forgejo/vendor/github.com/denisenkom/go-mssqldb/tds.go
2019-12-28 17:14:38 +00:00

916 lines
22 KiB
Go

package mssql
import (
"context"
"crypto/tls"
"crypto/x509"
"encoding/binary"
"errors"
"fmt"
"io"
"io/ioutil"
"net"
"sort"
"strconv"
"strings"
"unicode/utf16"
"unicode/utf8"
)
func parseInstances(msg []byte) map[string]map[string]string {
results := map[string]map[string]string{}
if len(msg) > 3 && msg[0] == 5 {
out_s := string(msg[3:])
tokens := strings.Split(out_s, ";")
instdict := map[string]string{}
got_name := false
var name string
for _, token := range tokens {
if got_name {
instdict[name] = token
got_name = false
} else {
name = token
if len(name) == 0 {
if len(instdict) == 0 {
break
}
results[strings.ToUpper(instdict["InstanceName"])] = instdict
instdict = map[string]string{}
continue
}
got_name = true
}
}
}
return results
}
func getInstances(ctx context.Context, d Dialer, address string) (map[string]map[string]string, error) {
conn, err := d.DialContext(ctx, "udp", address+":1434")
if err != nil {
return nil, err
}
defer conn.Close()
deadline, _ := ctx.Deadline()
conn.SetDeadline(deadline)
_, err = conn.Write([]byte{3})
if err != nil {
return nil, err
}
var resp = make([]byte, 16*1024-1)
read, err := conn.Read(resp)
if err != nil {
return nil, err
}
return parseInstances(resp[:read]), nil
}
// tds versions
const (
verTDS70 = 0x70000000
verTDS71 = 0x71000000
verTDS71rev1 = 0x71000001
verTDS72 = 0x72090002
verTDS73A = 0x730A0003
verTDS73 = verTDS73A
verTDS73B = 0x730B0003
verTDS74 = 0x74000004
)
// packet types
// https://msdn.microsoft.com/en-us/library/dd304214.aspx
const (
packSQLBatch packetType = 1
packRPCRequest = 3
packReply = 4
// 2.2.1.7 Attention: https://msdn.microsoft.com/en-us/library/dd341449.aspx
// 4.19.2 Out-of-Band Attention Signal: https://msdn.microsoft.com/en-us/library/dd305167.aspx
packAttention = 6
packBulkLoadBCP = 7
packTransMgrReq = 14
packNormal = 15
packLogin7 = 16
packSSPIMessage = 17
packPrelogin = 18
)
// prelogin fields
// http://msdn.microsoft.com/en-us/library/dd357559.aspx
const (
preloginVERSION = 0
preloginENCRYPTION = 1
preloginINSTOPT = 2
preloginTHREADID = 3
preloginMARS = 4
preloginTRACEID = 5
preloginTERMINATOR = 0xff
)
const (
encryptOff = 0 // Encryption is available but off.
encryptOn = 1 // Encryption is available and on.
encryptNotSup = 2 // Encryption is not available.
encryptReq = 3 // Encryption is required.
)
type tdsSession struct {
buf *tdsBuffer
loginAck loginAckStruct
database string
partner string
columns []columnStruct
tranid uint64
logFlags uint64
log optionalLogger
routedServer string
routedPort uint16
}
const (
logErrors = 1
logMessages = 2
logRows = 4
logSQL = 8
logParams = 16
logTransaction = 32
logDebug = 64
)
type columnStruct struct {
UserType uint32
Flags uint16
ColName string
ti typeInfo
}
type keySlice []uint8
func (p keySlice) Len() int { return len(p) }
func (p keySlice) Less(i, j int) bool { return p[i] < p[j] }
func (p keySlice) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
// http://msdn.microsoft.com/en-us/library/dd357559.aspx
func writePrelogin(w *tdsBuffer, fields map[uint8][]byte) error {
var err error
w.BeginPacket(packPrelogin, false)
offset := uint16(5*len(fields) + 1)
keys := make(keySlice, 0, len(fields))
for k, _ := range fields {
keys = append(keys, k)
}
sort.Sort(keys)
// writing header
for _, k := range keys {
err = w.WriteByte(k)
if err != nil {
return err
}
err = binary.Write(w, binary.BigEndian, offset)
if err != nil {
return err
}
v := fields[k]
size := uint16(len(v))
err = binary.Write(w, binary.BigEndian, size)
if err != nil {
return err
}
offset += size
}
err = w.WriteByte(preloginTERMINATOR)
if err != nil {
return err
}
// writing values
for _, k := range keys {
v := fields[k]
written, err := w.Write(v)
if err != nil {
return err
}
if written != len(v) {
return errors.New("Write method didn't write the whole value")
}
}
return w.FinishPacket()
}
func readPrelogin(r *tdsBuffer) (map[uint8][]byte, error) {
packet_type, err := r.BeginRead()
if err != nil {
return nil, err
}
struct_buf, err := ioutil.ReadAll(r)
if err != nil {
return nil, err
}
if packet_type != 4 {
return nil, errors.New("Invalid respones, expected packet type 4, PRELOGIN RESPONSE")
}
offset := 0
results := map[uint8][]byte{}
for true {
rec_type := struct_buf[offset]
if rec_type == preloginTERMINATOR {
break
}
rec_offset := binary.BigEndian.Uint16(struct_buf[offset+1:])
rec_len := binary.BigEndian.Uint16(struct_buf[offset+3:])
value := struct_buf[rec_offset : rec_offset+rec_len]
results[rec_type] = value
offset += 5
}
return results, nil
}
// OptionFlags2
// http://msdn.microsoft.com/en-us/library/dd304019.aspx
const (
fLanguageFatal = 1
fODBC = 2
fTransBoundary = 4
fCacheConnect = 8
fIntSecurity = 0x80
)
// TypeFlags
const (
// 4 bits for fSQLType
// 1 bit for fOLEDB
fReadOnlyIntent = 32
)
type login struct {
TDSVersion uint32
PacketSize uint32
ClientProgVer uint32
ClientPID uint32
ConnectionID uint32
OptionFlags1 uint8
OptionFlags2 uint8
TypeFlags uint8
OptionFlags3 uint8
ClientTimeZone int32
ClientLCID uint32
HostName string
UserName string
Password string
AppName string
ServerName string
CtlIntName string
Language string
Database string
ClientID [6]byte
SSPI []byte
AtchDBFile string
ChangePassword string
}
type loginHeader struct {
Length uint32
TDSVersion uint32
PacketSize uint32
ClientProgVer uint32
ClientPID uint32
ConnectionID uint32
OptionFlags1 uint8
OptionFlags2 uint8
TypeFlags uint8
OptionFlags3 uint8
ClientTimeZone int32
ClientLCID uint32
HostNameOffset uint16
HostNameLength uint16
UserNameOffset uint16
UserNameLength uint16
PasswordOffset uint16
PasswordLength uint16
AppNameOffset uint16
AppNameLength uint16
ServerNameOffset uint16
ServerNameLength uint16
ExtensionOffset uint16
ExtensionLenght uint16
CtlIntNameOffset uint16
CtlIntNameLength uint16
LanguageOffset uint16
LanguageLength uint16
DatabaseOffset uint16
DatabaseLength uint16
ClientID [6]byte
SSPIOffset uint16
SSPILength uint16
AtchDBFileOffset uint16
AtchDBFileLength uint16
ChangePasswordOffset uint16
ChangePasswordLength uint16
SSPILongLength uint32
}
// convert Go string to UTF-16 encoded []byte (littleEndian)
// done manually rather than using bytes and binary packages
// for performance reasons
func str2ucs2(s string) []byte {
res := utf16.Encode([]rune(s))
ucs2 := make([]byte, 2*len(res))
for i := 0; i < len(res); i++ {
ucs2[2*i] = byte(res[i])
ucs2[2*i+1] = byte(res[i] >> 8)
}
return ucs2
}
func ucs22str(s []byte) (string, error) {
if len(s)%2 != 0 {
return "", fmt.Errorf("Illegal UCS2 string length: %d", len(s))
}
buf := make([]uint16, len(s)/2)
for i := 0; i < len(s); i += 2 {
buf[i/2] = binary.LittleEndian.Uint16(s[i:])
}
return string(utf16.Decode(buf)), nil
}
func manglePassword(password string) []byte {
var ucs2password []byte = str2ucs2(password)
for i, ch := range ucs2password {
ucs2password[i] = ((ch<<4)&0xff | (ch >> 4)) ^ 0xA5
}
return ucs2password
}
// http://msdn.microsoft.com/en-us/library/dd304019.aspx
func sendLogin(w *tdsBuffer, login login) error {
w.BeginPacket(packLogin7, false)
hostname := str2ucs2(login.HostName)
username := str2ucs2(login.UserName)
password := manglePassword(login.Password)
appname := str2ucs2(login.AppName)
servername := str2ucs2(login.ServerName)
ctlintname := str2ucs2(login.CtlIntName)
language := str2ucs2(login.Language)
database := str2ucs2(login.Database)
atchdbfile := str2ucs2(login.AtchDBFile)
changepassword := str2ucs2(login.ChangePassword)
hdr := loginHeader{
TDSVersion: login.TDSVersion,
PacketSize: login.PacketSize,
ClientProgVer: login.ClientProgVer,
ClientPID: login.ClientPID,
ConnectionID: login.ConnectionID,
OptionFlags1: login.OptionFlags1,
OptionFlags2: login.OptionFlags2,
TypeFlags: login.TypeFlags,
OptionFlags3: login.OptionFlags3,
ClientTimeZone: login.ClientTimeZone,
ClientLCID: login.ClientLCID,
HostNameLength: uint16(utf8.RuneCountInString(login.HostName)),
UserNameLength: uint16(utf8.RuneCountInString(login.UserName)),
PasswordLength: uint16(utf8.RuneCountInString(login.Password)),
AppNameLength: uint16(utf8.RuneCountInString(login.AppName)),
ServerNameLength: uint16(utf8.RuneCountInString(login.ServerName)),
CtlIntNameLength: uint16(utf8.RuneCountInString(login.CtlIntName)),
LanguageLength: uint16(utf8.RuneCountInString(login.Language)),
DatabaseLength: uint16(utf8.RuneCountInString(login.Database)),
ClientID: login.ClientID,
SSPILength: uint16(len(login.SSPI)),
AtchDBFileLength: uint16(utf8.RuneCountInString(login.AtchDBFile)),
ChangePasswordLength: uint16(utf8.RuneCountInString(login.ChangePassword)),
}
offset := uint16(binary.Size(hdr))
hdr.HostNameOffset = offset
offset += uint16(len(hostname))
hdr.UserNameOffset = offset
offset += uint16(len(username))
hdr.PasswordOffset = offset
offset += uint16(len(password))
hdr.AppNameOffset = offset
offset += uint16(len(appname))
hdr.ServerNameOffset = offset
offset += uint16(len(servername))
hdr.CtlIntNameOffset = offset
offset += uint16(len(ctlintname))
hdr.LanguageOffset = offset
offset += uint16(len(language))
hdr.DatabaseOffset = offset
offset += uint16(len(database))
hdr.SSPIOffset = offset
offset += uint16(len(login.SSPI))
hdr.AtchDBFileOffset = offset
offset += uint16(len(atchdbfile))
hdr.ChangePasswordOffset = offset
offset += uint16(len(changepassword))
hdr.Length = uint32(offset)
var err error
err = binary.Write(w, binary.LittleEndian, &hdr)
if err != nil {
return err
}
_, err = w.Write(hostname)
if err != nil {
return err
}
_, err = w.Write(username)
if err != nil {
return err
}
_, err = w.Write(password)
if err != nil {
return err
}
_, err = w.Write(appname)
if err != nil {
return err
}
_, err = w.Write(servername)
if err != nil {
return err
}
_, err = w.Write(ctlintname)
if err != nil {
return err
}
_, err = w.Write(language)
if err != nil {
return err
}
_, err = w.Write(database)
if err != nil {
return err
}
_, err = w.Write(login.SSPI)
if err != nil {
return err
}
_, err = w.Write(atchdbfile)
if err != nil {
return err
}
_, err = w.Write(changepassword)
if err != nil {
return err
}
return w.FinishPacket()
}
func readUcs2(r io.Reader, numchars int) (res string, err error) {
buf := make([]byte, numchars*2)
_, err = io.ReadFull(r, buf)
if err != nil {
return "", err
}
return ucs22str(buf)
}
func readUsVarChar(r io.Reader) (res string, err error) {
numchars, err := readUshort(r)
if err != nil {
return
}
return readUcs2(r, int(numchars))
}
func writeUsVarChar(w io.Writer, s string) (err error) {
buf := str2ucs2(s)
var numchars int = len(buf) / 2
if numchars > 0xffff {
panic("invalid size for US_VARCHAR")
}
err = binary.Write(w, binary.LittleEndian, uint16(numchars))
if err != nil {
return
}
_, err = w.Write(buf)
return
}
func readBVarChar(r io.Reader) (res string, err error) {
numchars, err := readByte(r)
if err != nil {
return "", err
}
// A zero length could be returned, return an empty string
if numchars == 0 {
return "", nil
}
return readUcs2(r, int(numchars))
}
func writeBVarChar(w io.Writer, s string) (err error) {
buf := str2ucs2(s)
var numchars int = len(buf) / 2
if numchars > 0xff {
panic("invalid size for B_VARCHAR")
}
err = binary.Write(w, binary.LittleEndian, uint8(numchars))
if err != nil {
return
}
_, err = w.Write(buf)
return
}
func readBVarByte(r io.Reader) (res []byte, err error) {
length, err := readByte(r)
if err != nil {
return
}
res = make([]byte, length)
_, err = io.ReadFull(r, res)
return
}
func readUshort(r io.Reader) (res uint16, err error) {
err = binary.Read(r, binary.LittleEndian, &res)
return
}
func readByte(r io.Reader) (res byte, err error) {
var b [1]byte
_, err = r.Read(b[:])
res = b[0]
return
}
// Packet Data Stream Headers
// http://msdn.microsoft.com/en-us/library/dd304953.aspx
type headerStruct struct {
hdrtype uint16
data []byte
}
const (
dataStmHdrQueryNotif = 1 // query notifications
dataStmHdrTransDescr = 2 // MARS transaction descriptor (required)
dataStmHdrTraceActivity = 3
)
// Query Notifications Header
// http://msdn.microsoft.com/en-us/library/dd304949.aspx
type queryNotifHdr struct {
notifyId string
ssbDeployment string
notifyTimeout uint32
}
func (hdr queryNotifHdr) pack() (res []byte) {
notifyId := str2ucs2(hdr.notifyId)
ssbDeployment := str2ucs2(hdr.ssbDeployment)
res = make([]byte, 2+len(notifyId)+2+len(ssbDeployment)+4)
b := res
binary.LittleEndian.PutUint16(b, uint16(len(notifyId)))
b = b[2:]
copy(b, notifyId)
b = b[len(notifyId):]
binary.LittleEndian.PutUint16(b, uint16(len(ssbDeployment)))
b = b[2:]
copy(b, ssbDeployment)
b = b[len(ssbDeployment):]
binary.LittleEndian.PutUint32(b, hdr.notifyTimeout)
return res
}
// MARS Transaction Descriptor Header
// http://msdn.microsoft.com/en-us/library/dd340515.aspx
type transDescrHdr struct {
transDescr uint64 // transaction descriptor returned from ENVCHANGE
outstandingReqCnt uint32 // outstanding request count
}
func (hdr transDescrHdr) pack() (res []byte) {
res = make([]byte, 8+4)
binary.LittleEndian.PutUint64(res, hdr.transDescr)
binary.LittleEndian.PutUint32(res[8:], hdr.outstandingReqCnt)
return res
}
func writeAllHeaders(w io.Writer, headers []headerStruct) (err error) {
// Calculating total length.
var totallen uint32 = 4
for _, hdr := range headers {
totallen += 4 + 2 + uint32(len(hdr.data))
}
// writing
err = binary.Write(w, binary.LittleEndian, totallen)
if err != nil {
return err
}
for _, hdr := range headers {
var headerlen uint32 = 4 + 2 + uint32(len(hdr.data))
err = binary.Write(w, binary.LittleEndian, headerlen)
if err != nil {
return err
}
err = binary.Write(w, binary.LittleEndian, hdr.hdrtype)
if err != nil {
return err
}
_, err = w.Write(hdr.data)
if err != nil {
return err
}
}
return nil
}
func sendSqlBatch72(buf *tdsBuffer, sqltext string, headers []headerStruct, resetSession bool) (err error) {
buf.BeginPacket(packSQLBatch, resetSession)
if err = writeAllHeaders(buf, headers); err != nil {
return
}
_, err = buf.Write(str2ucs2(sqltext))
if err != nil {
return
}
return buf.FinishPacket()
}
// 2.2.1.7 Attention: https://msdn.microsoft.com/en-us/library/dd341449.aspx
// 4.19.2 Out-of-Band Attention Signal: https://msdn.microsoft.com/en-us/library/dd305167.aspx
func sendAttention(buf *tdsBuffer) error {
buf.BeginPacket(packAttention, false)
return buf.FinishPacket()
}
type auth interface {
InitialBytes() ([]byte, error)
NextBytes([]byte) ([]byte, error)
Free()
}
// SQL Server AlwaysOn Availability Group Listeners are bound by DNS to a
// list of IP addresses. So if there is more than one, try them all and
// use the first one that allows a connection.
func dialConnection(ctx context.Context, c *Connector, p connectParams) (conn net.Conn, err error) {
var ips []net.IP
ips, err = net.LookupIP(p.host)
if err != nil {
ip := net.ParseIP(p.host)
if ip == nil {
return nil, err
}
ips = []net.IP{ip}
}
if len(ips) == 1 {
d := c.getDialer(&p)
addr := net.JoinHostPort(ips[0].String(), strconv.Itoa(int(resolveServerPort(p.port))))
conn, err = d.DialContext(ctx, "tcp", addr)
} else {
//Try Dials in parallel to avoid waiting for timeouts.
connChan := make(chan net.Conn, len(ips))
errChan := make(chan error, len(ips))
portStr := strconv.Itoa(int(resolveServerPort(p.port)))
for _, ip := range ips {
go func(ip net.IP) {
d := c.getDialer(&p)
addr := net.JoinHostPort(ip.String(), portStr)
conn, err := d.DialContext(ctx, "tcp", addr)
if err == nil {
connChan <- conn
} else {
errChan <- err
}
}(ip)
}
// Wait for either the *first* successful connection, or all the errors
wait_loop:
for i, _ := range ips {
select {
case conn = <-connChan:
// Got a connection to use, close any others
go func(n int) {
for i := 0; i < n; i++ {
select {
case conn := <-connChan:
conn.Close()
case <-errChan:
}
}
}(len(ips) - i - 1)
// Remove any earlier errors we may have collected
err = nil
break wait_loop
case err = <-errChan:
}
}
}
// Can't do the usual err != nil check, as it is possible to have gotten an error before a successful connection
if conn == nil {
f := "Unable to open tcp connection with host '%v:%v': %v"
return nil, fmt.Errorf(f, p.host, resolveServerPort(p.port), err.Error())
}
return conn, err
}
func connect(ctx context.Context, c *Connector, log optionalLogger, p connectParams) (res *tdsSession, err error) {
dialCtx := ctx
if p.dial_timeout > 0 {
var cancel func()
dialCtx, cancel = context.WithTimeout(ctx, p.dial_timeout)
defer cancel()
}
// if instance is specified use instance resolution service
if p.instance != "" && p.port == 0 {
p.instance = strings.ToUpper(p.instance)
d := c.getDialer(&p)
instances, err := getInstances(dialCtx, d, p.host)
if err != nil {
f := "Unable to get instances from Sql Server Browser on host %v: %v"
return nil, fmt.Errorf(f, p.host, err.Error())
}
strport, ok := instances[p.instance]["tcp"]
if !ok {
f := "No instance matching '%v' returned from host '%v'"
return nil, fmt.Errorf(f, p.instance, p.host)
}
port, err := strconv.ParseUint(strport, 0, 16)
if err != nil {
f := "Invalid tcp port returned from Sql Server Browser '%v': %v"
return nil, fmt.Errorf(f, strport, err.Error())
}
p.port = port
}
initiate_connection:
conn, err := dialConnection(dialCtx, c, p)
if err != nil {
return nil, err
}
toconn := newTimeoutConn(conn, p.conn_timeout)
outbuf := newTdsBuffer(p.packetSize, toconn)
sess := tdsSession{
buf: outbuf,
log: log,
logFlags: p.logFlags,
}
instance_buf := []byte(p.instance)
instance_buf = append(instance_buf, 0) // zero terminate instance name
var encrypt byte
if p.disableEncryption {
encrypt = encryptNotSup
} else if p.encrypt {
encrypt = encryptOn
} else {
encrypt = encryptOff
}
fields := map[uint8][]byte{
preloginVERSION: {0, 0, 0, 0, 0, 0},
preloginENCRYPTION: {encrypt},
preloginINSTOPT: instance_buf,
preloginTHREADID: {0, 0, 0, 0},
preloginMARS: {0}, // MARS disabled
}
err = writePrelogin(outbuf, fields)
if err != nil {
return nil, err
}
fields, err = readPrelogin(outbuf)
if err != nil {
return nil, err
}
encryptBytes, ok := fields[preloginENCRYPTION]
if !ok {
return nil, fmt.Errorf("Encrypt negotiation failed")
}
encrypt = encryptBytes[0]
if p.encrypt && (encrypt == encryptNotSup || encrypt == encryptOff) {
return nil, fmt.Errorf("Server does not support encryption")
}
if encrypt != encryptNotSup {
var config tls.Config
if p.certificate != "" {
pem, err := ioutil.ReadFile(p.certificate)
if err != nil {
return nil, fmt.Errorf("Cannot read certificate %q: %v", p.certificate, err)
}
certs := x509.NewCertPool()
certs.AppendCertsFromPEM(pem)
config.RootCAs = certs
}
if p.trustServerCertificate {
config.InsecureSkipVerify = true
}
config.ServerName = p.hostInCertificate
// fix for https://github.com/denisenkom/go-mssqldb/issues/166
// Go implementation of TLS payload size heuristic algorithm splits single TDS package to multiple TCP segments,
// while SQL Server seems to expect one TCP segment per encrypted TDS package.
// Setting DynamicRecordSizingDisabled to true disables that algorithm and uses 16384 bytes per TLS package
config.DynamicRecordSizingDisabled = true
// setting up connection handler which will allow wrapping of TLS handshake packets inside TDS stream
handshakeConn := tlsHandshakeConn{buf: outbuf}
passthrough := passthroughConn{c: &handshakeConn}
tlsConn := tls.Client(&passthrough, &config)
err = tlsConn.Handshake()
passthrough.c = toconn
outbuf.transport = tlsConn
if err != nil {
return nil, fmt.Errorf("TLS Handshake failed: %v", err)
}
if encrypt == encryptOff {
outbuf.afterFirst = func() {
outbuf.transport = toconn
}
}
}
login := login{
TDSVersion: verTDS74,
PacketSize: uint32(outbuf.PackageSize()),
Database: p.database,
OptionFlags2: fODBC, // to get unlimited TEXTSIZE
HostName: p.workstation,
ServerName: p.host,
AppName: p.appname,
TypeFlags: p.typeFlags,
}
auth, auth_ok := getAuth(p.user, p.password, p.serverSPN, p.workstation)
if auth_ok {
login.SSPI, err = auth.InitialBytes()
if err != nil {
return nil, err
}
login.OptionFlags2 |= fIntSecurity
defer auth.Free()
} else {
login.UserName = p.user
login.Password = p.password
}
err = sendLogin(outbuf, login)
if err != nil {
return nil, err
}
// processing login response
success := false
for {
tokchan := make(chan tokenStruct, 5)
go processResponse(context.Background(), &sess, tokchan, nil)
for tok := range tokchan {
switch token := tok.(type) {
case sspiMsg:
sspi_msg, err := auth.NextBytes(token)
if err != nil {
return nil, err
}
if sspi_msg != nil && len(sspi_msg) > 0 {
outbuf.BeginPacket(packSSPIMessage, false)
_, err = outbuf.Write(sspi_msg)
if err != nil {
return nil, err
}
err = outbuf.FinishPacket()
if err != nil {
return nil, err
}
sspi_msg = nil
}
case loginAckStruct:
success = true
sess.loginAck = token
case error:
return nil, fmt.Errorf("Login error: %s", token.Error())
case doneStruct:
if token.isError() {
return nil, fmt.Errorf("Login error: %s", token.getError())
}
goto loginEnd
}
}
}
loginEnd:
if !success {
return nil, fmt.Errorf("Login failed")
}
if sess.routedServer != "" {
toconn.Close()
p.host = sess.routedServer
p.port = uint64(sess.routedPort)
if !p.hostInCertificateProvided {
p.hostInCertificate = sess.routedServer
}
goto initiate_connection
}
return &sess, nil
}