/**
 *    Copyright (C) 2018-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    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
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    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 Server Side 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/commands/authentication_commands.h"

#include <string>
#include <vector>

#include "mongo/base/status.h"
#include "mongo/bson/mutable/algorithm.h"
#include "mongo/bson/mutable/document.h"
#include "mongo/client/sasl_client_authenticate.h"
#include "mongo/config.h"
#include "mongo/db/audit.h"
#include "mongo/db/auth/authorization_session.h"
#include "mongo/db/auth/privilege.h"
#include "mongo/db/auth/sasl_options.h"
#include "mongo/db/auth/security_key.h"
#include "mongo/db/auth/user_name.h"
#include "mongo/db/client.h"
#include "mongo/db/commands.h"
#include "mongo/db/commands/test_commands_enabled.h"
#include "mongo/db/operation_context.h"
#include "mongo/platform/random.h"
#include "mongo/stdx/memory.h"
#include "mongo/transport/session.h"
#include "mongo/util/concurrency/mutex.h"
#include "mongo/util/log.h"
#include "mongo/util/net/ssl_manager.h"
#include "mongo/util/net/ssl_types.h"
#include "mongo/util/text.h"

namespace mongo {
namespace {

static bool _isX509AuthDisabled;
static const char _nonceAuthenticationDisabledMessage[] =
    "Challenge-response authentication using getnonce and authenticate commands is disabled.";
static const char _x509AuthenticationDisabledMessage[] = "x.509 authentication is disabled.";

#ifdef MONGO_CONFIG_SSL
Status _authenticateX509(OperationContext* opCtx, const UserName& user, const BSONObj& cmdObj) {
    if (!getSSLManager()) {
        return Status(ErrorCodes::ProtocolError,
                      "SSL support is required for the MONGODB-X509 mechanism.");
    }
    if (user.getDB() != "$external") {
        return Status(ErrorCodes::ProtocolError,
                      "X.509 authentication must always use the $external database.");
    }

    Client* client = Client::getCurrent();
    AuthorizationSession* authorizationSession = AuthorizationSession::get(client);
    auto clientName = SSLPeerInfo::forSession(client->session()).subjectName;
    uassert(ErrorCodes::AuthenticationFailed,
            "No verified subject name available from client",
            !clientName.empty());

    if (!getSSLManager()->getSSLConfiguration().hasCA) {
        return Status(ErrorCodes::AuthenticationFailed,
                      "Unable to verify x.509 certificate, as no CA has been provided.");
    } else if (user.getUser() != clientName.toString()) {
        return Status(ErrorCodes::AuthenticationFailed,
                      "There is no x.509 client certificate matching the user.");
    } else {
        // Handle internal cluster member auth, only applies to server-server connections
        if (getSSLManager()->getSSLConfiguration().isClusterMember(clientName)) {
            int clusterAuthMode = serverGlobalParams.clusterAuthMode.load();
            if (clusterAuthMode == ServerGlobalParams::ClusterAuthMode_undefined ||
                clusterAuthMode == ServerGlobalParams::ClusterAuthMode_keyFile) {
                return Status(ErrorCodes::AuthenticationFailed,
                              "The provided certificate "
                              "can only be used for cluster authentication, not client "
                              "authentication. The current configuration does not allow "
                              "x.509 cluster authentication, check the --clusterAuthMode flag");
            }
            authorizationSession->grantInternalAuthorization();
        }
        // Handle normal client authentication, only applies to client-server connections
        else {
            if (_isX509AuthDisabled) {
                return Status(ErrorCodes::BadValue, _x509AuthenticationDisabledMessage);
            }
            Status status = authorizationSession->addAndAuthorizeUser(opCtx, user);
            if (!status.isOK()) {
                return status;
            }
        }
        return Status::OK();
    }
}
#endif  // MONGO_CONFIG_SSL

class CmdAuthenticate : public BasicCommand {
public:
    AllowedOnSecondary secondaryAllowed(ServiceContext*) const override {
        return AllowedOnSecondary::kAlways;
    }
    std::string help() const override {
        return "internal";
    }
    virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
        return false;
    }
    bool requiresAuth() const override {
        return false;
    }
    virtual void addRequiredPrivileges(const std::string& dbname,
                                       const BSONObj& cmdObj,
                                       std::vector<Privilege>* out) const {}  // No auth required

    CmdAuthenticate() : BasicCommand("authenticate") {}
    bool run(OperationContext* opCtx,
             const std::string& dbname,
             const BSONObj& cmdObj,
             BSONObjBuilder& result);

private:
    /**
     * Completes the authentication of "user" using "mechanism" and parameters from "cmdObj".
     *
     * Returns Status::OK() on success.  All other statuses indicate failed authentication.  The
     * entire status returned here may always be used for logging.  However, if the code is
     * AuthenticationFailed, the "reason" field of the return status may contain information
     * that should not be revealed to the connected client.
     *
     * Other than AuthenticationFailed, common returns are BadValue, indicating unsupported
     * mechanism, and ProtocolError, indicating an error in the use of the authentication
     * protocol.
     */
    Status _authenticate(OperationContext* opCtx,
                         const std::string& mechanism,
                         const UserName& user,
                         const BSONObj& cmdObj);
} cmdAuthenticate;

/**
 * Returns a random 64-bit nonce.
 *
 * Previously, this command would have been called prior to {authenticate: ...}
 * when using the MONGODB-CR authentication mechanism.
 * Since that mechanism has been removed from MongoDB 3.8,
 * it is nominally no longer required.
 *
 * Unfortunately, mongo-tools uses a connection library
 * which optimistically invokes {getnonce: 1} upon connection
 * under the assumption that it will eventually be used as part
 * of "classic" authentication.
 * If the command dissapeared, then all of mongo-tools would
 * fail to connect, despite using SCRAM-SHA-1 or another valid
 * auth mechanism. Thus, we have to keep this command around for now.
 *
 * Note that despite nonces being available, they are not bound
 * to the AuthorizationSession anymore, and the authenticate
 * command doesn't acknowledge their existence.
 */
class CmdGetNonce : public BasicCommand {
public:
    CmdGetNonce() : BasicCommand("getnonce"), _random(SecureRandom::create()) {}

    AllowedOnSecondary secondaryAllowed(ServiceContext*) const override {
        return AllowedOnSecondary::kAlways;
    }

    std::string help() const final {
        return "internal";
    }

    bool supportsWriteConcern(const BSONObj& cmd) const final {
        return false;
    }

    bool requiresAuth() const override {
        return false;
    }
    void addRequiredPrivileges(const std::string& dbname,
                               const BSONObj& cmdObj,
                               std::vector<Privilege>* out) const final {
        // No auth required since this command was explicitly part
        // of an authentication workflow.
    }

    bool run(OperationContext* opCtx,
             const std::string&,
             const BSONObj& cmdObj,
             BSONObjBuilder& result) final {
        auto n = getNextNonce();
        std::stringstream ss;
        ss << std::hex << n;
        result.append("nonce", ss.str());
        return true;
    }

private:
    int64_t getNextNonce() {
        stdx::lock_guard<SimpleMutex> lk(_randMutex);
        return _random->nextInt64();
    }

    SimpleMutex _randMutex;  // Synchronizes accesses to _random.
    std::unique_ptr<SecureRandom> _random;
} cmdGetNonce;

bool CmdAuthenticate::run(OperationContext* opCtx,
                          const std::string& dbname,
                          const BSONObj& cmdObj,
                          BSONObjBuilder& result) {
    if (!serverGlobalParams.quiet.load()) {
        mutablebson::Document cmdToLog(cmdObj, mutablebson::Document::kInPlaceDisabled);
        log() << " authenticate db: " << dbname << " " << cmdToLog;
    }
    std::string mechanism = cmdObj.getStringField("mechanism");
    if (mechanism.empty()) {
        uasserted(ErrorCodes::BadValue, "Auth mechanism not specified");
    }

    UserName user(cmdObj.getStringField("user"), dbname);
#ifdef MONGO_CONFIG_SSL
    if (mechanism == kX509AuthMechanism && user.getUser().empty()) {
        auto& sslPeerInfo = SSLPeerInfo::forSession(opCtx->getClient()->session());
        user = UserName(sslPeerInfo.subjectName.toString(), dbname);
    }
#endif
    uassert(ErrorCodes::AuthenticationFailed, "No user name provided", !user.getUser().empty());

    if (getTestCommandsEnabled() && user.getDB() == "admin" &&
        user.getUser() == internalSecurity.user->getName().getUser()) {
        // Allows authenticating as the internal user against the admin database.  This is to
        // support the auth passthrough test framework on mongos (since you can't use the local
        // database on a mongos, so you can't auth as the internal user without this).
        user = internalSecurity.user->getName();
    }

    Status status = _authenticate(opCtx, mechanism, user, cmdObj);
    audit::logAuthentication(Client::getCurrent(), mechanism, user, status.code());
    if (!status.isOK()) {
        if (!serverGlobalParams.quiet.load()) {
            auto const client = opCtx->getClient();
            log() << "Failed to authenticate " << user
                  << (client->hasRemote() ? (" from client " + client->getRemote().toString()) : "")
                  << " with mechanism " << mechanism << ": " << status;
        }
        sleepmillis(saslGlobalParams.authFailedDelay.load());
        if (status.code() == ErrorCodes::AuthenticationFailed) {
            // Statuses with code AuthenticationFailed may contain messages we do not wish to
            // reveal to the user, so we return a status with the message "auth failed".
            uasserted(ErrorCodes::AuthenticationFailed, "auth failed");
        } else {
            uassertStatusOK(status);
        }
        return false;
    }
    result.append("dbname", user.getDB());
    result.append("user", user.getUser());
    return true;
}

Status CmdAuthenticate::_authenticate(OperationContext* opCtx,
                                      const std::string& mechanism,
                                      const UserName& user,
                                      const BSONObj& cmdObj) {
#ifdef MONGO_CONFIG_SSL
    if (mechanism == kX509AuthMechanism) {
        return _authenticateX509(opCtx, user, cmdObj);
    }
#endif
    return Status(ErrorCodes::BadValue, "Unsupported mechanism: " + mechanism);
}

class CmdLogout : public BasicCommand {
public:
    AllowedOnSecondary secondaryAllowed(ServiceContext*) const override {
        return AllowedOnSecondary::kAlways;
    }
    virtual void addRequiredPrivileges(const std::string& dbname,
                                       const BSONObj& cmdObj,
                                       std::vector<Privilege>* out) const {}  // No auth required
    std::string help() const override {
        return "de-authenticate";
    }
    virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
        return false;
    }
    CmdLogout() : BasicCommand("logout") {}
    bool run(OperationContext* opCtx,
             const std::string& dbname,
             const BSONObj& cmdObj,
             BSONObjBuilder& result) {
        AuthorizationSession* authSession = AuthorizationSession::get(Client::getCurrent());
        authSession->logoutDatabase(dbname);
        if (getTestCommandsEnabled() && dbname == "admin") {
            // Allows logging out as the internal user against the admin database, however
            // this actually logs out of the local database as well. This is to
            // support the auth passthrough test framework on mongos (since you can't use the
            // local database on a mongos, so you can't logout as the internal user
            // without this).
            authSession->logoutDatabase("local");
        }
        return true;
    }
} cmdLogout;

}  // namespace

void disableAuthMechanism(StringData authMechanism) {
    if (authMechanism == kX509AuthMechanism) {
        _isX509AuthDisabled = true;
    }
}

}  // namespace mongo