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Merge pull request #6609 from gilles-peskine-arm/mpi_sint-min-ub

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Fix undefined behavior in bignum: NULL+0 and -most-negative-sint
This commit is contained in:
Gilles Peskine
2022-11-21 19:51:58 +01:00
committed by GitHub
parent 8b85b4835e ef7f4e47b1
commit 339406daf9
6 changed files with 190 additions and 5 deletions
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144
tests/suites/test_suite_bignum.function
View File

@@ -1458,6 +1458,150 @@ exit:
}
/* END_CASE */
/* BEGIN_CASE */
void most_negative_mpi_sint( )
{
/* Ad hoc tests for n = -p = -2^(biL-1) as a mbedtls_mpi_sint. We
* guarantee that mbedtls_mpi_sint is a two's complement type, so this
* is a valid value. However, negating it (`-n`) has undefined behavior
* (although in practice `-n` evaluates to the value n).
*
* This function has ad hoc tests for this value. It's separated from other
* functions because the test framework makes it hard to pass this value
* into test cases.
*
* In the comments here:
* - biL = number of bits in limbs
* - p = 2^(biL-1) (smallest positive value not in mbedtls_mpi_sint range)
* - n = -2^(biL-1) (largest negative value in mbedtls_mpi_sint range)
*/
mbedtls_mpi A, R, X;
mbedtls_mpi_init( &A );
mbedtls_mpi_init( &R );
mbedtls_mpi_init( &X );
const size_t biL = 8 * sizeof( mbedtls_mpi_sint );
mbedtls_mpi_uint most_positive_plus_1 = (mbedtls_mpi_uint) 1 << ( biL - 1 );
const mbedtls_mpi_sint most_positive = most_positive_plus_1 - 1;
const mbedtls_mpi_sint most_negative = - most_positive - 1;
TEST_EQUAL( (mbedtls_mpi_uint) most_negative,
(mbedtls_mpi_uint) 1 << ( biL - 1 ) );
TEST_EQUAL( (mbedtls_mpi_uint) most_negative << 1, 0 );
/* Test mbedtls_mpi_lset() */
TEST_EQUAL( mbedtls_mpi_lset( &A, most_negative ), 0 );
TEST_EQUAL( A.s, -1 );
TEST_EQUAL( A.n, 1 );
TEST_EQUAL( A.p[0], most_positive_plus_1 );
/* Test mbedtls_mpi_cmp_int(): -p == -p */
TEST_EQUAL( mbedtls_mpi_cmp_int( &A, most_negative ), 0 );
/* Test mbedtls_mpi_cmp_int(): -(p+1) < -p */
A.p[0] = most_positive_plus_1 + 1;
TEST_EQUAL( mbedtls_mpi_cmp_int( &A, most_negative ), -1 );
/* Test mbedtls_mpi_cmp_int(): -(p-1) > -p */
A.p[0] = most_positive_plus_1 - 1;
TEST_EQUAL( mbedtls_mpi_cmp_int( &A, most_negative ), 1 );
/* Test mbedtls_mpi_add_int(): (p-1) + (-p) */
TEST_EQUAL( mbedtls_mpi_lset( &A, most_positive ), 0 );
TEST_EQUAL( mbedtls_mpi_add_int( &X, &A, most_negative ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &X, -1 ), 0 );
/* Test mbedtls_mpi_add_int(): (0) + (-p) */
TEST_EQUAL( mbedtls_mpi_lset( &A, 0 ), 0 );
TEST_EQUAL( mbedtls_mpi_add_int( &X, &A, most_negative ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &X, most_negative ), 0 );
/* Test mbedtls_mpi_add_int(): (-p) + (-p) */
TEST_EQUAL( mbedtls_mpi_lset( &A, most_negative ), 0 );
TEST_EQUAL( mbedtls_mpi_add_int( &X, &A, most_negative ), 0 );
TEST_EQUAL( X.s, -1 );
TEST_EQUAL( X.n, 2 );
TEST_EQUAL( X.p[0], 0 );
TEST_EQUAL( X.p[1], 1 );
/* Test mbedtls_mpi_sub_int(): (p) - (-p) */
mbedtls_mpi_free( &X );
TEST_EQUAL( mbedtls_mpi_lset( &A, most_positive ), 0 );
TEST_EQUAL( mbedtls_mpi_sub_int( &X, &A, most_negative ), 0 );
TEST_EQUAL( X.s, 1 );
TEST_EQUAL( X.n, 1 );
TEST_EQUAL( X.p[0], ~(mbedtls_mpi_uint)0 );
/* Test mbedtls_mpi_sub_int(): (0) - (-p) */
TEST_EQUAL( mbedtls_mpi_lset( &A, 0 ), 0 );
TEST_EQUAL( mbedtls_mpi_sub_int( &X, &A, most_negative ), 0 );
TEST_EQUAL( X.s, 1 );
TEST_EQUAL( X.n, 1 );
TEST_EQUAL( X.p[0], most_positive_plus_1 );
/* Test mbedtls_mpi_sub_int(): (-p) - (-p) */
TEST_EQUAL( mbedtls_mpi_lset( &A, most_negative ), 0 );
TEST_EQUAL( mbedtls_mpi_sub_int( &X, &A, most_negative ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &X, 0 ), 0 );
/* Test mbedtls_mpi_div_int(): (-p+1) / (-p) */
TEST_EQUAL( mbedtls_mpi_lset( &A, -most_positive ), 0 );
TEST_EQUAL( mbedtls_mpi_div_int( &X, &R, &A, most_negative ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &X, 0 ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &R, -most_positive ), 0 );
/* Test mbedtls_mpi_div_int(): (-p) / (-p) */
TEST_EQUAL( mbedtls_mpi_lset( &A, most_negative ), 0 );
TEST_EQUAL( mbedtls_mpi_div_int( &X, &R, &A, most_negative ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &X, 1 ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &R, 0 ), 0 );
/* Test mbedtls_mpi_div_int(): (-2*p) / (-p) */
TEST_EQUAL( mbedtls_mpi_shift_l( &A, 1 ), 0 );
TEST_EQUAL( mbedtls_mpi_div_int( &X, &R, &A, most_negative ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &X, 2 ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &R, 0 ), 0 );
/* Test mbedtls_mpi_div_int(): (-2*p+1) / (-p) */
TEST_EQUAL( mbedtls_mpi_add_int( &A, &A, 1 ), 0 );
TEST_EQUAL( mbedtls_mpi_div_int( &X, &R, &A, most_negative ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &X, 1 ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &R, -most_positive ), 0 );
/* Test mbedtls_mpi_div_int(): (p-1) / (-p) */
TEST_EQUAL( mbedtls_mpi_lset( &A, most_positive ), 0 );
TEST_EQUAL( mbedtls_mpi_div_int( &X, &R, &A, most_negative ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &X, 0 ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &R, most_positive ), 0 );
/* Test mbedtls_mpi_div_int(): (p) / (-p) */
TEST_EQUAL( mbedtls_mpi_add_int( &A, &A, 1 ), 0 );
TEST_EQUAL( mbedtls_mpi_div_int( &X, &R, &A, most_negative ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &X, -1 ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &R, 0 ), 0 );
/* Test mbedtls_mpi_div_int(): (2*p) / (-p) */
TEST_EQUAL( mbedtls_mpi_shift_l( &A, 1 ), 0 );
TEST_EQUAL( mbedtls_mpi_div_int( &X, &R, &A, most_negative ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &X, -2 ), 0 );
TEST_EQUAL( mbedtls_mpi_cmp_int( &R, 0 ), 0 );
/* Test mbedtls_mpi_mod_int(): never valid */
TEST_EQUAL( mbedtls_mpi_mod_int( X.p, &A, most_negative ),
MBEDTLS_ERR_MPI_NEGATIVE_VALUE );
/* Test mbedtls_mpi_random(): never valid */
TEST_EQUAL( mbedtls_mpi_random( &X, most_negative, &A,
mbedtls_test_rnd_std_rand, NULL ),
MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
exit:
mbedtls_mpi_free( &A );
mbedtls_mpi_free( &R );
mbedtls_mpi_free( &X );
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_SELF_TEST */
void mpi_selftest( )
{

3
tests/suites/test_suite_bignum.misc.data
View File

@@ -1958,6 +1958,9 @@ mpi_random_fail:2:"01":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
MPI random bad arguments: min > N = 1, 0 limb in upper bound
mpi_random_fail:2:"000000000000000001":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
Most negative mbedtls_mpi_sint
most_negative_mpi_sint:
MPI Selftest
depends_on:MBEDTLS_SELF_TEST
mpi_selftest: