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SSH: Support ECDH key exchange.

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As per RFC 5656.

Task-number: QTCREATORBUG-14025
Change-Id: I623c9f0808967f140cdfb40e11234c2e523484e6
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>
Reviewed-by: Christian Kandeler <christian.kandeler@theqtcompany.com>
This commit is contained in:
Christian Kandeler
2015-05-26 10:25:56 +02:00
parent 244cdb7804
commit 3b8ea3fc1e
12 changed files with 224 additions and 73 deletions
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138
src/libs/ssh/sshkeyexchange.cpp
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@@ -113,44 +113,64 @@ bool SshKeyExchange::sendDhInitPacket(const SshIncomingPacket &serverKexInit)
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_kexAlgoName = SshCapabilities::findBestMatch(SshCapabilities::KeyExchangeMethods,
kexInitParams.keyAlgorithms.names);
const QList<QByteArray> &commonHostKeyAlgos
= SshCapabilities::commonCapabilities(SshCapabilities::PublicKeyAlgorithms,
kexInitParams.serverHostKeyAlgorithms.names);
const bool ecdh = m_kexAlgoName.startsWith(SshCapabilities::EcdhKexNamePrefix);
foreach (const QByteArray &possibleHostKeyAlgo, commonHostKeyAlgos) {
if (ecdh && possibleHostKeyAlgo == SshCapabilities::PubKeyEcdsa) {
m_serverHostKeyAlgo = possibleHostKeyAlgo;
break;
}
if (!ecdh && (possibleHostKeyAlgo == SshCapabilities::PubKeyDss
|| possibleHostKeyAlgo == SshCapabilities::PubKeyRsa)) {
m_serverHostKeyAlgo = possibleHostKeyAlgo;
break;
}
}
if (m_serverHostKeyAlgo.isEmpty()) {
throw SshServerException(SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
"Invalid combination of key exchange and host key algorithms.",
QCoreApplication::translate("SshConnection",
"No matching host key algorithm available for key exchange algorithm '%1'.")
.arg(QString::fromLatin1(m_kexAlgoName)));
}
determineHashingAlgorithm(kexInitParams, true);
determineHashingAlgorithm(kexInitParams, false);
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))));
if (ecdh) {
m_ecdhKey.reset(new ECDH_PrivateKey(rng, EC_Group(botanKeyExchangeAlgoName(m_kexAlgoName))));
m_sendFacility.sendKeyEcdhInitPacket(convertByteArray(m_ecdhKey->public_value()));
} else {
m_dhKey.reset(new DH_PrivateKey(rng, DL_Group(botanKeyExchangeAlgoName(m_kexAlgoName))));
m_sendFacility.sendKeyDhInitPacket(m_dhKey->get_y());
}
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()) {
if (m_dhKey && (reply.f <= 0 || reply.f >= m_dhKey->group_p())) {
throw SSH_SERVER_EXCEPTION(SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
"Server sent invalid f.");
}
@@ -160,19 +180,28 @@ void SshKeyExchange::sendNewKeysPacket(const SshIncomingPacket &dhReply,
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);
DH_KA_Operation dhOp(*m_dhKey);
SecureVector<byte> encodedF = BigInt::encode(reply.f);
SecureVector<byte> encodedK = dhOp.agree(encodedF, encodedF.size());
SecureVector<byte> encodedK;
if (m_dhKey) {
concatenatedData += AbstractSshPacket::encodeMpInt(m_dhKey->get_y());
concatenatedData += AbstractSshPacket::encodeMpInt(reply.f);
DH_KA_Operation dhOp(*m_dhKey);
SecureVector<byte> encodedF = BigInt::encode(reply.f);
encodedK = dhOp.agree(encodedF, encodedF.size());
} else {
Q_ASSERT(m_ecdhKey);
concatenatedData // Q_C.
+= AbstractSshPacket::encodeString(convertByteArray(m_ecdhKey->public_value()));
concatenatedData += AbstractSshPacket::encodeString(reply.q_s);
ECDH_KA_Operation ecdhOp(*m_ecdhKey);
encodedK = ecdhOp.agree(convertByteArray(reply.q_s), reply.q_s.count());
}
const BigInt k = BigInt::decode(encodedK);
m_k = AbstractSshPacket::encodeMpInt(k); // Roundtrip, as Botan encodes BigInts somewhat differently.
concatenatedData += m_k;
m_hash.reset(get_hash(botanSha1Name()));
const SecureVector<byte> &hashResult
= m_hash->process(convertByteArray(concatenatedData),
concatenatedData.size());
m_hash.reset(get_hash(botanHMacAlgoName(hashAlgoForKexAlgo())));
const SecureVector<byte> &hashResult = m_hash->process(convertByteArray(concatenatedData),
concatenatedData.size());
m_h = convertByteArray(hashResult);
#ifdef CREATOR_SSH_DEBUG
@@ -199,22 +228,69 @@ void SshKeyExchange::sendNewKeysPacket(const SshIncomingPacket &dhReply,
RSA_PublicKey * const rsaKey
= new RSA_PublicKey(reply.parameters.at(1), reply.parameters.at(0));
sigKey.reset(rsaKey);
} else if (m_serverHostKeyAlgo == SshCapabilities::PubKeyEcdsa) {
const PointGFp point = OS2ECP(convertByteArray(reply.q), reply.q.count(),
m_ecdhKey->domain().get_curve());
ECDSA_PublicKey * const ecdsaKey = new ECDSA_PublicKey(m_ecdhKey->domain(), point);
sigKey.reset(ecdsaKey);
} else {
Q_ASSERT(!"Impossible: Neither DSS nor RSA!");
Q_ASSERT(!"Impossible: Neither DSS nor RSA nor ECDSA!");
}
const byte * const botanH = convertByteArray(m_h);
const Botan::byte * const botanSig
= convertByteArray(reply.signatureBlob);
const Botan::byte * const botanSig = convertByteArray(reply.signatureBlob);
PK_Verifier verifier(*sigKey, botanEmsaAlgoName(m_serverHostKeyAlgo));
if (!verifier.verify_message(botanH, m_h.size(), botanSig,
reply.signatureBlob.size())) {
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.");
"Invalid signature in key exchange reply packet.");
}
checkHostKey(reply.k_s);
m_sendFacility.sendNewKeysPacket();
m_dhKey.reset(nullptr);
m_ecdhKey.reset(nullptr);
}
QByteArray SshKeyExchange::hashAlgoForKexAlgo() const
{
if (m_kexAlgoName == SshCapabilities::EcdhNistp256)
return SshCapabilities::HMacSha256;
if (m_kexAlgoName == SshCapabilities::EcdhNistp384)
return SshCapabilities::HMacSha384;
if (m_kexAlgoName == SshCapabilities::EcdhNistp521)
return SshCapabilities::HMacSha512;
return SshCapabilities::HMacSha1;
}
void SshKeyExchange::determineHashingAlgorithm(const SshKeyExchangeInit &kexInit,
bool serverToClient)
{
QByteArray * const algo = serverToClient ? &m_s2cHMacAlgo : &m_c2sHMacAlgo;
const QList<QByteArray> &serverCapabilities = serverToClient
? kexInit.macAlgorithmsServerToClient.names
: kexInit.macAlgorithmsClientToServer.names;
const QList<QByteArray> commonAlgos = SshCapabilities::commonCapabilities(
SshCapabilities::MacAlgorithms, serverCapabilities);
const QByteArray hashAlgo = hashAlgoForKexAlgo();
foreach (const QByteArray &potentialAlgo, commonAlgos) {
if (potentialAlgo == hashAlgo
|| !m_kexAlgoName.startsWith(SshCapabilities::EcdhKexNamePrefix)) {
*algo = potentialAlgo;
break;
}
}
if (algo->isEmpty()) {
throw SshServerException(SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
"Invalid combination of key exchange and hashing algorithms.",
QCoreApplication::translate("SshConnection",
"Server requested invalid combination of key exchange and hashing algorithms. "
"Key exchange algorithm list was: %1.\nHashing algorithm list was %2.")
.arg(QString::fromLocal8Bit(kexInit.keyAlgorithms.names.join(", ")))
.arg(QString::fromLocal8Bit(serverCapabilities.join(", "))));
}
}
void SshKeyExchange::checkHostKey(const QByteArray &hostKey)