[exim-dev] [Bug 3037] New: Broken pipe in transport filter

https://bugs.exim.org/show_bug.cgi?id=3037

            Bug ID: 3037
           Summary: Broken pipe in transport filter
           Product: Exim
           Version: 4.97
          Hardware: x86
                OS: Linux
            Status: NEW
          Severity: bug
          Priority: medium
         Component: Transports
          Assignee: unallocated@???
          Reporter: hi@???
                CC: exim-dev@???

Created attachment 1448
--> https://bugs.exim.org/attachment.cgi?id=1448&action=edit
spool file

Hi there,

Exim throws Broken pipe for any email going through transport filter while it's
body size exceeds ARG_MAX, around 2MB in centOS.

I couldn't find way to increase ARG_MAX except through recompiling the kernel
which I can't do it for now.

I performed chunking during echo call from bash script to EXIM transport filter
to bypass the ARG_MAX limitation yet it seems the call of /bin/cat handling by
EXIM is again tied to the ARG_MAX and causes broken pipe.

I tried to call /bin/cat in EXIM configuration directly to a file which
contains the content of email, and I get the same, it throws broken pipe error.

# local-email header condition it's irrelevant to the bug
transport_filter = /bin/bash -c '${if
def:h_x-local-email:{/usr/exim/modifyemail.sh $message_exim_id}{/bin/cat}}'


The output I get in log and debug mode that's relevant to the issue it's the
following, as per my skimming skills, I'm not 100% sure but I looked at the
debugging verbose output and log selector with all flag carefully and couldn't
see anything else that can be considered relevant. In case there is, please let
me know.

2023-10-10 12:48:29 1qptUJ-000000006kF-23YV H=alt2.gmail-smtp-in.l.google.com
[173.194.202.27]: alt2.gmail-smtp-in.l.google.com [173.194.202.27]: Broken pipe
2023-10-10 12:48:33 1qptUJ-000000006kF-23YV H=alt4.gmail-smtp-in.l.google.com
[142.250.115.27]: alt4.gmail-smtp-in.l.google.com [142.250.115.27]: Broken pipe
2023-10-10 12:48:33 1qptUJ-000000006kF-23YV == dailyzakaria@???
R=dnslookup T=remote_smtp defer (32): Broken pipe
H=alt4.gmail-smtp-in.l.google.com [142.250.115.27]:
alt4.gmail-smtp-in.l.google.com [142.250.115.27]


If I send the same email without using transport filter or without over 2MB
attachment, it's sent successfully with no problem whatsoever.

Also, I run EXIM 4.97 RC2

Also, I wonder if there is anything else I can do in case it wasn't a bug?

Any feedback would be very much appreciated.

Looking forward, with thanks.

Zakaria.

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