Vulnerability Discussion

Untrusted Certificate Authorities (CA) can issue certificates, but they may be issued by organizations or individuals that seek to compromise DoD systems or by organizations with insufficient security controls. If the CA used for verifying the certificate is not a DoD-approved CA, trust of this CA has not been established.

The DoD will only accept PKI-certificates obtained from a DoD-approved internal or external certificate authority. Reliance on CAs for the establishment of secure sessions includes, for example, the use of SSL/TLS certificates.

Check

Verify the directory containing the root certificates for the Ubuntu operating system (/etc/ssl/certs) only contains certificate files for DoD PKI-established certificate authorities.

Determine if "/etc/ssl/certs" only contains certificate files whose sha256 fingerprint match the fingerprint of DoD PKI-established certificate authorities with the following command:

$ for f in $(realpath /etc/ssl/certs/*); do openssl x509 -sha256 -in $f -noout -fingerprint | cut -d= -f2 | tr -d ':' | egrep -vw '(9676F287356C89A12683D65234098CB77C4F1C18F23C0E541DE0E196725B7EBE|B107B33F453E5510F68E513110C6F6944BACC263DF0137F821C1B3C2F8F863D2|559A5189452B13F8233F0022363C06F26E3C517C1D4B77445035959DF3244F74|1F4EDE9DC2A241F6521BF518424ACD49EBE84420E69DAF5BAC57AF1F8EE294A9)'; done

If any entry is found, this is a finding.

Fix

Configure the Ubuntu operating system to only allow the use of DoD PKI-established certificate authorities for verification of the establishment of protected sessions.

Edit the "/etc/ca-certificates.conf" file, adding the character "!" to the beginning of all uncommented lines that do not start with the "!" character with the following command:

$ sudo sed -i -E 's/^([^!#]+)/!\1/' /etc/ca-certificates.conf

Add at least one DoD certificate authority to the "/usr/local/share/ca-certificates" directory in the PEM format.

Update the "/etc/ssl/certs" directory with the following command:

$ sudo update-ca-certificates