Java: do not read past the end of the element

java-library/src/main/java/com/sandflow/smpte/mxf/ClipReader.java

@@ -45,6 +45,8 @@ public class ClipReader extends InputStream {
   final AUID elementKey;
   final long elementLength;
   final long essenceOffset;
+  /* size of the key and length of the clip */
+  final long klLength;
   final RandomAccessFileInfo info;
   final RandomAccessInputSource source;
 
@@ -67,6 +69,7 @@ public ClipReader(RandomAccessFileInfo info, RandomAccessInputSource source) thr
     MXFDataInput mis = new MXFDataInput(this.source);
     this.elementKey = mis.readAUID();
     this.elementLength = mis.readBERLength();
+    this.klLength = this.source.position() - clipStartPosition;
 
     /*
      * ECXEPTION: Some versions of ASDCPLib index from the start of the K of the
@@ -78,7 +81,7 @@ public ClipReader(RandomAccessFileInfo info, RandomAccessInputSource source) thr
         && this.info.euToECPosition(0) != 0) {
       this.essenceOffset = 0;
     } else {
-      this.essenceOffset = this.source.position() - clipStartPosition;
+      this.essenceOffset = this.klLength;
     }
 
     this.seek(0);
@@ -131,7 +134,8 @@ public void seek(long euPosition) throws IOException {
     long ecPosition = this.info.euToECPosition(euPosition);
     long filePosition = this.info.ecToFilePositions(ecPosition) + this.essenceOffset;
     this.source.position(filePosition);
-    this.remainingElementBytes = this.elementLength - ecPosition;
+    /* ecPosition + essenceOffset is relative to the start of the K of the clip */
+    this.remainingElementBytes = this.elementLength - (ecPosition + this.essenceOffset - this.klLength);
   }
 
   /**
@@ -163,9 +167,12 @@ public int read() throws IOException {
    */
   @Override
   public int read(byte[] b, int off, int len) throws IOException {
-    if (this.remainingElementBytes == 0)
+    if (len == 0)
+      return 0;
+    if (this.remainingElementBytes <= 0)
       return -1;
-    int r = source.read(b, off, len);
+    /* do not read past the end of the element */
+    int r = source.read(b, off, (int) Math.min(len, this.remainingElementBytes));
     this.remainingElementBytes = r == -1 ? 0 : this.remainingElementBytes - r;
     return r;
   }
@@ -179,9 +186,10 @@ public int read(byte[] b, int off, int len) throws IOException {
    */
   @Override
   public long skip(long n) throws IOException {
-    if (this.remainingElementBytes == 0)
-      return -1;
-    long s = this.source.skip(n);
+    if (n <= 0 || this.remainingElementBytes <= 0)
+      return 0;
+    /* do not skip past the end of the element */
+    long s = Math.max(0, this.source.skip(Math.min(n, this.remainingElementBytes)));
     this.remainingElementBytes = this.remainingElementBytes - s;
     return s;
   }

java-library/src/main/java/com/sandflow/smpte/mxf/GenericStreamReader.java

@@ -143,9 +143,12 @@ public int read() throws IOException {
    */
   @Override
   public int read(byte[] b, int off, int len) throws IOException {
-    if (this.remainingElementBytes == 0)
+    if (len == 0)
+      return 0;
+    if (this.remainingElementBytes <= 0)
       return -1;
-    int r = source.read(b, off, len);
+    /* do not read past the end of the element */
+    int r = source.read(b, off, (int) Math.min(len, this.remainingElementBytes));
     this.remainingElementBytes = r == -1 ? 0 : this.remainingElementBytes - r;
     return r;
   }
@@ -159,9 +162,10 @@ public int read(byte[] b, int off, int len) throws IOException {
    */
   @Override
   public long skip(long n) throws IOException {
-    if (this.remainingElementBytes == 0)
-      return -1;
-    long s = this.source.skip(n);
+    if (n <= 0 || this.remainingElementBytes <= 0)
+      return 0;
+    /* do not skip past the end of the element */
+    long s = Math.max(0, this.source.skip(Math.min(n, this.remainingElementBytes)));
     this.remainingElementBytes = this.remainingElementBytes - s;
     return s;
   }

java-library/src/main/java/com/sandflow/smpte/mxf/StreamingReader.java

@@ -158,9 +158,12 @@ public int read(byte[] b, int off, int len) throws IOException {
     if (this.state != State.IN_PAYLOAD) {
       throw new RuntimeException();
     }
-    if (this.remainingElementBytes == 0)
+    if (len == 0)
+      return 0;
+    if (this.remainingElementBytes <= 0)
       return -1;
-    int r = this.mis.read(b, off, len);
+    /* do not read past the end of the element */
+    int r = this.mis.read(b, off, (int) Math.min(len, this.remainingElementBytes));
     this.remainingElementBytes = r == -1 ? 0 : this.remainingElementBytes - r;
     return r;
   }
@@ -170,9 +173,10 @@ public long skip(long n) throws IOException {
     if (this.state != State.IN_PAYLOAD) {
       throw new RuntimeException();
     }
-    if (this.remainingElementBytes == 0)
-      return -1;
-    long s = this.mis.skip(n);
+    if (n <= 0 || this.remainingElementBytes <= 0)
+      return 0;
+    /* do not skip past the end of the element */
+    long s = Math.max(0, this.mis.skip(Math.min(n, this.remainingElementBytes)));
     this.remainingElementBytes = this.remainingElementBytes - s;
     return s;
   }

java-library/src/test/java/com/sandflow/smpte/mxf/RandomAccessReaderTest.java

@@ -210,4 +210,38 @@ void testTimedEvents() throws Exception {
     gsr.close();
   }
 
+  /*
+   * Bulk reads and skips must not go past the end of the element
+   */
+  @Test
+  void testReadPastElementEnd() throws Exception {
+    File f = new File(ClassLoader.getSystemResource("mxf-files/timed_events.mxf").toURI());
+    FileRandomAccessInputSource rais = new FileRandomAccessInputSource(new RandomAccessFile(f, "r"));
+
+    RandomAccessFileInfo fi = new RandomAccessFileInfo(rais, null);
+
+    ClipReader cr = new ClipReader(fi, rais);
+    assertEquals(840, cr.readAllBytes().length);
+    assertEquals(0, cr.getRemainingElementBytes());
+    assertEquals(-1, cr.read());
+
+    cr.seek(0);
+    assertEquals(840, cr.skip(Long.MAX_VALUE));
+    assertEquals(0, cr.skip(1));
+    assertEquals(-1, cr.read(new byte[16]));
+    cr.close();
+
+    GenericStreamReader gsr = new GenericStreamReader(fi, rais);
+    gsr.seek(12);
+    assertEquals(81, gsr.readAllBytes().length);
+    assertEquals(0, gsr.getRemainingElementBytes());
+    assertEquals(-1, gsr.read());
+
+    gsr.seek(12);
+    assertEquals(81, gsr.skip(Long.MAX_VALUE));
+    assertEquals(0, gsr.skip(1));
+    assertEquals(-1, gsr.read(new byte[16]));
+    gsr.close();
+  }
+
 }

java-library/src/test/java/com/sandflow/smpte/mxf/StreamingReaderTest.java

@@ -171,6 +171,37 @@ void testTimedEvents() throws Exception {
     sr.close();
   }
 
+  /*
+   * Bulk reads and skips must not go past the end of the element
+   */
+  @Test
+  void testReadPastElementEnd() throws Exception {
+    InputStream is = ClassLoader.getSystemResourceAsStream("mxf-files/timed_events.mxf");
+    assertNotNull(is);
+
+    new StreamingFileInfo(is, null);
+    StreamingReader sr = new StreamingReader(is, null);
+
+    /* Timed Events Resource */
+
+    assertTrue(sr.nextElement());
+    assertEquals(840, sr.readAllBytes().length);
+    assertEquals(-1, sr.read());
+    assertEquals(0, sr.skip(1));
+
+    /* Timed Events Ancillary Resource, in a generic stream */
+
+    assertTrue(sr.nextElement());
+    assertEquals(12L, sr.getSID());
+    assertEquals(81, sr.readAllBytes().length);
+    assertEquals(-1, sr.read(new byte[16]));
+    assertEquals(0, sr.skip(Long.MAX_VALUE));
+
+    assertFalse(sr.nextElement());
+
+    sr.close();
+  }
+
   /*
    * SMPTE ST 2067-204 ADM audio track file, from the Photon test suite
    * (https://github.com/wruppelx/photon)