X509_sign, X509_sign_ctx, X509_REQ_sign, X509_REQ_sign_ctx, X509_ACERT_sign, X509_ACERT_sign_ctx,

       Copyright 2015-2024 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>.

3.5.0                                              2025-06-04                                    X509_SIGN(3SSL)

X509_sign() signs certificate x using private key pkey and message digest md and sets the signature in x.
       X509_sign_ctx() also signs certificate x but uses the parameters contained in digest context ctx.  If the
       certificate information includes X.509 extensions, these two functions make sure that the certificate
       bears X.509 version 3.

       X509_REQ_sign(), X509_REQ_sign_ctx(), X509_ACERT_sign(), X509_ACERT_sign_ctx(), X509_CRL_sign(), and
       X509_CRL_sign_ctx() sign certificate requests and CRLs, respectively.

       The X509_sign(), X509_REQ_sign() and X509_CRL_sign() functions are available in all versions of OpenSSL.

       The X509_sign_ctx(), X509_REQ_sign_ctx() and X509_CRL_sign_ctx() functions were added in OpenSSL 1.0.1.

       The X509_ACERT_sign() and X509_ACERT_sign_ctx() functions were added in OpenSSL 3.4.

       X509_sign, X509_sign_ctx, X509_REQ_sign, X509_REQ_sign_ctx, X509_ACERT_sign, X509_ACERT_sign_ctx,
       X509_CRL_sign, X509_CRL_sign_ctx - sign certificate, certificate request, or CRL signature

X509_sign_ctx() is used where the default parameters for the corresponding public key and digest are not
       suitable. It can be used to sign keys using RSA-PSS for example.

       For efficiency reasons and to work around ASN.1 encoding issues the encoding of the signed portion of a
       certificate, certificate request and CRL is cached internally. If the signed portion of the structure is
       modified the encoding is not always updated meaning a stale version is sometimes used. This is not
       normally a problem because modifying the signed portion will invalidate the signature and signing will
       always update the encoding.

       All functions return the size of the signature in bytes for success and zero for failure.

ERR_get_error(3), X509_NAME_add_entry_by_txt(3), X509_new(3), X509_verify_cert(3), X509_verify(3),
       X509_REQ_verify_ex(3), X509_REQ_verify(3), X509_CRL_verify(3)

        #include <openssl/x509.h>

        int X509_sign(X509 *x, EVP_PKEY *pkey, const EVP_MD *md);
        int X509_sign_ctx(X509 *x, EVP_MD_CTX *ctx);

        int X509_REQ_sign(X509_REQ *x, EVP_PKEY *pkey, const EVP_MD *md);
        int X509_REQ_sign_ctx(X509_REQ *x, EVP_MD_CTX *ctx);

        int X509_CRL_sign(X509_CRL *x, EVP_PKEY *pkey, const EVP_MD *md);
        int X509_CRL_sign_ctx(X509_CRL *x, EVP_MD_CTX *ctx);

        #include <openssl/x509_acert.h>

        int X509_ACERT_sign(X509_ACERT *x, EVP_PKEY *pkey, const EVP_MD *md);
        int X509_ACERT_sign_ctx(X509_ACERT *x, EVP_MD_CTX *ctx);