Sets the URL of the HTTP authentication server. The protocol is described below.
Appends the specified header to requests to the authentication server. This header can be used as the shared secret to verify that the request comes from nginx. For example:
auth_http_header X-Auth-Key "secret_string";
The HTTP is used to communicate with the authentication server. The data in the response body is ignored, and the information is passed only in the headers.
Examples of requests and responses:
GET /auth HTTP/1.0 Host: localhost Auth-Method: plain # plain/apop/cram-md5 Auth-User: user Auth-Pass: password Auth-Protocol: imap # imap/pop3/smtp Auth-Login-Attempt: 1 Client-IP: 192.0.2.42 Client-Host: client.example.org
HTTP/1.0 200 OK Auth-Status: OK Auth-Server: 198.51.100.1 Auth-Port: 143
HTTP/1.0 200 OK Auth-Status: Invalid login or password Auth-Wait: 3
If there is no “Auth-Wait” header, an error will be returned and the connection will be closed. The current implementation allocates memory for each authentication attempt. The memory is freed only at the end of a session. Therefore, the number of invalid authentication attempts in a single session must be limited — the server must respond without the “Auth-Wait” header after 10-20 attempts (the attempt number is passed in the “Auth-Login-Attempt” header).
When the APOP or CRAM-MD5 are used, a request-response will look as follows.
GET /auth HTTP/1.0 Host: localhost Auth-Method: apop Auth-User: user Auth-Salt: <email@example.com> Auth-Pass: auth_response Auth-Protocol: imap Auth-Login-Attempt: 1 Client-IP: 192.0.2.42 Client-Host: client.example.org
HTTP/1.0 200 OK Auth-Status: OK Auth-Server: 198.51.100.1 Auth-Port: 143 Auth-Pass: plain-text-pass
If the “Auth-User” header exists in a response, it overrides the username used to authenticate with the backend.
For the SMTP, the response additionally takes into account the “Auth-Error-Code” header — if exists, it is used as a response code in case of an error. Otherwise, the 535 5.7.0 code will be added to the “Auth-Status”.
For example, if the following response is received from the authentication server:
HTTP/1.0 200 OK Auth-Status: Temporary server problem, try again later Auth-Error-Code: 451 4.3.0 Auth-Wait: 3
then the SMTP client will receive an error
451 4.3.0 Temporary server problem, try again later
If proxying SMTP does not require authentication, a request will look as follows.
GET /auth HTTP/1.0 Host: localhost Auth-Method: none Auth-User: Auth-Pass: Auth-Protocol: smtp Auth-Login-Attempt: 1 Client-IP: 192.0.2.42 Client-Host: client.example.org Auth-SMTP-Helo: client.example.org Auth-SMTP-From: MAIL FROM: <> Auth-SMTP-To: RCPT TO: <firstname.lastname@example.org>