Simple HTTP Server in shell command language

httpd.sh

#!/bin/sh
# This is free and unencumbered software released into the public domain.

if (file &> /dev/null; test $? -eq 127); then
	file () {
		# file -Lbi file
		local l_mime
		case "$(echo "$2" | rev | cut -d . -f1 | rev)" in
			html) l_mime=text/html;;
			css) l_mime=text/css;;
			js) l_mime=application/javascript;;
			txt) l_mime=text/plain;;
			c) l_mime=text/plain;;
			h) l_mime=text/plain;;
			sh) l_mime=text/plain;;
			py) l_mime=text/plain;;
			conf) l_mime=text/plain;;
			*) l_mime=application/octet-stream;;
		esac
		echo "$l_mime"
	}
fi

procopts () {
	local l_opt
	eval "$(showdefconf)"
	while getopts 'idvb:p:r:s:c:g' l_opt
	do
		case $l_opt in
			i)HTTPD_INETD=1;;
			d)HTTPD_DAEMONIZE=1;;
			v)HTTPD_VERBOSE=1;;
			b)HTTPD_IP="$OPTARG";;
			p)HTTPD_PORT="$OPTARG";;
			r)HTTPD_ROOT="$OPTARG";;
			s)HTTPD_CGIREGEX="$OPTARG";;
			c)source "$OPTARG" || return 1;;
			g)showdefconf; exit 0;;
			?)return 1;;
		esac
	done
	return 0
}

showhelp () {
	printf 'Usage: httpd\n'
	printf 'Simple HTTP server\n'
	printf '\n'
	printf '\t-i       Inetd mode\n'
	printf '\t-d       Fork into background and log to syslog\n'
	printf '\t-v       Verbose\n'
	printf '\t-b IP    Bind to IP (default ::)\n'
	printf '\t-p PORT  Bind to PORT (default 8080)\n'
	printf '\t-r ROOT  Set webroot to ROOT (default .)\n'
	printf '\t-s REGEX CGI path regex\n'
	printf '\t-c FILE  Configuration file\n'
	printf '\t-g       Print default configuration file to stdout\n'
}

showdefconf () {
	cut -b2- << EOF
	# Configuration for httpd.sh
	# The built-in default conf is sourced before parsing options.
	# If you used -c option, the conf file would be sourced when processing
	# that option, and may override options given before it.

	# Inetd mode
	HTTPD_INETD=0

	# Daemonize
	HTTPD_DAEMONIZE=0

	# Verbose logging (include debug)
	HTTPD_VERBOSE=0

	# bind address
	HTTPD_IP='::'
	# bind port
	HTTPD_PORT='8080'
	# webroot
	HTTPD_ROOT='.'

	# Rewrite sanitized path using sed script
	# Setting it to empty string disables this function
	HTTPD_REWRITE=''

	# HTTP Basic authentication
	# Setting it to empty string disables this function
	HTTPD_BASIC_AUTH=''
	# Example for user 'user' and password 'passw0rd'
	# HTTPD_BASIC_AUTH='dXNlcjpwYXNzdzByZA=='

	# CGI regex
	# requests matching this regex would be passed to CGI
	# Setting it to empty string disables this function
	HTTPD_CGIREGEX=''

	# CGI header blacklist regex
	# HTTP headers matching this regex would be passed in variables with
	# HTTP_BLACKLISTED_ prefix
	HTTPD_CGI_HEADER_BLACKLIST='^PROXY$'
	# 'Proxy' header would be passed in HTTP_BLACKLISTED_PROXY
EOF
}

log () {
	local l_loglvl="$1"
	local l_logfmt="$2"
	shift 2
	local l_logmsg="$(printf "$l_logfmt" "$@")"
	if [ $HTTPD_DAEMONIZE -eq 0 ]; then
		printf '[' 1>&2
		tput bold 1>&2
		printf "$l_loglvl" 1>&2
		tput sgr0 1>&2
		printf ']' 1>&2
		echo "$l_logmsg" 1>&2
	else
		logger "$l_loglvl: $l_logmsg"
	fi
}

log_error () {
	log ERROR "$@"
}

log_info () {
	log INFO "$@"
}

log_debug () {
	if [ $HTTPD_VERBOSE -eq 0 ]; then
		return 0
	fi
	log DEBUG "$@"
}

toupper () {
	tr '[[:lower:]]' '[[:upper:]]'
}

shquote () {
	printf "'$(echo "$1" | sed 's/'\''/\\'\''/g')'"
}

urlsanitize () {
	local l_url="$1"
	local l_url="$(printf "$(echo "$l_url" | sed 's/@/\\x/g')")"
	while echo "$l_url" | grep '//' &> /dev/null; do
		l_nurl=$(echo "$l_url" | sed 's@//@/@g;')
		if [ "$l_url" = "$l_nurl" ]; then
			return 1
		fi
		l_url="$l_nurl"
	done
	while echo "$l_url" | grep '/\.\./' &> /dev/null; do
		l_nurl=$(echo "$l_url" | sed 's@/[^/]*/\.\.\(/\)@\1@g')
		if [ "$l_url" = "$l_nurl" ]; then
			return 1
		fi
		l_url="$l_nurl"
	done
	echo "$l_url"
	log_debug 'Sanitize URL "%s" -> "%s"' "$1" "$l_url"
	return 0
}

httphandler () {
	log_debug 'Entering HTTP handler'
	local l_start
	read -r l_start
	log_debug 'Got start line %s' "$(shquote "$l_start")"
	# 'national' in URL not supported
	echo "$l_start" | grep -E '^[A-Z]+ /(([-a-zA-Z0-9$_.!*'\''(),:@&=+]|%[0-9a-fA-F]{2})+(/([-a-zA-Z0-9$_.!*'\''(),:@&=+]|%[0-9a-fA-F]{2})*)*)?(;([-a-zA-Z0-9$_.!*'\''(),:@&=+/]|%[0-9a-fA-F]{2})*)*(\?([-a-zA-Z0-9$_.!*'\''(),;/?:@&=+]|%[0-9a-fA-F]{2})*)? HTTP/[0-9]+.[0-9]+'$'\r''$' &> /dev/null
	if [ $? -ne 0 ]; then
		# Invalid request
		printf 'HTTP/1.0 400 Bad Request\r\n\r\n'
		return
	fi
	log_debug 'Valid start line'
	REQUEST_METHOD="$(echo "$l_start" | cut -d' ' -f1 | toupper)"
	export REQUEST_METHOD
	log_debug 'Got method %s' "$REQUEST_METHOD"
	REQUEST_URI="$(echo "$l_start" | cut -d' ' -f2)"
	export REQUEST_URI
	log_debug 'Got URI %s' "$REQUEST_URI"
	QUERY_STRING="$(echo "$REQUEST_URI" | cut -d'?' -f2-)"
	export QUERY_STRING
	log_debug 'Got QS %s' "$QUERY_STRING"
	local l_path
	l_path="$(urlsanitize "$(echo "$REQUEST_URI" | cut -d'?' -f1)")"
	if [ $? -ne 0 ]; then
		# urlsanitize failed, rejecting
		printf 'HTTP/1.0 403 Forbidden\r\n\r\n'
		return
	fi
	if [ -n "$HTTPD_REWRITE" ]; then
		l_path="$(echo "$l_path" | sed "$HTTPD_REWRITE")"
		log_debug 'URL rewritten to "%s"' "$l_path"
	fi
	local l_head
	read -r l_head
	while [ "$l_head" != $'\r' ]
	do
		local l_hn="$(echo "$l_head" | cut -d: -f1 | toupper | sed 's/[^A-Z0-9]/_/g')"
		local l_hv="$(echo "$l_head" | cut -d: -f2- | cut -b2- | rev | cut -b2- | rev)"
		log_debug 'Got head line <%s>: <%s>' "$l_hn" "$l_hv"
		local l_prefix="HTTP_"
		if (echo "$l_hn" | grep "$HTTPD_CGI_HEADER_BLACKLIST" &> /dev/null); then
			l_prefix="HTTP_BLACKLISTED_"
		fi
		eval "${l_prefix}${l_hn}=$(shquote "$l_hv"); export ${l_prefix}${l_hn}"
		read -r l_head
	done
	if [ -n "$HTTPD_BASIC_AUTH" ] && [ "$HTTP_AUTHORIZATION" != "Basic $HTTPD_BASIC_AUTH" ]; then
			# auth fail
			printf 'HTTP/1.0 401 Authorization required\r\n\r\n'
			return
	fi
	local l_httpresp
	if [ -n "$HTTPD_CGIREGEX" ] && (echo "$l_path" | grep "$HTTPD_CGIREGEX" &> /dev/null); then
		log_debug 'Pass to CGI %s' "$HTTPD_ROOT$l_path"
		callcgi "$HTTPD_ROOT$l_path"
	else
		log_debug 'Pass to default handler'
		httpd_defhandler "$l_path"
	fi
	log_info '%s - - [%s] "%s" %d -' '-' "$(date '+%d/%b/%Y:%H:%M:%S %z')" "$(echo "$l_start" | rev | cut -b2- | rev)" "$l_httpresp"
}

httpcode2msg () {
	case "$1" in
		200) echo OK;;
		206) echo Partial Content;;
		302) echo Found;;
		400) echo Bad Requets;;
		401) echo Authorization Required;;
		403) echo Forbidden;;
		404) echo Not Found;;
		500) echo Internal Server Error;;
	esac
}

callcgi () {
	log_debug 'calling cgi'
	local l_cgi="$1"
	local l_ret
	l_ret="$("$l_cgi")"
	if [ $? -ne 0 ]; then
		log_debug 'cgi failed'
		printf 'HTTP/1.0 500 Internal Server Error\r\n\r\n'
		l_httpresp=500
		return
	fi
	log_debug 'cgi succeed'
	if (echo "$l_ret" | head -n1 | grep '^Status:' &> /dev/null); then
		log_debug 'cgi supplied status code'
		local l_stat=$(echo "$l_ret" | head -n1 | sed 's@^Status: \([0-9]\+\).*$@\1@')
		printf 'HTTP/1.0 %d %s\r\n' "$l_stat" "$(httpcode2msg "$l_stat")"
		log_debug 'outputting remaining content'
		echo "$l_ret" | tail -n+2
		l_httpresp="$l_stat"
		return
	else
		log_debug 'use status code 200'
		printf 'HTTP/1.0 200 OK\r\n\r\n'
		echo "$l_ret"
		l_httpresp="$l_stat"
		return
	fi
}

httpd_defhandler () {
	local l_tgtpath="$HTTPD_ROOT$1"
	log_debug 'defhandler: path "%s"' "$l_tgtpath"
	if [ ! -e "$l_tgtpath" ]; then
		printf 'HTTP/1.0 404 Not Found\r\n\r\n'
		l_httpresp=404
		return
	fi
	if [ -d "$l_tgtpath" ]; then
		if [ "$(echo "$l_tgtpath" | rev | cut -b1)" != '/' ]; then
			printf "HTTP/1.0 302 Found\r\nLocation: $1/\r\n\r\n"
			l_httpresp=302
			return
		fi
		# listing
		cd "$l_tgtpath"
		local l_listing="<html><body>$(ls | (while read l_f; do
			printf '<p><a href="%s">%s</a></p>' "$l_f" "$l_f"
		done))</body></html>"
		printf 'HTTP/1.0 200 Forbidden\r\nContent-Type: text/html\r\nContent-Length: %d\r\n\r\n%s' $(expr $(echo "$l_listing" | wc -c) - 1) "$l_listing"
		l_httpresp=200
		return
	fi
	if [ -f "$l_tgtpath" ]; then
		printf "HTTP/1.0 200 OK\r\nContent-Type: $(file -Lbi "$l_tgtpath" | cut -d';' -f1)\r\nContent-Length: $(ls -Ll "$l_tgtpath" | awk '{ print $5 }')\r\n\r\n"
		cat "$l_tgtpath"
		l_httpresp=200
		return
	fi
	printf 'HTTP/1.0 403 Forbidden\r\n\r\n'
	l_httpresp=403
	return
}

mkcmdline () {
	local l_cmdline
	for a in "$@"
	do
		if [ -n "$l_cmdline" ]; then
			l_cmdline="$l_cmdline $(shquote "$a")"
		else
			l_cmdline="$(shquote "$a")"
		fi
	done
	echo "$l_cmdline"
}

probeserver () {
	# runserver <ip> <port> <prog> [<args> ...]
	if (nc &> /dev/null; test $? -ne 127); then
		log_debug 'found nc'
		if (nc --help 2>&1 | head -n1 | grep 'nmap' &> /dev/null); then
			# nmap ncat
			runserver () {
				log_info 'Starting server using nmap ncat'
				local l_ip="$1"
				local l_port="$2"
				shift 2
				nc -lk "$l_ip" "$l_port" -c "$(mkcmdline "$@")"
			}
			return 0
		elif (nc --help 2>&1 | head -n1 | grep 'BusyBox' &> /dev/null); then
			# busybox nc
			runserver () {
				log_info 'Starting server using busybox nc'
				local l_ip="$1"
				local l_port="$2"
				shift 2
				nc -s "$l_ip" -lkp "$l_port" -e "$@"
			}
			return 0
		elif (nc < /dev/null 2>&1 | grep '^Cmd line' &> /dev/null); then
			# gnu netcat
			runserver () {
				log_info 'Starting server using gnu netcat'
				local l_ip="$1"
				local l_port="$2"
				shift 2
				nc -s "$l_ip" -lkp "$l_port" -c "$(mkcmdline "$@")"
			}
			return 0
		fi
		log_debug 'unsupported nc'
	fi
	if (busybox nc &> /dev/null; test $? -ne 127); then
		log_debug 'found busybox nc'
		# busybox nc
		runserver () {
			log_info 'Starting server using busybox nc'
			local l_ip="$1"
			local l_port="$2"
			shift 2
			busybox nc -s "$l_ip" -lkp "$l_port" -e "$@"
		}
		return 0
	fi
	if (tcpsvd &> /dev/null; test $? -ne 127); then
		log_debug 'found tcpsvd'
		# tcpsvd cannot parse ipv6 addresses
		runserver () {
			log_info 'Starting server using tcpsvd'
			tcpsvd "$@"
		}
		return 0
	fi
	return 1
}

main () {
	local l_progname="$1"
	shift
	procopts "$@"
	if [ $? -ne 0 ]; then
		showhelp
		exit 1
	fi
	log_debug 'procopts end'
	if [ $HTTPD_INETD -ne 0 ]; then
		httphandler
		exit 0
	fi
	probeserver
	if [ $? -ne 0 ]; then
		log_error 'No suitable server found'
		exit 1
	fi
	if [ "$HTTPD_DAEMONIZE" -ne 0 ]; then
		log_info 'Running server in background'
		runserver "$HTTPD_IP" "$HTTPD_PORT" "$l_progname" "$@" -i &
		disown
	else
		runserver "$HTTPD_IP" "$HTTPD_PORT" "$l_progname" "$@" -i
	fi
}

main "$0" "$@"
exit $?

Features:

• Directory listing
• CGI support (not fully compatible)

Dependencies:

• POSIX-compliant shell and utilities
• One of
  • Nmap Ncat
  • Busybox nc
  • GNU netcat
  • tcpsvd
  • inetd (inetd mode only)