File master source (#85)

Fixes #84

src/main/java/org/codehaus/plexus/components/secdispatcher/internal/sources/FileMasterSource.java

@@ -0,0 +1,111 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+package org.codehaus.plexus.components.secdispatcher.internal.sources;
+
+import javax.inject.Named;
+import javax.inject.Singleton;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+import org.codehaus.plexus.components.secdispatcher.MasterSourceMeta;
+import org.codehaus.plexus.components.secdispatcher.SecDispatcher;
+import org.codehaus.plexus.components.secdispatcher.SecDispatcherException;
+
+/**
+ * Password source that uses a plain file with plaintext master password (residing on things like an encrypted pen-drive
+ * or partition). Idea is to "delegate" all the security to that data carrier (for example, it may ask for permission
+ * or password on access to that path). Not recommended to be used on any unprotected data storage or partition.
+ * <p>
+ * Config: {@code file:$fileName}
+ * <p>
+ * The file may start with "#" for human comments, and first non-commented line (trimmed) will be used
+ * as master password.
+ */
+@Singleton
+@Named(FileMasterSource.NAME)
+public final class FileMasterSource extends PrefixMasterSourceSupport implements MasterSourceMeta {
+    public static final String NAME = "file";
+
+    public FileMasterSource() {
+        super(NAME + ":");
+    }
+
+    @Override
+    public String description() {
+        return "File (file name should be edited; use absolute path)";
+    }
+
+    @Override
+    public Optional<String> configTemplate() {
+        return Optional.of(NAME + ":$fileName");
+    }
+
+    @Override
+    protected String doHandle(String transformed) throws SecDispatcherException {
+        String value = readFile(transformed);
+        if (value == null) {
+            throw new SecDispatcherException("File '" + transformed + "' not found or is not readable");
+        }
+        return value;
+    }
+
+    @Override
+    protected SecDispatcher.ValidationResponse doValidateConfiguration(String transformed) {
+        String value = readFile(transformed);
+        if (value == null) {
+            return new SecDispatcher.ValidationResponse(
+                    getClass().getSimpleName(),
+                    true,
+                    Map.of(
+                            SecDispatcher.ValidationResponse.Level.WARNING,
+                            List.of("Configured file does not exist or is not readable")),
+                    List.of());
+        } else {
+            return new SecDispatcher.ValidationResponse(
+                    getClass().getSimpleName(),
+                    true,
+                    Map.of(
+                            SecDispatcher.ValidationResponse.Level.INFO,
+                            List.of("Configured file exist and is readable")),
+                    List.of());
+        }
+    }
+
+    private String readFile(String transformed) throws SecDispatcherException {
+        Path file = Paths.get(transformed);
+        if (file.isAbsolute() && Files.exists(file)) {
+            try {
+                return Files.readAllLines(file).stream()
+                        .filter(l -> !l.startsWith("#"))
+                        .map(String::trim)
+                        .findFirst()
+                        .orElse(null);
+            } catch (IOException e) {
+                throw new SecDispatcherException("Failed to read file '" + transformed + "'", e);
+            }
+        }
+        return null;
+    }
+}