Add demo for EC keygen
Fixes #14112 Reviewed-by: Paul Dale <pauli@openssl.org> (Merged from https://github.com/openssl/openssl/pull/15423)master
Shane Lontis
2 years ago
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dcc780cf8d
commit
8cf78d634b
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/*-
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* Copyright 2021 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the Apache License 2.0 (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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/*
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* Example showing how to generate an EC key and extract values from the
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* generated key.
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*/
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#include <string.h>
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#include <stdio.h>
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#include <openssl/err.h>
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#include <openssl/evp.h>
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#include <openssl/core_names.h>
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static int get_key_values(EVP_PKEY *pkey);
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/*
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* The following code shows how to generate an EC key from a curve name
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* with additional parameters. If only the curve name is required then the
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* simple helper can be used instead i.e. Either
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* pkey = EVP_EC_gen(curvename); OR
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* pkey = EVP_PKEY_Q_keygen(libctx, propq, "EC", curvename);
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*/
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static EVP_PKEY *do_ec_keygen(void)
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{
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/*
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* The libctx and propq can be set if required, they are included here
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* to show how they are passed to EVP_PKEY_CTX_new_from_name().
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*/
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OSSL_LIB_CTX *libctx = NULL;
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const char *propq = NULL;
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EVP_PKEY *key = NULL;
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OSSL_PARAM params[3];
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EVP_PKEY_CTX *genctx = NULL;
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const char *curvename = "P-256";
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int use_cofactordh = 1;
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genctx = EVP_PKEY_CTX_new_from_name(libctx, "EC", propq);
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if (genctx == NULL) {
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fprintf(stderr, "EVP_PKEY_CTX_new_from_name() failed\n");
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goto cleanup;
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}
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if (EVP_PKEY_keygen_init(genctx) <= 0) {
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fprintf(stderr, "EVP_PKEY_keygen_init() failed\n");
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goto cleanup;
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}
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params[0] = OSSL_PARAM_construct_utf8_string(OSSL_PKEY_PARAM_GROUP_NAME,
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(char *)curvename, 0);
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/*
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* This is an optional parameter.
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* For many curves where the cofactor is 1, setting this has no effect.
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*/
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params[1] = OSSL_PARAM_construct_int(OSSL_PKEY_PARAM_USE_COFACTOR_ECDH,
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&use_cofactordh);
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params[2] = OSSL_PARAM_construct_end();
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if (!EVP_PKEY_CTX_set_params(genctx, params)) {
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fprintf(stderr, "EVP_PKEY_CTX_set_params() failed\n");
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goto cleanup;
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}
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fprintf(stdout, "Generating EC key\n\n");
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if (EVP_PKEY_generate(genctx, &key) <= 0) {
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fprintf(stderr, "EVP_PKEY_generate() failed\n");
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goto cleanup;
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}
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cleanup:
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EVP_PKEY_CTX_free(genctx);
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return key;
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}
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/*
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* The following code shows how retrieve key data from the generated
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* EC key. See doc/man7/EVP_PKEY-EC.pod for more information.
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*
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* EVP_PKEY_print_private() could also be used to display the values.
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*/
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static int get_key_values(EVP_PKEY *pkey)
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{
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int result = 0;
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char out_curvename[80];
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unsigned char out_pubkey[80];
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unsigned char out_privkey[80];
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BIGNUM *out_priv = NULL;
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size_t i, out_pubkey_len, out_privkey_len = 0;
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if (!EVP_PKEY_get_utf8_string_param(pkey, OSSL_PKEY_PARAM_GROUP_NAME,
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out_curvename, sizeof(out_curvename),
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NULL)) {
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fprintf(stderr, "Failed to get curve name\n");
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goto cleanup;
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}
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if (!EVP_PKEY_get_octet_string_param(pkey, OSSL_PKEY_PARAM_PUB_KEY,
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out_pubkey, sizeof(out_pubkey),
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&out_pubkey_len)) {
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fprintf(stderr, "Failed to get public key\n");
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goto cleanup;
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}
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if (!EVP_PKEY_get_bn_param(pkey, OSSL_PKEY_PARAM_PRIV_KEY, &out_priv)) {
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fprintf(stderr, "Failed to get private key\n");
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goto cleanup;
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}
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out_privkey_len = BN_bn2bin(out_priv, out_privkey);
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if (out_privkey_len <= 0 || out_privkey_len > sizeof(out_privkey)) {
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fprintf(stderr, "BN_bn2bin failed\n");
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goto cleanup;
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}
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fprintf(stdout, "Curve name: %s\n", out_curvename);
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fprintf(stdout, "Public key:\n");
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BIO_dump_indent_fp(stdout, out_pubkey, out_pubkey_len, 2);
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fprintf(stdout, "Private Key:\n");
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BIO_dump_indent_fp(stdout, out_privkey, out_privkey_len, 2);
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result = 1;
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cleanup:
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/* Zeroize the private key data when we free it */
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BN_clear_free(out_priv);
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return result;
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}
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int main(void)
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{
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int result = 0;
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EVP_PKEY *pkey;
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pkey = do_ec_keygen();
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if (pkey == NULL)
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goto cleanup;
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if (!get_key_values(pkey))
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goto cleanup;
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/*
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* At this point we can write out the generated key using
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* i2d_PrivateKey() and i2d_PublicKey() if required.
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*/
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result = 1;
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cleanup:
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if (result != 1)
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ERR_print_errors_fp(stderr);
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EVP_PKEY_free(pkey);
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return result == 0;
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}
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@ -0,0 +1,20 @@
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#
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# To run the demos when linked with a shared library (default):
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#
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# LD_LIBRARY_PATH=../.. ./EVP_PKEY_EC_keygen
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CFLAGS = -I../../include -g
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LDFLAGS = -L../..
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LDLIBS = -lcrypto
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all: EVP_PKEY_EC_keygen
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%.o: %.c
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$(CC) $(CFLAGS) -c $<
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EVP_PKEY_EC_keygen: EVP_PKEY_EC_keygen.o
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test: ;
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clean:
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$(RM) *.o EVP_PKEY_EC_keygen
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