From dd7cfaebf2d503d8aa6df969d166cba8b665b790 Mon Sep 17 00:00:00 2001
From: Alberto Bertogli <albertito@blitiri.com.ar>
Date: Thu, 29 Nov 2018 00:31:48 +0000
Subject: [PATCH] test: Use minidns in the Docker tests

The integration tests depend on having a DNS server that resolves
"localhost", which is unfortunate but currently unavoidable given
glibc's limitations ($HOSTALIASES only works on DNS-level aliases, and
does not do lookups in /etc/hosts).

Even under docker, this makes the tests depend on the DNS server, and
whether it resolves localhost or not.

In order to make the docker tests more hermetic and isolated from the
environment, this patch introduces a docker entrypoint that, within the
container, will launch minidns and override /etc/resolv.conf to use it.

This guarantees that the tests will be able to resolve localhost, and
also avoid accidental reliance on external DNS zones.
---
 test/Dockerfile                | 10 ++++++--
 test/util/docker_entrypoint.sh | 46 ++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 2 deletions(-)
 create mode 100755 test/util/docker_entrypoint.sh

diff --git a/test/Dockerfile b/test/Dockerfile
index 128f05c..a413e87 100644
--- a/test/Dockerfile
+++ b/test/Dockerfile
@@ -27,6 +27,9 @@ RUN apt-get install -y -q \
 	gettext-base dovecot-imapd \
 	exim4-daemon-light
 
+# Install sudo, needed for the docker entrypoint.
+RUN apt-get install -y -q sudo
+
 # Prepare exim.
 RUN mkdir -p test/t-02-exim/.exim4 \
 	&& ln -s /usr/sbin/exim4 test/t-02-exim/.exim4
@@ -43,10 +46,13 @@ COPY . .
 # Install chasquid and its dependencies.
 RUN go get -d -v ./... && go install -v ./...
 
+# Custom entry point, which uses our own DNS server.
+ENTRYPOINT ["./test/util/docker_entrypoint.sh"]
+
 # Don't run the tests as root: it makes some integration tests more difficult,
 # as for example Exim has hard-coded protections against running as root.
 RUN useradd -m chasquid && chown -R chasquid:chasquid .
-USER chasquid
+#USER chasquid
 
 # Tests expect the $USER variable set.
-ENV USER chasquid
+#ENV USER chasquid
diff --git a/test/util/docker_entrypoint.sh b/test/util/docker_entrypoint.sh
new file mode 100755
index 0000000..578d895
--- /dev/null
+++ b/test/util/docker_entrypoint.sh
@@ -0,0 +1,46 @@
+#!/bin/bash
+#
+# Script that is used as a Docker entrypoint.
+#
+# It starts minidns with a zone resolving "localhost", and overrides
+# /etc/resolv.conf to use it. Then launches docker CMD.
+#
+# This is used for more hermetic Docker test environments.
+
+set -e
+. $(dirname ${0})/../util/lib.sh
+
+init
+
+# Go to the root of the repository.
+cd ../..
+
+# Undo the EXIT trap, so minidns continues to run in the background.
+trap - EXIT
+
+set -v
+
+go build -o /tmp/minidns "${UTILDIR}/minidns.go"
+
+# The DNS server resolves only "localhost"; tests will rely on this, as we
+# $HOSTALIASES to point our test hostnames to localhost, so it needs to
+# resolve.
+echo "
+localhost A    127.0.0.1
+localhost AAAA ::1
+" > /tmp/zones
+
+start-stop-daemon --start --background \
+	--exec /tmp/minidns \
+	-- --zones=/tmp/zones
+
+echo "nameserver 127.0.0.1" > /etc/resolv.conf
+echo "nameserver ::1" >> /etc/resolv.conf
+
+# Launch arguments, which come from docker CMD, as "chasquid" user.
+# Running tests as root makes some integration tests more difficult, as for
+# example Exim has hard-coded protections against running as root.
+sudo -u chasquid -g chasquid \
+	--set-home \
+	--preserve-env PATH=${PATH} \
+	-- "$@"