SERVER-7596 Native SCRAM-SHA-1 client/shell implementation

8 files changed, 608 insertions, 5 deletions

diff --git a/src/mongo/client/native_sasl_client_session.cpp b/src/mongo/client/native_sasl_client_session.cpp
index 705626dc106..57e33eb9639 100644
--- a/src/mongo/client/native_sasl_client_session.cpp
+++ b/src/mongo/client/native_sasl_client_session.cpp
@@ -30,6 +30,9 @@
 #include "mongo/client/native_sasl_client_session.h"
 
 #include "mongo/base/init.h"
+#include "mongo/client/sasl_client_conversation.h"
+#include "mongo/client/sasl_plain_client_conversation.h"
+#include "mongo/client/sasl_scramsha1_client_conversation.h"
 #include "mongo/util/mongoutils/str.h"
 
 namespace mongo {
@@ -49,18 +52,38 @@ namespace {
     NativeSaslClientSession::NativeSaslClientSession() :
             SaslClientSession(),
             _step(0),
-            _done(false) {
+            _done(false), 
+            _saslConversation(NULL) { 
     }
 
     NativeSaslClientSession::~NativeSaslClientSession() {}
 
     Status NativeSaslClientSession::initialize() {
-        return Status(ErrorCodes::BadValue,
-                      mongoutils::str::stream() << "SASL authentication not supported in client");
+        if (_saslConversation)
+            return Status(ErrorCodes::AlreadyInitialized, 
+                "Cannot reinitialize NativeSaslClientSession.");
+
+        std::string mechanism = getParameter(parameterMechanism).toString();
+        if (mechanism == "PLAIN") {
+            _saslConversation.reset(new SaslPLAINClientConversation(this));
+        }
+        else if (mechanism == "SCRAM-SHA-1") {
+            _saslConversation.reset(new SaslSCRAMSHA1ClientConversation(this));
+        }
+        else {
+            return Status(ErrorCodes::BadValue,
+                mongoutils::str::stream() << "SASL mechanism " << mechanism << 
+                                             "is not supported");
+        }
+
+        return Status::OK();
     }
 
     Status NativeSaslClientSession::step(const StringData& inputData, std::string* outputData) {
-        return Status(ErrorCodes::BadValue,
-                      mongoutils::str::stream() << "SASL authentication not supported in client");
+        StatusWith<bool> status = _saslConversation->step(inputData, outputData);
+        if (status.isOK()) {
+            _done = status.getValue();
+        }
+        return status.getStatus();
     }
 }  // namespace
diff --git a/src/mongo/client/native_sasl_client_session.h b/src/mongo/client/native_sasl_client_session.h
index d80b9cc57ed..3bb83230025 100644
--- a/src/mongo/client/native_sasl_client_session.h
+++ b/src/mongo/client/native_sasl_client_session.h
@@ -25,10 +25,14 @@
  *    then also delete it in the license file.
  */
 
+#include <boost/scoped_ptr.hpp>
+
 #include "mongo/client/sasl_client_session.h"
 
 namespace mongo {
 
+    class SaslClientConversation;
+
     /**
      * Implementation of the client side of a SASL authentication conversation using the
      * native SASL implementation.
@@ -52,6 +56,9 @@ namespace mongo {
 
         /// See isDone().
         bool _done;
+   
+        /// The client side of a SASL authentication conversation.
+        boost::scoped_ptr<SaslClientConversation> _saslConversation;
     };
 
 }  // namespace mongo
diff --git a/src/mongo/client/sasl_client_conversation.cpp b/src/mongo/client/sasl_client_conversation.cpp
new file mode 100644
index 00000000000..637d6b14f5f
--- /dev/null
+++ b/src/mongo/client/sasl_client_conversation.cpp
@@ -0,0 +1,35 @@
+/*
+ *    Copyright (C) 2014 MongoDB Inc.  All Rights Reserved.
+ *
+ *    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/client/sasl_client_conversation.h"
+
+namespace mongo {
+    
+    SaslClientConversation::~SaslClientConversation() {};
+    
+}  // namespace mongo
diff --git a/src/mongo/client/sasl_client_conversation.h b/src/mongo/client/sasl_client_conversation.h
new file mode 100644
index 00000000000..f71e7ea0ad0
--- /dev/null
+++ b/src/mongo/client/sasl_client_conversation.h
@@ -0,0 +1,78 @@
+/*
+ *    Copyright (C) 2014 MongoDB Inc.  All Rights Reserved.
+ *
+ *    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.
+ */
+
+#pragma once
+
+#include <string>
+
+#include "mongo/base/disallow_copying.h"
+#include "mongo/base/string_data.h"
+
+namespace mongo {
+    
+    class SaslClientSession;
+    template <typename T> class StatusWith;
+    
+    /**
+     * Abstract class for implementing the clent-side
+     * of a SASL mechanism conversation.
+     */
+    class SaslClientConversation {
+        MONGO_DISALLOW_COPYING(SaslClientConversation);
+    public:
+        /**
+         * Implements the client side of a SASL authentication mechanism.
+         *
+         * "saslClientSession" is the corresponding SASLClientSession.
+         * "saslClientSession" must stay in scope until the SaslClientConversation's 
+         *  destructor completes.
+         * 
+         **/
+        explicit SaslClientConversation(SaslClientSession* saslClientSession) :
+            _saslClientSession(saslClientSession) {}
+
+        virtual ~SaslClientConversation();
+
+        /**
+         * Performs one step of the client side of the authentication session,
+         * consuming "inputData" and producing "*outputData".
+         *
+         * A return of Status::OK() indicates successful progress towards authentication. 
+         * A return of !Status::OK() indicates failed authentication
+         *
+         * A return of true means that the authentication process has finished.
+         * A return of false means that the authentication process has more steps.
+         *
+         */
+        virtual StatusWith<bool> step(const StringData& inputData, std::string* outputData) = 0;
+
+    protected:
+        SaslClientSession* _saslClientSession;
+    };
+
+}  // namespace mongo
diff --git a/src/mongo/client/sasl_plain_client_conversation.cpp b/src/mongo/client/sasl_plain_client_conversation.cpp
new file mode 100644
index 00000000000..b3436cc836e
--- /dev/null
+++ b/src/mongo/client/sasl_plain_client_conversation.cpp
@@ -0,0 +1,64 @@
+/*
+ *    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.
+ */
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/client/sasl_plain_client_conversation.h"
+
+#include "mongo/base/status_with.h"
+#include "mongo/client/sasl_client_session.h"
+#include "mongo/util/log.h"
+#include "mongo/util/password_digest.h"
+#include "mongo/util/text.h"
+
+namespace mongo {
+   
+    SaslPLAINClientConversation::SaslPLAINClientConversation(
+                                                    SaslClientSession* saslClientSession) :
+        SaslClientConversation(saslClientSession) {
+    }
+
+    SaslPLAINClientConversation::~SaslPLAINClientConversation() {};
+ 
+    StatusWith<bool> SaslPLAINClientConversation::step(const StringData& inputData, 
+                                                       std::string* outputData) {
+        // Create PLAIN message on the form: user\0user\0pwd
+        
+        StringBuilder sb;
+        sb << _saslClientSession->getParameter(SaslClientSession::parameterUser).toString() <<
+              '\0' <<
+              _saslClientSession->getParameter(SaslClientSession::parameterUser).toString() <<
+              '\0' <<
+              _saslClientSession->getParameter(SaslClientSession::parameterPassword).toString();
+
+        *outputData = sb.str();
+
+        return StatusWith<bool>(true);
+    }
+    
+}  // namespace mongo
diff --git a/src/mongo/client/sasl_plain_client_conversation.h b/src/mongo/client/sasl_plain_client_conversation.h
new file mode 100644
index 00000000000..ffd3f46b810
--- /dev/null
+++ b/src/mongo/client/sasl_plain_client_conversation.h
@@ -0,0 +1,56 @@
+/*
+ *    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.
+ */
+
+#pragma once
+
+#include <string>
+
+#include "mongo/base/disallow_copying.h"
+#include "mongo/base/status.h"
+#include "mongo/base/string_data.h"
+#include "mongo/client/sasl_client_conversation.h"
+
+namespace mongo {
+    /**
+     *  Client side authentication session for SASL PLAIN.
+     */
+    class SaslPLAINClientConversation : public SaslClientConversation {
+        MONGO_DISALLOW_COPYING(SaslPLAINClientConversation);
+    public:
+        /**
+         * Implements the client side of a SASL PLAIN mechanism session.
+         *
+         **/
+        explicit SaslPLAINClientConversation(SaslClientSession* saslClientSession); 
+
+        virtual ~SaslPLAINClientConversation();
+
+        virtual StatusWith<bool> step(const StringData& inputData, std::string* outputData);
+    };
+
+}  // namespace mongo
diff --git a/src/mongo/client/sasl_scramsha1_client_conversation.cpp b/src/mongo/client/sasl_scramsha1_client_conversation.cpp
new file mode 100644
index 00000000000..1fdb171b52f
--- /dev/null
+++ b/src/mongo/client/sasl_scramsha1_client_conversation.cpp
@@ -0,0 +1,252 @@
+/*
+ *    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.
+ */
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/client/sasl_scramsha1_client_conversation.h"
+
+#include <boost/algorithm/string/replace.hpp>
+#ifdef MONGO_SSL
+#include <openssl/sha.h>
+#include <openssl/evp.h>
+#include <openssl/hmac.h>
+#endif
+
+#include "mongo/base/parse_number.h"
+#include "mongo/client/sasl_client_session.h"
+#include "mongo/platform/random.h"
+#include "mongo/util/base64.h"
+#include "mongo/util/mongoutils/str.h"
+#include "mongo/util/password_digest.h"
+#include "mongo/util/text.h"
+
+namespace mongo {
+    SaslSCRAMSHA1ClientConversation::SaslSCRAMSHA1ClientConversation(
+                                                    SaslClientSession* saslClientSession) :
+        SaslClientConversation(saslClientSession),
+        _step(0),
+        _authMessage(""),
+        _clientNonce("") {
+    }
+
+    SaslSCRAMSHA1ClientConversation::~SaslSCRAMSHA1ClientConversation(){
+        // clear the _saltedPassword memory
+        memset(_saltedPassword, 0, scram::hashSize);
+    }
+
+    StatusWith<bool> SaslSCRAMSHA1ClientConversation::step(const StringData& inputData, 
+                                                           std::string* outputData) {
+        std::vector<std::string> input = StringSplitter::split(inputData.toString(), ",");
+        _step++;
+
+        switch (_step) {
+            case 1: 
+                return _firstStep(outputData);
+            case 2:
+                // Append server-first-message to _authMessage
+                _authMessage += inputData.toString() + ",";
+                return _secondStep(input, outputData);
+            case 3:
+                return _thirdStep(input, outputData);
+            default:
+                return StatusWith<bool>(ErrorCodes::AuthenticationFailed,
+                                        mongoutils::str::stream() << 
+                                        "Invalid SCRAM-SHA-1 authentication step: " << _step);
+        }
+    }
+   
+    /* 
+     * RFC 5802 specifies that in SCRAM user names characters ',' and '=' are encoded as
+     * =2C and =3D respectively.
+     */
+    static void encodeSCRAMUsername(std::string& user) {
+        boost::replace_all(user, ",", "=2C");
+        boost::replace_all(user, "=", "=3D");
+    }
+
+    /*
+     * Generate client-first-message of the form:
+     * n,a=authzid,n=encoded-username,r=client-nonce
+     */
+    StatusWith<bool> SaslSCRAMSHA1ClientConversation::_firstStep(std::string* outputData) {
+#ifndef MONGO_SSL
+        return StatusWith<bool>(ErrorCodes::InternalError,
+            "The server is not compiled with SSL support");
+#else
+        // 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();
+       
+        std::string user = 
+            _saslClientSession->getParameter(SaslClientSession::parameterUser).toString();
+        encodeSCRAMUsername(user);
+        std::string clientNonce = base64::encode(reinterpret_cast<char*>(binaryNonce), 
+                                                 sizeof(binaryNonce));
+       
+        // Append client-first-message-bare to authMessage
+        _authMessage = "n=" + user + ",r=" + clientNonce + ",";
+
+        StringBuilder sb;
+        sb << "n,,n=" << user <<
+              ",r=" << clientNonce;
+        *outputData = sb.str();
+
+        return StatusWith<bool>(false);
+
+#endif // MONGO_SSL
+    }
+
+    /** 
+     * Parse server-first-message on the form:
+     * r=client-nonce|server-nonce,s=user-salt,i=iteration-count
+     *
+     * Generate client-final-message of the form:
+     * c=channel-binding(base64),r=client-nonce|server-nonce,p=ClientProof
+     *
+     **/
+    StatusWith<bool> SaslSCRAMSHA1ClientConversation::_secondStep(const std::vector<string>& input, 
+                                                                  std::string* outputData) {
+#ifndef MONGO_SSL
+        return StatusWith<bool>(ErrorCodes::InternalError, 
+            "The server is not compiled with SSL support");
+#else
+        if (input.size() != 3) {
+            return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() << 
+                "Incorrect number of arguments for first SCRAM-SHA-1 server message, got " << 
+                input.size() << " expected 3");
+        }
+        else if (!str::startsWith(input[0], "r=") || input[0].size() < 2) {
+            return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() << 
+                "Incorrect SCRAM-SHA-1 client|server nonce: " << input[0]);
+        }
+        else if (!str::startsWith(input[1], "s=") || input[1].size() < 6) {
+            return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() << 
+                "Incorrect SCRAM-SHA-1 salt: " << input[1]);
+        }
+        else if(!str::startsWith(input[2], "i=") || input[2].size() < 3) {
+            return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() << 
+                "Incorrect SCRAM-SHA-1 iteration count: " << input[2]);
+        }
+
+        std::string nonce = input[0].substr(2);
+        if(!str::startsWith(nonce, _clientNonce)) {
+            return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() << 
+                "Server SCRAM-SHA-1 nonce does not match client nonce" << input[2]);
+        }
+
+        std::string salt = input[1].substr(2);
+        int iterationCount;
+        
+        Status status = parseNumberFromStringWithBase(input[2].substr(2), 10, &iterationCount);
+        if (status != Status::OK()) {
+            return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() << 
+                "Failed to parse SCRAM-SHA-1 iteration count: " << input[2]);
+        }
+
+        // Append client-final-message-without-proof to _authMessage
+        _authMessage += "c=biws,r=" + nonce;
+
+        std::string decodedSalt;
+        try {
+            decodedSalt = base64::decode(salt);
+        }
+        catch (const DBException& ex) {
+            return StatusWith<bool>(ex.toStatus());
+        }
+
+        scram::generateSaltedPassword(
+                            _saslClientSession->getParameter(SaslClientSession::parameterPassword),
+                            reinterpret_cast<const unsigned char*>(decodedSalt.c_str()),
+                            decodedSalt.size(),
+                            iterationCount,
+                            _saltedPassword);
+       
+        std::string clientProof = scram::generateClientProof(_saltedPassword, _authMessage);
+        
+        StringBuilder sb;
+        sb << "c=biws,r=" << nonce << ",p=" << clientProof; 
+        *outputData = sb.str();
+
+        return StatusWith<bool>(false);
+#endif // MONGO_SSL
+    }
+
+    /** 
+     * Verify server-final-message on the form:
+     * v=ServerSignature 
+     * 
+     * or failed authentication server-final-message on the form:
+     * e=message
+     **/
+    StatusWith<bool> SaslSCRAMSHA1ClientConversation::_thirdStep(const std::vector<string>& input, 
+                                                                  std::string* outputData) {
+#ifndef MONGO_SSL
+        return StatusWith<bool>(ErrorCodes::InternalError, 
+            "The server is not compiled with SSL support");
+#else
+
+        if (input.size() != 1) {
+            return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() << 
+                "Incorrect number of arguments for final SCRAM-SHA-1 server message, got " << 
+                input.size() << " expected 1");
+        }
+        else if (input[0].size() < 3) {
+            return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() << 
+                "Incorrect SCRAM-SHA-1 server message length: " << input[0]);
+        }
+        else if (str::startsWith(input[0], "e=")) {
+            return StatusWith<bool>(ErrorCodes::AuthenticationFailed, mongoutils::str::stream() << 
+                "SCRAM-SHA-1 authentication failure: " << input[0].substr(2));
+        }
+        else if (!str::startsWith(input[0], "v=")) {
+            return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() << 
+                "Incorrect SCRAM-SHA-1 ServerSignature: " << input[0]);
+        }
+
+        bool validServerSignature = 
+            scram::verifyServerSignature(_saltedPassword, _authMessage, input[0].substr(2));
+
+        if (!validServerSignature) {
+            *outputData = "e=Invalid server signature";
+            return StatusWith<bool>(ErrorCodes::BadValue, mongoutils::str::stream() << 
+                    "Client failed to verify SCRAM-SHA-1 ServerSignature, received " <<
+                    input[0].substr(2));
+        }
+
+        *outputData = "";
+
+        return StatusWith<bool>(true);
+#endif // MONGO_SSL
+    }
+}  // namespace mongo
diff --git a/src/mongo/client/sasl_scramsha1_client_conversation.h b/src/mongo/client/sasl_scramsha1_client_conversation.h
new file mode 100644
index 00000000000..668588bc03f
--- /dev/null
+++ b/src/mongo/client/sasl_scramsha1_client_conversation.h
@@ -0,0 +1,88 @@
+/*
+ *    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.
+ */
+
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include "mongo/base/disallow_copying.h"
+#include "mongo/base/status.h"
+#include "mongo/base/string_data.h"
+#include "mongo/client/sasl_client_conversation.h"
+#include "mongo/db/auth/mechanism_scram.h"
+#include "mongo/db/auth/user.h"
+
+namespace mongo {
+    /**
+     *  Client side authentication session for SASL PLAIN.
+     */
+    class SaslSCRAMSHA1ClientConversation : public SaslClientConversation {
+        MONGO_DISALLOW_COPYING(SaslSCRAMSHA1ClientConversation);
+    public:
+        /**
+         * Implements the client side of a SASL PLAIN mechanism session.
+         **/
+        explicit SaslSCRAMSHA1ClientConversation(SaslClientSession* saslClientSession); 
+
+        virtual ~SaslSCRAMSHA1ClientConversation();
+
+        /**
+         * Takes one step in a SCRAM-SHA-1 conversation.
+         *
+         * @return !Status::OK() for failure. The boolean part indicates if the
+         * authentication conversation is finished or not.
+         *
+         **/
+        virtual StatusWith<bool> step(const StringData& inputData, std::string* outputData);
+
+    private:
+        /**
+         * Generates client-first-message.
+         **/
+        StatusWith<bool> _firstStep(std::string* outputData);
+        
+        /** 
+         * Parses server-first-message and generate client-final-message.
+         **/  
+        StatusWith<bool> _secondStep(const std::vector<string>& input, std::string* outputData);
+        
+        /**
+         * Generates client-first-message.
+         **/
+        StatusWith<bool> _thirdStep(const std::vector<string>& input, std::string* outputData);
+        
+        int _step;
+        std::string _authMessage;
+        unsigned char _saltedPassword[scram::hashSize];
+ 
+        // client and server nonce concatenated
+        std::string _clientNonce;
+    };
+
+}  // namespace mongo