On 28/08/2020 01:11, Alec Moskvin wrote:
Hello,
When connecting to Exim 4.94, dovecot submission logs this warning:
dovecot[25235]: submission(alec)<25347><QNydV8+t+oMKAgAF>: Warning: smtp-client: conn localhost:25 ([::1]:25) [1]: Received invalid EHLO response line: Unexpected character in EHLO keyword
Looks like it doesn't like the underscore in "X_PIPE_CONNECT", since it's neither "isalnum" nor a dash [1]:
1598480923.401085 220 myhostname ESMTP Exim 4.94 Wed, 26 Aug 2020 18:28:43 -0400 1598480923.401906 250-myhostname Hello localhost [::1] 1598480923.401906 250-SIZE 52428800 1598480923.401906 250-8BITMIME 1598480923.401906 250-PIPELINING 1598480923.401906 250-X_PIPE_CONNECT 1598480923.401906 250-CHUNKING 1598480923.401906 250-STARTTLS 1598480923.401906 250 HELP 1598480923.409242 250 OK 1598480923.434743 250 Accepted 1598480923.578335 250- 511 byte chunk, total 511 1598480923.578335 250 OK id=1kB3uN-0006ar-HU
Adding the line "pipelining_connect_advertise_hosts =" to Exim's config fixes the issue by disabling X_PIPE_CONNECT.
Is this a bug in Exim or is Dovecot being too strict?
Thanks, Alec
[1] https://github.com/dovecot/core/blob/2.3.11.3/src/lib-smtp/smtp-syntax.c#L25...
Dovecot follows the standards as strict as reasonable, with some workarounds for the bad code out there. Exim is in violation of RFC 5321, Section 4.1.1.1:
ehlo-ok-rsp = ( "250" SP Domain [ SP ehlo-greet ] CRLF )
/ ( "250-" Domain [ SP ehlo-greet ] CRLF
*( "250-" ehlo-line CRLF )
"250" SP ehlo-line CRLF )
ehlo-greet = 1*(%d0-9 / %d11-12 / %d14-127)
; string of any characters other than CR or LF
ehlo-line = ehlo-keyword *( SP ehlo-param )
ehlo-keyword = (ALPHA / DIGIT) *(ALPHA / DIGIT / "-")
; additional syntax of ehlo-params depends on
; ehlo-keyword
ehlo-param = 1*(%d33-126)
; any CHAR excluding <SP> and all
; control characters (US-ASCII 0-31 and 127
; inclusive)The underscore is not supported by the standard (only dash).
Is Exim doing this by default? In that case we may need to add a workaround for it.
Regards,
Stephan.