=encoding utf-8

=head1 NAME

ngx_mail_auth_http_module - Module ngx_mail_auth_http_module




=head1 Directives

=head2 auth_http


B<syntax:> auth_http I<I<C<URL>>>



B<context:> I<mail>


B<context:> I<server>





Sets the URL of the HTTP authentication server.
The protocol is described below.







=head2 auth_http_header


B<syntax:> auth_http_header I<I<C<header>> I<C<value>>>



B<context:> I<mail>


B<context:> I<server>





Appends the specified header to requests sent 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";









=head2 auth_http_pass_client_cert


B<syntax:> auth_http_pass_client_cert I<C<on> E<verbar> C<off>>


B<default:> I<off>


B<context:> I<mail>


B<context:> I<server>



This directive appeared in version 1.7.11.





Appends the C<Auth-SSL-Cert> header with the
L<client|ngx_mail_ssl_module>
certificate in the PEM format (urlencoded)
to requests sent to the authentication server.







=head2 auth_http_timeout


B<syntax:> auth_http_timeout I<I<C<time>>>


B<default:> I<60s>


B<context:> I<mail>


B<context:> I<server>





Sets the timeout for communication with the authentication server.







=head1 Protocol



The HTTP protocol is used to communicate with the authentication server.
The data in the response body is ignored, the information is passed only in
the headers.





Examples of requests and responses:





Request:

    
    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


Good response:

    
    HTTP/1.0 200 OK
    Auth-Status: OK
    Auth-Server: 198.51.100.1
    Auth-Port: 143


Bad response:

    
    HTTP/1.0 200 OK
    Auth-Status: Invalid login or password
    Auth-Wait: 3







If there is no C<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 C<Auth-Wait> header after 10-20 attempts
(the attempt number is passed in the C<Auth-Login-Attempt>
header).





When the APOP or CRAM-MD5 are used, request-response will look as follows:

    
    GET /auth HTTP/1.0
    Host: localhost
    Auth-Method: apop
    Auth-User: user
    Auth-Salt: <238188073.1163692009@mail.example.com>
    Auth-Pass: auth_response
    Auth-Protocol: imap
    Auth-Login-Attempt: 1
    Client-IP: 192.0.2.42
    Client-Host: client.example.org


Good response:

    
    HTTP/1.0 200 OK
    Auth-Status: OK
    Auth-Server: 198.51.100.1
    Auth-Port: 143
    Auth-Pass: plain-text-pass







If the C<Auth-User> header exists in the response,
it overrides the username used to authenticate with the backend.





For the SMTP, the response additionally takes into account
the C<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 C<Auth-Status> header.





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,
the 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: <postmaster@mail.example.com>







For the SSLE<sol>TLS client connection (1.7.11),
the C<Auth-SSL> header is added, and
C<Auth-SSL-Verify> will contain
the result of client certificate verification, if
L<enabled|ngx_mail_ssl_module>:
“C<SUCCESS>”, “C<FAILED>”, and
“C<NONE>” if a certificate was not present.
When the client certificate was present,
its details are passed in the following request headers:
C<Auth-SSL-Subject>, C<Auth-SSL-Issuer>,
C<Auth-SSL-Serial>, and C<Auth-SSL-Fingerprint>.
If L</auth_http_pass_client_cert> is enabled,
the certificate itself is passed in the
C<Auth-SSL-Cert> header.
The request will look as follows:

    
    GET /auth HTTP/1.0
    Host: localhost
    Auth-Method: plain
    Auth-User: user
    Auth-Pass: password
    Auth-Protocol: imap
    Auth-Login-Attempt: 1
    Client-IP: 192.0.2.42
    Auth-SSL: on
    Auth-SSL-Verify: SUCCESS
    Auth-SSL-Subject: /CN=example.com
    Auth-SSL-Issuer: /CN=example.com
    Auth-SSL-Serial: C07AD56B846B5BFF
    Auth-SSL-Fingerprint: 29d6a80a123d13355ed16b4b04605e29cb55a5ad






