added ISO/IEC 9797-1 padding method 3 + test

jpos · Dec 21, 2023 · 2187d42 · 2187d42
1 parent 36c19ed
commit 2187d42
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Showing 2 changed files with 49 additions and 9 deletions.
diff --git a/jpos/src/main/java/org/jpos/emv/cryptogram/CryptogramDataBuilder.java b/jpos/src/main/java/org/jpos/emv/cryptogram/CryptogramDataBuilder.java
@@ -33,7 +33,7 @@
  */
 public interface CryptogramDataBuilder {
 
-    final PaddingMethod ZERO_PADDING = data -> data;
+    final PaddingMethod NO_PADDING = data -> data;
 
     /**
      * ISO/IEC 9797-1 padding method 1
@@ -45,10 +45,24 @@ public interface CryptogramDataBuilder {
 
     /**
      * ISO/IEC 9797-1 padding method 2
-     *  for Block size 8,  n = 64
+     * for Block size 8,  n = 64
      */
     final PaddingMethod ISO9797Method2 = data -> ISO9797Method1.apply(data + "80");
 
+    /**
+     * ISO/IEC 9797-1 padding method 3
+     * for Block size 8,  n = 64
+     */
+    final PaddingMethod ISO9797Method3 = data -> {
+        StringBuilder sb = new StringBuilder();
+        String D = ISO9797Method1.apply(data);
+        String Ld = ISOUtil.byte2hex(ISOUtil.int2byte(data.length() / 2));
+        String Lp = ISO9797Method1.apply(Ld);
+        Lp = Ld.length() % 16 == 0 ? "" : Lp.substring(Ld.length());
+        return sb.append(Lp).append(Ld).append(D).toString();
+    };
+
+
     /**
      * Method that selects the  minimum set of data elements recommended for
      * the generation of application cryptograms described in EMV Book 2 sec 8.1.1

diff --git a/jpos/src/test/java/org/jpos/emv/cryptogram/CryptogramDataBuilderTest.java b/jpos/src/test/java/org/jpos/emv/cryptogram/CryptogramDataBuilderTest.java
@@ -7,9 +7,7 @@
 import java.util.Arrays;
 import java.util.Random;
 
-import static org.jpos.emv.cryptogram.CryptogramDataBuilder.ISO9797Method2;
-import static org.jpos.emv.cryptogram.CryptogramDataBuilder.ISO9797Method1;
-
+import static org.jpos.emv.cryptogram.CryptogramDataBuilder.*;
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
@@ -18,7 +16,6 @@
  */
 public class CryptogramDataBuilderTest {
 
-    Random r;
     byte[] r0;
     byte[] r1;
     byte[] r2;
@@ -56,7 +53,7 @@ void testPaddingMethod2() {
 
             // if data length is not multiple of n, data is padded  with 1 bit followed by 0s
             if (b.length % n > 0) {
-                byte[] padding = Arrays.copyOfRange(b_padded,  b.length, b_padded.length);
+                byte[] padding = Arrays.copyOfRange(b_padded, b.length, b_padded.length);
                 assertEquals(((byte) 0x80), padding[0]);
                 if (padding.length > 1) {
                     assertArrayEquals(ISOUtil.concat(new byte[]{(byte) 0x80}, new byte[n - b.length % n - 1]), padding);
@@ -68,7 +65,6 @@ void testPaddingMethod2() {
     @Test
     void testPaddingMethod1() {
         int n = 8; // block size
-
         Arrays.asList(r0, r1, r2).forEach(b -> {
             byte[] b_padded = ISOUtil.hex2byte(ISO9797Method1.apply(ISOUtil.hexString(b)));
 
@@ -84,11 +80,41 @@ void testPaddingMethod1() {
                 assertArrayEquals(b, b_padded);
             }
 
-            // if data length is not multiple of n, data is padded  with 0s
+            // if data length is not multiple of n, data is padded with 0s
             if (b.length % n > 0) {
                 assertArrayEquals(ISOUtil.concat(b, new byte[n - b.length % n]), b_padded);
             }
         });
     }
 
+    @Test
+    void testPaddingMethod3() {
+        int n = 8; // block size
+        Arrays.asList(r0, r1, r2).forEach(b -> {
+            byte[] b_padded = ISOUtil.hex2byte(ISO9797Method3.apply(ISOUtil.hexString(b)));
+
+            assertEquals(0, b_padded.length % n);
+
+            // if data is empty, padded data should be a 2 block of 0s
+            if (b.length == 0) {
+                assertArrayEquals(new byte[n * 2], b_padded);
+            }
+
+            // if data length is multiple of n, pad only length Block
+            if (b.length % n == 0 && b.length > 0) {
+                String pad = ISOUtil.byte2hex(b_padded).substring(0, 2 * (b_padded.length - b.length));
+                assertArrayEquals(b, Arrays.copyOfRange(b_padded, b_padded.length - b.length, b_padded.length));
+                assertArrayEquals(ISOUtil.int2byte(b.length), ISOUtil.hex2byte(ISOUtil.unPadLeft(pad, '0')));
+            }
+
+            // if data length is not multiple of n, data is right padded with 0s, then left padded with length Block
+            if (b.length % n > 0) {
+                byte[] rpad = new byte[n - b.length % n];
+                byte[] lpad = Arrays.copyOfRange(b_padded, 0, b_padded.length - b.length - rpad.length);
+                assertArrayEquals(ISOUtil.int2byte(b.length), ISOUtil.hex2byte(ISOUtil.unPadLeft(ISOUtil.byte2hex(lpad), '0')));
+                assertArrayEquals(ISOUtil.concat(ISOUtil.concat(lpad, b), rpad), b_padded);
+            }
+        });
+    }
+
 }