feat(OCLT-29): add HMAC wrapper

build/exports.js

@@ -3,3 +3,4 @@ export { randomBytes } from "@occult-app/crypto/random";
 export { sha256, sha512 } from "@occult-app/crypto/sha2";
 export { kdf } from "@occult-app/crypto/kdf";
 export { ppf } from "@occult-app/crypto/ppf";
+export { hmac } from "@occult-app/crypto/hmac";

src/hmac.ts

@@ -0,0 +1,25 @@
+import { subtle } from "crypto";
+import { ByteArray } from "./types";
+
+/**
+ * Computes the HMAC-SHA256 tag (hash) of the input data using the provided key.
+ *
+ * @param key The key used for HMAC computation.
+ * @param input The input data for which HMAC tag is computed.
+ * @returns The computed tag.
+ */
+async function hmac(key: ByteArray, input: ByteArray): Promise<ByteArray> {
+    const importedKey = await subtle.importKey(
+        "raw",
+        key,
+        { name: "HMAC", hash: "SHA-256" },
+        false,
+        ["sign"]
+    );
+
+    const tag = await subtle.sign("HMAC", importedKey, input);
+
+    return new Uint8Array(tag);
+}
+
+export { hmac };

src/index.ts

@@ -14,3 +14,4 @@ import { randomBytes } from "./random";
 import { sha256, sha512 } from "./sha2";
 import { kdf } from "./kdf";
 import { ppf } from "./ppf";
+import { hmac } from "./hmac";

tests/hmac.spec.ts

@@ -0,0 +1,17 @@
+import { ByteArray, bytesToHex, hexToBytes } from "../src/types";
+import { hmac } from "../src/hmac";
+
+describe("HMAC", () => {
+    it("should compute the HMAC-SHA256 hash", async () => {
+        const key: ByteArray = new Uint8Array([
+            108, 169, 151, 124, 154, 55, 16, 255, 152, 230, 112, 0, 136, 80, 171, 197, 35, 79, 55,
+            37, 161, 144, 41, 184, 148, 82, 137, 236, 132, 147, 213, 9
+        ]);
+
+        const tag: ByteArray = await hmac(key, hexToBytes("deadbeef"));
+
+        expect(bytesToHex(tag)).toEqual(
+            "e17dec46db65352eb08841a383eaee78b234e3396fa035a5e2359abea0aa4d72"
+        );
+    });
+});