bignum_mod: Adjusted input checking for mbedtls_mpi_mod_residue_setup()

This patch adjusts the logic of the size checking of the method,
and refactors the tests. Documentation has also been updated.

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>

library/bignum_mod.c

@@ -39,7 +39,7 @@ int mbedtls_mpi_mod_residue_setup( mbedtls_mpi_mod_residue *r,
                                    mbedtls_mpi_uint *p,
                                    size_t p_limbs )
 {
-    if( p_limbs > m->limbs || !mbedtls_mpi_core_lt_ct( p, m->p, m->limbs ) )
+    if( p_limbs > m->limbs || !mbedtls_mpi_core_lt_ct( p, m->p, p_limbs ) )
         return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
 
     r->limbs = m->limbs;

library/bignum_mod.h

@@ -75,16 +75,17 @@ typedef struct {
 
 /** Setup a residue structure.
  *
- * \param[out] r    The address of residue to setup. The size is determined by
+ * \param[out] r    The address of residue to setup. The resulting structure's
- *                  \p m.
+ *                  size is determined by \p m.
- *                  (In particular, it must have at least as many limbs as the
- *                  modulus \p m.)
  * \param[in] m     The address of the modulus related to \p r.
  * \param[in] p     The address of the limb array storing the value of \p r.
  *                  The memory pointed to by \p p will be used by \p r and must
  *                  not be modified in any way until after
- *                  mbedtls_mpi_mod_residue_release() is called.
+ *                  mbedtls_mpi_mod_residue_release() is called. The data
- * \param p_limbs   The number of limbs of \p p.
+ *                  pointed by p should be compatible (in terms of size/endianness)
+ *                  with the representation used in \p m.
+ * \param p_limbs   The number of limbs of \p p. It must have at most as
+ *                  many limbs as the modulus \p m.)
  *
  * \return      \c 0 if successful.
  * \return      #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if \p p_limbs is less than the

tests/suites/test_suite_bignum_mod.data

@@ -50,8 +50,29 @@ mpi_mod_setup:MBEDTLS_MPI_MOD_EXT_REP_LE:MBEDTLS_MPI_MOD_REP_MONTGOMERY:0
 # END MERGE SLOT 6
 
 # BEGIN MERGE SLOT 7
-Test mbedtls_mpi_residue_setup
+Test mbedtls_mpi_residue_setup #1 m > r
-mpi_residue_setup:
+mpi_residue_setup:"fe":"01":0
+
+Test mbedtls_mpi_residue_setup #2 r == m - 1
+mpi_residue_setup:"ff":"fe":0
+
+Test mbedtls_mpi_residue_setup #3 m->limbs > r-> limbs && m > r
+mpi_residue_setup:"000000000000000000000000000000007dfe5c6beb35a2d6":"fe":0
+
+Test mbedtls_mpi_residue_setup #4 m->limbs > r-> limbs && m > r
+mpi_residue_setup:"7ffffffffffffffffffffffffffffffffffffffffffffff1":"fe":0
+
+Test mbedtls_mpi_residue_setup #5 m->limbs > r-> limbs && m > r
+mpi_residue_setup:"7ffffffffffffffffffff000000000000000000000000000":"fe":-4
+
+Test mbedtls_mpi_residue_setup #6 m->limbs < r-> limbs && m > r
+mpi_residue_setup:"ff":"000000000000000000000000000000000000000000000001":-4
+
+Test mbedtls_mpi_residue_setup #7 r == m
+mpi_residue_setup:"fe":"fe":-4
+
+Test mbedtls_mpi_residue_setup #8 r > m
+mpi_residue_setup:"fe":"ff":-4
 
 Test mbedtls_mpi_mod_io_neg
 mpi_mod_io_neg:

tests/suites/test_suite_bignum_mod.function

@@ -81,52 +81,32 @@ exit:
 
 /* BEGIN MERGE SLOT 7 */
 /* BEGIN_CASE */
-void mpi_residue_setup( )
+void mpi_residue_setup( char * input_X, char * input_Y, int ret )
 {
-    #define RS_ONE       0
-    #define RS_MAX_MIN1  1
-    #define RS_MAX       2
-    const char * s_data[ 3 ] = { "01", "fe", "ff" };
-
     mbedtls_mpi_uint *N = NULL;
     mbedtls_mpi_uint *R = NULL;
-    mbedtls_mpi_uint *R_MAX = NULL;
+    size_t n_limbs, r_limbs;
-    size_t n_limbs, r_limbs, r_max_limbs;
     mbedtls_mpi_mod_modulus m;
     mbedtls_mpi_mod_residue r;
 
-    /* Allocate the memory for intermediate data structures */
-    TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &N, &n_limbs, s_data[ RS_MAX_MIN1 ] ) );
-    TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &R, &r_limbs, s_data[ RS_ONE ] ) );
-    TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &R_MAX, &r_max_limbs, s_data[ RS_MAX ] ) );
-
     mbedtls_mpi_mod_modulus_init( &m );
 
+    /* Allocate the memory for intermediate data structures */
+    TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &N, &n_limbs, input_X ) );
+    TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &R, &r_limbs, input_Y ) );
+
     TEST_EQUAL( 0, mbedtls_mpi_mod_modulus_setup( &m, N, n_limbs,
                 MBEDTLS_MPI_MOD_EXT_REP_LE, MBEDTLS_MPI_MOD_REP_MONTGOMERY ) );
 
-    TEST_EQUAL( 0, mbedtls_mpi_mod_residue_setup( &r, &m, R , r_limbs ) );
+    TEST_EQUAL( ret, mbedtls_mpi_mod_residue_setup( &r, &m, R , r_limbs ) );
-
-    /* Test for r-> limbs > m-> limbs */
-    TEST_EQUAL( MBEDTLS_ERR_MPI_BAD_INPUT_DATA, mbedtls_mpi_mod_residue_setup( &r, &m, R , r_limbs + 1 ) );
-
-    /* Test for r-> p > m-> p */
-    TEST_EQUAL( MBEDTLS_ERR_MPI_BAD_INPUT_DATA, mbedtls_mpi_mod_residue_setup( &r, &m, R_MAX , r_max_limbs ) );
-
-    /* Test for r-> p == m-> p */
-    TEST_EQUAL( MBEDTLS_ERR_MPI_BAD_INPUT_DATA, mbedtls_mpi_mod_residue_setup( &r, &m, N , r_max_limbs ) );
 
 exit:
     mbedtls_mpi_mod_modulus_free( &m );
     mbedtls_free( N );
     mbedtls_free( R );
-    mbedtls_free( R_MAX );
-
-    #undef RS_ONE
-    #undef RS_MAX_MIN1
-    #undef RS_MAX
 }
 /* END_CASE */
+
 /* BEGIN_CASE */
 void mpi_mod_io_neg( )
 {