1#!/usr/bin/env python3
2"""
3Purpose
4
5This script dumps comb table of ec curve. When you add a new ec curve, you
6can use this script to generate codes to define `<curve>_T` in ecp_curves.c
7"""
8
9# Copyright The Mbed TLS Contributors
10# SPDX-License-Identifier: Apache-2.0
11#
12# Licensed under the Apache License, Version 2.0 (the "License"); you may
13# not use this file except in compliance with the License.
14# You may obtain a copy of the License at
15#
16# http://www.apache.org/licenses/LICENSE-2.0
17#
18# Unless required by applicable law or agreed to in writing, software
19# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
20# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
21# See the License for the specific language governing permissions and
22# limitations under the License.
23
24import os
25import subprocess
26import sys
27import tempfile
28
29HOW_TO_ADD_NEW_CURVE = """
30If you are trying to add new curve, you can follow these steps:
31
321. Define curve parameters (<curve>_p, <curve>_gx, etc...) in ecp_curves.c.
332. Add a macro to define <curve>_T to NULL following these parameters.
343. Build mbedcrypto
354. Run this script with an argument of new curve
365. Copy the output of this script into ecp_curves.c and replace the macro added
37   in Step 2
386. Rebuild and test if everything is ok
39
40Replace the <curve> in the above with the name of the curve you want to add."""
41
42CC = os.getenv('CC', 'cc')
43MBEDTLS_LIBRARY_PATH = os.getenv('MBEDTLS_LIBRARY_PATH', "library")
44
45SRC_DUMP_COMB_TABLE = r'''
46#include <stdio.h>
47#include <stdlib.h>
48#include "mbedtls/ecp.h"
49#include "mbedtls/error.h"
50
51static void dump_mpi_initialize( const char *name, const mbedtls_mpi *d )
52{
53    uint8_t buf[128] = {0};
54    size_t olen;
55    uint8_t *p;
56
57    olen = mbedtls_mpi_size( d );
58    mbedtls_mpi_write_binary_le( d, buf, olen );
59    printf("static const mbedtls_mpi_uint %s[] = {\n", name);
60    for (p = buf; p < buf + olen; p += 8) {
61        printf( "    BYTES_TO_T_UINT_8( 0x%02X, 0x%02X, 0x%02X, 0x%02X, 0x%02X, 0x%02X, 0x%02X, 0x%02X ),\n",
62                p[0], p[1], p[2], p[3], p[4], p[5], p[6], p[7] );
63    }
64    printf("};\n");
65}
66
67static void dump_T( const mbedtls_ecp_group *grp )
68{
69    char name[128];
70
71    printf( "#if MBEDTLS_ECP_FIXED_POINT_OPTIM == 1\n" );
72
73    for (size_t i = 0; i < grp->T_size; ++i) {
74        snprintf( name, sizeof(name), "%s_T_%zu_X", CURVE_NAME, i );
75        dump_mpi_initialize( name, &grp->T[i].X );
76
77        snprintf( name, sizeof(name), "%s_T_%zu_Y", CURVE_NAME, i );
78        dump_mpi_initialize( name, &grp->T[i].Y );
79    }
80    printf( "static const mbedtls_ecp_point %s_T[%zu] = {\n", CURVE_NAME, grp->T_size );
81    size_t olen;
82    for (size_t i = 0; i < grp->T_size; ++i) {
83        int z;
84        if ( mbedtls_mpi_cmp_int(&grp->T[i].Z, 0) == 0 ) {
85            z = 0;
86        } else if ( mbedtls_mpi_cmp_int(&grp->T[i].Z, 1) == 0 ) {
87            z = 1;
88        } else {
89            fprintf( stderr, "Unexpected value of Z (i = %d)\n", (int)i );
90            exit( 1 );
91        }
92        printf( "    ECP_POINT_INIT_XY_Z%d(%s_T_%zu_X, %s_T_%zu_Y),\n",
93                z,
94                CURVE_NAME, i,
95                CURVE_NAME, i
96        );
97    }
98    printf("};\n#endif\n\n");
99}
100
101int main()
102{
103    int rc;
104    mbedtls_mpi m;
105    mbedtls_ecp_point R;
106    mbedtls_ecp_group grp;
107
108    mbedtls_ecp_group_init( &grp );
109    rc = mbedtls_ecp_group_load( &grp, CURVE_ID );
110    if (rc != 0) {
111        char buf[100];
112        mbedtls_strerror( rc, buf, sizeof(buf) );
113        fprintf( stderr, "mbedtls_ecp_group_load: %s (-0x%x)\n", buf, -rc );
114        return 1;
115    }
116    grp.T = NULL;
117    mbedtls_ecp_point_init( &R );
118    mbedtls_mpi_init( &m);
119    mbedtls_mpi_lset( &m, 1 );
120    rc = mbedtls_ecp_mul( &grp, &R, &m, &grp.G, NULL, NULL );
121    if ( rc != 0 ) {
122        char buf[100];
123        mbedtls_strerror( rc, buf, sizeof(buf) );
124        fprintf( stderr, "mbedtls_ecp_mul: %s (-0x%x)\n", buf, -rc );
125        return 1;
126    }
127    if ( grp.T == NULL ) {
128        fprintf( stderr, "grp.T is not generated. Please make sure"
129                         "MBEDTLS_ECP_FIXED_POINT_OPTIM is enabled in mbedtls_config.h\n" );
130        return 1;
131    }
132    dump_T( &grp );
133    return 0;
134}
135'''
136
137SRC_DUMP_KNOWN_CURVE = r'''
138#include <stdio.h>
139#include <stdlib.h>
140#include "mbedtls/ecp.h"
141
142int main() {
143    const mbedtls_ecp_curve_info *info = mbedtls_ecp_curve_list();
144    mbedtls_ecp_group grp;
145
146    mbedtls_ecp_group_init( &grp );
147    while ( info->name != NULL ) {
148        mbedtls_ecp_group_load( &grp, info->grp_id );
149        if ( mbedtls_ecp_get_type(&grp) == MBEDTLS_ECP_TYPE_SHORT_WEIERSTRASS ) {
150            printf( " %s", info->name );
151        }
152        info++;
153    }
154    printf( "\n" );
155    return 0;
156}
157'''
158
159
160def join_src_path(*args):
161    return os.path.normpath(os.path.join(os.path.dirname(__file__), "..", *args))
162
163
164def run_c_source(src, cflags):
165    """
166    Compile and run C source code
167    :param src: the c language code to run
168    :param cflags: additional cflags passing to compiler
169    :return:
170    """
171    binname = tempfile.mktemp(prefix="mbedtls")
172    fd, srcname = tempfile.mkstemp(prefix="mbedtls", suffix=".c")
173    srcfile = os.fdopen(fd, mode="w")
174    srcfile.write(src)
175    srcfile.close()
176    args = [CC,
177            *cflags,
178            '-I' + join_src_path("include"),
179            "-o", binname,
180            '-L' + MBEDTLS_LIBRARY_PATH,
181            srcname,
182            '-lmbedcrypto']
183
184    p = subprocess.run(args=args, check=False)
185    if p.returncode != 0:
186        return False
187    p = subprocess.run(args=[binname], check=False, env={
188        'LD_LIBRARY_PATH': MBEDTLS_LIBRARY_PATH
189    })
190    if p.returncode != 0:
191        return False
192    os.unlink(srcname)
193    os.unlink(binname)
194    return True
195
196
197def compute_curve(curve):
198    """compute comb table for curve"""
199    r = run_c_source(
200        SRC_DUMP_COMB_TABLE,
201        [
202            '-g',
203            '-DCURVE_ID=MBEDTLS_ECP_DP_%s' % curve.upper(),
204            '-DCURVE_NAME="%s"' % curve.lower(),
205        ])
206    if not r:
207        print("""\
208Unable to compile and run utility.""", file=sys.stderr)
209        sys.exit(1)
210
211
212def usage():
213    print("""
214Usage: python %s <curve>...
215
216Arguments:
217    curve       Specify one or more curve names (e.g secp256r1)
218
219All possible curves: """ % sys.argv[0])
220    run_c_source(SRC_DUMP_KNOWN_CURVE, [])
221    print("""
222Environment Variable:
223    CC          Specify which c compile to use to compile utility.
224    MBEDTLS_LIBRARY_PATH
225                Specify the path to mbedcrypto library. (e.g. build/library/)
226
227How to add a new curve: %s""" % HOW_TO_ADD_NEW_CURVE)
228
229
230def run_main():
231    shared_lib_path = os.path.normpath(os.path.join(MBEDTLS_LIBRARY_PATH, "libmbedcrypto.so"))
232    static_lib_path = os.path.normpath(os.path.join(MBEDTLS_LIBRARY_PATH, "libmbedcrypto.a"))
233    if not os.path.exists(shared_lib_path) and not os.path.exists(static_lib_path):
234        print("Warning: both '%s' and '%s' are not exists. This script will use "
235              "the library from your system instead of the library compiled by "
236              "this source directory.\n"
237              "You can specify library path using environment variable "
238              "'MBEDTLS_LIBRARY_PATH'." % (shared_lib_path, static_lib_path),
239              file=sys.stderr)
240
241    if len(sys.argv) <= 1:
242        usage()
243    else:
244        for curve in sys.argv[1:]:
245            compute_curve(curve)
246
247
248if __name__ == '__main__':
249    run_main()
250