qt-creator/src/libs/ssh/sshkeyexchange.cpp

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** This file is part of Qt Creator.
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#include "sshkeyexchange_p.h"

#include "sshbotanconversions_p.h"
#include "sshcapabilities_p.h"
#include "sshsendfacility_p.h"
#include "sshexception_p.h"
#include "sshincomingpacket_p.h"

#include <botan/botan.h>

#ifdef CREATOR_SSH_DEBUG
#include <iostream>
#endif
#include <string>

using namespace Botan;

namespace QSsh {
namespace Internal {

namespace {

    // For debugging
    void printNameList(const char *listName, const SshNameList &list)
    {
#ifdef CREATOR_SSH_DEBUG
        qDebug("%s:", listName);
        foreach (const QByteArray &name, list.names)
            qDebug("%s", name.constData());
#else
        Q_UNUSED(listName);
        Q_UNUSED(list);
#endif
    }

#ifdef CREATOR_SSH_DEBUG
    void printData(const char *name, const QByteArray &data)
    {
        std::cerr << std::hex;
        qDebug("The client thinks the %s has length %d and is:", name, data.count());
        for (int i = 0; i < data.count(); ++i)
            std::cerr << (static_cast<unsigned int>(data.at(i)) & 0xff) << ' ';
        std::cerr << std::endl;
    }
#endif

} // anonymous namespace

SshKeyExchange::SshKeyExchange(SshSendFacility &sendFacility)
    : m_sendFacility(sendFacility)
{
}

SshKeyExchange::~SshKeyExchange() {}

void SshKeyExchange::sendKexInitPacket(const QByteArray &serverId)
{
    m_serverId = serverId;
    m_clientKexInitPayload = m_sendFacility.sendKeyExchangeInitPacket();
}

bool SshKeyExchange::sendDhInitPacket(const SshIncomingPacket &serverKexInit)
{
#ifdef CREATOR_SSH_DEBUG
    qDebug("server requests key exchange");
#endif
    serverKexInit.printRawBytes();
    SshKeyExchangeInit kexInitParams
            = serverKexInit.extractKeyExchangeInitData();

    printNameList("Key Algorithms", kexInitParams.keyAlgorithms);
    printNameList("Server Host Key Algorithms", kexInitParams.serverHostKeyAlgorithms);
    printNameList("Encryption algorithms client to server", kexInitParams.encryptionAlgorithmsClientToServer);
    printNameList("Encryption algorithms server to client", kexInitParams.encryptionAlgorithmsServerToClient);
    printNameList("MAC algorithms client to server", kexInitParams.macAlgorithmsClientToServer);
    printNameList("MAC algorithms server to client", kexInitParams.macAlgorithmsServerToClient);
    printNameList("Compression algorithms client to server", kexInitParams.compressionAlgorithmsClientToServer);
    printNameList("Compression algorithms client to server", kexInitParams.compressionAlgorithmsClientToServer);
    printNameList("Languages client to server", kexInitParams.languagesClientToServer);
    printNameList("Languages server to client", kexInitParams.languagesServerToClient);
#ifdef CREATOR_SSH_DEBUG
    qDebug("First packet follows: %d", kexInitParams.firstKexPacketFollows);
#endif

    const QByteArray &keyAlgo
        = SshCapabilities::findBestMatch(SshCapabilities::KeyExchangeMethods,
              kexInitParams.keyAlgorithms.names);
    m_serverHostKeyAlgo
        = SshCapabilities::findBestMatch(SshCapabilities::PublicKeyAlgorithms,
              kexInitParams.serverHostKeyAlgorithms.names);
    m_encryptionAlgo
        = SshCapabilities::findBestMatch(SshCapabilities::EncryptionAlgorithms,
              kexInitParams.encryptionAlgorithmsClientToServer.names);
    m_decryptionAlgo
        = SshCapabilities::findBestMatch(SshCapabilities::EncryptionAlgorithms,
              kexInitParams.encryptionAlgorithmsServerToClient.names);
    m_c2sHMacAlgo
        = SshCapabilities::findBestMatch(SshCapabilities::MacAlgorithms,
              kexInitParams.macAlgorithmsClientToServer.names);
    m_s2cHMacAlgo
        = SshCapabilities::findBestMatch(SshCapabilities::MacAlgorithms,
              kexInitParams.macAlgorithmsServerToClient.names);
    SshCapabilities::findBestMatch(SshCapabilities::CompressionAlgorithms,
        kexInitParams.compressionAlgorithmsClientToServer.names);
    SshCapabilities::findBestMatch(SshCapabilities::CompressionAlgorithms,
        kexInitParams.compressionAlgorithmsServerToClient.names);

    AutoSeeded_RNG rng;
    m_dhKey.reset(new DH_PrivateKey(rng,
        DL_Group(botanKeyExchangeAlgoName(keyAlgo))));

    m_serverKexInitPayload = serverKexInit.payLoad();
    m_sendFacility.sendKeyDhInitPacket(m_dhKey->get_y());
    return kexInitParams.firstKexPacketFollows;
}

void SshKeyExchange::sendNewKeysPacket(const SshIncomingPacket &dhReply,
    const QByteArray &clientId)
{
    const SshKeyExchangeReply &reply
        = dhReply.extractKeyExchangeReply(m_serverHostKeyAlgo);
    if (reply.f <= 0 || reply.f >= m_dhKey->group_p()) {
        throw SSH_SERVER_EXCEPTION(SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
            "Server sent invalid f.");
    }

    QByteArray concatenatedData = AbstractSshPacket::encodeString(clientId);
    concatenatedData += AbstractSshPacket::encodeString(m_serverId);
    concatenatedData += AbstractSshPacket::encodeString(m_clientKexInitPayload);
    concatenatedData += AbstractSshPacket::encodeString(m_serverKexInitPayload);
    concatenatedData += reply.k_s;
    concatenatedData += AbstractSshPacket::encodeMpInt(m_dhKey->get_y());
    concatenatedData += AbstractSshPacket::encodeMpInt(reply.f);
    const BigInt k = power_mod(reply.f, m_dhKey->get_x(), m_dhKey->get_domain().get_p());
    m_k = AbstractSshPacket::encodeMpInt(k);
    concatenatedData += m_k;

    m_hash.reset(get_hash(botanSha1Name()));
    const SecureVector<byte> &hashResult
        = m_hash->process(convertByteArray(concatenatedData),
                        concatenatedData.size());
    m_h = convertByteArray(hashResult);

#ifdef CREATOR_SSH_DEBUG
    printData("Client Id", AbstractSshPacket::encodeString(clientId));
    printData("Server Id", AbstractSshPacket::encodeString(m_serverId));
    printData("Client Payload", AbstractSshPacket::encodeString(m_clientKexInitPayload));
    printData("Server payload", AbstractSshPacket::encodeString(m_serverKexInitPayload));
    printData("K_S", reply.k_s);
    printData("y", AbstractSshPacket::encodeMpInt(m_dhKey->get_y()));
    printData("f", AbstractSshPacket::encodeMpInt(reply.f));
    printData("K", m_k);
    printData("Concatenated data", concatenatedData);
    printData("H", m_h);
#endif // CREATOR_SSH_DEBUG

    QScopedPointer<Public_Key> sigKey;
    QScopedPointer<PK_Verifier> verifier;
    if (m_serverHostKeyAlgo == SshCapabilities::PubKeyDss) {
        const DL_Group group(reply.parameters.at(0), reply.parameters.at(1),
            reply.parameters.at(2));
        DSA_PublicKey * const dsaKey
            = new DSA_PublicKey(group, reply.parameters.at(3));
        sigKey.reset(dsaKey);
        verifier.reset(new PK_Verifier(*dsaKey, botanEmsaAlgoName(SshCapabilities::PubKeyDss)));
    } else if (m_serverHostKeyAlgo == SshCapabilities::PubKeyRsa) {
        RSA_PublicKey * const rsaKey
            = new RSA_PublicKey(reply.parameters.at(1), reply.parameters.at(0));
        sigKey.reset(rsaKey);
        verifier.reset(new PK_Verifier(*rsaKey, botanEmsaAlgoName(SshCapabilities::PubKeyRsa)));
    } else {
        Q_ASSERT(!"Impossible: Neither DSS nor RSA!");
    }
    const byte * const botanH = convertByteArray(m_h);
    const Botan::byte * const botanSig
        = convertByteArray(reply.signatureBlob);
    if (!verifier->verify_message(botanH, m_h.size(), botanSig,
        reply.signatureBlob.size())) {
        throw SSH_SERVER_EXCEPTION(SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
            "Invalid signature in SSH_MSG_KEXDH_REPLY packet.");
    }

    m_sendFacility.sendNewKeysPacket();
}

} // namespace Internal
} // namespace QSsh