From 0d82d303d9f4ed7899cdf085032919e084285863 Mon Sep 17 00:00:00 2001
From: Pascal Perrenoud <pascal@pband.ch>
Date: Thu, 6 Jun 2024 01:50:17 +0200
Subject: [PATCH] Implement secret-box

---
 src/secret-box.ts | 63 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 src/secret-box.ts

diff --git a/src/secret-box.ts b/src/secret-box.ts
new file mode 100644
index 0000000..3ceadfd
--- /dev/null
+++ b/src/secret-box.ts
@@ -0,0 +1,63 @@
+import logger from 'log'
+import {a2b64, b642a} from 'misc'
+
+const log = logger('crypto:secret-box')
+
+export class SecretBox {
+    private constructor(
+        private readonly iv: Uint8Array,
+        private readonly cipher: Uint8Array,
+    ) {}
+
+    public static gen_key() : Promise<CryptoKey> {
+        log.trace("generate key")
+        return crypto.subtle.generateKey(
+            {
+                name: "AES-GCM",
+                length: 256,
+            },
+            true,
+            ["encrypt", "decrypt"],
+        )
+    }
+
+    public static async encrypt(data: Uint8Array, key: CryptoKey) : Promise<SecretBox> {
+        log.trace("encrypt")
+        const iv = crypto.getRandomValues(new Uint8Array(11))
+        const cipher = await crypto.subtle.encrypt(
+            {
+                name: "AES-GCM",
+                iv,
+            },
+            key,
+            data
+        )
+        return new SecretBox(iv, new Uint8Array(cipher))
+    }
+    public async decrypt(key: CryptoKey) : Promise<Uint8Array> {
+        log.trace("decrypt")
+        const buffer = await crypto.subtle.decrypt(
+            {
+                name: "AES-GCM",
+                iv: this.iv
+            },
+            key,
+            this.cipher
+        )
+        return new Uint8Array(buffer)
+    }
+
+    public toString() : string {
+        log.trace("toString")
+        const iv = a2b64(this.iv)
+        const cipher = a2b64(this.iv)
+        return `${iv}.${cipher}`
+    }
+    public static fromString(data: string) : SecretBox {
+        log.trace("fromString")
+        const parts = data.split(".", 2)
+        const iv = b642a(parts[0]).expect("Failed decode IV")
+        const cipher = b642a(parts[1]).expect("Failed to decode cipher")
+        return new SecretBox(iv, cipher)
+    }
+}