D4: history the user can carry — encrypted export and import
Same design as iOS: the vault's history re-sealed under a passphrase- derived key (PBKDF2 600k rounds, AES-256-GCM), saved through SAF, merged back by content identity so the same backup twice adds nothing. Expired stories stay expired — a backup is not a way back in. The passphrase is stored nowhere, deliberately. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Paul Hitt
co-authored by
Claude Opus 4.8
Claude Opus 4.8
parent
f1122777c1
commit
6a0f642e0d
@@ -660,6 +660,9 @@ fun ColumnScope.AccountScreen(
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SectionBand()
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SettingsSection { RegisteredDevicesSection(model, phase) }
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SectionBand()
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SettingsSection { HistoryBackupSection(model) }
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SectionBand()
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SettingsSection { AddressCard(fnid = phase.fnid, relay = phase.relay, handle = phase.handle) }
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@@ -0,0 +1,230 @@
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package io.flamenet.messenger.app
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import android.net.Uri
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import androidx.activity.compose.rememberLauncherForActivityResult
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import androidx.activity.result.contract.ActivityResultContracts
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import androidx.compose.foundation.layout.Row
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import androidx.compose.foundation.layout.Spacer
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import androidx.compose.foundation.layout.fillMaxWidth
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import androidx.compose.foundation.layout.height
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import androidx.compose.foundation.layout.width
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import androidx.compose.material3.AlertDialog
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import androidx.compose.material3.MaterialTheme
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import androidx.compose.material3.OutlinedButton
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import androidx.compose.material3.OutlinedTextField
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import androidx.compose.material3.Text
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import androidx.compose.material3.TextButton
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import androidx.compose.runtime.Composable
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import androidx.compose.runtime.getValue
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import androidx.compose.runtime.mutableStateOf
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import androidx.compose.runtime.remember
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import androidx.compose.runtime.rememberCoroutineScope
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import androidx.compose.runtime.setValue
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import androidx.compose.ui.Modifier
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import androidx.compose.ui.platform.LocalContext
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import androidx.compose.ui.platform.testTag
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import androidx.compose.ui.text.input.PasswordVisualTransformation
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import androidx.compose.ui.unit.sp
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import io.flamenet.e2e.HistoryExport
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import kotlinx.coroutines.launch
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import java.text.SimpleDateFormat
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import java.util.Date
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import java.util.Locale
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/**
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* Export and import of encrypted history backups (D4).
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*
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* The relay keeps no history, so a new phone starts empty — this is the
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* remedy, and the passphrase is deliberately the only key: the app stores
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* nothing that could open the file, so neither can anyone who takes the file.
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*/
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@Composable
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fun HistoryBackupSection(model: MessengerViewModel) {
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val context = LocalContext.current
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val scope = rememberCoroutineScope()
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var showExportDialog by remember { mutableStateOf(false) }
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var pendingExport by remember { mutableStateOf<ByteArray?>(null) }
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var pendingImport by remember { mutableStateOf<Uri?>(null) }
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var working by remember { mutableStateOf(false) }
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var status by remember { mutableStateOf<String?>(null) }
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val saveLauncher = rememberLauncherForActivityResult(
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ActivityResultContracts.CreateDocument("application/octet-stream")
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) { uri ->
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val bytes = pendingExport
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pendingExport = null
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if (uri == null || bytes == null) return@rememberLauncherForActivityResult
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status = runCatching {
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context.contentResolver.openOutputStream(uri)?.use { it.write(bytes) }
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?: error("nothing to write to")
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}.fold(
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onSuccess = { "Backup saved. Keep the passphrase — it is the only key." },
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onFailure = { "Couldn't write the file: ${it.message}" },
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)
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}
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val openLauncher = rememberLauncherForActivityResult(
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ActivityResultContracts.OpenDocument()
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) { uri -> if (uri != null) pendingImport = uri }
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Text("History backup", style = MaterialTheme.typography.titleMedium)
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Text(
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"Your history lives only on this phone — the server keeps none, so a "
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+ "new phone starts empty. An export is sealed with a passphrase you "
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+ "choose and can be imported on another Android phone signed into "
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+ "this account. Lose the passphrase and the backup cannot be "
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+ "opened, by anyone.",
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fontSize = 12.sp,
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color = Palette.SecondaryText,
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)
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Spacer(Modifier.height(Space.sm))
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Row {
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OutlinedButton(
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onClick = { showExportDialog = true },
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enabled = !working,
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modifier = Modifier.testTag("export-history"),
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) { Text("Export…") }
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Spacer(Modifier.width(Space.sm))
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OutlinedButton(
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// SAF filters on MIME, and a custom extension has none — offer
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// everything and let the crypto refuse what isn't a backup.
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onClick = { openLauncher.launch(arrayOf("*/*")) },
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enabled = !working,
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modifier = Modifier.testTag("import-history"),
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) { Text("Import…") }
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}
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status?.let {
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Spacer(Modifier.height(Space.xs))
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Text(it, fontSize = 12.sp, color = Palette.SecondaryText,
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modifier = Modifier.testTag("backup-status"))
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}
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if (showExportDialog) {
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PassphraseDialog(
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title = "Export history",
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explainer = "This passphrase is the only key to the backup. It isn't "
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+ "stored anywhere — a forgotten passphrase means the backup can "
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+ "never be opened.",
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requireRepeat = true,
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busy = working,
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onDismiss = { if (!working) showExportDialog = false },
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) { phrase ->
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working = true
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scope.launch {
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val bytes = model.exportHistory(phrase.toCharArray())
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working = false
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showExportDialog = false
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if (bytes == null) {
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status = "Sign in first."
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} else {
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pendingExport = bytes
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val stamp = SimpleDateFormat("yyyy-MM-dd", Locale.US).format(Date())
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saveLauncher.launch("flamenet-history-$stamp.${HistoryExport.FILE_EXTENSION}")
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}
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}
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}
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}
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pendingImport?.let { uri ->
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PassphraseDialog(
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title = "Import history",
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explainer = "Anything already on this phone stays — the backup is "
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+ "merged in, never a replacement.",
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requireRepeat = false,
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busy = working,
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onDismiss = { if (!working) pendingImport = null },
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) { phrase ->
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working = true
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scope.launch {
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val bytes = runCatching {
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context.contentResolver.openInputStream(uri)?.use { it.readBytes() }
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}.getOrNull()
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if (bytes == null) {
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working = false
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pendingImport = null
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status = "Couldn't read that file."
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return@launch
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}
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val outcome = model.importHistory(bytes, phrase.toCharArray())
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working = false
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pendingImport = null
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status = outcome.fold(
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onSuccess = { counts ->
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if (counts.messages + counts.stories == 0)
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"Backup opened — everything in it was already here."
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else
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"Imported ${counts.messages} message${if (counts.messages == 1) "" else "s"}" +
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" and ${counts.stories} " +
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if (counts.stories == 1) "story." else "stories."
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},
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onFailure = { it.message ?: "That backup couldn't be opened." },
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)
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}
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}
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}
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}
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@Composable
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private fun PassphraseDialog(
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title: String,
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explainer: String,
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requireRepeat: Boolean,
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busy: Boolean,
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onDismiss: () -> Unit,
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onConfirm: (String) -> Unit,
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) {
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var phrase by remember { mutableStateOf("") }
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var repeat by remember { mutableStateOf("") }
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val mismatch = requireRepeat && repeat.isNotEmpty() && repeat != phrase
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val ready = phrase.length >= 6 && (!requireRepeat || repeat == phrase)
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AlertDialog(
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onDismissRequest = onDismiss,
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title = { Text(title) },
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text = {
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androidx.compose.foundation.layout.Column {
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Text(explainer, fontSize = 12.sp, color = Palette.SecondaryText)
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Spacer(Modifier.height(Space.sm))
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OutlinedTextField(
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value = phrase,
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onValueChange = { phrase = it },
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placeholder = { Text("Passphrase", fontSize = 14.sp) },
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singleLine = true,
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visualTransformation = PasswordVisualTransformation(),
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modifier = Modifier.fillMaxWidth().testTag("backup-passphrase"),
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)
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if (requireRepeat) {
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Spacer(Modifier.height(Space.xs))
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OutlinedTextField(
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value = repeat,
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onValueChange = { repeat = it },
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placeholder = { Text("Repeat passphrase", fontSize = 14.sp) },
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singleLine = true,
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visualTransformation = PasswordVisualTransformation(),
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isError = mismatch,
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modifier = Modifier.fillMaxWidth().testTag("backup-passphrase-repeat"),
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)
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if (mismatch) {
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Text("The two passphrases don't match yet.",
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fontSize = 12.sp, color = MaterialTheme.colorScheme.error)
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}
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}
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if (phrase.isNotEmpty() && phrase.length < 6) {
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Text("Use at least 6 characters.",
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fontSize = 12.sp, color = Palette.SecondaryText)
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}
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}
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},
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confirmButton = {
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TextButton(
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onClick = { onConfirm(phrase) },
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enabled = ready && !busy,
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modifier = Modifier.testTag("backup-confirm"),
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) { Text(if (busy) "Working…" else "Continue") }
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},
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dismissButton = {
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TextButton(onClick = onDismiss, enabled = !busy) { Text("Cancel") }
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},
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)
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}
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@@ -12,6 +12,7 @@ import io.flamenet.e2e.AccountKdf
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import io.flamenet.e2e.DeviceIdentity
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import io.flamenet.e2e.Ed25519
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import io.flamenet.e2e.FNID
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import io.flamenet.e2e.HistoryExport
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import io.flamenet.e2e.Vault
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import kotlinx.coroutines.Dispatchers
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import io.flamenet.client.IdentityTrust
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@@ -1251,6 +1252,31 @@ class MessengerViewModel(app: Application) : AndroidViewModel(app) {
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}
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}
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// -- History backup (D4) -------------------------------------------------
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/**
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* The vault's history, sealed under a passphrase the user chose.
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*
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* Off the main thread on purpose: the KDF runs 600k rounds, which is the
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* point of it, and would freeze the UI for a visible beat.
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*/
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suspend fun exportHistory(passphrase: CharArray): ByteArray? =
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withContext(Dispatchers.Default) {
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vault?.let { HistoryExport.seal(it.exportPayload(), passphrase) }
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}
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/** Merge a backup file in. Returns how much of it was actually new. */
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suspend fun importHistory(bytes: ByteArray, passphrase: CharArray): Result<Vault.ImportCounts> =
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withContext(Dispatchers.Default) {
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val v = vault
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?: return@withContext Result.failure(IllegalStateException("Sign in first."))
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runCatching {
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v.mergeImportedPayload(
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HistoryExport.open(bytes, passphrase),
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nowSeconds = System.currentTimeMillis() / 1000.0)
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}
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}
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// -- Stories (§6.6) ------------------------------------------------------
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fun refreshStories() = viewModelScope.launch {
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Reference in New Issue
Block a user