CODEC-313: Fix possible ArrayIndexOutOfBoundsException thrown by QuotedPrintableCodec.encodeQuotedPrintable() method (#221)

* CODEC-313: Fix possible ArrayIndexOutOfBoundsException

Signed-off-by: Arthur Chan <arthur.chan@adalogics.com>

* CODEC-313: Add unit test

Signed-off-by: Arthur Chan <arthur.chan@adalogics.com>

---------

Signed-off-by: Arthur Chan <arthur.chan@adalogics.com>

Author: arthurscchan

src/main/java/org/apache/commons/codec/net/QuotedPrintableCodec.java

@@ -84,6 +84,11 @@ public class QuotedPrintableCodec implements BinaryEncoder, BinaryDecoder, Strin
 
     private static final byte LF = 10;
 
+    /**
+     * Minimum length required for the byte arrays used by encodeQuotedPrintable method
+     */
+    private static final int MIN_BYTES = 3;
+
     /**
      * Safe line length for quoted printable encoded text.
      */
@@ -208,6 +213,10 @@ public static final byte[] encodeQuotedPrintable(BitSet printable, final byte[]
         final int bytesLength = bytes.length;
 
         if (strict) {
+            if (bytesLength < MIN_BYTES) {
+                return null;
+            }
+
             int pos = 1;
             // encode up to buffer.length - 3, the last three octets will be treated
             // separately for simplification of note #3

src/test/java/org/apache/commons/codec/net/QuotedPrintableCodecTest.java

@@ -227,6 +227,12 @@ public void testSoftLineBreakEncode() throws Exception {
         assertEquals(qpdata, qpcodec.encode(decoded));
     }
 
+    @Test
+    public void testTooShortByteArray() throws Exception{
+        final QuotedPrintableCodec qpcodec = new QuotedPrintableCodec(true);
+        assertNull(qpcodec.encode("AA"), "Result should be null.");
+    }
+
     @Test
     public void testTrailingSpecial() throws Exception {
         final QuotedPrintableCodec qpcodec = new QuotedPrintableCodec(true);