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/*
* Copyright (C) 2014 MongoDB 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.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kAccessControl
#include "mongo/platform/basic.h"
#include "mongo/db/auth/sasl_scramsha1_server_conversation.h"
#include <boost/algorithm/string/join.hpp>
#include <boost/algorithm/string/replace.hpp>
#include "mongo/crypto/crypto.h"
#include "mongo/crypto/mechanism_scram.h"
#include "mongo/platform/random.h"
#include "mongo/util/base64.h"
#include "mongo/util/log.h"
#include "mongo/util/mongoutils/str.h"
#include "mongo/util/password_digest.h"
#include "mongo/util/text.h"
namespace mongo {
SaslSCRAMSHA1ServerConversation::SaslSCRAMSHA1ServerConversation(
SaslAuthenticationSession* saslAuthSession) :
SaslServerConversation(saslAuthSession),
_step(0),
_authMessage(""),
_nonce("") {
}
StatusWith<bool> SaslSCRAMSHA1ServerConversation::step(const StringData& inputData,
std::string* outputData) {
std::vector<std::string> input = StringSplitter::split(inputData.toString(), ",");
_step++;
if (_step > 3 || _step <= 0) {
return StatusWith<bool>(ErrorCodes::AuthenticationFailed,
mongoutils::str::stream() << "Invalid SCRAM-SHA-1 authentication step: " << _step);
}
if (_step == 1) {
return _firstStep(input, outputData);
}
if (_step == 2) {
return _secondStep(input, outputData);
}
*outputData = "";
return StatusWith<bool>(true);
}
/*
* RFC 5802 specifies that in SCRAM user names characters ',' and '=' are encoded as
* =2C and =3D respectively.
*/
static void decodeSCRAMUsername(std::string& user) {
boost::replace_all(user, "=2C", ",");
boost::replace_all(user, "=3D", "=");
}
/*
* Parse client-first-message of the form:
* n,a=authzid,n=encoded-username,r=client-nonce
*
* Generate server-first-message on the form:
* r=client-nonce|server-nonce,s=user-salt,i=iteration-count
*
* NOTE: we are ignoring the authorization ID part of the message
*/
StatusWith<bool> SaslSCRAMSHA1ServerConversation::_firstStep(std::vector<string>& input,
std::string* outputData) {
std::string authzId = "";
if (input.size() == 4) {
/* The second entry a=authzid is optional. If provided it will be
* validated against the encoded username.
*
* The two allowed input forms are:
* n,,n=encoded-username,r=client-nonce
* n,a=authzid,n=encoded-username,r=client-nonce
*/
if (!str::startsWith(input[1], "a=") || input[1].size() < 3) {
return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() <<
"Incorrect SCRAM-SHA-1 authzid: " << input[1]);
}
authzId = input[1].substr(2);
input.erase(input.begin() + 1);
}
if (input.size() != 3) {
return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() <<
"Incorrect number of arguments for first SCRAM-SHA-1 client message, got " <<
input.size() << " expected 4");
}
else if (input[0] != "n") {
return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() <<
"Incorrect SCRAM-SHA-1 client message prefix: " << input[0]);
}
else if (!str::startsWith(input[1], "n=") || input[1].size() < 3) {
return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() <<
"Incorrect SCRAM-SHA-1 user name: " << input[1]);
}
else if(!str::startsWith(input[2], "r=") || input[2].size() < 6) {
return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() <<
"Incorrect SCRAM-SHA-1 client nonce: " << input[2]);
}
// add client-first-message-bare to _authMessage
_authMessage += input[1] + "," + input[2] + ",";
_user = input[1].substr(2);
if (!authzId.empty() && _user != authzId) {
return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() <<
"SCRAM-SHA-1 user name " << _user << " does not match authzid " << authzId);
}
decodeSCRAMUsername(_user);
std::string clientNonce = input[2].substr(2);
// The authentication database is also the source database for the user.
User* userObj;
Status status = _saslAuthSession->getAuthorizationSession()->getAuthorizationManager().
acquireUser(_saslAuthSession->getOpCtxt(),
UserName(_user, _saslAuthSession->getAuthenticationDatabase()),
&userObj);
if (!status.isOK()) {
return StatusWith<bool>(status);
}
_creds = userObj->getCredentials();
UserName userName = userObj->getName();
_saslAuthSession->getAuthorizationSession()->getAuthorizationManager().
releaseUser(userObj);
// Check for authentication attempts of the __system user on
// systems started without a keyfile.
if (userName == internalSecurity.user->getName() &&
_creds.scram.salt.empty()) {
return StatusWith<bool>(ErrorCodes::AuthenticationFailed,
"It is not possible to authenticate as the __system user "
"on servers started without --keyFile parameter");
}
// Generate SCRAM credentials on the fly for mixed MONGODB-CR/SCRAM mode.
if (_creds.scram.salt.empty() && !_creds.password.empty()) {
// Use a default value of 5000 for the scramIterationCount when in mixed mode,
// overriding the default value (10000) used for SCRAM mode or the user-given value.
const int mixedModeScramIterationCount = 5000;
BSONObj scramCreds = scram::generateCredentials(_creds.password,
mixedModeScramIterationCount);
_creds.scram.iterationCount = scramCreds[scram::iterationCountFieldName].Int();
_creds.scram.salt = scramCreds[scram::saltFieldName].String();
_creds.scram.storedKey = scramCreds[scram::storedKeyFieldName].String();
_creds.scram.serverKey = scramCreds[scram::serverKeyFieldName].String();
}
// Generate server-first-message
// Create text-based nonce as base64 encoding of a binary blob of length multiple of 3
const int nonceLenQWords = 3;
uint64_t binaryNonce[nonceLenQWords];
scoped_ptr<SecureRandom> sr(SecureRandom::create());
binaryNonce[0] = sr->nextInt64();
binaryNonce[1] = sr->nextInt64();
binaryNonce[2] = sr->nextInt64();
_nonce = clientNonce +
base64::encode(reinterpret_cast<char*>(binaryNonce), sizeof(binaryNonce));
StringBuilder sb;
sb << "r=" << _nonce <<
",s=" << _creds.scram.salt <<
",i=" << _creds.scram.iterationCount;
*outputData = sb.str();
// add server-first-message to authMessage
_authMessage += *outputData + ",";
return StatusWith<bool>(false);
}
/**
* Parse client-final-message of the form:
* c=channel-binding(base64),r=client-nonce|server-nonce,p=ClientProof
*
* Generate successful authentication server-final-message on the form:
* v=ServerSignature
*
* or failed authentication server-final-message on the form:
* e=message
*
* NOTE: we are ignoring the channel binding part of the message
**/
StatusWith<bool> SaslSCRAMSHA1ServerConversation::_secondStep(const std::vector<string>& input,
std::string* outputData) {
if (input.size() != 3) {
return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() <<
"Incorrect number of arguments for second SCRAM-SHA-1 client message, got " <<
input.size() << " expected 3");
}
else if (!str::startsWith(input[0], "c=") || input[0].size() < 3) {
return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() <<
"Incorrect SCRAM-SHA-1 channel binding: " << input[0]);
}
else if (!str::startsWith(input[1], "r=") || input[1].size() < 6) {
return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() <<
"Incorrect SCRAM-SHA-1 client|server nonce: " << input[1]);
}
else if(!str::startsWith(input[2], "p=") || input[2].size() < 3) {
return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() <<
"Incorrect SCRAM-SHA-1 ClientProof: " << input[2]);
}
// add client-final-message-without-proof to authMessage
_authMessage += input[0] + "," + input[1];
// Concatenated nonce sent by client should equal the one in server-first-message
std::string nonce = input[1].substr(2);
if (nonce != _nonce) {
return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() <<
"Unmatched SCRAM-SHA-1 nonce received from client in second step, expected " <<
_nonce << " but received " << nonce);
}
std::string clientProof = input[2].substr(2);
// Do server side computations, compare storedKeys and generate client-final-message
// AuthMessage := client-first-message-bare + "," +
// server-first-message + "," +
// client-final-message-without-proof
// ClientSignature := HMAC(StoredKey, AuthMessage)
// ClientKey := ClientSignature XOR ClientProof
// ServerSignature := HMAC(ServerKey, AuthMessage)
unsigned int hashLen = 0;
unsigned char clientSignature[scram::hashSize];
std::string decodedStoredKey = base64::decode(_creds.scram.storedKey);
// ClientSignature := HMAC(StoredKey, AuthMessage)
fassert(18662, crypto::hmacSha1(
reinterpret_cast<const unsigned char*>(decodedStoredKey.c_str()),
scram::hashSize,
reinterpret_cast<const unsigned char*>(_authMessage.c_str()),
_authMessage.size(),
clientSignature,
&hashLen));
fassert(18658, hashLen == scram::hashSize);
try {
clientProof = base64::decode(clientProof);
}
catch (const DBException& ex) {
return StatusWith<bool>(ex.toStatus());
}
const unsigned char *decodedClientProof =
reinterpret_cast<const unsigned char*>(clientProof.c_str());
// ClientKey := ClientSignature XOR ClientProof
unsigned char clientKey[scram::hashSize];
for(size_t i=0; i<scram::hashSize; i++) {
clientKey[i] = clientSignature[i]^decodedClientProof[i];
}
// StoredKey := H(ClientKey)
unsigned char computedStoredKey[scram::hashSize];
fassert(18659, crypto::sha1(clientKey, scram::hashSize, computedStoredKey));
if (memcmp(decodedStoredKey.c_str(), computedStoredKey, scram::hashSize) != 0) {
return StatusWith<bool>(ErrorCodes::AuthenticationFailed,
mongoutils::str::stream() <<
"SCRAM-SHA-1 authentication failed, storedKey mismatch");
}
// ServerSignature := HMAC(ServerKey, AuthMessage)
unsigned char serverSignature[scram::hashSize];
std::string decodedServerKey = base64::decode(_creds.scram.serverKey);
fassert(18660, crypto::hmacSha1(
reinterpret_cast<const unsigned char*>(decodedServerKey.c_str()),
scram::hashSize,
reinterpret_cast<const unsigned char*>(_authMessage.c_str()),
_authMessage.size(),
serverSignature,
&hashLen));
fassert(18661, hashLen == scram::hashSize);
StringBuilder sb;
sb << "v=" << base64::encode(reinterpret_cast<char*>(serverSignature), scram::hashSize);
*outputData = sb.str();
return StatusWith<bool>(false);
}
} // namespace mongo
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