remailer security, sendmail
I just read an interesting post on alt.hackers. Apparently you can figure out who's sending mail to who by repeatedly running the command /usr/lib/sendmail -bp. I just tested this out and it *seems* to work, as does running /usr/ucb/mailq repeatedly. How's that for an obscure feature? Does anyone run a remailer on a multi-user machine where sendmail is used? Is this sendmail feature a problem? If so, how would one fix it? (write a wrapper for sendmail? but that requires root access *sigh*) Am I missing something? ------------------------------------------------------------------------------- David Wagner dawagner@princeton.edu
-----BEGIN PGP SIGNED MESSAGE----- David Wagner writes:
I just read an interesting post on alt.hackers. Apparently you can figure out who's sending mail to who by repeatedly running the command /usr/lib/sendmail -bp. I just tested this out and it *seems* to work, as does running /usr/ucb/mailq repeatedly. How's that for an obscure feature?
Well, since it's in the first couple of man pages for sendmail, it's not very obscure :] I would have expected better material from alt.hackers....
Does anyone run a remailer on a multi-user machine where sendmail is used?
Yes; we had some discussion about this here a few weeks ago. I, for one, am doing just that.
Is this sendmail feature a problem? If so, how would one fix it? (write a wrapper for sendmail? but that requires root access *sigh*) Am I missing something?
As I understand sendmail, it only sticks outgoing messages in the queue if you tell it to do so. Otherwise they can be sent pre-emptively or in the background. This can be specified on the command line: dx Set the delivery mode to x. Delivery modes are `i' for interactive (synchronous) delivery, `b' for background (asynchronous) delivery, and `q' for queue only - that is, actual delivery is done the next time the queue is run. In any case, this doesn't provide any information about incoming mail. Besides, with ps -aux you get to see all the invocations of sendmail, and the invocations of pgp, and so on. I'd worry more about that than about the sendmail queue. Convincing sysadmins that they should somehow disable the -a option on ps doesn't sound like an easy task to me. All this ultimately argues for placing terminal remailers on private machines, which I think we've agreed is a Good Thing. -L. Futplex McCarthy; use "Subject: remailer-help" for an autoreply PGP key by finger or server; "Better watch what you say, or they'll be calling you a radical...a liberal" --Supertramp "[CIA/KGB mole Aldrich Ames] took information in shopping bags out the front door" --miscellaneous Congressperson -----BEGIN PGP SIGNATURE----- Version: 2.6.1 iQCVAwUBLs/6/2f7YYibNzjpAQFU2wP/Vq3k6/S8S34cdd0DCcH17yYBIfe1hP5K nX//G/OE3b1yJe7k7uql8aKOyf8xMqd5o3UQY/o0qL7Kl+rHiMP6GEd+QUZunHkF AyrjqS9nrgfls9klmXWVO3tjxllBW6ZZXuhQti4h0dMU+Kj6mu9Wva+zLPqyoSIP lDpPV6t1FkE= =H70i -----END PGP SIGNATURE-----
participants (2)
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David A. Wagner -
L. McCarthy