Fix: Install latest version of rust for multi-platform build

Author: bokysan

build-scripts/sasl-build.sh

@@ -1,6 +1,20 @@
 #!/usr/bin/env bash
 set -e
 
+# Build the sasl2 library with the sasl-xoauth2 plugin.
+#
+# The sasl-xoauth2 plugin is a SASL plugin that provides support for XOAUTH2 (OAuth 2.0) authentication.
+#
+# The build is done in /sasl-xoauth2/build.
+#
+# This script clones the sasl-xoauth2 repository, applies patches to:
+# - remove the build of the documentation
+# - fix the path to the python interpreter in the sasl-xoauth2-tool
+# - fix the path to the library when building on Alpine
+#
+# After building and installing the sasl2 library with the sasl-xoauth2 plugin, the
+# postfix-sasl-xoauth2-update-ca-certs script is installed into the /etc/ca-certificates/update.d directory.
+# This script is run by the update-ca-certificates command to update the list of trusted certificates.
 build_sasl2() {
 	git clone --depth 1 --branch ${SASL_XOAUTH2_GIT_REF} ${SASL_XOAUTH2_REPO_URL} /sasl-xoauth2
 	cd /sasl-xoauth2
@@ -27,27 +41,60 @@ build_sasl2() {
 	update-ca-certificates
 }
 
+# Installs rust. Debian bookwork comes with an old version of rust, so we can't use the one from the repository.
+# Rust is needed, though for installation of msal library. On some architectures, we cannot use pre-compiled packages
+# (because they don't exist in the PIP repositories) and "pip install" will fail without rust. Specifically, when
+# compiling cryptographic libraries.
+setup_rust() {
+	curl --proto '=https' --tlsv1.3 https://sh.rustup.rs -sSf | sh -s -- -y --profile minimal
+	export PATH="$HOME/.cargo/bin:$PATH"
+}
+
+# Create a virtual environment and install the msal library for the
+# sasl-xoauth2-tool.
 setup_python_venv() {
 	python3 -m venv /sasl
 	. /sasl/bin/activate
 	pip3 install msal
 }
 
+# Installs the base components into the docker image:
+#
+# 1. sasl2 using the sasl-xoauth2 plugin
+# 2. a python virtual environment with the msal library
+base_install() {
+	setup_rust
+	build_sasl2
+	setup_python_venv
+	rustup self uninstall
+}
+
+
 [ -f /etc/lsb-release ] && . /etc/lsb-release
 [ -f /etc/os-release ] && . /etc/os-release
+
+# Determine the base installation method based on the OS.
+# Alpine Linux has a different package management system than Debian-based systems.
 if [ -f /etc/alpine-release ]; then
-	LIBS="git cmake clang make gcc g++ libc-dev pkgconfig curl-dev jsoncpp-dev cyrus-sasl-dev patch rust cargo libffi-dev python3-dev"
+	# Install necessary libraries
+	LIBS="git cmake clang make gcc g++ libc-dev pkgconfig curl-dev jsoncpp-dev cyrus-sasl-dev patch libffi-dev python3-dev"
 	apk add --upgrade --virtual .build-deps ${LIBS}
-	build_sasl2
-	setup_python_venv
+
+	# Run compilation and installation
+	base_install
+
+	# Cleanup. This is important to ensure that we don't keep unnecessary files laying around and thus increasing the size of the image.
 	apk del .build-deps;
 else
+	# Install necessary libraries
 	apt-get update -y -qq
-	LIBS="git build-essential cmake pkg-config libcurl4-openssl-dev libssl-dev libjsoncpp-dev libsasl2-dev rustc cargo rustfmt python3-dev"
+	LIBS="git build-essential cmake pkg-config libcurl4-openssl-dev libssl-dev libjsoncpp-dev libsasl2-dev python3-dev"
 	apt-get install -y --no-install-recommends ${LIBS}
-	build_sasl2
-	apt-get install -y --no-install-recommends python3-venv
-	setup_python_venv
+
+	# Run compilation and installation
+	base_install
+
+	# Cleanup. This is important to ensure that we don't keep unnecessary files laying around and thus increasing the size of the image.
 	apt-get remove --purge -y ${LIBS} python3-venv
 	apt-get autoremove --yes
 	apt-get clean autoclean