diff --git a/library/bignum_core.h b/library/bignum_core.h index add7fee32..b7af4d0aa 100644 --- a/library/bignum_core.h +++ b/library/bignum_core.h @@ -517,6 +517,9 @@ size_t mbedtls_mpi_core_exp_mod_working_limbs( size_t AN_limbs, size_t E_limbs ) * \brief Perform a modular exponentiation with secret exponent: * X = A^E mod N, where \p A is already in Montgomery form. * + * \p X may be aliased to \p A, but not to \p RR or \p E, even if \p E_limbs == + * \p AN_limbs. + * * \param[out] X The destination MPI, as a little endian array of length * \p AN_limbs. * \param[in] A The base MPI, as a little endian array of length \p AN_limbs. diff --git a/library/bignum_mod_raw.c b/library/bignum_mod_raw.c index 22e56b7e6..266d915f2 100644 --- a/library/bignum_mod_raw.c +++ b/library/bignum_mod_raw.c @@ -124,6 +124,37 @@ void mbedtls_mpi_mod_raw_sub( mbedtls_mpi_uint *X, /* BEGIN MERGE SLOT 3 */ +size_t mbedtls_mpi_mod_raw_inv_prime_working_limbs( size_t AN_limbs ) +{ + /* mbedtls_mpi_mod_raw_inv_prime() needs a temporary for the exponent, + * which will be the same size as the modulus and input (AN_limbs), + * and additional space to pass to mbedtls_mpi_core_exp_mod(). */ + return( AN_limbs + + mbedtls_mpi_core_exp_mod_working_limbs( AN_limbs, AN_limbs ) ); +} + +void mbedtls_mpi_mod_raw_inv_prime( mbedtls_mpi_uint *X, + const mbedtls_mpi_uint *A, + const mbedtls_mpi_uint *N, + size_t AN_limbs, + const mbedtls_mpi_uint *RR, + mbedtls_mpi_uint *T ) +{ + /* Inversion by power: g^|G| = 1 => g^(-1) = g^(|G|-1), and + * |G| = N - 1, so we want + * g^(|G|-1) = g^(N - 2) + */ + + /* Use the first AN_limbs of T to hold N - 2 */ + mbedtls_mpi_uint *Nminus2 = T; + (void) mbedtls_mpi_core_sub_int( Nminus2, N, 2, AN_limbs ); + + /* Rest of T is given to exp_mod for its working space */ + mbedtls_mpi_core_exp_mod( X, + A, N, AN_limbs, Nminus2, AN_limbs, + RR, T + AN_limbs ); +} + /* END MERGE SLOT 3 */ /* BEGIN MERGE SLOT 4 */ diff --git a/library/bignum_mod_raw.h b/library/bignum_mod_raw.h index d7b6dd115..698119e19 100644 --- a/library/bignum_mod_raw.h +++ b/library/bignum_mod_raw.h @@ -174,6 +174,51 @@ void mbedtls_mpi_mod_raw_sub( mbedtls_mpi_uint *X, /* BEGIN MERGE SLOT 3 */ +/** + * \brief Returns the number of limbs of working memory required for + * a call to `mbedtls_mpi_mod_raw_inv_prime()`. + * + * \param AN_limbs The number of limbs in the input `A` and the modulus `N` + * (they must be the same size) that will be given to + * `mbedtls_mpi_mod_raw_inv_prime()`. + * + * \return The number of limbs of working memory required by + * `mbedtls_mpi_mod_raw_inv_prime()`. + */ +size_t mbedtls_mpi_mod_raw_inv_prime_working_limbs( size_t AN_limbs ); + +/** + * \brief Perform fixed-width modular inversion of a Montgomery-form MPI with + * respect to a modulus \p N that must be prime. + * + * \p X may be aliased to \p A, but not to \p N or \p RR. + * + * \param[out] X The modular inverse of \p A with respect to \p N. + * Will be in Montgomery form. + * \param[in] A The number to calculate the modular inverse of. + * Must be in Montgomery form. Must not be 0. + * \param[in] N The modulus, as a little-endian array of length \p AN_limbs. + * Must be prime. + * \param AN_limbs The number of limbs in \p A, \p N and \p RR. + * \param[in] RR The precomputed residue of 2^{2*biL} modulo N, as a little- + * endian array of length \p AN_limbs. + * \param[in,out] T Temporary storage of at least the number of limbs returned + * by `mbedtls_mpi_mod_raw_inv_prime_working_limbs()`. + * Its initial content is unused and its final content is + * indeterminate. + * It must not alias or otherwise overlap any of the other + * parameters. + * It is up to the caller to zeroize \p T when it is no + * longer needed, and before freeing it if it was dynamically + * allocated. + */ +void mbedtls_mpi_mod_raw_inv_prime( mbedtls_mpi_uint *X, + const mbedtls_mpi_uint *A, + const mbedtls_mpi_uint *N, + size_t AN_limbs, + const mbedtls_mpi_uint *RR, + mbedtls_mpi_uint *T ); + /* END MERGE SLOT 3 */ /* BEGIN MERGE SLOT 4 */ diff --git a/scripts/mbedtls_dev/bignum_common.py b/scripts/mbedtls_dev/bignum_common.py index 3ff8b2f35..0339b1ad1 100644 --- a/scripts/mbedtls_dev/bignum_common.py +++ b/scripts/mbedtls_dev/bignum_common.py @@ -99,6 +99,7 @@ class OperationCommon(test_data_generation.BaseTest): limb_sizes = [32, 64] # type: List[int] arities = [1, 2] arity = 2 + suffix = False # for arity = 1, symbol can be prefix (default) or suffix def __init__(self, val_a: str, val_b: str = "0", bits_in_limb: int = 32) -> None: self.val_a = val_a @@ -170,7 +171,8 @@ class OperationCommon(test_data_generation.BaseTest): """ if not self.case_description: if self.arity == 1: - self.case_description = "{} {:x}".format( + format_string = "{1:x} {0}" if self.suffix else "{0} {1:x}" + self.case_description = format_string.format( self.symbol, self.int_a ) elif self.arity == 2: diff --git a/scripts/mbedtls_dev/bignum_data.py b/scripts/mbedtls_dev/bignum_data.py index e6ed30005..965893320 100644 --- a/scripts/mbedtls_dev/bignum_data.py +++ b/scripts/mbedtls_dev/bignum_data.py @@ -90,8 +90,8 @@ RANDOM_1024_BIT_SEED_4_NO5 = ("53be4721f5b9e1f5acdac615bc20f6264922b9ccf469aef8" "4708d9893a973000b54a23020fc5b043d6e4a51519d9c9cc" "52d32377e78131c1") -# Adding 192 bit and 1024 bit numbers because these are the shortest required -# for ECC and RSA respectively. +# Adding 192 bit and 1024 bit numbers because these are the shortest required +# for ECC and RSA respectively. INPUTS_DEFAULT = [ "0", "1", # corner cases "2", "3", # small primes @@ -110,13 +110,21 @@ INPUTS_DEFAULT = [ # supported for now. MODULI_DEFAULT = [ "53", # safe prime - "45", # non-prime + "45", # non-prime SAFE_PRIME_192_BIT_SEED_1, # safe prime RANDOM_192_BIT_SEED_2_NO4, # not a prime SAFE_PRIME_1024_BIT_SEED_3, # safe prime RANDOM_1024_BIT_SEED_4_NO5, # not a prime ] +# Some functions, e.g. mbedtls_mpi_mod_raw_inv_prime(), only support prime moduli. +ONLY_PRIME_MODULI = [ + "53", # safe prime + "8ac72304057392b5", # 9999999997777777333 (longer, not safe, prime) + SAFE_PRIME_192_BIT_SEED_1, # safe prime + SAFE_PRIME_1024_BIT_SEED_3, # safe prime + ] + def __gen_safe_prime(bits, seed): ''' Generate a safe prime. diff --git a/scripts/mbedtls_dev/bignum_mod_raw.py b/scripts/mbedtls_dev/bignum_mod_raw.py index d05479a00..048642667 100644 --- a/scripts/mbedtls_dev/bignum_mod_raw.py +++ b/scripts/mbedtls_dev/bignum_mod_raw.py @@ -18,6 +18,7 @@ from typing import Dict, List from . import test_data_generation from . import bignum_common +from .bignum_data import ONLY_PRIME_MODULI class BignumModRawTarget(test_data_generation.BaseTarget): #pylint: disable=abstract-method, too-few-public-methods @@ -53,6 +54,34 @@ class BignumModRawSub(bignum_common.ModOperationCommon, # BEGIN MERGE SLOT 3 +class BignumModRawInvPrime(bignum_common.ModOperationCommon, + BignumModRawTarget): + """Test cases for bignum mpi_mod_raw_inv_prime().""" + moduli = ONLY_PRIME_MODULI + symbol = "^ -1" + test_function = "mpi_mod_raw_inv_prime" + test_name = "mbedtls_mpi_mod_raw_inv_prime (Montgomery form only)" + input_style = "fixed" + arity = 1 + suffix = True + + @property + def is_valid(self) -> bool: + return self.int_a > 0 and self.int_a < self.int_n + + @property + def arg_a(self) -> str: + # Input has to be given in Montgomery form + mont_a = self.to_montgomery(self.int_a) + return self.format_arg('{:x}'.format(mont_a)) + + def result(self) -> List[str]: + result = bignum_common.invmod(self.int_a, self.int_n) + if result < 0: + result += self.int_n + mont_result = self.to_montgomery(result) + return [self.format_result(mont_result)] + # END MERGE SLOT 3 # BEGIN MERGE SLOT 4 diff --git a/tests/suites/test_suite_bignum_core.function b/tests/suites/test_suite_bignum_core.function index b64127afc..7bf03fb49 100644 --- a/tests/suites/test_suite_bignum_core.function +++ b/tests/suites/test_suite_bignum_core.function @@ -1097,6 +1097,12 @@ void mpi_core_exp_mod( char * input_N, char * input_A, TEST_EQUAL( 0, memcmp( X, Y, N_limbs * sizeof( mbedtls_mpi_uint ) ) ); + /* Check when output aliased to input */ + + mbedtls_mpi_core_exp_mod( A, A, N, N_limbs, E, E_limbs, R2, T ); + + TEST_EQUAL( 0, memcmp( X, A, N_limbs * sizeof( mbedtls_mpi_uint ) ) ); + exit: mbedtls_free( T ); mbedtls_free( A ); diff --git a/tests/suites/test_suite_bignum_mod_raw.function b/tests/suites/test_suite_bignum_mod_raw.function index c7decf007..5d23707e4 100644 --- a/tests/suites/test_suite_bignum_mod_raw.function +++ b/tests/suites/test_suite_bignum_mod_raw.function @@ -349,6 +349,75 @@ exit: /* BEGIN MERGE SLOT 3 */ +/* BEGIN_CASE */ +void mpi_mod_raw_inv_prime( char * input_N, char * input_A, char * input_X ) +{ + mbedtls_mpi_uint *A = NULL; + mbedtls_mpi_uint *N = NULL; + mbedtls_mpi_uint *X = NULL; + size_t A_limbs, N_limbs, X_limbs; + mbedtls_mpi_uint *Y = NULL; + mbedtls_mpi_uint *T = NULL; + const mbedtls_mpi_uint *R2 = NULL; + + /* Legacy MPIs for computing R2 */ + mbedtls_mpi N_mpi; /* gets set up manually, aliasing N, so no need to free */ + mbedtls_mpi R2_mpi; + mbedtls_mpi_init( &R2_mpi ); + + TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &A, &A_limbs, input_A ) ); + TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &N, &N_limbs, input_N ) ); + TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &X, &X_limbs, input_X ) ); + ASSERT_ALLOC( Y, N_limbs ); + + TEST_EQUAL( A_limbs, N_limbs ); + TEST_EQUAL( X_limbs, N_limbs ); + + N_mpi.s = 1; + N_mpi.p = N; + N_mpi.n = N_limbs; + TEST_EQUAL( 0, mbedtls_mpi_core_get_mont_r2_unsafe( &R2_mpi, &N_mpi ) ); + TEST_EQUAL( 0, mbedtls_mpi_grow( &R2_mpi, N_limbs ) ); + R2 = R2_mpi.p; + + size_t working_limbs = mbedtls_mpi_mod_raw_inv_prime_working_limbs( N_limbs ); + + /* No point exactly duplicating the code in mbedtls_mpi_mod_raw_inv_prime_working_limbs() + * to see if the output is correct, but we can check that it's in a + * reasonable range. The current calculation works out as + * `1 + N_limbs * (welem + 4)`, where welem is the number of elements in + * the window (1 << 1 up to 1 << 6). + */ + size_t min_expected_working_limbs = 1 + N_limbs * 5; + size_t max_expected_working_limbs = 1 + N_limbs * 68; + + TEST_LE_U( min_expected_working_limbs, working_limbs ); + TEST_LE_U( working_limbs, max_expected_working_limbs ); + + ASSERT_ALLOC( T, working_limbs ); + + mbedtls_mpi_mod_raw_inv_prime( Y, A, N, N_limbs, R2, T ); + + TEST_EQUAL( 0, memcmp( X, Y, N_limbs * sizeof( mbedtls_mpi_uint ) ) ); + + /* Check when output aliased to input */ + + mbedtls_mpi_mod_raw_inv_prime( A, A, N, N_limbs, R2, T ); + + TEST_EQUAL( 0, memcmp( X, A, N_limbs * sizeof( mbedtls_mpi_uint ) ) ); + +exit: + mbedtls_free( T ); + mbedtls_free( A ); + mbedtls_free( N ); + mbedtls_free( X ); + mbedtls_free( Y ); + mbedtls_mpi_free( &R2_mpi ); + // R2 doesn't need to be freed as it is only aliasing R2_mpi + // N_mpi doesn't need to be freed as it is only aliasing N +} +/* END_CASE */ + /* END MERGE SLOT 3 */ /* BEGIN MERGE SLOT 4 */