openssl/doc/man3/EVP_PKEY_fromdata.pod

=pod

=head1 NAME

EVP_PKEY_param_fromdata_init, EVP_PKEY_key_fromdata_init, EVP_PKEY_fromdata,
EVP_PKEY_param_fromdata_settable, EVP_PKEY_key_fromdata_settable
- functions to create key parameters and keys from user data

=head1 SYNOPSIS

 #include <openssl/evp.h>

 int EVP_PKEY_param_fromdata_init(EVP_PKEY_CTX *ctx);
 int EVP_PKEY_key_fromdata_init(EVP_PKEY_CTX *ctx);
 int EVP_PKEY_fromdata(EVP_PKEY_CTX *ctx, EVP_PKEY **ppkey, OSSL_PARAM params[]);
 const OSSL_PARAM *EVP_PKEY_param_fromdata_settable(EVP_PKEY_CTX *ctx);
 const OSSL_PARAM *EVP_PKEY_key_fromdata_settable(EVP_PKEY_CTX *ctx);

=head1 DESCRIPTION

The functions described here are used to create new keys from user
provided key data, such as I<n>, I<e> and I<d> for a minimal RSA
keypair.

These functions use an B<EVP_PKEY_CTX> context, which should primarily
be created with L<EVP_PKEY_CTX_new_from_name(3)> or
L<EVP_PKEY_CTX_new_id(3)>.

The exact key data that the user can pass depends on the key type.
These are passed as an L<OSSL_PARAM(3)> array.

EVP_PKEY_param_fromdata_init() initializes a public key algorithm context
for creating key parameters from user data.

EVP_PKEY_key_fromdata_init() initializes a public key algorithm context for
creating a key from user data.

EVP_PKEY_fromdata() creates the structure to store key parameters or a
key, given data from I<params> and a context that's been initialized with
EVP_PKEY_param_fromdata_init() or EVP_PKEY_key_fromdata_init().  The result is
written to I<*ppkey>. The parameters that can be used for various types of key
are as described by the diverse "Common parameters" sections of the
L<B<EVP_PKEY-RSA>(7)|EVP_PKEY-RSA(7)/Common RSA parameters>,
L<B<EVP_PKEY-DSA>(7)|EVP_PKEY-DSA(7)/Common DSA & DH parameters>,
L<B<EVP_PKEY-DH>(7)|EVP_PKEY-DH(7)/Common DH parameters>,
L<B<EVP_PKEY-EC>(7)|EVP_PKEY-EC(7)/Common EC parameters>,
L<B<EVP_PKEY-ED448>(7)|EVP_PKEY-ED448(7)/Common X25519, X448, ED25519 and ED448 parameters>,
L<B<EVP_PKEY-X25519>(7)|EVP_PKEY-X25519(7)/Common X25519, X448, ED25519 and ED448 parameters>,
L<B<EVP_PKEY-X448>(7)|EVP_PKEY-X448(7)/Common X25519, X448, ED25519 and ED448 parameters>,
and L<B<EVP_PKEY-ED25519>(7)|EVP_PKEY-ED25519(7)/Common X25519, X448, ED25519 and ED448 parameters> pages.

=for comment the awful list of links above is made this way so we get nice
rendering as a man-page while still getting proper links in HTML

EVP_PKEY_param_fromdata_settable() and EVP_PKEY_key_fromdata_settable()
get a constant B<OSSL_PARAM> array that describes the settable parameters
that can be used with EVP_PKEY_fromdata().
See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as parameter descriptor.

=head1 NOTES

These functions only work with key management methods coming from a
provider.

=for comment We may choose to make this available for legacy methods too... 

=head1 RETURN VALUES

EVP_PKEY_key_fromdata_init(), EVP_PKEY_param_fromdata_init() and
EVP_PKEY_fromdata() return 1 for success and 0 or a negative value for
failure.  In particular a return value of -2 indicates the operation is
not supported by the public key algorithm.

=head1 EXAMPLES

These examples are very terse for the sake of staying on topic, which
is the EVP_PKEY_fromdata() set of functions.  In real applications,
BIGNUMs would be handled and converted to byte arrays with
BN_bn2nativepad(), but that's off topic here.

=begin comment

TODO Write a set of cookbook documents and link to them.

=end comment

=head2 Creating an RSA keypair using raw key data

 #include <openssl/evp.h>

 /*
  * These are extremely small to make this example simple.  A real
  * and secure application will not use such small numbers.  A real
  * and secure application is expected to use BIGNUMs, and to build
  * this array dynamically.
  */
 unsigned long rsa_n = 0xbc747fc5;
 unsigned long rsa_e = 0x10001;
 unsigned long rsa_d = 0x7b133399;
 OSSL_PARAM params[] = {
     OSSL_PARAM_ulong("n", &rsa_n),
     OSSL_PARAM_ulong("e", &rsa_e),
     OSSL_PARAM_ulong("d", &rsa_d),
     OSSL_PARAM_END
 };

 int main()
 {
     EVP_PKEY_CTX *ctx = EVP_PKEY_CTX_new_from_name(NULL, "RSA", NULL);
     EVP_PKEY *pkey = NULL;

     if (ctx == NULL
         || EVP_PKEY_key_fromdata_init(ctx) <= 0
         || EVP_PKEY_fromdata(ctx, &pkey, params) <= 0)
         exit(1);

     /* Do what you want with |pkey| */
 }

=head2 Creating an ECC keypair using raw key data

 #include <openssl/evp.h>
 #include <openssl/param_build.h>

 /*
  * Fixed data to represent the private and public key.
  */
 const unsigned char priv_data[] = {
     0xb9, 0x2f, 0x3c, 0xe6, 0x2f, 0xfb, 0x45, 0x68,
     0x39, 0x96, 0xf0, 0x2a, 0xaf, 0x6c, 0xda, 0xf2,
     0x89, 0x8a, 0x27, 0xbf, 0x39, 0x9b, 0x7e, 0x54,
     0x21, 0xc2, 0xa1, 0xe5, 0x36, 0x12, 0x48, 0x5d
 };
 /* UNCOMPRESSED FORMAT */
 const unsigned char pub_data[] = {
     POINT_CONVERSION_UNCOMPRESSED,
     0xcf, 0x20, 0xfb, 0x9a, 0x1d, 0x11, 0x6c, 0x5e,
     0x9f, 0xec, 0x38, 0x87, 0x6c, 0x1d, 0x2f, 0x58,
     0x47, 0xab, 0xa3, 0x9b, 0x79, 0x23, 0xe6, 0xeb,
     0x94, 0x6f, 0x97, 0xdb, 0xa3, 0x7d, 0xbd, 0xe5,
     0x26, 0xca, 0x07, 0x17, 0x8d, 0x26, 0x75, 0xff,
     0xcb, 0x8e, 0xb6, 0x84, 0xd0, 0x24, 0x02, 0x25,
     0x8f, 0xb9, 0x33, 0x6e, 0xcf, 0x12, 0x16, 0x2f,
     0x5c, 0xcd, 0x86, 0x71, 0xa8, 0xbf, 0x1a, 0x47
 };
 const OSSL_PARAM params[] = {
     OSSL_PARAM_utf8_string("group", "prime256v1"),
     OSSL_PARAM_BN("priv", priv, sizeof(priv)),
     OSSL_PARAM_BN("pub", pub, sizeof(pub)),
     OSSL_PARAM_END
 };

 int main()
 {
     EVP_PKEY_CTX *ctx;
     EVP_PKEY *pkey = NULL;
     BIGNUM *priv;
     OSSL_PARAM_BLD *param_bld;
     OSSL_PARAM *params = NULL;
     int exitcode = 0;

     priv = BN_bin2bn(priv_data, sizeof(priv_data), NULL);

     param_bld = OSSL_PARAM_BLD_new();
     if (priv != NULL && param_bld != NULL
         && OSSL_PARAM_BLD_push_utf8_string(param_bld, "group",
                                            "prime256v1", 0);
         && OSSL_PARAM_BLD_push_BN(param_bld, "priv", priv);
         && OSSL_PARAM_BLD_push_octet_string(param_bld, "pub",
                                             pub_data, sizeof(pub_data)))
         params = OSSL_PARAM_BLD_to_param(param_bld);

     ctx = EVP_PKEY_CTX_new_from_name(NULL, "EC", NULL);
     if (ctx == NULL
         || params != NULL
         || EVP_PKEY_key_fromdata_init(ctx) <= 0
         || EVP_PKEY_fromdata(ctx, &pkey, params) <= 0) {
         exitcode = 1;
     } else {
         /* Do what you want with |pkey| */
     }

     EVP_PKEY_free(pkey);
     EVP_PKEY_CTX_free(ctx);
     OSSL_PARAM_BLD_free_params(params);
     OSSL_PARAM_BLD_free(param_bld);
     BN_free(priv);

     exit(exitcode);
 }

=head2 Finding out params for an unknown key type

 #include <openssl/evp.h>

 /* Program expects a key type as first argument */
 int main(int argc, char *argv[])
 {
     EVP_PKEY_CTX *ctx = EVP_PKEY_CTX_new_from_name(NULL, argv[1], NULL);
     const *OSSL_PARAM *settable_params = NULL;

     if (ctx == NULL
         || (settable_params = EVP_PKEY_key_fromdata_settable(ctx)) == NULL)
         exit(1);

     for (; settable_params->key != NULL; settable_params++) {
         const char *datatype = NULL;

         switch (settable_params->data_type) {
         case OSSL_PARAM_INTEGER:
             datatype = "integer";
             break;
         case OSSL_PARAM_UNSIGNED_INTEGER:
             datatype = "unsigned integer";
             break;
         case OSSL_PARAM_UTF8_STRING:
             datatype = "printable string (utf-8 encoding expected)";
             break;
         case OSSL_PARAM_UTF8_PTR:
             datatype = "printable string pointer (utf-8 encoding expected)";
             break;
         case OSSL_PARAM_OCTET_STRING:
             datatype = "octet string";
             break;
         case OSSL_PARAM_OCTET_PTR:
             datatype = "octet string pointer";
             break;
         }
         printf("%s : %s ", settable_params->key, datatype);
         if (settable_params->data_size == 0)
             printf("(unlimited size)");
         else
             printf("(maximum size %zu)", settable_params->data_size);
     }
 }

The descriptor L<OSSL_PARAM(3)> returned by
EVP_PKEY_key_fromdata_settable() may also be used programmatically, for
example with L<OSSL_PARAM_allocate_from_text(3)>.

=head1 SEE ALSO

L<EVP_PKEY_CTX_new(3)>, L<provider(7)>, L<EVP_PKEY_gettable_params(3)>,
L<OSSL_PARAM(3)>,
L<EVP_PKEY-RSA(7)>, L<EVP_PKEY-DSA(7)>, L<EVP_PKEY-DH(7)>, L<EVP_PKEY-EC(7)>,
L<EVP_PKEY-ED448(7)>, L<EVP_PKEY-X25519(7)>, L<EVP_PKEY-X448(7)>,
L<EVP_PKEY-ED25519(7)>

=head1 HISTORY

These functions were added in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2019-2020 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
L<https://www.openssl.org/source/license.html>.

=cut