| Commit message (Collapse) | Author | Age |
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When using GSSAPI encryption in non-blocking mode, libpq sometimes
failed with "GSSAPI caller failed to retransmit all data needing
to be retried". The cause is that pqPutMsgEnd rounds its transmit
request down to an even multiple of 8K, and sometimes that can lead
to not requesting a write of data that was requested to be written
(but reported as not written) earlier. That can upset pg_GSS_write's
logic for dealing with not-yet-written data, since it's possible
the data in question had already been incorporated into an encrypted
packet that we weren't able to send during the previous call.
We could fix this with a one-or-two-line hack to disable pqPutMsgEnd's
round-down behavior, but that seems like making the caller work around
a behavior that pg_GSS_write shouldn't expose in this way. Instead,
adjust pg_GSS_write to never report a partial write: it either
reports a complete write, or reflects the failure of the lower-level
pqsecure_raw_write call. The requirement still exists for the caller
to present at least as much data as on the previous call, but with
the caller-visible write start point not moving there is no temptation
for it to present less. We lose some ability to reclaim buffer space
early, but I doubt that that will make much difference in practice.
This also gets rid of a rather dubious assumption that "any
interesting failure condition (from pqsecure_raw_write) will recur
on the next try". We've not seen failure reports traceable to that,
but I've never trusted it particularly and am glad to remove it.
Make the same adjustments to the equivalent backend routine
be_gssapi_write(). It is probable that there's no bug on the backend
side, since we don't have a notion of nonblock mode there; but we
should keep the logic the same to ease future maintenance.
Per bug #18210 from Lars Kanis. Back-patch to all supported branches.
Discussion: https://postgr.es/m/18210-4c6d0b14627f2eb8@postgresql.org
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pqsecure_open_gss() includes a code path handling error messages with
v2-style protocol messages coming from the server. The client-side
buffer holding the error message does not force a NULL-termination, with
the data of the server getting copied to the errorMessage of the
connection. Hence, it would be possible for a server to send an
unterminated string and copy arbitrary bytes in the buffer receiving the
error message in the client, opening the door to a crash or even data
exposure.
As at this stage of the authentication process the exchange has not been
completed yet, this could be abused by an attacker without Kerberos
credentials. Clients that have a valid kerberos cache are vulnerable as
libpq opportunistically requests for it except if gssencmode is
disabled.
Author: Jacob Champion
Backpatch-through: 12
Security: CVE-2022-41862
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The critical issue fixed here is that if a GSSAPI-encrypted connection
is successfully made, pqsecure_open_gss() cleared conn->allow_ssl_try,
as an admittedly-hacky way of preventing us from then trying to tunnel
SSL encryption over the already-encrypted connection. The problem
with that is that if we abandon the GSSAPI connection because of a
failure during authentication, we would not attempt SSL encryption
in the next try with the same server. This can lead to unexpected
connection failure, or silently getting a non-encrypted connection
where an encrypted one is expected.
Fortunately, we'd only manage to make a GSSAPI-encrypted connection
if both client and server hold valid tickets in the same Kerberos
infrastructure, which is a relatively uncommon environment.
Nonetheless this is a very nasty bug with potential security
consequences. To fix, don't reset the flag, instead adding a
check for conn->gssenc being already true when deciding whether
to try to initiate SSL.
While here, fix some lesser issues in libpq's GSSAPI code:
* Use the need_new_connection stanza when dropping an attempted
GSSAPI connection, instead of partially duplicating that code.
The consequences of this are pretty minor: AFAICS it could only
lead to auth_req_received or password_needed remaining set when
they shouldn't, which is not too harmful.
* Fix pg_GSS_error() to not repeat the "mprefix" it's given multiple
times, and to notice any failure return from gss_display_status().
* Avoid gratuitous dependency on NI_MAXHOST in
pg_GSS_load_servicename().
Per report from Mikael Gustavsson. Back-patch to v12 where
this code was introduced.
Discussion: https://postgr.es/m/e5b0b6ed05764324a2f3fe7acfc766d5@smhi.se
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Both the backend and libpq leaked buffers containing encrypted data
to be transmitted, so that the process size would grow roughly as
the total amount of data sent.
There were also far-less-critical leaks of the same sort in GSSAPI
session establishment.
Oversight in commit b0b39f72b, which I failed to notice while
reviewing the code in 2c0cdc818.
Per complaint from pmc@citylink.
Back-patch to v12 where this code was introduced.
Discussion: https://postgr.es/m/20200504115649.GA77072@gate.oper.dinoex.org
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Fix assorted bugs in handling of non-blocking I/O when using GSSAPI
encryption. The encryption layer could return the wrong status
information to its caller, resulting in effectively dropping some data
(or possibly in aborting a not-broken connection), or in a "livelock"
situation where data remains to be sent but the upper layers think
transmission is done and just go to sleep. There were multiple small
thinkos contributing to that, as well as one big one (failure to think
through what to do when a send fails after having already transmitted
data). Note that these errors could cause failures whether the client
application asked for non-blocking I/O or not, since both libpq and
the backend always run things in non-block mode at this level.
Also get rid of use of static variables for GSSAPI inside libpq;
that's entirely not okay given that multiple connections could be
open at once inside a single client process.
Also adjust a bunch of random small discrepancies between the frontend
and backend versions of the send/receive functions -- except for error
handling, they should be identical, and now they are.
Also extend the Kerberos TAP tests to exercise cases where nontrivial
amounts of data need to be pushed through encryption. Before, those
tests didn't provide any useful coverage at all for the cases of
interest here. (They still might not, depending on timing, but at
least there's a chance.)
Per complaint from pmc@citylink and subsequent investigation.
Back-patch to v12 where this code was introduced.
Discussion: https://postgr.es/m/20200109181822.GA74698@gate.oper.dinoex.org
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Make the error messages around GSSAPI encryption a bit clearer. Tweak
some messages to avoid plural problems.
Also make a code change for clarity. Using "conf" for "confidential"
is quite confusing. Using "conf_state" is perhaps not much better but
that's what the GSSAPI documentation uses, so there is at least some
hope of understanding it.
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Reviewed-by: Michael Paquier
Discussion: https://postgr.es/m/CA%2BhUKGJFWXmtYo6Frd77RR8YXCHz7hJ2mRy5aHV%3D7fJOqDnBHA%40mail.gmail.com
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I noted that some buildfarm members were complaining about %ld being
used to format values that are (probably) declared size_t. Use %zu
instead, and insert a cast just in case some versions of the GSSAPI
API declare the length field differently. While at it, clean up
gratuitous differences in wording of equivalent messages, show
the complained-of length in all relevant messages not just some,
include trailing newline where needed, adjust random deviations
from project-standard code layout and message style, etc.
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There was some confusion over the format of the error message returned
from the server during GSSAPI startup; specifically, it was expected
that a length would be returned when, in reality, at this early stage in
the startup sequence, no length is returned from the server as part of
an error message.
Correct the client-side code for dealing with error messages sent by the
server during startup by simply reading what's available into our
buffer, after we've discovered it's an error message, and then reporting
back what was returned.
In passing, also add in documentation of the environment variable
PGGSSENCMODE which was missed previously, and adjust the code to look
for the PGGSSENCMODE variable (the environment variable change was
missed in the prior GSSMODE -> GSSENCMODE commit).
Error-handling issue discovered by Peter Eisentraut, the rest were items
discovered during testing of the error handling.
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On both the frontend and backend, prepare for GSSAPI encryption
support by moving common code for error handling into a separate file.
Fix a TODO for handling multiple status messages in the process.
Eliminate the OIDs, which have not been needed for some time.
Add frontend and backend encryption support functions. Keep the
context initiation for authentication-only separate on both the
frontend and backend in order to avoid concerns about changing the
requested flags to include encryption support.
In postmaster, pull GSSAPI authorization checking into a shared
function. Also share the initiator name between the encryption and
non-encryption codepaths.
For HBA, add "hostgssenc" and "hostnogssenc" entries that behave
similarly to their SSL counterparts. "hostgssenc" requires either
"gss", "trust", or "reject" for its authentication.
Similarly, add a "gssencmode" parameter to libpq. Supported values are
"disable", "require", and "prefer". Notably, negotiation will only be
attempted if credentials can be acquired. Move credential acquisition
into its own function to support this behavior.
Add a simple pg_stat_gssapi view similar to pg_stat_ssl, for monitoring
if GSSAPI authentication was used, what principal was used, and if
encryption is being used on the connection.
Finally, add documentation for everything new, and update existing
documentation on connection security.
Thanks to Michael Paquier for the Windows fixes.
Author: Robbie Harwood, with changes to the read/write functions by me.
Reviewed in various forms and at different times by: Michael Paquier,
Andres Freund, David Steele.
Discussion: https://www.postgresql.org/message-id/flat/jlg1tgq1ktm.fsf@thriss.redhat.com
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