libcrypto/man/OSSL_ENCODER_to_bio.3

 $NetBSD: OSSL_ENCODER_to_bio.3,v 1.5 2026/04/08 17:06:45 christos Exp $

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 Title "OSSL_ENCODER_to_bio 3"  OSSL_ENCODER_to_bio 3 2026-04-07 3.5.6 OpenSSL
 For nroff, turn off justification. Always turn off hyphenation; it makes
 way too many mistakes in technical documents.
.nh
 NAME
OSSL_ENCODER_to_data,
OSSL_ENCODER_to_bio,
OSSL_ENCODER_to_fp
\- Routines to perform an encoding
 SYNOPSIS
 Header "SYNOPSIS" .Vb 1
 #include <openssl/encoder.h>
\&
 int OSSL_ENCODER_to_data(OSSL_ENCODER_CTX *ctx, unsigned char **pdata,
  size_t *pdata_len);
 int OSSL_ENCODER_to_bio(OSSL_ENCODER_CTX *ctx, BIO *out);
 int OSSL_ENCODER_to_fp(OSSL_ENCODER_CTX *ctx, FILE *fp);
.Ve

Feature availability macros:
 "OSSL_ENCODER_to_fp() is only available when OPENSSL_NO_STDIO is undefined." 4
 Item "OSSL_ENCODER_to_fp() is only available when OPENSSL_NO_STDIO is undefined."  DESCRIPTION
 Header "DESCRIPTION" \fBOSSL_ENCODER_to_data() runs the encoding process for the context ctx,
with the output going to the *pdata and *pdata_len.
If *pdata is NULL when OSSL_ENCODER_to_data() is called, a buffer will be
allocated using OPENSSL_zalloc\|(3), and *pdata will be set to point at
the start of that buffer, and *pdata_len will be assigned its length when
\fBOSSL_ENCODER_to_data() returns.
If *pdata is non-NULL when OSSL_ENCODER_to_data() is called, *pdata_len
is assumed to have its size. In this case, *pdata will be set to point
after the encoded bytes, and *pdata_len will be assigned the number of
remaining bytes.

\fBOSSL_ENCODER_to_bio() runs the encoding process for the context ctx, with
the output going to the BIO out.

\fBOSSL_ENCODER_to_fp() does the same thing as OSSL_ENCODER_to_bio(), except
that the output is going to the FILE fp.

For OSSL_ENCODER_to_bio() and OSSL_ENCODER_to_fp(), the application is
required to set up the BIO or FILE properly, for example to have
it in text or binary mode as is appropriate for the encoder output type.
 "RETURN VALUES"
 Header "RETURN VALUES" \fBOSSL_ENCODER_to_bio(), OSSL_ENCODER_to_fp() and OSSL_ENCODER_to_data()
return 1 on success, or 0 on failure.
 EXAMPLES
 Header "EXAMPLES" To encode a pkey as PKCS#8 with PEM format into a bio:

.Vb 4
 OSSL_ENCODER_CTX *ectx;
 const char *format = "PEM";
 const char *structure = "PrivateKeyInfo"; /* PKCS#8 structure */
 const unsigned char *pass = "my password";
\&
 ectx = OSSL_ENCODER_CTX_new_for_pkey(pkey,
  OSSL_KEYMGMT_SELECT_KEYPAIR
  | OSSL_KEYMGMT_SELECT_DOMAIN_PARAMETERS,
  format, structure,
  NULL);
 if (ectx == NULL) {
  /* error: no suitable potential encoders found */
 }
 if (pass != NULL)
  OSSL_ENCODER_CTX_set_passphrase(ectx, pass, strlen(pass));
 if (OSSL_ENCODER_to_bio(ectx, bio)) {
  /* pkey was successfully encoded into the bio */
 } else {
  /* encoding failure */
 }
 OSSL_ENCODER_CTX_free(ectx);
.Ve

To encode a pkey as PKCS#8 with DER format encrypted with
AES-256-CBC into a buffer:

.Vb 6
 OSSL_ENCODER_CTX *ectx;
 const char *format = "DER";
 const char *structure = "PrivateKeyInfo"; /* PKCS#8 structure */
 const unsigned char *pass = "my password";
 unsigned char *data = NULL;
 size_t datalen;
\&
 ectx = OSSL_ENCODER_CTX_new_for_pkey(pkey,
  OSSL_KEYMGMT_SELECT_KEYPAIR
  | OSSL_KEYMGMT_SELECT_DOMAIN_PARAMETERS,
  format, structure,
  NULL);
 if (ectx == NULL) {
  /* error: no suitable potential encoders found */
 }
 if (pass != NULL) {
  OSSL_ENCODER_CTX_set_passphrase(ectx, pass, strlen(pass));
  OSSL_ENCODER_CTX_set_cipher(ctx, "AES-256-CBC", NULL);
 }
 if (OSSL_ENCODER_to_data(ectx, &data, &datalen)) {
  /*
  * pkey was successfully encoded into a newly allocated
  * data buffer
  */
 } else {
  /* encoding failure */
 }
 OSSL_ENCODER_CTX_free(ectx);
.Ve
 "SEE ALSO"
 Header "SEE ALSO" \fBprovider\|(7), OSSL_ENCODER_CTX\|(3)
 HISTORY
 Header "HISTORY" The functions described here were added in OpenSSL 3.0.
 COPYRIGHT
 Header "COPYRIGHT" Copyright 2019-2021 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>.