Add .editorconfig file and implement dependency check that can be

invoked from the command line.

.editorconfig

@@ -0,0 +1,5 @@
+root = true
+
+[*.sh]
+indent_size = 4
+indent_style = tab

ddos-mitigator.sh

@@ -42,6 +42,24 @@ MY_IP="94.199.214.20"
 # After this point, no editing is required.
 start=$(date +%s)
 
+# Dependencies of this script. Simple array with the following structure:
+# (command package [...])
+dependencies=(
+"sudo" "app-admin/sudo"
+"python" "dev-lang/python:3.8"
+"fail2ban-client" "net-analyzer/fail2ban"
+"cut" "sys-apps/coreutils"
+"id" "sys-apps/coreutils"
+"sort" "sys-apps/coreutils"
+"touch" "sys-apps/coreutils"
+"tr" "sys-apps/coreutils"
+"uniq" "sys-apps/coreutils"
+"grep" "sys-apps/grep"
+"sponge" "sys-apps/moreutils"
+"netstat" "sys-apps/net_tools"
+"getopt" "sys-apps/util-linux"
+)
+
 # These suffixes must be appended to the respective addresses and subnets.
 suffix8="/8"
 suffix16="/16"
@@ -61,18 +79,40 @@ bold="$(printf '\033[1m')"
 reset="$(printf '\033[0m')"
 
 # Clean up when the script exits.
-trap 'sudo -k; rm -r ${tmpdir}' EXIT
+trap 'sudo -k 2>/dev/null >&2; rm -r ${tmpdir}' EXIT
 
-function check_installed() {
+function is_installed() {
+	which "${1}" 2>/dev/null >&2
+	return $?
+}
+
+function print_missing_dependency() {
 	local command="$1"
 	local package="$2"
-	which "${command}" 2>/dev/null >&2
-	local result=$?
 
-	if [[ "${result}" -ne 0 ]] ; then
-		echo "${red}Command ${bold}${command}${reset}${red} not found.${reset} Please install package ${blue}${package}${reset}."
-		exit 1
-	fi
+	echo "${red}Command ${bold}${command}${reset}${red} not found.${reset} Please install package ${blue}${package}${reset}." >&2
+}
+
+function check_dependencies() {
+	local arraylength=${#dependencies[@]}
+	local res=
+	local command=
+	local package=
+	# 0: true, all installed; 1: false, at least one command/package missing
+	local all_installed=0
+
+	for (( i=0; i<${arraylength}; i+=2 )) ; do
+		command="${dependencies[$i]}"
+		package="${dependencies[$i+1]}"
+		is_installed "${command}" "${package}"
+		res=$?
+		if [[ $res -ne 0 ]] ; then
+			print_missing_dependency "${command}" "${package}"
+			all_installed=1
+		fi
+	done
+
+	return ${all_installed}
 }
 
 function print_help() {
@@ -96,6 +136,12 @@ Usage: $(basename $0) -d FILE [OPTION...]
                                       comma-separated values; defaults to 'CN'
                                       (China).
 
+  -e, --dependencies                  Check if all required dependencies are
+                                      installed. If all dependencies are found,
+                                      exits with code 0. Otherwise, missing
+                                      dependencies are printed to stderr and
+                                      the program terminates with code 1.
+
   -j, --jail=JAIL                     Specify the JAIL to use for banning the IP
                                       addresses.
                                       Defaults to 'apache-auth'.
@@ -152,7 +198,7 @@ function filter() {
 }
 
 function parse_command_line_args() {
-	TEMP=$(getopt -o 'a::,c:,d:,j:,n:,p:,h' -l 'auto::,country:,database:,jail:,netmask:,port:,help' -- "$@")
+	TEMP=$(getopt -o 'a::,c:,d:,e,j:,n:,p:,h' -l 'auto::,country:,database:,dependencies,jail:,netmask:,port:,help' -- "$@")
 
 	if [ $? -ne 0 ] ; then
 		echo 'Error parsing command line options. Terminating. Invoke with --help for help.' >&2
@@ -191,6 +237,10 @@ function parse_command_line_args() {
 				database="$2"
 				shift
 			;;
+			'-e'|'--dependencies')
+				check_dependencies
+				exit $?
+			;;
 			'-j'|'--jail')
 				jail="$2"
 				shift
@@ -408,19 +458,11 @@ port=443
 
 parse_command_line_args "$@"
 
-check_installed "sudo" "app-admin/sudo"
-check_installed "python" "dev-lang/python:3.8"
-check_installed "fail2ban-client" "net-analyzer/fail2ban"
-check_installed "cut" "sys-apps/coreutils"
-check_installed "id" "sys-apps/coreutils"
-check_installed "sort" "sys-apps/coreutils"
-check_installed "touch" "sys-apps/coreutils"
-check_installed "tr" "sys-apps/coreutils"
-check_installed "uniq" "sys-apps/coreutils"
-check_installed "grep" "sys-apps/grep"
-check_installed "sponge" "sys-apps/moreutils"
-check_installed "netstat" "sys-apps/net_tools"
-check_installed "getopt" "sys-apps/util-linux"
+check_dependencies
+dependencies_ok=$?
+if [[ ${dependencies_ok} -ne 0 ]] ; then
+	exit ${dependencies_ok}
+fi
 
 # List already banned addresses in the chosen jail
 banned="$(exec_as_root fail2ban-client get "${jail}" banip)"