Node signing helper

signing.js

import crypto from "crypto";

const separator = ":";

export function sign(content, secret) {
  const signature = generateSignature(content, secret);
  return {
    signature,
    content,
    signedContent: join(content, signature)
  };
}

export function verify(signedContent, secret) {
  const { signature, content } = separate(signedContent);
  const signatureCheck = generateSignature(content, secret);

  const signatureCheckBuffer = Buffer.from(signatureCheck);
  const signatureBuffer = Buffer.from(signature);
  return {
    result:
      signatureCheckBuffer.length === signatureBuffer.length &&
      crypto.timingSafeEqual(signatureCheckBuffer, signatureBuffer),
    content,
    signature,
    signedContent
  };
}

export function generateSignature(content, secret) {
  const hmac = crypto.createHmac("sha256", secret);
  hmac.update(content);
  return hmac.digest("hex");
}

export function separate(signed) {
  const parts = signed.split(separator);
  const signature = parts.pop();
  const content = parts.join(separator);

  return {
    content,
    signature
  };
}

export const join = (content, hash) => content + separator + hash;

signing.ts

import crypto from "crypto";

const sessionSecret = "my-super-secret";

const separator = ":";

type Signature = {
  signature: string;
  content: string;
  signedContent: string;
  result?: boolean;
};

export function sign(content: string): Signature {
  const signature = generateSignature(content);
  return {
    signature,
    content,
    signedContent: join(content, signature)
  };
}

export function verify(signedContent: string): Signature {
  const { signature, content } = separate(signedContent);
  const signatureCheck = generateSignature(content);

  const signatureCheckBuffer = Buffer.from(signatureCheck);
  const signatureBuffer = Buffer.from(signature);
  return {
    result:
      signatureCheckBuffer.length === signatureBuffer.length &&
      crypto.timingSafeEqual(signatureCheckBuffer, signatureBuffer),
    content,
    signature,
    signedContent
  };
}

export function generateSignature(content) {
  const hmac = crypto.createHmac("sha256", sessionSecret);
  hmac.update(content);
  return hmac.digest("hex");
}

export function separate(signed) {
  const parts = signed.split(separator);
  const signature = parts.pop();
  const content = parts.join(separator);

  return {
    content,
    signature
  };
}

export const join = (content, hash) => `${content}${separator}${hash}`;