BREAKING: allow hashes provided as a URL to a text file or a string

(closes #1)

lib/checksum.js

@@ -0,0 +1,97 @@
+import path from "path";
+import crypto from "crypto";
+import fs from "fs-extra";
+
+import debug from "./debug.js";
+
+// Check the checksum via a parsed text file containing one or more hashes.
+export const checksumViaFile = async (desiredFile, checksumFile, algorithm, encoding) => {
+  debug(`Validating checksum of '${desiredFile}' against hashes listed in '${checksumFile}' (algo: '${algorithm}', encoding: '${encoding}')`);
+
+  const parsedHashes = await parseChecksumFile(checksumFile);
+  debug(`All hashes pulled from the checksums file '${path.basename(checksumFile)}' : ${JSON.stringify(parsedHashes)}`);
+
+  const generatedHash = await generateHashFromFile(desiredFile, algorithm, encoding);
+  debug(`Generated a ${algorithm} hash of '${path.basename(desiredFile)}' => ${generatedHash}`);
+
+  const correctHash = parsedHashes[path.basename(desiredFile)];
+  debug(`Found '${path.basename(desiredFile)}' in '${path.basename(checksumFile)}', provided hash is: ${correctHash}`);
+
+  if (!correctHash) {
+    throw new Error(`'${path.basename(desiredFile)}' isn't listed in checksums file.`);
+  }
+
+  debug(`Checking if generated === provided... ${generatedHash} : ${correctHash}`);
+  if (generatedHash !== correctHash) {
+    debug(`Nope... ${generatedHash} !== ${correctHash}`);
+    throw new Error(`Hash of '${path.basename(desiredFile)}' doesn't match the given checksum.`);
+  }
+
+  debug("Checksum validated via file, it's a match!");
+  return true;
+};
+
+// Check the checksum via a provided hash.
+export const checksumViaString = async (desiredFile, correctHash, algorithm, encoding) => {
+  debug(`Validating checksum of '${desiredFile}' against provided hash '${correctHash}' (algo: '${algorithm}', encoding: '${encoding}')`);
+
+  const generatedHash = await generateHashFromFile(desiredFile, algorithm, encoding);
+  debug(`Generated a ${algorithm} hash of '${path.basename(desiredFile)}' => ${generatedHash}`);
+
+  debug(`Checking if generated === provided... ${generatedHash} : ${correctHash}`);
+  if (generatedHash !== correctHash) {
+    debug(`Nope... ${generatedHash} !== ${correctHash}`);
+    throw new Error(`Hash of '${path.basename(desiredFile)}' doesn't match the given checksum.`);
+  }
+
+  debug("Checksum validated via string, it's a match!");
+  return true;
+};
+
+// Takes a path to a file and returns its hash.
+const generateHashFromFile = async (file, algorithm, encoding) => {
+  const fileBuffer = fs.readFileSync(file);
+  const hashSum = crypto.createHash(algorithm);
+  hashSum.update(fileBuffer);
+
+  return hashSum.digest(encoding);
+};
+
+// Largely adapted from sumchecker:
+// https://github.com/malept/sumchecker/blob/28aed640a02787490d033fda56eaee30e24e5a71/src/index.ts#L97
+const parseChecksumFile = async (checksumFile) => {
+  // read the text file holding one or more checksums
+  const data = fs.readFileSync(checksumFile, { encoding: "utf8" });
+
+  // https://regexr.com/67k7i
+  const lineRegex = /^([\da-fA-F]+) ([ *])(.+)$/;
+
+  // extract each file and its hash into this object
+  const checksums = {};
+
+  // loop through each line (should be one file & hash each)
+  let lineNumber = 0;
+  for (const line of data.trim().split(/[\r\n]+/)) {
+    lineNumber += 1;
+
+    // parse the current line using the regex pattern above
+    const parsedLine = lineRegex.exec(line);
+
+    if (parsedLine === null) {
+      // didn't match regex
+      debug(`Could not parse line number ${lineNumber}`);
+      throw new Error(lineNumber, line);
+    } else {
+      parsedLine.shift();
+
+      // eslint-disable-next-line no-unused-vars
+      const [hash, binary, file] = parsedLine;
+
+      // save the current file & hash in the checksums object
+      checksums[file] = hash;
+    }
+  }
+
+  // send back the cleaned up object of filenames & hashes
+  return checksums;
+};

lib/debug.js

@@ -0,0 +1,4 @@
+import debug from "debug";
+
+// set DEBUG=careful-downloader in environment to enable detailed logging
+export default debug("careful-downloader");

lib/download.js

@@ -0,0 +1,20 @@
+import stream from "stream";
+import { promisify } from "util";
+import fs from "fs-extra";
+import got from "got";
+
+import debug from "./debug.js";
+
+// Download any file to any destination. Returns a promise.
+export default async (url, dest) => {
+  debug(`Downloading '${url}' to '${dest}'`);
+
+  // get remote file and write locally
+  const pipeline = promisify(stream.pipeline);
+  const download = pipeline(
+    got.stream(url, { followRedirect: true }), // GitHub releases redirect to unpredictable URLs
+    fs.createWriteStream(dest),
+  );
+
+  return download;
+};