| A Proxy-Authenticate header field value contains an authentication
challenge. When a UAC sends a request to a proxy server, the proxy server
MAY authenticate the originator before the request is processed. If no
credentials (in the Proxy-Authorization header field) are provided in the
request, the proxy can challenge the originator to provide credentials by
rejecting the request with a 407 (Proxy Authentication Required) status
code. The proxy MUST populate the 407 (Proxy Authentication Required)
message with a Proxy-Authenticate header field value applicable to the
proxy for the requested resource. The field value consists of a challenge
that indicates the authentication and parameters applicable to the proxy
for this RequestURI.
Note - Unlike its usage within HTTP, the ProxyAuthenticateHeader must be
passed upstream in the Response to the UAC. In SIP, only UAC's can
authenticate themselves to proxies.
Proxies MUST NOT add values to the Proxy-Authorization header field. All
407 (Proxy Authentication Required) responses MUST be forwarded upstream
toward the UAC following the procedures for any other response. It is the
UAC's responsibility to add the Proxy-Authorization header field value
containing credentials for the realm of the proxy that has asked for
authentication.
When the originating UAC receives the 407 (Proxy Authentication Required)
it SHOULD, if it is able, re-originate the request with the proper
credentials. It should follow the same procedures for the display of the
"realm" parameter that are given above for responding to 401. If no
credentials for a realm can be located, UACs MAY attempt to retry the
request with a username of "anonymous" and no password (a password of "").
The UAC SHOULD also cache the credentials used in the re-originated request.
For Example:
Proxy-Authenticate: Digest realm="jcp.org",
domain="sip:ss1.duke.com", qop="auth",
nonce="f84f1cec41e6cbe5aea9c8e88d359", opaque="", stale=FALSE,
algorithm=MD5
See Also: Parameters
See Also: ProxyAuthorizationHeader
author:
BEA Systems, NIST
version:
1.2 |