NixOS, for PKI-based authentication, must validate certificates by constructing a certification path (which includes status information) to an accepted trust anchor.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-268124	SRG-OS-000066-GPOS-00034	ANIX-00-000710	SV-268124r1039260_rule	2024-10-25	1

Description
Without path validation, an informed trust decision by the relying party cannot be made when presented with any certificate not already explicitly trusted. A trust anchor is an authoritative entity represented via a public key and associated data. It is used in the context of public key infrastructures, X.509 digital certificates, and DNSSEC. When there is a chain of trust, usually the top entity to be trusted becomes the trust anchor; it can be, for example, a Certification Authority (CA). A certification path starts with the subject certificate and proceeds through a number of intermediate certificates up to a trusted root certificate, typically issued by a trusted CA. This requirement verifies that a certification path to an accepted trust anchor is used for certificate validation and that the path includes status information. Path validation is necessary for a relying party to make an informed trust decision when presented with any certificate not already explicitly trusted. Status information for certification paths includes certificate revocation lists or online certificate status protocol responses. Validation of the certificate status information is out of scope for this requirement. Satisfies: SRG-OS-000066-GPOS-00034, SRG-OS-000403-GPOS-00182, SRG-OS-000775-GPOS-00230

Description

Without path validation, an informed trust decision by the relying party cannot be made when presented with any certificate not already explicitly trusted. A trust anchor is an authoritative entity represented via a public key and associated data. It is used in the context of public key infrastructures, X.509 digital certificates, and DNSSEC. When there is a chain of trust, usually the top entity to be trusted becomes the trust anchor; it can be, for example, a Certification Authority (CA). A certification path starts with the subject certificate and proceeds through a number of intermediate certificates up to a trusted root certificate, typically issued by a trusted CA. This requirement verifies that a certification path to an accepted trust anchor is used for certificate validation and that the path includes status information. Path validation is necessary for a relying party to make an informed trust decision when presented with any certificate not already explicitly trusted. Status information for certification paths includes certificate revocation lists or online certificate status protocol responses. Validation of the certificate status information is out of scope for this requirement. Satisfies: SRG-OS-000066-GPOS-00034, SRG-OS-000403-GPOS-00182, SRG-OS-000775-GPOS-00230

ℹ️ Check
Verify NixOS only allows the use of DOD PKI-established certificate authorities by running the following: $ nix-env -iA nixos.openssl $ openssl x509 -text -in /etc/sssd/pki/sssd_auth_ca_db.pem Certificate: Data: Version: 3 (0x2) Serial Number: 1 (0x1) Signature Algorithm: sha256WithRSAEncryption Issuer: C = US, O = U.S. Government, OU = DOD, OU = PKI, CN = DOD Root CA 3 Validity Not Before: Mar 20 18:46:41 2012 GMT Not After : Dec 30 18:46:41 2029 GMT Subject: C = US, O = U.S. Government, OU = DOD, OU = PKI, CN = DOD Root CA 3 Subject Public Key Info: Public Key Algorithm: rsaEncryption If the root CA file is not a DOD-issued certificate with a valid date and installed in the /etc/sssd/pki/sssd_auth_ca_db.pem location, this is a finding.

ℹ️ Check

Verify NixOS only allows the use of DOD PKI-established certificate authorities by running the following: $ nix-env -iA nixos.openssl $ openssl x509 -text -in /etc/sssd/pki/sssd_auth_ca_db.pem Certificate: Data: Version: 3 (0x2) Serial Number: 1 (0x1) Signature Algorithm: sha256WithRSAEncryption Issuer: C = US, O = U.S. Government, OU = DOD, OU = PKI, CN = DOD Root CA 3 Validity Not Before: Mar 20 18:46:41 2012 GMT Not After : Dec 30 18:46:41 2029 GMT Subject: C = US, O = U.S. Government, OU = DOD, OU = PKI, CN = DOD Root CA 3 Subject Public Key Info: Public Key Algorithm: rsaEncryption If the root CA file is not a DOD-issued certificate with a valid date and installed in the /etc/sssd/pki/sssd_auth_ca_db.pem location, this is a finding.

✔️ Fix
Configure /etc/nixos/configuration.nix to authenticate using DOD's root CA by adding the following configuration settings: services.sssd.enable = true; environment.etc."sssd/pki/sssd_auth_ca_db.pem".source = let certzip = pkgs.fetchzip { url = "https://dl.dod.cyber.mil/wp-content/uploads/pki-pke/zip/unclass-certificates_pkcs7_v5-6_dod.zip"; sha256 = "sha256-iwwJRXCnONk/LFddQlwy8KX9e9kVXW/QWDnX5qZFZjc="; }; in "${certzip}/DOD_PKE_CA_chain.pem"; Rebuild the system with the following command: $ sudo nixos-rebuild switch

✔️ Fix

Configure /etc/nixos/configuration.nix to authenticate using DOD's root CA by adding the following configuration settings: services.sssd.enable = true; environment.etc."sssd/pki/sssd_auth_ca_db.pem".source = let certzip = pkgs.fetchzip { url = "https://dl.dod.cyber.mil/wp-content/uploads/pki-pke/zip/unclass-certificates_pkcs7_v5-6_dod.zip"; sha256 = "sha256-iwwJRXCnONk/LFddQlwy8KX9e9kVXW/QWDnX5qZFZjc="; }; in "${certzip}/DOD_PKE_CA_chain.pem"; Rebuild the system with the following command: $ sudo nixos-rebuild switch