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Merge pull request #6230 from tom-cosgrove-arm/issue-6223-core-add

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Bignum: extract core_add from the prototype
This commit is contained in:
Gilles Peskine 2022-10-27 11:25:27 +02:00 committed by GitHub
commit 9603daddaa
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GPG Key ID: 4AEE18F83AFDEB23
5 changed files with 213 additions and 73 deletions
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31
library/bignum.c
View File

@ -867,8 +867,7 @@ int mbedtls_mpi_cmp_int( const mbedtls_mpi *X, mbedtls_mpi_sint z )
int mbedtls_mpi_add_abs( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi *B )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t i, j;
mbedtls_mpi_uint *o, *p, c, tmp;
size_t j;
MPI_VALIDATE_RET( X != NULL );
MPI_VALIDATE_RET( A != NULL );
MPI_VALIDATE_RET( B != NULL );
@ -882,7 +881,7 @@ int mbedtls_mpi_add_abs( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
MBEDTLS_MPI_CHK( mbedtls_mpi_copy( X, A ) );
/*
* X should always be positive as a result of unsigned additions.
* X must always be positive as a result of unsigned additions.
*/
X->s = 1;
@ -892,27 +891,25 @@ int mbedtls_mpi_add_abs( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( X, j ) );
o = B->p; p = X->p; c = 0;
/* j is the number of non-zero limbs of B. Add those to X. */
/*
* tmp is used because it might happen that p == o
*/
for( i = 0; i < j; i++, o++, p++ )
{
tmp= *o;
*p += c; c = ( *p < c );
*p += tmp; c += ( *p < tmp );
}
mbedtls_mpi_uint *p = X->p;
mbedtls_mpi_uint c = mbedtls_mpi_core_add( p, p, B->p, j );
p += j;
/* Now propagate any carry */
while( c != 0 )
{
if( i >= X->n )
if( j >= X->n )
{
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( X, i + 1 ) );
p = X->p + i;
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( X, j + 1 ) );
p = X->p + j;
}
*p += c; c = ( *p < c ); i++; p++;
*p += c; c = ( *p < c ); j++; p++;
}
cleanup:

19
library/bignum_core.c
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@ -316,8 +316,6 @@ int mbedtls_mpi_core_write_be( const mbedtls_mpi_uint *X,
return( 0 );
}
void mbedtls_mpi_core_shift_r( mbedtls_mpi_uint *X, size_t limbs,
size_t count )
{
@ -360,7 +358,24 @@ void mbedtls_mpi_core_shift_r( mbedtls_mpi_uint *X, size_t limbs,
}
}
mbedtls_mpi_uint mbedtls_mpi_core_add( mbedtls_mpi_uint *X,
const mbedtls_mpi_uint *A,
const mbedtls_mpi_uint *B,
size_t limbs )
{
mbedtls_mpi_uint c = 0;
for( size_t i = 0; i < limbs; i++ )
{
mbedtls_mpi_uint t = c + A[i];
c = ( t < A[i] );
t += B[i];
c += ( t < B[i] );
X[i] = t;
}
return( c );
}
mbedtls_mpi_uint mbedtls_mpi_core_add_if( mbedtls_mpi_uint *X,
const mbedtls_mpi_uint *A,

22
library/bignum_core.h
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@ -277,6 +277,28 @@ int mbedtls_mpi_core_write_be( const mbedtls_mpi_uint *A,
void mbedtls_mpi_core_shift_r( mbedtls_mpi_uint *X, size_t limbs,
size_t count );
/**
* \brief Add two fixed-size large unsigned integers, returning the carry.
*
* Calculates `A + B` where `A` and `B` have the same size.
*
* This function operates modulo `2^(biL*limbs)` and returns the carry
* (1 if there was a wraparound, and 0 otherwise).
*
* \p X may be aliased to \p A or \p B.
*
* \param[out] X The result of the addition.
* \param[in] A Little-endian presentation of the left operand.
* \param[in] B Little-endian presentation of the right operand.
* \param limbs Number of limbs of \p X, \p A and \p B.
*
* \return 1 if `A + B >= 2^(biL*limbs)`, 0 otherwise.
*/
mbedtls_mpi_uint mbedtls_mpi_core_add( mbedtls_mpi_uint *X,
const mbedtls_mpi_uint *A,
const mbedtls_mpi_uint *B,
size_t limbs );
/**
* \brief Conditional addition of two fixed-size large unsigned integers,
* returning the carry.

8
scripts/mbedtls_dev/bignum_core.py
View File

@ -144,12 +144,12 @@ class BignumCoreOperationArchSplit(BignumCoreOperation):
yield cls(a_value, b_value, 32).create_test_case()
yield cls(a_value, b_value, 64).create_test_case()
class BignumCoreAddIf(BignumCoreOperationArchSplit):
"""Test cases for bignum core add if."""
class BignumCoreAddAndAddIf(BignumCoreOperationArchSplit):
"""Test cases for bignum core add and add-if."""
count = 0
symbol = "+"
test_function = "mpi_core_add_if"
test_name = "mbedtls_mpi_core_add_if"
test_function = "mpi_core_add_and_add_if"
test_name = "mpi_core_add_and_add_if"
def result(self) -> List[str]:
result = self.int_a + self.int_b

206
tests/suites/test_suite_bignum_core.function
View File

@ -5,6 +5,154 @@
#include "constant_time_internal.h"
#include "test/constant_flow.h"
/** Verifies mbedtls_mpi_core_add().
*
* \param[in] A Little-endian presentation of the left operand.
* \param[in] B Little-endian presentation of the right operand.
* \param limbs Number of limbs in each MPI (\p A, \p B, \p S and \p X).
* \param[in] S Little-endian presentation of the expected sum.
* \param carry Expected carry from the addition.
* \param[in,out] X Temporary storage to be used for results.
*
* \return 1 if mbedtls_mpi_core_add() passes this test, otherwise 0.
*/
static int mpi_core_verify_add( mbedtls_mpi_uint *A,
mbedtls_mpi_uint *B,
size_t limbs,
mbedtls_mpi_uint *S,
int carry,
mbedtls_mpi_uint *X )
{
int ret = 0;
size_t bytes = limbs * sizeof( *A );
/* The test cases have A <= B to avoid repetition, so we test A + B then,
* if A != B, B + A. If A == B, we can test when A and B are aliased */
/* A + B */
/* A + B => correct result and carry */
TEST_EQUAL( carry, mbedtls_mpi_core_add( X, A, B, limbs ) );
ASSERT_COMPARE( X, bytes, S, bytes );
/* A + B; alias output and first operand => correct result and carry */
memcpy( X, A, bytes );
TEST_EQUAL( carry, mbedtls_mpi_core_add( X, X, B, limbs ) );
ASSERT_COMPARE( X, bytes, S, bytes );
/* A + B; alias output and second operand => correct result and carry */
memcpy( X, B, bytes );
TEST_EQUAL( carry, mbedtls_mpi_core_add( X, A, X, limbs ) );
ASSERT_COMPARE( X, bytes, S, bytes );
if ( memcmp( A, B, bytes ) == 0 )
{
/* A == B, so test where A and B are aliased */
/* A + A => correct result and carry */
TEST_EQUAL( carry, mbedtls_mpi_core_add( X, A, A, limbs ) );
ASSERT_COMPARE( X, bytes, S, bytes );
/* A + A, output aliased to both operands => correct result and carry */
memcpy( X, A, bytes );
TEST_EQUAL( carry, mbedtls_mpi_core_add( X, X, X, limbs ) );
ASSERT_COMPARE( X, bytes, S, bytes );
}
else
{
/* A != B, so test B + A */
/* B + A => correct result and carry */
TEST_EQUAL( carry, mbedtls_mpi_core_add( X, B, A, limbs ) );
ASSERT_COMPARE( X, bytes, S, bytes );
/* B + A; alias output and first operand => correct result and carry */
memcpy( X, B, bytes );
TEST_EQUAL( carry, mbedtls_mpi_core_add( X, X, A, limbs ) );
ASSERT_COMPARE( X, bytes, S, bytes );
/* B + A; alias output and second operand => correct result and carry */
memcpy( X, A, bytes );
TEST_EQUAL( carry, mbedtls_mpi_core_add( X, B, X, limbs ) );
ASSERT_COMPARE( X, bytes, S, bytes );
}
ret = 1;
exit:
return ret;
}
/** Verifies mbedtls_mpi_core_add_if().
*
* \param[in] A Little-endian presentation of the left operand.
* \param[in] B Little-endian presentation of the right operand.
* \param limbs Number of limbs in each MPI (\p A, \p B, \p S and \p X).
* \param[in] S Little-endian presentation of the expected sum.
* \param carry Expected carry from the addition.
* \param[in,out] X Temporary storage to be used for results.
*
* \return 1 if mbedtls_mpi_core_add_if() passes this test, otherwise 0.
*/
static int mpi_core_verify_add_if( mbedtls_mpi_uint *A,
mbedtls_mpi_uint *B,
size_t limbs,
mbedtls_mpi_uint *S,
int carry,
mbedtls_mpi_uint *X )
{
int ret = 0;
size_t bytes = limbs * sizeof( *A );
/* The test cases have A <= B to avoid repetition, so we test A + B then,
* if A != B, B + A. If A == B, we can test when A and B are aliased */
/* A + B */
/* cond = 0 => X unchanged, no carry */
memcpy( X, A, bytes );
TEST_EQUAL( 0, mbedtls_mpi_core_add_if( X, B, limbs, 0 ) );
ASSERT_COMPARE( X, bytes, A, bytes );
/* cond = 1 => correct result and carry */
TEST_EQUAL( carry, mbedtls_mpi_core_add_if( X, B, limbs, 1 ) );
ASSERT_COMPARE( X, bytes, S, bytes );
if ( memcmp( A, B, bytes ) == 0 )
{
/* A == B, so test where A and B are aliased */
/* cond = 0 => X unchanged, no carry */
memcpy( X, B, bytes );
TEST_EQUAL( 0, mbedtls_mpi_core_add_if( X, X, limbs, 0 ) );
ASSERT_COMPARE( X, bytes, B, bytes );
/* cond = 1 => correct result and carry */
TEST_EQUAL( carry, mbedtls_mpi_core_add_if( X, X, limbs, 1 ) );
ASSERT_COMPARE( X, bytes, S, bytes );
}
else
{
/* A != B, so test B + A */
/* cond = 0 => d unchanged, no carry */
memcpy( X, B, bytes );
TEST_EQUAL( 0, mbedtls_mpi_core_add_if( X, A, limbs, 0 ) );
ASSERT_COMPARE( X, bytes, B, bytes );
/* cond = 1 => correct result and carry */
TEST_EQUAL( carry, mbedtls_mpi_core_add_if( X, A, limbs, 1 ) );
ASSERT_COMPARE( X, bytes, S, bytes );
}
ret = 1;
exit:
return ret;
}
/* END_HEADER */
/* BEGIN_DEPENDENCIES
@ -359,70 +507,28 @@ exit:
/* END_CASE */
/* BEGIN_CASE */
void mpi_core_add_if( char * input_A, char * input_B,
char * input_S, int carry )
void mpi_core_add_and_add_if( char * input_A, char * input_B,
char * input_S, int carry )
{
mbedtls_mpi_uint *A = NULL; /* first value to add */
size_t A_limbs;
mbedtls_mpi_uint *B = NULL; /* second value to add */
size_t B_limbs;
mbedtls_mpi_uint *S = NULL; /* expected result */
size_t S_limbs;
mbedtls_mpi_uint *X = NULL; /* destination - the in/out first operand */
size_t X_limbs;
size_t A_limbs, B_limbs, S_limbs;
TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &A, &A_limbs, input_A ) );
TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &B, &B_limbs, input_B ) );
TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &S, &S_limbs, input_S ) );
X_limbs = S_limbs;
ASSERT_ALLOC( X, X_limbs );
/* add_if expects all operands to be the same length */
/* add and add_if expect all operands to be the same length */
TEST_EQUAL( A_limbs, B_limbs );
TEST_EQUAL( A_limbs, S_limbs );
size_t limbs = A_limbs;
size_t bytes = limbs * sizeof( *A );
ASSERT_ALLOC( X, limbs );
/* The test cases have A <= B to avoid repetition, so we test A + B then,
* if A != B, B + A. If A == B, we can test when A and B are aliased */
/* A + B */
/* cond = 0 => X unchanged, no carry */
memcpy( X, A, bytes );
TEST_EQUAL( 0, mbedtls_mpi_core_add_if( X, B, limbs, 0 ) );
ASSERT_COMPARE( X, bytes, A, bytes );
/* cond = 1 => correct result and carry */
TEST_EQUAL( carry, mbedtls_mpi_core_add_if( X, B, limbs, 1 ) );
ASSERT_COMPARE( X, bytes, S, bytes );
if ( memcmp( A, B, bytes ) == 0 )
{
/* A == B, so test where A and B are aliased */
/* cond = 0 => X unchanged, no carry */
memcpy( X, B, bytes );
TEST_EQUAL( 0, mbedtls_mpi_core_add_if( X, X, limbs, 0 ) );
ASSERT_COMPARE( X, bytes, B, bytes );
/* cond = 1 => correct result and carry */
TEST_EQUAL( carry, mbedtls_mpi_core_add_if( X, X, limbs, 1 ) );
ASSERT_COMPARE( X, bytes, S, bytes );
}
else
{
/* A != B, so test B + A */
/* cond = 0 => d unchanged, no carry */
memcpy( X, B, bytes );
TEST_EQUAL( 0, mbedtls_mpi_core_add_if( X, A, limbs, 0 ) );
ASSERT_COMPARE( X, bytes, B, bytes );
/* cond = 1 => correct result and carry */
TEST_EQUAL( carry, mbedtls_mpi_core_add_if( X, A, limbs, 1 ) );
ASSERT_COMPARE( X, bytes, S, bytes );
}
TEST_ASSERT( mpi_core_verify_add( A, B, limbs, S, carry, X ) );
TEST_ASSERT( mpi_core_verify_add_if( A, B, limbs, S, carry, X ) );
exit:
mbedtls_free( A );