The bignum module does not officially support "negative zero" (an
mbedtls_mpi object with s=-1 and all limbs zero). However, we have a
history of bugs where a function that should produce an official
zero (with s=1), produces a negative zero in some circumstances. So it's
good to check that the bignum functions are robust when passed a negative
zero as input. And for that, we need a way to construct a negative zero
from test case arguments.
There are checks that functions don't produce negative zeros as output in
the test suite. Skip those checks if there's a negative zero input: we
don't want functions to _create_ negative zeros, but we don't mind if
they _propagate_ negative zeros.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
In mbedtls_mpi_add_mpi() and mbedtls_mpi_sub_mpi(), and by extention
mbedtls_mpi_add_int() and mbedtls_mpi_sub_int(), when the resulting value
was zero, the sign bit of the result was incorrectly set to -1 when the
left-hand operand was negative. This is not a valid mbedtls_mpi
representation. Fix this: always set the sign to +1 when the result is 0.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This exposes a bug in mbedtls_mpi_add_mpi() and mbedtls_mpi_sub_mpi() which
will be fixed in a subsequent commit.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
mbedtls_mpi_add_mpi() and mbedtls_mpi_sub_mpi() have the same logic, just
with one bit to flip in the sign calculation. Move the shared logic to a new
auxiliary function. This slightly reduces the code size (if the compiler
doesn't inline) and reduces the maintenance burden.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
The already existing "x509_csr_check()" function is extended in order
to support/test also CSR's extensions. The test is performed by
adding an extended key usage.
Signed-off-by: Valerio Setti <vsetti@baylibre.com>
This patch updates the `mbedtls_mpi_mod_raw_conv_xx()` methods
as follows:
* Renamed for simplicity: conv_fwd -> from_mont_rep, conv_inv -> to_mont_rep.
* Uncoupled the dependency on the legaly bignum interface.
* `mbedtls_mpi` is no longer used for temporary buffer allocation.
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
This patch moves `BignumModRawOperation` and `BignumModRawOperationArchSplit`
outside of the scaffolding merge slot.
It also renames `r_sqrt` property to `r2`.
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
This patch modifies the BignumModRawOperation class to
provide special access to key members commonly used
in tests.
It binds the module's getters to conversion functions
which enable automatic conversions such as:
* hex to int.
* zero padding hex strings.
* common Montgomery constants such as R, R^2 and R^01
are now be calculated upon access.
class `BignumModRawOperationArchSplit` is also updated to
utilise the new design.
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
This patch is adding a basic instantance of `BignumModRawOperation`
and creates an `BignumModRawOperationArchSplit` class, copying
over the implementation of `BignumCoreRawOperationArchSplit`.
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
In 'dh_genprime.c', the following condition can be found inside an 'if' statement:
ret = mbedtls_mpi_write_file( "P = ", &P, 16, fout ) != 0
As the '!=' operator binds closer than the assignment operator ('='), the value assigned to 'ret' will be the boolean result of the comparison (0 or 1) instead of the status code returned by 'mbedtls_mpi_write_file'. This means that the above statement is actually equivalent to:
ret = ( mbedtls_mpi_write_file( "P = ", &P, 16, fout ) != 0 )
What we want instead is for the the status code to be assigned to 'ret'. If the value assigned is non-zero, it will be 'truthy' and the 'if' branch will be taken.
( ret = mbedtls_mpi_write_file( "P = ", &P, 16, fout ) ) != 0
This PR fixes the issue by explicitly specifying the precedence of operations with parentheses.
Signed-off-by: ihsinme <ihsinme@gmail.com>
A core MPI must have at least 1 limb. We can no longer test with 0 limbs,
and we don't need to anyway, so don't try.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This way static analyzers have a chance of knowing we don't expect the
bignum functions to support empty inputs. As things are, Coverity keeps
complaining about it.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Instead of corrupting the public key part of the message,
corrupt the proof part. A proof is conceptually similar to a signature,
and changing anything in it should make it invalid with
a high probability.
Also, instead of shifting data, perform a bitflip.
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
