Rust library for HTTP authentication. Parses challenge lists, responds to Basic and Digest challenges. Likely to be extended with server support and additional auth schemes.

HTTP authentication is described in the following documents and specifications:

• MDN documentation.
• RFC 7235: Hypertext Transfer Protocol (HTTP/1.1): Authentication.
• RFC 7617: The ‘Basic’ HTTP Authentication Scheme
• RFC 7616: HTTP Digest Access Authentication

This framework is primarily used with HTTP, as suggested by the name. It is also used by some other protocols such as RTSP.

Status

Young but well-tested. The API may change to improve ergonomics and functionality. New functionality is likely to be added. PRs welcome!

Goals

In order:

1. sound. Currently no unsafe blocks in http-auth itself. All dependencies are common, trusted crates.
2. correct. Precisely implements the specifications except where noted. Fuzz tests verify the hand-written parser never panics and matches a nom-based reference implementation.
3. light-weight. Minimal dependencies; uses Cargo features so callers can avoid them when undesired. Simple code that minimizes monomorphization bloat. Small data structures; eg http_auth::DigestClient currently weighs in at 32 bytes plus one allocation for all string fields.
4. complete. Implements both parsing and responding to challenges. (Currently only supports the client side and responding to the most common Basic and Digest schemes; future expansion is likely.)
5. ergonomic. Creating a client for responding to a password challenge is a one-liner from a string header or a http::header::GetAll.
6. fast enough. HTTP authentication is a small part of a real program, and http-auth's CPU usage should never be noticeable. For Digest's cryptographic operations, it uses popular optimized crates. In other respects, http-auth is likely at least as efficient as other HTTP authentication crates, although I have no reason to believe their performance is problematic.

Why a new crate?

There are at least a couple other available crates relating to HTTP authentication. You may prefer them. Here's why http-auth's author decided not to use them.

www-authenticate

• sound: www-authenticate has some unsound transmutes to static lifetime. (These likely aren't hard to fix though.)
• light-weight: www-authenticate depends on hyperx and unicase, large dependencies which many useful programs don't include.
• complete: www-authenticate only supports parsing of challenge lists, not responding to them.

digest_auth

• complete: digest_auth only supports Digest. It can't parse multiple challenges and will fail if given a list that starts with another scheme. Thus, if the server follows the advice of RFC 7235 section 2.1 and lists another scheme such as Basic first, digest_auth's parsing is insufficient.

www-authenticate + digest_auth together

In addition to the www-authenticate caveats above, responding to password challenges by using both www-authenticate and digest_auth is not complete and ergonomic. The caller must do extra work:

• explicitly consider both Digest and Basic, rather than using the abstract http_auth::PasswordClient that chooses the challenge for you.
• when responding to a Digest challenge, construct a matching digest_auth::WwwAuthenticateHeader from the www_authenticate::DigestChallenge.
• when responding to a Basic challenge, do the encoding manually.

Author

Scott Lamb <slamb@slamb.org>

License

SPDX-License-Identifier: MIT OR Apache-2.0

See LICENSE-MIT.txt or LICENSE-APACHE, respectively.