add AWS credential provider from config file (#1041)

api/src/main/java/io/minio/credentials/AwsConfigProvider.java

@@ -0,0 +1,135 @@
+/*
+ * MinIO Java SDK for Amazon S3 Compatible Cloud Storage, (C) 2020 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
+ *
+ *     https://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 io.minio.credentials;
+
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Paths;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Properties;
+import javax.annotation.Nullable;
+
+/** Credential provider using Amazon AWS credentials file. */
+public class AwsConfigProvider extends EnvironmentProvider {
+  private final String filename;
+  private final String profile;
+
+  public AwsConfigProvider(@Nullable String filename, @Nullable String profile) {
+    if (filename != null && filename.isEmpty()) {
+      throw new IllegalArgumentException("Filename must not be empty");
+    }
+
+    if (profile != null && profile.isEmpty()) {
+      throw new IllegalArgumentException("Profile must not be empty");
+    }
+
+    this.filename = filename;
+    this.profile = profile;
+  }
+
+  /**
+   * Retrieve credentials in provided profile or AWS_PROFILE or "default" section in INI file from
+   * provided filename or AWS_SHARED_CREDENTIALS_FILE environment variable or file .aws/credentials
+   * in user's home directory.
+   */
+  @Override
+  public Credentials fetch() {
+    String filename = this.filename;
+    if (filename == null) {
+      filename = getProperty("AWS_SHARED_CREDENTIALS_FILE");
+    }
+    if (filename == null) {
+      filename = Paths.get(System.getProperty("user.home"), ".aws", "credentials").toString();
+    }
+
+    String profile = this.profile;
+    if (profile == null) {
+      profile = getProperty("AWS_PROFILE");
+    }
+    if (profile == null) {
+      profile = "default";
+    }
+
+    try (InputStream is = new FileInputStream(filename)) {
+      Map<String, Properties> result = unmarshal(new InputStreamReader(is, StandardCharsets.UTF_8));
+      Properties values = result.get(profile);
+      if (values == null) {
+        throw new IllegalStateException(
+            "Profile " + profile + " does not exist in AWS credential file");
+      }
+
+      String accessKey = values.getProperty("aws_access_key_id");
+      String secretKey = values.getProperty("aws_secret_access_key");
+      String sessionToken = values.getProperty("aws_session_token");
+
+      if (accessKey == null) {
+        throw new IllegalStateException(
+            "Access key does not exist in profile " + profile + " in AWS credential file");
+      }
+
+      if (secretKey == null) {
+        throw new IllegalStateException(
+            "Secret key does not exist in profile " + profile + " in AWS credential file");
+      }
+
+      return new Credentials(accessKey, secretKey, sessionToken, null);
+    } catch (IOException e) {
+      throw new IllegalStateException("Unable to read AWS credential file", e);
+    }
+  }
+
+  private Map<String, Properties> unmarshal(Reader reader) throws IOException {
+    return new Ini().unmarshal(reader);
+  }
+
+  private static class Ini {
+    private Map<String, Properties> result = new HashMap<>();
+
+    public Map<String, Properties> unmarshal(Reader reader) throws IOException {
+      new Properties() {
+        private Properties section;
+
+        @Override
+        public Object put(Object key, Object value) {
+          String header = (((String) key) + " " + value).trim();
+          if (header.startsWith("[") && header.endsWith("]")) {
+            section = new Properties();
+            return result.put(header.substring(1, header.length() - 1), section);
+          }
+          return section.put(key, value);
+        }
+
+        @Override
+        public boolean equals(Object o) {
+          return super.equals(o);
+        }
+
+        @Override
+        public int hashCode() {
+          return super.hashCode();
+        }
+      }.load(reader);
+
+      return result;
+    }
+  }
+}

examples/MinioClientWithAwsConfigProvider.java

@@ -0,0 +1,39 @@
+/*
+ * MinIO Java SDK for Amazon S3 Compatible Cloud Storage, (C) 2020 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
+ *
+ *     https://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.
+ */
+
+import io.minio.MinioClient;
+import io.minio.StatObjectArgs;
+import io.minio.StatObjectResponse;
+import io.minio.credentials.AwsConfigProvider;
+import io.minio.credentials.Provider;
+
+public class MinioClientWithAwsConfigProvider {
+  public static void main(String[] args) throws Exception {
+    Provider provider = new AwsConfigProvider(null, null);
+
+    MinioClient minioClient =
+        MinioClient.builder()
+            .endpoint("https://MINIO-HOST:MINIO-PORT")
+            .credentialsProvider(provider)
+            .build();
+
+    // Get information of an object.
+    StatObjectResponse stat =
+        minioClient.statObject(
+            StatObjectArgs.builder().bucket("my-bucketname").object("my-objectname").build());
+    System.out.println(stat);
+  }
+}