#1736 FingerprintUtil: Add prettifyFingerprint method

Author: gefeili

pg/src/main/java/org/bouncycastle/bcpg/FingerprintUtil.java

@@ -1,10 +1,35 @@
 package org.bouncycastle.bcpg;
 
 import org.bouncycastle.util.Pack;
+import org.bouncycastle.util.encoders.Hex;
 
 public class FingerprintUtil
 {
 
+    /**
+     * Derive a key-id from the given key fingerprint.
+     * This method can derive key-ids from v4, v5 (LibrePGP) and v6 keys.
+     * For keys with other versions (2,3) it will return 0.
+     *
+     * @param keyVersion version of the key
+     * @param fingerprint fingerprint of the key
+     * @return derived key-id
+     */
+    public static long keyIdFromFingerprint(int keyVersion, byte[] fingerprint)
+    {
+        switch (keyVersion)
+        {
+            case PublicKeyPacket.VERSION_4:
+                return keyIdFromV4Fingerprint(fingerprint);
+            case PublicKeyPacket.LIBREPGP_5:
+                return keyIdFromLibrePgpFingerprint(fingerprint);
+            case PublicKeyPacket.VERSION_6:
+                return keyIdFromV6Fingerprint(fingerprint);
+            default:
+                return 0;
+        }
+    }
+
     /**
      * Derive a 64 bit key-id from a version 6 OpenPGP fingerprint.
      * For v6 keys, the key-id corresponds to the left-most 8 octets of the fingerprint.
@@ -112,4 +137,55 @@ public static void writeKeyID(long keyID, byte[] bytes)
     {
         writeKeyID(keyID, bytes, 0);
     }
+
+    public static String prettifyFingerprint(byte[] fingerprint)
+    {
+        // -DM Hex.toHexString
+        String hex = Hex.toHexString(fingerprint).toUpperCase();
+        StringBuilder sb = new StringBuilder();
+        switch (hex.length())
+        {
+            case 32:
+                // v3 keys
+                for (int i = 0; i < 4; i++)
+                {
+                    sb.append(hex, i * 4, (i + 1) * 4).append(' ');
+                }
+                sb.append(' ');
+                for (int i = 4; i < 7; i++)
+                {
+                    sb.append(hex, i * 4, (i + 1) * 4).append(' ');
+                }
+                sb.append(hex, 28, 32);
+                return sb.toString();
+            case 40:
+                // v4 keys
+                for (int i = 0; i <= 4; i++)
+                {
+                    sb.append(hex, i * 4, (i + 1) * 4).append(' ');
+                }
+                sb.append(' ');
+                for (int i = 5; i <= 8; i++)
+                {
+                    sb.append(hex, i * 4, (i + 1) * 4).append(' ');
+                }
+                sb.append(hex, 36, 40);
+                return sb.toString();
+            case 64:
+                // v5, v6 keys
+                for (int i = 0; i < 4; i++)
+                {
+                    sb.append(hex, i * 8, (i + 1) * 8).append(' ');
+                }
+                sb.append(' ');
+                for (int i = 4; i < 7; i++)
+                {
+                    sb.append(hex, i * 8, (i + 1) * 8).append(' ');
+                }
+                sb.append(hex, 56, 64);
+                return sb.toString();
+            default:
+                return hex;
+        }
+    }
 }

pg/src/test/java/org/bouncycastle/bcpg/test/FingerprintUtilTest.java

@@ -47,6 +47,19 @@ private void testLibrePgpKeyIdFromFingerprint()
             -3812177997909612905L, FingerprintUtil.keyIdFromLibrePgpFingerprint(decoded));
     }
 
+    private void testKeyIdFromFingerprint()
+    {
+        isEquals("v4 key-id from fingerprint mismatch",
+                -5425419407118114754L, FingerprintUtil.keyIdFromFingerprint(
+                        4, Hex.decode("1D018C772DF8C5EF86A1DCC9B4B509CB5936E03E")));
+        isEquals("v5 key-id from fingerprint mismatch",
+                -3812177997909612905L, FingerprintUtil.keyIdFromFingerprint(
+                        5, Hex.decode("cb186c4f0609a697e4d52dfa6c722b0c1f1e27c18a56708f6525ec27bad9acc9")));
+        isEquals("v6 key-id from fingerprint mismatch",
+                -3812177997909612905L, FingerprintUtil.keyIdFromFingerprint(
+                        6, Hex.decode("cb186c4f0609a697e4d52dfa6c722b0c1f1e27c18a56708f6525ec27bad9acc9")));
+    }
+
     private void testLeftMostEqualsRightMostFor8Bytes()
     {
         byte[] bytes = new byte[] {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08};
@@ -79,6 +92,23 @@ private void testWriteKeyIdToBytes()
         }
     }
 
+    private void testPrettifyFingerprint()
+    {
+        isEquals("Prettified v4 fingerprint mismatch",
+                "1D01 8C77 2DF8 C5EF 86A1  DCC9 B4B5 09CB 5936 E03E",
+                FingerprintUtil.prettifyFingerprint(Hex.decode("1D018C772DF8C5EF86A1DCC9B4B509CB5936E03E")));
+        isEquals("Prettified v5/v6 fingerprint mismatch",
+                "CB186C4F 0609A697 E4D52DFA 6C722B0C  1F1E27C1 8A56708F 6525EC27 BAD9ACC9",
+                FingerprintUtil.prettifyFingerprint(Hex.decode("cb186c4f0609a697e4d52dfa6c722b0c1f1e27c18a56708f6525ec27bad9acc9")));
+    }
+
+    private void testPrettifyFingerprintReturnsHexForUnknownFormat()
+    {
+        String fp = "C0FFEE1DECAFF0";
+        isEquals("Prettifying fingerprint with unknown format MUST return uppercase hex fingerprint",
+                fp, FingerprintUtil.prettifyFingerprint(Hex.decode(fp)));
+    }
+
     @Override
     public String getName()
     {
@@ -95,6 +125,9 @@ public void performTest()
         testLibrePgpKeyIdFromFingerprint();
         testLeftMostEqualsRightMostFor8Bytes();
         testWriteKeyIdToBytes();
+        testKeyIdFromFingerprint();
+        testPrettifyFingerprint();
+        testPrettifyFingerprintReturnsHexForUnknownFormat();
     }
 
     public static void main(String[] args)