Node.js invalid http header demo

README.md

Nodejs invalid http header error

When attempting to set http headers with invalid characters, Nodejs will throw a TypeError.

const http = require("http");

const server = http.createServer((req, res) => {
    // Attempting to set a header with invalid characters
    res.setHeader("CF-Region", "中文");
    res.writeHead(200, { "Content-Type": "text/plain" });
    res.end("Hello, world!");
});

const PORT = 3000;
server.listen(PORT, () => {
  console.log(`Server running at http://localhost:${PORT}/`);
});

node:_http_outgoing:628
    throw new ERR_INVALID_CHAR('header content', name);
    ^

TypeError [ERR_INVALID_CHAR]: Invalid character in header content ["CF-Region"]
    at ServerResponse.setHeader (node:_http_outgoing:651:3)
    at Server.<anonymous> (/Users/kevin.he/dev/nodehttpheader/index.js:5:7)
    at Server.emit (node:events:517:28)
    at parserOnIncoming (node:_http_server:1107:12)
    at HTTPParser.parserOnHeadersComplete (node:_http_common:119:17) {
  code: 'ERR_INVALID_CHAR'
}

Potential Solutions / Workarounds

1. Use res.writeHead instead of res.setHeader.

res.writeHead bypasses the ascii character validation, however, this is not a direct replace because res.writeHead can only be called once before response is sent.

2. encode the value via encodeURIComponent

solution.js

const http = require("http");

const server = http.createServer((req, res) => {
    // Attempting to set a header with invalid characters
    res.setHeader("CF-Region", encodeURIComponent("中文"));
    res.writeHead(200, { "Content-Type": "text/plain" });
    res.end("Hello, world!");
});

const PORT = 3000;
server.listen(PORT, () => {
  console.log(`Server running at http://localhost:${PORT}/`);
});