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[bug-mailutils] TLS certificate checking and enforcement for mailutils c
Daniel Kahn Gillmor
[bug-mailutils] TLS certificate checking and enforcement for mailutils client programs
Fri, 21 Jul 2006 17:13:21 -0400
Another question about secure connection techniques:
i see that mail has a --tls=BOOL option for connecting with
TLS-capable servers. What i can't tell is how the TLS certificates
are verified. Without proper certificate validation, TLS connections
are vulnerable to man-in-the-middle attacks from an active attacker
(one who can intercept and modify traffic).
Usually certificate validation/verification is handled by specifying a
file or directory containing the certificates of trusted X509
certificate authorities. the mailutils imap4d and pop3d both
implement this approach with their --ssl-cafile options . However,
there are many more setups with server-side certificates these days
than client-side certificates. So certificate checks are probably
even more important from the other direction: the client verifying the
but /usr/bin/mail (at least verion 0.94) doesn't seem to support a
--ssl-cafile option, and i don't see any reference to a comparable
option for this program.
Furthermore, it's not clear to me how to *force* TLS from the client's
point of view. That is, you should be able to instruct a TLS-aware
client to terminate the connection if the TLS negotiation fails, so
that you don't risk exposing traffic over an insecure connection.
>From the documentation, it's not clear that the --tls option allows
for this kind of rigor.
Does one of the folks on this list who understands mailutils better
than i do care to explain the situation? If mailutils isn't capable
of these distinctions, are they desired features?
Thanks for the great software,
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