docker: Support docker swarm secrets. (#3977)

Fixes #3896

buildscripts/docker-entrypoint.sh

@@ -0,0 +1,43 @@
+#!/bin/sh
+#
+# Minio Cloud Storage, (C) 2017 Minio, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+# if command starts with an option, prepend minio
+if [ "${1}" != "minio" ]; then
+    if [ -n "${1}" ]; then
+        set -- minio "$@"
+    fi
+fi
+
+## Look for swarm secrets in default location.
+file_env() {
+    local MINIO_ACCESS_KEY_FILE="/run/secrets/access_key"
+    local MINIO_SECRET_KEY_FILE="/run/secrets/secret_key"
+
+    if [ -f $MINIO_ACCESS_KEY_FILE -a -f $MINIO_SECRET_KEY_FILE ]; then
+        if [ -f $MINIO_ACCESS_KEY_FILE ]; then
+            export MINIO_ACCESS_KEY="$(cat "$MINIO_ACCESS_KEY_FILE")"
+        fi
+        if [ -f $MINIO_SECRET_KEY_FILE ]; then
+            export MINIO_SECRET_KEY="$(cat "$MINIO_SECRET_KEY_FILE")"
+        fi
+    fi
+}
+
+## Set env if necessary.
+file_env
+
+exec "$@"