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/*
* TLS Session State
* (C) 2011-2012 Jack Lloyd
*
* Released under the terms of the Botan license
*/
#include <botan/tls_session.h>
#include <botan/der_enc.h>
#include <botan/ber_dec.h>
#include <botan/asn1_str.h>
#include <botan/pem.h>
#include <botan/lookup.h>
#include <botan/loadstor.h>
#include <memory>
namespace Botan {
namespace TLS {
Session::Session(const MemoryRegion<byte>& session_identifier,
const MemoryRegion<byte>& master_secret,
Protocol_Version version,
u16bit ciphersuite,
byte compression_method,
Connection_Side side,
bool secure_renegotiation_supported,
size_t fragment_size,
const std::vector<X509_Certificate>& certs,
const MemoryRegion<byte>& ticket,
const std::string& sni_hostname,
const std::string& srp_identifier) :
m_start_time(std::chrono::system_clock::now()),
m_identifier(session_identifier),
m_session_ticket(ticket),
m_master_secret(master_secret),
m_version(version),
m_ciphersuite(ciphersuite),
m_compression_method(compression_method),
m_connection_side(side),
m_secure_renegotiation_supported(secure_renegotiation_supported),
m_fragment_size(fragment_size),
m_peer_certs(certs),
m_sni_hostname(sni_hostname),
m_srp_identifier(srp_identifier)
{
}
Session::Session(const std::string& pem)
{
SecureVector<byte> der = PEM_Code::decode_check_label(pem, "SSL SESSION");
*this = Session(&der[0], der.size());
}
Session::Session(const byte ber[], size_t ber_len)
{
byte side_code = 0;
ASN1_String sni_hostname_str;
ASN1_String srp_identifier_str;
byte major_version = 0, minor_version = 0;
MemoryVector<byte> peer_cert_bits;
size_t start_time = 0;
BER_Decoder(ber, ber_len)
.start_cons(SEQUENCE)
.decode_and_check(static_cast<size_t>(TLS_SESSION_PARAM_STRUCT_VERSION),
"Unknown version in session structure")
.decode_integer_type(start_time)
.decode_integer_type(major_version)
.decode_integer_type(minor_version)
.decode(m_identifier, OCTET_STRING)
.decode(m_session_ticket, OCTET_STRING)
.decode_integer_type(m_ciphersuite)
.decode_integer_type(m_compression_method)
.decode_integer_type(side_code)
.decode_integer_type(m_fragment_size)
.decode(m_secure_renegotiation_supported)
.decode(m_master_secret, OCTET_STRING)
.decode(peer_cert_bits, OCTET_STRING)
.decode(sni_hostname_str)
.decode(srp_identifier_str)
.end_cons()
.verify_end();
m_version = Protocol_Version(major_version, minor_version);
m_start_time = std::chrono::system_clock::from_time_t(start_time);
m_sni_hostname = sni_hostname_str.value();
m_srp_identifier = srp_identifier_str.value();
m_connection_side = static_cast<Connection_Side>(side_code);
if(!peer_cert_bits.empty())
{
DataSource_Memory certs(peer_cert_bits);
while(!certs.end_of_data())
m_peer_certs.push_back(X509_Certificate(certs));
}
}
SecureVector<byte> Session::DER_encode() const
{
MemoryVector<byte> peer_cert_bits;
for(size_t i = 0; i != m_peer_certs.size(); ++i)
peer_cert_bits += m_peer_certs[i].BER_encode();
return DER_Encoder()
.start_cons(SEQUENCE)
.encode(static_cast<size_t>(TLS_SESSION_PARAM_STRUCT_VERSION))
.encode(static_cast<size_t>(std::chrono::system_clock::to_time_t(m_start_time)))
.encode(static_cast<size_t>(m_version.major_version()))
.encode(static_cast<size_t>(m_version.minor_version()))
.encode(m_identifier, OCTET_STRING)
.encode(m_session_ticket, OCTET_STRING)
.encode(static_cast<size_t>(m_ciphersuite))
.encode(static_cast<size_t>(m_compression_method))
.encode(static_cast<size_t>(m_connection_side))
.encode(static_cast<size_t>(m_fragment_size))
.encode(m_secure_renegotiation_supported)
.encode(m_master_secret, OCTET_STRING)
.encode(peer_cert_bits, OCTET_STRING)
.encode(ASN1_String(m_sni_hostname, UTF8_STRING))
.encode(ASN1_String(m_srp_identifier, UTF8_STRING))
.end_cons()
.get_contents();
}
std::string Session::PEM_encode() const
{
return PEM_Code::encode(this->DER_encode(), "SSL SESSION");
}
std::chrono::seconds Session::session_age() const
{
return std::chrono::duration_cast<std::chrono::seconds>(
std::chrono::system_clock::now() - m_start_time);
}
namespace {
const u32bit SESSION_CRYPTO_MAGIC = 0x571B0E4E;
const std::string SESSION_CRYPTO_CIPHER = "AES-256/CBC";
const std::string SESSION_CRYPTO_MAC = "HMAC(SHA-256)";
const std::string SESSION_CRYPTO_KDF = "KDF2(SHA-256)";
const size_t MAGIC_LENGTH = 4;
const size_t MAC_KEY_LENGTH = 32;
const size_t CIPHER_KEY_LENGTH = 32;
const size_t CIPHER_IV_LENGTH = 16;
const size_t MAC_OUTPUT_LENGTH = 32;
}
MemoryVector<byte>
Session::encrypt(const SymmetricKey& master_key,
RandomNumberGenerator& rng) const
{
std::unique_ptr<KDF> kdf(get_kdf(SESSION_CRYPTO_KDF));
SymmetricKey cipher_key =
kdf->derive_key(CIPHER_KEY_LENGTH,
master_key.bits_of(),
"tls.session.cipher-key");
SymmetricKey mac_key =
kdf->derive_key(MAC_KEY_LENGTH,
master_key.bits_of(),
"tls.session.mac-key");
InitializationVector cipher_iv(rng, 16);
std::unique_ptr<MessageAuthenticationCode> mac(get_mac(SESSION_CRYPTO_MAC));
mac->set_key(mac_key);
Pipe pipe(get_cipher(SESSION_CRYPTO_CIPHER, cipher_key, cipher_iv, ENCRYPTION));
pipe.process_msg(this->DER_encode());
MemoryVector<byte> ctext = pipe.read_all(0);
MemoryVector<byte> out(MAGIC_LENGTH);
store_be(SESSION_CRYPTO_MAGIC, &out[0]);
out += cipher_iv.bits_of();
out += ctext;
mac->update(out);
out += mac->final();
return out;
}
Session Session::decrypt(const byte buf[], size_t buf_len,
const SymmetricKey& master_key)
{
try
{
const size_t MIN_CTEXT_SIZE = 4 * 16; // due to 48 byte master secret
if(buf_len < (MAGIC_LENGTH +
CIPHER_IV_LENGTH +
MIN_CTEXT_SIZE +
MAC_OUTPUT_LENGTH))
throw Decoding_Error("Encrypted TLS session too short to be valid");
if(load_be<u32bit>(buf, 0) != SESSION_CRYPTO_MAGIC)
throw Decoding_Error("Unknown header value in encrypted session");
std::unique_ptr<KDF> kdf(get_kdf(SESSION_CRYPTO_KDF));
SymmetricKey mac_key =
kdf->derive_key(MAC_KEY_LENGTH,
master_key.bits_of(),
"tls.session.mac-key");
std::unique_ptr<MessageAuthenticationCode> mac(get_mac(SESSION_CRYPTO_MAC));
mac->set_key(mac_key);
mac->update(&buf[0], buf_len - MAC_OUTPUT_LENGTH);
MemoryVector<byte> computed_mac = mac->final();
if(!same_mem(&buf[buf_len - MAC_OUTPUT_LENGTH], &computed_mac[0], computed_mac.size()))
throw Decoding_Error("MAC verification failed for encrypted session");
SymmetricKey cipher_key =
kdf->derive_key(CIPHER_KEY_LENGTH,
master_key.bits_of(),
"tls.session.cipher-key");
InitializationVector cipher_iv(&buf[MAGIC_LENGTH], CIPHER_IV_LENGTH);
const size_t CTEXT_OFFSET = MAGIC_LENGTH + CIPHER_IV_LENGTH;
Pipe pipe(get_cipher(SESSION_CRYPTO_CIPHER, cipher_key, cipher_iv, DECRYPTION));
pipe.process_msg(&buf[CTEXT_OFFSET],
buf_len - (MAC_OUTPUT_LENGTH + CTEXT_OFFSET));
SecureVector<byte> ber = pipe.read_all();
return Session(&ber[0], ber.size());
}
catch(std::exception& e)
{
throw Decoding_Error("Failed to decrypt encrypted session -" +
std::string(e.what()));
}
}
}
}
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