From 5190aff93210098168ad0a5ad492f93e6c080e21 Mon Sep 17 00:00:00 2001
From: Robert C Jennings <robert.jennings@canonical.com>
Date: Fri, 6 Mar 2020 14:55:50 +0100
Subject: [PATCH] Ensure a binary hook has not changed the temporary
 sources.list

---
 live-build/functions | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/live-build/functions b/live-build/functions
index 65c2bc92..b687a5f7 100644
--- a/live-build/functions
+++ b/live-build/functions
@@ -99,10 +99,19 @@ setup_sourceslist(){
         "${mountpoint}/etc/apt/sources.list"
     sed -i "s#http://security.ubuntu.com/ubuntu#${LB_PARENT_MIRROR_CHROOT}#g" \
         "${mountpoint}/etc/apt/sources.list"
+
+    sha256sum "${mountpoint}/etc/apt/sources.list" > sources.list.sha
 }
 
 recover_sourceslist(){
     # Remove the build environment apt mirror from the image
+
+    # Check that the sources.list has not changed.  If it has changed then the
+    # binary hook has modified the file that will be discarded.  If the build
+    # fails here the binary hook needs to alter sources.list.tmp and regenerate
+    # sources.list.sha
+    sha256sum --check sources.list.sha
+
     mv sources.list.tmp "${mountpoint}/etc/apt/sources.list"
 }