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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/time.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(system_time()),
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;
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(m_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_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>(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");
}
namespace {
const u64bit ENCRYPTED_SESSION_MAGIC = 0xACE4480800000000;
}
MemoryVector<byte>
Session::encrypt(const SymmetricKey& master_key,
RandomNumberGenerator& rng)
{
std::auto_ptr<KDF> kdf(get_kdf("KDF2(SHA-256)"));
SymmetricKey aes_key = kdf->derive_key(32, master_key.bits_of(),
"tls.session.cipher-key");
SymmetricKey hmac_key = kdf->derive_key(32, master_key.bits_of(),
"tls.session.mac-key");
InitializationVector aes_iv(rng, 16);
std::auto_ptr<MessageAuthenticationCode> mac(get_mac("HMAC(SHA-256)"));
mac->set_key(hmac_key);
Pipe pipe(get_cipher("AES-256/CBC", aes_key, aes_iv, ENCRYPTION));
pipe.process_msg(this->DER_encode());
MemoryVector<byte> ctext = pipe.read_all(0);
MemoryVector<byte> out(8);
store_be(ENCRYPTED_SESSION_MAGIC, &out[0]);
out += aes_iv.bits_of();
out += ctext;
mac->update(out);
out += mac->final();
return out;
}
Session Session::decrypt(const MemoryRegion<byte>& buf,
const SymmetricKey& master_key)
{
try
{
/*
8 bytes header
16 bytes IV
32 bytes MAC
16 bytes per AES block * 4 blocks (absolute min amount due to
48 bytes master secret)
*/
if(buf.size() < (8 + 16 + 32 + 4*16))
throw Decoding_Error("Encrypted TLS session too short to be valid");
std::auto_ptr<KDF> kdf(get_kdf("KDF2(SHA-256)"));
SymmetricKey hmac_key = kdf->derive_key(32, master_key.bits_of(),
"tls.session.mac-key");
std::auto_ptr<MessageAuthenticationCode> mac(get_mac("HMAC(SHA-256)"));
mac->set_key(hmac_key);
mac->update(&buf[0], buf.size() - 32);
MemoryVector<byte> computed_mac = mac->final();
if(!same_mem(&buf[buf.size() - 32], &computed_mac[0], computed_mac.size()))
throw Decoding_Error("MAC verification failed for encrypted session");
const u64bit header = load_be<u64bit>(buf, 0);
if(header != ENCRYPTED_SESSION_MAGIC)
throw Decoding_Error("Unknown header value in encrypted session");
SymmetricKey aes_key = kdf->derive_key(32, master_key.bits_of(),
"tls.session.cipher-key");
InitializationVector aes_iv(&buf[8], 16);
Pipe pipe(get_cipher("AES-256/CBC", aes_key, aes_iv, DECRYPTION));
pipe.process_msg(&buf[8+16], buf.size() - (32 + 8 + 16));
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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