feat: write a simple crypto.subtle based hmac implementation to stop relying on old std

Author: oplik0

lib/helpers.ts

@@ -1,10 +1,11 @@
 /**
  * @todo document this module
  */
-import { crypto } from "https://deno.land/std@0.152.0/crypto/mod.ts";
-import { decode, encode } from "https://deno.land/std@0.152.0/encoding/base64.ts";
-import { HmacSha256 } from "https://deno.land/[email protected]/hash/sha256.ts";
+import { crypto } from "std/crypto/mod.ts";
+import { decodeBase64, encodeBase64 } from "std/encoding/base64.ts";
+import { hmacSHA256 } from "./hmac.ts";
 // dprint-ignore-next-line
+// deno-fmt-ignore
 export type logN = 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63;
 export interface ScryptParameters {
   logN?: logN;
@@ -26,27 +27,31 @@ export function formatScrypt(
   const encoder = new TextEncoder();
   const result = new Uint8Array(96);
   const dataview = new DataView(result.buffer);
-  const hmac = new HmacSha256(new Uint8Array(decode(rawHash)).subarray(32));
   // first 6 bytes are the word "scrypt", 7th byte is 0
   result.set([115, 99, 114, 121, 112, 116, 0], 0);
   dataview.setUint8(7, logN);
   dataview.setUint32(8, r, false);
   dataview.setUint32(12, p, false);
   result.set(typeof salt === "string" ? encoder.encode(salt) : salt, 16);
-  const hashedResult = crypto.subtle.digestSync("SHA-256", result.subarray(0, 48));
+  const hashedResult = crypto.subtle.digestSync(
+    "SHA-256",
+    result.subarray(0, 48),
+  );
   result.set(new Uint8Array(hashedResult), 48);
-  hmac.update(result.subarray(0, 64));
   result.set(
-    hmac.array(),
+    hmacSHA256(
+      new Uint8Array(decodeBase64(rawHash)).subarray(32),
+      result.subarray(0, 64),
+    ),
     64,
   );
   // encode the result as a base64 string
-  return encode(result);
+  return encodeBase64(result);
 }
 function decomposeScrypt(
   formattedHash: string,
 ): ScryptParameters {
-  const bytes: Uint8Array = new Uint8Array(decode(formattedHash));
+  const bytes: Uint8Array = new Uint8Array(decodeBase64(formattedHash));
   const dataview: DataView = new DataView(bytes.buffer);
   const parameters: ScryptParameters = {};
   parameters.logN = bytes[7] as logN;
@@ -74,15 +79,16 @@ export function formatPHC(
   salt: string | Uint8Array,
 ): string {
   // convert salt to base64 without padding
-  salt = encode(salt).replace(/=/g, "");
+  salt = encodeBase64(salt).replace(/=/g, "");
   rawHash = rawHash.replace(/=/g, "");
   return `\$scrypt\$ln=${logN},r=${r},p=${p}\$${salt}\$${rawHash}`;
 }
 function decomposePHC(formattedHash: string): ScryptParameters {
-  const regex = /\$scrypt\$ln=(?<logN>\d+),r=(?<r>\d+),p=(?<p>\d+)\$(?<salt>[a-zA-Z0-9\-\_\+\/\=]*)\$/;
+  const regex =
+    /\$scrypt\$ln=(?<logN>\d+),r=(?<r>\d+),p=(?<p>\d+)\$(?<salt>[a-zA-Z0-9\-\_\+\/\=]*)\$/;
   const parameters: ScryptParameters = formattedHash.match(regex)
     ?.groups as ScryptParameters;
-  parameters.salt = new Uint8Array(decode(parameters.salt as string));
+  parameters.salt = new Uint8Array(decodeBase64(parameters.salt as string));
   // the PHC format from passlib always uses 32 bytes hashes
   parameters.dklen = 32;
   return parameters;

lib/hmac.ts

@@ -0,0 +1,40 @@
+/**
+ * A very primitive crypto.subtle.digestSync-based HMAC-SHA256 synchronous implementation.
+ */
+import { crypto } from "std/crypto/mod.ts";
+
+function mergeArrays(a: Uint8Array, b: Uint8Array): Uint8Array {
+  const result = new Uint8Array(a.length + b.length);
+  result.set(a);
+  result.set(b, a.length);
+  return result;
+}
+function blockSizedKey(key: Uint8Array, blockSize: number): Uint8Array {
+  if (key.length > blockSize) {
+    return new Uint8Array(crypto.subtle.digestSync("SHA-256", key));
+  } else if (key.length < blockSize) {
+    const result = new Uint8Array(blockSize);
+    result.set(key);
+    return result;
+  }
+  return key;
+}
+
+export function hmacSHA256(key: Uint8Array, data: Uint8Array): Uint8Array {
+  const b_key = blockSizedKey(key, 64);
+  const o_pad = new Uint8Array(64);
+  const i_pad = new Uint8Array(64);
+  for (let i = 0; i < 64; i++) {
+    o_pad[i] = b_key[i] ^ 0x5c;
+    i_pad[i] = b_key[i] ^ 0x36;
+  }
+  return new Uint8Array(crypto.subtle.digestSync(
+    "SHA-256",
+    mergeArrays(
+      o_pad,
+      new Uint8Array(
+        crypto.subtle.digestSync("SHA-256", mergeArrays(i_pad, data)),
+      ),
+    ),
+  ));
+}

lib/hmac_bench.ts

@@ -0,0 +1,66 @@
+import { decodeHex } from "std/encoding/hex.ts";
+import { hmacSHA256 } from "./hmac.ts";
+import { HmacSha256 } from "https://deno.land/[email protected]/hash/sha256.ts";
+
+Deno.bench("hmac - subtle", { group: "small hmac", baseline: true }, () => {
+  hmacSHA256(
+    decodeHex("0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b"),
+    decodeHex("4869205468657265"),
+  );
+});
+Deno.bench("hmac - old", { group: "small hmac" }, () => {
+  const hmac = new HmacSha256(
+    decodeHex("0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b"),
+  );
+  hmac.update(decodeHex("4869205468657265"));
+  hmac.digest();
+});
+
+Deno.bench("hmac - subtle", { group: "larger hmac", baseline: true }, () => {
+  hmacSHA256(
+    decodeHex(
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    ),
+    decodeHex(
+      "5468697320697320612074657374207573696e672061206c6172676572207468616e20626c6f636b2d73697a65206b657920616e642061206c6172676572207468616e20626c6f636b2d73697a6520646174612e20546865206b6579206e6565647320746f20626520686173686564206265666f7265206265696e6720757365642062792074686520484d414320616c676f726974686d2e",
+    ),
+  );
+});
+Deno.bench("hmac - old", { group: "larger hmac" }, () => {
+  const hmac = new HmacSha256(
+    decodeHex(
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    ),
+  );
+  hmac.update(
+    decodeHex(
+      "5468697320697320612074657374207573696e672061206c6172676572207468616e20626c6f636b2d73697a65206b657920616e642061206c6172676572207468616e20626c6f636b2d73697a6520646174612e20546865206b6579206e6565647320746f20626520686173686564206265666f7265206265696e6720757365642062792074686520484d414320616c676f726974686d2e",
+    ),
+  );
+  hmac.digest();
+});
+
+// appears to be comparable to the old implementation in practice
+Deno.bench("hmac - subtle", { group: "hmac as used", baseline: true }, () => {
+  hmacSHA256(
+    decodeHex(
+      "834680896aab19cf86a4c0edf4cef4db8af5bd05a40d42e768e658057ee521e63acadefa59fb2f3133def01d2c3dd5d1",
+    ).subarray(0, 48),
+    decodeHex(
+      "024b5b12a8b3d622c289ad69536a30cda848074c82d06ff05775d653bf0fc48033ddafba8071b7f119810dd57619553e87aff3bc8c237669523dc6530b8ee267",
+    ).subarray(0, 64),
+  );
+});
+Deno.bench("hmac - old", { group: "hmac as used" }, () => {
+  const hmac = new HmacSha256(
+    decodeHex(
+      "834680896aab19cf86a4c0edf4cef4db8af5bd05a40d42e768e658057ee521e63acadefa59fb2f3133def01d2c3dd5d1",
+    ).subarray(0, 48),
+  );
+  hmac.update(
+    decodeHex(
+      "024b5b12a8b3d622c289ad69536a30cda848074c82d06ff05775d653bf0fc48033ddafba8071b7f119810dd57619553e87aff3bc8c237669523dc6530b8ee267",
+    ).subarray(0, 64),
+  );
+  hmac.digest();
+});

lib/hmac_test.ts

@@ -0,0 +1,18 @@
+import { hmacSHA256 } from "./hmac.ts";
+import { decodeHex } from "std/encoding/hex.ts";
+import { assertEquals } from "std/assert/assert_equals.ts";
+
+const encoder = new TextEncoder();
+
+Deno.test("basic hmacSHA256", (): void => {
+  const result = hmacSHA256(
+    decodeHex("0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b"),
+    decodeHex("4869205468657265"),
+  );
+  assertEquals(
+    result,
+    decodeHex(
+      "b0344c61d8db38535ca8afceaf0bf12b881dc200c9833da726e9376c2e32cff7",
+    ),
+  );
+});