The previous code used comparison operators >= and == that are quite likely to
be compiled to branches by some compilers on some architectures (with some
optimisation levels).
For example, take the following function:
void old_update( size_t data_len, size_t *padlen )
{
*padlen *= ( data_len >= *padlen + 1 );
}
With Clang 3.8, let's compile it for the Arm v6-M architecture:
% clang --target=arm-none-eabi -march=armv6-m -Os foo.c -S -o - |
sed -n '/^old_update:$/,/\.size/p'
old_update:
.fnstart
@ BB#0:
.save {r4, lr}
push {r4, lr}
ldr r2, [r1]
adds r4, r2, #1
movs r3, #0
cmp r4, r0
bls .LBB0_2
@ BB#1:
mov r2, r3
.LBB0_2:
str r2, [r1]
pop {r4, pc}
.Lfunc_end0:
.size old_update, .Lfunc_end0-old_update
We can see an unbalanced secret-dependant branch, resulting in a total
execution time depends on the value of the secret (here padlen) in a
straightforward way.
The new version, based on bit operations, doesn't have this issue:
new_update:
.fnstart
@ BB#0:
ldr r2, [r1]
subs r0, r0, #1
subs r0, r0, r2
asrs r0, r0, #31
bics r2, r0
str r2, [r1]
bx lr
.Lfunc_end1:
.size new_update, .Lfunc_end1-new_update
(As a bonus, it's smaller and uses less stack.)
While there's no formal guarantee that the version based on bit operations in
C won't be translated using branches by the compiler, experiments tend to show
that's the case [1], and it is commonly accepted knowledge in the practical
crypto community that if we want to sick to C, bit operations are the safest
bet [2].
[1] https://github.com/mpg/ct/blob/master/results
[2] https://github.com/veorq/cryptocoding
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
Return a name that more clearly returns nonzero=true=good, 0=bad. We'd
normally expect check_xxx to return 0=pass, nonzero=fail so
check_parity was a bad name.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
An early draft of the PSA crypto specification required multipart
operations to keep working after destroying the key. This is no longer
the case: instead, now, operations are guaranteed to fail. Mbed TLS
does not comply yet, and still allows the operation to keep going.
Stop testing Mbed TLS's non-compliant behavior.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Rely on Asan to detect a potential buffer overflow, instead of doing a
manual check. This makes the code simpler and Asan can detect
underflows as well as overflows.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
In the cleanup code for persistent_key_load_key_from_storage(), we
only attempt to reopen the key so that it will be deleted if it exists
at that point. It's intentional that we do nothing if psa_open_key()
fails here.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
If any of the TEST_ASSERT()s that are before the call to
mbedtls_pk_warp_as_opaque() failed, when reaching the exit label
psa_destroy_key() would be called with an uninitialized argument.
Found by Clang.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
I might be wrong, but lcc's optimizer is curious about this,
and I am too: shouldn't we free allocated stuff correctly
before exiting `dh_genprime` in this certain point of code?
Signed-off-by: makise-homura <akemi_homura@kurisa.ch>
Replace server2.crt with server2-sha256.crt which, as the name implies, is
just the SHA-256 version of the same certificate.
Replace server1.crt with cert_sha256.crt which, as the name doesn't imply, is
associated with the same key and just have a slightly different Subject Name,
which doesn't matter in this instance.
The other certificates used in this script (server5.crt and server6.crt) are
already signed with SHA-256.
This change is motivated by the fact that recent versions of GnuTLS (or older
versions with the Debian patches) reject SHA-1 in certificates by default, as
they should. There are options to still accept it (%VERIFY_ALLOW_BROKEN and
%VERIFY_ALLOW_SIGN_WITH_SHA1) but:
- they're not available in all versions that reject SHA-1-signed certs;
- moving to SHA-2 just seems cleaner anyway.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
Recent GnuTLS packages on Ubuntu 16.04 have them disabled.
From /usr/share/doc/libgnutls30/changelog.Debian.gz:
gnutls28 (3.4.10-4ubuntu1.5) xenial-security; urgency=medium
* SECURITY UPDATE: Lucky-13 issues
[...]
- debian/patches/CVE-2018-1084x-4.patch: hmac-sha384 and sha256
ciphersuites were removed from defaults in lib/gnutls_priority.c,
tests/priorities.c.
Since we do want to test the ciphersuites, explicitly re-enable them in the
server's priority string. (This is a no-op with versions of GnuTLS where those
are already enabled by default.)
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
Update copyright notices to newly added files since merge of original
PR #3546 "Update copyright notices to use Linux Foundation guidance".
Generated using the same script.
Signed-off-by: Dan Handley <dan.handley@arm.com>
* development:
Update copyright notices to use Linux Foundation guidance
Undef ASSERT before defining it to ensure that no previous definition has sneaked in through included files.
Add ChangeLog entry for X.509 CN-type vulnerability
Improve documentation of cn in x509_crt_verify()
Fix comparison between different name types
Add test: DNS names should not match IP addresses
Remove obsolete buildbot reference in compat.sh
Fix misuse of printf in shell script
Fix added proxy command when IPv6 is used
Simplify test syntax
Fix logic error in setting client port
ssl-opt.sh: include test name in log files
ssl-opt.sh: remove old buildbot-specific condition
ssl-opt.sh: add proxy to all DTLS tests
Signed-off-by: Dan Handley <dan.handley@arm.com>
