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/*
* PKCS #5 PBES2
* (C) 1999-2008,2014 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/pbes2.h>
#include <botan/cipher_mode.h>
#include <botan/pbkdf.h>
#include <botan/der_enc.h>
#include <botan/ber_dec.h>
#include <botan/parsing.h>
#include <botan/alg_id.h>
#include <botan/oids.h>
#include <botan/rng.h>
#include <algorithm>
namespace Botan {
namespace {
/*
* Encode PKCS#5 PBES2 parameters
*/
std::vector<byte> encode_pbes2_params(const std::string& cipher,
const std::string& prf,
const secure_vector<byte>& salt,
const secure_vector<byte>& iv,
size_t iterations,
size_t key_length)
{
return DER_Encoder()
.start_cons(SEQUENCE)
.encode(
AlgorithmIdentifier("PKCS5.PBKDF2",
DER_Encoder()
.start_cons(SEQUENCE)
.encode(salt, OCTET_STRING)
.encode(iterations)
.encode(key_length)
.encode_if(
prf != "HMAC(SHA-160)",
AlgorithmIdentifier(prf, AlgorithmIdentifier::USE_NULL_PARAM))
.end_cons()
.get_contents_unlocked()
)
)
.encode(
AlgorithmIdentifier(cipher,
DER_Encoder().encode(iv, OCTET_STRING).get_contents_unlocked()
)
)
.end_cons()
.get_contents_unlocked();
}
}
/*
* PKCS#5 v2.0 PBE Constructor
*/
std::pair<AlgorithmIdentifier, std::vector<byte>>
pbes2_encrypt(const secure_vector<byte>& key_bits,
const std::string& passphrase,
std::chrono::milliseconds msec,
const std::string& cipher,
const std::string& digest,
RandomNumberGenerator& rng)
{
const std::string prf = "HMAC(" + digest + ")";
const std::vector<std::string> cipher_spec = split_on(cipher, '/');
if(cipher_spec.size() != 2)
throw Decoding_Error("PBE-PKCS5 v2.0: Invalid cipher spec " + cipher);
const secure_vector<byte> salt = rng.random_vec(12);
if(cipher_spec[1] != "CBC" && cipher_spec[1] != "GCM")
throw Decoding_Error("PBE-PKCS5 v2.0: Don't know param format for " + cipher);
std::unique_ptr<Cipher_Mode> enc(get_cipher_mode(cipher, ENCRYPTION));
if(!enc)
throw Decoding_Error("PBE-PKCS5 cannot encrypt no cipher " + cipher);
std::unique_ptr<PBKDF> pbkdf(get_pbkdf("PBKDF2(" + prf + ")"));
const size_t key_length = enc->key_spec().maximum_keylength();
size_t iterations = 0;
secure_vector<byte> iv = rng.random_vec(enc->default_nonce_length());
enc->set_key(pbkdf->derive_key(key_length, passphrase, salt.data(), salt.size(),
msec, iterations).bits_of());
enc->start(iv);
secure_vector<byte> buf = key_bits;
enc->finish(buf);
AlgorithmIdentifier id(
OIDS::lookup("PBE-PKCS5v20"),
encode_pbes2_params(cipher, prf, salt, iv, iterations, key_length));
return std::make_pair(id, unlock(buf));
}
secure_vector<byte>
pbes2_decrypt(const secure_vector<byte>& key_bits,
const std::string& passphrase,
const std::vector<byte>& params)
{
AlgorithmIdentifier kdf_algo, enc_algo;
BER_Decoder(params)
.start_cons(SEQUENCE)
.decode(kdf_algo)
.decode(enc_algo)
.verify_end()
.end_cons();
AlgorithmIdentifier prf_algo;
if(kdf_algo.oid != OIDS::lookup("PKCS5.PBKDF2"))
throw Decoding_Error("PBE-PKCS5 v2.0: Unknown KDF algorithm " +
kdf_algo.oid.as_string());
secure_vector<byte> salt;
size_t iterations = 0, key_length = 0;
BER_Decoder(kdf_algo.parameters)
.start_cons(SEQUENCE)
.decode(salt, OCTET_STRING)
.decode(iterations)
.decode_optional(key_length, INTEGER, UNIVERSAL)
.decode_optional(prf_algo, SEQUENCE, CONSTRUCTED,
AlgorithmIdentifier("HMAC(SHA-160)",
AlgorithmIdentifier::USE_NULL_PARAM))
.verify_end()
.end_cons();
const std::string cipher = OIDS::lookup(enc_algo.oid);
const std::vector<std::string> cipher_spec = split_on(cipher, '/');
if(cipher_spec.size() != 2)
throw Decoding_Error("PBE-PKCS5 v2.0: Invalid cipher spec " + cipher);
if(cipher_spec[1] != "CBC" && cipher_spec[1] != "GCM")
throw Decoding_Error("PBE-PKCS5 v2.0: Don't know param format for " + cipher);
if(salt.size() < 8)
throw Decoding_Error("PBE-PKCS5 v2.0: Encoded salt is too small");
secure_vector<byte> iv;
BER_Decoder(enc_algo.parameters).decode(iv, OCTET_STRING).verify_end();
const std::string prf = OIDS::lookup(prf_algo.oid);
std::unique_ptr<PBKDF> pbkdf(get_pbkdf("PBKDF2(" + prf + ")"));
std::unique_ptr<Cipher_Mode> dec(get_cipher_mode(cipher, DECRYPTION));
if(!dec)
throw Decoding_Error("PBE-PKCS5 cannot decrypt no cipher " + cipher);
if(key_length == 0)
key_length = dec->key_spec().maximum_keylength();
dec->set_key(pbkdf->pbkdf_iterations(key_length, passphrase, salt.data(), salt.size(), iterations));
dec->start(iv);
secure_vector<byte> buf = key_bits;
dec->finish(buf);
return buf;
}
}
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