From 333f743114b2576ab5f252033f19e462729d4c3d Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonyg@leastfixedpoint.com>
Date: Wed, 29 May 2024 11:50:23 +0200
Subject: [PATCH] Experimental sealing

---
 packages/core/src/index.ts     |  1 +
 packages/ws-relay/package.json |  3 +-
 packages/ws-relay/src/index.ts |  5 ++-
 packages/ws-relay/src/seal.ts  | 71 ++++++++++++++++++++++++++++++++++
 4 files changed, 76 insertions(+), 4 deletions(-)
 create mode 100644 packages/ws-relay/src/seal.ts

diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index 2b0cadb..fc759e0 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -20,6 +20,7 @@ export * as Skeleton from './runtime/skeleton.js';
 export * from './runtime/space.js';
 export * from './runtime/supervise.js';
 
+export * as SaltyCrypto from 'salty-crypto';
 export * as Cryptography from './transport/cryptography.js';
 export * as WireProtocol from './transport/protocol.js';
 export * as Relay from './transport/relay.js';
diff --git a/packages/ws-relay/package.json b/packages/ws-relay/package.json
index feb7951..1f4a0f6 100644
--- a/packages/ws-relay/package.json
+++ b/packages/ws-relay/package.json
@@ -28,8 +28,7 @@
     "@preserves/core": "^0.995.200"
   },
   "dependencies": {
-    "@syndicate-lang/core": "^0.34.5",
-    "salty-crypto": "0.3"
+    "@syndicate-lang/core": "^0.34.5"
   },
   "devDependencies": {
     "@syndicate-lang/ts-plugin": "^0.36.5",
diff --git a/packages/ws-relay/src/index.ts b/packages/ws-relay/src/index.ts
index cc3cb80..bd41123 100644
--- a/packages/ws-relay/src/index.ts
+++ b/packages/ws-relay/src/index.ts
@@ -24,14 +24,15 @@ import {
     stringify,
     underlying,
     Embeddable,
+    SaltyCrypto,
 } from "@syndicate-lang/core";
 import G = Schemas.gatekeeper;
 import S = Schemas.sturdy;
 import N = Schemas.noise;
 import T = Schemas.transportAddress;
 import E = Schemas.stdenv;
-import * as SaltyCrypto from 'salty-crypto';
-export * as SaltyCrypto from 'salty-crypto';
+
+export * from './seal.js';
 
 type TransportState = {
     addr: T.WebSocket,
diff --git a/packages/ws-relay/src/seal.ts b/packages/ws-relay/src/seal.ts
new file mode 100644
index 0000000..da17a9e
--- /dev/null
+++ b/packages/ws-relay/src/seal.ts
@@ -0,0 +1,71 @@
+/// SPDX-License-Identifier: GPL-3.0-or-later
+/// SPDX-FileCopyrightText: Copyright © 2024 Tony Garnock-Jones <tonyg@leastfixedpoint.com>
+
+import { Bytes, Value, encode, decode, isEmbedded, isSequence } from "@preserves/core";
+import { SaltyCrypto, Ref } from "@syndicate-lang/core";
+
+const aead = SaltyCrypto.ChaCha20Poly1305_RFC8439;
+
+export type Sealed = [Bytes, number, number, number];
+
+export function makeSeal() {
+    const key = new DataView(SaltyCrypto.randomBytes(aead.KEYBYTES).buffer);
+    const n = new SaltyCrypto.Nonce();
+    return {
+        seal(v: Value<Ref>): Promise<Sealed> {
+            return new Promise(k => {
+                at this.sealer {
+                    send message [v, create ({
+                        message(reply) { k(reply as Sealed); }
+                    })];
+                }
+            });
+        },
+
+        unseal(sealed: Sealed): Promise<{ ok: true, value: Value } | { ok: false }> {
+            return new Promise(k => {
+                at this.unsealer {
+                    send message [sealed, create ({
+                        message(reply) { k(reply as any); }
+                    })];
+                }
+            });
+        },
+
+        sealer: create ({
+            message(req) {
+                if (isSequence(req) && req.length === 2 && isEmbedded(req[1])) {
+                    try {
+                        const [term, k] = req;
+                        const m = encode(term);
+                        const c = aead.encrypt(m._view, key, n);
+                        at k { send message [Bytes.from(c), n.lo, n.hi, n.extra]; }
+                        n.increment();
+                    } catch (_e) { console.error('Failed sealing: ' + _e); }
+                }
+            }
+        }),
+
+        unsealer: create ({
+            message(req) {
+                if (
+                    isSequence(req) && req.length === 2 && isEmbedded(req[1]) &&
+                        isSequence(req[0]) && req[0].length === 4 &&
+                        Bytes.isBytes(req[0][0]) &&
+                        typeof req[0][1] === 'number' &&
+                        typeof req[0][2] === 'number' &&
+                        typeof req[0][3] === 'number'
+                ) {
+                    const [[c, lo, hi, extra], k] = req;
+                    try {
+                        const n = new SaltyCrypto.Nonce(lo, hi, extra);
+                        const m = aead.decrypt(c._view, key, n);
+                        at k { send message { ok: true, value: decode(Bytes.from(m)) }; }
+                    } catch (e) {
+                        at k { send message { ok: false }; }
+                    }
+                }
+            },
+        }),
+    };
+}