORRELATOR;
                }

                bool SecurityBlock::isCorrelatorPresent(const dtn::data::Bundle& bundle, const dtn::data::Number &correlator)
                {
                        bool return_val = false;
                        for (dtn::data::Bundle::const_iterator it = bundle.begin(); it != bundle.end() && !return_val; ++it)
                        {
                                const dtn::data::Block &b = (**it);
                                const dtn::data::block_t type = b.getType();
                                if (type == BUNDLE_AUTHENTICATION_BLOCK
                                        || type == PAYLOAD_INTEGRITY_BLOCK
                                        || type == PAYLOAD_CONFIDENTIAL_BLOCK
                                        || type == EXTENSION_SECURITY_BLOCK)
                                return_val = static_cast<const SecurityBlock&>(b)._correlator == correlator;
                        }
                        return return_val;
                }

                dtn::data::Number SecurityBlock::createCorrelatorValue(const dtn::data::Bundle& bundle)
                {
                        dtn::data::Number corr;
                        corr.random();

                        while (isCorrelatorPresent(bundle, corr)) {
                                corr.random();
                        }
                        return corr;
                }

                dtn::data::Length SecurityBlock::getLength() const
                {
                        dtn::data::Length length = _ciphersuite_id.getLength()
                                + _ciphersuite_flags.getLength();

                        if (_ciphersuite_flags & CONTAINS_CORRELATOR)
                        {
                                length += _correlator.getLength();
                        }

                        if (_ciphersuite_flags & CONTAINS_CIPHERSUITE_PARAMS)
                        {
                                const dtn::data::Number size(_ciphersuite_params.getLength());
                                length += size.getLength() + size.get<dtn::data::Length>();
                        }

                        if (_ciphersuite_flags & CONTAINS_SECURITY_RESULT)
                        {
                                const dtn::data::Number size(getSecurityResultSize());
                                length += size.getLength() + size.get<dtn::data::Length>();
                        }

                        return length;
                }

                dtn::data::Length SecurityBlock::getLength_mutable() const
                {
                        // ciphersuite_id
                        dtn::data::Length length = MutableSerializer::sdnv_size;

                        // ciphersuite_flags
                        length += MutableSerializer::sdnv_size;

                        // correlator
                        if (_ciphersuite_flags & CONTAINS_CORRELATOR)
                        {
                                length += MutableSerializer::sdnv_size;
                        }

                        // ciphersuite parameters
                        if (_ciphersuite_flags & CONTAINS_CIPHERSUITE_PARAMS)
                        {
                                length += MutableSerializer::sdnv_size;
                                length += _ciphersuite_params.getLength();
                        }
                        // security result
                        if (_ciphersuite_flags & CONTAINS_SECURITY_RESULT)
                        {
                                length += MutableSerializer::sdnv_size + getSecurityResultSize();
                        }

                        return length;
                }

                std::ostream& SecurityBlock::serialize(std::ostream &stream, dtn::data::Length &) const
                {
                        stream << _ciphersuite_id << _ciphersuite_flags;

                        if (_ciphersuite_flags & CONTAINS_CORRELATOR)
                        {
                                stream << _correlator;
                        }

                        if (_ciphersuite_flags & CONTAINS_CIPHERSUITE_PARAMS)
                        {
                                stream << _ciphersuite_params;
                        }

                        if (_ciphersuite_flags & CONTAINS_SECURITY_RESULT)
                        {
                                stream << _security_result;
                        }

                        return stream;
                }

                std::ostream& SecurityBlock::serialize_strict(std::ostream &stream, dtn::data::Length &) const
                {
                        stream << _ciphersuite_id << _ciphersuite_flags;

                        if (_ciphersuite_flags & CONTAINS_CORRELATOR)
                        {
                                stream << _correlator;
                        }

                        if (_ciphersuite_flags & CONTAINS_CIPHERSUITE_PARAMS)
                        {
                                stream << _ciphersuite_params;
                        }

                        if (_ciphersuite_flags & CONTAINS_SECURITY_RESULT)
                        {
                                stream << dtn::data::Number(getSecurityResultSize());
                        }

                        return stream;
                }

                std::istream& SecurityBlock::deserialize(std::istream &stream, const dtn::data::Length&)
                {
#ifdef __DEVELOPMENT_ASSERTIONS__
                        // recheck blocktype. if blocktype is set wrong, this will be a huge fail
                        assert(_blocktype == BUNDLE_AUTHENTICATION_BLOCK || _blocktype == PAYLOAD_INTEGRITY_BLOCK || _blocktype == PAYLOAD_CONFIDENTIAL_BLOCK || _blocktype == EXTENSION_SECURITY_BLOCK);
#endif

                        stream >> _ciphersuite_id >> _ciphersuite_flags;

#ifdef __DEVELOPMENT_ASSERTIONS__
                        // recheck ciphersuite_id
                        assert(_ciphersuite_id == BAB_HMAC || _ciphersuite_id == PIB_RSA_SHA256 || _ciphersuite_id == PCB_RSA_AES128_PAYLOAD_PIB_PCB || _ciphersuite_id == ESB_RSA_AES128_EXT);
                        // recheck ciphersuite_flags, could be more exhaustive
                        assert(_ciphersuite_flags < 32);
#endif

                        // copy security source and destination
                        if (_ciphersuite_flags & SecurityBlock::CONTAINS_SECURITY_SOURCE)
                        {
                                if (_eids.size() == 0)
                                        throw dtn::SerializationFailedException("ciphersuite flags indicate a security source, but it is not present");

                                _security_source = _eids.front();
                        }

                        if (_ciphersuite_flags & SecurityBlock::CONTAINS_SECURITY_DESTINATION)
                        {
                                if (_ciphersuite_flags & SecurityBlock::CONTAINS_SECURITY_SOURCE)
                                {
                                        if (_eids.size() < 2)
                                                throw dtn::SerializationFailedException("ciphersuite flags indicate a security destination, but it is not present");

                                        _security_destination = *(++_eids.begin());
                                }
                                else
                                {
                                        if (_eids.size() == 0)
                                                throw dtn::SerializationFailedException("ciphersuite flags indicate a security destination, but it is not present");

                                        _security_destination = _eids.front();
                                }
                        }

                        if (_ciphersuite_flags & CONTAINS_CORRELATOR)
                        {
                                stream >> _correlator;
                        }
                        if (_ciphersuite_flags & CONTAINS_CIPHERSUITE_PARAMS)
                        {
                                stream >> _ciphersuite_params;
#ifdef __DEVELOPMENT_ASSERTIONS__
                                assert(_ciphersuite_params.getLength() > 0);
#endif
                        }

                        if (_ciphersuite_flags & CONTAINS_SECURITY_RESULT)
                        {
                                stream >> _security_result;
#ifdef __DEVELOPMENT_ASSERTIONS__
                                assert(_security_result.getLength() > 0);
#endif
                        }

                        return stream;
                }

                dtn::security::MutableSerializer& SecurityBlock::serialize_mutable(dtn::security::MutableSerializer &serializer, bool include_security_result) const
                {
                        serializer << _ciphersuite_id;
                        serializer << _ciphersuite_flags;

                        if (_ciphersuite_flags & CONTAINS_CORRELATOR)
                        {
                                serializer << _correlator;
                        }

                        if (_ciphersuite_flags & CONTAINS_CIPHERSUITE_PARAMS)
                        {
                                serializer << _ciphersuite_params;
                        }

                        if (_ciphersuite_flags & CONTAINS_SECURITY_RESULT)
                        {
                                if (include_security_result) {
                                        serializer << _security_result;
                                } else {
                                        serializer << dtn::data::Number(getSecurityResultSize());
                                }
                        }

                        return serializer;
                }

                dtn::data::Length SecurityBlock::getSecurityResultSize() const
                {
#ifdef __DEVELOPMENT_ASSERTIONS__
                        assert(_security_result.getLength() != 0);
#endif
                        return _security_result.getLength();
                }

                void SecurityBlock::createSaltAndKey(uint32_t& salt, unsigned char* key, dtn::data::Length key_size)
                {

                        if (!RAND_bytes(reinterpret_cast<unsigned char *>(&salt), sizeof(uint32_t)))
                        {
                                IBRCOMMON_LOGGER_ex(critical) << "failed to generate salt. maybe /dev/urandom is missing for seeding the PRNG" << IBRCOMMON_LOGGER_ENDL;
                                ERR_print_errors_fp(stderr);
                        }
                        if (!RAND_bytes(key, static_cast<int>(key_size)))
                        {
                                IBRCOMMON_LOGGER_ex(critical) << "failed to generate key. maybe /dev/urandom is missing for seeding the PRNG" << IBRCOMMON_LOGGER_ENDL;
                                ERR_print_errors_fp(stderr);
                        }
                }

                void SecurityBlock::addKey(TLVList& security_parameter, unsigned char const * const key, dtn::data::Length key_size, RSA * rsa)
                {
                        // encrypt the ephemeral key and place it in _ciphersuite_params
#ifdef __DEVELOPMENT_ASSERTIONS__
                        assert(key_size < (dtn::data::Length)RSA_size(rsa)-41);
#endif
                        std::vector<unsigned char> encrypted_key(RSA_size(rsa));
                        int encrypted_key_len = RSA_public_encrypt(static_cast<int>(key_size), key, &encrypted_key[0], rsa, RSA_PKCS1_OAEP_PADDING);
                        if (encrypted_key_len == -1)
                        {
                                IBRCOMMON_LOGGER_ex(critical) << "failed to encrypt the symmetric AES key" << IBRCOMMON_LOGGER_ENDL;
                                ERR_print_errors_fp(stderr);
                                return;
                        }
                        security_parameter.set(SecurityBlock::key_information, std::string(reinterpret_cast<char *>(&encrypted_key[0]), encrypted_key_len));
                }

                bool SecurityBlock::getKey(const TLVList& security_parameter, unsigned char * key, dtn::data::Length key_size, RSA * rsa)
                {
                        std::string key_string = security_parameter.get(SecurityBlock::key_information);
                        // get key, convert with reinterpret_cast
                        const unsigned char *encrypted_key = reinterpret_cast<const unsigned char*>(key_string.c_str());
                        std::vector<unsigned char> the_key(RSA_size(rsa));
                        RSA_blinding_on(rsa, NULL);
                        int plaintext_key_len = RSA_private_decrypt(static_cast<int>(key_string.size()), encrypted_key, &the_key[0], rsa, RSA_PKCS1_OAEP_PADDING);
                        RSA_blinding_off(rsa);
                        if (plaintext_key_len == -1)
                        {
                                IBRCOMMON_LOGGER_ex(critical) << "failed to decrypt the symmetric AES key" << IBRCOMMON_LOGGER_ENDL;
                                ERR_print_errors_fp(stderr);
                                return false;
                        }
#ifdef __DEVELOPMENT_ASSERTIONS__
                        assert((dtn::data::Length)plaintext_key_len == key_size);
#endif
                        std::copy(&the_key[0], &the_key[key_size], key);
                        return true;
                }

                void SecurityBlock::copyEID(const Block& from, Block& to, dtn::data::Length skip)
                {
                        // take eid list, getEIDList() is broken
                        std::list<dtn::data::EID> their_eids = from.getEIDList();
                        std::list<dtn::data::EID>::iterator it = their_eids.begin();

                        while (it != their_eids.end() && skip > 0)
                        {
                                skip--;
                                ++it;
                        }

                        for (; it != their_eids.end(); ++it)
                                to.addEID(*it);
                }

                void SecurityBlock::addSalt(TLVList& security_parameters, const uint32_t &salt)
                {
                        uint32_t nsalt = GUINT32_TO_BE(salt);
                        security_parameters.set(SecurityBlock::salt, (const unsigned char*)&nsalt, sizeof(nsalt));
                }

                uint32_t SecurityBlock::getSalt(const TLVList& security_parameters)
                {
                        uint32_t nsalt = 0;
                        security_parameters.get(SecurityBlock::salt, (unsigned char*)&nsalt, sizeof(nsalt));
                        return GUINT32_TO_BE(nsalt);
                }

                void SecurityBlock::decryptBlock(dtn::data::Bundle& bundle, dtn::data::Bundle::iterator &it, uint32_t salt, const unsigned char key[ibrcommon::AES128Stream::key_size_in_bytes])
                {
                        const dtn::security::SecurityBlock &block = dynamic_cast<const dtn::security::SecurityBlock&>(**it);

                        // the array for the extracted tag
                        unsigned char tag[ibrcommon::AES128Stream::tag_len];

                        // the array for the extracted iv
                        unsigned char iv[ibrcommon::AES128Stream::iv_len];

                        // get iv, convert with reinterpret_cast
                        block._ciphersuite_params.get(SecurityBlock::initialization_vector, iv, ibrcommon::AES128Stream::iv_len);

                        // get data and tag, the last tag_len bytes are the tag. cut them of and reinterpret_cast
                        std::string block_data = block._security_result.get(SecurityBlock::encapsulated_block);

                        // create a pointer to the tag begin
                        const char *tag_p = block_data.c_str() + (block_data.size() - ibrcommon::AES128Stream::tag_len);

                        // copy the tag
                        ::memcpy(tag, tag_p, ibrcommon::AES128Stream::tag_len);

                        // strip off the tag from block data
                        block_data.resize(block_data.size() - ibrcommon::AES128Stream::tag_len);

                        // decrypt block
                        std::stringstream plaintext;
                        ibrcommon::AES128Stream decrypt(ibrcommon::CipherStream::CIPHER_DECRYPT, plaintext, key, salt, iv);
                        decrypt << block_data << std::flush;

                        // verify the decrypt tag
                        if (!decrypt.verify(tag))
                        {
                                throw DecryptException("decryption of block failed - tag is bad");
                        }

                        // deserialize block
                        dtn::data::DefaultDeserializer ddser(plaintext);

                        // peek the block type
                        dtn::data::block_t block_type = (dtn::data::block_t)plaintext.peek();

                        // get the position of "block"
                        dtn::data::Bundle::iterator b_it = bundle.find(block);

                        if (block_type == dtn::data::PayloadBlock::BLOCK_TYPE)
                        {
                                dtn::data::PayloadBlock &plaintext_block = bundle.insert<dtn::data::PayloadBlock>(b_it);
                                ddser >> plaintext_block;
                        }
                        else
                        {
                                try {
                                        dtn::data::ExtensionBlock::Factory &f = dtn::data::ExtensionBlock::Factory::get(block_type);
                                        dtn::data::Block &plaintext_block = bundle.insert(b_it, f);
                                        ddser >> plaintext_block;

                                        plaintext_block.clearEIDs();

                                        // copy eids
                                        // remove security_source and destination
                                        dtn::data::Length skip = 0;
                                        if (block._ciphersuite_flags & SecurityBlock::CONTAINS_SECURITY_DESTINATION)
                                                skip++;
                                        if (block._ciphersuite_flags & SecurityBlock::CONTAINS_SECURITY_SOURCE)
                                                skip++;
                                        copyEID(plaintext_block, plaintext_block, skip);

                                } catch (const ibrcommon::Exception &ex) {
                                        dtn::data::ExtensionBlock &plaintext_block = bundle.insert<dtn::data::ExtensionBlock>(b_it);
                                        ddser >> plaintext_block;

                                        plaintext_block.clearEIDs();

                                        // copy eids
                                        // remove security_source and destination
                                        dtn::data::Length skip = 0;
                                        if (block._ciphersuite_flags & SecurityBlock::CONTAINS_SECURITY_DESTINATION)
                                                skip++;
                                        if (block._ciphersuite_flags & SecurityBlock::CONTAINS_SECURITY_SOURCE)
                                                skip++;
                                        copyEID(plaintext_block, plaintext_block, skip);
                                }
                        }

                        bundle.remove(block);
                }

                void SecurityBlock::addFragmentRange(TLVList& ciphersuite_params, const dtn::data::Number &offset, const dtn::data::Number &range)
                {
                        std::stringstream ss;
                        ss << offset << range;

                        ciphersuite_params.set(SecurityBlock::fragment_range, ss.str());
                }

                bool SecurityBlock::isSecuritySource(const dtn::data::Bundle& bundle, const dtn::data::EID& eid) const
                {
                        IBRCOMMON_LOGGER_DEBUG_TAG("SecurityBlock", 30) << "check security source: " << getSecuritySource(bundle).getString() << " == " << eid.getNode().getString() << IBRCOMMON_LOGGER_ENDL;
                        return getSecuritySource(bundle).sameHost(eid);
                }

                bool SecurityBlock::isSecurityDestination(const dtn::data::Bundle& bundle, const dtn::data::EID& eid) const
                {
                        IBRCOMMON_LOGGER_DEBUG_TAG("SecurityBlock", 30) << "check security destination: " << getSecurityDestination(bundle).getString() << " == " << eid.getNode().getString() << IBRCOMMON_LOGGER_ENDL;
                        return getSecurityDestination(bundle).sameHost(eid);
                }
                
                const dtn::data::EID SecurityBlock::getSecuritySource(const dtn::data::Bundle& bundle) const
                {
                        const dtn::data::EID source = getSecuritySource();
                        if (source.isNone())
                                return bundle.source.getNode();
                        return source;
                }

                const dtn::data::EID SecurityBlock::getSecurityDestination(const dtn::data::Bundle& bundle) const
                {
                        const dtn::data::EID destination = getSecurityDestination();
                        if (destination.isNone())
                                return bundle.destination.getNode();
                        return destination;
                }
        }
}