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/*
* Copyright (C) 2014 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#include "mongo/platform/basic.h"
#include "mongo/db/auth/mechanism_scram.h"
#include <vector>
#ifdef MONGO_SSL
#include <openssl/sha.h>
#include <openssl/evp.h>
#include <openssl/hmac.h>
#endif
#include "mongo/platform/random.h"
#include "mongo/util/base64.h"
namespace mongo {
const int scramHashSize = 20;
// Need to #ifdef this until our SCRAM implementation
// is independent of libcrypto
#ifdef MONGO_SSL
// Compute the SCRAM step Hi() as defined in RFC5802
static void HMACIteration(const unsigned char input[],
size_t inputLen,
const unsigned char salt[],
size_t saltLen,
unsigned int iterationCount,
unsigned char output[]){
unsigned char tmpRes[scramHashSize];
unsigned char startKey[scramHashSize];
unsigned int hashLen = 0;
uassert(17450, "invalid salt length provided", saltLen <= 16);
memcpy (startKey, salt, saltLen);
startKey[saltLen] = 0;
startKey[saltLen+1] = 0;
startKey[saltLen+2] = 0;
startKey[saltLen+3] = 1;
// U1 = HMAC(input, salt || 1)
fassert(17494, HMAC(EVP_sha1(),
input,
inputLen,
startKey,
saltLen + 4,
output,
&hashLen));
memcpy(tmpRes, output, scramHashSize);
// tmpRes contain Uj and result contains the accumulated XOR:ed result
for (size_t i = 2; i <= iterationCount; i++) {
fassert(17495, HMAC(EVP_sha1(),
input,
inputLen,
tmpRes,
scramHashSize,
tmpRes,
&hashLen));
for (int k = 0; k < scramHashSize; k++) {
output[k] ^= tmpRes[k];
}
}
}
/* Compute the SCRAM secrets storedKey and serverKey
* as defined in RFC5802 */
static void computeSCRAMProperties(const std::string& password,
const unsigned char salt[],
size_t saltLen,
size_t iterationCount,
unsigned char storedKey[scramHashSize],
unsigned char serverKey[scramHashSize]) {
unsigned char saltedPassword[scramHashSize];
unsigned char clientKey[scramHashSize];
unsigned int hashLen = 0;
// saltedPassword = Hi(password, salt)
HMACIteration(reinterpret_cast<const unsigned char*>(password.data()),
password.size(),
salt,
saltLen,
iterationCount,
saltedPassword);
// clientKey = HMAC(saltedPassword, "Client Key")
const std::string clientKeyConst = "Client Key";
fassert(17498, HMAC(EVP_sha1(),
saltedPassword,
scramHashSize,
reinterpret_cast<const unsigned char*>(clientKeyConst.data()),
clientKeyConst.size(),
clientKey,
&hashLen));
// storedKey = H(clientKey)
fassert(17499, SHA1(clientKey, scramHashSize, storedKey));
// serverKey = HMAC(saltedPassword, "Server Key")
const std::string serverKeyConst = "Server Key";
fassert(17500, HMAC(EVP_sha1(),
saltedPassword,
scramHashSize,
reinterpret_cast<const unsigned char*>(serverKeyConst.data()),
serverKeyConst.size(),
serverKey,
&hashLen));
}
#endif //MONGO_SSL
BSONObj generateSCRAMCredentials(const std::string& hashedPassword) {
#ifndef MONGO_SSL
return BSONObj();
#else
// TODO: configure the default iteration count via setParameter
const int iterationCount = 10000;
const int saltLenQWords = 2;
// Generate salt
uint64_t userSalt[saltLenQWords];
scoped_ptr<SecureRandom> sr(SecureRandom::create());
userSalt[0] = sr->nextInt64();
userSalt[1] = sr->nextInt64();
std::string encodedUserSalt =
base64::encode(reinterpret_cast<char*>(&userSalt[0]), sizeof(userSalt));
// Compute SCRAM secrets serverKey and storedKey
unsigned char storedKey[scramHashSize];
unsigned char serverKey[scramHashSize];
computeSCRAMProperties(hashedPassword,
reinterpret_cast<unsigned char*>(userSalt),
saltLenQWords*sizeof(uint64_t),
iterationCount,
storedKey,
serverKey);
std::string encodedStoredKey =
base64::encode(reinterpret_cast<char*>(&storedKey[0]), scramHashSize);
std::string encodedServerKey =
base64::encode(reinterpret_cast<char*>(&serverKey[0]), scramHashSize);
return BSON("iterationCount" << iterationCount <<
"salt" << encodedUserSalt <<
"storedKey" << encodedStoredKey <<
"serverKey" << encodedServerKey);
#endif
}
} // namespace mongo
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