obfsproxy: new package

From the Tor project page:

obfsproxy is a tool that attempts to circumvent censorship, by
transforming the Tor traffic between the client and the bridge. This
way, censors, who usually monitor traffic between the client and the
bridge, will see innocent-looking transformed traffic instead of the
actual Tor traffic.

This depends on:

- pyptlib (#2053)
- twisted (#2052)

Also, txsocksx (#2058) is necessary to use an outgoing SOCKS proxy,
and having either gmpy2 (#2067) or gmpy (#2051) installed will help
speed up calculations.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

net/obfsproxy/files/obfsproxy.conf

@@ -0,0 +1,57 @@
+# To use Obfsproxy with Tor, follow the instructions at:
+#
+# https://www.torproject.org/projects/obfsproxy-instructions.html.en
+#
+# instead of setting up a separate instance of Obfsproxy.
+
+config obfsproxy 'obfsproxy'
+	# Set to 1 to enable this instance
+	option enabled 0
+
+	# One of: managed, dummy, b64, obfs2, obfs3, scramblesuit
+	option transport 'scramblesuit'
+
+	# Shared secret / password
+	# For obfs2 (as the shared secret parameter) and scramblesuit only
+	option password 'EXAMPLEPASSWORDNOTREAL'
+
+	# One of: server, ext_server, client, socks
+	option mode 'socks'
+
+	# Destination address
+	# Required for all modes except 'socks'
+	#option dest_host '0.0.0.0'
+	#option dest_port '80'
+
+	# Extended ORPort authentication cookie file location
+	# Required for 'ext_server' mode
+	#option ext_cookie_file ''
+
+	# Listener address
+	option listen_host '127.0.0.1'
+	option listen_port '8080'
+
+	# Set to log to a file instead of syslog
+	#option log_file '/var/log/obfsproxy.log'
+
+	# Minimum logging severity
+	# One of: error, warning, info, debug
+	#option log_min_severity 'info'
+
+	# Set to 1 to disable logging
+	#option no_log 0
+
+	# Set to 1 to disable safe (scrubbed address) logging
+	#option no_safe_logging 0
+
+	# Run as a different user
+	#option user 'nobody'
+
+	# Outgoing proxy
+	# proxy_scheme is one of: socks4a, socks5, http
+	# txsocksx is required for socks4a or socks5
+	#option proxy_scheme ''
+	#option proxy_username ''
+	#option proxy_password ''
+	#option proxy_host ''
+	#option proxy_port ''

net/obfsproxy/files/obfsproxy.init

@@ -0,0 +1,158 @@
+#!/bin/sh /etc/rc.common
+# Copyright (C) 2016 OpenWrt.org
+
+START=80
+STOP=20
+USE_PROCD=1
+
+PROG=/usr/bin/obfsproxy
+
+append_arg() {
+	local cfg="$1"
+	local var="$2"
+	local opt="$3"
+	local def="$4"
+	local val
+
+	config_get val "$cfg" "$var"
+	[ -n "$val" -o -n "$def" ] && procd_append_param command "$opt" "${val:-$def}"
+}
+
+append_bool() {
+	local cfg="$1"
+	local var="$2"
+	local opt="$3"
+	local def="$4"
+	local val
+
+	config_get_bool val "$cfg" "$var" "$def"
+	[ "$val" = 1 ] && procd_append_param command "$opt"
+}
+
+append_plain() {
+	procd_append_param command "$1"
+}
+
+append_param() {
+	local cfg="$1"
+	local var="$2"
+	local opt="$3"
+	local def="$4"
+	local val
+
+	config_get val "$cfg" "$var"
+	[ -n "$val" -o -n "$def" ] && procd_append_param "$opt" "${val:-$def}"
+}
+
+append_proxy_spec() {
+	local cfg="$1"
+	local scheme_var="$2"
+	local username_var="$3"
+	local password_var="$4"
+	local host_var="$5"
+	local port_var="$6"
+	local opt="$7"
+	local def="$8"
+	local scheme
+	local username
+	local password
+	local host
+	local port
+	local login
+	local val
+
+	config_get scheme "$cfg" "$scheme_var"
+	config_get username "$cfg" "$username_var"
+	config_get password "$cfg" "$password_var"
+	config_get host "$cfg" "$host_var"
+	config_get port "$cfg" "$port_var"
+	[ "$username" ] && login="$username${password:+:$password}@"
+	[ -n "$scheme" -a -n "$host" -a -n "$port" ] && val="$scheme://$login$host:$port"
+	[ -n "$val" -o -n "$def" ] && procd_append_param command "$opt" "${val:-$def}"
+}
+
+append_host_port() {
+	local cfg="$1"
+	local host_var="$2"
+	local port_var="$3"
+	local opt="$4"
+	local def="$5"
+	local host
+	local port
+	local val
+
+	config_get host "$cfg" "$host_var"
+	config_get port "$cfg" "$port_var"
+	[ -n "$host" -a -n "$port" ] && val="$host:$port"
+	[ -n "$val" -o -n "$def" ] && {
+		[ "$opt" ] && procd_append_param command "$opt"
+		procd_append_param command "${val:-$def}"
+	}
+}
+
+start_instance() {
+	local cfg="$1"
+	local lib_dir="/var/lib/obfsproxy/$cfg"
+	local redirect=0
+	local enabled
+	local user
+	local transport
+	local password
+	local log_min_severity
+
+	config_get_bool enabled "$cfg" 'enabled' '0'
+	[ "$enabled" = 0 ] && return 1
+
+	config_get user "$cfg" 'user' 'root'
+	config_get transport "$cfg" 'transport'
+	[ "$transport" = "scramblesuit" ] && config_get password "$cfg" 'password'
+
+	[ -d "$lib_dir" ] || {
+		mkdir -m 0755 -p "$lib_dir/data"
+		chmod -R 0700 "$lib_dir"
+	}
+	[ "$password" ] && {
+		echo "$password" > "$lib_dir/secret"
+		chmod 0600 "$lib_dir/secret"
+	}
+	chown -R "$user:" "$lib_dir"
+
+	config_get log_min_severity "$cfg" 'log_min_severity'
+	[ "$log_min_severity" = "debug" ] && redirect=1
+
+	procd_open_instance
+
+	procd_set_param command "$PROG" --data-dir "$lib_dir/data" --syslog "obfsproxy($cfg)"
+
+	append_arg "$cfg" log_file "--log-file"
+	append_arg "$cfg" log_min_severity "--log-min-severity"
+	append_bool "$cfg" no_log "--no-log"
+	append_bool "$cfg" no_safe_logging "--no-safe-logging"
+	append_proxy_spec "$cfg" proxy_scheme proxy_username proxy_password proxy_host proxy_port "--proxy"
+
+	append_param "$cfg" transport command
+	[ "$transport" = "obfs2" ] && append_arg "$cfg" password "--shared-secret"
+	[ "$password" ] && procd_append_param command "--password-file" "$lib_dir/secret"
+
+	append_param "$cfg" mode command
+	append_host_port "$cfg" dest_host dest_port "--dest"
+	append_arg "$cfg" ext_cookie_file "--ext-cookie-file"
+
+	append_host_port "$cfg" listen_host listen_port
+
+	procd_set_param respawn
+	procd_set_param stdout $redirect
+	procd_set_param stderr $redirect
+	append_param "$cfg" user user
+
+	procd_close_instance
+}
+
+service_triggers() {
+	procd_add_reload_trigger obfsproxy
+}
+
+start_service() {
+	config_load obfsproxy
+	config_foreach start_instance obfsproxy
+}