The signature and naming of the Montgomrey initialisation function in
development and in the LTS was different. Align them for easier
readability and maintenance.
Signed-off-by: Janos Follath <janos.follath@arm.com>
So far we needed it only locally here, but we will need calculating RR
for safe unblinding in RSA as well.
Signed-off-by: Janos Follath <janos.follath@arm.com>
Clear some confusion between `X` as the output variable and "X" as a name
given to the accumulator. Previous iterations of the code used the variable
`X` as the accumulator, but now that the accumulator is `W[x_index]`, some
of the comments didn't make sense.
Remove the copy of the initial value of `X` into `W[x_index]`, which was
meaningless: the initial value of an output variable should not, and did
not, matter. `W[x_index]` is later overridden unconditionally to take the
value `RR`.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
IAR was warning that conditional execution could bypass initialisation of
variables, although those same variables were not used uninitialised. Fix
this along with some other IAR warnings.
Signed-off-by: Paul Elliott <paul.elliott@arm.com>
In some contexts, the output pointer may equal the first input
pointer, in which case copying is not only superfluous but results in
"Source and destination overlap in memcpy" errors from Valgrind (as I
observed in the context of ecp_double_jac) and a diagnostic message
from TrustInSoft Analyzer (as Pascal Cuoq reported in the context of
other ECP functions called by cert-app with a suitable certificate).
Signed-off-by: Aaron M. Ucko <ucko@ncbi.nlm.nih.gov>
The first half of the table is not used, let's reuse index 0 for the
result instead of appending it in the end.
Signed-off-by: Janos Follath <janos.follath@arm.com>
The table size was set before the configured window size bound was
applied which lead to out of bounds access when the configured window
size bound is less.
Signed-off-by: Janos Follath <janos.follath@arm.com>
The window size starts giving diminishing returns around 6 on most
platforms and highly unlikely to be more than 31 in practical use cases.
Still, compilers and static analysers might complain about this and
better to be pedantic.
Co-authored-by: Gilles Peskine <gilles.peskine@arm.com>
Signed-off-by: Janos Follath <janos.follath@arm.com>
With small exponents (for example, when doing RSA-1024 with CRT, each
prime is 512 bits and we'll use wsize = 5 which may be smaller that the
maximum - or even worse when doing public RSA operations which typically
have a 16-bit exponent so we'll use wsize = 1) the usage of W will have
pre-computed values, then empty space, then the accumulator at the very
end.
Move X next to the precomputed values to make accesses more efficient
and intuitive.
Signed-off-by: Janos Follath <janos.follath@arm.com>
Elements of W didn't all have the same owner: all were owned by this
function, except W[x_index]. It is more robust if we make a proper copy
of X.
Signed-off-by: Janos Follath <janos.follath@arm.com>
When x is the most negative value of a two's complement type,
`(unsigned_type)(-x)` has undefined behavior, whereas `-(unsigned_type)x`
has well-defined behavior and does what was intended.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Fix undefined behavior (typically harmless in practice) of
mbedtls_mpi_add_mpi(), mbedtls_mpi_add_abs() and mbedtls_mpi_add_int() when
both operands are 0 and the left operand is represented with 0 limbs.
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>
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>
Out of window zeroes were doing squaring on the output variable
directly. This leaks the position of windows and the out of window
zeroes.
Loading the output variable from the table in constant time removes this
leakage.
Signed-off-by: Janos Follath <janos.follath@arm.com>
We used to include platform.h only when MBEDTLS_PLATFORM_C was enabled, and
to define ad hoc replacements for mbedtls_xxx functions on a case-by-case
basis when MBEDTLS_PLATFORM_C was disabled. The only reason for this
complication was to allow building individual source modules without copying
platform.h. This is not something we support or recommend anymore, so get
rid of the complication: include platform.h unconditionally.
There should be no change in behavior since just including the header should
not change the behavior of a program.
This commit replaces most occurrences of conditional inclusion of
platform.h, using the following code:
```
perl -i -0777 -pe 's!#if.*\n#include "mbedtls/platform.h"\n(#else.*\n(#define (mbedtls|MBEDTLS)_.*\n|#include <(stdarg|stddef|stdio|stdlib|string|time)\.h>\n)*)?#endif.*!#include "mbedtls/platform.h"!mg' $(git grep -l '#include "mbedtls/platform.h"')
```
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Fix a null pointer dereference when performing some operations on zero
represented with 0 limbs: mbedtls_mpi_mod_int() dividing by 2, or
mbedtls_mpi_write_string() in base 2.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Elinimate macros defined by modules locally in the functions that are
moving to the new constant-time module.
Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
There were multiple functions called mbedtls_cf_size_bool_eq. They had exactly
the same behavior, so move the one in bignum.c and remove the other.
Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
