Move bignum helpers to their own module

Move bignum-related helper functions to their own files under tests/include
and tests/src. The primary motivation is that a subsequent commit will make
bignum_helpers.h include library/bignum*.h, but we want to be able to
include <test/helpers.h> without having the library directory on the include
path (we do this in some programs under programs/ intended for testing).

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

2 files changed, 122 insertions, 84 deletions

diff --git a/tests/src/bignum_helpers.c b/tests/src/bignum_helpers.c
new file mode 100644
index 0000000..575bd03
--- /dev/null
+++ b/tests/src/bignum_helpers.c
@@ -0,0 +1,119 @@
+/**
+ * \file bignum_helpers.c
+ *
+ * \brief   This file contains the prototypes of helper functions for
+ *          bignum-related testing.
+ */
+
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+#define MBEDTLS_ALLOW_PRIVATE_ACCESS
+#include <test/bignum_helpers.h>
+
+#if defined(MBEDTLS_BIGNUM_C)
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <mbedtls/bignum.h>
+#include <bignum_core.h>
+#include <bignum_mod.h>
+#include <bignum_mod_raw.h>
+
+#include <test/helpers.h>
+#include <test/macros.h>
+
+int mbedtls_test_read_mpi_core( mbedtls_mpi_uint **pX, size_t *plimbs,
+                                const char *input )
+{
+    /* Sanity check */
+    if( *pX != NULL )
+        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
+
+    size_t hex_len = strlen( input );
+    size_t byte_len = ( hex_len + 1 ) / 2;
+    *plimbs = CHARS_TO_LIMBS( byte_len );
+
+    /* A core bignum is not allowed to be empty. Forbid it as test data,
+     * this way static analyzers have a chance of knowing we don't expect
+     * the bignum functions to support empty inputs. */
+    if( *plimbs == 0 )
+        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
+
+    *pX = mbedtls_calloc( *plimbs, sizeof( **pX ) );
+    if( *pX == NULL )
+        return( MBEDTLS_ERR_MPI_ALLOC_FAILED );
+
+    unsigned char *byte_start = ( unsigned char * ) *pX;
+    if( byte_len % sizeof( mbedtls_mpi_uint ) != 0 )
+    {
+        byte_start += sizeof( mbedtls_mpi_uint ) - byte_len % sizeof( mbedtls_mpi_uint );
+    }
+    if( ( hex_len & 1 ) != 0 )
+    {
+        /* mbedtls_test_unhexify wants an even number of hex digits */
+        TEST_ASSERT( mbedtls_test_ascii2uc( *input, byte_start ) == 0 );
+        ++byte_start;
+        ++input;
+        --byte_len;
+    }
+    TEST_ASSERT( mbedtls_test_unhexify( byte_start,
+                                        byte_len,
+                                        input,
+                                        &byte_len ) == 0 );
+
+    mbedtls_mpi_core_bigendian_to_host( *pX, *plimbs );
+    return( 0 );
+
+exit:
+    mbedtls_free( *pX );
+    return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
+}
+
+int mbedtls_test_read_mpi( mbedtls_mpi *X, const char *s )
+{
+    int negative = 0;
+    /* Always set the sign bit to -1 if the input has a minus sign, even for 0.
+     * This creates an invalid representation, which mbedtls_mpi_read_string()
+     * avoids but we want to be able to create that in test data. */
+    if( s[0] == '-' )
+    {
+        ++s;
+        negative = 1;
+    }
+    /* mbedtls_mpi_read_string() currently retains leading zeros.
+     * It always allocates at least one limb for the value 0. */
+    if( s[0] == 0 )
+    {
+        mbedtls_mpi_free( X );
+        return( 0 );
+    }
+    int ret = mbedtls_mpi_read_string( X, 16, s );
+    if( ret != 0 )
+        return( ret );
+    if( negative )
+    {
+        if( mbedtls_mpi_cmp_int( X, 0 ) == 0 )
+            ++mbedtls_test_case_uses_negative_0;
+        X->s = -1;
+    }
+    return( 0 );
+}
+
+#endif /* MBEDTLS_BIGNUM_C */
+
diff --git a/tests/src/helpers.c b/tests/src/helpers.c
index 7c83714..be5c465 100644
--- a/tests/src/helpers.c
+++ b/tests/src/helpers.c
@@ -48,7 +48,7 @@ void mbedtls_test_platform_teardown( void )
 #endif /* MBEDTLS_PLATFORM_C */
 }
 
-static int ascii2uc(const char c, unsigned char *uc)
+int mbedtls_test_ascii2uc(const char c, unsigned char *uc)
 {
     if( ( c >= '0' ) && ( c <= '9' ) )
         *uc = c - '0';
@@ -207,10 +207,10 @@ int mbedtls_test_unhexify( unsigned char *obuf,
 
     while( *ibuf != 0 )
     {
-        if ( ascii2uc( *(ibuf++), &uc ) != 0 )
+        if ( mbedtls_test_ascii2uc( *(ibuf++), &uc ) != 0 )
             return( -1 );
 
-        if ( ascii2uc( *(ibuf++), &uc2 ) != 0 )
+        if ( mbedtls_test_ascii2uc( *(ibuf++), &uc2 ) != 0 )
             return( -1 );
 
         *(obuf++) = ( uc << 4 ) | uc2;
@@ -350,84 +350,3 @@ void mbedtls_test_err_add_check( int high, int low,
     }
 }
 #endif /* MBEDTLS_TEST_HOOKS */
-
-#if defined(MBEDTLS_BIGNUM_C)
-#include "bignum_core.h"
-
-int mbedtls_test_read_mpi_core( mbedtls_mpi_uint **pX, size_t *plimbs,
-                                const char *input )
-{
-    /* Sanity check */
-    if( *pX != NULL )
-        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
-
-    size_t hex_len = strlen( input );
-    size_t byte_len = ( hex_len + 1 ) / 2;
-    *plimbs = CHARS_TO_LIMBS( byte_len );
-
-    /* A core bignum is not allowed to be empty. Forbid it as test data,
-     * this way static analyzers have a chance of knowing we don't expect
-     * the bignum functions to support empty inputs. */
-    if( *plimbs == 0 )
-        return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
-
-    *pX = mbedtls_calloc( *plimbs, sizeof( **pX ) );
-    if( *pX == NULL )
-        return( MBEDTLS_ERR_MPI_ALLOC_FAILED );
-
-    unsigned char *byte_start = ( unsigned char * ) *pX;
-    if( byte_len % sizeof( mbedtls_mpi_uint ) != 0 )
-    {
-        byte_start += sizeof( mbedtls_mpi_uint ) - byte_len % sizeof( mbedtls_mpi_uint );
-    }
-    if( ( hex_len & 1 ) != 0 )
-    {
-        /* mbedtls_test_unhexify wants an even number of hex digits */
-        TEST_ASSERT( ascii2uc( *input, byte_start ) == 0 );
-        ++byte_start;
-        ++input;
-        --byte_len;
-    }
-    TEST_ASSERT( mbedtls_test_unhexify( byte_start,
-                                        byte_len,
-                                        input,
-                                        &byte_len ) == 0 );
-
-    mbedtls_mpi_core_bigendian_to_host( *pX, *plimbs );
-    return( 0 );
-
-exit:
-    mbedtls_free( *pX );
-    return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
-}
-
-int mbedtls_test_read_mpi( mbedtls_mpi *X, const char *s )
-{
-    int negative = 0;
-    /* Always set the sign bit to -1 if the input has a minus sign, even for 0.
-     * This creates an invalid representation, which mbedtls_mpi_read_string()
-     * avoids but we want to be able to create that in test data. */
-    if( s[0] == '-' )
-    {
-        ++s;
-        negative = 1;
-    }
-    /* mbedtls_mpi_read_string() currently retains leading zeros.
-     * It always allocates at least one limb for the value 0. */
-    if( s[0] == 0 )
-    {
-        mbedtls_mpi_free( X );
-        return( 0 );
-    }
-    int ret = mbedtls_mpi_read_string( X, 16, s );
-    if( ret != 0 )
-        return( ret );
-    if( negative )
-    {
-        if( mbedtls_mpi_cmp_int( X, 0 ) == 0 )
-            ++mbedtls_test_case_uses_negative_0;
-        X->s = -1;
-    }
-    return( 0 );
-}
-#endif