X509_SIGN(3ossl)

💖 X509_SIGN(3ossl) — the OpenSSL glow-up 💖

okay bestie, so this is the X509_SIGN(3ossl) page from the OpenSSL manual set, and it's literally all about signing stuff. certificates, cert requests, CRLs, the whole girlboss lineup. let's get into it ✨

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🌸 NAME 🌸

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 💅

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✨ SYNOPSIS ✨

#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);

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🎀 DESCRIPTION 🎀

so X509_sign() signs certificate x using private key pkey and message digest md, and then sets the signature in x. iconic. and X509_sign_ctx() also signs certificate x, but it uses the parameters that are chillin' inside digest context ctx instead. and listen — if the certificate information includes X.509 extensions, these two functions make sure the certificate bears X.509 version 3. no cap 🫶

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. same energy, different little guys 💜

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🦋 NOTES 🦋

X509_sign_ctx() is the one you reach for when the default parameters for the corresponding public key and digest just aren't it. like, it can be used to sign keys using RSA-PSS for example. versatility ✨

okay now for a lil technical tea, and this one's important, so pay attention bestie 🫖:

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. and if the signed portion of the structure gets modified, the encoding is not always updated — meaning a stale version is sometimes used. 😭

not a crisis tho: this is not normally a problem, because modifying the signed portion will invalidate the signature, and signing will always update the encoding. so like… it works out. periodt 💅

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🌈 RETURN VALUES 🌈

all of these functions return the size of the signature in bytes for success, and zero for failure. that's it, that's the vibe check 👑

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💜 SEE ALSO 💜

• 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)

go read those too, they're the supporting cast 🎀

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⭐ HISTORY ⭐

• the X509_sign(), X509_REQ_sign() and X509_CRL_sign() functions are available in all versions of OpenSSL. og status fr fr 👑
• 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. the new girls on the block 💅

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🌸 COPYRIGHT 🌸

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>.

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and that's the whole page bestie!! this lil masterpiece is from OpenSSL 3.5.9, dated 2026-09-29, and it lives under the name X509_SIGN(3ossl). mwah, go sign something iconic 💋🦋✨