8320971: Use BufferedInputStream.buf directly when param of implTransferTo() is trusted

Reviewed-by: alanb, bpb

src/java.base/share/classes/java/io/BufferedInputStream.java

@@ -643,9 +643,13 @@ public class BufferedInputStream extends FilterInputStream {
         if (getClass() == BufferedInputStream.class && markpos == -1) {
             int avail = count - pos;
             if (avail > 0) {
+                if (isTrusted(out)) {
+                    out.write(getBufIfOpen(), pos, count);
+                } else {
                     // Prevent poisoning and leaking of buf
                     byte[] buffer = Arrays.copyOfRange(getBufIfOpen(), pos, count);
                     out.write(buffer);
+                }
                 pos = count;
             }
             try {
@@ -658,4 +662,22 @@ public class BufferedInputStream extends FilterInputStream {
         }
     }
 
+    /**
+     * Returns true if this class satisfies the following conditions:
+     * <ul>
+     * <li>does not retain a reference to the {@code byte[]}</li>
+     * <li>does not leak a reference to the {@code byte[]} to non-trusted classes</li>
+     * <li>does not modify the contents of the {@code byte[]}</li>
+     * <li>{@code write()} method does not read the contents outside of the offset/length bounds</li>
+     * </ul>
+     *
+     * @return true if this class is trusted
+     */
+    private static boolean isTrusted(OutputStream os) {
+        var clazz = os.getClass();
+        return clazz == ByteArrayOutputStream.class
+                || clazz == FileOutputStream.class
+                || clazz == PipedOutputStream.class;
+    }
+
 }

test/jdk/java/io/BufferedInputStream/TransferToTrusted.java

@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2023, 2024 Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import java.io.*;
+import java.util.Arrays;
+import java.util.Objects;
+import java.util.Random;
+
+/*
+ * @test
+ * @bug 8320971
+ * @summary Verify BufferedInputStream.buf is used directly by
+ *          BufferedInputStream.implTransferTo() only when its OutputStream
+ *          parameter is trusted
+ * @key randomness
+ * @run main/othervm --add-opens=java.base/java.io=ALL-UNNAMED TransferToTrusted
+ */
+public class TransferToTrusted {
+
+    private static final Random RND = new Random(System.nanoTime());
+
+    private static final class UntrustedOutputStream extends OutputStream {
+
+        UntrustedOutputStream() {
+            super();
+        }
+
+        @Override
+        public void write(byte[] b, int off, int len) {
+            Objects.checkFromIndexSize(off, len, b.length);
+            byte[] tmp = new byte[len];
+            RND.nextBytes(tmp);
+            System.arraycopy(tmp, 0, b, off, len);
+        }
+
+        @Override
+        public void write(int b) throws IOException {
+            write(new byte[]{(byte) b});
+        }
+    }
+
+    public static void main(String[] args) throws Exception {
+        final int length = 128;
+        byte[] buf = new byte[length];
+        RND.nextBytes(buf);
+
+        var outputStreams = new OutputStream[]{
+                new ByteArrayOutputStream(),
+                new FileOutputStream(File.createTempFile(TransferToTrusted.class.getName(), null)),
+                new PipedOutputStream(new PipedInputStream(length)),
+                new UntrustedOutputStream()
+        };
+
+        for (var out : outputStreams) {
+            System.err.println("out: " + out.getClass().getName());
+
+            var bis = new BufferedInputStream(new ByteArrayInputStream(buf.clone()));
+            try (out; bis) {
+                bis.read();//need this to fill the BIS.buf in
+                bis.transferTo(out);
+                var internalBuffer = bis.getClass().getDeclaredField("buf");
+                internalBuffer.setAccessible(true);
+                if (!Arrays.equals(buf, Arrays.copyOf((byte[]) internalBuffer.get(bis), length))) {
+                    throw new RuntimeException("Internal buffer was modified");
+                }
+            }
+        }
+    }
+}