Add a shell library for Tor functions.

These are shared among multiple of our scripts.

config/chroot_local-includes/usr/local/lib/tails-shell-library/tor.sh

+#!/bin/sh
+
+TOR_LOG=/var/log/tor/log
+TOR_DIR=/var/lib/tor
+TOR_DESCRIPTORS=${TOR_DIR}/cached-microdescs
+NEW_TOR_DESCRIPTORS=${TOR_DESCRIPTORS}.new
+
+# FIXME: If we end up using this, let's give root access to Tor's control
+# port instead of relying on sudo.
+tor_control_send() {
+	COOKIE=/var/run/tor/control.authcookie
+	HEXCOOKIE=$(xxd -c 32 -g 0 $COOKIE | cut -d' ' -f2)
+	/bin/echo -ne "AUTHENTICATE ${HEXCOOKIE}\r\n${1}\r\nQUIT\r\n" | \
+	    sudo -u amnesia nc 127.0.0.1 9051
+}
+
+# This function may be dangerous to use. See "Potential Tor bug" below.
+# Only handles GETINFO keys with single-line answers
+tor_control_getinfo() {
+	tor_control_send "GETINFO ${1}" | grep -m 1 "^250-${1}=" | \
+	    # Note: we have to remove trailing CL+RF to not confuse the shell
+	    sed "s|^250-${1}=\(.*\)[[:space:]]\+$|\1|"
+}
+
+tor_control_setconf() {
+	tor_control_send "SETCONF ${1}" >/dev/null
+}
+
+# Potential Tor bug: it seems like using this version makes Tor get
+# stuck at "Bootstrapped 5%" quite often. Is Tor sensitive to opening
+# control ports and/or issuing "getinfo status/bootstrap-phase" during
+# early bootstrap? Because of this we fallback to greping the log.
+#tor_bootstrap_progress() {
+#	tor_control_getinfo status/bootstrap-phase | \
+#	    sed 's/^.* BOOTSTRAP PROGRESS=\([[:digit:]]\+\) .*$/\1/'
+#}
+
+tor_is_working() {
+	[ -e $TOR_DESCRIPTORS ] || [ -e $NEW_TOR_DESCRIPTORS ]
+}