Correctly report error when HTTP connection was closed before Content…

…-Length was fulfilled.

Instead of reporting checksum mismatch, the downloader will now report

```
Connection was closed before Content-Length was fulfilled. Bytes read %s but wanted %s
```

when HTTP connection is closed before Content-Length is fulfilled.

Closes bazelbuild#13918.

PiperOrigin-RevId: 395411418

src/main/java/com/google/devtools/build/lib/bazel/repository/downloader/CheckContentLengthInputStream.java

@@ -0,0 +1,83 @@
+// Copyright 2021 The Bazel Authors. All rights reserved.
+//
+// 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.
+package com.google.devtools.build.lib.bazel.repository.downloader;
+
+import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadCompatible;
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * Input stream that guarantees its contents match a size.
+ *
+ * <p>This class is not thread safe, but it is safe to message pass this object between threads.
+ */
+@ThreadCompatible
+public class CheckContentLengthInputStream extends InputStream {
+  private final InputStream delegate;
+  private final long expectedSize;
+  private long actualSize;
+
+  public CheckContentLengthInputStream(InputStream delegate, long expectedSize) {
+    this.delegate = delegate;
+    this.expectedSize = expectedSize;
+  }
+
+  @Override
+  public int read() throws IOException {
+    int result = delegate.read();
+    if (result == -1) {
+      checkContentLength();
+    } else {
+      actualSize += result;
+    }
+    return result;
+  }
+
+  @Override
+  public int read(byte[] buffer, int offset, int length) throws IOException {
+    int amount = delegate.read(buffer, offset, length);
+    if (amount == -1) {
+      checkContentLength();
+    } else {
+      actualSize += amount;
+    }
+    return amount;
+  }
+
+  @Override
+  public int available() throws IOException {
+    return delegate.available();
+  }
+
+  @Override
+  public void close() throws IOException {
+    delegate.close();
+    checkContentLength();
+  }
+
+  private void checkContentLength() throws IOException {
+    if (actualSize < expectedSize) {
+      throw new UnrecoverableHttpException(
+          String.format(
+              "Connection was closed before Content-Length was fulfilled. Bytes read %s but wanted"
+                  + " %s",
+              actualSize, expectedSize));
+    } else if (actualSize > expectedSize) {
+      throw new UnrecoverableHttpException(
+          String.format(
+              "Received more bytes than Content-Length. Bytes read %s but wanted %s",
+              actualSize, expectedSize));
+    }
+  }
+}

src/main/java/com/google/devtools/build/lib/bazel/repository/downloader/HttpStream.java

@@ -87,6 +87,16 @@ HttpStream create(
           stream = retrier;
         }
 
+        try {
+          String contentLength = connection.getHeaderField("Content-Length");
+          if (contentLength != null) {
+            long expectedSize = Long.parseLong(contentLength);
+            stream = new CheckContentLengthInputStream(stream, expectedSize);
+          }
+        } catch (NumberFormatException ignored) {
+          // ignored
+        }
+
         stream = progressInputStreamFactory.create(stream, connection.getURL(), originalUrl);
 
         // Determine if we need to transparently gunzip. See RFC2616 § 3.5 and § 14.11. Please note

src/test/java/com/google/devtools/build/lib/bazel/repository/downloader/HttpStreamTest.java

@@ -18,6 +18,7 @@
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.devtools.build.lib.bazel.repository.downloader.DownloaderTestUtils.makeUrl;
 import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.fail;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyInt;
@@ -205,6 +206,56 @@ public void bigDataWithInvalidChecksum_throwsIOExceptionAfterCreateOnEof() throw
     }
   }
 
+  @Test
+  public void bigDataTruncated_throwsExpectedError() throws Exception {
+    byte[] bigData = new byte[HttpStream.PRECHECK_BYTES + 70001];
+    randoCalrissian.nextBytes(bigData);
+    when(connection.getHeaderField("Content-Length"))
+        .thenReturn(String.valueOf(bigData.length + 1));
+    when(connection.getInputStream()).thenReturn(new ByteArrayInputStream(bigData));
+
+    IOException thrown =
+        assertThrows(
+            IOException.class,
+            () -> {
+              try (HttpStream stream =
+                  streamFactory.create(
+                      connection,
+                      AURL,
+                      makeChecksum(Hashing.sha256().hashBytes(bigData).toString()),
+                      reconnector)) {
+                ByteStreams.exhaust(stream);
+              }
+            });
+
+    assertThat(thrown).hasMessageThat().contains("Content-Length");
+  }
+
+  @Test
+  public void bigDataOverflowed_throwsExpectedError() throws Exception {
+    byte[] bigData = new byte[HttpStream.PRECHECK_BYTES + 70001];
+    randoCalrissian.nextBytes(bigData);
+    when(connection.getHeaderField("Content-Length"))
+        .thenReturn(String.valueOf(bigData.length - 1));
+    when(connection.getInputStream()).thenReturn(new ByteArrayInputStream(bigData));
+
+    IOException thrown =
+        assertThrows(
+            IOException.class,
+            () -> {
+              try (HttpStream stream =
+                  streamFactory.create(
+                      connection,
+                      AURL,
+                      makeChecksum(Hashing.sha256().hashBytes(bigData).toString()),
+                      reconnector)) {
+                ByteStreams.exhaust(stream);
+              }
+            });
+
+    assertThat(thrown).hasMessageThat().contains("Content-Length");
+  }
+
   @Test
   public void httpServerSaidGzippedButNotGzipped_throwsZipExceptionInCreate() throws Exception {
     when(connection.getURL()).thenReturn(AURL);