Try to avoid showing externally visible timing or memory access
differences regardless of whether the derived pwd-value is smaller than
the group prime.
This is related to CVE-2019-9494.
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
This is an initial step towards making the FFC case use strictly
constant time operations similarly to the ECC case.
sae_test_pwd_seed_ffc() does not yet have constant time behavior,
though.
This is related to CVE-2019-9494.
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
These groups have significant probability of coming up with pwd-value
that is equal or greater than the prime and as such, need for going
through the PWE derivation loop multiple times. This can result in
sufficient timing different to allow an external observer to determine
how many rounds are needed and that can leak information about the used
password.
Force at least 40 loop rounds for these MODP groups similarly to the ECC
group design to mask timing. This behavior is not described in IEEE Std
802.11-2016 for SAE, but it does not result in different values (i.e.,
only different timing), so such implementation specific countermeasures
can be done without breaking interoperability with other implementation.
Note: These MODP groups 22, 23, and 24 are not considered sufficiently
strong to be used with SAE (or more or less anything else). As such,
they should never be enabled in runtime configuration for any production
use cases. These changes to introduce additional protection to mask
timing is only for completeness of implementation and not an indication
that these groups should be used.
This is related to CVE-2019-9494.
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Make the non-failure path in the function proceed without branches based
on r_odd and in constant time to minimize risk of observable differences
in timing or cache use. (CVE-2019-9494)
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
The QR test result can provide information about the password to an
attacker, so try to minimize differences in how the
sae_test_pwd_seed_ecc() result is used. (CVE-2019-9494)
Use heap memory for the dummy password to allow the same password length
to be used even with long passwords.
Use constant time selection functions to track the real vs. dummy
variables so that the exact same operations can be performed for both QR
test results.
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
The rules defining which DH groups are suitable for SAE use were
accepted into IEEE 802.11 REVmd based on this document:
https://mentor.ieee.org/802.11/dcn/19/11-19-0387-02-000m-addressing-some-sae-comments.docx
Enforce those rules in production builds of wpa_supplicant and hostapd.
CONFIG_TESTING_OPTIONS=y builds can still be used to select any o the
implemented groups to maintain testing coverage.
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
This extends the SAE implementation in both infrastructure and mesh BSS
cases to allow an optional Password Identifier to be used. This uses the
mechanism added in P802.11REVmd/D1.0. The Password Identifier is
configured in a wpa_supplicant network profile as a new string parameter
sae_password_id. In hostapd configuration, the existing sae_password
parameter has been extended to allow the password identifier (and also a
peer MAC address) to be set. In addition, multiple sae_password entries
can now be provided to hostapd to allow multiple per-peer and
per-identifier passwords to be set.
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
This makes it easier to understand why "SAE: Failed to select group"
debug entry shows up in cases the selected crypto library does not
support a specific group.
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Set Sc to 2^16-1 when moving to Accepted state per IEEE Std 802.11-2016,
12.4.8.6.5 (Protocol instance behavior - Confirmed state). This allows
the peer in Accepted state to silently ignore unnecessary
retransmissions of the Confirm message.
Signed-off-by: Jouni Malinen <j@w1.fi>
IEEE Std 802.11-2012 11.3.5.4 specifies the PMKID for SAE-derived keys
as:
L((commit-scalar + peer-commit-scalar) mod r, 0, 128)
This is already calculated in the SAE code when the PMK is derived, but
not saved anywhere. Later, when generating the PMKID for plink action
frames, the definition for PMKID from 11.6.1.3 is incorrectly used.
Correct this by saving the PMKID when the key is generated and use it
subsequently.
Signed-off-by: Bob Copeland <me@bobcopeland.com>
Reorder terms in a way that no invalid pointers are generated with
pos+len operations. end-pos is always defined (with a valid pos pointer)
while pos+len could end up pointing beyond the end pointer which would
be undefined behavior.
Signed-off-by: Jouni Malinen <j@w1.fi>
The current P802.11 description of SAE uses "1 < element < p" as the
required range. However, this is not correct and does not match the
Dragonfly description of "1 < element < p-1". SAE definition will need
to change here. Update the implementation to reject p-1 based on the
correct rule here.
Signed-off-by: Jouni Malinen <j@w1.fi>
IEEE Std 802.11-2012 description of SAE does not require this, i.e., it
describes the requirement as 0 < scalar < r for processing the Commit
message. However, this is not correct and will be changes to 1 < scalar
< r to match the Dragonfly description so that a trivial secret case
will be avoided explicitly.
This is not much of an issue for the locally generated commit-scalar
since it would be very unlikely to get the value of 1. For Commit
message processing, a peer with knowledge of the password could
potentially force the exchange to expose key material without this
check.
Signed-off-by: Jouni Malinen <j@w1.fi>
If PWE is discovered before the minimum number of loops (k) is reached,
the extra iterations use a random "password" to further obfuscate the
cost of discovering PWE.
Signed-off-by: Jouni Malinen <j@w1.fi>
This replaces the earlier IEEE Std 802.11-2012 algorithm with the design
from P802.11-REVmc/D4.0. Things brings in a blinding technique for
determining whether the pwd-seed results in a suitable PWE value.
Signed-off-by: Jouni Malinen <j@w1.fi>
draft-irtf-cfrg-dragonfly recommends implementation to set the security
parameter, k, to a value of at least 40. This will make PWE generation
take significantly more resources, but makes it more likely to hide
timing differences due to different number of loops needed to find a
suitable PWE.
Signed-off-by: Jouni Malinen <j@w1.fi>
This check explicitly for reflection attack and stops authentication
immediately if that is detected instead of continuing to the following
4-way handshake that would fail due to the attacker not knowing the key
from the SAE exchange.
Signed-off-by: Jouni Malinen <j@w1.fi>
There is no need to keep temporary keys in memory beyond the end of the
association, so explicitly clear any SAE buffers that can contain keys
as soon as such keys are not needed.
Signed-off-by: Jouni Malinen <j@w1.fi>
This commit inserts Finite Cyclic Group to Anti-Clogging Token request
frame because IEEE Std 802.11-2012, Table 8-29 says "Finite Cyclic Group
is present if Status is zero or 76".
Signed-off-by: Masashi Honma <masashi.honma@gmail.com>
The mesh anti-clogging functionality is implemented partially. This
patch fixes to parse anti-clogging request frame and use anti-clogging
token.
Signed-off-by: Masashi Honma <masashi.honma@gmail.com>
This makes the implementation less likely to provide useful timing
information to potential attackers from comparisons of information
received from a remote device and private material known only by the
authorized devices.
Signed-off-by: Jouni Malinen <j@w1.fi>
If the randomly generated bignum does not meet the validation steps, the
iteration loop in sae_get_rand() did not free the data properly. Fix the
memory leak by freeing the temporary bignum before starting the next
attempt at generating the value.
Signed-off-by: Jouni Malinen <j@w1.fi>
Confirm-before-commit validation step allowed execution to continue on
error case. This could result in segfault in sae_check_confirm() if the
temporary SAE data was not available (as it would not be, e.g., in case
of an extra SAE confirm message being received after successful
exchange). Fix this by stopping SAE processing immediately after
detecting unexpected state for confirm message. In addition, make the
public sae.c functions verify sae->tmp before dereferencing it to make
this type of bugs less likely to result in critical issues.
Signed-hostap: Jouni Malinen <jouni@qca.qualcomm.com>
prime_len was added to the start pointer twice and because of this, the
actual y coordinate was not verified to be valid. This could also result
in reading beyond the buffer in some cases.
Signed-hostap: Jouni Malinen <j@w1.fi>
It was already possible to configure hostapd and wpa_supplicant to use
FT-SAE for the key management, but number of places were missing proper
AKM checks to allow FT to be used with the new AKM.
Signed-hostap: Jouni Malinen <j@w1.fi>
Number of regressions had shown up in wpa_supplicant implementation of
SAE group selection due to different integer array termination (-1 in
hostapd, 0 in wpa_supplicant) being used for SAE groups. The
default_groups list did not seem to use any explicit termination value.
In addition, the sae_group_index was not cleared back to 0 properly
whenever a new SAE session was started.
Signed-hostap: Jouni Malinen <j@w1.fi>
The peer commit element needs to be validated to pass one of the steps
listed in IEEE 802.11, 11.3.5.4:
scalar-op(r, ELEMENT) = 1 modulo p
Similar step was present for ECC groups, but was missing for FFC groups.
This is needed to avoid dictionary attacks.
Thanks to Michael Roßberg and Sascha Grau for reporting this.
Signed-hostap: Jouni Malinen <j@w1.fi>
It is clearer to keep all the validation steps described in IEEE 802.11
11.3.5.4 in a single location instead of splitting this between the
parsing and processing functions.
Signed-hostap: Jouni Malinen <j@w1.fi>
This allows even more memory to be freed when the SAE instance enters
Accepted state. This leaves only the minimal needed memory allocated
during the association which is especially helpful for the AP
implementation where multiple stations may be associated concurrently.
Signed-hostap: Jouni Malinen <j@w1.fi>
Most of the variables are not needed anymore once the SAE instance
has entered Accepted state. Free these to save memory.
Signed-hostap: Jouni Malinen <j@w1.fi>
The rand/mask values and commit scalar are derived using the exact same
operations, so only use a separate function for deriving the commit
element.
Signed-hostap: Jouni Malinen <j@w1.fi>
There is no need to postpone this validation step to a separate
processing operation for the commit message, so move the minimal
validation tasks into the parsing functions.
Signed-hostap: Jouni Malinen <j@w1.fi>
Move the bignum comparison part into the bignum library to allow a
single implementation of rand generation for both ECC and FCC based
groups.
Signed-hostap: Jouni Malinen <j@w1.fi>
