Http Basic Authentication 的请求头Authorization的状态保存问题：见‘斜粗下划线’部分说明

Basic access authentication

From Wikipedia, the free encyclopedia

HTTP
Persistence Compression HTTPS
Request methods
OPTIONS GET HEAD POST PUT DELETE TRACE CONNECT PATCH
Header fields
Cookie ETag Location HTTP referer DNT X-Forwarded-For
Status codes
301 Moved Permanently 302 Found 303 See Other 403 Forbidden 404 Not Found
v t e

In the context of an HTTP transaction, basic
access authentication is a method for an HTTP user agent to
provide a user name andpassword when
making a request.

Contents

[hide]

1 Features
2 Security
3 Protocol

3.1 Server
side
3.2 Client
side

4 See
also
5 References
and notes

Features[edit]

HTTP Basic authentication (BA) implementation is the simplest technique for enforcing access
controls to web resources because it doesn't require cookies, session
identifierand login pages. Rather, HTTP Basic authentication uses static, standard fields in the HTTP
header which means that no handshakes have to be done
in anticipation.

Security[edit]

The BA mechanism provides no confidentiality protection
for the transmitted credentials. They are merely encoded with Base64 in transit, but not encrypted or hashed in
any way. Basic Authentication is, therefore, typically used over HTTPS.
Because the BA field has to be sent in the header of each HTTP request, the web
browser needs to cache credentials for a reasonable period of time to avoid constantly prompting the user for their username and password. Caching policy differs between browsers. Microsoft
Internet Explorer by default caches them for 15 minutes.[1]
HTTP does not provide a method for a web server to instruct
the client to "log out" the user. However, there are a number of methods to clear cached credentials in certain web browsers. One of them is redirecting the user to a URL on the same domain containing credentials that are intentionally incorrect.
Unfortunately, this behavior is inconsistent between various browsers and browser versions.[2] Microsoft
Internet Explorer offers a dedicated JavaScript method to clear cached credentials:[3]

 <script>document.execCommand('ClearAuthenticationCache', 'false');</script>

Protocol[edit]

Server side[edit]

When the server wants the user agent to authenticate itself towards the server, it must respond appropriately to unauthenticated requests.
Unauthenticated requests should return a response whose header contains a HTTP 401 Not Authorized status[4] and
a WWW-Authenticate field.[5]
The WWW-Authenticate field for basic authentication (used most often) is constructed as following:[6]

WWW-Authenticate: Basic realm="nmrs_m7VKmomQ2YM3:"

Client side[edit]

When the user agent wants to send the server authentication credentials it may use the Authorization field.[7]
The Authorization field is constructed as follows:[8]

Username and password are combined into a string "username:password". Note that username cannot contain the ":" character.[9]
The resulting string is then encoded using the RFC2045-MIME variant of Base64,
except not limited to 76 char/line[10]
The authorization method and a space i.e. "Basic " is then put before the encoded string.

For example, if the user agent uses 'Aladdin' as the username and 'open sesame' as the password then the field is formed as follows:

Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==

See also[edit]

Digest access authentication
HTTP header
TLS-SRP, an alternative if one wants to avoid transmitting a password-equivalent
to the server (even encrypted, like with TLS).

References and notes[edit]

Jump
up^ "Basic
Authentication". Microsoft. 2005. Retrieved October 17, 2014.
Jump
up^ "Is
there a browser equivalent to IE's ClearAuthenticationCache?". StackOverflow. Retrieved March 15, 2013.
Jump
up^ "IDM_CLEARAUTHENTICATIONCACHE command
identifier". Microsoft. Retrieved March 15, 2013.
Jump
up^ http://tools.ietf.org/html/rfc1945#section-11
Jump
up^ http://tools.ietf.org/html/rfc1945#section-10.16
Jump
up^ http://tools.ietf.org/html/rfc1945#section-11.1
Jump
up^ http://tools.ietf.org/html/rfc1945#section-10.2
Jump
up^ http://tools.ietf.org/html/rfc1945#section-10.2
Jump
up^ http://tools.ietf.org/html/rfc2617#section-2
Jump
up^ http://tools.ietf.org/html/rfc1945#section-11

Categories:

Hypertext Transfer Protocol

Computer access control protocols