Data encryption using Base64 PublicKey & decryption using Base64 PrivateKey

[Eric-Chomba]

Data encryption & decryption works with Public & Private Keys in raw binary formats like these
BinaryKeys.zip using this test case

    public void runApp() {
        try {
            String data = "Secret message";
            //InputStream publicStream = Display.getInstance().getResourceAsStream(MyApp.class, "/BinaryTestPublicKey.pem");
            InputStream publicStream = Display.getInstance().getResourceAsStream(MyApp.class, "/Base64TestPublicKey.pem");
            PublicKey publicKey = PublicKey.rsa(Util.readInputStream(publicStream));
            Log.p("publicKey: " + Base64.encode(publicKey.getEncoded()));
            byte[] cipher = Cipher.rsaEncrypt(Cipher.RSA_OAEP_SHA256, publicKey, data.getBytes());
            Log.p("cipherText: " + Base64.encode(cipher));

            //InputStream privateStream = Display.getInstance().getResourceAsStream(MyApp.class, "/BinaryTestPrivateKey.pem");
            InputStream privateStream = Display.getInstance().getResourceAsStream(MyApp.class, "/Base64TestPrivateKey.pem");
            PrivateKey privateKey = PrivateKey.rsa(Util.readInputStream(privateStream));
            Log.p("privateKey: " + Base64.encode(privateKey.getEncoded()));
            byte[] plain = Cipher.rsaDecrypt(Cipher.RSA_OAEP_SHA256, privateKey, cipher);
            Log.p("plainText: " + new String(plain, StandardCharsets.UTF_8));

            publicStream.close();
            privateStream.close();
        } catch (Exception e) {
            //Log.p("Error " + e);
            e.printStackTrace();
        }
    }

Changing keys to Base64 formats like these
Base64Keys.zip
throws the following InvalidKeyException

com.codename1.security.CryptoException: RSA encrypt failed: java.security.InvalidKeyException: invalid key format
	at com.codename1.security.Cipher.rsaEncrypt(Cipher.java:137)
	at com.example.myapp.MyApp.runApp(MyApp.java:62)
	at com.codename1.system.Lifecycle.start(Lifecycle.java:125)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:569)
	at com.codename1.impl.javase.Executor$3$2.run(Executor.java:368)
	at com.codename1.ui.Display.executeSerialCall(Display.java:1592)
	at com.codename1.ui.Display.processSerialCalls(Display.java:1576)
	at com.codename1.ui.Display.mainEDTLoop(Display.java:1268)
	at com.codename1.ui.RunnableWrapper.run(RunnableWrapper.java:139)
	at com.codename1.impl.CodenameOneThread.run(CodenameOneThread.java:179)
Caused by: java.lang.RuntimeException: RSA encrypt failed: java.security.InvalidKeyException: invalid key format
	at com.codename1.impl.javase.JavaSEPort.rsaEncrypt(JavaSEPort.java:21829)
	at com.codename1.io.Util.rsaEncrypt(Util.java:1864)
	at com.codename1.security.Cipher.rsaEncrypt(Cipher.java:135)

These Base64 keys formats are already working in backend. How can they also work in Codename One app?

[shai-almog]

The problem is that PublicKey.rsa(...) / PrivateKey.rsa(...) take the decoded DER bytes, not PEM text. Your "binary" files already are DER, which is why those work. The Base64 ones are PEM-armored, so what reaches the key factory is still ASCII.

Rather than have you write the stripping code, I've added it to the API. On the next update you'll be able to write:

InputStream publicStream = Display.getInstance().getResourceAsStream(MyApp.class, "/Base64TestPublicKey.pem");
PublicKey publicKey = PublicKey.fromPem(Util.readInputStream(publicStream));

InputStream privateStream = Display.getInstance().getResourceAsStream(MyApp.class, "/Base64TestPrivateKey.pem");
PrivateKey privateKey = PrivateKey.fromPem(Util.readInputStream(privateStream));

The rest of your code can remain unchanged. fromPem figures out RSA vs EC from the key itself, handles PUBLIC KEY/PRIVATE KEY (SPKI/PKCS#8) as well as the older RSA PRIVATE KEY, RSA PUBLIC KEY and EC PRIVATE KEY files, and copes with CRLF and stray surrounding text.

In the meantime, on the current release you can strip the armor yourself. Note you can't just decode the whole file - isn't a valid Base64 character, so Base64.decode returns null for an armored file (newlines are fine, the header lines are not):

private static byte[] pemToDer(InputStream is) throws IOException {
    String pem = new String(Util.readInputStream(is), "UTF-8");
    StringBuilder b = new StringBuilder();
    for (String line : Util.split(pem, "\n")) {
        line = line.trim();
        if (line.length() == 0 || line.startsWith("-----")) {
            continue;
        }
        b.append(line);
    }
    return Base64.decode(b.toString().getBytes("UTF-8"));
}

Then PublicKey.rsa(pemToDer(publicStream)) and PrivateKey.rsa(pemToDer(privateStream)).

One thing to check on the private key if you go that route: it must be PKCS#8 (-----BEGIN PRIVATE KEY-----). If yours says -----BEGIN RSA PRIVATE KEY----- that's PKCS#1, and it decodes to valid-looking bytes but is still rejected with the same message. Convert it once with openssl pkcs8 -topk8 -nocrypt -in key.pem -out key_pkcs8.pem. The new fromPem handles that case for you.

[Eric-Chomba]

Thanks. Changing to

PublicKey publicKey = PublicKey.rsa(pemToDer(publicStream));

fails with this exception

com.codename1.security.CryptoException: RSA encrypt failed: java.security.InvalidKeyException: IOException: DerValue.getOID, not an OID -96
	at com.codename1.security.Cipher.rsaEncrypt(Cipher.java:137)
	at com.example.myapp.MyApp.runApp(MyApp.java:64)
	at com.codename1.system.Lifecycle.start(Lifecycle.java:125)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:569)
	at com.codename1.impl.javase.Executor$3$2.run(Executor.java:368)
	at com.codename1.ui.Display.executeSerialCall(Display.java:1592)
	at com.codename1.ui.Display.processSerialCalls(Display.java:1576)
	at com.codename1.ui.Display.mainEDTLoop(Display.java:1268)
	at com.codename1.ui.RunnableWrapper.run(RunnableWrapper.java:139)
	at com.codename1.impl.CodenameOneThread.run(CodenameOneThread.java:179)
Caused by: java.lang.RuntimeException: RSA encrypt failed: java.security.InvalidKeyException: IOException: DerValue.getOID, not an OID -96
	at com.codename1.impl.javase.JavaSEPort.rsaEncrypt(JavaSEPort.java:21829)
	at com.codename1.io.Util.rsaEncrypt(Util.java:1864)
	at com.codename1.security.Cipher.rsaEncrypt(Cipher.java:135)