Usage of nsIHttpChannel Interface

 Upon receipt of a server challenge, this function is called to determine
 whether or not the current user identity has been rejected.  If true,
 then the user will be prompted by the channel to enter (or revise) their
 identity.  Following this, generateCredentials will be called.

 If the IDENTITY_IGNORED auth flag is set, then the aInvalidateIdentity
 return value will be ignored, and user prompting will be suppressed.

 @param aChannel
        the http channel that received the challenge.
 @param aChallenge
        the challenge from the WWW-Authenticate/Proxy-Authenticate
        server response header.  (possibly from the auth cache.)
 @param aProxyAuth
        flag indicating whether or not aChallenge is from a proxy.
 @param aSessionState
        see description below for generateCredentials.
 @param aContinuationState
        see description below for generateCredentials.
 @param aInvalidateIdentity
        return value indicating whether or not to prompt the user for a
        revised identity.

void challengeReceived(in nsIHttpChannel aChannel, in string aChallenge, in boolean aProxyAuth, inout nsISupports aSessionState, inout nsISupports aContinuationState, out boolean aInvalidatesIdentity)

 Called to generate the authentication credentials for a particular
 server/proxy challenge.  This is the value that will be sent back
 to the server via an Authorization/Proxy-Authorization header.

 This function may be called using a cached challenge provided the
 authenticator sets the REUSABLE_CHALLENGE flag.

 @param aChannel
        the http channel requesting credentials
 @param aChallenge
        the challenge from the WWW-Authenticate/Proxy-Authenticate
        server response header.  (possibly from the auth cache.)
 @param aProxyAuth
        flag indicating whether or not aChallenge is from a proxy.
 @param aDomain
        string containing the domain name (if appropriate)
 @param aUser
        string containing the user name
 @param aPassword
        string containing the password
 @param aSessionState
        state stored along side the user's identity in the auth cache
        for the lifetime of the browser session.  if a new auth cache
        entry is created for this challenge, then this parameter will
        be null.  on return, the result will be stored in the new auth
        cache entry.  this parameter is non-null when an auth cache entry
        is being reused.
 @param aContinuationState
        state held by the channel between consecutive calls to
        generateCredentials, assuming multiple calls are required
        to authenticate.  this state is held for at most the lifetime of
        the channel.

string generateCredentials(in nsIHttpChannel aChannel, in string aChallenge, in boolean aProxyAuth, in wstring aDomain, in wstring aUser, in wstring aPassword, inout nsISupports aSessionState, inout nsISupports aContinuationState)

 Called when a redirect occurs due to a HTTP response like 302.  The
 redirection may be to a non-http channel.

 @return failure cancels redirect

void onRedirect(in nsIHttpChannel httpChannel, in nsIChannel newChannel)