Ensure error logging is enabled and set to the info logging level

MediumLevel 1Automatednginx

Description

The error_log directive configures logging for server errors and operational messages. Unlike access logs, error logs capture diagnostic information about failed requests, upstream connection issues, and configuration errors. The log level determines the verbosity of these messages and should be set to capture sufficient detail (typically notice or info) without overwhelming the storage system. error_log must be defined outside server/location blocks, and no error_log may point to /dev/null or use the crit, alert or emerg level. Evaluated on the merged configuration printed by `nginx -T` (all included files; needs permission to read them). CIS marks this recommendation Manual; the automated check implements its audit procedure.

How it is checked

Audit method: Shell command

shell

out=$(nginx -T 2>/dev/null) || exit 1; printf '%s\n' "$out" | awk '{l=$0; o=""; q=""; for(i=1;i<=length(l);i++){c=substr(l,i,1); if(q!=""){o=o c; if(c==q) q=""; continue} if(c=="\""||c=="\047"){q=c; o=o c; continue} if(c=="#") break; if(c==";"||c=="{"){print o c; o=""; continue} if(c=="}"){if(o~/[^[:space:]]/) print o; print "}"; o=""; continue} o=o c} if(o~/[^[:space:]]/) print o}' | awk 'function a(i,  x){x=$i; sub(/;$/,"",x); gsub(/["\047]/,"",x); return x} function inb(n,  i){for(i=1;i<=sp;i++) if(st[i]==n) return 1; return 0} $1=="error_log" && !inb("server") && !inb("location"){n++; f=a(2); l=a(3); if(f=="/dev/null"||l~/^(crit|alert|emerg)$/) bad=1} $1=="error_log" && (inb("server")||inb("location")) {f=a(2); l=a(3); if(f=="/dev/null"||l~/^(crit|alert|emerg)$/) bad=1} {o=gsub(/\{/,"{"); c=gsub(/\}/,"}"); while(o-->0){sp++; b=$1; sub(/\{.*/,"",b); st[sp]=b} while(c-->0 && sp>0) sp--} END{print (n>0&&!bad)?"compliant":"noncompliant"}'

Expected output: compliant

How it is fixed

Fix method: Guidance or infrastructure patch

Set 'error_log /var/log/nginx/error.log info;' (or notice, per your logging policy) at the top of nginx.conf. Then run nginx -t and reload nginx.

Properties

Operating systems: Any
Tags: nginxlogging
Reference: CIS NGINX Benchmark v3.0.0 - 3.3 Ensure error logging is enabled and set to the info logging level

Check this host

Run this on a machine you are allowed to audit. The scan is read-only.

shell

tmaegis scan --target nginx