diff options
Diffstat (limited to 'demos/pkey/EVP_PKEY_EC_keygen.c')
| -rw-r--r-- | demos/pkey/EVP_PKEY_EC_keygen.c | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/demos/pkey/EVP_PKEY_EC_keygen.c b/demos/pkey/EVP_PKEY_EC_keygen.c new file mode 100644 index 0000000000..14efaea53a --- /dev/null +++ b/demos/pkey/EVP_PKEY_EC_keygen.c @@ -0,0 +1,155 @@ +/*- + * Copyright 2021 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 i, 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; +} |