kea/src/lib/dhcp/pkt4.cc

// Copyright (C) 2011-2016 Internet Systems Consortium, Inc. ("ISC")
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

#include <config.h>
#include <asiolink/io_address.h>
#include <dhcp/dhcp4.h>
#include <dhcp/libdhcp++.h>
#include <dhcp/option_int.h>
#include <dhcp/pkt4.h>
#include <exceptions/exceptions.h>

#include <algorithm>
#include <iostream>
#include <sstream>

using namespace std;
using namespace isc::dhcp;
using namespace isc::asiolink;

namespace {

/// @brief Default address used in Pkt4 constructor
const IOAddress DEFAULT_ADDRESS("0.0.0.0");
}

namespace isc {
namespace dhcp {

Pkt4::Pkt4(uint8_t msg_type, uint32_t transid)
     :Pkt(transid, DEFAULT_ADDRESS, DEFAULT_ADDRESS, DHCP4_SERVER_PORT,
          DHCP4_CLIENT_PORT),
      op_(DHCPTypeToBootpType(msg_type)),
      hwaddr_(new HWAddr()),
      hops_(0),
      secs_(0),
      flags_(0),
      ciaddr_(DEFAULT_ADDRESS),
      yiaddr_(DEFAULT_ADDRESS),
      siaddr_(DEFAULT_ADDRESS),
      giaddr_(DEFAULT_ADDRESS)
{
    memset(sname_, 0, MAX_SNAME_LEN);
    memset(file_, 0, MAX_FILE_LEN);

    setType(msg_type);
}

Pkt4::Pkt4(const uint8_t* data, size_t len)
     :Pkt(data, len, DEFAULT_ADDRESS, DEFAULT_ADDRESS, DHCP4_SERVER_PORT,
          DHCP4_CLIENT_PORT),
      op_(BOOTREQUEST),
      hwaddr_(new HWAddr()),
      hops_(0),
      secs_(0),
      flags_(0),
      ciaddr_(DEFAULT_ADDRESS),
      yiaddr_(DEFAULT_ADDRESS),
      siaddr_(DEFAULT_ADDRESS),
      giaddr_(DEFAULT_ADDRESS)
{

    if (len < DHCPV4_PKT_HDR_LEN) {
        isc_throw(OutOfRange, "Truncated DHCPv4 packet (len=" << len
                  << ") received, at least " << DHCPV4_PKT_HDR_LEN
                  << " is expected.");
    }
    memset(sname_, 0, MAX_SNAME_LEN);
    memset(file_, 0, MAX_FILE_LEN);
}

size_t
Pkt4::len() {
    size_t length = DHCPV4_PKT_HDR_LEN; // DHCPv4 header

    // ... and sum of lengths of all options
    for (OptionCollection::const_iterator it = options_.begin();
         it != options_.end();
         ++it) {
        length += (*it).second->len();
    }

    return (length);
}

void
Pkt4::pack() {
    if (!hwaddr_) {
        isc_throw(InvalidOperation, "Can't build Pkt4 packet. HWAddr not set.");
    }

    // Clear the output buffer to make sure that consecutive calls to pack()
    // will not result in concatenation of multiple packet copies.
    buffer_out_.clear();

    try {
        size_t hw_len = hwaddr_->hwaddr_.size();

        buffer_out_.writeUint8(op_);
        buffer_out_.writeUint8(hwaddr_->htype_);
        buffer_out_.writeUint8(hw_len < MAX_CHADDR_LEN ?
                              hw_len : MAX_CHADDR_LEN);
        buffer_out_.writeUint8(hops_);
        buffer_out_.writeUint32(transid_);
        buffer_out_.writeUint16(secs_);
        buffer_out_.writeUint16(flags_);
        buffer_out_.writeUint32(ciaddr_);
        buffer_out_.writeUint32(yiaddr_);
        buffer_out_.writeUint32(siaddr_);
        buffer_out_.writeUint32(giaddr_);


        if ((hw_len > 0) && (hw_len <= MAX_CHADDR_LEN)) {
            // write up to 16 bytes of the hardware address (CHADDR field is 16
            // bytes long in DHCPv4 message).
            buffer_out_.writeData(&hwaddr_->hwaddr_[0],
                                 (hw_len < MAX_CHADDR_LEN ?
                                  hw_len : MAX_CHADDR_LEN) );
            hw_len = MAX_CHADDR_LEN - hw_len;
        } else {
            hw_len = MAX_CHADDR_LEN;
        }

        // write (len) bytes of padding
        if (hw_len > 0) {
            vector<uint8_t> zeros(hw_len, 0);
            buffer_out_.writeData(&zeros[0], hw_len);
        }

        buffer_out_.writeData(sname_, MAX_SNAME_LEN);
        buffer_out_.writeData(file_, MAX_FILE_LEN);

        // write DHCP magic cookie
        buffer_out_.writeUint32(DHCP_OPTIONS_COOKIE);

        LibDHCP::packOptions4(buffer_out_, options_);

        // add END option that indicates end of options
        // (End option is very simple, just a 255 octet)
         buffer_out_.writeUint8(DHO_END);
     } catch(const Exception& e) {
        // An exception is thrown and message will be written to Logger
         isc_throw(InvalidOperation, e.what());
    }
}

void
Pkt4::unpack() {

    // input buffer (used during message reception)
    isc::util::InputBuffer buffer_in(&data_[0], data_.size());

    if (buffer_in.getLength() < DHCPV4_PKT_HDR_LEN) {
        isc_throw(OutOfRange, "Received truncated DHCPv4 packet (len="
                  << buffer_in.getLength() << " received, at least "
                  << DHCPV4_PKT_HDR_LEN << "is expected");
    }

    op_ = buffer_in.readUint8();
    uint8_t htype = buffer_in.readUint8();
    uint8_t hlen = buffer_in.readUint8();
    hops_ = buffer_in.readUint8();
    transid_ = buffer_in.readUint32();
    secs_ = buffer_in.readUint16();
    flags_ = buffer_in.readUint16();
    ciaddr_ = IOAddress(buffer_in.readUint32());
    yiaddr_ = IOAddress(buffer_in.readUint32());
    siaddr_ = IOAddress(buffer_in.readUint32());
    giaddr_ = IOAddress(buffer_in.readUint32());

    vector<uint8_t> hw_addr(MAX_CHADDR_LEN, 0);
    buffer_in.readVector(hw_addr, MAX_CHADDR_LEN);
    buffer_in.readData(sname_, MAX_SNAME_LEN);
    buffer_in.readData(file_, MAX_FILE_LEN);

    hw_addr.resize(hlen);

    hwaddr_ = HWAddrPtr(new HWAddr(hw_addr, htype));

    if (buffer_in.getLength() == buffer_in.getPosition()) {
        // this is *NOT* DHCP packet. It does not have any DHCPv4 options. In
        // particular, it does not have magic cookie, a 4 byte sequence that
        // differentiates between DHCP and BOOTP packets.
        isc_throw(InvalidOperation, "Received BOOTP packet. BOOTP is not supported.");
    }

    if (buffer_in.getLength() - buffer_in.getPosition() < 4) {
      // there is not enough data to hold magic DHCP cookie
      isc_throw(Unexpected, "Truncated or no DHCP packet.");
    }

    uint32_t magic = buffer_in.readUint32();
    if (magic != DHCP_OPTIONS_COOKIE) {
      isc_throw(Unexpected, "Invalid or missing DHCP magic cookie");
    }

    size_t opts_len = buffer_in.getLength() - buffer_in.getPosition();
    vector<uint8_t> opts_buffer;

    // Use readVector because a function which parses option requires
    // a vector as an input.
    buffer_in.readVector(opts_buffer, opts_len);

    size_t offset = LibDHCP::unpackOptions4(opts_buffer, "dhcp4", options_);

    // If offset is not equal to the size and there is no DHO_END,
    // then something is wrong here. We either parsed past input
    // buffer (bug in our code) or we haven't parsed everything
    // (received trailing garbage or truncated option).
    //
    // Invoking Jon Postel's law here: be conservative in what you send, and be
    // liberal in what you accept. There's no easy way to log something from
    // libdhcp++ library, so we just choose to be silent about remaining
    // bytes. We also need to quell compiler warning about unused offset
    // variable.
    //
    // if ((offset != size) && (opts_buffer[offset] != DHO_END)) {
    //        isc_throw(BadValue, "Received DHCPv6 buffer of size " << size
    //                  << ", were able to parse " << offset << " bytes.");
    // }
    (void)offset;

    // No need to call check() here. There are thorough tests for this
    // later (see Dhcp4Srv::accept()). We want to drop the packet later,
    // so we'll be able to log more detailed drop reason.
}

uint8_t Pkt4::getType() const {
    OptionPtr generic = getNonCopiedOption(DHO_DHCP_MESSAGE_TYPE);
    if (!generic) {
        return (DHCP_NOTYPE);
    }

    // Check if Message Type is specified as OptionInt<uint8_t>
    boost::shared_ptr<OptionInt<uint8_t> > type_opt =
        boost::dynamic_pointer_cast<OptionInt<uint8_t> >(generic);
    if (type_opt) {
        return (type_opt->getValue());
    }

    // Try to use it as generic option
    return (generic->getUint8());
}

void Pkt4::setType(uint8_t dhcp_type) {
    OptionPtr opt = getNonCopiedOption(DHO_DHCP_MESSAGE_TYPE);
    if (opt) {

        // There is message type option already, update it. It seems that
        // we do have two types of objects representing message-type option.
        // It would be more preferable to use only one type, but there's no
        // easy way to enforce it.
        //
        // One is an instance of the Option class. It stores type in
        // Option::data_, so Option::setUint8() and Option::getUint8() can be
        // used. The other one is an instance of OptionInt<uint8_t> and
        // it stores message type as integer, hence
        // OptionInt<uint8_t>::getValue() and OptionInt<uint8_t>::setValue()
        // should be used.
        boost::shared_ptr<OptionInt<uint8_t> > type_opt =
            boost::dynamic_pointer_cast<OptionInt<uint8_t> >(opt);
        if (type_opt) {
            type_opt->setValue(dhcp_type);
        } else {
            opt->setUint8(dhcp_type);
        }
    } else {
        // There is no message type option yet, add it
        opt.reset(new OptionInt<uint8_t>(Option::V4, DHO_DHCP_MESSAGE_TYPE,
                                         dhcp_type));
        addOption(opt);
    }
}

const char*
Pkt4::getName(const uint8_t type) {
    static const char* DHCPDISCOVER_NAME = "DHCPDISCOVER";
    static const char* DHCPOFFER_NAME = "DHCPOFFER";
    static const char* DHCPREQUEST_NAME = "DHCPREQUEST";
    static const char* DHCPDECLINE_NAME = "DHCPDECLINE";
    static const char* DHCPACK_NAME = "DHCPACK";
    static const char* DHCPNAK_NAME = "DHCPNAK";
    static const char* DHCPRELEASE_NAME = "DHCPRELEASE";
    static const char* DHCPINFORM_NAME = "DHCPINFORM";
    static const char* UNKNOWN_NAME = "UNKNOWN";

    switch (type) {
        case DHCPDISCOVER:
            return (DHCPDISCOVER_NAME);

        case DHCPOFFER:
            return (DHCPOFFER_NAME);

        case DHCPREQUEST:
            return (DHCPREQUEST_NAME);

        case DHCPDECLINE:
            return (DHCPDECLINE_NAME);

        case DHCPACK:
            return (DHCPACK_NAME);

        case DHCPNAK:
            return (DHCPNAK_NAME);

        case DHCPRELEASE:
            return (DHCPRELEASE_NAME);

        case DHCPINFORM:
            return (DHCPINFORM_NAME);

        default:
            ;
    }
    return (UNKNOWN_NAME);
}

const char*
Pkt4::getName() const {
    // getType() is now exception safe. Even if there's no option 53 (message
    // type), it now returns 0 rather than throw. getName() is able to handle
    // 0 and unknown message types.
    return (Pkt4::getName(getType()));
}

std::string
Pkt4::getLabel() const {

    /// @todo If and when client id is extracted into Pkt4, this method should
    /// use the instance member rather than fetch it every time.
    std::string suffix;
    ClientIdPtr client_id;
    OptionPtr client_opt = getNonCopiedOption(DHO_DHCP_CLIENT_IDENTIFIER);
    if (client_opt) {
        try {
            client_id = ClientIdPtr(new ClientId(client_opt->getData()));
        } catch (...) {
            // ClientId may throw if the client-id is too short.
            suffix = " (malformed client-id)";
        }
    }

    std::ostringstream label;
    try {
        label << makeLabel(hwaddr_, client_id, transid_);
    } catch (...) {
        // This should not happen with the current code, but we may add extra
        // sanity checks in the future that would possibly throw if
        // the hwaddr length is 0.
        label << " (malformed hw address)";
    }

    label << suffix;
    return (label.str());
}

std::string
Pkt4::makeLabel(const HWAddrPtr& hwaddr, const ClientIdPtr& client_id,
                const uint32_t transid) {
    // Create label with HW address and client identifier.
    stringstream label;
    label << makeLabel(hwaddr, client_id);

    // Append transaction id.
    label << ", tid=0x" << hex << transid << dec;

    return label.str();
}

std::string
Pkt4::makeLabel(const HWAddrPtr& hwaddr, const ClientIdPtr& client_id) {
    stringstream label;
    label << "[" << (hwaddr ? hwaddr->toText() : "no hwaddr info")
          << "], cid=[" << (client_id ? client_id->toText() : "no info")
          << "]";

    return label.str();
}

std::string
Pkt4::toText() const {
    stringstream output;
    output << "local_address=" << local_addr_ << ":" << local_port_
        << ", remote_adress=" << remote_addr_
        << ":" << remote_port_ << ", msg_type=";

    // Try to obtain message type.
    uint8_t msg_type = getType();
    if (msg_type != DHCP_NOTYPE) {
        output << getName(msg_type) << " (" << static_cast<int>(msg_type) << ")";
    } else {
        // Message Type option is missing.
        output << "(missing)";
    }

    output << ", transid=0x" << hex << transid_ << dec;

    if (!options_.empty()) {
        output << "," << std::endl << "options:";
        for (isc::dhcp::OptionCollection::const_iterator opt = options_.begin();
             opt != options_.end(); ++opt) {
            try {
                output << std::endl << opt->second->toText(2);
            } catch (...) {
                output << "(unknown)" << std::endl;
            }
        }

    } else {
        output << ", message contains no options";
    }

    return (output.str());
}

void
Pkt4::setHWAddr(uint8_t htype, uint8_t hlen,
                const std::vector<uint8_t>& mac_addr) {
    setHWAddrMember(htype, hlen, mac_addr, hwaddr_);
}

void
Pkt4::setHWAddr(const HWAddrPtr& addr) {
    if (!addr) {
        isc_throw(BadValue, "Setting DHCPv4 chaddr field to NULL"
                  << " is forbidden");
    }
    hwaddr_ = addr;
}

void
Pkt4::setHWAddrMember(const uint8_t htype, const uint8_t hlen,
                      const std::vector<uint8_t>& mac_addr,
                      HWAddrPtr& hw_addr) {
    /// @todo Rewrite this once support for client-identifier option
    /// is implemented (ticket 1228?)
    if (hlen > MAX_CHADDR_LEN) {
        isc_throw(OutOfRange, "Hardware address (len=" << hlen
                  << " too long. Max " << MAX_CHADDR_LEN << " supported.");

    } else if (mac_addr.empty() && (hlen > 0) ) {
        isc_throw(OutOfRange, "Invalid HW Address specified");
    }

    hw_addr.reset(new HWAddr(mac_addr, htype));
}

void
Pkt4::setLocalHWAddr(const uint8_t htype, const uint8_t hlen,
                      const std::vector<uint8_t>& mac_addr) {
    setHWAddrMember(htype, hlen, mac_addr, local_hwaddr_);
}

void
Pkt4::setLocalHWAddr(const HWAddrPtr& addr) {
    if (!addr) {
        isc_throw(BadValue, "Setting local HW address to NULL is"
                  << " forbidden.");
    }
    local_hwaddr_ = addr;
}

void
Pkt4::setSname(const uint8_t* sname, size_t snameLen /*= MAX_SNAME_LEN*/) {
    if (snameLen > MAX_SNAME_LEN) {
        isc_throw(OutOfRange, "sname field (len=" << snameLen
                  << ") too long, Max " << MAX_SNAME_LEN << " supported.");

    } else if (sname == NULL) {
        isc_throw(InvalidParameter, "Invalid sname specified");
    }

    std::copy(sname, (sname + snameLen), sname_);
    if (snameLen < MAX_SNAME_LEN) {
        std::fill((sname_ + snameLen), (sname_ + MAX_SNAME_LEN), 0);
    }

    // No need to store snameLen as any empty space is filled with 0s
}

void
Pkt4::setFile(const uint8_t* file, size_t fileLen /*= MAX_FILE_LEN*/) {
    if (fileLen > MAX_FILE_LEN) {
        isc_throw(OutOfRange, "file field (len=" << fileLen
                  << ") too long, Max " << MAX_FILE_LEN << " supported.");

    } else if (file == NULL) {
        isc_throw(InvalidParameter, "Invalid file name specified");
    }

    std::copy(file, (file + fileLen), file_);
    if (fileLen < MAX_FILE_LEN) {
        std::fill((file_ + fileLen), (file_ + MAX_FILE_LEN), 0);
    }

    // No need to store fileLen as any empty space is filled with 0s
}

uint8_t
// cppcheck-suppress unusedFunction
Pkt4::DHCPTypeToBootpType(uint8_t dhcpType) {
    switch (dhcpType) {
    case DHCPDISCOVER:
    case DHCPREQUEST:
    case DHCPDECLINE:
    case DHCPRELEASE:
    case DHCPINFORM:
    case DHCPLEASEQUERY:
    case DHCPBULKLEASEQUERY:
        return (BOOTREQUEST);

    case DHCPACK:
    case DHCPNAK:
    case DHCPOFFER:
    case DHCPLEASEUNASSIGNED:
    case DHCPLEASEUNKNOWN:
    case DHCPLEASEACTIVE:
    case DHCPLEASEQUERYDONE:
        return (BOOTREPLY);

    default:
        isc_throw(OutOfRange, "Invalid message type: "
                  << static_cast<int>(dhcpType) );
    }
}

uint8_t
Pkt4::getHtype() const {
    if (!hwaddr_) {
        return (HTYPE_UNDEFINED);
    }
    return (hwaddr_->htype_);
}

uint8_t
Pkt4::getHlen() const {
    if (!hwaddr_) {
        return (0);
    }
    uint8_t len = hwaddr_->hwaddr_.size();
    return (len <= MAX_CHADDR_LEN ? len : MAX_CHADDR_LEN);
}

void
Pkt4::addOption(const OptionPtr& opt) {
    // Check for uniqueness (DHCPv4 options must be unique)
    if (getNonCopiedOption(opt->getType())) {
        isc_throw(BadValue, "Option " << opt->getType()
                  << " already present in this message.");
    }

    Pkt::addOption(opt);
}

bool
Pkt4::isRelayed() const {
    return (!giaddr_.isV4Zero() && !giaddr_.isV4Bcast());
}

} // end of namespace isc::dhcp

} // end of namespace isc