OSSL_DECODER_FROM_BIO(3ossl)

💖 OSSL_DECODER_FROM_BIO(3ossl) 💖

okay bestie, so this is a page from the OpenSSL manual, and it's all about the routines that actually do the decoding: OSSL_DECODER_from_data, OSSL_DECODER_from_bio and OSSL_DECODER_from_fp. The whole vibe is "I have a decoder context, now let me feed it some bytes and watch it cook" ✨

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🌸 NAME 🌸

OSSL_DECODER_from_data, OSSL_DECODER_from_bio, OSSL_DECODER_from_fp — routines to perform a decoding. that's it, that's the whole job description, and honestly? iconic. 👑

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🎀 SYNOPSIS 🎀

#include <openssl/decoder.h>

int OSSL_DECODER_from_bio(OSSL_DECODER_CTX *ctx, BIO *in);
int OSSL_DECODER_from_fp(OSSL_DECODER_CTX *ctx, FILE *fp);
int OSSL_DECODER_from_data(OSSL_DECODER_CTX *ctx, const unsigned char **pdata,
                           size_t *pdata_len);

Feature availability macros:

• OSSL_DECODER_from_fp() is only available when OPENSSL_NO_STDIO is undefined.

so if OPENSSL_NO_STDIO is a thing on your build, that fp one is literally just not there. vibe check failed, no FILE for you 🫶

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✨ DESCRIPTION ✨

OSSL_DECODER_from_data() runs the decoding process for the context ctx, with input coming from *pdata, *pdata_len bytes long. Both *pdata and *pdata_len must be non-NULL. When OSSL_DECODER_from_data() returns, *pdata is updated to point at the location after what has been decoded, and *pdata_len to have the number of remaining bytes.

the way that it just moves your pointer forward... it's giving "I ate those bytes and now I'm handing you the leftovers" 😭

OSSL_DECODER_from_bio() runs the decoding process for the context ctx, with the input coming from the BIO in. Should it make a difference, it's recommended to have the BIO set in binary mode rather than text mode.

OSSL_DECODER_from_fp() does the same thing as OSSL_DECODER_from_bio(), except that the input is coming from the FILE fp.

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💅 RETURN VALUES 💅

OSSL_DECODER_from_bio(), OSSL_DECODER_from_data() and OSSL_DECODER_from_fp() return 1 on success, or 0 on failure.

1 = slay. 0 = bestie no. 💀

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🦋 EXAMPLES 🦋

To decode an RSA key encoded with PEM from a bio:

OSSL_DECODER_CTX *dctx;
EVP_PKEY *pkey = NULL;
const char *format = "PEM";   /* NULL for any format */
const char *structure = NULL; /* any structure */
const char *keytype = "RSA";  /* NULL for any key */
const unsigned char *pass = "my password";

dctx = OSSL_DECODER_CTX_new_for_pkey(&pkey, format, structure,
                                     keytype,
                                     OSSL_KEYMGMT_SELECT_KEYPAIR,
                                     NULL, NULL);
if (dctx == NULL) {
    /* error: no suitable potential decoders found */
}
if (pass != NULL)
    OSSL_DECODER_CTX_set_passphrase(dctx, pass, strlen(pass));
if (OSSL_DECODER_from_bio(dctx, bio)) {
    /* pkey is created with the decoded data from the bio */
} else {
    /* decoding failure */
}
OSSL_DECODER_CTX_free(dctx);

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To decode an EC key encoded with DER from a buffer:

OSSL_DECODER_CTX *dctx;
EVP_PKEY *pkey = NULL;
const char *format = "DER";   /* NULL for any format */
const char *structure = NULL; /* any structure */
const char *keytype = "EC";   /* NULL for any key */
const unsigned char *pass = NULL
const unsigned char *data = buffer;
size_t datalen = sizeof(buffer);

dctx = OSSL_DECODER_CTX_new_for_pkey(&pkey, format, structure,
                                     keytype,
                                     OSSL_KEYMGMT_SELECT_KEYPAIR
                                     | OSSL_KEYMGMT_SELECT_DOMAIN_PARAMETERS,
                                     NULL, NULL);
if (dctx == NULL) {
    /* error: no suitable potential decoders found */
}
if (pass != NULL)
    OSSL_DECODER_CTX_set_passphrase(dctx, pass, strlen(pass));
if (OSSL_DECODER_from_data(dctx, &data, &datalen)) {
    /* pkey is created with the decoded data from the buffer */
} else {
    /* decoding failure */
}
OSSL_DECODER_CTX_free(dctx);

no cap, notice how in the first one it's from_bio with a BIO, and in the second it's from_data with &data and &datalen. same energy, different snack. 🍓

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🌈 SEE ALSO 🌈

provider(7), OSSL_DECODER_CTX(3)

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⭐ HISTORY ⭐

The functions described here were added in OpenSSL 3.0.

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👑 COPYRIGHT 👑

Copyright 2020-2023 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 whole page, bestie 💖 this was served up from OpenSSL 3.5.9, dated 2026-09-29, under the title OSSL_DECODER_FROM_BIO(3ossl). go forth and decode, you absolute main character 🧚✨