From 3d5dd65e306ba3ca560b3c221830ee4cdb4363fb Mon Sep 17 00:00:00 2001 From: Wiktor Kwapisiewicz Date: Mon, 6 Nov 2017 12:41:00 +0100 Subject: Display TOTP code if entry contains OTP secret TOTP is calculated on display and on copy to clipboard from secret embedded in entry (either in password or in extra) and the current time. --- .../main/java/com/zeapo/pwdstore/utils/Totp.java | 50 ++++++++++++++++++++++ 1 file changed, 50 insertions(+) create mode 100644 app/src/main/java/com/zeapo/pwdstore/utils/Totp.java (limited to 'app/src/main/java/com/zeapo/pwdstore/utils') diff --git a/app/src/main/java/com/zeapo/pwdstore/utils/Totp.java b/app/src/main/java/com/zeapo/pwdstore/utils/Totp.java new file mode 100644 index 00000000..5e4326e2 --- /dev/null +++ b/app/src/main/java/com/zeapo/pwdstore/utils/Totp.java @@ -0,0 +1,50 @@ +package com.zeapo.pwdstore.utils; + +import android.util.Log; + +import org.apache.commons.codec.binary.Base32; + +import java.math.BigInteger; +import java.nio.ByteBuffer; +import java.security.InvalidKeyException; +import java.security.NoSuchAlgorithmException; +import java.util.Arrays; + +import javax.crypto.Mac; +import javax.crypto.spec.SecretKeySpec; + +public class Totp { + + private static final String ALGORITHM = "HmacSHA1"; + private static final int TIME_WINDOW = 30; + private static final int CODE_DIGITS = 6; + + private static final Base32 BASE_32 = new Base32(); + + private Totp() { + } + + public static String calculateCode(String secret, long epochSeconds) { + SecretKeySpec signingKey = new SecretKeySpec(BASE_32.decode(secret), ALGORITHM); + + Mac mac = null; + try { + mac = Mac.getInstance(ALGORITHM); + mac.init(signingKey); + } catch (NoSuchAlgorithmException e) { + Log.e("TOTP", ALGORITHM + " unavailable - should never happen", e); + return null; + } catch (InvalidKeyException e) { + Log.e("TOTP", "Key is malformed", e); + return null; + } + + long time = epochSeconds / TIME_WINDOW; + byte[] digest = mac.doFinal(ByteBuffer.allocate(8).putLong(time).array()); + int offset = digest[digest.length - 1] & 0xf; + byte[] code = Arrays.copyOfRange(digest, offset, offset + 4); + code[0] = (byte) (0x7f & code[0]); + String strCode = new BigInteger(code).toString(); + return strCode.substring(strCode.length() - CODE_DIGITS); + } +} -- cgit v1.2.3