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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/crypto/mechanism_scram.h"
#include <boost/scoped_ptr.hpp>
#include <vector>
#include "mongo/crypto/crypto.h"
#include "mongo/platform/random.h"
#include "mongo/util/base64.h"
namespace mongo {
namespace scram {
using boost::scoped_ptr;
// 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 intermediateDigest[hashSize];
unsigned char startKey[hashSize];
// Placeholder for HMAC return size, will always be scram::hashSize for HMAC SHA-1
unsigned int hashLen = 0;
uassert(17450, "invalid salt length provided", saltLen + 4 == hashSize);
memcpy (startKey, salt, saltLen);
startKey[saltLen] = 0;
startKey[saltLen+1] = 0;
startKey[saltLen+2] = 0;
startKey[saltLen+3] = 1;
// U1 = HMAC(input, salt + 0001)
fassert(17494, crypto::hmacSha1(input,
inputLen,
startKey,
saltLen + 4,
output,
&hashLen));
memcpy(intermediateDigest, output, hashSize);
// intermediateDigest contains Ui and output contains the accumulated XOR:ed result
for (size_t i = 2; i <= iterationCount; i++) {
unsigned char intermediateOutput[hashSize];
fassert(17495, crypto::hmacSha1(input,
inputLen,
intermediateDigest,
hashSize,
intermediateOutput,
&hashLen));
memcpy(intermediateDigest, intermediateOutput, hashSize);
for (size_t k = 0; k < hashSize; k++) {
output[k] ^= intermediateDigest[k];
}
}
}
// Iterate the hash function to generate SaltedPassword
void generateSaltedPassword(const StringData& hashedPassword,
const unsigned char* salt,
const int saltLen,
const int iterationCount,
unsigned char saltedPassword[hashSize]) {
// saltedPassword = Hi(hashedPassword, salt)
HMACIteration(reinterpret_cast<const unsigned char*>(hashedPassword.rawData()),
hashedPassword.size(),
salt,
saltLen,
iterationCount,
saltedPassword);
}
void generateSecrets(const std::string& hashedPassword,
const unsigned char salt[],
size_t saltLen,
size_t iterationCount,
unsigned char storedKey[hashSize],
unsigned char serverKey[hashSize]) {
unsigned char saltedPassword[hashSize];
unsigned char clientKey[hashSize];
unsigned int hashLen = 0;
generateSaltedPassword(hashedPassword,
salt,
saltLen,
iterationCount,
saltedPassword);
// clientKey = HMAC(saltedPassword, "Client Key")
fassert(17498,
crypto::hmacSha1(saltedPassword,
hashSize,
reinterpret_cast<const unsigned char*>(clientKeyConst.data()),
clientKeyConst.size(),
clientKey,
&hashLen));
// storedKey = H(clientKey)
fassert(17499, crypto::sha1(clientKey, hashSize, storedKey));
// serverKey = HMAC(saltedPassword, "Server Key")
fassert(17500,
crypto::hmacSha1(saltedPassword,
hashSize,
reinterpret_cast<const unsigned char*>(serverKeyConst.data()),
serverKeyConst.size(),
serverKey,
&hashLen));
}
BSONObj generateCredentials(const std::string& hashedPassword, int iterationCount) {
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), sizeof(userSalt));
// Compute SCRAM secrets serverKey and storedKey
unsigned char storedKey[hashSize];
unsigned char serverKey[hashSize];
generateSecrets(hashedPassword,
reinterpret_cast<unsigned char*>(userSalt),
saltLenQWords*sizeof(uint64_t),
iterationCount,
storedKey,
serverKey);
std::string encodedStoredKey =
base64::encode(reinterpret_cast<char*>(storedKey), hashSize);
std::string encodedServerKey =
base64::encode(reinterpret_cast<char*>(serverKey), hashSize);
return BSON(iterationCountFieldName << iterationCount <<
saltFieldName << encodedUserSalt <<
storedKeyFieldName << encodedStoredKey <<
serverKeyFieldName << encodedServerKey);
}
std::string generateClientProof(const unsigned char saltedPassword[hashSize],
const std::string& authMessage) {
// ClientKey := HMAC(saltedPassword, "Client Key")
unsigned char clientKey[hashSize];
unsigned int hashLen = 0;
fassert(18689,
crypto::hmacSha1(saltedPassword,
hashSize,
reinterpret_cast<const unsigned char*>(clientKeyConst.data()),
clientKeyConst.size(),
clientKey,
&hashLen));
// StoredKey := H(clientKey)
unsigned char storedKey[hashSize];
fassert(18701, crypto::sha1(clientKey, hashSize, storedKey));
// ClientSignature := HMAC(StoredKey, AuthMessage)
unsigned char clientSignature[hashSize];
fassert(18702,
crypto::hmacSha1(storedKey,
hashSize,
reinterpret_cast<const unsigned char*>(authMessage.c_str()),
authMessage.size(),
clientSignature,
&hashLen));
// ClientProof := ClientKey XOR ClientSignature
unsigned char clientProof[hashSize];
for (size_t i = 0; i<hashSize; i++) {
clientProof[i] = clientKey[i] ^ clientSignature[i];
}
return base64::encode(reinterpret_cast<char*>(clientProof), hashSize);
}
bool verifyServerSignature(const unsigned char saltedPassword[hashSize],
const std::string& authMessage,
const std::string& receivedServerSignature) {
// ServerKey := HMAC(SaltedPassword, "Server Key")
unsigned int hashLen;
unsigned char serverKey[hashSize];
fassert(18703,
crypto::hmacSha1(saltedPassword,
hashSize,
reinterpret_cast<const unsigned char*>(serverKeyConst.data()),
serverKeyConst.size(),
serverKey,
&hashLen));
// ServerSignature := HMAC(ServerKey, AuthMessage)
unsigned char serverSignature[hashSize];
fassert(18704,
crypto::hmacSha1(serverKey,
hashSize,
reinterpret_cast<const unsigned char*>(authMessage.c_str()),
authMessage.size(),
serverSignature,
&hashLen));
std::string encodedServerSignature =
base64::encode(reinterpret_cast<char*>(serverSignature), sizeof(serverSignature));
return (receivedServerSignature == encodedServerSignature);
}
} // namespace scram
} // namespace mongo
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