format-common: initial API for PasswordEntry

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

3 files changed, 126 insertions, 0 deletions

diff --git a/format-common/src/main/kotlin/dev/msfjarvis/aps/util/time/Clocks.kt b/format-common/src/main/kotlin/dev/msfjarvis/aps/util/time/Clocks.kt
new file mode 100644
index 00000000..087a5028
--- /dev/null
+++ b/format-common/src/main/kotlin/dev/msfjarvis/aps/util/time/Clocks.kt
@@ -0,0 +1,26 @@
+/*
+ * Copyright © 2014-2021 The Android Password Store Authors. All Rights Reserved.
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package dev.msfjarvis.aps.util.time
+
+import java.time.Clock
+import java.time.Instant
+import java.time.ZoneId
+import javax.inject.Inject
+
+/**
+ * A subclass of [Clock] that uses [Clock.systemDefaultZone] to get a clock that works for the
+ * user's current time zone.
+ */
+public open class UserClock @Inject constructor() : Clock() {
+
+  private val clock = systemDefaultZone()
+
+  override fun withZone(zone: ZoneId): Clock = clock.withZone(zone)
+
+  override fun getZone(): ZoneId = clock.zone
+
+  override fun instant(): Instant = clock.instant()
+}
diff --git a/format-common/src/main/kotlin/dev/msfjarvis/aps/util/totp/Otp.kt b/format-common/src/main/kotlin/dev/msfjarvis/aps/util/totp/Otp.kt
new file mode 100644
index 00000000..e6efd794
--- /dev/null
+++ b/format-common/src/main/kotlin/dev/msfjarvis/aps/util/totp/Otp.kt
@@ -0,0 +1,74 @@
+/*
+ * Copyright © 2014-2021 The Android Password Store Authors. All Rights Reserved.
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package dev.msfjarvis.aps.util.totp
+
+import com.github.michaelbull.result.Err
+import com.github.michaelbull.result.runCatching
+import java.nio.ByteBuffer
+import java.util.Locale
+import javax.crypto.Mac
+import javax.crypto.spec.SecretKeySpec
+import kotlin.experimental.and
+import org.apache.commons.codec.binary.Base32
+
+internal object Otp {
+
+  private val BASE_32 = Base32()
+  private val STEAM_ALPHABET = "23456789BCDFGHJKMNPQRTVWXY".toCharArray()
+
+  init {
+    check(STEAM_ALPHABET.size == 26)
+  }
+
+  fun calculateCode(secret: String, counter: Long, algorithm: String, digits: String) = runCatching {
+    val algo = "Hmac${algorithm.toUpperCase(Locale.ROOT)}"
+    val decodedSecret = BASE_32.decode(secret)
+    val secretKey = SecretKeySpec(decodedSecret, algo)
+    val digest =
+      Mac.getInstance(algo).run {
+        init(secretKey)
+        doFinal(ByteBuffer.allocate(8).putLong(counter).array())
+      }
+    // Least significant 4 bits are used as an offset into the digest.
+    val offset = (digest.last() and 0xf).toInt()
+    // Extract 32 bits at the offset and clear the most significant bit.
+    val code = digest.copyOfRange(offset, offset + 4)
+    code[0] = (0x7f and code[0].toInt()).toByte()
+    val codeInt = ByteBuffer.wrap(code).int
+    check(codeInt > 0)
+    if (digits == "s") {
+      // Steam
+      var remainingCodeInt = codeInt
+      buildString {
+        repeat(5) {
+          append(STEAM_ALPHABET[remainingCodeInt % 26])
+          remainingCodeInt /= 26
+        }
+      }
+    } else {
+      // Base 10, 6 to 10 digits
+      val numDigits = digits.toIntOrNull()
+      when {
+        numDigits == null -> {
+          return Err(IllegalArgumentException("Digits specifier has to be either 's' or numeric"))
+        }
+        numDigits < 6 -> {
+          return Err(IllegalArgumentException("TOTP codes have to be at least 6 digits long"))
+        }
+        numDigits > 10 -> {
+          return Err(IllegalArgumentException("TOTP codes can be at most 10 digits long"))
+        }
+        else -> {
+          // 2^31 = 2_147_483_648, so we can extract at most 10 digits with the first one
+          // always being 0, 1, or 2. Pad with leading zeroes.
+          val codeStringBase10 = codeInt.toString(10).padStart(10, '0')
+          check(codeStringBase10.length == 10)
+          codeStringBase10.takeLast(numDigits)
+        }
+      }
+    }
+  }
+}
diff --git a/format-common/src/main/kotlin/dev/msfjarvis/aps/util/totp/TotpFinder.kt b/format-common/src/main/kotlin/dev/msfjarvis/aps/util/totp/TotpFinder.kt
new file mode 100644
index 00000000..64f22065
--- /dev/null
+++ b/format-common/src/main/kotlin/dev/msfjarvis/aps/util/totp/TotpFinder.kt
@@ -0,0 +1,26 @@
+/*
+ * Copyright © 2014-2021 The Android Password Store Authors. All Rights Reserved.
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package dev.msfjarvis.aps.util.totp
+
+/** Defines a class that can extract relevant parts of a TOTP URL for use by the app. */
+public interface TotpFinder {
+
+  /** Get the TOTP secret from the given extra content. */
+  public fun findSecret(content: String): String?
+
+  /** Get the number of digits required in the final OTP. */
+  public fun findDigits(content: String): String
+
+  /** Get the TOTP timeout period. */
+  public fun findPeriod(content: String): Long
+
+  /** Get the algorithm for the TOTP secret. */
+  public fun findAlgorithm(content: String): String
+
+  public companion object {
+    public val TOTP_FIELDS: Array<String> = arrayOf("otpauth://totp", "totp:")
+  }
+}