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/*
* CMS Algorithm Specific Code
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/cms_enc.h>
#include <botan/der_enc.h>
#include <botan/sha160.h>
#include <botan/cbc.h>
#include <botan/filters.h>
#include <botan/libstate.h>
#if defined(BOTAN_HAS_RC2)
#include <botan/rc2.h>
#endif
namespace Botan {
namespace {
/*
* Wrap a key as specified in RFC 3217
*/
SecureVector<byte> do_rfc3217_wrap(RandomNumberGenerator& rng,
const std::string& cipher_name,
const SymmetricKey& kek,
const SecureVector<byte>& input)
{
class Flip_Bytes : public Filter
{
public:
std::string name() const { return "Fip_Bytes"; }
void write(const byte data[], size_t length)
{
buf += std::make_pair(data, length);
}
void end_msg()
{
for(size_t j = 0; j != buf.size(); j++)
send(buf[buf.size()-j-1]);
buf.clear();
}
Flip_Bytes(const SecureVector<byte>& prefix) : buf(prefix) {}
private:
SecureVector<byte> buf;
};
Algorithm_Factory& af = global_state().algorithm_factory();
const BlockCipher* cipher = af.prototype_block_cipher(cipher_name);
if(!cipher || cipher->block_size() != 8)
throw Encoding_Error("do_rfc3217_wrap: Bad cipher: " + cipher_name);
Pipe icv(new Hash_Filter(new SHA_160, 8));
icv.process_msg(input);
InitializationVector iv(rng, 8);
InitializationVector fixed("4ADDA22C79E82105");
Pipe pipe(new CBC_Encryption(cipher->clone(), new Null_Padding, kek, iv),
new Flip_Bytes(iv.bits_of()),
new CBC_Encryption(cipher->clone(), new Null_Padding, kek, iv));
pipe.start_msg();
pipe.write(input);
pipe.write(icv.read_all());
pipe.end_msg();
return pipe.read_all();
}
}
/*
* Wrap a CEK with a KEK
*/
SecureVector<byte> CMS_Encoder::wrap_key(RandomNumberGenerator& rng,
const std::string& cipher,
const SymmetricKey& cek,
const SymmetricKey& kek)
{
#if defined(BOTAN_HAS_DES)
if(cipher == "TripleDES")
{
SymmetricKey cek_parity = cek;
cek_parity.set_odd_parity();
return do_rfc3217_wrap(rng, cipher, kek, cek_parity.bits_of());
}
#endif
#if defined(BOTAN_HAS_RC2) || defined(BOTAN_HAS_CAST)
if(cipher == "RC2" || cipher == "CAST-128")
{
if(kek.length() != 16)
throw Encoding_Error("CMS: 128-bit KEKs must be used with " + cipher);
SecureVector<byte> lcekpad;
lcekpad.push_back(static_cast<byte>(cek.length()));
lcekpad += cek.bits_of();
while(lcekpad.size() % 8)
lcekpad.push_back(rng.next_byte());
return do_rfc3217_wrap(rng, cipher, kek, lcekpad);
}
#endif
throw Invalid_Argument("CMS_Encoder::wrap: Unknown cipher " + cipher);
}
/*
* Encode the parameters for an encryption algo
*/
SecureVector<byte> CMS_Encoder::encode_params(const std::string& cipher,
const SymmetricKey& key,
const InitializationVector& iv)
{
DER_Encoder encoder;
#if defined(BOTAN_HAS_RC2)
if(cipher == "RC2")
{
encoder.start_cons(SEQUENCE).
encode(static_cast<size_t>(RC2::EKB_code(8*key.length()))).
encode(iv.bits_of(), OCTET_STRING).
end_cons();
return encoder.get_contents();
}
#endif
if(cipher == "CAST-128")
{
encoder.start_cons(SEQUENCE).
encode(iv.bits_of(), OCTET_STRING).
encode(8*key.length()).
end_cons();
}
else
encoder.encode(iv.bits_of(), OCTET_STRING);
return encoder.get_contents();
}
/*
* Generate a CEK or KEK for the cipher
*/
SymmetricKey CMS_Encoder::setup_key(RandomNumberGenerator& rng,
const std::string& cipher)
{
size_t keysize = 0;
if(cipher == "TripleDES") keysize = 24;
if(cipher == "RC2") keysize = 16;
if(cipher == "CAST-128") keysize = 16;
if(keysize == 0)
throw Invalid_Argument("CMS: Cannot encrypt with cipher " + cipher);
SymmetricKey key(rng, keysize);
if(cipher == "DES" || cipher == "TripleDES")
key.set_odd_parity();
return key;
}
}
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