NGINX must be configured to use a Certificate Revocation List (CRL) for certificate path validation and revocation. (Online Certificate Status Protocol [OCSP] is the preferred configuration.)

Severity
Group ID
Group Title
Version
Rule ID
Date
STIG Version
mediumV-278391SRG-APP-000175NGNX-APP-000720SV-278391r1171925_rule2026-01-071
Description
Without path validation, an informed trust decision by the relying party cannot be made when presented with any certificate not already explicitly trusted. To meet this requirement, the information system must create trusted channels between itself and remote trusted authorized IT product (e.g., syslog server) entities that protect the confidentiality and integrity of communications. The information system must create trusted paths between itself and remote administrators and users that protect the confidentiality and integrity of communications. A trust anchor is an authoritative entity represented via a public key and associated data. It is most often used in the context of public key infrastructures, X.509 digital certificates, and DNSSEC. However, applications that do not use a trusted path are not approved for nonlocal and remote management of DOD information systems. Use of SSHv2 to establish a trusted channel is approved. Use of FTP, TELNET, HTTP, and SNMPV1 is not approved since they violate the trusted channel rule set. Use of web management tools that are not validated by common criteria may also violate trusted channel rule set. 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-APP-000175, SRG-APP-000401
ℹ️ Check
If using OCSP for certificate revocation, this requirement is Not Applicable. Determine the path to NGINX config file: # nginx -qT | grep "# configuration" # configuration file /etc/nginx/nginx.conf: Note: The default NGINX configuration is "/etc/nginx/nginx.conf", though various files may also be included. # cat <path to config> Check the http { blocks for the following example: http { server { listen 443 ssl; server_name example.com; ssl_certificate /etc/nginx/ssl/server.crt; ssl_certificate_key /etc/nginx/ssl/server.key; ssl_client_certificate /etc/nginx/ssl/ca.crt; ssl_verify_client on; ssl_crl /etc/nginx/ssl/crl.pem; ssl_ocsp on; ssl_ocsp_responder http://ocsp.disa.mil; ssl_stapling on; ssl_stapling_verify on; ssl_stapling_file /etc/nginx/ssl/ocsp_cache.pem; ssl_stapling_responder_timeout 3s; # Timeout for OCSP responder queries ssl_stapling_responder_error_cache_time 300s; # Cache time for responder errors location / { proxy_pass http://backend; } } } Check for certificate path validation. If "ssl_verify_client on" is not present in the configuration, this is a finding. Check if a CRL file is configured. If "ssl_crl <file>" is not present in the configuration, this is a finding.
✔️ Fix
If using OCSP for certificate revocation, this requirement is Not Applicable. Determine path to NGINX config file: # nginx -qT | grep "# configuration" # configuration file /etc/nginx/nginx.conf: Note: The default NGINX configuration is "/etc/nginx/nginx.conf", though various files may also be included. # cat <path to config> Configure the following lines in the http { blocks using the example below. Set ssl_verify_client on. Set ssl_crl /etc/nginx/ssl/crl.pem to match the CRL file name. http { server { listen 443 ssl; server_name example.com; ssl_certificate /etc/nginx/ssl/server.crt; ssl_certificate_key /etc/nginx/ssl/server.key; ssl_client_certificate /etc/nginx/ssl/ca.crt; ssl_verify_client on; ssl_crl /etc/nginx/ssl/crl.pem; ssl_ocsp on; ssl_ocsp_responder http://ocsp.disa.mil; ssl_stapling on; ssl_stapling_verify on; ssl_stapling_file /etc/nginx/ssl/ocsp_cache.pem; ssl_stapling_responder_timeout 3s; # Timeout for OCSP responder queries ssl_stapling_responder_error_cache_time 300s; # Cache time for responder errors location / { proxy_pass http://backend; } } }