From e2fe2d6db16b422ee6d69ef03f1393e1f0f42749 Mon Sep 17 00:00:00 2001
From: Florian Dold <florian@dold.me>
Date: Thu, 7 Oct 2021 12:01:40 +0200
Subject: add anastasis skeleton, put crypto in taler-util

---
 packages/taler-util/src/kdf.ts | 92 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 packages/taler-util/src/kdf.ts

(limited to 'packages/taler-util/src/kdf.ts')

diff --git a/packages/taler-util/src/kdf.ts b/packages/taler-util/src/kdf.ts
new file mode 100644
index 000000000..af4d05035
--- /dev/null
+++ b/packages/taler-util/src/kdf.ts
@@ -0,0 +1,92 @@
+/*
+ This file is part of GNU Taler
+ (C) 2019 GNUnet e.V.
+
+ GNU Taler is free software; you can redistribute it and/or modify it under the
+ terms of the GNU General Public License as published by the Free Software
+ Foundation; either version 3, or (at your option) any later version.
+
+ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along with
+ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+import * as nacl from "./nacl-fast.js";
+import { sha256 } from "./sha256.js";
+
+export function sha512(data: Uint8Array): Uint8Array {
+  return nacl.hash(data);
+}
+
+export function hmac(
+  digest: (d: Uint8Array) => Uint8Array,
+  blockSize: number,
+  key: Uint8Array,
+  message: Uint8Array,
+): Uint8Array {
+  if (key.byteLength > blockSize) {
+    key = digest(key);
+  }
+  if (key.byteLength < blockSize) {
+    const k = key;
+    key = new Uint8Array(blockSize);
+    key.set(k, 0);
+  }
+  const okp = new Uint8Array(blockSize);
+  const ikp = new Uint8Array(blockSize);
+  for (let i = 0; i < blockSize; i++) {
+    ikp[i] = key[i] ^ 0x36;
+    okp[i] = key[i] ^ 0x5c;
+  }
+  const b1 = new Uint8Array(blockSize + message.byteLength);
+  b1.set(ikp, 0);
+  b1.set(message, blockSize);
+  const h0 = digest(b1);
+  const b2 = new Uint8Array(blockSize + h0.length);
+  b2.set(okp, 0);
+  b2.set(h0, blockSize);
+  return digest(b2);
+}
+
+export function hmacSha512(key: Uint8Array, message: Uint8Array): Uint8Array {
+  return hmac(sha512, 128, key, message);
+}
+
+export function hmacSha256(key: Uint8Array, message: Uint8Array): Uint8Array {
+  return hmac(sha256, 64, key, message);
+}
+
+export function kdf(
+  outputLength: number,
+  ikm: Uint8Array,
+  salt: Uint8Array,
+  info: Uint8Array,
+): Uint8Array {
+  // extract
+  const prk = hmacSha512(salt, ikm);
+
+  // expand
+  const N = Math.ceil(outputLength / 32);
+  const output = new Uint8Array(N * 32);
+  for (let i = 0; i < N; i++) {
+    let buf;
+    if (i == 0) {
+      buf = new Uint8Array(info.byteLength + 1);
+      buf.set(info, 0);
+    } else {
+      buf = new Uint8Array(info.byteLength + 1 + 32);
+      for (let j = 0; j < 32; j++) {
+        buf[j] = output[(i - 1) * 32 + j];
+      }
+      buf.set(info, 32);
+    }
+    buf[buf.length - 1] = i + 1;
+    const chunk = hmacSha256(prk, buf);
+    output.set(chunk, i * 32);
+  }
+
+  return output.slice(0, outputLength);
+}
-- 
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