1=pod 2 3=head1 NAME 4 5EVP_PKEY_gettable_params, EVP_PKEY_get_params, 6EVP_PKEY_get_int_param, EVP_PKEY_get_size_t_param, 7EVP_PKEY_get_bn_param, EVP_PKEY_get_utf8_string_param, 8EVP_PKEY_get_octet_string_param 9- retrieve key parameters from a key 10 11=head1 SYNOPSIS 12 13 #include <openssl/evp.h> 14 15 const OSSL_PARAM *EVP_PKEY_gettable_params(EVP_PKEY *pkey); 16 int EVP_PKEY_get_params(const EVP_PKEY *pkey, OSSL_PARAM params[]); 17 int EVP_PKEY_get_int_param(const EVP_PKEY *pkey, const char *key_name, 18 int *out); 19 int EVP_PKEY_get_size_t_param(const EVP_PKEY *pkey, const char *key_name, 20 size_t *out); 21 int EVP_PKEY_get_bn_param(const EVP_PKEY *pkey, const char *key_name, 22 BIGNUM **bn); 23 int EVP_PKEY_get_utf8_string_param(const EVP_PKEY *pkey, const char *key_name, 24 char *str, size_t max_buf_sz, 25 size_t *out_len); 26 int EVP_PKEY_get_octet_string_param(const EVP_PKEY *pkey, const char *key_name, 27 unsigned char *buf, size_t max_buf_sz, 28 size_t *out_len); 29 30=head1 DESCRIPTION 31 32See L<OSSL_PARAM(3)> for information about parameters. 33 34EVP_PKEY_get_params() retrieves parameters from the key I<pkey>, according to 35the contents of I<params>. 36 37EVP_PKEY_gettable_params() returns a constant list of I<params> indicating 38the names and types of key parameters that can be retrieved. 39 40An L<OSSL_PARAM(3)> of type B<OSSL_PARAM_INTEGER> or 41B<OSSL_PARAM_UNSIGNED_INTEGER> is of arbitrary length. Such a parameter can be 42obtained using any of the functions EVP_PKEY_get_int_param(), 43EVP_PKEY_get_size_t_param() or EVP_PKEY_get_bn_param(). Attempting to 44obtain an integer value that does not fit into a native C B<int> type will cause 45EVP_PKEY_get_int_param() to fail. Similarly attempting to obtain an integer 46value that is negative or does not fit into a native C B<size_t> type using 47EVP_PKEY_get_size_t_param() will also fail. 48 49EVP_PKEY_get_int_param() retrieves a key I<pkey> integer value I<*out> 50associated with a name of I<key_name> if it fits into C<int> type. For 51parameters that do not fit into C<int> use EVP_PKEY_get_bn_param(). 52 53EVP_PKEY_get_size_t_param() retrieves a key I<pkey> size_t value I<*out> 54associated with a name of I<key_name> if it fits into C<size_t> type. For 55parameters that do not fit into C<size_t> use EVP_PKEY_get_bn_param(). 56 57EVP_PKEY_get_bn_param() retrieves a key I<pkey> BIGNUM value I<**bn> 58associated with a name of I<key_name>. If I<*bn> is NULL then the BIGNUM 59is allocated by the method. 60 61EVP_PKEY_get_utf8_string_param() get a key I<pkey> UTF8 string value into a 62buffer I<str> of maximum size I<max_buf_sz> associated with a name of 63I<key_name>. The maximum size must be large enough to accommodate the string 64value including a terminating NUL byte, or this function will fail. 65If I<out_len> is not NULL, I<*out_len> is set to the length of the string 66not including the terminating NUL byte. The required buffer size not including 67the terminating NUL byte can be obtained from I<*out_len> by calling the 68function with I<str> set to NULL. 69 70EVP_PKEY_get_octet_string_param() get a key I<pkey>'s octet string value into a 71buffer I<buf> of maximum size I<max_buf_sz> associated with a name of I<key_name>. 72If I<out_len> is not NULL, I<*out_len> is set to the length of the contents. 73The required buffer size can be obtained from I<*out_len> by calling the 74function with I<buf> set to NULL. 75 76=head1 NOTES 77 78These functions only work for B<EVP_PKEY>s that contain a provider side key. 79 80=head1 RETURN VALUES 81 82EVP_PKEY_gettable_params() returns NULL on error or if it is not supported. 83 84All other methods return 1 if a value associated with the key's I<key_name> was 85successfully returned, or 0 if there was an error. 86An error may be returned by methods EVP_PKEY_get_utf8_string_param() and 87EVP_PKEY_get_octet_string_param() if I<max_buf_sz> is not big enough to hold the 88value. If I<out_len> is not NULL, I<*out_len> will be assigned the required 89buffer size to hold the value. 90 91=head1 EXAMPLES 92 93 #include <openssl/evp.h> 94 95 char curve_name[64]; 96 unsigned char pub[256]; 97 BIGNUM *bn_priv = NULL; 98 99 /* 100 * NB: assumes 'key' is set up before the next step. In this example the key 101 * is an EC key. 102 */ 103 104 if (!EVP_PKEY_get_utf8_string_param(key, OSSL_PKEY_PARAM_GROUP_NAME, 105 curve_name, sizeof(curve_name), &len)) { 106 /* Error */ 107 } 108 if (!EVP_PKEY_get_octet_string_param(key, OSSL_PKEY_PARAM_PUB_KEY, 109 pub, sizeof(pub), &len)) { 110 /* Error */ 111 } 112 if (!EVP_PKEY_get_bn_param(key, OSSL_PKEY_PARAM_PRIV_KEY, &bn_priv)) { 113 /* Error */ 114 } 115 116 BN_clear_free(bn_priv); 117 118=head1 SEE ALSO 119 120L<EVP_PKEY_CTX_new(3)>, L<provider-keymgmt(7)>, L<OSSL_PARAM(3)> 121 122=head1 HISTORY 123 124These functions were added in OpenSSL 3.0. 125 126=head1 COPYRIGHT 127 128Copyright 2020-2023 The OpenSSL Project Authors. All Rights Reserved. 129 130Licensed under the Apache License 2.0 (the "License"). You may not use 131this file except in compliance with the License. You can obtain a copy 132in the file LICENSE in the source distribution or at 133L<https://www.openssl.org/source/license.html>. 134 135=cut 136 137