[netty#4793] Correctly add newlines when encode base64

Motivation:

We not correctly added newlines if the src data needed to be padded. This regression was introduced by '63426fc3ed083513c07a58b45381f5c10dd47061'

Modifications:

- Correctly handling newlines
- Add unit test that proves the fix.

Result:

No more invalid base64 encoded data.

codec/src/main/java/io/netty/handler/codec/base64/Base64.java

@@ -126,15 +126,12 @@ public static ByteBuf encode(
         int e = 0;
         int len2 = len - 2;
         int lineLength = 0;
-        for (; d < len2; e += 4) {
+        for (; d < len2; d += 3, e += 4) {
             encode3to4(src, d + off, 3, dest, e, dialect);
 
             lineLength += 4;
-            d += 3;
 
-            if (breakLines && lineLength == MAX_LINE_LENGTH
-                    // Only add NEW_LINE if we not ended directly on the MAX_LINE_LENGTH
-                    && d < len2) {
+            if (breakLines && lineLength == MAX_LINE_LENGTH) {
                 dest.setByte(e + 4, NEW_LINE);
                 e ++;
                 lineLength = 0;
@@ -146,6 +143,11 @@ public static ByteBuf encode(
             e += 4;
         } // end if: some padding needed
 
+        // Remove last byte if it's a newline
+        if (e > 1 && dest.getByte(e - 1) == NEW_LINE) {
+            e--;
+        }
+
         return dest.slice(0, e);
     }
 

codec/src/test/java/io/netty/handler/codec/base64/Base64Test.java

@@ -16,10 +16,16 @@
 package io.netty.handler.codec.base64;
 
 import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
 import io.netty.util.CharsetUtil;
 import org.junit.Test;
 
 
+import java.io.ByteArrayInputStream;
+import java.nio.charset.Charset;
+import java.security.cert.CertificateFactory;
+import java.security.cert.X509Certificate;
+
 import static io.netty.buffer.Unpooled.copiedBuffer;
 import static org.junit.Assert.assertEquals;
 
@@ -45,6 +51,62 @@ public void testAddNewLine() {
         testEncode(src, expectedEncoded);
     }
 
+    @Test
+    public void testEncodeEmpty() {
+        ByteBuf src = Unpooled.EMPTY_BUFFER;
+        ByteBuf expectedEncoded = Unpooled.EMPTY_BUFFER;
+        testEncode(src, expectedEncoded);
+    }
+
+    @Test
+    public void testPaddingNewline() throws Exception {
+        String cert = "-----BEGIN CERTIFICATE-----\n" +
+                "MIICqjCCAjGgAwIBAgICI1YwCQYHKoZIzj0EATAmMSQwIgYDVQQDDBtUcnVzdGVk\n" +
+                "IFRoaW4gQ2xpZW50IFJvb3QgQ0EwIhcRMTYwMTI0MTU0OTQ1LTA2MDAXDTE2MDQy\n" +
+                "NTIyNDk0NVowYzEwMC4GA1UEAwwnREMgMGRlYzI0MGYtOTI2OS00MDY5LWE2MTYt\n" +
+                "YjJmNTI0ZjA2ZGE0MREwDwYDVQQLDAhEQyBJUFNFQzEcMBoGA1UECgwTVHJ1c3Rl\n" +
+                "ZCBUaGluIENsaWVudDB2MBAGByqGSM49AgEGBSuBBAAiA2IABOB7pZYC24sF5gJm\n" +
+                "OHXhasxmrNYebdtSAiQRgz0M0pIsogsFeTU/W0HTlTOqwDDckphHESAKHVxa6EBL\n" +
+                "d+/8HYZ1AaCmXtG73XpaOyaRr3TipJl2IaJzwuehgDHs0L+qcqOB8TCB7jAwBgYr\n" +
+                "BgEBEAQEJgwkMGRlYzI0MGYtOTI2OS00MDY5LWE2MTYtYjJmNTI0ZjA2ZGE0MCMG\n" +
+                "CisGAQQBjCHbZwEEFQwTNDkwNzUyMjc1NjM3MTE3Mjg5NjAUBgorBgEEAYwh22cC\n" +
+                "BAYMBDIwNTkwCwYDVR0PBAQDAgXgMAkGA1UdEwQCMAAwHQYDVR0OBBYEFGWljaKj\n" +
+                "wiGqW61PgLL/zLxj4iirMB8GA1UdIwQYMBaAFA2FRBtG/dGnl0iXP2uKFwJHmEQI\n" +
+                "MCcGA1UdJQQgMB4GCCsGAQUFBwMCBggrBgEFBQcDAQYIKwYBBQUHAwkwCQYHKoZI\n" +
+                "zj0EAQNoADBlAjAQFP8rMLUxl36u8610LsSCiRG8pP3gjuLaaJMm3tjbVue/TI4C\n" +
+                "z3iL8i96YWK0VxcCMQC7pf6Wk3RhUU2Sg6S9e6CiirFLDyzLkaWxuCnXcOwTvuXT\n" +
+                "HUQSeUCp2Q6ygS5qKyc=\n" +
+                "-----END CERTIFICATE-----";
+
+        String expected = "MIICqjCCAjGgAwIBAgICI1YwCQYHKoZIzj0EATAmMSQwIgYDVQQDDBtUcnVzdGVkIFRoaW4gQ2xp\n" +
+                "ZW50IFJvb3QgQ0EwIhcRMTYwMTI0MTU0OTQ1LTA2MDAXDTE2MDQyNTIyNDk0NVowYzEwMC4GA1UE\n" +
+                "AwwnREMgMGRlYzI0MGYtOTI2OS00MDY5LWE2MTYtYjJmNTI0ZjA2ZGE0MREwDwYDVQQLDAhEQyBJ\n" +
+                "UFNFQzEcMBoGA1UECgwTVHJ1c3RlZCBUaGluIENsaWVudDB2MBAGByqGSM49AgEGBSuBBAAiA2IA\n" +
+                "BOB7pZYC24sF5gJmOHXhasxmrNYebdtSAiQRgz0M0pIsogsFeTU/W0HTlTOqwDDckphHESAKHVxa\n" +
+                "6EBLd+/8HYZ1AaCmXtG73XpaOyaRr3TipJl2IaJzwuehgDHs0L+qcqOB8TCB7jAwBgYrBgEBEAQE\n" +
+                "JgwkMGRlYzI0MGYtOTI2OS00MDY5LWE2MTYtYjJmNTI0ZjA2ZGE0MCMGCisGAQQBjCHbZwEEFQwT\n" +
+                "NDkwNzUyMjc1NjM3MTE3Mjg5NjAUBgorBgEEAYwh22cCBAYMBDIwNTkwCwYDVR0PBAQDAgXgMAkG\n" +
+                "A1UdEwQCMAAwHQYDVR0OBBYEFGWljaKjwiGqW61PgLL/zLxj4iirMB8GA1UdIwQYMBaAFA2FRBtG\n" +
+                "/dGnl0iXP2uKFwJHmEQIMCcGA1UdJQQgMB4GCCsGAQUFBwMCBggrBgEFBQcDAQYIKwYBBQUHAwkw\n" +
+                "CQYHKoZIzj0EAQNoADBlAjAQFP8rMLUxl36u8610LsSCiRG8pP3gjuLaaJMm3tjbVue/TI4Cz3iL\n" +
+                "8i96YWK0VxcCMQC7pf6Wk3RhUU2Sg6S9e6CiirFLDyzLkaWxuCnXcOwTvuXTHUQSeUCp2Q6ygS5q\n" +
+                "Kyc=";
+
+        ByteBuf src =  Unpooled.wrappedBuffer(certFromString(cert).getEncoded());
+        ByteBuf expectedEncoded = copiedBuffer(expected, CharsetUtil.US_ASCII);
+        testEncode(src, expectedEncoded);
+    }
+
+    private static X509Certificate certFromString(String string) throws Exception {
+        CertificateFactory factory = CertificateFactory.getInstance("X.509");
+        ByteArrayInputStream bin = new ByteArrayInputStream(string.getBytes(CharsetUtil.US_ASCII));
+        try {
+            return (X509Certificate) factory.generateCertificate(bin);
+        } finally {
+            bin.close();
+        }
+    }
+
     private static void testEncode(ByteBuf src, ByteBuf expectedEncoded) {
         ByteBuf encoded = Base64.encode(src, true, Base64Dialect.STANDARD);
         try {