Add script for reading docker secrets into environment variables

Author: Tamas Pallos

README.md

@@ -1,2 +1,47 @@
 # jore4-tools
+
 Tools which are commonly used by other JORE4 projects
+
+## Tools for Docker
+
+### read-secrets.sh
+
+Reads docker secrets into environment variables. Secrets' filenames are
+transformed into environment variable names with \_ characters replacing
+non-alphanumeric characters.
+
+Parameters:
+
+Reads secrets' bash path from `SECRET_STORE_BASE_PATH` env variable
+
+Example setup:
+
+```
+$ cat secrets/foo1
+bar1
+$ cat secrets/foo2-blabla
+bar2
+$ cat secrets/foo3.lol
+bar3.lolo
+```
+
+Usage:
+
+```
+$ SECRET_STORE_BASE_PATH=secrets source read-secrets.sh
+$ printenv
+[...]
+FOO1=bar1
+FOO2_BLABLA=bar2
+FOO3_LOL=bar3.lolo
+```
+
+Usage within Dockerfile:
+
+```
+# download script for reading docker secrets
+RUN curl -o /tmp/read-secrets.sh "https://raw.githubusercontent.com/HSLdevcom/jore4-tools/main/docker/read-secrets.sh"
+
+# read docker secrets into environment variables and run application
+CMD /bin/bash -c "source /tmp/read-secrets.sh && java -jar /.../xxx.jar"
+```

docker/read-secrets.sh

@@ -0,0 +1,36 @@
+#!/bin/sh
+
+set -eu
+
+# Reads docker secrets into environment variables.
+# Secrets' filenames are transformed into environment variable names with _ characters replacing non-alphanumeric characters.
+#
+# parameters:
+# reads secrets' bash path from SECRET_STORE_BASE_PATH env variable
+#
+# example setup:
+# $ cat secrets/foo1
+# bar1
+# $ cat secrets/foo2-blabla
+# bar2
+# $ cat secrets/foo3.lol
+# bar3.lolo
+#
+# usage:
+# $ SECRET_STORE_BASE_PATH=secrets source read-secrets.sh
+# $ printenv
+# [...]
+# FOO1=bar1
+# FOO2_BLABLA=bar2
+# FOO3_LOL=bar3.lolo
+
+# read docker secrets into environment variables
+SECRET_STORE_BASE_PATH="${SECRET_STORE_BASE_PATH:-/run/secrets}"
+for SECRET_FILENAME in $(ls "$SECRET_STORE_BASE_PATH");
+do
+    # replace non-alphanumeric characters with _ and convert to uppercase
+    VAR_NAME=$(echo $SECRET_FILENAME | sed -E 's/[^a-zA-Z0-9]+/_/g' | tr a-z A-Z)
+    VAR_VALUE=$(cat "$SECRET_STORE_BASE_PATH/$SECRET_FILENAME")
+    export "$VAR_NAME"="$VAR_VALUE"
+    echo "Found secret '$SECRET_FILENAME', exported it as '$VAR_NAME' environment variable."
+done