Duplicate `Authorization` headers should not be ignored.

[issuefiler]

The context

A sender can send multiple Authorization headers in a request, because the Authorization header’s definition, credentials, allows multiple auth-params to be recombined as a comma-separated list.

RFC 9110 — HTTP semantics

a sender MUST NOT generate multiple field lines with the same name in a message (whether in the headers or trailers) or append a field line when a field line of the same name already exists in the message, unless that field's definition allows multiple field line values to be recombined as a comma-separated list (i.e., at least one alternative of the field's definition allows a comma-separated list, such as an ABNF rule of #(values) defined in Section 5.6.1).

Authorization = credentials

credentials = auth-scheme [ 1*SP ( token68 / #auth-param ) ]

---

Node.js MAY join them together with , .

RFC 9110 — HTTP semantics

A recipient MAY combine multiple field lines within a field section that have the same field name into one field line, without changing the semantics of the message, by appending each subsequent field line value to the initial field line value in order, separated by a comma (",") and optional whitespace (OWS, defined in Section 5.6.3). For consistency, use comma SP.

---

Currently, Node.js ignores duplicate Authorization headers when it creates message.headers.

Node.js 19.2.0 documentation — HTTP

• Duplicates of age, authorization, content-length, content-type, etag, expires, from, host, if-modified-since, if-unmodified-since, last-modified, location, max-forwards, proxy-authorization, referer, retry-after, server, or user-agent are discarded.
• …
• For all other headers, the values are joined together with , .

Suggestion

I suggest Node.js join the field line values of multiple Authorization headers in a request with , , instead of ignoring them, when it creates message.headers.

The related issue

#3591

[aduh95]

Can you share a minimal repro, the expected result, and the actual result?

[issuefiler]

Proof-of-concept

import Network from "node:net";
import HTTP from "node:http";

const server = HTTP.createServer(request => console.log(request.headers))
	.listen(_ => {
		const client = Network.createConnection(
			server.address().port,
			_ => client.write(
				"GET / HTTP/1.1\r\n"
				+ `Authorization: Digest username="ha"\r\n`
				+ `Authorization: realm="no"\r\n\r\n`
			)
		);
	});

The actual output

{ authorization: 'Digest username="ha"' }

The expected output

{ authorization: 'Digest username="ha", realm="no"' }

---

@aduh95.

[issuefiler]

But now that I think of it, splitting the Authorization header field value like this (Authorization: realm="no") could be violation of the RFC, Authorization = credentials.

[aduh95]

@nodejs/http

[issuefiler]

RFC 9110 — HTTP semantics

5.2. Field Lines and Combined Field Value

Field sections are composed of any number of “field lines,” each with a “field name” (see Section 5.1) identifying the field, and a “field line value” that conveys data for that instance of the field.

…When a field name is repeated within a section, its combined field value consists of the list of corresponding field line values within that section, concatenated in order, with each field line value separated by a comma.

For example, this section:

Example-Field: Foo, Bar
Example-Field: Baz

contains two field lines, both with the field name “Example-Field.” The first field line has a field line value of “Foo, Bar,” while the second field line value is “Baz.” The field value for “Example-Field” is the list “Foo, Bar, Baz.”

11.6.2. Authorization

…Its value consists of credentials containing the authentication information of the user agent for the realm of the resource being requested.

Authorization = credentials

I am not sure whether the “value” in the section §11.6.2 means a “(combined) field value” or “field line value.”

If it means the former,

Authorization: Digest username="ha"
Authorization: realm="no"

would be valid _{(meaning, Node.js should respect multiple occurrences of Authorization headers)},

and if it means the latter, invalid _{(meaning, Node.js is fine as is)}.

[ShogunPanda]

According to section https://www.rfc-editor.org/rfc/rfc9110#name-changes-from-rfc-7230, if there is no clear indication of "field line value" then it refers to combined value.

Now, AFAIK Node implements RFC 7230 and not RFC 9110, so I wonder whether we should implement this or not.

@nodejs/http @nodejs/tsc WDYT?

[bnoordhuis]

One problem I see is there's a non-zero risk of breaking existing programs if we make this change.

[mcollina]

If we want to support this it would be behind an option.

[marco-ippolito]

We can leave the default behaviour as it is and implement a flag in http.createServer() like allowDuplicateHeaders and combine them with ,. Maybe in a future release this can become the standard behaviour.
WDYT?

[issuefiler]

That sounds good to me. The future documentation on that option would refer to RFC 9110.

[mcollina]

As I said, I would recommend adding an option and possibly documenting it as experimental. I don't have much time to look into RFC 9110 and how it changed things.

Note that a lot of old clients and servers are very lenient on HTTP semantics, so they can expect whatever.

[marco-ippolito]

I will open a PR