#3298 - SSL monitoring script for icinga

check_ssl_cert.sh

+#!/bin/sh
+
+# Icinga plugin that checks how many days are left
+# until SSL certificate expires.
+# Usage:
+# $PLUGIN_DIR/check_ssl_cert.sh -H $HOST -P $PORT -c $CRITICAL -w $WARNING
+
+get_ssl_expiry_date() {
+  openssl s_client -connect "$1:$2" </dev/null 2>/dev/null \
+  | openssl x509 -noout -enddate 2>/dev/null
+}
+
+CURRENT_DATE=`date +%y%m%d`
+HOST="$2"
+PORT="$4"
+CRITICAL="$6"
+WARNING="$8"
+STATE_OK=0
+STATE_WARNING=1
+STATE_CRITICAL=2
+STATE_UNKNOWN=3
+OUTPUT=`get_ssl_expiry_date "$HOST" "$PORT"`
+
+if [ -z "$OUTPUT" ]
+then
+  echo "UNKNOWN - Could not connect to $HOST via port $PORT"
+  exit "$STATE_UNKNOWN"
+fi
+
+DAY=`echo "$OUTPUT" | awk '{print $2}'`
+MONTH=`echo "$OUTPUT" | awk '{print $1}' | cut -c 10-`
+YEAR=`echo "$OUTPUT" | awk '{print $4}'`
+
+if [ "$DAY" -lt 10 ]
+then
+  DAY="0$DAY"
+fi

[Fred, 2018/07/04 14:24:10]

That should work.
But you could also use awk's printf function instead:
In line 30 do this:
DAY=`echo "$OUTPUT" | awk '{printf "%02d", $2}'`

+
+case "$MONTH" in
+
+  "Jan")
+    MONTH="01"
+    ;;
+  "Feb")
+    MONTH="02"
+    ;;
+  "Mar")
+    MONTH="03"
+    ;;
+  "Apr")
+    MONTH="04"
+    ;;
+  "May")
+    MONTH="05"
+    ;;
+  "Jun")
+    MONTH="06"
+    ;;
+  "Jul")
+    MONTH="07"
+    ;;
+  "Aug")
+    MONTH="08"
+    ;;
+  "Sep")
+    MONTH="09"
+    ;;
+  "Oct")
+    MONTH="10"
+    ;;
+  "Nov")
+    MONTH="11"
+    ;;
+  "Dec")
+    MONTH="12"
+    ;;
+  "*")
+    echo "An error occured"
+    exit 1
+    ;;
+esac
+
+EXPIRY_DATE_IN_SEC=`date -d "${YEAR}${MONTH}${DAY}" +%s`
+CURRENT_DATE_IN_SEC=`date -d "$CURRENT_DATE" +%s`
+DIFFERENCE=`expr \( "$EXPIRY_DATE_IN_SEC" - "$CURRENT_DATE_IN_SEC" \) / 86400`
+
+if [ "$DIFFERENCE" -le "$CRITICAL" ]
+then
+  echo "CRITICAL - $HOST: SSL certificate has been expired!"
+  exit "$STATE_CRITICAL"
+elif [ "$DIFFERENCE" -le "$WARNING" ]
+then
+  echo "WARNING - $HOST: SSL certificate will be expired in $DIFFERENCE days!"
+  exit "$STATE_WARNING"
+elif [ "$DIFFERENCE" -gt "$WARNING" ]
+then
+  echo "OK - $HOST: SSL certificate will be expired in $DIFFERENCE days"
+  exit "$STATE_OK"
+else
+  echo "UNKNOWN - $HOST: Could not retrieve data"
+  exit "$STATE_UNKNOWN"
+fi