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-rw-r--r--demos/pkey/EVP_PKEY_EC_keygen.c155
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diff --git a/demos/pkey/EVP_PKEY_EC_keygen.c b/demos/pkey/EVP_PKEY_EC_keygen.c
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+++ b/demos/pkey/EVP_PKEY_EC_keygen.c
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+/*-
+ * 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;
+}