feat(app): add an about screen

Version with build number, documentation and project links, Ko-fi, the privacy
statement, the certificate this copy was really signed with, and the licenses.
Debug builds also show the git commit, since a test build can share its version
with a release.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

3 files changed, 224 insertions, 1 deletions

diff --git a/app/src/main/java/app/passwordstore/ui/settings/AboutScreen.kt b/app/src/main/java/app/passwordstore/ui/settings/AboutScreen.kt
new file mode 100644
index 00000000..fd47c119
--- /dev/null
+++ b/app/src/main/java/app/passwordstore/ui/settings/AboutScreen.kt
@@ -0,0 +1,208 @@
+/*
+ * Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package app.passwordstore.ui.settings
+
+import android.content.ActivityNotFoundException
+import android.content.Context
+import android.content.Intent
+import android.content.pm.PackageManager
+import androidx.compose.foundation.BorderStroke
+import androidx.compose.foundation.Image
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.shape.CircleShape
+import androidx.compose.material3.Button
+import androidx.compose.material3.ButtonDefaults
+import androidx.compose.material3.ListItem
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.res.painterResource
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.semantics.Role
+import androidx.compose.ui.text.font.FontFamily
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.unit.dp
+import androidx.core.net.toUri
+import androidx.fragment.app.FragmentActivity
+import app.passwordstore.BuildConfig
+import app.passwordstore.R
+import app.passwordstore.ui.compose.theme.SpacingMedium
+import app.passwordstore.ui.crypto.copyTextToClipboard
+import app.passwordstore.util.extensions.getPackageInfoCompat
+import app.passwordstore.util.extensions.snackbar
+import java.security.MessageDigest
+
+private const val REPOSITORY = "https://github.com/danixland/HardenedPass"
+private const val DOCUMENTATION = "https://danix.xyz/hardenedpass"
+private const val KO_FI = "https://ko-fi.com/K6Y520C9I6"
+
+/**
+ * What ships in the APK and its license, by hand: update it when a dependency comes or goes. A
+ * generating plugin would be one more build dependency for a list this short.
+ */
+private val LICENSES =
+  listOf(
+    "AndroidX, Jetpack Compose" to "Apache-2.0",
+    "Apache Commons Codec, Curtains, Guava, JavaEWAH, JSpecify, uri-kmp" to "Apache-2.0",
+    "Bouncy Castle" to "Bouncy Castle Licence (MIT)",
+    "Dagger, Hilt" to "Apache-2.0",
+    "EFF Diceware word list" to "CC-BY",
+    "JGit" to "EDL-1.0 (BSD-3-Clause)",
+    "kotlin-result" to "ISC",
+    "Kotlin, kotlinx" to "Apache-2.0",
+    "LeakCanary plumber, logcat" to "Apache-2.0",
+    "Manrope" to "OFL-1.1",
+    "PGPainless" to "Apache-2.0",
+    "Public Suffix List" to "MPL-2.0",
+    "SLF4J" to "MIT",
+    "sshj" to "Apache-2.0",
+    "sublime-fuzzy" to "MIT",
+    "ZXing, zxing-android-embedded" to "Apache-2.0",
+  )
+
+/** `0.3.0 (300)`, followed by the [commit] on the debug builds that have one. */
+internal fun versionLine(name: String, code: Int, commit: String): String =
+  if (commit.isEmpty()) "$name ($code)" else "$name ($code) · $commit"
+
+/** The changelog at the tag of [versionName], without a suffix like `-debug`. */
+internal fun changelogUrl(versionName: String): String =
+  "$REPOSITORY/blob/v${versionName.substringBefore('-')}/CHANGELOG.md"
+
+/** SHA-256 of [certificate] as `apksigner` and `keytool` users compare it, colon separated. */
+internal fun certificateFingerprint(certificate: ByteArray): String =
+  MessageDigest.getInstance("SHA-256").digest(certificate).joinToString(":") { "%02X".format(it) }
+
+/** The certificate this copy was really signed with, so it can be compared with the published. */
+private fun Context.signingFingerprint(): String? =
+  packageManager
+    .getPackageInfoCompat(packageName, PackageManager.GET_SIGNING_CERTIFICATES)
+    .signingInfo
+    ?.apkContentsSigners
+    ?.firstOrNull()
+    ?.let { certificateFingerprint(it.toByteArray()) }
+
+/** The about screen. Links leave for the browser: the app itself makes no connection for them. */
+@Composable
+fun AboutDestination(
+  activity: FragmentActivity,
+  onBack: () -> Unit,
+  modifier: Modifier = Modifier,
+) {
+  val fingerprint = remember { activity.signingFingerprint() }
+  AboutScreen(
+    version =
+      versionLine(BuildConfig.VERSION_NAME, BuildConfig.VERSION_CODE, BuildConfig.GIT_COMMIT),
+    changelog = changelogUrl(BuildConfig.VERSION_NAME),
+    fingerprint = fingerprint,
+    onCopy = { activity.copyTextToClipboard(it) },
+    onOpen = { url ->
+      try {
+        activity.startActivity(Intent(Intent.ACTION_VIEW, url.toUri()))
+      } catch (_: ActivityNotFoundException) {
+        activity.snackbar(message = activity.getString(R.string.about_no_browser))
+      }
+    },
+    onBack = onBack,
+    modifier = modifier,
+  )
+}
+
+@Composable
+private fun AboutScreen(
+  version: String,
+  changelog: String,
+  fingerprint: String?,
+  onCopy: (String) -> Unit,
+  onOpen: (String) -> Unit,
+  onBack: () -> Unit,
+  modifier: Modifier = Modifier,
+) {
+  SettingsScaffold(stringResource(R.string.about), onBack, modifier) {
+    Column(
+      Modifier.fillMaxWidth().padding(SpacingMedium),
+      horizontalAlignment = Alignment.CenterHorizontally,
+      verticalArrangement = Arrangement.spacedBy(SpacingMedium),
+    ) {
+      Box(Modifier.size(96.dp).clip(CircleShape)) {
+        Image(painterResource(R.drawable.ic_launcher_background), contentDescription = null)
+        Image(painterResource(R.drawable.ic_launcher_foreground), contentDescription = null)
+      }
+      Text(stringResource(R.string.app_name), style = MaterialTheme.typography.headlineSmall)
+      Text(stringResource(R.string.about_summary), textAlign = TextAlign.Center)
+    }
+    AboutRow(stringResource(R.string.about_version), version) { onCopy(version) }
+    AboutRow(stringResource(R.string.about_docs)) { onOpen(DOCUMENTATION) }
+    AboutRow(stringResource(R.string.about_changelog)) { onOpen(changelog) }
+    AboutRow(stringResource(R.string.about_source)) { onOpen(REPOSITORY) }
+    AboutRow(stringResource(R.string.about_issues)) { onOpen("$REPOSITORY/issues") }
+    // White in both themes: the logo's dark outline disappears on a dark background, and Ko-fi
+    // asks that the logo itself stays as it is.
+    Button(
+      onClick = { onOpen(KO_FI) },
+      modifier = Modifier.fillMaxWidth().padding(SpacingMedium),
+      colors =
+        ButtonDefaults.buttonColors(containerColor = Color.White, contentColor = Color.Black),
+      border = BorderStroke(1.dp, MaterialTheme.colorScheme.outline),
+    ) {
+      Image(
+        painterResource(R.drawable.ic_kofi_symbol),
+        contentDescription = null,
+        modifier = Modifier.height(24.dp),
+      )
+      Box(Modifier.width(SpacingMedium))
+      Text(stringResource(R.string.about_support))
+    }
+    ListItem(
+      headlineContent = { Text(stringResource(R.string.about_privacy_title)) },
+      supportingContent = { Text(stringResource(R.string.about_privacy)) },
+      colors = rowColors(),
+    )
+    if (fingerprint != null)
+      ListItem(
+        headlineContent = { Text(stringResource(R.string.about_certificate)) },
+        supportingContent = { Text(fingerprint, fontFamily = FontFamily.Monospace) },
+        modifier = Modifier.clickable(role = Role.Button) { onCopy(fingerprint) },
+        colors = rowColors(),
+      )
+    AboutRow(stringResource(R.string.about_license), stringResource(R.string.about_license_text)) {
+      onOpen("$REPOSITORY/blob/master/LICENSE.txt")
+    }
+    ListItem(
+      headlineContent = { Text(stringResource(R.string.about_libraries)) },
+      colors = rowColors(),
+    )
+    LICENSES.forEach { (name, license) ->
+      ListItem(
+        headlineContent = { Text(name) },
+        supportingContent = { Text(license) },
+        colors = rowColors(),
+      )
+    }
+  }
+}
+
+@Composable
+private fun AboutRow(title: String, summary: String? = null, onClick: () -> Unit) {
+  ListItem(
+    headlineContent = { Text(title) },
+    supportingContent = summary?.let { { Text(it) } },
+    modifier = Modifier.clickable(role = Role.Button, onClick = onClick),
+    colors = rowColors(),
+  )
+}
diff --git a/app/src/main/java/app/passwordstore/ui/settings/SettingsGraph.kt b/app/src/main/java/app/passwordstore/ui/settings/SettingsGraph.kt
index ae4e277b..44ae06d8 100644
--- a/app/src/main/java/app/passwordstore/ui/settings/SettingsGraph.kt
+++ b/app/src/main/java/app/passwordstore/ui/settings/SettingsGraph.kt
@@ -30,6 +30,9 @@ import kotlinx.serialization.Serializable
 /** The store's commit log. */
 @Serializable data object GitLogRoute
 
+/** Version, links, certificate and licenses. */
+@Serializable data object AboutRoute
+
 /** HTTP(S) proxy settings. */
 @Serializable data object ProxyRoute
 
@@ -44,9 +47,13 @@ fun NavGraphBuilder.settingsGraph(activity: MainActivity, nav: NavHostController
   composable<SettingsRoute> { entry ->
     SettingsScreen(
       onSection = { if (onTop(entry)) nav.navigate(SettingsSectionRoute(it)) },
+      onAbout = { if (onTop(entry)) nav.navigate(AboutRoute) },
       onBack = { close(entry) },
     )
   }
+  composable<AboutRoute> { entry ->
+    AboutDestination(activity = activity, onBack = { close(entry) })
+  }
   composable<SettingsSectionRoute> { entry ->
     SettingsSectionDestination(
       activity = activity,
diff --git a/app/src/main/java/app/passwordstore/ui/settings/SettingsScreen.kt b/app/src/main/java/app/passwordstore/ui/settings/SettingsScreen.kt
index d13d1cf5..14895017 100644
--- a/app/src/main/java/app/passwordstore/ui/settings/SettingsScreen.kt
+++ b/app/src/main/java/app/passwordstore/ui/settings/SettingsScreen.kt
@@ -17,6 +17,7 @@ import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.verticalScroll
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.automirrored.filled.ArrowBack
+import androidx.compose.material.icons.filled.Info
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
@@ -68,7 +69,7 @@ enum class SettingsAction {
 /** Top bar with [title] and back, then [content] in one grouped surface, scrolling. */
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
-private fun SettingsScaffold(
+internal fun SettingsScaffold(
   title: String,
   onBack: () -> Unit,
   modifier: Modifier = Modifier,
@@ -97,6 +98,7 @@ private fun SettingsScaffold(
 @Composable
 fun SettingsScreen(
   onSection: (SettingsSection) -> Unit,
+  onAbout: () -> Unit,
   onBack: () -> Unit,
   modifier: Modifier = Modifier,
 ) {
@@ -109,6 +111,12 @@ fun SettingsScreen(
         colors = rowColors(),
       )
     }
+    ListItem(
+      headlineContent = { Text(stringResource(R.string.about)) },
+      modifier = Modifier.clickable(role = Role.Button, onClick = onAbout),
+      leadingContent = { Icon(Icons.Filled.Info, contentDescription = null) },
+      colors = rowColors(),
+    )
   }
 }