DeviceManifestSupport.kt

1package com.peachpasswords.sync23import kotlinx.serialization.builtins.serializer4import kotlinx.serialization.json.Json5import org.bouncycastle.crypto.params.Ed25519PrivateKeyParameters67/** 0x03 adds relay routing to each introduced peer edge. */8const val DEVICE_MANIFEST_VERSION = 0x039private const val DEVICE_MANIFEST_FRESHNESS_MS = 5 * 60_000L10/**11 * Upper bounds on what verifyDeviceManifest will accept. A pathological peer12 * could otherwise craft a manifest that consumes unbounded memory or skips13 * sanity checks (e.g. `issuedAt = Long.MIN_VALUE` bypasses `abs(...) > window`14 * because `abs(Long.MIN_VALUE)` is still negative). These caps match the15 * realistic limits of the pairing protocol: a handful of paired devices, a16 * bounded revocation list, and string fields long enough for any honest use.17 */18private const val MAX_MANIFEST_DEVICES = 25619private const val MAX_MANIFEST_REVOCATIONS = 50020private const val MAX_MANIFEST_STRING = 25621internal const val NO_KEY_SENTINEL = "0000000000000000000000000000000000000000000000000000000000000000"2223interface PairedDeviceRegistry {24    fun getAll(): List<PairedDevice>25    fun get(id: String): PairedDevice?26    fun getByPubkey(pubkeyHex: String): PairedDevice? =27        getAll().firstOrNull {28            it.longTermPublicKeyHex?.let { key -> CryptoCompare.hex(key, pubkeyHex) } == true29        }30    fun upsert(device: PairedDevice)31    fun remove(deviceId: String) {}32    fun listRevocations(): List<DeviceRevocation> = emptyList()3334    /** Returns the ids that were not already revoked. */35    fun mergeRevocations(incoming: List<DeviceRevocation>): List<String> = emptyList()3637    /**38     * True when either the id or the long-term key is under a terminal39     * revocation. `deviceId` is a self-asserted string in a manifest, so40     * keying terminality on it alone is bypassed by re-vouching a revoked41     * device's key under a fresh id. The key is what a revoked device still42     * holds, so it is what terminality has to follow. `0`×64 is the "no key was43     * ever stored" sentinel (see PairedDeviceStore.revoke) and matches nothing.44     */45    fun isRevoked(deviceId: String, longTermPublicKeyHex: String? = null): Boolean {46        val key = longTermPublicKeyHex?.lowercase()?.takeIf { it != NO_KEY_SENTINEL }47        return listRevocations().any {48            it.deviceId == deviceId || (key != null && it.longTermPublicKeyHex.lowercase() == key)49        }50    }5152    /** Only a direct, SAS-confirmed re-pair may lift a terminal revocation. */53    fun clearRevocation(deviceId: String) {}54}5556fun buildSignedDeviceManifest(57    issuerDeviceId: String,58    devices: List<ManifestDeviceEntry>,59    signingPrivateKey: Ed25519PrivateKeyParameters,60    nowMs: Long = System.currentTimeMillis(),61    revoked: List<DeviceRevocation> = emptyList(),62): SignedDeviceManifest {63    require(issuerDeviceId.isNotBlank()) { "issuerDeviceId is required" }64    val body = DeviceManifestBody(65        manifestVersion = DEVICE_MANIFEST_VERSION,66        issuerDeviceId = issuerDeviceId,67        issuedAt = nowMs,68        // Normalise valid entries but keep invalid ones too — verifyDeviceManifest69        // is the gate that detects malformed input (M-09: silent drop would let70        // a caller believe they sent a valid manifest).71        devices = devices.map { normaliseManifestEntry(it) ?: it },72        revoked = revoked.map(::normaliseRevocation),73    )74    val signature = signEd25519(signingPrivateKey, canonicalDeviceManifestBody(body).toByteArray(Charsets.UTF_8))75    return SignedDeviceManifest(body, pubkeyToHex(signature))76}7778fun verifyDeviceManifest(79    manifest: SignedDeviceManifest,80    issuerSigningPublicKey: ByteArray,81    nowMs: Long = System.currentTimeMillis(),82    freshnessMs: Long = DEVICE_MANIFEST_FRESHNESS_MS,83): DeviceManifestBody? {84    val body = manifest.body85    if (body.manifestVersion != DEVICE_MANIFEST_VERSION) return null86    // Two-sided bounds — avoids `abs(...) > window`, which overflows for87    // `Long.MIN_VALUE` and lets a peer-presented timestamp bypass the88    // freshness gate. Reject negative `issuedAt` outright so the bounds89    // arithmetic can't be steered into a wrap-around by the manifest.90    if (body.issuedAt < 0L) return null91    if (body.issuedAt < nowMs - freshnessMs || body.issuedAt > nowMs + freshnessMs) return null92    if (body.issuerDeviceId.isBlank() || body.issuerDeviceId.length > MAX_MANIFEST_STRING) return null93    if (body.devices.size > MAX_MANIFEST_DEVICES) return null94    if (body.revoked.size > MAX_MANIFEST_REVOCATIONS) return null95    if (!isHex(manifest.signatureHex, 128)) return null96    if (!body.devices.all { normaliseManifestEntry(it) != null }) return null97    if (!body.revoked.all { isValidRevocation(it) }) return null98    val signature = runCatching { hexToBytes(manifest.signatureHex) }.getOrNull() ?: return null99    val canonical = canonicalDeviceManifestBody(body).toByteArray(Charsets.UTF_8)100    if (!verifyEd25519(issuerSigningPublicKey, canonical, signature)) return null101    return body102}103104fun canonicalDeviceManifestBody(body: DeviceManifestBody): String =105    canonicalise(106        mapOf(107            "devices" to body.devices.map { manifestEntryMap(it) },108            "issuedAt" to body.issuedAt,109            "issuerDeviceId" to body.issuerDeviceId,110            "manifestVersion" to body.manifestVersion,111            "revoked" to body.revoked.map { revocationMap(it) },112        ),113    )114115fun PairedDevice.toManifestEntry(): ManifestDeviceEntry? {116    val id = deviceId.takeIf { it.isNotBlank() } ?: return null117    val name = deviceName?.takeIf { it.isNotBlank() } ?: return null118    val type = deviceType?.takeIf { it in setOf("extension", "android", "ios") } ?: return null119    val longTerm = longTermPublicKeyHex?.lowercase()?.takeIf { isHex(it, 64) } ?: return null120    val signing = signingPublicKeyHex?.lowercase()?.takeIf { isHex(it, 64) } ?: return null121    return ManifestDeviceEntry(122        deviceId = id,123        deviceName = name,124        deviceType = type,125        longTermPublicKeyHex = longTerm,126        signingPublicKeyHex = signing,127        wsPort = wsPort,128        relayUrl = relayUrl,129        pairedAt = pairedAt,130    )131}132133private fun normaliseManifestEntry(entry: ManifestDeviceEntry): ManifestDeviceEntry? {134    if (entry.deviceId.isBlank() || entry.deviceName.isBlank()) return null135    // Bound string fields — a peer could otherwise send multi-megabyte strings136    // that pass the format checks and bloat the canonical signature input.137    if (entry.deviceId.length > MAX_MANIFEST_STRING || entry.deviceName.length > MAX_MANIFEST_STRING) return null138    if (entry.deviceType !in setOf("extension", "android", "ios")) return null139    if (!isHex(entry.longTermPublicKeyHex, 64) || !isHex(entry.signingPublicKeyHex, 64)) return null140    if (entry.wsPort != null && entry.wsPort !in 1..65_535) return null141    if (entry.pairedAt < 0L) return null142    if (143        entry.relayUrl != null && (144            entry.relayUrl.length > MAX_MANIFEST_STRING ||145            runCatching { Rendezvous.normalizeRelayUrl(entry.relayUrl) }.isFailure146        )147    ) return null148    return entry.copy(149        longTermPublicKeyHex = entry.longTermPublicKeyHex.lowercase(),150        signingPublicKeyHex = entry.signingPublicKeyHex.lowercase(),151    )152}153154private fun normaliseRevocation(r: DeviceRevocation): DeviceRevocation =155    r.copy(longTermPublicKeyHex = r.longTermPublicKeyHex.lowercase())156157private fun isValidRevocation(r: DeviceRevocation): Boolean =158    r.deviceId.isNotBlank() && r.deviceId.length <= MAX_MANIFEST_STRING &&159        isHex(r.longTermPublicKeyHex.lowercase(), 64) &&160        r.revokedByDeviceId.isNotBlank() && r.revokedByDeviceId.length <= MAX_MANIFEST_STRING &&161        r.revokedAt >= 0L162163private fun revocationMap(r: DeviceRevocation): Map<String, Any> = linkedMapOf(164    "deviceId" to r.deviceId,165    "longTermPublicKeyHex" to r.longTermPublicKeyHex.lowercase(),166    "revokedAt" to r.revokedAt,167    "revokedByDeviceId" to r.revokedByDeviceId,168)169170private fun manifestEntryMap(entry: ManifestDeviceEntry): Map<String, Any> {171    val normalised = normaliseManifestEntry(entry) ?: entry172    val map = linkedMapOf<String, Any>(173        "deviceId" to normalised.deviceId,174        "deviceName" to normalised.deviceName,175        "deviceType" to normalised.deviceType,176        "longTermPublicKeyHex" to normalised.longTermPublicKeyHex.lowercase(),177        "pairedAt" to normalised.pairedAt,178        "signingPublicKeyHex" to normalised.signingPublicKeyHex.lowercase(),179    )180    normalised.wsPort?.let { map["wsPort"] = it }181    normalised.relayUrl?.let { map["relayUrl"] = it }182    return map183}184185private fun canonicalise(value: Any?): String = when (value) {186    null -> "null"187    is Number -> {188        val d = value.toDouble()189        require(d.isFinite()) { "non-finite number" }190        if (d % 1.0 == 0.0) value.toLong().toString() else value.toString()191    }192    is String -> Json.encodeToString(String.serializer(), value)193    is Boolean -> if (value) "true" else "false"194    is List<*> -> value.joinToString(prefix = "[", postfix = "]", separator = ",") { canonicalise(it) }195    is Map<*, *> -> value.entries196        .map { (k, v) -> k.toString() to v }197        .sortedBy { it.first }198        .joinToString(prefix = "{", postfix = "}", separator = ",") { (k, v) ->199            Json.encodeToString(String.serializer(), k) + ":" + canonicalise(v)200        }201    else -> error("cannot canonicalise ${value::class.simpleName}")202}203204private fun isHex(value: String, length: Int): Boolean =205    value.length == length && value.all { it in '0'..'9' || it in 'a'..'f' }