aboutsummaryrefslogtreecommitdiffstats
path: root/src/tls/msg_client_kex.cpp
diff options
context:
space:
mode:
authorlloyd <[email protected]>2012-08-03 14:42:44 +0000
committerlloyd <[email protected]>2012-08-03 14:42:44 +0000
commit3b8478fbf7aced5b1ab5d56757b6ca70f37e7557 (patch)
treed48fc9257d9eac73b12a1335bbd22d86e610830e /src/tls/msg_client_kex.cpp
parentdb2a5f10716f69a58f8c554c8e65d21e198ffbc5 (diff)
Rename all the message source files to msg_
Diffstat (limited to 'src/tls/msg_client_kex.cpp')
-rw-r--r--src/tls/msg_client_kex.cpp410
1 files changed, 410 insertions, 0 deletions
diff --git a/src/tls/msg_client_kex.cpp b/src/tls/msg_client_kex.cpp
new file mode 100644
index 000000000..1bf41cff2
--- /dev/null
+++ b/src/tls/msg_client_kex.cpp
@@ -0,0 +1,410 @@
+/*
+* Client Key Exchange Message
+* (C) 2004-2010 Jack Lloyd
+*
+* Released under the terms of the Botan license
+*/
+
+#include <botan/internal/tls_messages.h>
+#include <botan/internal/tls_reader.h>
+#include <botan/internal/tls_extensions.h>
+#include <botan/internal/tls_handshake_io.h>
+#include <botan/internal/assert.h>
+#include <botan/credentials_manager.h>
+#include <botan/pubkey.h>
+#include <botan/dh.h>
+#include <botan/ecdh.h>
+#include <botan/rsa.h>
+#include <botan/srp6.h>
+#include <botan/rng.h>
+#include <botan/loadstor.h>
+#include <memory>
+
+namespace Botan {
+
+namespace TLS {
+
+namespace {
+
+secure_vector<byte> strip_leading_zeros(const secure_vector<byte>& input)
+ {
+ size_t leading_zeros = 0;
+
+ for(size_t i = 0; i != input.size(); ++i)
+ {
+ if(input[i] != 0)
+ break;
+ ++leading_zeros;
+ }
+
+ secure_vector<byte> output(&input[leading_zeros],
+ &input[input.size()]);
+ return output;
+ }
+
+}
+
+/*
+* Create a new Client Key Exchange message
+*/
+Client_Key_Exchange::Client_Key_Exchange(Handshake_IO& io,
+ Handshake_State* state,
+ const Policy& policy,
+ Credentials_Manager& creds,
+ const std::vector<X509_Certificate>& peer_certs,
+ const std::string& hostname,
+ RandomNumberGenerator& rng)
+ {
+ const std::string kex_algo = state->suite.kex_algo();
+
+ if(kex_algo == "PSK")
+ {
+ std::string identity_hint = "";
+
+ if(state->server_kex)
+ {
+ TLS_Data_Reader reader(state->server_kex->params());
+ identity_hint = reader.get_string(2, 0, 65535);
+ }
+
+ const std::string hostname = state->client_hello->sni_hostname();
+
+ const std::string psk_identity = creds.psk_identity("tls-client",
+ hostname,
+ identity_hint);
+
+ append_tls_length_value(key_material, psk_identity, 2);
+
+ SymmetricKey psk = creds.psk("tls-client", hostname, psk_identity);
+
+ std::vector<byte> zeros(psk.length());
+
+ append_tls_length_value(pre_master, zeros, 2);
+ append_tls_length_value(pre_master, psk.bits_of(), 2);
+ }
+ else if(state->server_kex)
+ {
+ TLS_Data_Reader reader(state->server_kex->params());
+
+ SymmetricKey psk;
+
+ if(kex_algo == "DHE_PSK" || kex_algo == "ECDHE_PSK")
+ {
+ std::string identity_hint = reader.get_string(2, 0, 65535);
+
+ const std::string hostname = state->client_hello->sni_hostname();
+
+ const std::string psk_identity = creds.psk_identity("tls-client",
+ hostname,
+ identity_hint);
+
+ append_tls_length_value(key_material, psk_identity, 2);
+
+ psk = creds.psk("tls-client", hostname, psk_identity);
+ }
+
+ if(kex_algo == "DH" || kex_algo == "DHE_PSK")
+ {
+ BigInt p = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
+ BigInt g = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
+ BigInt Y = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
+
+ if(reader.remaining_bytes())
+ throw Decoding_Error("Bad params size for DH key exchange");
+
+ if(p.bits() < policy.minimum_dh_group_size())
+ throw TLS_Exception(Alert::INSUFFICIENT_SECURITY,
+ "Server sent DH group of " +
+ std::to_string(p.bits()) +
+ " bits, policy requires at least " +
+ std::to_string(policy.minimum_dh_group_size()));
+
+ /*
+ * A basic check for key validity. As we do not know q here we
+ * cannot check that Y is in the right subgroup. However since
+ * our key is ephemeral there does not seem to be any
+ * advantage to bogus keys anyway.
+ */
+ if(Y <= 1 || Y >= p - 1)
+ throw TLS_Exception(Alert::INSUFFICIENT_SECURITY,
+ "Server sent bad DH key for DHE exchange");
+
+ DL_Group group(p, g);
+
+ if(!group.verify_group(rng, true))
+ throw Internal_Error("DH group failed validation, possible attack");
+
+ DH_PublicKey counterparty_key(group, Y);
+
+ DH_PrivateKey priv_key(rng, group);
+
+ PK_Key_Agreement ka(priv_key, "Raw");
+
+ secure_vector<byte> dh_secret = strip_leading_zeros(
+ ka.derive_key(0, counterparty_key.public_value()).bits_of());
+
+ if(kex_algo == "DH")
+ pre_master = dh_secret;
+ else
+ {
+ append_tls_length_value(pre_master, dh_secret, 2);
+ append_tls_length_value(pre_master, psk.bits_of(), 2);
+ }
+
+ append_tls_length_value(key_material, priv_key.public_value(), 2);
+ }
+ else if(kex_algo == "ECDH" || kex_algo == "ECDHE_PSK")
+ {
+ const byte curve_type = reader.get_byte();
+
+ if(curve_type != 3)
+ throw Decoding_Error("Server sent non-named ECC curve");
+
+ const u16bit curve_id = reader.get_u16bit();
+
+ const std::string name = Supported_Elliptic_Curves::curve_id_to_name(curve_id);
+
+ if(name == "")
+ throw Decoding_Error("Server sent unknown named curve " + std::to_string(curve_id));
+
+ EC_Group group(name);
+
+ std::vector<byte> ecdh_key = reader.get_range<byte>(1, 1, 255);
+
+ ECDH_PublicKey counterparty_key(group, OS2ECP(ecdh_key, group.get_curve()));
+
+ ECDH_PrivateKey priv_key(rng, group);
+
+ PK_Key_Agreement ka(priv_key, "Raw");
+
+ secure_vector<byte> ecdh_secret = ka.derive_key(0, counterparty_key.public_value()).bits_of();
+
+ if(kex_algo == "ECDH")
+ pre_master = ecdh_secret;
+ else
+ {
+ append_tls_length_value(pre_master, ecdh_secret, 2);
+ append_tls_length_value(pre_master, psk.bits_of(), 2);
+ }
+
+ append_tls_length_value(key_material, priv_key.public_value(), 1);
+ }
+ else if(kex_algo == "SRP_SHA")
+ {
+ const BigInt N = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
+ const BigInt g = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
+ std::vector<byte> salt = reader.get_range<byte>(1, 1, 255);
+ const BigInt B = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
+
+ const std::string srp_group = srp6_group_identifier(N, g);
+
+ const std::string srp_identifier =
+ creds.srp_identifier("tls-client", hostname);
+
+ const std::string srp_password =
+ creds.srp_password("tls-client", hostname, srp_identifier);
+
+ std::pair<BigInt, SymmetricKey> srp_vals =
+ srp6_client_agree(srp_identifier,
+ srp_password,
+ srp_group,
+ "SHA-1",
+ salt,
+ B,
+ rng);
+
+ append_tls_length_value(key_material, BigInt::encode(srp_vals.first), 2);
+ pre_master = srp_vals.second.bits_of();
+ }
+ else
+ {
+ throw Internal_Error("Client_Key_Exchange: Unknown kex " +
+ kex_algo);
+ }
+
+ reader.assert_done();
+ }
+ else
+ {
+ // No server key exchange msg better mean RSA kex + RSA key in cert
+
+ if(kex_algo != "RSA")
+ throw Unexpected_Message("No server kex but negotiated kex " + kex_algo);
+
+ if(peer_certs.empty())
+ throw Internal_Error("No certificate and no server key exchange");
+
+ std::unique_ptr<Public_Key> pub_key(peer_certs[0].subject_public_key());
+
+ if(const RSA_PublicKey* rsa_pub = dynamic_cast<const RSA_PublicKey*>(pub_key.get()))
+ {
+ const Protocol_Version offered_version = state->client_hello->version();
+
+ pre_master = rng.random_vec(48);
+ pre_master[0] = offered_version.major_version();
+ pre_master[1] = offered_version.minor_version();
+
+ PK_Encryptor_EME encryptor(*rsa_pub, "PKCS1v15");
+
+ std::vector<byte> encrypted_key = encryptor.encrypt(pre_master, rng);
+
+ if(state->version() == Protocol_Version::SSL_V3)
+ key_material = encrypted_key; // no length field
+ else
+ append_tls_length_value(key_material, encrypted_key, 2);
+ }
+ else
+ throw TLS_Exception(Alert::HANDSHAKE_FAILURE,
+ "Expected a RSA key in server cert but got " +
+ pub_key->algo_name());
+ }
+
+ state->hash.update(io.send(*this));
+ }
+
+/*
+* Read a Client Key Exchange message
+*/
+Client_Key_Exchange::Client_Key_Exchange(const std::vector<byte>& contents,
+ const Handshake_State* state,
+ Credentials_Manager& creds,
+ const Policy& policy,
+ RandomNumberGenerator& rng)
+ {
+ const std::string kex_algo = state->suite.kex_algo();
+
+ if(kex_algo == "RSA")
+ {
+ BOTAN_ASSERT(state->server_certs && !state->server_certs->cert_chain().empty(),
+ "RSA key exchange negotiated so server sent a certificate");
+
+ const Private_Key* private_key = state->server_rsa_kex_key;
+
+ if(!private_key)
+ throw Internal_Error("Expected RSA kex but no server kex key set");
+
+ if(!dynamic_cast<const RSA_PrivateKey*>(private_key))
+ throw Internal_Error("Expected RSA key but got " + private_key->algo_name());
+
+ PK_Decryptor_EME decryptor(*private_key, "PKCS1v15");
+
+ Protocol_Version client_version = state->client_hello->version();
+
+ try
+ {
+ if(state->version() == Protocol_Version::SSL_V3)
+ {
+ pre_master = decryptor.decrypt(contents);
+ }
+ else
+ {
+ TLS_Data_Reader reader(contents);
+ pre_master = decryptor.decrypt(reader.get_range<byte>(2, 0, 65535));
+ }
+
+ if(pre_master.size() != 48 ||
+ client_version.major_version() != pre_master[0] ||
+ client_version.minor_version() != pre_master[1])
+ {
+ throw Decoding_Error("Client_Key_Exchange: Secret corrupted");
+ }
+ }
+ catch(...)
+ {
+ // Randomize to hide timing channel
+ pre_master = rng.random_vec(48);
+ pre_master[0] = client_version.major_version();
+ pre_master[1] = client_version.minor_version();
+ }
+ }
+ else
+ {
+ TLS_Data_Reader reader(contents);
+
+ SymmetricKey psk;
+
+ if(kex_algo == "PSK" || kex_algo == "DHE_PSK" || kex_algo == "ECDHE_PSK")
+ {
+ const std::string psk_identity = reader.get_string(2, 0, 65535);
+
+ psk = creds.psk("tls-server",
+ state->client_hello->sni_hostname(),
+ psk_identity);
+
+ if(psk.length() == 0)
+ {
+ if(policy.hide_unknown_users())
+ psk = SymmetricKey(rng, 16);
+ else
+ throw TLS_Exception(Alert::UNKNOWN_PSK_IDENTITY,
+ "No PSK for identifier " + psk_identity);
+ }
+ }
+
+ if(kex_algo == "PSK")
+ {
+ std::vector<byte> zeros(psk.length());
+ append_tls_length_value(pre_master, zeros, 2);
+ append_tls_length_value(pre_master, psk.bits_of(), 2);
+ }
+ else if(kex_algo == "SRP_SHA")
+ {
+ SRP6_Server_Session& srp = state->server_kex->server_srp_params();
+
+ pre_master = srp.step2(BigInt::decode(reader.get_range<byte>(2, 0, 65535))).bits_of();
+ }
+ else if(kex_algo == "DH" || kex_algo == "DHE_PSK" ||
+ kex_algo == "ECDH" || kex_algo == "ECDHE_PSK")
+ {
+ const Private_Key& private_key = state->server_kex->server_kex_key();
+
+ const PK_Key_Agreement_Key* ka_key =
+ dynamic_cast<const PK_Key_Agreement_Key*>(&private_key);
+
+ if(!ka_key)
+ throw Internal_Error("Expected key agreement key type but got " +
+ private_key.algo_name());
+
+ try
+ {
+ PK_Key_Agreement ka(*ka_key, "Raw");
+
+ std::vector<byte> client_pubkey;
+
+ if(ka_key->algo_name() == "DH")
+ client_pubkey = reader.get_range<byte>(2, 0, 65535);
+ else
+ client_pubkey = reader.get_range<byte>(1, 0, 255);
+
+ secure_vector<byte> shared_secret = ka.derive_key(0, client_pubkey).bits_of();
+
+ if(ka_key->algo_name() == "DH")
+ shared_secret = strip_leading_zeros(shared_secret);
+
+ if(kex_algo == "DHE_PSK" || kex_algo == "ECDHE_PSK")
+ {
+ append_tls_length_value(pre_master, shared_secret, 2);
+ append_tls_length_value(pre_master, psk.bits_of(), 2);
+ }
+ else
+ pre_master = shared_secret;
+ }
+ catch(std::exception &e)
+ {
+ /*
+ * Something failed in the DH computation. To avoid possible
+ * timing attacks, randomize the pre-master output and carry
+ * on, allowing the protocol to fail later in the finished
+ * checks.
+ */
+ pre_master = rng.random_vec(ka_key->public_value().size());
+ }
+ }
+ else
+ throw Internal_Error("Client_Key_Exchange: Unknown kex type " + kex_algo);
+ }
+ }
+
+}
+
+}