first commit

Author: lsongdev

.gitignore

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+
+yarn.lock
+
+node_modules/

README.md

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+# kelp-cors
+
+[Cross-Origin Resource Sharing(CORS)](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS) Middleware for [Kelp Project](https://github.com/kelpjs).
+
+## Installation
+
+```bash
+$ npm i kelp-cors --save
+```
+
+## Example
+
+```js
+const http = require('http');
+const kelp = require('kelp');
+const cors = require('kelp-cors');
+
+const app = kelp();
+
+app.use(cors({
+  allowOrigin: 'baidu.com',
+  allowMethods: ['POST', 'GET'],
+  allowHeaders: ['X-MY-HEADER', 'X-Y-HEADER'],
+  exposeHeaders: ['X-MY-HEADER'],
+  maxAge: 3600,
+  allowCredentials: true,
+}));
+
+app.use((req, res) => {
+  res.end("hello world");
+});
+
+http.createServer(app).listen(3000);
+```
+
+Also accept function as options:
+
+```js
+app.use(cors(({ preflight }) => {
+  console.log('preflight:', preflight);
+  return { alloworigin: '*', allowcredentials: false };
+}));
+```
+
+## Contributing
+
++ Fork this Repo first
++ Clone your Repo
++ Install dependencies by $ npm install
++ Checkout a feature branch
++ Feel free to add your features
++ Make sure your features are fully tested
++ Publish your local branch, Open a pull request
++ Enjoy hacking <3
+
+
+## MIT license
+
+Copyright (c) 2016 Lsong <song940@gmail.com>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

example/index.js

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+const http = require('http');
+const kelp = require('kelp');
+const cors = require('..');
+
+const app = kelp();
+
+app.use(cors({
+  allowOrigin: 'baidu.com',
+  allowMethods: ['POST', 'GET'],
+  allowHeaders: ['X-MY-HEADER', 'X-Y-HEADER'],
+  exposeHeaders: ['X-MY-HEADER'],
+  maxAge: 3600,
+  allowCredentials: true,
+}));
+
+// app.use(cors(({ preflight }) => {
+//     console.log('preflight:', preflight);
+//     return { allowOrigin: '*', allowCredentials: false };
+// }));
+
+app.use((req, res) => {
+  res.end("hello world");
+});
+
+http.createServer(app).listen(3000);

index.js

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+const assert = require('assert');
+
+const defaultAllowMethods = 'GET,HEAD,PUT,POST,DELETE,PATCH';
+
+const split = str => {
+  if (!str) return [];
+  return str.split(',');
+};
+
+const getHeader = (req, name) => {
+  const key = name.toLowerCase();
+  return req.headers[key];
+};
+
+/**
+ * kelp-cors middleware
+ * @docs https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS
+ * @param {*} options 
+ * @returns 
+ */
+const cors = (options = {}) => {
+  const flag = typeof options === 'function';
+  /**
+   * kelp middleware
+   */
+  return async (req, res, next) => {
+    res.headers = res.headers || {};
+    let preflight = false, requestHeaders, requestMethod;
+    const requestOrigin = getHeader(req, 'Origin');
+    if (!requestOrigin) return next();
+    if (req.method === 'OPTIONS') {
+      preflight = true; // https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#preflighted_requests
+      requestMethod = getHeader(req, 'Access-Control-Request-Method');
+      requestHeaders = getHeader(req, 'Access-Control-Request-Headers');
+      if (!requestMethod) return next(); // not a valid preflight request
+    }
+    /**
+     * process allow* settings
+     */
+    let {
+      allowOrigin = requestOrigin,
+      allowMethods = defaultAllowMethods,
+      allowHeaders = requestHeaders,
+      allowCredentials = true,
+      exposeHeaders, maxAge,
+    } = flag ? await options({
+      preflight,
+      requestMethod,
+      requestOrigin,
+      requestHeaders: split(requestHeaders),
+    }) : options;
+    /**
+     * serialized
+     */
+    if (Array.isArray(allowMethods)) allowMethods = allowMethods.join(',');
+    if (Array.isArray(allowHeaders)) allowHeaders = allowHeaders.join(',');
+    if (Array.isArray(exposeHeaders)) exposeHeaders = exposeHeaders.join(',');
+    /**
+     * Please note that, when responding to a credentialed requests request, 
+     * the server must specify an origin in the value of the Access-Control-Allow-Origin header, 
+     * instead of specifying the "*" wildcard.
+     * @docs https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#requests_with_credentials
+     */
+    if (allowCredentials === true) {
+      assert.notEqual(allowOrigin, '*', '[kelp-cors] Must specify an origin instead of specifying the "*" wildcard when responding allowCredentials.');
+    }
+    /**
+     * If the server specifies a single origin (that may dynamically change 
+     * based on the requesting origin as part of a allowlist) rather than the "*" wildcard, 
+     * then the server should also include Origin in the Vary response header — 
+     * to indicate to clients that server responses will differ based on the value of the Origin request header.
+     */
+    if (allowOrigin !== '*') {
+      // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Vary
+      const vary = split(res.headers['vary']);
+      // also include ',Origin' in the 'Vary'
+      if (vary.indexOf('Origin') === -1)
+        res.setHeader('Vary', vary.concat('Origin').join(','));
+    }
+    res.setHeader('Access-Control-Allow-Origin', allowOrigin);
+    if (maxAge) res.setHeader('Access-Control-Max-Age', maxAge);
+    if (allowCredentials) res.setHeader('Access-Control-Allow-Credentials', 'true');
+    if (preflight) {
+      if (allowMethods) res.setHeader('Access-Control-Allow-Methods', allowMethods);
+      if (allowHeaders) res.setHeader('Access-Control-Allow-Headers', allowHeaders);
+      res.end();
+      return;
+    } else {
+      // @docs https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#access-control-expose-headers
+      if (exposeHeaders) res.setHeader('Access-Control-Expose-Headers', exposeHeaders);
+    }
+    return next();
+  };
+};
+
+module.exports = cors;

package.json

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+{
+  "name": "kelp-cors",
+  "version": "0.0.0",
+  "description": "Cross-Origin Resource Sharing(CORS) Middleware for Kelp Project.",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/song940/kelp-cors.git"
+  },
+  "keywords": [
+    "kelp",
+    "cors"
+  ],
+  "author": "Lsong <song940@gmail.com>",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/song940/kelp-cors/issues"
+  },
+  "homepage": "https://github.com/song940/kelp-cors#readme",
+  "devDependencies": {
+    "kelp": "^2.0.2"
+  }
+}