feat(app): add the setup model and stricter key checks

URL checks and fixes, authentication modes per URL, the clone target,
the store's recipients, a size- and symlink-checked .gpg-id read and
the .gpg-id text for a new store (uppercase long key IDs), as pure
functions for the Compose setup screens. The SSH key import now also
requires a format sshj recognizes (an OpenPGP private key block
matched the old marker check and was imported as the SSH key) and no
longer crashes on an empty size cursor. KeyUtils tells secret keys
apart and no longer throws on a key without user ID.

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

2 files changed, 127 insertions, 10 deletions

diff --git a/app/src/main/java/app/passwordstore/ui/setup/SetupModel.kt b/app/src/main/java/app/passwordstore/ui/setup/SetupModel.kt
new file mode 100644
index 00000000..8c7b20a1
--- /dev/null
+++ b/app/src/main/java/app/passwordstore/ui/setup/SetupModel.kt
@@ -0,0 +1,102 @@
+/*
+ * Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package app.passwordstore.ui.setup
+
+import app.passwordstore.crypto.PGPIdentifier
+import app.passwordstore.util.settings.AuthMode
+import java.io.File
+import java.io.IOException
+import java.nio.file.Files
+import java.nio.file.LinkOption
+import java.util.Locale
+
+/** Why a repository URL is questioned before it is saved, as the old server screen checked it. */
+enum class UrlProblem {
+  /** An HTTPS URL with a custom port, which the old screen did not support. */
+  HttpsPort,
+  /** An scp-style SSH URL with a port: without `ssh://` the port is read as part of the path. */
+  SshScheme,
+  /** The unencrypted `git://` protocol. */
+  GitScheme,
+}
+
+private val PORT = ":[0-9]{1,5}/".toRegex()
+
+private fun isHttp(url: String) = url.startsWith("http://") || url.startsWith("https://")
+
+/** What is wrong with [url], or null. `git://` is checked first: a port does not make it SSH. */
+fun urlProblem(url: String): UrlProblem? =
+  when {
+    url.startsWith("git://") -> UrlProblem.GitScheme
+    !url.contains(PORT) -> null
+    url.startsWith("https://") -> UrlProblem.HttpsPort
+    url.startsWith("http://") || url.startsWith("ssh://") -> null
+    else -> UrlProblem.SshScheme
+  }
+
+/** The old screen's fix for [problem] in [url], or null when there is none (`git://`). */
+fun fixUrl(url: String, problem: UrlProblem): String? =
+  when (problem) {
+    UrlProblem.HttpsPort -> url.replace(PORT, "/")
+    UrlProblem.SshScheme -> "ssh://$url"
+    UrlProblem.GitScheme -> null
+  }
+
+/** The authentication modes offered for [url], the default first. */
+fun authModes(url: String): List<AuthMode> =
+  if (isHttp(url)) listOf(AuthMode.None, AuthMode.Password)
+  else listOf(AuthMode.SshKey, AuthMode.Password)
+
+/** [current] when [url] still allows it, the default for [url] otherwise. */
+fun fitAuthMode(url: String, current: AuthMode): AuthMode =
+  authModes(url).let { modes -> if (current in modes) current else modes.first() }
+
+/** What a clone into the store folder finds there. */
+enum class CloneTarget {
+  /** Missing or empty. */
+  Empty,
+  /** Only a `.git` folder, from a store created and abandoned: deleted without asking. */
+  OnlyGit,
+  /** Anything else: deleted after a confirmation. */
+  Occupied,
+}
+
+fun cloneTarget(dir: File): CloneTarget {
+  val files = dir.listFiles().orEmpty()
+  return when {
+    files.isEmpty() -> CloneTarget.Empty
+    files.size == 1 && files[0].name == ".git" -> CloneTarget.OnlyGit
+    else -> CloneTarget.Occupied
+  }
+}
+
+/** The recipients named by a `.gpg-id` file's [text]; blank and unparsable lines are skipped. */
+fun storeRecipients(text: String): List<PGPIdentifier> =
+  text.lines().map(String::trim).filter(String::isNotEmpty).mapNotNull(PGPIdentifier::fromString)
+
+/**
+ * A `.gpg-id` naming [keys]: each 16-hex long key ID in uppercase on a line of its own, the format
+ * of a desktop store made with `pass init <key ID>`.
+ */
+fun gpgIdText(keys: List<PGPIdentifier.KeyId>): String =
+  keys.joinToString("") { "${it.toString().uppercase(Locale.ROOT)}\n" }
+
+private const val MAX_GPG_ID_BYTES = 64 * 1024
+
+/**
+ * The text of [dir]'s `.gpg-id`, or null when it is missing, not a regular file, a symlink, larger
+ * than 64 KiB or unreadable. Blocking: call it off the main thread.
+ */
+fun readGpgId(dir: File): String? {
+  val file = File(dir, ".gpg-id")
+  val path = file.toPath()
+  return try {
+    if (!Files.isRegularFile(path, LinkOption.NOFOLLOW_LINKS)) null
+    else if (Files.size(path) > MAX_GPG_ID_BYTES) null else file.readText()
+  } catch (_: IOException) {
+    null
+  }
+}
diff --git a/app/src/main/java/app/passwordstore/util/git/sshj/SshKey.kt b/app/src/main/java/app/passwordstore/util/git/sshj/SshKey.kt
index 109e36c9..8d5519a8 100644
--- a/app/src/main/java/app/passwordstore/util/git/sshj/SshKey.kt
+++ b/app/src/main/java/app/passwordstore/util/git/sshj/SshKey.kt
@@ -46,7 +46,9 @@ import net.schmizz.sshj.SSHClient
 import net.schmizz.sshj.common.Buffer
 import net.schmizz.sshj.common.Ed25519KeyFactory
 import net.schmizz.sshj.common.KeyType
+import net.schmizz.sshj.userauth.keyprovider.KeyFormat
 import net.schmizz.sshj.userauth.keyprovider.KeyProvider
+import net.schmizz.sshj.userauth.keyprovider.KeyProviderUtil
 import org.bouncycastle.crypto.params.Ed25519PrivateKeyParameters
 
 private const val PROVIDER_ANDROID_KEY_STORE = "AndroidKeyStore"
@@ -82,6 +84,25 @@ internal fun ed25519KeyPair(seed: ByteArray) =
     Ed25519KeyFactory.getPrivateKey(seed),
   )
 
+/**
+ * True when [lines] look like an SSH private key sshj can load: private key markers on the first
+ * and last line, in a format sshj recognizes. An OpenPGP private key block has the same markers and
+ * is refused by the format check.
+ */
+internal fun isSshPrivateKey(lines: List<String>): Boolean {
+  if (
+    lines.size < 2 ||
+      !Regex("BEGIN .* PRIVATE KEY").containsMatchIn(lines.first()) ||
+      !Regex("END .* PRIVATE KEY").containsMatchIn(lines.last())
+  )
+    return false
+  return try {
+    KeyProviderUtil.detectKeyFileFormat(lines.joinToString("\n"), false) != KeyFormat.Unknown
+  } catch (_: IOException) {
+    false
+  }
+}
+
 object SshKey {
 
   val sshPublicKey
@@ -198,9 +219,8 @@ object SshKey {
     val fileSize =
       context.contentResolver.query(uri, arrayOf(OpenableColumns.SIZE), null, null, null)?.use {
         cursor ->
-        // Cursor returns only a single row.
-        cursor.moveToFirst()
-        cursor.getInt(0)
+        // A single row; none when the provider cannot tell: the IOException below.
+        if (cursor.moveToFirst()) cursor.getInt(0) else null
       } ?: throw IOException(context.getString(R.string.ssh_key_does_not_exist))
 
     // We assume that an SSH key's ideal size is > 0 bytes && < 100 kilobytes.
@@ -214,13 +234,8 @@ object SshKey {
         ?: throw IOException(context.getString(R.string.ssh_key_does_not_exist))
     val lines = sshKeyInputStream.use { `is` -> `is`.bufferedReader().readLines() }
 
-    // The file must have more than 2 lines, and the first and last line must have private key
-    // markers.
-    if (
-      lines.size < 2 ||
-        !Regex("BEGIN .* PRIVATE KEY").containsMatchIn(lines.first()) ||
-        !Regex("END .* PRIVATE KEY").containsMatchIn(lines.last())
-    )
+    // Private key markers and a format sshj can read; the current key stays when this fails.
+    if (!isSshPrivateKey(lines))
       throw IllegalArgumentException(
         context.getString(R.string.ssh_key_import_error_not_an_ssh_key_message)
       )