package com.fsck.k9.mail;
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import com.fsck.k9.mail.filter.Base64;
import com.fsck.k9.mail.filter.Hex;
public class Authentication {
private static final String US_ASCII = "US-ASCII";
private static final String XOAUTH_FORMAT = "user=%1s\001auth=Bearer %2s\001\001";
/**
* Computes the response for CRAM-MD5 authentication mechanism given the user credentials and
* the server-provided nonce.
*
* @param username The username.
* @param password The password.
* @param b64Nonce The nonce as base64-encoded string.
* @return The CRAM-MD5 response.
*
* @throws MessagingException If something went wrong.
*
* @see Authentication#computeCramMd5Bytes(String, String, byte[])
*/
public static String computeCramMd5(String username, String password, String b64Nonce)
throws MessagingException {
try {
byte[] b64NonceBytes = b64Nonce.getBytes(US_ASCII);
byte[] b64CRAM = computeCramMd5Bytes(username, password, b64NonceBytes);
return new String(b64CRAM, US_ASCII);
} catch (MessagingException e) {
throw e;
} catch (Exception e) {
throw new MessagingException("This shouldn't happen", e);
}
}
/**
* Computes the response for CRAM-MD5 authentication mechanism given the user credentials and
* the server-provided nonce.
*
* @param username The username.
* @param password The password.
* @param b64Nonce The nonce as base64-encoded byte array.
* @return The CRAM-MD5 response as byte array.
*
* @throws MessagingException If something went wrong.
*
* @see <a href="https://tools.ietf.org/html/rfc2195">RFC 2195</a>
*/
public static byte[] computeCramMd5Bytes(String username, String password, byte[] b64Nonce)
throws MessagingException {
try {
byte[] nonce = Base64.decodeBase64(b64Nonce);
byte[] secretBytes = password.getBytes();
MessageDigest md = MessageDigest.getInstance("MD5");
if (secretBytes.length > 64) {
secretBytes = md.digest(secretBytes);
}
byte[] ipad = new byte[64];
byte[] opad = new byte[64];
System.arraycopy(secretBytes, 0, ipad, 0, secretBytes.length);
System.arraycopy(secretBytes, 0, opad, 0, secretBytes.length);
for (int i = 0; i < ipad.length; i++) ipad[i] ^= 0x36;
for (int i = 0; i < opad.length; i++) opad[i] ^= 0x5c;
md.update(ipad);
byte[] firstPass = md.digest(nonce);
md.update(opad);
byte[] result = md.digest(firstPass);
String plainCRAM = username + " " + Hex.encodeHex(result);
byte[] b64CRAM = Base64.encodeBase64(plainCRAM.getBytes());
return b64CRAM;
} catch (Exception e) {
throw new MessagingException("Something went wrong during CRAM-MD5 computation", e);
}
}
public static String computeXoauth(String username, String authToken) throws UnsupportedEncodingException {
String formattedAuthenticationString = String.format(XOAUTH_FORMAT, username, authToken);
byte[] base64encodedAuthenticationString =
Base64.encodeBase64(formattedAuthenticationString.getBytes());
return new String(base64encodedAuthenticationString, US_ASCII);
}
}