Fix unpacking time (unsigned int) from octets for large values

pg/src/main/java/org/bouncycastle/bcpg/sig/Utils.java

@@ -57,7 +57,7 @@ static long timeFromBytes(byte[] bytes)
             throw new IllegalStateException("Byte array has unexpected length. Expected length 4, got " + bytes.length);
         }
 
-        return Pack.bigEndianToInt(bytes, 0);
+        return Pack.bigEndianToInt(bytes, 0) & 0xFFFFFFFFL; // time is unsigned
     }
 
     static byte[] timeToBytes(long t)

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

@@ -24,7 +24,8 @@ public void testPacketParsing()
                         new OnePassSignaturePacketTest(),
                         new OpenPgpMessageTest(),
                         new FingerprintUtilTest(),
-                        new EncryptedMessagePacketTest()
+                        new EncryptedMessagePacketTest(),
+                        new UtilsTest()
                 };
 
         for (int i = 0; i != tests.length; i++)

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

@@ -0,0 +1,40 @@
+package org.bouncycastle.bcpg.test;
+
+import org.bouncycastle.bcpg.sig.KeyExpirationTime;
+import org.bouncycastle.util.test.SimpleTest;
+
+public class UtilsTest
+        extends SimpleTest
+{
+    @Override
+    public String getName()
+    {
+        return "UtilsTest";
+    }
+
+    @Override
+    public void performTest()
+            throws Exception
+    {
+        testRoundtrippingLargeUnsignedInt();
+    }
+
+    private void testRoundtrippingLargeUnsignedInt()
+    {
+        // Integer.MAX_VALUE < large < 0xffffffff
+        long large = 2523592696L; // fits a 32-bit *unsigned* int, but overflows signed int
+        // KeyExpirationTime packs the time into 4 octets
+        KeyExpirationTime kexp = new KeyExpirationTime(false, large);
+        // getTime() parses the time from 4 octets
+        isEquals("Roundtripped unsigned int mismatches before packet parser pass", large, kexp.getTime());
+
+        // To be safe, do an additional packet encode/decode roundtrip
+        KeyExpirationTime pKexp = new KeyExpirationTime(kexp.isCritical(), kexp.isLongLength(), kexp.getData());
+        isEquals("Roundtripped unsigned int mismatches after packet parser pass", large, pKexp.getTime());
+    }
+
+    public static void main(String[] args)
+    {
+        runTest(new UtilsTest());
+    }
+}