| Network Working Group | J. Reschke |
| Internet-Draft | greenbytes |
| Updates: 2617 (if approved) | August 16, 2010 |
| Intended status: Standards Track | |
| Expires: February 17, 2011 |
The "Basic" authentication scheme defined in RFC 2617 does not properly define how to treat non-ASCII characters. This has lead to a situation where user agent implementations disagree, and servers make different assumptions based on the locales they are running in. There is little interoperability for characters in the ISO-8859-1 character set, and even less interoperability for any characters beyond that.¶
This document defines a backwards-compatible extension to "Basic", specifying the server's character encoding expectation, using a new authentication scheme parameter.¶
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| I edit (type: edit, status: open) | ||
| julian.reschke@greenbytes.de | 2010-08-11 | Umbrella issue for editorial fixes/enhancements. |
| Associated changes in this document: A.1, A.2, B.2, <#rfc.change.edit.4>. | ||
| I paramcase (type: change, status: closed) | ||
| julian.reschke@greenbytes.de | 2010-08-12 | Are auth param names case-sensitive? |
| 2010-08-12 | Resolution: Be consistent with "realm" (case-insensitive). Note that should be clarified in RFC2617bis for auth params in general. | |
| Associated changes in this document: 3, 3. | ||
| I credparam (type: change, status: closed) | ||
| julian.reschke@greenbytes.de | 2010-08-12 | Should "encoding" also be defined for the credentials (the UA's response)? |
| Resolution: Disallow (but reserve) encoding in credentials, and explain why this is the case. | ||
| Associated changes in this document: 3, 3, 3, B. | ||
The "Basic" authentication scheme defined in Section 2 of [RFC2617] does not properly define how to treat non-ASCII characters ([USASCII]): it uses the Base64 [RFC4648] encoding of the concatenation of username, separator character, and password without stating which character encoding to use.¶
This has lead to a situation where user agent implementations disagree, and servers make different assumptions based on the locales they are running in. There is little interoperability for characters in the ISO-8859-1 character set ([ISO-8859-1]), and even less interoperability for any characters beyond that.¶
This document defines a backwards-compatible extension to "Basic", specifying the server's character encoding expection, using a new auth-param as defined in Section 1.2 of [RFC2617].¶
↓ServersIn challenges, servers MAY use the "encoding" authentication parameter↓(case-insensitive) to express the character encoding they expect the user agent to use. ↑[case-sens: Are parameter names case-sensitive?] ↑↓[also-cred: Should this also work as a parameter on the credentials? See Appendix del-1.] ¶
The only allowed value is "UTF-8", to be matched case-insensitively (see [RFC2978], Section 2.3), indicating that the server expects the UTF-8 character encoding to be used ([RFC3629]).¶
Other values are reserved for future use.¶
For credentials sent by the user agent, the "encoding" parameter is reserved for future use and MUST NOT be sent.
The reason for this is that the information that could be included does not seem to be useful to the server, but the additional complexity of parsing and processing the additional parameter might make this extension harder to deploy.
In the example below, the server prompts for authentication in the "foo" realm, using Basic authentication, with a preference for the UTF-8 character encoding:
WWW-Authenticate: Basic realm="foo", encoding="UTF-8"
Note that the parameter value can be either a token or a quoted string; in this case the server chose to use the quoted-string notation.
The user's name is "test", and his password is the string "123" followed by the Unicode character U+00A3 (POUND SIGN). Following Section 1.2 of [RFC2617], but using the character encoding UTF-8, the user-pass, converted to a sequence of octets, is:¶
't' 'e' 's' 't' ':' '1' '2' '3' pound 74 65 73 74 3A 31 32 33 C2 A3
dGVzdDoxMjPCow==
Thus the Authorization header field would be:¶
Authorization: Basic dGVzdDoxMjPCow==
This document does not introduce any new security considerations beyond those defined for the "Basic" authentication scheme ([RFC2617], Section 4), and those applicable to the handling of UTF-8 ([RFC3629], Section 10).¶
There are no IANA Considerations related to this specification.¶
The internationalisation problem has been reported as a Mozilla bug back in the year 2000 (see <https://bugzilla.mozilla.org/show_bug.cgi?id=41489>). It was Andrew Clover's idea to address it using a new auth-param.¶
Thanks to Martin Thomson for providing feedback on this document.¶
User agents which already default to UTF-8 do not need to be changed at all. Other user agents can keep their default behavior, and switch to UTF-8 when seeing the new parameter.
On the other hand, the strategy below may already improve the user-visible behavior today:
User agents not implementing this specifications should continue to work as before, ignoring the new parameter.
User agents which already default to the UTF-8 encoding already implement this specification by definition.
Other user agents can keep their default behavior, and switch to UTF-8 when seeing the new parameter.
On the other hand, the strategy below may already improve the user-visible behavior today:
Origin servers that expect ISO-8859-1 encoding do not require any changes. Other servers that already expect UTF-8 can add the new parameter without any risk of breaking existing user agents. [testme: We may want to confirm this with test cases.]
Origin servers that do not expect non-ASCII characters in credentials do not require any changes.
Origin servers that need to support non-ASCII characters, but can't use the UTF-8 encoding will not be affected; they will continue to function as well as before.
Finally, origin servers that need to support non-ASCII characters and can use the UTF-8 encoding can opt in as described above. In the worst case, they'll continue to see either broken credentials or no credentials at all (depending on how legacy clients handle characters they can not encode).
There are sites in use today that default to a locale encoding, such as ISO-8859-1, and expect user agents to use that encoding. These sites will break if the user agent uses a different encoding, such as UTF-8.¶
Defining a parameter on the credentials would make it easier for the server to find out what the client is sending. As far as clients only send the credentials parameter when the server opted-in through the challenge, there should be no interop issue.
This sounds like a nice-to-have, but doesn't seem to be really needed. Feedback appreciated.