Test the validity of the sign bit after constructing an MPI object
This is mostly to look for cases where the sign bit may have been left at 0
after zerozing memory, or a value of 0 with the sign bit set to -11. Both of
these mostly work fine, so they can go otherwise undetected by unit tests,
but they can break when certain combinations of functions are used.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index eaede01..d45d3dc 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -6,6 +6,18 @@
#define MPI_MAX_BITS_LARGER_THAN_792
#endif
+/* Check the validity of the sign bit in an MPI object. Reject representations
+ * that are not supported by the rest of the library and indicate a bug when
+ * constructing the value. */
+static int sign_is_valid( const mbedtls_mpi *X )
+{
+ if( X->s != 1 && X->s != -1 )
+ return( 0 ); // invalid sign bit, e.g. 0
+ if( mbedtls_mpi_bitlen( X ) == 0 && X->s != 1 )
+ return( 0 ); // negative zero
+ return( 1 );
+}
+
typedef struct mbedtls_test_mpi_random
{
data_t *data;
@@ -150,6 +162,7 @@
TEST_ASSERT( mbedtls_mpi_read_string( &X, radix_X, input_X ) == result_read );
if( result_read == 0 )
{
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_write_string( &X, radix_A, str, output_size, &len ) == result_write );
if( result_write == 0 )
{
@@ -174,6 +187,7 @@
TEST_ASSERT( mbedtls_mpi_read_binary( &X, buf->x, buf->len ) == 0 );
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_write_string( &X, radix_A, str, sizeof( str ), &len ) == 0 );
TEST_ASSERT( strcmp( (char *) str, input_A ) == 0 );
@@ -193,6 +207,7 @@
TEST_ASSERT( mbedtls_mpi_read_binary_le( &X, buf->x, buf->len ) == 0 );
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_write_string( &X, radix_A, str, sizeof( str ), &len ) == 0 );
TEST_ASSERT( strcmp( (char *) str, input_A ) == 0 );
@@ -287,6 +302,7 @@
if( result == 0 )
{
+ TEST_ASSERT( sign_is_valid( &X ) );
buflen = mbedtls_mpi_size( &X );
TEST_ASSERT( mbedtls_mpi_write_binary( &X, buf, buflen ) == 0 );
@@ -357,6 +373,7 @@
if( result == 0 )
{
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &Y ) == 0 );
}
@@ -404,6 +421,7 @@
TEST_ASSERT( mbedtls_test_read_mpi( &Y, radix_Y, input_Y ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &A, radix_A, input_A ) == 0 );
TEST_ASSERT( mbedtls_mpi_gcd( &Z, &X, &Y ) == 0 );
+ TEST_ASSERT( sign_is_valid( &Z ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Z, &A ) == 0 );
exit:
@@ -492,6 +510,7 @@
TEST_ASSERT( mbedtls_mpi_lset( &Y, input_Y ) == 0 );
TEST_ASSERT( mbedtls_mpi_copy( &Y, &X ) == 0 );
+ TEST_ASSERT( sign_is_valid( &Y ) );
TEST_ASSERT( mbedtls_mpi_cmp_int( &X, input_X ) == 0 );
TEST_ASSERT( mbedtls_mpi_cmp_int( &Y, input_X ) == 0 );
@@ -512,6 +531,7 @@
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &X0 ) == 0 );
TEST_ASSERT( mbedtls_mpi_copy( &Y, &X ) == 0 );
+ TEST_ASSERT( sign_is_valid( &Y ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &X0 ) == 0 );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Y, &X0 ) == 0 );
@@ -566,9 +586,11 @@
TEST_ASSERT( mbedtls_mpi_copy( &XX, &X ) == 0 );
TEST_ASSERT( mbedtls_mpi_safe_cond_assign( &X, &Y, 0 ) == 0 );
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &XX ) == 0 );
TEST_ASSERT( mbedtls_mpi_safe_cond_assign( &X, &Y, 1 ) == 0 );
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &Y ) == 0 );
exit:
@@ -594,10 +616,14 @@
TEST_ASSERT( mbedtls_mpi_copy( &YY, &Y ) == 0 );
TEST_ASSERT( mbedtls_mpi_safe_cond_swap( &X, &Y, 0 ) == 0 );
+ TEST_ASSERT( sign_is_valid( &X ) );
+ TEST_ASSERT( sign_is_valid( &Y ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &XX ) == 0 );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Y, &YY ) == 0 );
TEST_ASSERT( mbedtls_mpi_safe_cond_swap( &X, &Y, 1 ) == 0 );
+ TEST_ASSERT( sign_is_valid( &X ) );
+ TEST_ASSERT( sign_is_valid( &Y ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Y, &XX ) == 0 );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &YY ) == 0 );
@@ -619,6 +645,8 @@
TEST_ASSERT( mbedtls_mpi_cmp_int( &Y, input_Y ) == 0 );
mbedtls_mpi_swap( &X, &Y );
+ TEST_ASSERT( sign_is_valid( &X ) );
+ TEST_ASSERT( sign_is_valid( &Y ) );
TEST_ASSERT( mbedtls_mpi_cmp_int( &X, input_Y ) == 0 );
TEST_ASSERT( mbedtls_mpi_cmp_int( &Y, input_X ) == 0 );
@@ -640,6 +668,8 @@
TEST_ASSERT( mbedtls_mpi_read_binary( &Y0, input_Y->x, input_Y->len ) == 0 );
mbedtls_mpi_swap( &X, &Y );
+ TEST_ASSERT( sign_is_valid( &X ) );
+ TEST_ASSERT( sign_is_valid( &Y ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &Y0 ) == 0 );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Y, &X0 ) == 0 );
@@ -659,6 +689,7 @@
TEST_ASSERT( mbedtls_mpi_read_binary( &X0, input_X->x, input_X->len ) == 0 );
mbedtls_mpi_swap( &X, &X );
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &X0 ) == 0 );
exit:
@@ -677,15 +708,18 @@
TEST_ASSERT( mbedtls_test_read_mpi( &Y, radix_Y, input_Y ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &A, radix_A, input_A ) == 0 );
TEST_ASSERT( mbedtls_mpi_add_mpi( &Z, &X, &Y ) == 0 );
+ TEST_ASSERT( sign_is_valid( &Z ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Z, &A ) == 0 );
/* result == first operand */
TEST_ASSERT( mbedtls_mpi_add_mpi( &X, &X, &Y ) == 0 );
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &A ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &X, radix_X, input_X ) == 0 );
/* result == second operand */
TEST_ASSERT( mbedtls_mpi_add_mpi( &Y, &X, &Y ) == 0 );
+ TEST_ASSERT( sign_is_valid( &Y ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Y, &A ) == 0 );
exit:
@@ -705,13 +739,16 @@
TEST_ASSERT( mbedtls_test_read_mpi( &X, radix_X, input_X ) == 0 );
TEST_ASSERT( mbedtls_mpi_sub_abs( &X, &X, &X ) == 0 );
TEST_ASSERT( mbedtls_mpi_cmp_int( &X, 0 ) == 0 );
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_test_read_mpi( &X, radix_X, input_X ) == 0 );
TEST_ASSERT( mbedtls_mpi_add_abs( &X, &X, &X ) == 0 );
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &A ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &X, radix_X, input_X ) == 0 );
TEST_ASSERT( mbedtls_mpi_add_mpi( &X, &X, &X ) == 0 );
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &A ) == 0 );
exit:
@@ -731,15 +768,18 @@
TEST_ASSERT( mbedtls_test_read_mpi( &Y, radix_Y, input_Y ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &A, radix_A, input_A ) == 0 );
TEST_ASSERT( mbedtls_mpi_add_abs( &Z, &X, &Y ) == 0 );
+ TEST_ASSERT( sign_is_valid( &Z ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Z, &A ) == 0 );
/* result == first operand */
TEST_ASSERT( mbedtls_mpi_add_abs( &X, &X, &Y ) == 0 );
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &A ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &X, radix_X, input_X ) == 0 );
/* result == second operand */
TEST_ASSERT( mbedtls_mpi_add_abs( &Y, &X, &Y ) == 0 );
+ TEST_ASSERT( sign_is_valid( &Y ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Y, &A ) == 0 );
exit:
@@ -757,6 +797,7 @@
TEST_ASSERT( mbedtls_test_read_mpi( &X, radix_X, input_X ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &A, radix_A, input_A ) == 0 );
TEST_ASSERT( mbedtls_mpi_add_int( &Z, &X, input_Y ) == 0 );
+ TEST_ASSERT( sign_is_valid( &Z ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Z, &A ) == 0 );
exit:
@@ -775,15 +816,18 @@
TEST_ASSERT( mbedtls_test_read_mpi( &Y, radix_Y, input_Y ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &A, radix_A, input_A ) == 0 );
TEST_ASSERT( mbedtls_mpi_sub_mpi( &Z, &X, &Y ) == 0 );
+ TEST_ASSERT( sign_is_valid( &Z ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Z, &A ) == 0 );
/* result == first operand */
TEST_ASSERT( mbedtls_mpi_sub_mpi( &X, &X, &Y ) == 0 );
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &A ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &X, radix_X, input_X ) == 0 );
/* result == second operand */
TEST_ASSERT( mbedtls_mpi_sub_mpi( &Y, &X, &Y ) == 0 );
+ TEST_ASSERT( sign_is_valid( &Y ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Y, &A ) == 0 );
exit:
@@ -806,17 +850,20 @@
res = mbedtls_mpi_sub_abs( &Z, &X, &Y );
TEST_ASSERT( res == sub_result );
+ TEST_ASSERT( sign_is_valid( &Z ) );
if( res == 0 )
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Z, &A ) == 0 );
/* result == first operand */
TEST_ASSERT( mbedtls_mpi_sub_abs( &X, &X, &Y ) == sub_result );
+ TEST_ASSERT( sign_is_valid( &X ) );
if( sub_result == 0 )
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &A ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &X, radix_X, input_X ) == 0 );
/* result == second operand */
TEST_ASSERT( mbedtls_mpi_sub_abs( &Y, &X, &Y ) == sub_result );
+ TEST_ASSERT( sign_is_valid( &Y ) );
if( sub_result == 0 )
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Y, &A ) == 0 );
@@ -835,6 +882,7 @@
TEST_ASSERT( mbedtls_test_read_mpi( &X, radix_X, input_X ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &A, radix_A, input_A ) == 0 );
TEST_ASSERT( mbedtls_mpi_sub_int( &Z, &X, input_Y ) == 0 );
+ TEST_ASSERT( sign_is_valid( &Z ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Z, &A ) == 0 );
exit:
@@ -853,6 +901,7 @@
TEST_ASSERT( mbedtls_test_read_mpi( &Y, radix_Y, input_Y ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &A, radix_A, input_A ) == 0 );
TEST_ASSERT( mbedtls_mpi_mul_mpi( &Z, &X, &Y ) == 0 );
+ TEST_ASSERT( sign_is_valid( &Z ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Z, &A ) == 0 );
exit:
@@ -871,6 +920,7 @@
TEST_ASSERT( mbedtls_test_read_mpi( &X, radix_X, input_X ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &A, radix_A, input_A ) == 0 );
TEST_ASSERT( mbedtls_mpi_mul_int( &Z, &X, input_Y ) == 0 );
+ TEST_ASSERT( sign_is_valid( &Z ) );
if( strcmp( result_comparison, "==" ) == 0 )
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Z, &A ) == 0 );
else if( strcmp( result_comparison, "!=" ) == 0 )
@@ -901,6 +951,8 @@
TEST_ASSERT( res == div_result );
if( res == 0 )
{
+ TEST_ASSERT( sign_is_valid( &Q ) );
+ TEST_ASSERT( sign_is_valid( &R ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Q, &A ) == 0 );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &R, &B ) == 0 );
}
@@ -928,6 +980,8 @@
TEST_ASSERT( res == div_result );
if( res == 0 )
{
+ TEST_ASSERT( sign_is_valid( &Q ) );
+ TEST_ASSERT( sign_is_valid( &R ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Q, &A ) == 0 );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &R, &B ) == 0 );
}
@@ -954,6 +1008,7 @@
TEST_ASSERT( res == div_result );
if( res == 0 )
{
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &A ) == 0 );
}
@@ -1007,6 +1062,7 @@
TEST_ASSERT( res == div_result );
if( res == 0 )
{
+ TEST_ASSERT( sign_is_valid( &Z ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Z, &X ) == 0 );
}
@@ -1066,6 +1122,7 @@
TEST_ASSERT( res == div_result );
if( res == 0 )
{
+ TEST_ASSERT( sign_is_valid( &Z ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &Z, &A ) == 0 );
}
@@ -1141,6 +1198,7 @@
TEST_ASSERT( actual_bits >= (size_t) bits );
TEST_ASSERT( actual_bits <= (size_t) bits + 1 );
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_is_prime_ext( &X, 40,
mbedtls_test_rnd_std_rand,
@@ -1170,6 +1228,7 @@
TEST_ASSERT( mbedtls_test_read_mpi( &X, radix_X, input_X ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &A, radix_A, input_A ) == 0 );
TEST_ASSERT( mbedtls_mpi_shift_l( &X, shift_X ) == 0 );
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &A ) == 0 );
exit:
@@ -1187,6 +1246,7 @@
TEST_ASSERT( mbedtls_test_read_mpi( &X, radix_X, input_X ) == 0 );
TEST_ASSERT( mbedtls_test_read_mpi( &A, radix_A, input_A ) == 0 );
TEST_ASSERT( mbedtls_mpi_shift_r( &X, shift_X ) == 0 );
+ TEST_ASSERT( sign_is_valid( &X ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &X, &A ) == 0 );
exit:
@@ -1228,6 +1288,7 @@
TEST_ASSERT( mbedtls_mpi_size( &X ) + leading_zeros ==
(size_t) wanted_bytes );
TEST_ASSERT( (int) bytes_left == rng_bytes - wanted_bytes );
+ TEST_ASSERT( sign_is_valid( &X ) );
}
exit:
@@ -1285,6 +1346,7 @@
TEST_EQUAL( 0, mbedtls_mpi_random( &result, min, &upper_bound,
mbedtls_test_rnd_std_rand, NULL ) );
+ TEST_ASSERT( sign_is_valid( &result ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &result, &upper_bound ) < 0 );
TEST_ASSERT( mbedtls_mpi_cmp_int( &result, min ) >= 0 );
if( full_stats )
@@ -1366,6 +1428,7 @@
bound_bytes->x, bound_bytes->len ) );
TEST_EQUAL( 0, mbedtls_mpi_random( &result, min, &upper_bound,
mbedtls_test_rnd_std_rand, NULL ) );
+ TEST_ASSERT( sign_is_valid( &result ) );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &result, &upper_bound ) < 0 );
TEST_ASSERT( mbedtls_mpi_cmp_int( &result, min ) >= 0 );