The signature of mbedtls_mpi_cmp_mpi_ct() meant to support using it in
place of mbedtls_mpi_cmp_mpi(). This meant full comparison functionality
and a signed result.
To make the function more universal and friendly to constant time
coding, we change the result type to unsigned. Theoretically, we could
encode the comparison result in an unsigned value, but it would be less
intuitive.
Therefore we won't be able to represent the result as unsigned anymore
and the functionality will be constrained to checking if the first
operand is less than the second. This is sufficient to support the
current use case and to check any relationship between MPIs.
The only drawback is that we need to call the function twice when
checking for equality, but this can be optimised later if an when it is
needed.
Make check-test-cases.py pass.
Prior to this commit, there were many repeated test descriptions, but
none with the same test data and dependencies and comments, as checked
with the following command:
for x in tests/suites/*.data; do perl -00 -ne 'warn "$ARGV: $. = $seen{$_}\n" if $seen{$_}; $seen{$_}=$.' $x; done
Wherever a test suite contains multiple test cases with the exact same
description, add " [#1]", " [#2]", etc. to make the descriptions
unique. We don't currently use this particular arrangement of
punctuation, so all occurrences of " [#" were added by this script.
I used the following ad hoc code:
import sys
def fix_test_suite(data_file_name):
in_paragraph = False
total = {}
index = {}
lines = None
with open(data_file_name) as data_file:
lines = list(data_file.readlines())
for line in lines:
if line == '\n':
in_paragraph = False
continue
if line.startswith('#'):
continue
if not in_paragraph:
# This is a test case description line.
total[line] = total.get(line, 0) + 1
index[line] = 0
in_paragraph = True
with open(data_file_name, 'w') as data_file:
for line in lines:
if line in total and total[line] > 1:
index[line] += 1
line = '%s [#%d]\n' % (line[:-1], index[line])
data_file.write(line)
for data_file_name in sys.argv[1:]:
fix_test_suite(data_file_name)
The function `mbedtls_mpi_write_binary()` writes big endian byte order,
but we need to be able to write little endian in some caseses. (For
example when handling keys corresponding to Montgomery curves.)
Used `echo xx | tac -rs ..` to transform the test data to little endian.
The function `mbedtls_mpi_read_binary()` expects big endian byte order,
but we need to be able to read from little endian in some caseses. (For
example when handling keys corresponding to Montgomery curves.)
Used `echo xx | tac -rs .. | tr [a-z] [A-Z]` to transform the test data
to little endian and `echo "ibase=16;xx" | bc` to convert to decimal.
Extend the mbedtls_mpi_is_prime_det test to check that it reports
the number as prime when testing rounds-1 rounds, then reports the
number as composite when testing the full number of rounds.
When using a primality testing function the tolerable error rate depends
on the scheme in question, the required security strength and wether it
is used for key generation or parameter validation. To support all use
cases we need more flexibility than what the old API provides.
Primality tests have to deal with different distribution when generating
primes and when validating primes.
These new tests are testing if mbedtls_mpi_is_prime() is working
properly in the latter setting.
The new tests involve pseudoprimes with maximum number of
non-witnesses. The non-witnesses were generated by printing them
from mpi_miller_rabin(). The pseudoprimes were generated by the
following function:
void gen_monier( mbedtls_mpi* res, int nbits )
{
mbedtls_mpi p_2x_plus_1, p_4x_plus_1, x, tmp;
mbedtls_mpi_init( &p_2x_plus_1 );
mbedtls_mpi_init( &p_4x_plus_1 );
mbedtls_mpi_init( &x ); mbedtls_mpi_init( &tmp );
do
{
mbedtls_mpi_gen_prime( &p_2x_plus_1, nbits >> 1, 0,
rnd_std_rand, NULL );
mbedtls_mpi_sub_int( &x, &p_2x_plus_1, 1 );
mbedtls_mpi_div_int( &x, &tmp, &x, 2 );
if( mbedtls_mpi_get_bit( &x, 0 ) == 0 )
continue;
mbedtls_mpi_mul_int( &p_4x_plus_1, &x, 4 );
mbedtls_mpi_add_int( &p_4x_plus_1, &p_4x_plus_1, 1 );
if( mbedtls_mpi_is_prime( &p_4x_plus_1, rnd_std_rand,
NULL ) == 0 )
break;
} while( 1 );
mbedtls_mpi_mul_mpi( res, &p_2x_plus_1, &p_4x_plus_1 );
}
Setting the dh_flag to 1 used to indicate that the caller requests safe
primes from mbedtls_mpi_gen_prime. We generalize the functionality to
make room for more flags in that parameter.
- Separate string and hex parameter as unhexify is moved out of the function. It's input should only be hex.
- Fix test mbedtls_ccm_encrypt_and_tag that grows input message buffer with tag
- Add missing expected length parameter in ECP TLS tests
- Add deleted TEST_ASSERT and mbedtls calls that got removed in script based code generation
The specification requires that numbers are the raw entropy (except for odd/
even) and at least 2^(nbits-0.5). If not, new random bits need to be used for
the next number. Similarly, if the number is not prime new random bits need to
be used.
The modular inversion function hangs when provided with the modulus 1. This commit refuses this modulus with a BAD_INPUT error code. It also adds a test for this case.
Fix a buffer overflow when writting a string representation of an MPI
number to a buffer in hexadecimal. The problem occurs because hex
digits are written in pairs and this is not accounted for in the
calculation of the required buffer size when the number of digits is
odd.
Changes include:
- Integers marked with '#' in the .function files.
- Strings should have "" in .data files.
- String comparison instead of preprocessor-like replace for e.g. '=='
- Params and variables cannot have the same name in .function files
