| /*- |
| * Copyright 2021-2022 The OpenSSL Project Authors. All Rights Reserved. |
| * |
| * Licensed under the Apache License 2.0 (the "License"). You may not use |
| * this file except in compliance with the License. You can obtain a copy |
| * in the file LICENSE in the source distribution or at |
| * https://www.openssl.org/source/license.html |
| */ |
| |
| /* |
| * Example showing how to generate an EC key and extract values from the |
| * generated key. |
| */ |
| |
| #include <string.h> |
| #include <stdio.h> |
| #include <openssl/err.h> |
| #include <openssl/evp.h> |
| #include <openssl/core_names.h> |
| |
| static int get_key_values(EVP_PKEY *pkey); |
| |
| /* |
| * The following code shows how to generate an EC key from a curve name |
| * with additional parameters. If only the curve name is required then the |
| * simple helper can be used instead i.e. Either |
| * pkey = EVP_EC_gen(curvename); OR |
| * pkey = EVP_PKEY_Q_keygen(libctx, propq, "EC", curvename); |
| */ |
| static EVP_PKEY *do_ec_keygen(void) |
| { |
| /* |
| * The libctx and propq can be set if required, they are included here |
| * to show how they are passed to EVP_PKEY_CTX_new_from_name(). |
| */ |
| OSSL_LIB_CTX *libctx = NULL; |
| const char *propq = NULL; |
| EVP_PKEY *key = NULL; |
| OSSL_PARAM params[3]; |
| EVP_PKEY_CTX *genctx = NULL; |
| const char *curvename = "P-256"; |
| int use_cofactordh = 1; |
| |
| genctx = EVP_PKEY_CTX_new_from_name(libctx, "EC", propq); |
| if (genctx == NULL) { |
| fprintf(stderr, "EVP_PKEY_CTX_new_from_name() failed\n"); |
| goto cleanup; |
| } |
| |
| if (EVP_PKEY_keygen_init(genctx) <= 0) { |
| fprintf(stderr, "EVP_PKEY_keygen_init() failed\n"); |
| goto cleanup; |
| } |
| |
| params[0] = OSSL_PARAM_construct_utf8_string(OSSL_PKEY_PARAM_GROUP_NAME, |
| (char *)curvename, 0); |
| /* |
| * This is an optional parameter. |
| * For many curves where the cofactor is 1, setting this has no effect. |
| */ |
| params[1] = OSSL_PARAM_construct_int(OSSL_PKEY_PARAM_USE_COFACTOR_ECDH, |
| &use_cofactordh); |
| params[2] = OSSL_PARAM_construct_end(); |
| if (!EVP_PKEY_CTX_set_params(genctx, params)) { |
| fprintf(stderr, "EVP_PKEY_CTX_set_params() failed\n"); |
| goto cleanup; |
| } |
| |
| fprintf(stdout, "Generating EC key\n\n"); |
| if (EVP_PKEY_generate(genctx, &key) <= 0) { |
| fprintf(stderr, "EVP_PKEY_generate() failed\n"); |
| goto cleanup; |
| } |
| cleanup: |
| EVP_PKEY_CTX_free(genctx); |
| return key; |
| } |
| |
| /* |
| * The following code shows how retrieve key data from the generated |
| * EC key. See doc/man7/EVP_PKEY-EC.pod for more information. |
| * |
| * EVP_PKEY_print_private() could also be used to display the values. |
| */ |
| static int get_key_values(EVP_PKEY *pkey) |
| { |
| int result = 0; |
| char out_curvename[80]; |
| unsigned char out_pubkey[80]; |
| unsigned char out_privkey[80]; |
| BIGNUM *out_priv = NULL; |
| size_t out_pubkey_len, out_privkey_len = 0; |
| |
| if (!EVP_PKEY_get_utf8_string_param(pkey, OSSL_PKEY_PARAM_GROUP_NAME, |
| out_curvename, sizeof(out_curvename), |
| NULL)) { |
| fprintf(stderr, "Failed to get curve name\n"); |
| goto cleanup; |
| } |
| |
| if (!EVP_PKEY_get_octet_string_param(pkey, OSSL_PKEY_PARAM_PUB_KEY, |
| out_pubkey, sizeof(out_pubkey), |
| &out_pubkey_len)) { |
| fprintf(stderr, "Failed to get public key\n"); |
| goto cleanup; |
| } |
| |
| if (!EVP_PKEY_get_bn_param(pkey, OSSL_PKEY_PARAM_PRIV_KEY, &out_priv)) { |
| fprintf(stderr, "Failed to get private key\n"); |
| goto cleanup; |
| } |
| |
| out_privkey_len = BN_bn2bin(out_priv, out_privkey); |
| if (out_privkey_len <= 0 || out_privkey_len > sizeof(out_privkey)) { |
| fprintf(stderr, "BN_bn2bin failed\n"); |
| goto cleanup; |
| } |
| |
| fprintf(stdout, "Curve name: %s\n", out_curvename); |
| fprintf(stdout, "Public key:\n"); |
| BIO_dump_indent_fp(stdout, out_pubkey, out_pubkey_len, 2); |
| fprintf(stdout, "Private Key:\n"); |
| BIO_dump_indent_fp(stdout, out_privkey, out_privkey_len, 2); |
| |
| result = 1; |
| cleanup: |
| /* Zeroize the private key data when we free it */ |
| BN_clear_free(out_priv); |
| return result; |
| } |
| |
| int main(void) |
| { |
| int result = 0; |
| EVP_PKEY *pkey; |
| |
| pkey = do_ec_keygen(); |
| if (pkey == NULL) |
| goto cleanup; |
| |
| if (!get_key_values(pkey)) |
| goto cleanup; |
| |
| /* |
| * At this point we can write out the generated key using |
| * i2d_PrivateKey() and i2d_PublicKey() if required. |
| */ |
| result = 1; |
| cleanup: |
| if (result != 1) |
| ERR_print_errors_fp(stderr); |
| |
| EVP_PKEY_free(pkey); |
| return result == 0; |
| } |