forked from hirochachacha/go-smb2
/
server.go
273 lines (226 loc) · 7.76 KB
/
server.go
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package ntlm
import (
"bytes"
"crypto/hmac"
"crypto/md5"
"crypto/rand"
"crypto/rc4"
"errors"
"strings"
)
// NTLM v2 server
type Server struct {
targetName string
accounts map[string]string // User: Password
nmsg []byte
cmsg []byte
session *Session
}
func NewServer(targetName string) *Server {
return &Server{
targetName: targetName,
accounts: make(map[string]string),
}
}
func (s *Server) AddAccount(user, password string) {
s.accounts[user] = password
}
func (s *Server) Challenge(nmsg []byte) (cmsg []byte, err error) {
// NegotiateMessage
// 0-8: Signature
// 8-12: MessageType
// 12-16: NegotiateFlags
// 16-24: DomainNameFields
// 24-32: WorkstationFields
// 32-40: Version
// 40-: Payload
s.nmsg = nmsg
if len(nmsg) < 32 {
return nil, errors.New("message length is too short")
}
if !bytes.Equal(nmsg[:8], signature) {
return nil, errors.New("invalid signature")
}
if le.Uint32(nmsg[8:12]) != NtLmNegotiate {
return nil, errors.New("invalid message type")
}
flags := le.Uint32(nmsg[12:16]) & defaultFlags
// ChallengeMessage
// 0-8: Signature
// 8-12: MessageType
// 12-20: TargetNameFields
// 20-24: NegotiateFlags
// 24-32: ServerChallenge
// 32-40: _
// 40-48: TargetInfoFields
// 48-56: Version
// 56-: Payload
off := 48
if flags&NTLMSSP_NEGOTIATE_VERSION != 0 {
off += 8
}
targetName := encodeString(s.targetName)
cmsg = make([]byte, off+len(targetName)+4)
copy(cmsg[:8], signature)
le.PutUint32(cmsg[8:12], NtLmChallenge)
le.PutUint32(cmsg[20:24], flags)
if targetName != nil && flags&NTLMSSP_REQUEST_TARGET != 0 {
len := copy(cmsg[off:], targetName)
le.PutUint16(cmsg[12:14], uint16(len))
le.PutUint16(cmsg[14:16], uint16(len))
le.PutUint32(cmsg[16:20], uint32(off))
off += len
}
if flags&NTLMSSP_NEGOTIATE_TARGET_INFO != 0 {
len := copy(cmsg[off:], []byte{0x00, 0x00, 0x00, 0x00}) // AvId: MsvAvEOL, AvLen: 0
le.PutUint16(cmsg[40:42], uint16(len))
le.PutUint16(cmsg[42:44], uint16(len))
le.PutUint32(cmsg[44:48], uint32(off))
off += len
}
_, err = rand.Read(cmsg[24:32])
if err != nil {
return nil, err
}
if flags&NTLMSSP_NEGOTIATE_VERSION != 0 {
copy(cmsg[48:56], version)
}
s.cmsg = cmsg
return cmsg, nil
}
func (s *Server) Authenticate(amsg []byte) (err error) {
// AuthenticateMessage
// 0-8: Signature
// 8-12: MessageType
// 12-20: LmChallengeResponseFields
// 20-28: NtChallengeResponseFields
// 28-36: DomainNameFields
// 36-44: UserNameFields
// 44-52: WorkstationFields
// 52-60: EncryptedRandomSessionKeyFields
// 60-64: NegotiateFlags
// 64-72: Version
// 72-88: MIC
// 88-: Payload
if len(amsg) < 64 {
return errors.New("message length is too short")
}
if !bytes.Equal(amsg[:8], signature) {
return errors.New("invalid signature")
}
if le.Uint32(amsg[8:12]) != NtLmAuthenticate {
return errors.New("invalid message type")
}
flags := le.Uint32(amsg[60:64])
ntChallengeResponseLen := le.Uint16(amsg[20:22]) // amsg.NtChallengeResponseLen
ntChallengeResponseMaxLen := le.Uint16(amsg[22:24]) // amsg.NtChallengeResponseMaxLen
if ntChallengeResponseMaxLen < ntChallengeResponseLen {
return errors.New("invalid LM challenge format")
}
ntChallengeResponseBufferOffset := le.Uint32(amsg[24:28]) // amsg.NtChallengeResponseBufferOffset
if len(amsg) < int(ntChallengeResponseBufferOffset+uint32(ntChallengeResponseLen)) {
return errors.New("invalid LM challenge format")
}
ntChallengeResponse := amsg[ntChallengeResponseBufferOffset : ntChallengeResponseBufferOffset+uint32(ntChallengeResponseLen)] // amsg.NtChallengeResponse
domainNameLen := le.Uint16(amsg[28:30]) // amsg.DomainNameLen
domainNameMaxLen := le.Uint16(amsg[30:32]) // amsg.DomainNameMaxLen
if domainNameMaxLen < domainNameLen {
return errors.New("invalid domain name format")
}
domainNameBufferOffset := le.Uint32(amsg[32:36]) // amsg.DomainNameBufferOffset
if len(amsg) < int(domainNameBufferOffset+uint32(domainNameLen)) {
return errors.New("invalid domain name format")
}
domainName := amsg[domainNameBufferOffset : domainNameBufferOffset+uint32(domainNameLen)] // amsg.DomainName
userNameLen := le.Uint16(amsg[36:38]) // amsg.UserNameLen
userNameMaxLen := le.Uint16(amsg[38:40]) // amsg.UserNameMaxLen
if userNameMaxLen < userNameLen {
return errors.New("invalid user name format")
}
userNameBufferOffset := le.Uint32(amsg[40:44]) // amsg.UserNameBufferOffset
if len(amsg) < int(userNameBufferOffset+uint32(userNameLen)) {
return errors.New("invalid user name format")
}
userName := amsg[userNameBufferOffset : userNameBufferOffset+uint32(userNameLen)] // amsg.UserName
encryptedRandomSessionKeyLen := le.Uint16(amsg[52:54]) // amsg.EncryptedRandomSessionKeyLen
encryptedRandomSessionKeyMaxLen := le.Uint16(amsg[54:56]) // amsg.EncryptedRandomSessionKeyMaxLen
if encryptedRandomSessionKeyMaxLen < encryptedRandomSessionKeyLen {
return errors.New("invalid user name format")
}
encryptedRandomSessionKeyBufferOffset := le.Uint32(amsg[56:60]) // amsg.EncryptedRandomSessionKeyBufferOffset
if len(amsg) < int(encryptedRandomSessionKeyBufferOffset+uint32(encryptedRandomSessionKeyLen)) {
return errors.New("invalid user name format")
}
encryptedRandomSessionKey := amsg[encryptedRandomSessionKeyBufferOffset : encryptedRandomSessionKeyBufferOffset+uint32(encryptedRandomSessionKeyLen)] // amsg.EncryptedRandomSessionKey
if len(userName) != 0 || len(ntChallengeResponse) != 0 {
user := decodeString(userName)
expectedNtChallengeResponse := make([]byte, len(ntChallengeResponse))
ntlmv2ClientChallenge := ntChallengeResponse[16:]
USER := encodeString(strings.ToUpper(user))
password := encodeString(s.accounts[user])
h := hmac.New(md5.New, ntowfv2(USER, password, domainName))
serverChallenge := s.cmsg[24:32]
timeStamp := ntlmv2ClientChallenge[8:16]
clientChallenge := ntlmv2ClientChallenge[16:24]
targetInfo := ntlmv2ClientChallenge[28:]
encodeNtlmv2Response(expectedNtChallengeResponse, h, serverChallenge, clientChallenge, timeStamp, bytesEncoder(targetInfo))
if !bytes.Equal(ntChallengeResponse, expectedNtChallengeResponse) {
return errors.New("login failure")
}
session := new(Session)
session.isClientSide = false
session.user = user
session.negotiateFlags = flags
h.Reset()
h.Write(ntChallengeResponse[:16])
sessionBaseKey := h.Sum(nil)
keyExchangeKey := sessionBaseKey // if ntlm version == 2
if flags&NTLMSSP_NEGOTIATE_KEY_EXCH != 0 {
session.exportedSessionKey = make([]byte, 16)
cipher, err := rc4.NewCipher(keyExchangeKey)
if err != nil {
return err
}
cipher.XORKeyStream(session.exportedSessionKey, encryptedRandomSessionKey)
} else {
session.exportedSessionKey = keyExchangeKey
}
if infoMap, ok := parseAvPairs(targetInfo); ok {
if avFlags, ok := infoMap[MsvAvFlags]; ok && le.Uint32(avFlags)&0x02 != 0 {
MIC := make([]byte, 16)
if flags&NTLMSSP_NEGOTIATE_VERSION != 0 {
copy(MIC, amsg[72:88])
copy(amsg[72:88], zero[:])
} else {
copy(MIC, amsg[64:80])
copy(amsg[64:80], zero[:])
}
h = hmac.New(md5.New, session.exportedSessionKey)
h.Write(s.nmsg)
h.Write(s.cmsg)
h.Write(amsg)
if !bytes.Equal(MIC, h.Sum(nil)) {
return errors.New("login failure")
}
}
}
{
session.clientSigningKey = signKey(flags, session.exportedSessionKey, true)
session.serverSigningKey = signKey(flags, session.exportedSessionKey, false)
session.clientHandle, err = rc4.NewCipher(sealKey(flags, session.exportedSessionKey, true))
if err != nil {
return err
}
session.serverHandle, err = rc4.NewCipher(sealKey(flags, session.exportedSessionKey, false))
if err != nil {
return err
}
}
s.session = session
return nil
}
return errors.New("credential is empty")
}
func (s *Server) Session() *Session {
return s.session
}