in certain configurations, under very unlikely conditions (which are
practically impossible to control remotely), we'd overflow ranges[].
in a typical gcc build, the values (which are also practically
impossible to control remotely) would be written at the end of buf[],
which would be rather harmless, as only a tiny part of buf is used
subsequently. so i'm not classifying this as a security issue.
amends 77acc268.
this wasn't really a security problem, as the name mapping we actually
do does not change the string length, and the iteration was already
safe after the literal length fix, but it's still better to catch weird
input.
we didn't limit the 32-bit size of literals so far, which, given that we
use int-sized lengths & offsets, permitted all kinds of buffer
overflows. malicious/compromised servers may have been able to exploit
this. actual email senders would be constrained by size limits for
delivered mails, and to cause more than a crash they'd have to predict
the exact size of the final message.
we now limit to 2GB, which, given that we use unsigned ints since
e2d3b4d55 (v1.4.0), gives the handlers downstream plenty of headroom.
an alternative would have been using 64-bit offsets, but this seems like
major overkill, even if IMAP4rev2 recently mandated it (we talk only
IMAP4rev1, so we can ignore it).
the AUTHENTICATE command may get insanely long for GSSAPI when SASL-IR
is available. instead of growing the buffers each time someone hits the
limit (as done in f7cec306), remove the limitation altogether.
imap_vprintf() still contains a fixed-size buffer which could overflow
when really long strings (e.g., mailbox names) need to be quoted. this
seems very unlikely, so we'll deal with it if someone actually hits it.
REFMAIL: 87sg1qxdye.fsf@cern.ch
if the code was sent in response to anything but a STORE, we'd overwrite
a data pointer in one of our imap_cmd subclasses, an allocator data
structure, or the start of the next allocation, with an int that was
completely under the server's control. it's plausible that this could be
exploited for remote code execution.
to avoid this, we could ensure that the object is of the right type
prior to casting, by using a new flag in the parameter block. but it's
easier to just dispose of the out_uid field altogether and reuse the uid
field that is present in the parameter block anyway, but was used only
for FETCH commands so far.
this problem was found by Lukas Braun <koomi@moshbit.net> using a
fuzzer.
while it's technically reasonable to expect the user to match the
server's casing of INBOX if they set Path, this might come as a
surprise to those who know that the IMAP INBOX is case-insensitive.
so tolerate any casing instead. as a minor side effect, we'd now even be
able to deal with a server using different casing in NAMESPACE and LIST.
in particular, '..' in the name could be used to escape the Path/Inbox
of a Maildir Store, which could be exploited for stealing or deleting
data, or staging a (mild) DoS attack.
fastmail sends flags containing ']' in PERMANENTFLAGS, which is formally
illegal. however, if we parse the embedded list before looking for the
response code's closing ']', things work out fine.
as a side effect we won't complain about similarly or completely
malformed response codes we don't recognize at all, which may or may not
be considered an improvement ...
on error, parse_imap_list() needs to reset the nesting level in the
state, as imap_socket_read() uses that as an indicator whether list
parsing is ongoing.
while the spec says that the server SHOULD not send FETCH responses
about STORE FLAGS when .SILENT is used, at least gmail and fastmail seem
to do it nonetheless. also, in case of concurrent flag updates on the
affected messages such responses can be legitimately sent.
in earlier versions of mbsync this would lead to duplicate messages
piling up in the store, though that would pose no problem at that point.
The SASL library will refuse to use the EXTERNAL module when no auth id
is set a priori.
Tested to work with Dovecot, using TLS client certificates for
authentication.
to test async operation of the syncing core while using the synchronous
maildir driver, we add a mode to the proxy driver where it queues
callback invocations to the next main loop iteration.
the struct declarations got uglier, but their usage requires a lot fewer
explicit references to the parent struct (though some are added where
using the derived struct is more practical now).
we also use something i'd term "covariant members": derivatives of
store_t also reference derivatives of store_conf_t, etc., which
drastically cuts down the number of casts.
fwiw, to achieve this with "proper" inheritance in C++, we'd use
covariant getter functions which hide the still existing casts.
C11 is almost a decade old now, and compilers supported that feature
even longer than that, so i don't expect this to be a problem.
that's mostly hypothetical, but let's not make assumptions.
this also adds EXPUNGE response handling to make total_msgs reliable. in
principle, this affects the post-SELECT UIDNEXT fallback as well, but
there the racing window is so short that this barely improves anything.
amends 94022a67.
the uidnext query following message stores can be interleaved with
message fetches. that means that we cannot rely on the 1st command in
flight being that query. but instead of iterating over all commands in
flight, move the uidnext query flag to imap_store (and make sure to
check for the presence of a message body before testing it) - this
avoids the loop and an extra byte in every command.
this also makes it clear that the query is mutually exclusive with
loading messages (the untagged responses are not distinguishable).
delay reporting success of STORE FLAGS until a subsequent CHECK
succeeds.
this fixes (inverse flag change propagation) and (deletes not being
propagated) after an interruption due to prematurely logged flag
updates.
we need to pass a different "boundary" UID to driver_t::load_box() for
every OPEN_* flag that queries a partial range:
- OPEN_FIND refers to messages newer than all we know about
- OPEN_OLD_IDS refers to messages which are paired
- OPEN_{OLD,NEW}_SIZE refers to messages (not) above the committed
boundary of already propagated messages
we treated the 3rd like the 2nd, which was just wrong - the actual
boundary may be lower or higher, so we'd produce wrong results when
MaxSize was set and only one of New and ReNew was requested.
this is better than using PassCmd, as it allows the keychain manager to
identify the calling process and therefore use a selective whitelist.
unlike in the now removed example, we use an "internet password" for the
imap protocol, rather than a "generic password" - this seems more
appropriate.
based on a patch by Oliver Runge <oliver.runge@gmail.com>
It was already possible to retrieve passwords from arbitrary commands.
But this goes only half the way to allowing automated derivation of
login credentials, as some environments may also have different user
names based on the system. Therefore, add the UserCmd option to
complement PassCmd.
Based on a patch series by Patrick Steinhardt <ps@pks.im>
