OSSL_ENCODER_TO_BIO(3ossl)

💅 OSSL_ENCODER_TO_BIO — bestie's guide to actually encoding stuff

okay so welcome to the 3ossl girlies ✨ this is the OpenSSL family of man pages, and today we're covering total icons: OSSL_ENCODER_to_data, OSSL_ENCODER_to_bio, and OSSL_ENCODER_to_fp — the routines that actually do the encoding. no cap.

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✨ NAME ✨

OSSL_ENCODER_to_data, OSSL_ENCODER_to_bio, OSSL_ENCODER_to_fp — routines to perform an encoding 🎀

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🌸 SYNOPSIS 🌸

#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);

🦋 Feature availability macros 🦋

OSSL_ENCODER_to_fp() is only available when OPENSSL_NO_STDIO is undefined. that's it, that's the vibe check 👑

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💖 DESCRIPTION 💖

OSSL_ENCODER_to_data() — the buffer baddie

so OSSL_ENCODER_to_data() runs the whole encoding process for the context ctx, and the output goes to *pdata and *pdata_len. literally the main character of memory management 🫶

here's the tea on how it behaves:

• if *pdata is NULL when you call OSSL_ENCODER_to_data(), a buffer gets allocated using OPENSSL_zalloc(3), and *pdata gets set to point at the start of that buffer. then *pdata_len gets assigned its length by the time OSSL_ENCODER_to_data() returns ✨
• if *pdata is non-NULL when you call OSSL_ENCODER_to_data(), then *pdata_len is assumed to have its size. in that case, *pdata gets set to point after the encoded bytes, and *pdata_len gets assigned the number of remaining bytes. it's giving "pass the parcel" energy 🎁

OSSL_ENCODER_to_bio() — the BIO bestie

OSSL_ENCODER_to_bio() runs the encoding process for the context ctx, and the output goes to the BIO out. simple, iconic, done 💅

OSSL_ENCODER_to_fp() — same but for FILE

OSSL_ENCODER_to_fp() does the exact same thing as OSSL_ENCODER_to_bio(), except the output is going to the FILE fp. twins fr fr 👯

⚠️ okay important thing, don't skip: 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. that's on you, not on OpenSSL. you've been warned bestie 😭

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🔥 RETURN VALUES 🔥

OSSL_ENCODER_to_bio(), OSSL_ENCODER_to_fp() and OSSL_ENCODER_to_data() all return 1 on success, or 0 on failure. that's the whole vibe — binary, no in-between 🌈

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🌟 EXAMPLES 🌟

🧚 example one: pkey → PKCS#8, PEM format, into a bio

to encode a pkey as PKCS#8 with PEM format into a bio:

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);

like, look at her go. she ate 💅

🍓 example two: pkey → PKCS#8, DER format, AES-256-CBC encrypted, into a buffer

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

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);

(and yeah, that second one uses OSSL_ENCODER_CTX_set_cipher(ctx, "AES-256-CBC", NULL); — copying it exactly as the page gives it, no editing from me bestie 🙈)

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🎀 SEE ALSO 🎀

provider(7), OSSL_ENCODER_CTX(3)

go read those next, iykyk 💜

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⭐ HISTORY ⭐

the functions described here were added in OpenSSL 3.0. glow-up era 🌸

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👑 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>.

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and that's the page, bestie 🫶 this was OpenSSL 3.5.6, dated 2026-04-07, and the whole thing is filed under OSSL_ENCODER_TO_BIO(3ossl) — mwah, go encode something iconic 💖✨