this is actually potentially counterproductive, as people who have set
SSLVersions and fail to adjust it will _lose_ tls 1.3 support. however,
without the option being there, people (incorrectly) believe that tls
1.3 is not supported.
Some distributions (e.g. Fedora) added support for system wide crypto
policies. This is supported in most common crypto libraries including
OpenSSL. Applications can override this policy using their own cipher
string. This commit adds support for specifying the cipher string in
the mbsync configuration.
For example, to exclude Diffie-Hellman, the user can specify
CipherString "DEFAULT:!DH"
in the IMAP Account's configuration.
there is no reason not to, and debian even disabled 1.0 globally,
because it's (theoretically) too insecure in some contexts (BEAST
attack).
in the compat wrapper, the UseTLSv1 option has been re-interpreted as
v1.x, to avoid adding new options.
do that by wrapping the actual stores into proxies.
the proxy driver's code is auto-generated from function templates, some
parameters, and the declarations of the driver functions themselves.
attempts to do it with CPP macros turned out to be a nightmare.
turns out i misread the spec in a subtle way: while all other folders
are physically nested under INBOX, the IMAP view puts them at the same
(root) level. to get them shown as subfolders of INBOX, they need to
have _two_ leading dots.
this also implies that the Maildir++ mode has no use for a Path, so
reject attempts to specify one.
the legacy style is a poorly executed attempt at Maildir++, so introduce
the latter for the sake of completeness. but most users will probably
just want to use subfolders without any additional dots.
the PassCmd will be typically non-interactive (or it will use a gui
password agent), so starting a new line just makes the progress counter
uglier. so make it configurable and default to no line break.
- the old meaning of -V[V] was moved to -D{n|N}, as these are really
debugging options.
- don't print the info messages by default; this can be re-enabled with
the -V switch, and is implied by most debug options (it was really
kind of stupid that verbose/debug operation disabled these).
- the sync algo/state debugging can be separately enabled with -Ds now.
propagating many messages from a fast store (typically maildir or a
local IMAP server) to a slow asynchronous store could cause gigabytes of
data being buffered. avoid this by throttling fetches if the target
context reports memory usage above a configurable limit.
REFMAIL: 9737edb14457c71af4ed156c1be0ae59@mpcjanssen.nl
... for windows fs compatibility.
the maildir-specific InfoDelimiter inherits the global FieldDelimiter
(which affects SyncState), based on the assumption that if the sync
state is on a windows FS, the mailboxes certainly will be as well, while
the inverse is not necessarily true (when running on unix, anyway).
REFMAIL: <CA+m_8J1ynqAjHRJagvKt9sb31yz047Q7NH-ODRmHOKyfru8vtA@mail.gmail.com>
patch initially by Jack Stone <jwjstone@fastmail.fm>,
cleaned up by Jan Synacek <jsynacek@redhat.com>,
... and then almost completely rewritten by me. ^^
RequireCRAM (another fairly stupid "use if available" option) is now
deprecated. instead, the AuthMech option can be used to give a precise
list of acceptable authentication mechanisms (which is currently "a bit"
short). in particular, this allows *not* using CRAM-MD5 even if it's
available.
the combinations of the various options made quite a mess. additionally,
'RequireSSL no' is inherently insecure - "use SSL if available" is plain
stupid.
the old options are still accepted, but will elicit a warning.
such connections don't support STARTTLS. that is reasonable, as whatever
makes the connection preauthenticated (typically a Tunnel used to launch
imapd via a shell login) must already rely on the connection's security.
consequently, we would not try to use STARTTLS with such connections.
unfortunately, we'd also skip the RequireSSL check as a side effect.
this means that a rogue server (via a MITM attack) could simply offer a
preauthenticated connection to make us not use SSL, and thus bypass
server authentication. as a result, we could send potentially sensitive
data to the attacker:
- with Patterns used, we would send a LIST command which reveals the
remote Path setting. this isn't very useful to an attacker. also, IMAP
Accounts usually rely on the server-provided NAMESPACE to start with.
- with Create enabled for the remote Store, we would upload messages
from newly appeared local folders. this isn't a very likely situation,
unless the attacker manages to convince the victim to move/copy
interesting mails to a new folder right before the attack.
- with Expunge enabled for the local Store, previously synchronized
folders would be wiped. however, this would require the attacker to
know the correct UIDVALIDITY of each remote folder, which would
require incredible luck or convincing the victim to disclose them.
the first mismatch would likely tip off the victim.
in practice, someone with the level of technical and social engineering
skills required for this attack would very likely find more attractive
attack vectors. therefore, i don't consider this a particularly serious
issue.
configurations with UseIMAPS enabled or using a secure Tunnel were not
affected to start with.
a side effect of this fix is that most users of Tunnel will now need to
explicitly set RequireSSL to false.
an alternative approach would be defaulting all SSL-related settings to
off when Tunnel is used. this would be too invasive for a patch release,
but i'll consider it for 1.2.
see also CVE-2014-2567 for the Trojita MUA.
unlike the isync wrapper, mbsync does not have a default for the IMAP
user. the remote user seldomly matches the local one, so "forwarding" it
is more confusing than helpful.
CCMAIL: 744389@bugs.debian.org
as the named boxes are the same on both sides, they logically make
sense only when the channel is in that mode anyway, which is the case
when using patterns.
