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/*
* (C) 2017 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/psk_db.h>
#include <botan/exceptn.h>
#include <botan/nist_keywrap.h>
#include <botan/base64.h>
#include <botan/mac.h>
#include <botan/block_cipher.h>
namespace Botan {
Encrypted_PSK_Database::Encrypted_PSK_Database(const secure_vector<uint8_t>& master_key)
{
m_cipher = BlockCipher::create_or_throw("AES-256");
m_hmac = MessageAuthenticationCode::create_or_throw("HMAC(SHA-256)");
m_hmac->set_key(master_key);
m_cipher->set_key(m_hmac->process("wrap"));
m_hmac->set_key(m_hmac->process("hmac"));
}
Encrypted_PSK_Database::~Encrypted_PSK_Database()
{
// for ~unique_ptr
}
std::set<std::string> Encrypted_PSK_Database::list_names() const
{
const std::set<std::string> encrypted_names = kv_get_all();
std::set<std::string> names;
for(std::string enc_name : encrypted_names)
{
try
{
const secure_vector<uint8_t> raw_name = base64_decode(enc_name);
const secure_vector<uint8_t> name_bits =
nist_key_unwrap_padded(raw_name.data(), raw_name.size(), *m_cipher);
std::string pt_name(cast_uint8_ptr_to_char(name_bits.data()), name_bits.size());
names.insert(pt_name);
}
catch(Invalid_Authentication_Tag&)
{
}
}
return names;
}
void Encrypted_PSK_Database::remove(const std::string& name)
{
const std::vector<uint8_t> wrapped_name =
nist_key_wrap_padded(cast_char_ptr_to_uint8(name.data()),
name.size(),
*m_cipher);
this->kv_del(base64_encode(wrapped_name));
}
secure_vector<uint8_t> Encrypted_PSK_Database::get(const std::string& name) const
{
const std::vector<uint8_t> wrapped_name =
nist_key_wrap_padded(cast_char_ptr_to_uint8(name.data()),
name.size(),
*m_cipher);
const std::string val_base64 = kv_get(base64_encode(wrapped_name));
if(val_base64.empty())
throw Invalid_Argument("Named PSK not located");
const secure_vector<uint8_t> val = base64_decode(val_base64);
std::unique_ptr<BlockCipher> wrap_cipher(m_cipher->clone());
wrap_cipher->set_key(m_hmac->process(wrapped_name));
return nist_key_unwrap_padded(val.data(), val.size(), *wrap_cipher);
}
void Encrypted_PSK_Database::set(const std::string& name, const uint8_t val[], size_t len)
{
/*
* Both as a basic precaution wrt key seperation, and specifically to prevent
* cut-and-paste attacks against the database, each PSK is encrypted with a
* distinct key which is derived by hashing the wrapped key name with HMAC.
*/
const std::vector<uint8_t> wrapped_name =
nist_key_wrap_padded(cast_char_ptr_to_uint8(name.data()),
name.size(),
*m_cipher);
std::unique_ptr<BlockCipher> wrap_cipher(m_cipher->clone());
wrap_cipher->set_key(m_hmac->process(wrapped_name));
const std::vector<uint8_t> wrapped_key = nist_key_wrap_padded(val, len, *wrap_cipher);
this->kv_set(base64_encode(wrapped_name), base64_encode(wrapped_key));
}
}