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#!/usr/bin/env python3
"""
Purpose
This script dumps comb table of ec curve. When you add a new ec curve, you
can use this script to generate codes to define `<curve>_T` in ecp_curves.c
"""
# Copyright The Mbed TLS Contributors
# SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
import os
import subprocess
import sys
import tempfile
HOW_TO_ADD_NEW_CURVE = """
If you are trying to add new curve, you can follow these steps:
1. Define curve parameters (<curve>_p, <curve>_gx, etc...) in ecp_curves.c.
2. Add a macro to define <curve>_T to NULL following these parameters.
3. Build mbedcrypto
4. Run this script with an argument of new curve
5. Copy the output of this script into ecp_curves.c and replace the macro added
in Step 2
6. Rebuild and test if everything is ok
Replace the <curve> in the above with the name of the curve you want to add."""
CC = os.getenv('CC', 'cc')
MBEDTLS_LIBRARY_PATH = os.getenv('MBEDTLS_LIBRARY_PATH', "library")
SRC_DUMP_COMB_TABLE = r'''
#include <stdio.h>
#include <stdlib.h>
#include "mbedtls/ecp.h"
#include "mbedtls/error.h"
static void dump_mpi_initialize( const char *name, const mbedtls_mpi *d )
{
uint8_t buf[128] = {0};
size_t olen;
uint8_t *p;
olen = mbedtls_mpi_size( d );
mbedtls_mpi_write_binary_le( d, buf, olen );
printf("static const mbedtls_mpi_uint %s[] = {\n", name);
for (p = buf; p < buf + olen; p += 8) {
printf( " BYTES_TO_T_UINT_8( 0x%02X, 0x%02X, 0x%02X, 0x%02X, 0x%02X, 0x%02X, 0x%02X, 0x%02X ),\n",
p[0], p[1], p[2], p[3], p[4], p[5], p[6], p[7] );
}
printf("};\n");
}
static void dump_T( const mbedtls_ecp_group *grp )
{
char name[128];
printf( "#if MBEDTLS_ECP_FIXED_POINT_OPTIM == 1\n" );
for (size_t i = 0; i < grp->T_size; ++i) {
snprintf( name, sizeof(name), "%s_T_%zu_X", CURVE_NAME, i );
dump_mpi_initialize( name, &grp->T[i].X );
snprintf( name, sizeof(name), "%s_T_%zu_Y", CURVE_NAME, i );
dump_mpi_initialize( name, &grp->T[i].Y );
}
printf( "static const mbedtls_ecp_point %s_T[%zu] = {\n", CURVE_NAME, grp->T_size );
size_t olen;
for (size_t i = 0; i < grp->T_size; ++i) {
int z;
if ( mbedtls_mpi_cmp_int(&grp->T[i].Z, 0) == 0 ) {
z = 0;
} else if ( mbedtls_mpi_cmp_int(&grp->T[i].Z, 1) == 0 ) {
z = 1;
} else {
fprintf( stderr, "Unexpected value of Z (i = %d)\n", (int)i );
exit( 1 );
}
printf( " ECP_POINT_INIT_XY_Z%d(%s_T_%zu_X, %s_T_%zu_Y),\n",
z,
CURVE_NAME, i,
CURVE_NAME, i
);
}
printf("};\n#endif\n\n");
}
int main()
{
int rc;
mbedtls_mpi m;
mbedtls_ecp_point R;
mbedtls_ecp_group grp;
mbedtls_ecp_group_init( &grp );
rc = mbedtls_ecp_group_load( &grp, CURVE_ID );
if (rc != 0) {
char buf[100];
mbedtls_strerror( rc, buf, sizeof(buf) );
fprintf( stderr, "mbedtls_ecp_group_load: %s (-0x%x)\n", buf, -rc );
return 1;
}
grp.T = NULL;
mbedtls_ecp_point_init( &R );
mbedtls_mpi_init( &m);
mbedtls_mpi_lset( &m, 1 );
rc = mbedtls_ecp_mul( &grp, &R, &m, &grp.G, NULL, NULL );
if ( rc != 0 ) {
char buf[100];
mbedtls_strerror( rc, buf, sizeof(buf) );
fprintf( stderr, "mbedtls_ecp_mul: %s (-0x%x)\n", buf, -rc );
return 1;
}
if ( grp.T == NULL ) {
fprintf( stderr, "grp.T is not generated. Please make sure"
"MBEDTLS_ECP_FIXED_POINT_OPTIM is enabled in mbedtls_config.h\n" );
return 1;
}
dump_T( &grp );
return 0;
}
'''
SRC_DUMP_KNOWN_CURVE = r'''
#include <stdio.h>
#include <stdlib.h>
#include "mbedtls/ecp.h"
int main() {
const mbedtls_ecp_curve_info *info = mbedtls_ecp_curve_list();
mbedtls_ecp_group grp;
mbedtls_ecp_group_init( &grp );
while ( info->name != NULL ) {
mbedtls_ecp_group_load( &grp, info->grp_id );
if ( mbedtls_ecp_get_type(&grp) == MBEDTLS_ECP_TYPE_SHORT_WEIERSTRASS ) {
printf( " %s", info->name );
}
info++;
}
printf( "\n" );
return 0;
}
'''
def join_src_path(*args):
return os.path.normpath(os.path.join(os.path.dirname(__file__), "..", *args))
def run_c_source(src, cflags):
"""
Compile and run C source code
:param src: the c language code to run
:param cflags: additional cflags passing to compiler
:return:
"""
binname = tempfile.mktemp(prefix="mbedtls")
fd, srcname = tempfile.mkstemp(prefix="mbedtls", suffix=".c")
srcfile = os.fdopen(fd, mode="w")
srcfile.write(src)
srcfile.close()
args = [CC,
*cflags,
'-I' + join_src_path("include"),
"-o", binname,
'-L' + MBEDTLS_LIBRARY_PATH,
srcname,
'-lmbedcrypto']
p = subprocess.run(args=args, check=False)
if p.returncode != 0:
return False
p = subprocess.run(args=[binname], check=False, env={
'LD_LIBRARY_PATH': MBEDTLS_LIBRARY_PATH
})
if p.returncode != 0:
return False
os.unlink(srcname)
os.unlink(binname)
return True
def compute_curve(curve):
"""compute comb table for curve"""
r = run_c_source(
SRC_DUMP_COMB_TABLE,
[
'-g',
'-DCURVE_ID=MBEDTLS_ECP_DP_%s' % curve.upper(),
'-DCURVE_NAME="%s"' % curve.lower(),
])
if not r:
print("""\
Unable to compile and run utility.""", file=sys.stderr)
sys.exit(1)
def usage():
print("""
Usage: python %s <curve>...
Arguments:
curve Specify one or more curve names (e.g secp256r1)
All possible curves: """ % sys.argv[0])
run_c_source(SRC_DUMP_KNOWN_CURVE, [])
print("""
Environment Variable:
CC Specify which c compile to use to compile utility.
MBEDTLS_LIBRARY_PATH
Specify the path to mbedcrypto library. (e.g. build/library/)
How to add a new curve: %s""" % HOW_TO_ADD_NEW_CURVE)
def run_main():
shared_lib_path = os.path.normpath(os.path.join(MBEDTLS_LIBRARY_PATH, "libmbedcrypto.so"))
static_lib_path = os.path.normpath(os.path.join(MBEDTLS_LIBRARY_PATH, "libmbedcrypto.a"))
if not os.path.exists(shared_lib_path) and not os.path.exists(static_lib_path):
print("Warning: both '%s' and '%s' are not exists. This script will use "
"the library from your system instead of the library compiled by "
"this source directory.\n"
"You can specify library path using environment variable "
"'MBEDTLS_LIBRARY_PATH'." % (shared_lib_path, static_lib_path),
file=sys.stderr)
if len(sys.argv) <= 1:
usage()
else:
for curve in sys.argv[1:]:
compute_curve(curve)
if __name__ == '__main__':
run_main()
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