On 4 Mar 2019, at 6:58, Vsevolod Stakhov wrote:
Hello,
I'm trying to debug one issue with the milter interface in Postfix. I
want to remove multiple headers with the same name, for example:
X-Spam-Flag: No
X-Spam-Flag: No
X-Spam-Flag: Not really
X-Spam-Flag: No
To do that, I track headers on header phase and track numbers for each
header. For this particular sample, I will have some map like
`X-Spam-Flag = 4`.
After end-of-data stage, I send multiple `CHGHEADER` ('m') commands
with
header value equal to a empty string:
change/insert header command pos = 1 - "X-Spam-Flag"=""
change/insert header command pos = 2 - "X-Spam-Flag"=""
change/insert header command pos = 3 - "X-Spam-Flag"=""
change/insert header command pos = 4 - "X-Spam-Flag"=""
Literally, my code (Rspamd) sends CHGHEADER command 4 times. After
message being processed, I can see that Postfix removes 2 of 4
`X-Spam-Flag` headers.
I have tested something else after that. I have tried to add more
headers where names are equal and non equal. It seems that all odd
headers are not removed.
I have not tested this, but your description is consistent with the
Milter interface acting immediately on your deletion of the indexed
header instance and collapsing the array, modifying which index points
to which data. So, after you delete the 1st "X-Spam-Flag" header, you
now have 3 instances remaining, with the new 1st instance being the
former 2nd instance. This way, if you delete the 2nd instance, you are
deleting what WAS the 3rd.
In any event, the results described also imply that you are not
bothering to check for errors when you call a library routine that CAN
return an error. Again, I have not tested this but I know that chgheader
CAN return an error and would expect it to do so when passed an
out-of-range index.
Return values exist for good reasons. One of them is to help novice
coders avoid public embarrassment.
--
Bill Cole
b...@scconsult.com or billc...@apache.org
(AKA @grumpybozo and many *@billmail.scconsult.com addresses)
Available For Hire: https://linkedin.com/in/billcole
