OSSL_ENCODER_to_data, OSSL_ENCODER_to_bio, OSSL_ENCODER_to_fp - Routines to perform an encoding

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       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>.

3.5.0                                              2025-06-04                          OSSL_ENCODER_TO_BIO(3SSL)

OSSL_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   OSSL_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.

       OSSL_ENCODER_to_bio() runs the encoding process for the context ctx, with the output  going  to  the  BIOout.

       OSSL_ENCODER_to_fp() does the same thing as OSSL_ENCODER_to_bio(), except that the output is going to the
       FILEfp.

       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.

       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);

       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);

       The functions described here were added in OpenSSL 3.0.

       OSSL_ENCODER_to_data, OSSL_ENCODER_to_bio, OSSL_ENCODER_to_fp - Routines to perform an encoding

OSSL_ENCODER_to_bio(),  OSSL_ENCODER_to_fp()  and  OSSL_ENCODER_to_data()  return  1  on success, or 0 on
       failure.

provider(7), OSSL_ENCODER_CTX(3)

        #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.