Digest access authentication: Difference between revisions

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'''Digest access authentication''' is one of the agreed-upon methods a [[web server]] can use to negotiate credentials, such as username or password, with a user's [[web browser]]. This can be used to confirm the identity of a user before sending sensitive information, such as online banking transaction history. It applies a [[hash function]] to the username and [[password]] before sending them over the network. In contrast, [[basic access authentication]] uses the easily reversible [[Base64]] encoding instead of hashing, making it non-secure unless used in conjunction with [[Transport Layer Security|TLS]].

Technically, digest authentication is an application of [[MD5]] [[cryptographic hash]]ing with usage of [[cryptographic nonce|nonce]] values to prevent [[replay attack]]s. It uses the [[Hypertext Transfer Protocol|HTTP]] protocol.

ThisDIGEST-MD5 standardas a [[Simple_Authentication_and_Security_Layer|SASL]] mechanism specified by {{IETF RFC|2831}} is obsolete since July 2011.<ref>[https://datatracker.ietf.org/doc/html/rfc6331 Moving DIGEST-MD5 to Historic, July 2011].</ref>

== Overview ==

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The above shows that when qop is not specified, the simpler RFC 2069 standard is followed.

In September 2015, RFC 7616 replaced RFC 2617 by adding 4 new [[Algorithm|algorithms]]: "SHA-256", "SHA-256-sess", "SHA-512-256" and "SHA-512-256-sess". The encoding is equivalent to "MD5" and "MD5-sess" algorithms, with [[MD5|MD5 hashing function]] replaced with [[SHA-256]] and [[SHA-256|SHA-512-256]]. However, {{as of|2021|7|lc=y}}, none of popular browsers, including Firefox<ref>{{cite web |title=Bug 472823: SHA 256 Digest Authentication |url=https://bugzilla.mozilla.org/show_bug.cgi?id=472823 |website=Mozilla Bugzilla}}</ref> and Chrome,<ref>{{cite web |title= Issue 1160478: SHA-256 for HTTP Digest Access Authentication in accordance with rfc7616 |url=https://bugs.chromium.org/p/chromium/issues/detail?id=1160478 |website=Chromium bugs}}</ref> support SHA-256 as the hash function. {{As of|2021|10}}, Firefox 93<ref>{{cite web |title=Bug 472823: SHA 256 Digest Authentication |url=https://bugzilla.mozilla.org/show_bug.cgi?id=472823 |website=Mozilla Bugzilla}}</ref> officially supports "SHA-256" and "SHA-256-sess" algorithms for digest authentication. However, support for "SHA-512-256", "SHA-512-256-sess" algorithms and username hashing<ref>{{cite news |title=IETF.org: RFC 7616 Username Hashing |url=https://datatracker.ietf.org/doc/html/rfc7616#section-3.4.4 |newspaper=Ietf Datatracker|date=30 September 2015 }}</ref> is still lacking.<ref>{{cite web |title=Mozilla-central: support SHA-256 HTTP Digest auth |url=https://hg.mozilla.org/mozilla-central/rev/7a4994734e00 |website=Mozilla-central}}</ref> {{As of|2023|8}}, Chromium 117 (then Chrome and Edge) supports "SHA-256".<ref>{{cite web |title=Chrome Feature: RFC 7616 Digest auth: Support SHA-256 and username hashing|url=https://chromestatus.com/feature/5139896267702272?context=myfeatures}}</ref>

== Impact of MD5 security on digest authentication ==

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| title = On the Security of HMAC and NMAC Based on HAVAL, MD4, MD5, SHA-0 and SHA-1

|author1=Jongsung Kim |author2=Alex Biryukov |author3=Bart Preneel |author4=Seokhie Hong | publisher = [[International Association for Cryptologic Research|IACR]]

}}</ref> cause some doubt over other MD5 applications as well. So far, however, MD5 collision attacks have not been shown to pose a threat to digest authentication{{Citation needed|date=November 2014}}, and the RFC 2617 allows servers to implement mechanisms to detect some collision and [[replay attack]]s.

== HTTP digest authentication considerations ==

{{Unreferenced section|date=July 2024}}

=== Advantages ===

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| first7 = L.

| s2cid = 27137261

| url-access = subscription

}}</ref>

* Digest access authentication prevents the use of a strong password hash (such as [[bcrypt]]) when storing passwords (since either the password, or the digested username, realm and password must be recoverable)

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== Deprecations ==

Because of the disadvantages of Digest authentication compared to Basic authentication over HTTPS it has been deprecated by a lot of software e.g.:

* Bitbucket<ref>{{Cite web |last=DeLorenzo |first=Ike |date=2015-04-03 |title=Fare-thee-well, Digest access authentication |url=https://bitbucket.org/blog/fare-thee-well-digest-access-authentication |access-date=2025-01-21 |website=Bitbucet |archive-url=https://web.archive.org/web/20240423145906/https://bitbucket.org/blog/fare-thee-well-digest-access-authentication |archive-date=2024-04-23}}</ref>

* Symfony PHP framework<ref>{{Cite web |title=[RFC] Deprecate HTTP Digest authentication · Issue #24325 · symfony/symfony |url=https://github.com/symfony/symfony/issues/24325 |access-date=2025-01-21 |archive-url=https://web.archive.org/web/20231012074234/https://github.com/symfony/symfony/issues/24325 |archive-date=2023-10-12 |website=GitHub |language=en}}</ref>

* Symfony PHP framework: https://github.com/symfony/symfony/issues/24325

== See also ==