SCRAM_KEY_LEN was a variable used in the internal routines of SCRAM to
size a set of fixed-sized arrays used in the SHA and HMAC computations
during the SASL exchange or when building a SCRAM password. This had a
hard dependency on SHA-256, reducing the flexibility of SCRAM when it
comes to the addition of more hash methods. A second issue was that
SHA-256 is assumed as the cryptohash method to use all the time.
This commit renames SCRAM_KEY_LEN to a more generic SCRAM_KEY_MAX_LEN,
which is used as the size of the buffers used by the internal routines
of SCRAM. This is aimed at tracking centrally the maximum size
necessary for all the hash methods supported by SCRAM. A global
variable has the advantage of keeping the code in its simplest form,
reducing the need of more alloc/free logic for all the buffers used in
the hash calculations.
A second change is that the key length (SHA digest length) and hash
types are now tracked by the state data in the backend and the frontend,
the common portions being extended to handle these as arguments by the
internal routines of SCRAM. There are a few RFC proposals floating
around to extend the SCRAM protocol, including some to use stronger
cryptohash algorithms, so this lifts some of the existing restrictions
in the code.
The code in charge of parsing and building SCRAM secrets is extended to
rely on the key length and on the cryptohash type used for the exchange,
assuming currently that only SHA-256 is supported for the moment. Note
that the mock authentication simply enforces SHA-256.
Author: Michael Paquier
Reviewed-by: Peter Eisentraut, Jonathan Katz
Discussion: https://postgr.es/m/Y5k3Qiweo/1g9CG6@paquier.xyz
The frontend-side routine in charge of building a SCRAM verifier
mentioned that the restrictions applying to SASLprep on the password
with the encoding are described at the top of fe-auth-scram.c, but this
information is in auth-scram.c.
This is wrong since 8f8b9be, so backpatch all the way down as this is an
important documentation bit.
Spotted while reviewing a different patch.
Backpatch-through: 11
This is similar to b69aba7, except that this completes the work for
HMAC with a new routine called pg_hmac_error() that would provide more
context about the type of error that happened during a HMAC computation:
- The fallback HMAC implementation in hmac.c relies on cryptohashes, so
in some code paths it is necessary to return back the error generated by
cryptohashes.
- For the OpenSSL implementation (hmac_openssl.c), the logic is very
similar to cryptohash_openssl.c, where the error context comes from
OpenSSL if one of its internal routines failed, with different error
codes if something internal to hmac_openssl.c failed or was incorrect.
Any in-core code paths that use the centralized HMAC interface are
related to SCRAM, for errors that are unlikely going to happen, with
only SHA-256. It would be possible to see errors when computing some
HMACs with MD5 for example and OpenSSL FIPS enabled, and this commit
would help in reporting the correct errors but nothing in core uses
that. So, at the end, no backpatch to v14 is done, at least for now.
Errors in SCRAM related to the computation of the server key, stored
key, etc. need to pass down the potential error context string across
more layers of their respective call stacks for the frontend and the
backend, so each surrounding routine is adapted for this purpose.
Reviewed-by: Sergey Shinderuk
Discussion: https://postgr.es/m/Yd0N9tSAIIkFd+qi@paquier.xyz
The code of SCRAM and SASL have been tightly linked together since SCRAM
exists in the core code, making hard to apprehend the addition of new
SASL mechanisms, but these are by design different facilities, with
SCRAM being an option for SASL. This refactors the code related to both
so as the backend and the frontend use a set of callbacks for SASL
mechanisms, documenting while on it what is expected by anybody adding a
new SASL mechanism.
The separation between both layers is neat, using two sets of callbacks
for the frontend and the backend to mark the frontier between both
facilities. The shape of the callbacks is now directly inspired from
the routines used by SCRAM, so the code change is straight-forward, and
the SASL code is moved into its own set of files. These will likely
change depending on how and if new SASL mechanisms get added in the
future.
Author: Jacob Champion
Reviewed-by: Michael Paquier
Discussion: https://postgr.es/m/3d2a6f5d50e741117d6baf83eb67ebf1a8a35a11.camel@vmware.com
Similarly to the cryptohash implementations, this refactors the existing
HMAC code into a single set of APIs that can be plugged with any crypto
libraries PostgreSQL is built with (only OpenSSL currently). If there
is no such libraries, a fallback implementation is available. Those new
APIs are designed similarly to the existing cryptohash layer, so there
is no real new design here, with the same logic around buffer bound
checks and memory handling.
HMAC has a dependency on cryptohashes, so all the cryptohash types
supported by cryptohash{_openssl}.c can be used with HMAC. This
refactoring is an advantage mainly for SCRAM, that included its own
implementation of HMAC with SHA256 without relying on the existing
crypto libraries even if PostgreSQL was built with their support.
This code has been tested on Windows and Linux, with and without
OpenSSL, across all the versions supported on HEAD from 1.1.1 down to
1.0.1. I have also checked that the implementations are working fine
using some sample results, a custom extension of my own, and doing
cross-checks across different major versions with SCRAM with the client
and the backend.
Author: Michael Paquier
Reviewed-by: Bruce Momjian
Discussion: https://postgr.es/m/X9m0nkEJEzIPXjeZ@paquier.xyz
Previously, we had an undisciplined mish-mash of printfPQExpBuffer and
appendPQExpBuffer calls to report errors within libpq. This commit
establishes a uniform rule that appendPQExpBuffer[Str] should be used.
conn->errorMessage is reset only at the start of an application request,
and then accumulates messages till we're done. We can remove no less
than three different ad-hoc mechanisms that were used to get the effect
of concatenation of error messages within a sequence of operations.
Although this makes things quite a bit cleaner conceptually, the main
reason to do it is to make the world safer for the multiple-target-host
feature that was added awhile back. Previously, there were many cases
in which an error occurring during an individual host connection attempt
would wipe out the record of what had happened during previous attempts.
(The reporting is still inadequate, in that it can be hard to tell which
host got the failure, but that seems like a matter for a separate commit.)
Currently, lo_import and lo_export contain exceptions to the "never
use printfPQExpBuffer" rule. If we changed them, we'd risk reporting
an incidental lo_close failure before the actual read or write
failure, which would be confusing, not least because lo_close happened
after the main failure. We could improve this by inventing an
internal version of lo_close that doesn't reset the errorMessage; but
we'd also need a version of PQfn() that does that, and it didn't quite
seem worth the trouble for now.
Discussion: https://postgr.es/m/BN6PR05MB3492948E4FD76C156E747E8BC9160@BN6PR05MB3492.namprd05.prod.outlook.com
Two new routines to allocate a hash context and to free it are created,
as these become necessary for the goal behind this refactoring: switch
the all cryptohash implementations for OpenSSL to use EVP (for FIPS and
also because upstream does not recommend the use of low-level cryptohash
functions for 20 years). Note that OpenSSL hides the internals of
cryptohash contexts since 1.1.0, so it is necessary to leave the
allocation to OpenSSL itself, explaining the need for those two new
routines. This part is going to require more work to properly track
hash contexts with resource owners, but this not introduced here.
Still, this refactoring makes the move possible.
This reduces the number of routines for all SHA2 implementations from
twelve (SHA{224,256,386,512} with init, update and final calls) to five
(create, free, init, update and final calls) by incorporating the hash
type directly into the hash context data.
The new cryptohash routines are moved to a new file, called cryptohash.c
for the fallback implementations, with SHA2 specifics becoming a part
internal to src/common/. OpenSSL specifics are part of
cryptohash_openssl.c. This infrastructure is usable for more hash
types, like MD5 or HMAC.
Any code paths using the internal SHA2 routines are adapted to report
correctly errors, which are most of the changes of this commit. The
zones mostly impacted are checksum manifests, libpq and SCRAM.
Note that e21cbb4 was a first attempt to switch SHA2 to EVP, but it
lacked the refactoring needed for libpq, as done here.
This patch has been tested on Linux and Windows, with and without
OpenSSL, and down to 1.0.1, the oldest version supported on HEAD.
Author: Michael Paquier
Reviewed-by: Daniel Gustafsson
Discussion: https://postgr.es/m/20200924025314.GE7405@paquier.xyz
Includes some manual cleanup of places that pgindent messed up,
most of which weren't per project style anyway.
Notably, it seems some people didn't absorb the style rules of
commit c9d297751, because there were a bunch of new occurrences
of function calls with a newline just after the left paren, all
with faulty expectations about how the rest of the call would get
indented.
Within the context of SCRAM, "verifier" has a specific meaning in the
protocol, per RFCs. The existing code used "verifier" differently, to
mean whatever is or would be stored in pg_auth.rolpassword.
Fix this by using the term "secret" for this, following RFC 5803.
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://www.postgresql.org/message-id/flat/be397b06-6e4b-ba71-c7fb-54cae84a7e18%402ndquadrant.com
This is a follow-up refactoring after 09ec55b and b674211, which has
proved that the encoding and decoding routines used by SCRAM have a
poor interface when it comes to check after buffer overflows. This adds
an extra argument in the shape of the length of the result buffer for
each routine, which is used for overflow checks when encoding or
decoding an input string. The original idea comes from Tom Lane.
As a result of that, the encoding routine can now fail, so all its
callers are adjusted to generate proper error messages in case of
problems.
On failure, the result buffer gets zeroed.
Author: Michael Paquier
Reviewed-by: Daniel Gustafsson
Discussion: https://postgr.es/m/20190623132535.GB1628@paquier.xyz
This changes various places where appendPQExpBuffer was used in places
where it was possible to use appendPQExpBufferStr, and likewise for
appendStringInfo and appendStringInfoString. This is really just a
stylistic improvement, but there are also small performance gains to be
had from doing this.
Discussion: http://postgr.es/m/CAKJS1f9P=M-3ULmPvr8iCno8yvfDViHibJjpriHU8+SXUgeZ=w@mail.gmail.com
When a client connects to a rogue server sending specifically-crafted
messages, this can suffice to execute arbitrary code as the operating
system account used by the client.
While on it, fix one error handling when decoding an incorrect salt
included in the first message received from server.
Author: Michael Paquier
Reviewed-by: Jonathan Katz, Heikki Linnakangas
Security: CVE-2019-10164
Backpatch-through: 10
This removes a portion of infrastructure introduced by fe0a0b5 to allow
compilation of Postgres in environments where no strong random source is
available, meaning that there is no linking to OpenSSL and no
/dev/urandom (Windows having its own CryptoAPI). No systems shipped
this century lack /dev/urandom, and the buildfarm is actually not
testing this switch at all, so just remove it. This simplifies
particularly some backend code which included a fallback implementation
using shared memory, and removes a set of alternate regression output
files from pgcrypto.
Author: Michael Paquier
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/20181230063219.GG608@paquier.xyz
Ensure that pg_saslprep() initializes its output argument to NULL in
all failure paths, and then remove the redundant initialization that
some (not all) of its callers did. This does not fix any live bug,
but it reduces the odds of future bugs of omission.
Also add a comment about why the existing failure-path coding is
adequate.
Back-patch so as to keep the function's API consistent across branches,
again to forestall future bug introduction.
Patch by me, reviewed by Michael Paquier
Discussion: https://postgr.es/m/16558.1536407783@sss.pgh.pa.us
There are some problems with the tls-unique channel binding type. It's not
supported by all SSL libraries, and strictly speaking it's not defined for
TLS 1.3 at all, even though at least in OpenSSL, the functions used for it
still seem to work with TLS 1.3 connections. And since we had no
mechanism to negotiate what channel binding type to use, there would be
awkward interoperability issues if a server only supported some channel
binding types. tls-server-end-point seems feasible to support with any SSL
library, so let's just stick to that.
This removes the scram_channel_binding libpq option altogether, since there
is now only one supported channel binding type.
This also removes all the channel binding tests from the SSL test suite.
They were really just testing the scram_channel_binding option, which
is now gone. Channel binding is used if both client and server support it,
so it is used in the existing tests. It would be good to have some tests
specifically for channel binding, to make sure it really is used, and the
different combinations of a client and a server that support or doesn't
support it. The current set of settings we have make it hard to write such
tests, but I did test those things manually, by disabling
HAVE_BE_TLS_GET_CERTIFICATE_HASH and/or
HAVE_PGTLS_GET_PEER_CERTIFICATE_HASH.
I also removed the SCRAM_CHANNEL_BINDING_TLS_END_POINT constant. This is a
matter of taste, but IMO it's more readable to just use the
"tls-server-end-point" string.
Refactor the checks on whether the SSL library supports the functions
needed for tls-server-end-point channel binding. Now the server won't
advertise, and the client won't choose, the SCRAM-SHA-256-PLUS variant, if
compiled with an OpenSSL version too old to support it.
In the passing, add some sanity checks to check that the chosen SASL
mechanism, SCRAM-SHA-256 or SCRAM-SHA-256-PLUS, matches whether the SCRAM
exchange used channel binding or not. For example, if the client selects
the non-channel-binding variant SCRAM-SHA-256, but in the SCRAM message
uses channel binding anyway. It's harmless from a security point of view,
I believe, and I'm not sure if there are some other conditions that would
cause the connection to fail, but it seems better to be strict about these
things and check explicitly.
Discussion: https://www.postgresql.org/message-id/ec787074-2305-c6f4-86aa-6902f98485a4%40iki.fi
pg_hba_file_rules erroneously reported this as scram-sha256. Fix that.
To avoid future errors and confusion, also adjust documentation links
and internal symbols to have a separator between "sha" and "256".
Reported-by: Christophe Courtois <christophe.courtois@dalibo.com>
Author: Michael Paquier <michael.paquier@gmail.com>
This adds a second standard channel binding type for SCRAM. It is
mainly intended for third-party clients that cannot implement
tls-unique, for example JDBC.
Author: Michael Paquier <michael.paquier@gmail.com>
As things stand now, channel binding data is fetched from OpenSSL and
saved into the SCRAM exchange context for any SSL connection attempted
for a SCRAM authentication, resulting in data fetched but not used if no
channel binding is used or if a different channel binding type is used
than what the data is here for.
Refactor the code in such a way that binding data is fetched from the
SSL stack only when a specific channel binding is used for both the
frontend and the backend. In order to achieve that, save the libpq
connection context directly in the SCRAM exchange state, and add a
dependency to SSL in the low-level SCRAM routines.
This makes the interface in charge of initializing the SCRAM context
cleaner as all its data comes from either PGconn* (for frontend) or
Port* (for the backend).
Author: Michael Paquier <michael.paquier@gmail.com>
This parameter can be used to enforce the channel binding type used
during a SCRAM authentication. This can be useful to check code paths
where an invalid channel binding type is used by a client and will be
even more useful to allow testing other channel binding types when they
are added.
The default value is tls-unique, which is what RFC 5802 specifies.
Clients can optionally specify an empty value, which has as effect to
not use channel binding and use SCRAM-SHA-256 as chosen SASL mechanism.
More tests for SCRAM and channel binding are added to the SSL test
suite.
Author: Author: Michael Paquier <michael.paquier@gmail.com>
Mechanism names for SCRAM and channel binding names have been included
in scram.h by the libpq frontend code, and this header references a set
of routines which are only used by the backend. scram-common.h is on
the contrary usable by both the backend and libpq, so getting those
names from there seems more reasonable.
Author: Michael Paquier <michael.paquier@gmail.com>
We need to check whether the channel-binding flag encoded in the
client-final-message is the same one sent in the client-first-message.
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
This is the basic feature set using OpenSSL to support the feature. In
order to allow the frontend and the backend to fetch the sent and
expected TLS Finished messages, a PG-like API is added to be able to
make the interface pluggable for other SSL implementations.
This commit also adds a infrastructure to facilitate the addition of
future channel binding types as well as libpq parameters to control the
SASL mechanism names and channel binding names. Those will be added by
upcoming commits.
Some tests are added to the SSL test suite to test SCRAM authentication
with channel binding.
Author: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Don't move parenthesized lines to the left, even if that means they
flow past the right margin.
By default, BSD indent lines up statement continuation lines that are
within parentheses so that they start just to the right of the preceding
left parenthesis. However, traditionally, if that resulted in the
continuation line extending to the right of the desired right margin,
then indent would push it left just far enough to not overrun the margin,
if it could do so without making the continuation line start to the left of
the current statement indent. That makes for a weird mix of indentations
unless one has been completely rigid about never violating the 80-column
limit.
This behavior has been pretty universally panned by Postgres developers.
Hence, disable it with indent's new -lpl switch, so that parenthesized
lines are always lined up with the preceding left paren.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
The nonce consists of client and server nonces concatenated together. The
client checks the nonce contained the client nonce, but it would get fooled
if the server sent a truncated or even empty nonce.
Reported by Steven Fackler to security@postgresql.org. Neither me or Steven
are sure what harm a malicious server could do with this, but let's fix it.
In the backend, this is just to silence coverity warnings, but in the
frontend, it's a genuine leak, even if extremely rare.
Spotted by Coverity, patch by Michael Paquier.
* Remove is_scram_verifier() function. It was unused.
* Fix sanitize_char() function, used in error messages on protocol
violations, to print bytes >= 0x7F correctly.
* Change spelling of scram_MockSalt() function to be more consistent with
the surroundings.
* Change a few more references to "server proof" to "server signature" that
I missed in commit d981074c24.
* Move computation of SaltedPassword to a separate function from
scram_ClientOrServerKey(). This saves a lot of cycles in libpq, by
computing SaltedPassword only once per authentication. (Computing
SaltedPassword is expensive by design.)
* Split scram_ClientOrServerKey() into two functions. Improves
readability, by making the calling code less verbose.
* Rename "server proof" to "server signature", to better match the
nomenclature used in RFC 5802.
* Rename SCRAM_SALT_LEN to SCRAM_DEFAULT_SALT_LEN, to make it more clear
that the salt can be of any length, and the constant only specifies how
long a salt we use when we generate a new verifier. Also rename
SCRAM_ITERATIONS_DEFAULT to SCRAM_DEFAULT_ITERATIONS, for consistency.
These things caught my eye while working on other upcoming changes.
An important step of SASLprep normalization, is to convert the string to
Unicode normalization form NFKC. Unicode normalization requires a fairly
large table of character decompositions, which is generated from data
published by the Unicode consortium. The script to generate the table is
put in src/common/unicode, as well test code for the normalization.
A pre-generated version of the tables is included in src/include/common,
so you don't need the code in src/common/unicode to build PostgreSQL, only
if you wish to modify the normalization tables.
The SASLprep implementation depends on the UTF-8 functions from
src/backend/utils/mb/wchar.c. So to use it, you must also compile and link
that. That doesn't change anything for the current users of these
functions, the backend and libpq, as they both already link with wchar.o.
It would be good to move those functions into a separate file in
src/commmon, but I'll leave that for another day.
No documentation changes included, because there is no details on the
SCRAM mechanism in the docs anyway. An overview on that in the protocol
specification would probably be good, even though SCRAM is documented in
detail in RFC5802. I'll write that as a separate patch. An important thing
to mention there is that we apply SASLprep even on invalid UTF-8 strings,
to support other encodings.
Patch by Michael Paquier and me.
Discussion: https://www.postgresql.org/message-id/CAB7nPqSByyEmAVLtEf1KxTRh=PWNKiWKEKQR=e1yGehz=wbymQ@mail.gmail.com
It was not used for what the comment claimed, at all. It was actually used
as the 'base' argument to strtol(), when reading the iteration count. We
don't need a constant for base-10, so remove it.
This introduces a new generic SASL authentication method, similar to the
GSS and SSPI methods. The server first tells the client which SASL
authentication mechanism to use, and then the mechanism-specific SASL
messages are exchanged in AuthenticationSASLcontinue and PasswordMessage
messages. Only SCRAM-SHA-256 is supported at the moment, but this allows
adding more SASL mechanisms in the future, without changing the overall
protocol.
Support for channel binding, aka SCRAM-SHA-256-PLUS is left for later.
The SASLPrep algorithm, for pre-processing the password, is not yet
implemented. That could cause trouble, if you use a password with
non-ASCII characters, and a client library that does implement SASLprep.
That will hopefully be added later.
Authorization identities, as specified in the SCRAM-SHA-256 specification,
are ignored. SET SESSION AUTHORIZATION provides more or less the same
functionality, anyway.
If a user doesn't exist, perform a "mock" authentication, by constructing
an authentic-looking challenge on the fly. The challenge is derived from
a new system-wide random value, "mock authentication nonce", which is
created at initdb, and stored in the control file. We go through these
motions, in order to not give away the information on whether the user
exists, to unauthenticated users.
Bumps PG_CONTROL_VERSION, because of the new field in control file.
Patch by Michael Paquier and Heikki Linnakangas, reviewed at different
stages by Robert Haas, Stephen Frost, David Steele, Aleksander Alekseev,
and many others.
Discussion: https://www.postgresql.org/message-id/CAB7nPqRbR3GmFYdedCAhzukfKrgBLTLtMvENOmPrVWREsZkF8g%40mail.gmail.com
Discussion: https://www.postgresql.org/message-id/CAB7nPqSMXU35g%3DW9X74HVeQp0uvgJxvYOuA4A-A3M%2B0wfEBv-w%40mail.gmail.com
Discussion: https://www.postgresql.org/message-id/55192AFE.6080106@iki.fi