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README.md

@@ -19,9 +19,15 @@ umn status
 umn address
 ```
 
-The installer builds locally, asks for administrator authorization once, installs a minimal root LaunchDaemon for `utun` and `/128` route management, installs the scoped `.mesh` resolver, then starts `umnd` as a per-user LaunchAgent. Peer networking, keys, packet parsing, firewall state, and DNS remain in the unprivileged daemon. If prompted, allow local-network access. Identity and configuration live in `~/Library/Application Support/UltraMesh`.
+The installer builds locally, asks for administrator authorization once, installs a minimal root LaunchDaemon for `utun` and `/128` route management, installs the scoped `.mesh` resolver, then starts `umnd` as a per-user LaunchAgent. Peer networking, keys, packet parsing, firewall state, and DNS remain in the unprivileged daemon. If prompted, allow local-network access. All persistent state lives in `~/Library/Application Support/UltraMesh`. The cryptographic identity in `identity.plist` determines the machine's mesh IPv6, and the same value is recorded as plain text in `address`; both files are mode `0600`.
 
-Use `./scripts/uninstall.sh` to remove both daemons, the interface/routes, binaries, and installer-managed resolver. It deliberately preserves identity, aliases, and firewall configuration so reinstalling keeps the same mesh address.
+Use `./scripts/uninstall.sh` to remove both daemons, the interface/routes, binaries, and installer-managed resolver. It deliberately preserves the entire state directory so reinstalling keeps the same mesh address. Do not edit or separately replace `identity.plist` or `address`: if either is corrupt, missing from an established identity/address pair, or mismatched, startup fails instead of silently assigning a new address.
+
+To verify the persistent address after installation or a restart:
+
+```sh
+test "$(umn address)" = "$(tr -d '[:space:]' < "$HOME/Library/Application Support/UltraMesh/address")"
+```
 
 ## Native IPv6
 
@@ -96,6 +102,7 @@ HTTPS is passed through unchanged. The web server remains responsible for its TL
 ## Design and current limits
 
 - Bonjour and Network.framework discover peers over infrastructure and Apple peer-to-peer Wi-Fi (`includePeerToPeer`). New routes recover automatically when an access-point path disappears while Wi-Fi remains enabled.
+- The local mesh IPv6 is derived only from the persistent signing identity. Wi-Fi path changes, peer-to-peer fallback, route updates, `utun` recreation, reboots, and reinstalls do not select or alter it.
 - Signed link-state announcements and shortest-hop routing support multi-hop topologies. The implementation is bounded and tested for 32 live nodes and 16 hops.
 - Service payloads are authenticated and encrypted end-to-end with Curve25519, HKDF-SHA256, and ChaCha20-Poly1305. Relays see routing metadata but cannot read ports or content.
 - Streams use sequence numbers, acknowledgements, retransmission, and a 60-second recovery window. An active stream can continue after a route change if another path appears within that window.

Sources/UltraMeshCore/Crypto.swift

@@ -1,7 +1,14 @@
 import Foundation
 import CryptoKit
+import Darwin
 
 public final class NodeIdentity: @unchecked Sendable {
+    private struct StoredIdentity: Codable {
+        let version: Int
+        let signing: Data
+        let agreement: Data
+    }
+
     public static let currentVersion = 1
     public let signingKey: Curve25519.Signing.PrivateKey
     public let agreementKey: Curve25519.KeyAgreement.PrivateKey
@@ -16,23 +23,161 @@ public final class NodeIdentity: @unchecked Sendable {
                                  agreementPublicKey: agreementKey.publicKey.rawRepresentation)
     }
 
+    private static func writeAtomicallyWithoutReplacing(_ data: Data, to url: URL) throws {
+        let temporaryURL = url.deletingLastPathComponent()
+            .appendingPathComponent(".\(url.lastPathComponent).\(UUID().uuidString).tmp")
+        let descriptor = Darwin.open(temporaryURL.path, O_WRONLY | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR)
+        guard descriptor >= 0 else { throw POSIXError(.init(rawValue: errno) ?? .EIO) }
+        defer {
+            Darwin.close(descriptor)
+            Darwin.unlink(temporaryURL.path)
+        }
+        try data.withUnsafeBytes { bytes in
+            guard let base = bytes.baseAddress else { return }
+            var offset = 0
+            while offset < data.count {
+                let written = Darwin.write(descriptor, base.advanced(by: offset), data.count - offset)
+                if written < 0 {
+                    if errno == EINTR { continue }
+                    throw POSIXError(.init(rawValue: errno) ?? .EIO)
+                }
+                offset += written
+            }
+        }
+        guard Darwin.fsync(descriptor) == 0 else { throw POSIXError(.init(rawValue: errno) ?? .EIO) }
+        // A hard link publishes the fully-written same-filesystem temporary file in
+        // one operation and fails with EEXIST instead of replacing existing state.
+        guard Darwin.link(temporaryURL.path, url.path) == 0 else {
+            throw POSIXError(.init(rawValue: errno) ?? .EIO)
+        }
+    }
+
+    private static func itemExists(at url: URL) throws -> Bool {
+        var status = stat()
+        if Darwin.lstat(url.path, &status) == 0 { return true }
+        let code = errno
+        if code == ENOENT || code == ENOTDIR { return false }
+        throw POSIXError(.init(rawValue: code) ?? .EIO)
+    }
+
     public static func loadOrCreate(at url: URL) throws -> NodeIdentity {
-        struct Stored: Codable { let version: Int; let signing: Data; let agreement: Data }
+        let fileManager = FileManager.default
-        let decoder = PropertyListDecoder()
+
-        if let data = try? Data(contentsOf: url) {
+        func load() throws -> NodeIdentity {
-            let value = try decoder.decode(Stored.self, from: data)
+            let data: Data
-            guard value.version == currentVersion else { throw UMNError.invalidIdentity }
+            do {
+                data = try Data(contentsOf: url)
+            } catch {
+                throw UMNError.message("Cannot read the UltraMesh identity at \(url.path). Restore access to this file; it was not replaced.")
+            }
+            let value: StoredIdentity
+            do {
+                value = try PropertyListDecoder().decode(StoredIdentity.self, from: data)
+            } catch {
+                throw UMNError.message("The UltraMesh identity at \(url.path) is corrupt. Restore it from backup or explicitly reset UltraMesh state; it was not replaced.")
+            }
+            guard value.version == currentVersion else {
+                throw UMNError.message("The UltraMesh identity at \(url.path) uses unsupported version \(value.version). Upgrade UltraMesh or restore a compatible identity; it was not replaced.")
+            }
+            do {
                 return try NodeIdentity(signingKey: .init(rawRepresentation: value.signing),
                                         agreementKey: .init(rawRepresentation: value.agreement))
+            } catch {
+                throw UMNError.message("The UltraMesh identity at \(url.path) contains invalid cryptographic keys. Restore it from backup or explicitly reset UltraMesh state; it was not replaced.")
             }
+        }
+
+        let exists: Bool
+        do {
+            exists = try itemExists(at: url)
+        } catch {
+            throw UMNError.message("Cannot inspect the UltraMesh identity path at \(url.path): \(error.localizedDescription). No new identity was created.")
+        }
+        if exists { return try load() }
+
         let identity = try NodeIdentity()
-        try FileManager.default.createDirectory(at: url.deletingLastPathComponent(), withIntermediateDirectories: true)
+        do {
+            try fileManager.createDirectory(at: url.deletingLastPathComponent(), withIntermediateDirectories: true)
+        } catch {
+            throw UMNError.message("Cannot create the UltraMesh state directory at \(url.deletingLastPathComponent().path): \(error.localizedDescription)")
+        }
         let encoder = PropertyListEncoder(); encoder.outputFormat = .binary
-        let data = try encoder.encode(Stored(version: currentVersion,
+        let data = try encoder.encode(StoredIdentity(version: currentVersion,
                                                      signing: identity.signingKey.rawRepresentation,
                                                      agreement: identity.agreementKey.rawRepresentation))
-        try data.write(to: url, options: .atomic)
+        do {
-        try FileManager.default.setAttributes([.posixPermissions: 0o600], ofItemAtPath: url.path)
+            try writeAtomicallyWithoutReplacing(data, to: url)
+        } catch {
+            // Another daemon may have won the first-run race. Its complete identity is
+            // authoritative; never overwrite it with the identity generated above.
+            if (try? itemExists(at: url)) == true { return try load() }
+            throw UMNError.message("Cannot create the UltraMesh identity at \(url.path): \(error.localizedDescription)")
+        }
+        do {
+            try fileManager.setAttributes([.posixPermissions: 0o600], ofItemAtPath: url.path)
+        } catch {
+            throw UMNError.message("The UltraMesh identity was created at \(url.path), but its permissions could not be restricted to 0600: \(error.localizedDescription)")
+        }
+        return identity
+    }
+
+    /// Loads the persistent identity in a state directory and creates or verifies
+    /// its derived, human-readable address sidecar.
+    public static func loadOrCreate(in directory: URL) throws -> NodeIdentity {
+        let fileManager = FileManager.default
+        let identityURL = directory.appendingPathComponent("identity.plist")
+        let addressURL = directory.appendingPathComponent("address")
+        let identityExists: Bool
+        let addressExists: Bool
+        do {
+            identityExists = try itemExists(at: identityURL)
+            addressExists = try itemExists(at: addressURL)
+        } catch {
+            throw UMNError.message("Cannot inspect UltraMesh state in \(directory.path): \(error.localizedDescription). No state was changed.")
+        }
+
+        guard identityExists || !addressExists else {
+            throw UMNError.message("Found \(addressURL.path) without \(identityURL.path). Restore the matching identity or explicitly reset UltraMesh state; no new identity was created.")
+        }
+
+        let identity = try loadOrCreate(at: identityURL)
+
+        func verifyAddress() throws {
+            let data: Data
+            do {
+                data = try Data(contentsOf: addressURL)
+            } catch {
+                throw UMNError.message("Cannot read the stored UltraMesh address at \(addressURL.path). Restore access to this file; it was not replaced.")
+            }
+            guard let stored = String(data: data, encoding: .utf8) else {
+                throw UMNError.message("The stored UltraMesh address at \(addressURL.path) is not UTF-8 text. Restore the matching record or explicitly reset UltraMesh state; it was not replaced.")
+            }
+            let text = stored.trimmingCharacters(in: .whitespacesAndNewlines)
+            guard let address = try? MeshAddress(text), address == identity.record.address else {
+                throw UMNError.message("The stored UltraMesh address at \(addressURL.path) does not match the persistent identity. Restore the matching identity/address pair or explicitly reset UltraMesh state; neither file was replaced.")
+            }
+        }
+
+        if addressExists {
+            try verifyAddress()
+        } else {
+            let data = Data("\(identity.record.address)\n".utf8)
+            do {
+                try writeAtomicallyWithoutReplacing(data, to: addressURL)
+            } catch {
+                // As with identity creation, tolerate only a concurrent complete write.
+                if (try? itemExists(at: addressURL)) == true { try verifyAddress() }
+                else {
+                    throw UMNError.message("Cannot create the stored UltraMesh address at \(addressURL.path): \(error.localizedDescription)")
+                }
+            }
+        }
+
+        do {
+            try fileManager.setAttributes([.posixPermissions: 0o600], ofItemAtPath: addressURL.path)
+        } catch {
+            throw UMNError.message("Cannot restrict the stored UltraMesh address at \(addressURL.path) to mode 0600: \(error.localizedDescription)")
+        }
         return identity
     }
 

Sources/umn-selftest/main.swift

@@ -14,6 +14,14 @@ func check(_ condition: @autoclosure () throws -> Bool, _ name: String) throws {
     passed += 1; print("ok \(passed) - \(name)")
 }
 
+func rejects(_ name: String, _ operation: () throws -> Void) throws {
+    do { try operation() } catch {
+        passed += 1; print("ok \(passed) - \(name)")
+        return
+    }
+    throw TestFailure(name)
+}
+
 func ipv6Packet(source: MeshAddress, destination: MeshAddress, next: UInt8, payload: Data) -> Data {
     var packet = Data(repeating: 0, count: 40)
     packet[0] = 0x60; packet[4] = UInt8(payload.count >> 8); packet[5] = UInt8(payload.count & 255)
@@ -47,11 +55,84 @@ do {
     let directory = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString)
     defer { try? FileManager.default.removeItem(at: directory) }
     let identityURL = directory.appendingPathComponent("identity.plist")
-    let stored1 = try NodeIdentity.loadOrCreate(at: identityURL)
+    let addressURL = directory.appendingPathComponent("address")
-    let stored2 = try NodeIdentity.loadOrCreate(at: identityURL)
+    let stored1 = try NodeIdentity.loadOrCreate(in: directory)
-    try check(stored1.record == stored2.record, "identity persists")
+    let stored2 = try NodeIdentity.loadOrCreate(in: directory)
+    try check(stored1.record == stored2.record, "identity and address persist across daemon-style reloads")
     let attributes = try FileManager.default.attributesOfItem(atPath: identityURL.path)
     try check((attributes[.posixPermissions] as? NSNumber)?.intValue == 0o600, "identity permissions")
+    let addressAttributes = try FileManager.default.attributesOfItem(atPath: addressURL.path)
+    try check((addressAttributes[.posixPermissions] as? NSNumber)?.intValue == 0o600, "address permissions")
+    let storedAddressText = try String(contentsOf: addressURL, encoding: .utf8)
+        .trimmingCharacters(in: .whitespacesAndNewlines)
+    try check(try MeshAddress(storedAddressText) == stored1.record.address, "stored address is valid IPv6 matching identity")
+
+    let legacyDirectory = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString)
+    defer { try? FileManager.default.removeItem(at: legacyDirectory) }
+    let legacyIdentity = try NodeIdentity.loadOrCreate(at: legacyDirectory.appendingPathComponent("identity.plist"))
+    try check(!FileManager.default.fileExists(atPath: legacyDirectory.appendingPathComponent("address").path),
+              "legacy path API creates only identity")
+    let upgradedIdentity = try NodeIdentity.loadOrCreate(in: legacyDirectory)
+    try check(upgradedIdentity.record == legacyIdentity.record &&
+              FileManager.default.fileExists(atPath: legacyDirectory.appendingPathComponent("address").path),
+              "existing installation gains address sidecar without identity change")
+
+    let corruptDirectory = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString)
+    defer { try? FileManager.default.removeItem(at: corruptDirectory) }
+    try FileManager.default.createDirectory(at: corruptDirectory, withIntermediateDirectories: true)
+    let corruptURL = corruptDirectory.appendingPathComponent("identity.plist")
+    let corruptBytes = Data("not an identity".utf8)
+    try corruptBytes.write(to: corruptURL)
+    try rejects("corrupt identity fails without replacement") { _ = try NodeIdentity.loadOrCreate(in: corruptDirectory) }
+    try check(try Data(contentsOf: corruptURL) == corruptBytes, "corrupt identity remains unchanged")
+
+    let incompatibleDirectory = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString)
+    defer { try? FileManager.default.removeItem(at: incompatibleDirectory) }
+    try FileManager.default.createDirectory(at: incompatibleDirectory, withIntermediateDirectories: true)
+    let incompatibleURL = incompatibleDirectory.appendingPathComponent("identity.plist")
+    let incompatibleBytes = try PropertyListSerialization.data(
+        fromPropertyList: ["version": 999, "signing": Data(repeating: 1, count: 32),
+                           "agreement": Data(repeating: 2, count: 32)], format: .binary, options: 0)
+    try incompatibleBytes.write(to: incompatibleURL)
+    try rejects("incompatible identity version fails without replacement") {
+        _ = try NodeIdentity.loadOrCreate(in: incompatibleDirectory)
+    }
+    try check(try Data(contentsOf: incompatibleURL) == incompatibleBytes, "incompatible identity remains unchanged")
+
+    let orphanDirectory = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString)
+    defer { try? FileManager.default.removeItem(at: orphanDirectory) }
+    try FileManager.default.createDirectory(at: orphanDirectory, withIntermediateDirectories: true)
+    let orphanAddressURL = orphanDirectory.appendingPathComponent("address")
+    let orphanBytes = Data("\(alice.record.address)\n".utf8)
+    try orphanBytes.write(to: orphanAddressURL)
+    try rejects("address without identity fails without creating identity") {
+        _ = try NodeIdentity.loadOrCreate(in: orphanDirectory)
+    }
+    try check(!FileManager.default.fileExists(atPath: orphanDirectory.appendingPathComponent("identity.plist").path) &&
+              (try Data(contentsOf: orphanAddressURL)) == orphanBytes, "orphan address state remains unchanged")
+
+    let mismatchDirectory = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString)
+    defer { try? FileManager.default.removeItem(at: mismatchDirectory) }
+    let mismatchIdentity = try NodeIdentity.loadOrCreate(in: mismatchDirectory)
+    let mismatchAddressURL = mismatchDirectory.appendingPathComponent("address")
+    let mismatchedBytes = Data("\(bob.record.address)\n".utf8)
+    try mismatchedBytes.write(to: mismatchAddressURL, options: .atomic)
+    try rejects("address and identity mismatch fails") { _ = try NodeIdentity.loadOrCreate(in: mismatchDirectory) }
+    try check(try Data(contentsOf: mismatchAddressURL) == mismatchedBytes &&
+              mismatchIdentity.record.address != bob.record.address, "mismatched address remains unchanged")
+
+    let unreadableDirectory = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString)
+    defer { try? FileManager.default.removeItem(at: unreadableDirectory) }
+    _ = try NodeIdentity.loadOrCreate(in: unreadableDirectory)
+    let unreadableURL = unreadableDirectory.appendingPathComponent("identity.plist")
+    let unreadableBytes = try Data(contentsOf: unreadableURL)
+    try FileManager.default.setAttributes([.posixPermissions: 0o000], ofItemAtPath: unreadableURL.path)
+    defer { try? FileManager.default.setAttributes([.posixPermissions: 0o600], ofItemAtPath: unreadableURL.path) }
+    try rejects("unreadable identity fails without replacement") {
+        _ = try NodeIdentity.loadOrCreate(in: unreadableDirectory)
+    }
+    try FileManager.default.setAttributes([.posixPermissions: 0o600], ofItemAtPath: unreadableURL.path)
+    try check(try Data(contentsOf: unreadableURL) == unreadableBytes, "unreadable identity remains unchanged")
 
     let original = InnerFrame(kind: .text, port: 7000, payload: Data("hello".utf8), sourceRecord: alice.record)
     let sealed = try alice.seal(original, to: bob.record)
@@ -76,6 +157,8 @@ do {
     try check(!router.ingest(try carol.makeLinkState(sequence: 1, neighbors: [])), "stale topology rejected")
     let forged = LinkState(origin: carol.record, sequence: 2, neighbors: [], signature: Data(repeating: 0, count: 64))
     try check(!router.ingest(forged), "forged topology rejected")
+    try check((try NodeIdentity.loadOrCreate(in: directory)).record.address == stored1.record.address,
+              "route and peer topology changes do not alter persistent local address")
 
     let firewall = MeshFirewall()
     try check(!firewall.allows(port: 80, source: alice.record.address), "firewall defaults to deny")

Sources/umnd/MeshDaemon.swift

@@ -53,7 +53,7 @@ final class MeshDaemon {
     init(baseURL: URL = FileManager.default.homeDirectoryForCurrentUser
         .appendingPathComponent("Library/Application Support/UltraMesh"), socketPath: String? = nil) throws {
         try FileManager.default.createDirectory(at: baseURL, withIntermediateDirectories: true)
-        identity = try NodeIdentity.loadOrCreate(at: baseURL.appendingPathComponent("identity.plist"))
+        identity = try NodeIdentity.loadOrCreate(in: baseURL)
         router = LinkStateRouter(local: identity.record.address)
         configURL = baseURL.appendingPathComponent("config.json")
         config = DaemonConfig.load(from: configURL)

scripts/install.sh

@@ -82,5 +82,8 @@ STATUS=$("${BIN_DIR}/umn" status)
 echo "${STATUS}"
 INTERFACE=$("${BIN_DIR}/umn" interface status)
 echo "${INTERFACE}"
+ADDRESS=$("${BIN_DIR}/umn" address)
+STORED_ADDRESS=$(tr -d '[:space:]' < "${STATE_DIR}/address")
+[[ "${ADDRESS}" == "${STORED_ADDRESS}" ]] || { echo "identity address health check failed: umn address does not match ${STATE_DIR}/address." >&2; exit 1; }
 [[ "${STATUS}" == *"DNS listening"* ]] || { echo "DNS health check failed (port 53535 may be busy)." >&2; exit 1; }
 [[ "${INTERFACE}" == *"helper: connected"* ]] || { echo "native interface health check failed." >&2; exit 1; }

scripts/uninstall.sh

@@ -26,4 +26,4 @@ sudo launchctl bootout system "${HELPER_PLIST}" >/dev/null 2>&1 || true
 if [[ -e "${RESOLVER_PATH}" ]] && cmp -s "${TEMP_RESOLVER}" "${RESOLVER_PATH}"; then sudo unlink "${RESOLVER_PATH}"; fi
 
 echo "Binaries, LaunchAgent, LaunchDaemon, routes, interface, and managed resolver removed."
-echo "Identity and configuration were preserved in ~/Library/Application Support/UltraMesh."
+echo "All persistent state, including identity and address, was preserved in ~/Library/Application Support/UltraMesh."