From 69e55aff83149326d176dabc57462b694c53c78c Mon Sep 17 00:00:00 2001
From: DL6ER <dl6er@dl6er.de>
Date: Wed, 30 Dec 2020 10:50:16 +0100
Subject: [PATCH] Ensure critical config lines have trailing newlines before
 appending new content. This is guaranteed by our scripts, however, it is not
 guaranteed any longer when uders manually edited config files themselves.
 Ensure the files are okay to work with before adding anything to them.

Signed-off-by: DL6ER <dl6er@dl6er.de>
---
 advanced/Scripts/webpage.sh |  8 ++++++++
 pihole                      | 14 ++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/advanced/Scripts/webpage.sh b/advanced/Scripts/webpage.sh
index f26ce11d..7870355e 100755
--- a/advanced/Scripts/webpage.sh
+++ b/advanced/Scripts/webpage.sh
@@ -49,6 +49,7 @@ Options:
 }
 
 add_setting() {
+    ensure_newline "${setupVars}"
     echo "${1}=${2}" >> "${setupVars}"
 }
 
@@ -62,6 +63,7 @@ change_setting() {
 }
 
 addFTLsetting() {
+    ensure_newline "${FTLconf}"
     echo "${1}=${2}" >> "${FTLconf}"
 }
 
@@ -75,6 +77,7 @@ changeFTLsetting() {
 }
 
 add_dnsmasq_setting() {
+    ensure_newline "${dnsmasqconfig}"
     if [[ "${2}" != "" ]]; then
         echo "${1}=${2}" >> "${dnsmasqconfig}"
     else
@@ -146,6 +149,7 @@ SetWebPassword() {
 ProcessDNSSettings() {
     source "${setupVars}"
 
+    ensure_newline "${dnsmasqconfig}"
     delete_dnsmasq_setting "server"
 
     COUNTER=1
@@ -392,6 +396,7 @@ ProcessDHCPSettings() {
     fi
 
     # Write settings to file
+    # We do not need to ensure a newline here as the entire file is re-written
     echo "###############################################################################
 #  DHCP SERVER CONFIG FILE AUTOMATICALLY POPULATED BY PI-HOLE WEB INTERFACE.  #
 #            ANY CHANGES MADE TO THIS FILE WILL BE LOST ON CHANGE             #
@@ -545,6 +550,7 @@ AddDHCPStaticAddress() {
     ip="${args[3]}"
     host="${args[4]}"
 
+    ensure_newline "${dhcpstaticconfig}"
     if [[ "${ip}" == "noip" ]]; then
         # Static host name
         echo "dhcp-host=${mac},${host}" >> "${dhcpstaticconfig}"
@@ -689,6 +695,7 @@ AddCustomDNSAddress() {
 
     ip="${args[2]}"
     host="${args[3]}"
+    ensure_newline "${dnscustomfile}"
 	echo "${ip} ${host}" >> "${dnscustomfile}"
 
     # Restart dnsmasq to load new custom DNS entries
@@ -711,6 +718,7 @@ AddCustomCNAMERecord() {
 
     domain="${args[2]}"
     target="${args[3]}"
+    ensure_newline "${dnscustomcnamefile}"
     echo "cname=${domain},${target}" >> "${dnscustomcnamefile}"
 
     # Restart dnsmasq to load new custom CNAME records
diff --git a/pihole b/pihole
index 2b2b7bc2..48e29e93 100755
--- a/pihole
+++ b/pihole
@@ -20,6 +20,18 @@ PI_HOLE_BIN_DIR="/usr/local/bin"
 readonly colfile="${PI_HOLE_SCRIPT_DIR}/COL_TABLE"
 source "${colfile}"
 
+# Ensure there is a newline at the end of the file passed as argument
+ensure_newline() {
+  # Check if the last line of the passed file is empty, if not, append a newline
+  # to the file to ensure we can append new content safely using echo "" >>
+  # later on
+  [ -n "$(tail -c1 "${1}")" ] && printf '\n' >> "${1}"
+  # There was also the suggestion of using a sed-magic call here, however, this
+  # had the drawback to updating all the file timestamps whenever the sed was
+  # run. This solution only updates the timestamp when actually appending a
+  # newline
+}
+
 webpageFunc() {
   source "${PI_HOLE_SCRIPT_DIR}/webpage.sh"
   main "$@"
@@ -191,6 +203,7 @@ Time:
 
       local str="Pi-hole Disabled"
       sed -i "/BLOCKING_ENABLED=/d" "${setupVars}"
+      ensure_newline "${setupVars}"
       echo "BLOCKING_ENABLED=false" >> "${setupVars}"
     fi
   else
@@ -204,6 +217,7 @@ Time:
     local str="Pi-hole Enabled"
 
     sed -i "/BLOCKING_ENABLED=/d" "${setupVars}"
+    ensure_newline "${setupVars}"
     echo "BLOCKING_ENABLED=true" >> "${setupVars}"
   fi