Title

The system must use SMB client signing for connecting to samba servers using mount.cifs. (Cat III impact)

Discussion

Packet signing can prevent man-in-the-middle attacks which modify SMB packets in transit.

Check Content

If Samba is not in use, this is not applicable. To verify that Samba clients using mount.cifs must use packet signing, run the following command: # grep sec /etc/fstab /etc/mtab The output should show either "krb5i" or "ntlmv2i" in use. If it does not, this is a finding.

Fix Text

Require packet signing of clients who mount Samba shares using the "mount.cifs" program (e.g., those who specify shares in "/etc/fstab"). To do so, ensure signing options (either "sec=krb5i" or "sec=ntlmv2i") are used. See the "mount.cifs(8)" man page for more information. A Samba client should only communicate with servers who can support SMB packet signing.

Additional Identifiers

Rule ID: SV-218025r603264_rule

Vulnerability ID: V-218025

Group Title: SRG-OS-000480

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.