[Dovecot] 1.0.alpha3 plaintext authentication problem

[Timo Sirainen]

On Mon, 2005-10-10 at 07:21 +0900, Sergey Redin wrote:
> dovecot: Oct 10 02:03:28 Info: pop3-login: Authenticate PLAIN failed: 
> Unsupported authentication mechanism.: method=PLAIN, rip=82.146.63.23, 
> lip=82.146.50.34

>   We see here two successfull logins with PLAIN and then suddenly PLAIN 
> becomes unsupported.

Strange. I tried to look at possible reasons for that in code, but
didn't really see anything. When pop3-login process starts, it first
connects to dovecot-auth using UNIX socket. dovecot-auth tells what
mechanisms are available. I think the only way the above error could
happen is if dovecot-auth didn't return the mechanism list.

You don't happen to have multiple dovecot-auth processes running at the
same time for some reason?

Also maybe this patch will show a different error message? I'll commit
it to CVS too:

diff -u -r1.13 auth-server-connection.c
--- src/lib-auth/auth-server-connection.c	14 Aug 2005 20:39:22 -0000	1.13
+++ src/lib-auth/auth-server-connection.c	28 Oct 2005 17:08:45 -0000
@@ -107,6 +107,11 @@
 	conn->available_auth_mechs_count =
 		conn->auth_mechs_buf->used / sizeof(struct auth_mech_desc);
 
+	if (conn->available_auth_mechs_count == 0) {
+		i_error("BUG: Authentication server returned no mechanisms");
+		return FALSE;
+	}
+
 	conn->handshake_received = TRUE;
 	conn->client->conn_waiting_handshake_count--;
 	update_available_auth_mechs(conn);

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