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.

3 files changed, 91 insertions, 0 deletions

diff --git a/app/src/main/java/com/zeapo/pwdstore/PasswordEntry.java b/app/src/main/java/com/zeapo/pwdstore/PasswordEntry.java
index d4d3fe81..ba689fe9 100644
--- a/app/src/main/java/com/zeapo/pwdstore/PasswordEntry.java
+++ b/app/src/main/java/com/zeapo/pwdstore/PasswordEntry.java
@@ -1,5 +1,7 @@
 package com.zeapo.pwdstore;
 
+import android.net.Uri;
+
 import java.io.ByteArrayOutputStream;
 import java.io.UnsupportedEncodingException;
 
@@ -13,6 +15,7 @@ public class PasswordEntry {
     private final String extraContent;
     private final String password;
     private final String username;
+    private final String totpSecret;
 
     public PasswordEntry(final ByteArrayOutputStream os) throws UnsupportedEncodingException {
         this(os.toString("UTF-8"));
@@ -23,6 +26,7 @@ public class PasswordEntry {
         password = passContent[0];
         extraContent = passContent.length > 1 ? passContent[1] : "";
         username = findUsername();
+        totpSecret = findTotpSecret(decryptedContent);
     }
 
     public String getPassword() {
@@ -37,6 +41,10 @@ public class PasswordEntry {
         return username;
     }
 
+    public String getTotpSecret() {
+        return totpSecret;
+    }
+
     public boolean hasExtraContent() {
         return extraContent.length() != 0;
     }
@@ -45,6 +53,8 @@ public class PasswordEntry {
         return username != null;
     }
 
+    public boolean hasTotp() { return totpSecret != null; }
+
     private String findUsername() {
         final String[] extraLines = extraContent.split("\n");
         for (String line : extraLines) {
@@ -56,4 +66,13 @@ public class PasswordEntry {
         }
         return null;
     }
+
+    private String findTotpSecret(String decryptedContent) {
+        for (String line : decryptedContent.split("\n")) {
+            if (line.startsWith("otpauth://totp/")) {
+                return Uri.parse(line).getQueryParameter("secret");
+            }
+        }
+        return null;
+    }
 }
diff --git a/app/src/main/java/com/zeapo/pwdstore/crypto/PgpActivity.kt b/app/src/main/java/com/zeapo/pwdstore/crypto/PgpActivity.kt
index db2acfac..905f37bf 100644
--- a/app/src/main/java/com/zeapo/pwdstore/crypto/PgpActivity.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/crypto/PgpActivity.kt
@@ -20,6 +20,7 @@ import com.zeapo.pwdstore.PasswordEntry
 import com.zeapo.pwdstore.R
 import com.zeapo.pwdstore.UserPreference
 import com.zeapo.pwdstore.pwgenDialogFragment
+import com.zeapo.pwdstore.utils.Totp
 import kotlinx.android.synthetic.main.decrypt_layout.*
 import kotlinx.android.synthetic.main.encrypt_layout.*
 import org.apache.commons.io.FileUtils
@@ -32,6 +33,7 @@ import java.io.ByteArrayInputStream
 import java.io.ByteArrayOutputStream
 import java.io.File
 import java.nio.charset.Charset
+import java.util.Date
 
 class PgpActivity : AppCompatActivity(), OpenPgpServiceConnection.OnBound {
     private val clipboard: ClipboardManager by lazy {
@@ -231,6 +233,20 @@ class PgpActivity : AppCompatActivity(), OpenPgpServiceConnection.OnBound {
                             }
                         }
 
+                        if (entry.hasTotp()) {
+                            crypto_totp_show.visibility = View.VISIBLE
+                            crypto_totp_show_label.visibility = View.VISIBLE
+                            crypto_copy_totp.visibility = View.VISIBLE
+
+                            crypto_copy_totp.setOnClickListener { copyTotpToClipBoard(Totp.calculateCode(entry.totpSecret, Date().time / 1000)) }
+                            crypto_totp_show.typeface = monoTypeface
+                            crypto_totp_show.text = Totp.calculateCode(entry.totpSecret, Date().time / 1000);
+                        } else {
+                            crypto_totp_show.visibility = View.GONE
+                            crypto_totp_show_label.visibility = View.GONE
+                            crypto_copy_totp.visibility = View.GONE
+                        }
+
                         if (settings.getBoolean("copy_on_decrypt", true)) {
                             copyPasswordToClipBoard()
                         }
@@ -460,6 +476,12 @@ class PgpActivity : AppCompatActivity(), OpenPgpServiceConnection.OnBound {
         showToast(resources.getString(R.string.clipboard_username_toast_text))
     }
 
+    private fun copyTotpToClipBoard(code: String) {
+        val clip = ClipData.newPlainText("pgp_handler_result_pm", code)
+        clipboard.primaryClip = clip
+        showToast(resources.getString(R.string.clipboard_totp_toast_text))
+    }
+
 
     private fun shareAsPlaintext() {
         if (findViewById<View>(R.id.share_password_as_plaintext) == null)
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);
+    }
+}