doc/man3/EVP_PKEY_set1_encoded_public_key.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 EVP_PKEY_set1_encoded_public_key, EVP_PKEY_get1_encoded_public_key
   6 - functions to set and get public key data within an EVP_PKEY
   7
   8 =head1 SYNOPSIS
   9
  10  #include <openssl/evp.h>
  11
  12  int EVP_PKEY_set1_encoded_public_key(EVP_PKEY *pkey,
  13                                       const unsigned char *pub, size_t publen);
  14
  15  size_t EVP_PKEY_get1_encoded_public_key(EVP_PKEY *pkey, unsigned char **ppub);
  16
  17  #define EVP_PKEY_set1_tls_encodedpoint(pkey, pt, ptlen) \
  18          EVP_PKEY_set1_encoded_public_key((pkey), (pt), (ptlen))
  19
  20  #define EVP_PKEY_get1_tls_encodedpoint(pkey, ppt) \
  21          EVP_PKEY_get1_encoded_public_key((pkey), (ppt))
  22
  23 =head1 DESCRIPTION
  24
  25 EVP_PKEY_set1_encoded_public_key() can be used to set the public key value
  26 within an existing EVP_PKEY object. For the built-in OpenSSL algorithms this
  27 currently only works for those that support key exchange. Parameters are not
  28 set as part of this operation, so typically an application will create an
  29 EVP_PKEY first, set the parameters on it, and then call this function.
  30 For example setting the parameters might be done using
  31 L<EVP_PKEY_copy_parameters(3)>.
  32
  33 The format for the encoded public key will depend on the algorithm in use. For
  34 DH it should be encoded as a positive integer in big-endian form. For EC is
  35 should be a point conforming to Sec. 2.3.4 of the SECG SEC 1 ("Elliptic
  36 Curve Cryptography") standard. For X25519 and X448 it should be encoded in a
  37 format as defined by RFC7748.
  38
  39 The key to be updated is supplied in B<pkey>. The buffer containing the encoded
  40 key is pointed to be B<pub>. The length of the buffer is supplied in B<publen>.
  41
  42 EVP_PKEY_get1_encoded_public_key() does the equivalent operation except that
  43 the encoded public key is returned to the application. The key containing the
  44 public key data is supplied in B<pkey>. A buffer containing the encoded key will
  45 be allocated and stored in B<*ppub>. The length of the encoded public key is
  46 returned by the function. The application is responsible for freeing the
  47 allocated buffer.
  48
  49 =head1 RETURN VALUES
  50
  51 EVP_PKEY_set1_encoded_public_key() returns 1 for success and 0 or a negative
  52 value for failure.
  53
  54 EVP_PKEY_get1_encoded_public_key() return 1
  55
  56 =head1 EXAMPLES
  57
  58 See L<EVP_PKEY_derive_init(3)> and L<EVP_PKEY_derive(3)> for information about
  59 performing a key exchange operation.
  60
  61 =head2 Set up a peer's EVP_PKEY ready for a key exchange operation
  62
  63  #include <openssl/evp.h>
  64
  65  int exchange(EVP_PKEY *ourkey, unsigned char *peer_pub, size_t peer_pub_len)
  66  {
  67      EVP_PKEY *peerkey = EVP_PKEY_new();
  68
  69      if (peerkey == NULL || EVP_PKEY_copy_parameters(peerkey, ourkey) <= 0)
  70          return 0;
  71
  72      if (EVP_PKEY_set1_encoded_public_key(peerkey, peer_pub,
  73                                           peer_pub_len) <= 0)
  74          return 0;
  75
  76      /* Do the key exchange here */
  77
  78      EVP_PKEY_free(peerkey);
  79
  80      return 1;
  81  }
  82
  83 =head2 Get an encoded public key to send to a peer
  84
  85  #include <openssl/evp.h>
  86
  87  int get_encoded_pub_key(EVP_PKEY *ourkey)
  88  {
  89      unsigned char *pubkey;
  90      size_t pubkey_len;
  91
  92     pubkey_len = EVP_PKEY_get1_encoded_public_key(ourkey, &pubkey);
  93     if (pubkey_len == 0)
  94         return 0;
  95
  96     /*
  97      * Send the encoded public key stored in the buffer at "pubkey" and of
  98      * length pubkey_len, to the peer.
  99      */
 100
 101     OPENSSL_free(pubkey);
 102     return 1;
 103  }
 104
 105 =head1 SEE ALSO
 106
 107 L<EVP_PKEY_new(3)>, L<EVP_PKEY_copy_parameters(7)>,
 108 L<EVP_PKEY_derive_init(3)>, L<EVP_PKEY_derive(3)>,
 109 L<EVP_PKEY-DH(7)>, L<EVP_PKEY-EC(7)>, L<EVP_PKEY-X25519(7)>, L<EVP_PKEY-X448(7)>
 110
 111 =head1 HISTORY
 112
 113 These functions were added in OpenSSL 3.0.
 114
 115 =head1 COPYRIGHT
 116
 117 Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.
 118
 119 Licensed under the Apache License 2.0 (the "License").  You may not use
 120 this file except in compliance with the License.  You can obtain a copy
 121 in the file LICENSE in the source distribution or at
 122 L<https://www.openssl.org/source/license.html>.
 123
 124 =cut
 125