Fix the subtraction in fix_negative, which was incorrectly not looking
for a carry. This caused the result to be wrong when the least
significant limb of N was 0. Fix#4296.
The bug was introduced by d10e8fae9e
"Optimize fix_negative". Thanks to Philippe Antoine (catenacyber) for
reporting the bug which was found by his EC differential fuzzer.
Credit to OSS-Fuzz.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Reduce the code size, stack consumption and heap consumption in
fix_negative by encoding the special-case subtraction manually.
* Code size: ecp_curves.o goes down from 7837B down to 7769 in a
sample Cortex-M0 build with all curves enabled. The savings come
from not having to set up C in INIT (which is used many times) and
from not having to catch errors in fix_negative.
* Stack consumption: get rid of C on the stack.
* Heap: mbedtls_mpi_sub_abs with destination == second operand would
make a heap allocation. The new code doesn't do any heap allocation.
* Performance: no measurable difference.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
fix_negative allocates memory for its result. The calling site didn't
check the return value, so an out-of-memory error could lead to an
incorrect calculation. Fix this.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
As a result, the copyright of contributors other than Arm is now
acknowledged, and the years of publishing are no longer tracked in the
source files.
Also remove the now-redundant lines declaring that the files are part of
MbedTLS.
This commit was generated using the following script:
# ========================
#!/bin/sh
# Find files
find '(' -path './.git' -o -path './3rdparty' ')' -prune -o -type f -print | xargs sed -bi '
# Replace copyright attribution line
s/Copyright.*Arm.*/Copyright The Mbed TLS Contributors/I
# Remove redundant declaration and the preceding line
$!N
/This file is part of Mbed TLS/Id
P
D
'
# ========================
Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>
For some curves (semi-coincidentally, short Weierstrass curves), the
ECP module calculates some group parameters dynamically. Build the
code to calculate the parameters only if a relevant curve is enabled.
This fixes an unused function warning when building with only
Montgomery curves.
Signed-off-by: Gilles Peskine <gilles.peskine@arm.com>
In library source files, include "common.h", which takes care of
including "mbedtls/config.h" (or the alternative MBEDTLS_CONFIG_FILE)
and other things that are used throughout the library.
FROM=$'#if !defined(MBEDTLS_CONFIG_FILE)\n#include "mbedtls/config.h"\n#else\n#include MBEDTLS_CONFIG_FILE\n#endif' perl -i -0777 -pe 's~\Q$ENV{FROM}~#include "common.h"~' library/*.c 3rdparty/*/library/*.c scripts/data_files/error.fmt scripts/data_files/version_features.fmt
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit improves hygiene and formatting of macro definitions
throughout the library. Specifically:
- It adds brackets around parameters to avoid unintended
interpretation of arguments, e.g. due to operator precedence.
- It adds uses of the `do { ... } while( 0 )` idiom for macros that
can be used as commands.
The function ecp_mod_koblitz computed the space for the result of a
multiplication optimally for that specific case, but unfortunately
the function mbedtls_mpi_mul_mpi performs a generic, suboptimal
calculation and needs one more limb for the result. Since the result's
buffer is on the stack, the best case scenario is that the program
stops.
This only happened on 64 bit platforms.
Fixes#569
