Add configuration for mapping access keys

This allows S3Proxy to use multiple local credentials mapping onto
multiple remote credentials.  Credentials properties files have the
form:

local-identity=local-credential:remote-identity:remote-credential

src/main/java/org/gaul/s3proxy/Main.java

@@ -16,6 +16,8 @@
 
 package org.gaul.s3proxy;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
 import java.io.Console;
 import java.io.File;
 import java.io.FileInputStream;
@@ -24,6 +26,7 @@ import java.io.InputStream;
 import java.io.PrintStream;
 import java.net.URI;
 import java.nio.charset.StandardCharsets;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.Properties;
 import java.util.concurrent.Executors;
@@ -31,6 +34,7 @@ import java.util.concurrent.TimeUnit;
 
 import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Maps;
 import com.google.common.io.Files;
 import com.google.inject.Module;
 
@@ -59,6 +63,10 @@ public final class Main {
                 usage = "S3Proxy configuration (required)")
         private File propertiesFile;
 
+        @Option(name = "--credentials-properties",
+                usage = "Mapping for multiple credentials")
+        private File credentialsPropertyFile;
+
         @Option(name = "--version", usage = "display version")
         private boolean version;
     }
@@ -91,6 +99,14 @@ public final class Main {
         }
         properties.putAll(System.getProperties());
 
+        Properties credentialsProperties = new Properties();
+        if (options.credentialsPropertyFile != null) {
+            try (InputStream is = new FileInputStream(
+                    options.credentialsPropertyFile)) {
+                credentialsProperties.load(is);
+            }
+        }
+
         String s3ProxyEndpointString = properties.getProperty(
                 S3ProxyConstants.PROPERTY_ENDPOINT);
         String secureEndpoint = properties.getProperty(
@@ -238,6 +254,33 @@ public final class Main {
             System.exit(1);
             throw e;
         }
+
+        final Map<String, Map.Entry<String, BlobStore>> credentialsMap =
+                new HashMap<>();
+        for (Map.Entry<Object, Object> entry :
+                credentialsProperties.entrySet()) {
+            String key = (String) entry.getKey();
+            String[] values = ((String) entry.getValue()).split(":");
+            checkArgument(values.length == 3, "values must have the form: " +
+                    "frontend_credential:remote_identity:remote_credential");
+
+            Properties newProperties = new Properties(properties);
+            newProperties.setProperty(Constants.PROPERTY_IDENTITY, values[1]);
+            newProperties.setProperty(Constants.PROPERTY_CREDENTIAL, values[2]);
+
+            credentialsMap.put(key, Maps.immutableEntry(values[0],
+                    createBlobStore(newProperties)));
+        }
+        if (!credentialsMap.isEmpty()) {
+            s3Proxy.setBlobStoreLocator(new BlobStoreLocator() {
+                @Override
+                public Map.Entry<String, BlobStore> locateBlobStore(
+                        String identity, String container, String blob) {
+                    return credentialsMap.get(identity);
+                }
+            });
+        }
+
         try {
             s3Proxy.start();
         } catch (Exception e) {

src/test/java/org/gaul/s3proxy/AwsSdkTest.java

@@ -87,10 +87,13 @@ import com.amazonaws.services.s3.model.UploadPartRequest;
 import com.amazonaws.services.s3.model.UploadPartResult;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Maps;
 import com.google.common.io.ByteSource;
 
 import org.assertj.core.api.Fail;
 
+import org.jclouds.ContextBuilder;
+import org.jclouds.blobstore.BlobStore;
 import org.jclouds.blobstore.BlobStoreContext;
 import org.jclouds.rest.HttpClient;
 
@@ -1379,6 +1382,75 @@ public final class AwsSdkTest {
         }
     }
 
+    @Test
+    public void testBlobStoreLocator() throws Exception {
+        final BlobStore blobStore1 = ContextBuilder
+                .newBuilder("transient")
+                .credentials("identity1", "credential1")
+                .build(BlobStoreContext.class)
+                .getBlobStore();
+        blobStore1.createContainerInLocation(null, containerName);
+
+        final BlobStore blobStore2 = ContextBuilder
+                .newBuilder("transient")
+                .credentials("identity2", "credential2")
+                .build(BlobStoreContext.class)
+                .getBlobStore();
+        blobStore2.createContainerInLocation(null, containerName);
+
+        s3Proxy.setBlobStoreLocator(new BlobStoreLocator() {
+            @Override
+            public Map.Entry<String, BlobStore> locateBlobStore(
+                    String identity, String container, String blob) {
+                if (identity.equals("identity1")) {
+                    return Maps.immutableEntry("credential1", blobStore1);
+                } else if (identity.equals("identity2")) {
+                    return Maps.immutableEntry("credential2", blobStore2);
+                } else {
+                    return null;
+                }
+            }
+        });
+
+        client = AmazonS3ClientBuilder.standard()
+                .withClientConfiguration(V2_SIGNER_CONFIG)
+                .withCredentials(new AWSStaticCredentialsProvider(
+                        new BasicAWSCredentials("identity1", "credential1")))
+                .withEndpointConfiguration(s3EndpointConfig).build();
+
+        ObjectMetadata metadata = new ObjectMetadata();
+        metadata.setContentLength(BYTE_SOURCE.size());
+        client.putObject(containerName, "foo",
+                BYTE_SOURCE.openStream(), metadata);
+
+        S3Object object = client.getObject(containerName, "foo");
+        assertThat(object).isNotNull();
+
+        client = AmazonS3ClientBuilder.standard()
+                .withClientConfiguration(V2_SIGNER_CONFIG)
+                .withCredentials(new AWSStaticCredentialsProvider(
+                        new BasicAWSCredentials("identity2", "credential2")))
+                .withEndpointConfiguration(s3EndpointConfig).build();
+
+        try {
+            client.getObject(containerName, "foo");
+        } catch (AmazonS3Exception e) {
+            assertThat(e.getErrorCode()).isEqualTo("NoSuchKey");
+        }
+
+        client = AmazonS3ClientBuilder.standard()
+                .withClientConfiguration(V2_SIGNER_CONFIG)
+                .withCredentials(new AWSStaticCredentialsProvider(
+                        new BasicAWSCredentials("identity3", "credential3")))
+                .withEndpointConfiguration(s3EndpointConfig).build();
+
+        try {
+            client.getObject(containerName, "foo");
+        } catch (AmazonS3Exception e) {
+            assertThat(e.getErrorCode()).isEqualTo("InvalidAccessKeyId");
+        }
+    }
+
     private static final class NullX509TrustManager
             implements X509TrustManager {
         @Override