added sanity checks for boolean flags - related to github #1575

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

@@ -26,6 +26,6 @@ public Exportable(
 
     public boolean isExportable()
     {
-        return data[0] != 0;
+        return Utils.booleanFromByteArray(data);
     }
 }

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

@@ -26,6 +26,6 @@ public PrimaryUserID(
 
     public boolean isPrimaryUserID()
     {
-        return data[0] != 0;
+        return Utils.booleanFromByteArray(data);
     }
 }

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

@@ -26,6 +26,6 @@ public Revocable(
 
     public boolean isRevocable()
     {
-        return data[0] != 0;
+        return Utils.booleanFromByteArray(data);
     }
 }

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

@@ -19,6 +19,35 @@ static byte[] booleanToByteArray(boolean value)
         return data;
     }
 
+    /**
+     * Convert a one-entry byte array into a boolean.
+     * If the byte array doesn't have one entry, or if this entry is neither a 0 nor 1, this method throws an
+     * {@link IllegalArgumentException}.
+     * A 1 is translated into true, a 0 into false.
+     *
+     * @param bytes byte array
+     * @return boolean
+     */
+    static boolean booleanFromByteArray(byte[] bytes)
+    {
+        if (bytes.length != 1)
+        {
+            throw new IllegalStateException("Byte array has unexpected length. Expected length 1, got " + bytes.length);
+        }
+        if (bytes[0] == 0)
+        {
+            return false;
+        }
+        else if (bytes[0] == 1)
+        {
+            return true;
+        }
+        else
+        {
+            throw new IllegalStateException("Unexpected byte value for boolean encoding: " + bytes[0]);
+        }
+    }
+
     static byte[] timeToBytes(
         long    t)
     {

pg/src/test/java/org/bouncycastle/openpgp/test/BytesBooleansTest.java

@@ -0,0 +1,60 @@
+package org.bouncycastle.util.utiltest;
+
+import junit.framework.TestCase;
+import org.bouncycastle.bcpg.sig.PrimaryUserID;
+
+public class BytesBooleansTest
+    extends TestCase
+{
+    public void testParseFalse()
+    {
+        PrimaryUserID primaryUserID = new PrimaryUserID(true, false);
+
+        byte[] bFalse = primaryUserID.getData();
+        assertEquals(1, bFalse.length);
+        assertEquals(0, bFalse[0]);
+        assertFalse(primaryUserID.isPrimaryUserID());
+    }
+
+    public void testParseTrue()
+    {
+        PrimaryUserID primaryUserID = new PrimaryUserID(true, true);
+
+        byte[] bTrue = primaryUserID.getData();
+
+        assertEquals(1, bTrue.length);
+        assertEquals(1, bTrue[0]);
+        assertTrue(primaryUserID.isPrimaryUserID());
+    }
+
+    public void testParseTooShort()
+    {
+        PrimaryUserID primaryUserID = new PrimaryUserID(true, false, new byte[0]);
+        byte[] bTooShort = primaryUserID.getData();
+        try
+        {
+            primaryUserID.isPrimaryUserID();
+            fail("Should throw.");
+        }
+        catch (IllegalStateException e)
+        {
+            // expected.
+        }
+    }
+
+    public void testParseTooLong()
+    {
+        PrimaryUserID primaryUserID = new PrimaryUserID(true, false, new byte[42]);
+        byte[] bTooLong = primaryUserID.getData();
+
+        try
+        {
+            primaryUserID.isPrimaryUserID();
+            fail("Should throw.");
+        }
+        catch (IllegalStateException e)
+        {
+            // expected.
+        }
+    }
+}