connection.go

package vertigo

// Copyright (c) 2019-2022 Micro Focus or one of its affiliates.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

import (
	"context"
	"crypto/md5"
	"crypto/sha512"
	"crypto/tls"
	"database/sql/driver"
	"encoding/binary"
	"fmt"
	"net"
	"net/url"
	"os"
	"strings"
	"sync"
	"time"

	"github.com/vertica/vertica-sql-go/common"
	"github.com/vertica/vertica-sql-go/logger"
	"github.com/vertica/vertica-sql-go/msgs"
)

var (
	connectionLogger = logger.New("connection")
)

const (
	tlsModeServer       = "server"
	tlsModeServerStrict = "server-strict"
	tlsModeNone         = "none"
)

type _tlsConfigs struct {
	m map[string]*tls.Config
	sync.RWMutex
}

func (t *_tlsConfigs) add(name string, config *tls.Config) error {
	t.Lock()
	defer t.Unlock()
	t.m[name] = config
	return nil
}

func (t *_tlsConfigs) get(name string) (*tls.Config, bool) {
	t.RLock()
	defer t.RUnlock()
	conf, ok := t.m[name]
	return conf, ok
}

var tlsConfigs = &_tlsConfigs{m: make(map[string]*tls.Config)}

//  db, err := sql.Open("vertica", "user@tcp(localhost:3306)/test?tlsmode=custom")
//  reserved modes: 'server', 'server-strict' or 'none'
func RegisterTLSConfig(name string, config *tls.Config) error {
	if name == tlsModeServer || name == tlsModeServerStrict || name == tlsModeNone {
		return fmt.Errorf("config name '%s' is reserved therefore cannot be used", name)
	}
	return tlsConfigs.add(name, config)
}

// Connection represents a connection to Vertica
type connection struct {
	driver.Conn

	conn             net.Conn
	connURL          *url.URL
	parameters       map[string]string
	clientPID        int
	backendPID       uint32
	cancelKey        uint32
	transactionState byte
	usePreparedStmts bool
	connHostsList    []string
	scratch          [512]byte
	sessionID        string
	serverTZOffset   string
	dead             bool // used if a ROLLBACK severity error is encountered
	sessMutex        sync.Mutex
}

// Begin - Begin starts and returns a new transaction. (DEPRECATED)
// From interface: sql.driver.Conn
func (v *connection) Begin() (driver.Tx, error) {
	return nil, nil
}

// BeginTx - Begin starts and returns a new transaction.
// From interface: sql.driver.ConnBeginTx
func (v *connection) BeginTx(ctx context.Context, opts driver.TxOptions) (driver.Tx, error) {
	connectionLogger.Trace("connection.BeginTx()")
	return newTransaction(ctx, v, opts)
}

// Close closes a connection to the Vertica DB. After calling close, you shouldn't use this connection anymore.
// From interface: sql.driver.Conn
func (v *connection) Close() error {
	connectionLogger.Trace("connection.Close()")

	v.sendMessage(&msgs.FETerminateMsg{})

	var result error = nil

	if v.conn != nil {
		result = v.conn.Close()
		v.conn = nil
	}

	return result
}

// PrepareContext returns a prepared statement, bound to this connection.
// context is for the preparation of the statement,
// it must not store the context within the statement itself.
// From interface: sql.driver.ConnPrepareContext
func (v *connection) PrepareContext(ctx context.Context, query string) (driver.Stmt, error) {

	s, err := newStmt(v, query)

	if err != nil {
		return nil, err
	}

	if v.usePreparedStmts {
		if err = s.prepareAndDescribe(); err != nil {
			return nil, err
		}
	}

	return s, nil
}

// Prepare returns a prepared statement, bound to this connection.
// From interface: sql.driver.Conn
func (v *connection) Prepare(query string) (driver.Stmt, error) {
	return v.PrepareContext(context.Background(), query)
}

// Ping implements the Pinger interface for connection. Use this to check for a valid connection state.
// This has to prepare AND execute the query in case prepared statements are disabled.
func (v *connection) Ping(ctx context.Context) error {
	stmt, err := v.PrepareContext(ctx, "select 1 as test")
	if err != nil {
		return driver.ErrBadConn
	}
	defer stmt.Close()
	// If we are preparing statements server side, successfully preparing verifies the connection
	if v.usePreparedStmts {
		return nil
	}
	queryContext := stmt.(driver.StmtQueryContext)
	rows, err := queryContext.QueryContext(ctx, nil)
	if err != nil {
		return driver.ErrBadConn
	}
	var val interface{}
	if err := rows.Next([]driver.Value{val}); err != nil {
		return driver.ErrBadConn
	}
	rows.Close()
	return nil
}

// ResetSession implements the SessionResetter interface for connection. This allows the sql
// package to evaluate the connection state when managing the connection pool.
func (v *connection) ResetSession(ctx context.Context) error {
	if v.dead {
		return driver.ErrBadConn
	}
	return v.Ping(ctx)
}

// newConnection constructs a new Vertica Connection object based on the connection string.
func newConnection(connString string) (*connection, error) {

	result := &connection{parameters: make(map[string]string), usePreparedStmts: true}

	var err error
	result.connURL, err = url.Parse(connString)

	if err != nil {
		return nil, err
	}

	result.clientPID = os.Getpid()
	result.sessionID = fmt.Sprintf("%s-%s-%d-%d", driverName, driverVersion, result.clientPID, time.Now().Unix())

	// Read the interpolate flag.
	if iFlag := result.connURL.Query().Get("use_prepared_statements"); iFlag != "" {
		result.usePreparedStmts = iFlag == "1"
	}

	// Read connection load balance flag.
	loadBalanceFlag := result.connURL.Query().Get("connection_load_balance")

	// Read connection failover flag.
	backupHostsStr := result.connURL.Query().Get("backup_server_node")
	if backupHostsStr == "" {
		result.connHostsList = []string{result.connURL.Host}
	} else {
		// Parse comma-seperated list of backup host-port pairs
		hosts := strings.Split(backupHostsStr, ",")
		// Push target host to front of the hosts list
		result.connHostsList = append([]string{result.connURL.Host}, hosts...)
	}

	// Read SSL/TLS flag.
	sslFlag := strings.ToLower(result.connURL.Query().Get("tlsmode"))
	if sslFlag == "" {
		sslFlag = tlsModeNone
	}

	result.conn, err = result.establishSocketConnection()

	if err != nil {
		return nil, err
	}

	// Load Balancing
	if loadBalanceFlag == "1" {
		if err = result.balanceLoad(); err != nil {
			return nil, err
		}
	}

	if sslFlag != tlsModeNone {
		if err = result.initializeSSL(sslFlag); err != nil {
			return nil, err
		}
	}

	if err = result.handshake(); err != nil {
		return nil, err
	}

	if err = result.initializeSession(); err != nil {
		return nil, err
	}

	return result, nil
}

func (v *connection) establishSocketConnection() (net.Conn, error) {
	// Failover: loop to try all hosts in the list
	err_msg := ""
	for i := 0; i < len(v.connHostsList); i++ {
		// net.Dial will resolve the host to multiple IP addresses,
		// and try each IP address in order until one succeeds.
		conn, err := net.Dial("tcp", v.connHostsList[i])
		if err != nil {
			err_msg += fmt.Sprintf("\n  '%s': %s", v.connHostsList[i], err.Error())
		} else {
			if len(err_msg) != 0 {
				connectionLogger.Debug("Failed to establish a connection to %s", err_msg)
			}
			connectionLogger.Debug("Established socket connection to %s", v.connHostsList[i])
			v.connHostsList = v.connHostsList[i:]
			return conn, err
		}
	}
	// All of the hosts failed
	return nil, fmt.Errorf("Failed to establish a connection to the primary server or any backup host.%s", err_msg)
}

func (v *connection) recvMessage() (msgs.BackEndMsg, error) {
	msgHeader := v.scratch[:5]

	var err error

	if err = v.readAll(msgHeader); err != nil {
		return nil, err
	}

	msgSize := int(binary.BigEndian.Uint32(msgHeader[1:]) - 4)

	msgBytes := v.scratch[5:]

	var y []byte
	if msgSize > 0 {
		if msgSize <= len(msgBytes) {
			y = msgBytes[:msgSize]
		} else {
			y = make([]byte, msgSize)
		}
		if err = v.readAll(y); err != nil {
			return nil, err
		}
	}

	bem, err := msgs.CreateBackEndMsg(msgHeader[0], y)

	if err != nil {
		return nil, err
	}

	// Print the message to stdout (for debugging purposes)
	if _, drm := bem.(*msgs.BEDataRowMsg); !drm {
		connectionLogger.Debug("<- " + bem.String())
	} else {
		connectionLogger.Trace("<- " + bem.String())
	}

	return bem, nil
}

func (v *connection) sendMessage(msg msgs.FrontEndMsg) error {
	return v.sendMessageTo(msg, v.conn)
}

func (v *connection) sendMessageTo(msg msgs.FrontEndMsg, conn net.Conn) error {
	var result error = nil

	msgBytes, msgTag := msg.Flatten()

	if msgTag != 0 {
		_, result = conn.Write([]byte{msgTag})
	}

	if result == nil {
		sizeBytes := v.scratch[:4]
		binary.BigEndian.PutUint32(sizeBytes, uint32(len(msgBytes)+4))

		_, result = conn.Write(sizeBytes)

		if result == nil && len(msgBytes) > 0 {
			size := 8192 // Max msg size, consistent with how the server works
			pos := 0
			var sent int
			for pos < len(msgBytes) {
				sent, result = conn.Write(msgBytes[pos:min(pos+size, len(msgBytes))])
				if result != nil {
					break
				}
				pos += sent
			}
		}
	}

	if result != nil {
		connectionLogger.Error("-> FAILED SENDING "+msg.String()+": %v", result.Error())
	} else {
		connectionLogger.Debug("-> " + msg.String())
	}

	return result
}

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func (v *connection) handshake() error {

	if v.connURL.User == nil {
		return fmt.Errorf("connection string must include a user name")
	}

	userName := v.connURL.User.Username()

	if len(userName) == 0 {
		return fmt.Errorf("connection string must have a non-empty user name")
	}

	if len(v.connURL.Path) <= 1 {
		return fmt.Errorf("connection string must include a database name")
	}

	path := v.connURL.Path[1:]

	msg := &msgs.FEStartupMsg{
		ProtocolVersion: protocolVersion,
		DriverName:      driverName,
		DriverVersion:   driverVersion,
		Username:        userName,
		Database:        path,
		SessionID:       v.sessionID,
		ClientPID:       v.clientPID,
	}

	if err := v.sendMessage(msg); err != nil {
		return err
	}

	for {
		bMsg, err := v.recvMessage()

		if err != nil {
			return err
		}

		switch msg := bMsg.(type) {
		case *msgs.BEErrorMsg:
			return errorMsgToVError(msg)
		case *msgs.BEReadyForQueryMsg:
			v.transactionState = msg.TransactionState
			return nil
		case *msgs.BEParamStatusMsg:
			v.parameters[msg.ParamName] = msg.ParamValue
		case *msgs.BEKeyDataMsg:
			v.backendPID = msg.BackendPID
			v.cancelKey = msg.CancelKey
		default:
			_, err = v.defaultMessageHandler(msg)
			if err != nil {
				return err
			}
		}
	}
}

// We have to be tricky here since we're inside of a connection, but trying to use interfaces of the
// driver class.
func (v *connection) initializeSession() error {

	stmt, err := newStmt(v, "select now()::timestamptz")

	if err != nil {
		return err
	}

	result, err := stmt.QueryContextRaw(context.Background(), []driver.NamedValue{})

	if err != nil {
		return err
	}

	firstRow := result.resultData.Peek()

	if len(result.Columns()) != 1 && result.Columns()[1] != "now" || firstRow == nil {
		return fmt.Errorf("unable to initialize session; functionality may be unreliable")
	}

	// Peek into the results manually.
	colData := firstRow.Columns()
	str := string(colData.Chunk())

	if len(str) < 23 {
		return fmt.Errorf("can't get server timezone: %s", str)
	}

	v.serverTZOffset = str[len(str)-3:]

	connectionLogger.Debug("Setting server timezone offset to %s", str[len(str)-3:])

	return nil
}

func (v *connection) defaultMessageHandler(bMsg msgs.BackEndMsg) (bool, error) {

	handled := true

	var err error = nil

	switch msg := bMsg.(type) {
	case *msgs.BEAuthenticationMsg:
		switch msg.Response {
		case common.AuthenticationOK:
			break
		case common.AuthenticationCleartextPassword:
			err = v.authSendPlainTextPassword()
		case common.AuthenticationMD5Password:
			err = v.authSendMD5Password(msg.ExtraAuthData)
		case common.AuthenticationSHA512Password:
			err = v.authSendSHA512Password(msg.ExtraAuthData)
		default:
			handled = false
			err = fmt.Errorf("unsupported authentication scheme: %d", msg.Response)
		}
	case *msgs.BENoticeMsg:
		break
	case *msgs.BEParamStatusMsg:
		connectionLogger.Debug("%v", msg)
	default:
		handled = false
		err = fmt.Errorf("unhandled message: %v", msg)
		connectionLogger.Warn("%v", err)
	}

	return handled, err
}

func (v *connection) readAll(buf []byte) error {
	readIndex := 0

	for {
		bytesRead, err := v.conn.Read(buf[readIndex:])

		if err != nil {
			return err
		}

		readIndex += bytesRead

		if readIndex == len(buf) {
			return nil
		}
	}
}

func (v *connection) balanceLoad() error {
	v.sendMessage(&msgs.FELoadBalanceMsg{})
	response := v.scratch[:1]

	var err error
	if err = v.readAll(response); err != nil {
		return err
	}

	if response[0] == 'N' {
		// keep existing connection
		connectionLogger.Debug("<- LoadBalanceResponse: N")
		connectionLogger.Warn("Load balancing requested but not supported by server")
		return nil
	}

	if response[0] != 'Y' {
		connectionLogger.Debug("<- LoadBalanceResponse: %c", response[0])
		return fmt.Errorf("Load balancing request gave unknown response: %c", response[0])
	}

	header := v.scratch[1:5]
	if err = v.readAll(header); err != nil {
		return err
	}
	msgSize := int(binary.BigEndian.Uint32(header) - 4)
	msgBytes := v.scratch[5:]

	var y []byte
	if msgSize > 0 {
		if msgSize <= len(msgBytes) {
			y = msgBytes[:msgSize]
		} else {
			y = make([]byte, msgSize)
		}
		if err = v.readAll(y); err != nil {
			return err
		}
	}

	bem, err := msgs.CreateBackEndMsg(response[0], y)
	if err != nil {
		return err
	}
	connectionLogger.Debug("<- " + bem.String())
	msg := bem.(*msgs.BELoadBalanceMsg)

	// v.connURL.Hostname() is used by initializeSSL(), so load balancing info should not write into v.connURL
	loadBalanceAddr := fmt.Sprintf("%s:%d", msg.Host, msg.Port)

	if v.connHostsList[0] == loadBalanceAddr {
		// Already connecting to the host
		return nil
	}

	// Push the new host onto the host list before connecting again.
	// Note that this leaves the originally-specified host as the first failover possibility
	v.connHostsList = append([]string{loadBalanceAddr}, v.connHostsList...)

	// Connect to new host
	v.conn.Close()
	v.conn, err = v.establishSocketConnection()

	if err != nil {
		return fmt.Errorf("cannot redirect to %s (%s)", loadBalanceAddr, err.Error())
	}

	return nil
}

func (v *connection) initializeSSL(sslFlag string) error {
	v.sendMessage(&msgs.FESSLMsg{})

	buf := v.scratch[:1]

	err := v.readAll(buf)

	if err != nil {
		return err
	}

	if buf[0] == 'N' {
		return fmt.Errorf("SSL/TLS is not enabled on this server")
	}

	if buf[0] != 'S' {
		return fmt.Errorf("SSL/TLS probe gave unknown response: %c", buf[0])
	}

	switch sslFlag {
	case tlsModeServer:
		connectionLogger.Info("enabling SSL/TLS server mode")
		v.conn = tls.Client(v.conn, &tls.Config{InsecureSkipVerify: true})
	case tlsModeServerStrict:
		connectionLogger.Info("enabling SSL/TLS server strict mode")
		v.conn = tls.Client(v.conn, &tls.Config{ServerName: v.connURL.Hostname()})
	default:
		// Custom mode is used for mutual ssl mode
		connectionLogger.Info("enabling SSL/TLS custom mode")
		config, ok := tlsConfigs.get(sslFlag)
		if !ok {
			err := fmt.Errorf("tls config %s not registered. See 'Using custom TLS config' in the README.md file", sslFlag)
			connectionLogger.Error(err.Error())
			return err
		}
		v.conn = tls.Client(v.conn, config)
		return nil
	}

	return nil
}

func (v *connection) authSendPlainTextPassword() error {
	passwd, isSet := v.connURL.User.Password()

	if !isSet {
		passwd = ""
	}

	msg := &msgs.FEPasswordMsg{PasswordData: passwd}

	return v.sendMessage(msg)
}

func (v *connection) authSendMD5Password(extraAuthData []byte) error {
	passwd, isSet := v.connURL.User.Password()

	if !isSet {
		passwd = ""
	}

	hash1 := fmt.Sprintf("%x", md5.Sum([]byte(passwd+v.connURL.User.Username())))
	hash2 := fmt.Sprintf("md5%x", md5.Sum(append([]byte(hash1), extraAuthData[0:4]...)))

	msg := &msgs.FEPasswordMsg{PasswordData: hash2}

	return v.sendMessage(msg)
}

func (v *connection) authSendSHA512Password(extraAuthData []byte) error {
	passwd, isSet := v.connURL.User.Password()

	if !isSet {
		passwd = ""
	}

	hash1 := fmt.Sprintf("%x", sha512.Sum512(append([]byte(passwd), extraAuthData[8:]...)))
	hash2 := fmt.Sprintf("sha512%x", sha512.Sum512(append([]byte(hash1), extraAuthData[0:4]...)))

	msg := &msgs.FEPasswordMsg{PasswordData: hash2}

	return v.sendMessage(msg)
}

func (v *connection) sync() error {
	err := v.sendMessage(&msgs.FESyncMsg{})

	if err != nil {
		return err
	}

	for true {
		bem, err := v.recvMessage()
		if err != nil {
			return err
		}

		_, ok := bem.(*msgs.BEReadyForQueryMsg)

		if ok {
			break
		}

		_, _ = v.defaultMessageHandler(bem)
	}

	return nil
}

func (v *connection) lockSessionMutex() {
	v.sessMutex.Lock()
}

func (v *connection) unlockSessionMutex() {
	v.sessMutex.Unlock()
}