feat(multi-account): add DesktopAccountStorage with AES-256-GCM encryption

Phase 2: encrypted persistence for multi-account metadata. - DesktopAccountStorage implements AccountStorage interface - AES-256-GCM encryption with random key stored in OS keychain - Jackson DTOs for flat serialization (no polymorphic complexity) - Migration helper from legacy single-account files - Atomic writes via temp file + rename - POSIX file permissions (owner-only read/write) - 11 unit tests covering roundtrip, encryption, deletion, migration Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-04-24 07:34:07 +03:00
parent aa33b7d271
commit 197db2361d
2 changed files with 477 additions and 0 deletions
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+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.desktop.account
+
+import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
+import com.fasterxml.jackson.module.kotlin.readValue
+import com.vitorpamplona.amethyst.commons.keystorage.SecureKeyStorage
+import com.vitorpamplona.amethyst.commons.model.account.AccountInfo
+import com.vitorpamplona.amethyst.commons.model.account.AccountStorage
+import com.vitorpamplona.amethyst.commons.model.account.SignerType
+import com.vitorpamplona.quartz.utils.Log
+import java.io.File
+import java.nio.file.Files
+import java.nio.file.attribute.PosixFilePermission
+import java.security.SecureRandom
+import java.util.Base64
+import javax.crypto.Cipher
+import javax.crypto.spec.GCMParameterSpec
+import javax.crypto.spec.SecretKeySpec
+
+/**
+ * Encrypted account metadata storage for Desktop.
+ *
+ * Architecture:
+ * - Account metadata (npub, signerType, active account) stored in encrypted JSON file
+ * - Private keys (nsecs) stored separately in SecureKeyStorage (OS keychain)
+ * - AES-256-GCM encryption key stored in OS keychain via SecureKeyStorage
+ *
+ * File: ~/.amethyst/accounts.json.enc
+ */
+class DesktopAccountStorage(
+    private val secureStorage: SecureKeyStorage,
+    private val homeDir: File = File(System.getProperty("user.home")),
+) : AccountStorage {
+    companion object {
+        private const val METADATA_KEY_ALIAS = "account-metadata-key"
+        private const val ACCOUNTS_FILE = "accounts.json.enc"
+        private const val AES_KEY_SIZE = 32 // 256 bits
+        private const val GCM_IV_SIZE = 12
+        private const val GCM_TAG_BITS = 128
+    }
+
+    private val mapper = jacksonObjectMapper()
+    private val amethystDir by lazy { File(homeDir, ".amethyst") }
+
+    // --- AccountStorage interface ---
+
+    override suspend fun loadAccounts(): List<AccountInfo> = readMetadata().accounts.map { it.toAccountInfo() }
+
+    override suspend fun saveAccount(info: AccountInfo) {
+        val metadata = readMetadata()
+        val dto = AccountInfoDto.from(info)
+        val updated = metadata.accounts.filter { it.npub != info.npub } + dto
+        writeMetadata(metadata.copy(accounts = updated))
+    }
+
+    override suspend fun deleteAccount(npub: String) {
+        val metadata = readMetadata()
+        val updated = metadata.accounts.filter { it.npub != npub }
+        val newActive =
+            if (metadata.activeNpub == npub) {
+                updated.firstOrNull()?.npub
+            } else {
+                metadata.activeNpub
+            }
+        writeMetadata(metadata.copy(accounts = updated, activeNpub = newActive))
+    }
+
+    override suspend fun currentAccount(): String? = readMetadata().activeNpub
+
+    override suspend fun setCurrentAccount(npub: String) {
+        val metadata = readMetadata()
+        writeMetadata(metadata.copy(activeNpub = npub))
+    }
+
+    // --- Migration from single-account files ---
+
+    suspend fun migrateFromLegacyFiles(accountManager: AccountManager): Boolean {
+        val prefsFile = File(amethystDir, "last_account.txt")
+        val bunkerFile = File(amethystDir, "bunker_uri.txt")
+
+        if (!prefsFile.exists() && !bunkerFile.exists()) return false
+        if (getAccountsFile().exists()) return false // already migrated
+
+        val npub =
+            prefsFile
+                .takeIf { it.exists() }
+                ?.readText()
+                ?.trim()
+                ?.takeIf { it.isNotEmpty() }
+                ?: return false
+
+        val bunkerUri =
+            bunkerFile
+                .takeIf { it.exists() }
+                ?.readText()
+                ?.trim()
+                ?.takeIf { it.isNotEmpty() }
+
+        val signerType =
+            if (bunkerUri != null) {
+                SignerType.Remote(bunkerUri)
+            } else {
+                val hasPrivKey = secureStorage.hasPrivateKey(npub)
+                if (hasPrivKey) SignerType.Internal else SignerType.ViewOnly
+            }
+
+        val info = AccountInfo(npub = npub, signerType = signerType)
+        val metadata = AccountMetadata(accounts = listOf(AccountInfoDto.from(info)), activeNpub = npub)
+        writeMetadata(metadata)
+
+        // Verify migration by reading back
+        val verified = readMetadata()
+        if (verified.accounts.any { it.npub == npub }) {
+            // Migration verified — rename old files
+            prefsFile.renameTo(File(amethystDir, "last_account.txt.bak"))
+            bunkerFile.takeIf { it.exists() }?.renameTo(File(amethystDir, "bunker_uri.txt.bak"))
+            Log.d("DesktopAccountStorage", "Migrated legacy account: $npub")
+            return true
+        }
+
+        return false
+    }
+
+    // --- Encrypted file I/O ---
+
+    private suspend fun readMetadata(): AccountMetadata {
+        val file = getAccountsFile()
+        if (!file.exists()) return AccountMetadata()
+
+        return try {
+            val encrypted = file.readBytes()
+            val decrypted = decrypt(encrypted)
+            mapper.readValue<AccountMetadata>(decrypted)
+        } catch (e: Exception) {
+            Log.e("DesktopAccountStorage", "Failed to read accounts metadata", e)
+            AccountMetadata()
+        }
+    }
+
+    private suspend fun writeMetadata(metadata: AccountMetadata) {
+        ensureDir()
+        val json = mapper.writeValueAsBytes(metadata)
+        val encrypted = encrypt(json)
+
+        // Atomic write via temp file
+        val file = getAccountsFile()
+        val temp = File(amethystDir, "${ACCOUNTS_FILE}.tmp")
+        temp.writeBytes(encrypted)
+        temp.renameTo(file)
+
+        setFilePermissions(file)
+    }
+
+    private fun getAccountsFile() = File(amethystDir, ACCOUNTS_FILE)
+
+    // --- AES-256-GCM encryption ---
+
+    private suspend fun getOrCreateKey(): ByteArray {
+        val existing = secureStorage.getPrivateKey(METADATA_KEY_ALIAS)
+        if (existing != null) return Base64.getDecoder().decode(existing)
+
+        val key = ByteArray(AES_KEY_SIZE).also { SecureRandom().nextBytes(it) }
+        secureStorage.savePrivateKey(METADATA_KEY_ALIAS, Base64.getEncoder().encodeToString(key))
+        return key
+    }
+
+    private suspend fun encrypt(data: ByteArray): ByteArray {
+        val key = getOrCreateKey()
+        val iv = ByteArray(GCM_IV_SIZE).also { SecureRandom().nextBytes(it) }
+        val cipher = Cipher.getInstance("AES/GCM/NoPadding")
+        cipher.init(Cipher.ENCRYPT_MODE, SecretKeySpec(key, "AES"), GCMParameterSpec(GCM_TAG_BITS, iv))
+        val ciphertext = cipher.doFinal(data)
+        // Prepend IV to ciphertext
+        return iv + ciphertext
+    }
+
+    private suspend fun decrypt(data: ByteArray): ByteArray {
+        val key = getOrCreateKey()
+        val iv = data.copyOfRange(0, GCM_IV_SIZE)
+        val ciphertext = data.copyOfRange(GCM_IV_SIZE, data.size)
+        val cipher = Cipher.getInstance("AES/GCM/NoPadding")
+        cipher.init(Cipher.DECRYPT_MODE, SecretKeySpec(key, "AES"), GCMParameterSpec(GCM_TAG_BITS, iv))
+        return cipher.doFinal(ciphertext)
+    }
+
+    // --- File system helpers ---
+
+    private fun ensureDir() {
+        if (!amethystDir.exists()) amethystDir.mkdirs()
+        try {
+            Files.setPosixFilePermissions(
+                amethystDir.toPath(),
+                setOf(
+                    PosixFilePermission.OWNER_READ,
+                    PosixFilePermission.OWNER_WRITE,
+                    PosixFilePermission.OWNER_EXECUTE,
+                ),
+            )
+        } catch (_: UnsupportedOperationException) {
+            // Windows
+        } catch (_: Exception) {
+        }
+    }
+
+    private fun setFilePermissions(file: File) {
+        try {
+            Files.setPosixFilePermissions(
+                file.toPath(),
+                setOf(PosixFilePermission.OWNER_READ, PosixFilePermission.OWNER_WRITE),
+            )
+        } catch (_: UnsupportedOperationException) {
+        } catch (_: Exception) {
+        }
+    }
+}
+
+/**
+ * Internal DTO for JSON serialization.
+ * Uses flat fields instead of polymorphic SignerType to keep serialization simple.
+ */
+internal data class AccountMetadata(
+    val accounts: List<AccountInfoDto> = emptyList(),
+    val activeNpub: String? = null,
+)
+
+internal data class AccountInfoDto(
+    val npub: String,
+    val signerKind: String, // "internal", "remote", "viewonly"
+    val bunkerUri: String? = null,
+    val isTransient: Boolean = false,
+) {
+    fun toAccountInfo(): AccountInfo =
+        AccountInfo(
+            npub = npub,
+            signerType =
+                when (signerKind) {
+                    "remote" -> SignerType.Remote(bunkerUri ?: "")
+                    "viewonly" -> SignerType.ViewOnly
+                    else -> SignerType.Internal
+                },
+            isTransient = isTransient,
+        )
+
+    companion object {
+        fun from(info: AccountInfo): AccountInfoDto =
+            AccountInfoDto(
+                npub = info.npub,
+                signerKind =
+                    when (info.signerType) {
+                        is SignerType.Internal -> "internal"
+                        is SignerType.Remote -> "remote"
+                        is SignerType.ViewOnly -> "viewonly"
+                    },
+                bunkerUri = (info.signerType as? SignerType.Remote)?.bunkerUri,
+                isTransient = info.isTransient,
+            )
+    }
+}