Do some hostname validity checking

diff --git a/dsa-nagios-checks/checks/dsa-check-log-age-loghost b/dsa-nagios-checks/checks/dsa-check-log-age-loghost
index 256caef..391f330 100755 (executable)
--- a/dsa-nagios-checks/checks/dsa-check-log-age-loghost
+++ b/dsa-nagios-checks/checks/dsa-check-log-age-loghost
@@ -29,10 +29,15 @@ usage(){
 
 host="$1"
 if [ -z "$host" ] || [ "$host" = "-h" ] ||  [ "$host" = "--help" ]; then
-       echo >&2 "$0: Usage: $0 <host>"
+       echo >&2 "Usage: $0 <host>"
        usage 3
 fi
 
+if [ "${host/[^a-z0-9]/}" != "$host" ]; then
+       echo >&2 "$0: Invalid hostname $1"
+       exit 3
+fi
+
 ts=$(date -d 'now' +'%Y/%m/%d')
 file="/var/log/hosts/$host/$ts/syslog"
 if [ ! -e "$file" ]; then