A Nagios plugin to check keystore, fixed version of http://www.davidgouveia.net/2013/07/simple-script-to-check-expiry-dates-on-a-java-keystore-jks-file/

checkCertificate.ps1

########################################################
#
#       Check certificates inside a java keystore
#
########################################################

[CmdletBinding()]
Param(
	[Parameter(Mandatory=$True)]
	[string]$keystore,
		
	[Parameter(Mandatory=$True)]
	[string]$password,
	
	[Parameter(Mandatory=$True)]
	[string]$alias,
	
	[Parameter(Mandatory=$True)]
	[int]$threshold
)

[System.Threading.Thread]::CurrentThread.CurrentCulture = "en-US"

$keytool="keytool.exe"
$certificate = Invoke-Expression "$keytool -list -v -keystore $keystore -storepass $password -alias '$alias'"

foreach($line in $certificate){    
    if($line.Contains("Valid from: ")){        
		$index = $line.IndexOf("until: ")
		$dateAsString = $line.SubString($index + "until: ".length).Replace(" CET","")
		$expirationDate = [datetime]::parseexact($dateAsString,"ddd MMM dd HH:mm:ss yyyy",$null)
		break
    }
}

$now = ([System.DateTime]::Now)
$daysToExpire = [int]($expirationDate - $now).TotalDays

if ($threshold -lt $daysToExpire) {
	Write-Host "[OK] Certificate '$alias' expires in '$expirationDate' ($daysToExpire day(s) remaining)."
	exit 0
} elseif ($daysToExpire -lt 0) {
	Write-Host "[CRITICAL] Certificate $alias has already expired."
    exit 2
} else {
	Write-Host "[WARNING] Certificate '$alias' expires in '$expirationDate' ($daysToExpire day(s) remaining)."
    exit 1
}

checkCertificate.sh

#!/bin/bash
 
########################################################
#
#       Check certificates inside a java keystore
#
#       Inspired by http://www.davidgouveia.net/2013/07/simple-script-to-check-expiry-dates-on-a-java-keystore-jks-file/
#
########################################################
TIMEOUT="timeout -k 10s 5s "
KEYTOOL="$TIMEOUT keytool"
THRESHOLD_IN_DAYS="30"
KEYSTORE=""
PASSWORD=""
ALIAS=""
 
ARGS=`getopt -o "p:k:t:a" -l "password:,keystore:,threshold:,alias:" -n "$0" -- "$@"`
 
usage() {
    echo "Usage: $0 --keystore <keystore> --alias <alias>] [--password <password>] [--threshold <number of days until expiry>]"
    exit
}
  
start() {
    CURRENT=`date +%s`

    THRESHOLD=$(($CURRENT + ($THRESHOLD_IN_DAYS*24*60*60)))
    if [ $THRESHOLD -le $CURRENT ]; then
        echo "[ERROR] Invalid date."
        exit 1
    fi

    $KEYTOOL -list -v -keystore "$KEYSTORE" $PASSWORD 2>&1 > /dev/null
    if [ $? -gt 0 ]; then echo "Error opening the keystore."; exit 1; fi

    EXPIRACY=`$KEYTOOL -list -v -keystore "$KEYSTORE" $PASSWORD -alias "$ALIAS" | grep Valid | head -1`
    UNTIL=`$KEYTOOL -list -v -keystore "$KEYSTORE" $PASSWORD -alias "$ALIAS" | grep Valid | head -1 | perl -ne 'if(/until: (.*?)\n/) { print "$1\n"; }'`
    UNTIL_SECONDS=`date -d "$UNTIL" +%s`
    REMAINING_DAYS=$(( ($UNTIL_SECONDS -  $(date +%s)) / 60 / 60 / 24 ))
    if [ $THRESHOLD -le $UNTIL_SECONDS ]; then
        echo "[OK] Certificate '$ALIAS' expires in '$UNTIL' ($REMAINING_DAYS day(s) remaining)."
        exit 0
    elif [ $REMAINING_DAYS -le 0 ]; then
        echo "[CRITICAL] Certificate $ALIAS has already expired."
        exit 2
    else
        echo "[WARNING] Certificate '$ALIAS' expires in '$UNTIL' ($REMAINING_DAYS day(s) remaining)."
        exit 1
    fi

}
 
eval set -- "$ARGS"
 
while true
do
    case "$1" in
        -p|--password)
            if [ -n "$2" ]; then PASSWORD=" -storepass $2"; else echo "Invalid password"; exit 1; fi
            shift 2;;
        -k|--keystore)
            if [ ! -f "$2" ]; then echo "Keystore not found: $1"; exit 1; else KEYSTORE=$2; fi
            shift 2;;
        -t|--threshold)
            if [[ $2 =~ ^[0-9]+$ ]]; then THRESHOLD_IN_DAYS=$2; else echo "Invalid threshold"; exit 1; fi
            shift 2;;
        -a|--alias)
            if [ -n "$2" ]; then ALIAS=$2; else echo "Entry type not set."; exit 1; fi
            shift 2;;
        --)
            shift
            break;;
    esac
done
 
if [ -n "$KEYSTORE" ] && [ -n "$ALIAS" ]
then
    start
else
    usage
fi

@peop558, notice line 59, the script prepends the argument to the password. I had this same error in my testing, but it was due to linebreak issues. Double-check those and/or update the script arguments yourself to test/verify?