Support _FILE suffixed env vars in Docker entrypoint

distribution/docker/src/docker/bin/docker-entrypoint.sh

@@ -38,6 +38,45 @@ if [[ "$1" != "eswrapper" ]]; then
   fi
 fi
 
+# Allow environment variables to be set by creating a file with the
+# contents, and setting an environment variable with the suffix _FILE to
+# point to it. This can be used to provide secrets to a container, without
+# the values being specified explicitly when running the container.
+for VAR_NAME_FILE in $(env | cut -f1 -d= | grep '_FILE$'); do
+  if [[ -n "$VAR_NAME_FILE" ]]; then
+    VAR_NAME="${VAR_NAME_FILE%_FILE}"
+
+    if [[ -n "${!VAR_NAME}" ]]; then
+      echo "ERROR: Both $VAR_NAME_FILE and $VAR_NAME are set. These are mutually exclusive." >&2
+      exit 1
+    fi
+
+    if [[ ! -e "${!VAR_NAME_FILE}" ]]; then
+      echo "ERROR: File ${!VAR_NAME_FILE} from $VAR_NAME_FILE does not exist" >&2
+      exit 1
+    fi
+
+    if [[ ! -r "${!VAR_NAME_FILE}" ]]; then
+      echo "ERROR: File ${!VAR_NAME_FILE} from $VAR_NAME_FILE is not readable" >&2
+      exit 1
+    fi
+
+    FILE_PERMS="$(stat -c '%a' ${!VAR_NAME_FILE})"
+
+    if [[ "$FILE_PERMS" != "400" && "$FILE_PERMS" != 600 ]]; then
+        echo "ERROR: File ${!VAR_NAME_FILE} from $VAR_NAME_FILE must have file permissions 400 or 600" >&2
+        exit 1
+    fi
+
+    echo "Setting $VAR_NAME from $VAR_NAME_FILE at ${!VAR_NAME_FILE}" >&2
+    export "$VAR_NAME"="$(cat ${!VAR_NAME_FILE})"
+
+    unset VAR_NAME
+    # Unset the suffixed environment variable
+    unset "$VAR_NAME_FILE"
+  fi
+done
+
 # Parse Docker env vars to customize Elasticsearch
 #
 # e.g. Setting the env var cluster.name=testcluster

qa/os/src/test/java/org/elasticsearch/packaging/test/DockerTests.java

@@ -40,18 +40,21 @@
 import static org.elasticsearch.packaging.util.Docker.existsInContainer;
 import static org.elasticsearch.packaging.util.Docker.removeContainer;
 import static org.elasticsearch.packaging.util.Docker.runContainer;
+import static org.elasticsearch.packaging.util.Docker.runContainerExpectingFailure;
 import static org.elasticsearch.packaging.util.Docker.verifyContainerInstallation;
+import static org.elasticsearch.packaging.util.Docker.waitForElasticsearch;
 import static org.elasticsearch.packaging.util.Docker.waitForPathToExist;
+import static org.elasticsearch.packaging.util.FileMatcher.p600;
 import static org.elasticsearch.packaging.util.FileMatcher.p660;
 import static org.elasticsearch.packaging.util.FileUtils.append;
 import static org.elasticsearch.packaging.util.FileUtils.getTempDir;
 import static org.elasticsearch.packaging.util.FileUtils.mkdir;
 import static org.elasticsearch.packaging.util.FileUtils.rm;
 import static org.elasticsearch.packaging.util.ServerUtils.makeRequest;
-import static org.elasticsearch.packaging.util.ServerUtils.waitForElasticsearch;
 import static org.hamcrest.CoreMatchers.containsString;
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.Matchers.emptyString;
+import static org.hamcrest.Matchers.equalTo;
 import static org.junit.Assume.assumeTrue;
 
 public class DockerTests extends PackagingTestCase {
@@ -71,7 +74,7 @@ public static void cleanup() {
     }
 
     @Before
-    public void setupTest() throws Exception {
+    public void setupTest() {
         sh = new DockerShell();
         installation = runContainer(distribution());
     }
@@ -153,20 +156,15 @@ public void test70BindMountCustomPathConfAndJvmOptions() throws Exception {
             // we have to disable Log4j from using JMX lest it will hit a security
             // manager exception before we have configured logging; this will fail
             // startup since we detect usages of logging before it is configured
-            final String jvmOptions =
-                "-Xms512m\n" +
-                "-Xmx512m\n" +
-                "-Dlog4j2.disable.jmx=true\n";
+            final String jvmOptions = "-Xms512m\n-Xmx512m\n-Dlog4j2.disable.jmx=true\n";
             append(tempConf.resolve("jvm.options"), jvmOptions);
 
             // Make the temp directory and contents accessible when bind-mounted
             Files.setPosixFilePermissions(tempConf, fromString("rwxrwxrwx"));
 
             // Restart the container
-            removeContainer();
-            runContainer(distribution(), tempConf, Map.of(
-                "ES_JAVA_OPTS", "-XX:-UseCompressedOops"
-            ));
+            final Map<Path, Path> volumes = Map.of(tempConf, Path.of("/usr/share/elasticsearch/config"));
+            runContainer(distribution(), volumes, Map.of("ES_JAVA_OPTS", "-XX:-UseCompressedOops"));
 
             waitForElasticsearch(installation);
 
@@ -178,6 +176,122 @@ public void test70BindMountCustomPathConfAndJvmOptions() throws Exception {
         }
     }
 
+    /**
+     * Check that environment variables can be populated by setting variables with the suffix "_FILE",
+     * which point to files that hold the required values.
+     */
+    public void test80SetEnvironmentVariablesUsingFiles() throws Exception {
+        final Path secretsDir = getTempDir().resolve("secrets");
+        final String optionsFilename = "esJavaOpts.txt";
+
+        try {
+            mkdir(secretsDir);
+
+            // ES_JAVA_OPTS_FILE
+            Files.writeString(secretsDir.resolve(optionsFilename), "-XX:-UseCompressedOops\n");
+
+            Map<String, String> envVars = Map.of("ES_JAVA_OPTS_FILE", "/run/secrets/" + optionsFilename);
+
+            // File permissions need to be secured in order for the ES wrapper to accept
+            // them for populating env var values
+            Files.setPosixFilePermissions(secretsDir.resolve(optionsFilename), p600);
+
+            final Map<Path, Path> volumes = Map.of(secretsDir, Path.of("/run/secrets"));
+
+            // Restart the container
+            runContainer(distribution(), volumes, envVars);
+
+            waitForElasticsearch(installation);
+
+            final String nodesResponse = makeRequest(Request.Get("http://localhost:9200/_nodes"));
+
+            assertThat(nodesResponse, containsString("\"using_compressed_ordinary_object_pointers\":\"false\""));
+        } finally {
+            rm(secretsDir);
+        }
+    }
+
+    /**
+     * Check that the elastic user's password can be configured via a file and the ELASTIC_PASSWORD_FILE environment variable.
+     */
+    public void test81ConfigurePasswordThroughEnvironmentVariableFile() throws Exception {
+        // Test relies on configuring security
+        assumeTrue(distribution.isDefault());
+
+        final String xpackPassword = "hunter2";
+        final Path secretsDir = getTempDir().resolve("secrets");
+        final String passwordFilename = "password.txt";
+
+        try {
+            mkdir(secretsDir);
+
+            // ELASTIC_PASSWORD_FILE
+            Files.writeString(secretsDir.resolve(passwordFilename), xpackPassword + "\n");
+
+            Map<String, String> envVars = Map
+                .of(
+                    "ELASTIC_PASSWORD_FILE",
+                    "/run/secrets/" + passwordFilename,
+                    // Enable security so that we can test that the password has been used
+                    "xpack.security.enabled",
+                    "true"
+                );
+
+            // File permissions need to be secured in order for the ES wrapper to accept
+            // them for populating env var values
+            Files.setPosixFilePermissions(secretsDir.resolve(passwordFilename), p600);
+
+            final Map<Path, Path> volumes = Map.of(secretsDir, Path.of("/run/secrets"));
+
+            // Restart the container
+            runContainer(distribution(), volumes, envVars);
+
+            // If we configured security correctly, then this call will only work if we specify the correct credentials.
+            waitForElasticsearch("green", null, installation, "elastic", "hunter2");
+
+            // Also check that an unauthenticated call fails
+            final int statusCode = Request.Get("http://localhost:9200/_nodes").execute().returnResponse().getStatusLine().getStatusCode();
+            assertThat("Expected server to require authentication", statusCode, equalTo(401));
+        } finally {
+            rm(secretsDir);
+        }
+    }
+
+    /**
+     * Check that when populating environment variables by setting variables with the suffix "_FILE",
+     * the files' permissions are checked.
+     */
+    public void test81EnvironmentVariablesUsingFilesHaveCorrectPermissions() throws Exception {
+        final Path secretsDir = getTempDir().resolve("secrets");
+        final String optionsFilename = "esJavaOpts.txt";
+
+        try {
+            mkdir(secretsDir);
+
+            // ES_JAVA_OPTS_FILE
+            Files.writeString(secretsDir.resolve(optionsFilename), "-XX:-UseCompressedOops\n");
+
+            Map<String, String> envVars = Map.of("ES_JAVA_OPTS_FILE", "/run/secrets/" + optionsFilename);
+
+            // Set invalid file permissions
+            Files.setPosixFilePermissions(secretsDir.resolve(optionsFilename), p660);
+
+            final Map<Path, Path> volumes = Map.of(secretsDir, Path.of("/run/secrets"));
+
+            // Restart the container
+            final Result dockerLogs = runContainerExpectingFailure(distribution(), volumes, envVars);
+
+            assertThat(
+                dockerLogs.stderr,
+                containsString(
+                    "ERROR: File /run/secrets/" + optionsFilename + " from ES_JAVA_OPTS_FILE must have file permissions 400 or 600"
+                )
+            );
+        } finally {
+            rm(secretsDir);
+        }
+    }
+
     /**
      * Check whether the elasticsearch-certutil tool has been shipped correctly,
      * and if present then it can execute.
@@ -219,7 +333,6 @@ public void test92ElasticsearchNodeCliPackaging() {
         final Installation.Executables bin = installation.executables();
 
         final Result result = sh.run(bin.elasticsearchNode + " -h");
-        assertThat(result.stdout,
-            containsString("A CLI tool to do unsafe cluster and index manipulations on current node"));
+        assertThat(result.stdout, containsString("A CLI tool to do unsafe cluster and index manipulations on current node"));
     }
 }