Environment: Exim 4.51 on RedHat Enterprise Linux 3 on a Dell 1550 server.
Synopsis: Data from an LDAP lookup remains in the address_data
variable, even after a subsequent LDAP lookup fails.
Details: When testing my mail forwarding router, I discovered that if a
user specifies a bad local forwarding address in their LDAP record,
incoming mail just gets delivered to the original recipient and no error
message is generated. Here's how it happens: On the first pass through
the routers, the recipient's data is retrieved from LDAP by a router
which stores it in address_data and then declines so that the following
routers can process it. This data includes, among other things, their
mail directory and forwarding address, if set. These data items are
extracted and used by subsequent routers, including my forwarding
(redirect) router. If the user has specified a local forwarding
address, a second pass through the routers begins. If the specified
forwarding address is invalid, the LDAP lookup will fail, but the
address_data variable is not cleared. My forwarding router uses the
original address_data and redirects the mail to the bad address a second
time. On the third pass through the routers, the LDAP lookup fails
again, but the forwarding router detects the loop and declines. My
local delivery router then uses the mail directory data from the
original LDAP lookup and stores the message in the original recipients
directory. No forwarding gets done, no error gets generated, nothing.
Solution: Clearing the old data out of address_data when a lookup fails
seems to be the obvious fix, but I can see that this change in behaviour
might impact other sites. Another option would be to add a new option
to the redirect router to explicitly clear the address_data variable
before starting another pass through the routers. Also, I suppose I
could put a new router directly before the one that does the LDAP
lookup, which would just clear the address_data and then decline.
Questions: Is this a bug / mis-feature in address_data handling? Has
the handling of address_data changed recently? - I would have sworn this
worked in a previous 4.x version of Exim. Is there a better way to
process mail forwarding?
Russ
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Russell D. Wilton E Mail: WILTON@???
Internet Services Manager Voice: (403) 329-2525
University of Lethbridge FAX: (403) 382-7108
4401 University Drive Lethbridge, Alberta, CANADA T1K 3M4
