PKCS7_SIGN_ADD_SIGNER(3ossl)

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version 15.1 · 2 versions
, in freebsd 15.1

okay bestie, this is the PKCS7_SIGN_ADD_SIGNER(3ossl) page — the OpenSSL one about adding info to a PKCS7 structure — and we’re gonna make it make sense 💅✨

🌸 NAME 🌸

PKCS7_sign_add_signer, PKCS7_add_certificate, PKCS7_add_crl — add information to PKCS7 structure 🫶

✨ SYNOPSIS ✨

#include <openssl/pkcs7.h>

PKCS7_SIGNER_INFO *PKCS7_sign_add_signer(PKCS7 *p7, X509 *signcert,
                                         EVP_PKEY *pkey, const EVP_MD *md, int flags);
int PKCS7_add_certificate(PKCS7 *p7, X509 *cert);
int PKCS7_add_crl(PKCS7 *p7, X509_CRL *crl);

💖 DESCRIPTION 💖

PKCS7_sign_add_signer() adds a signer to a PKCS7 signed data structure p7 — with certificate signcert, private key pkey, and message digest md 👑✨

The PKCS7 structure should be obtained from an initial call to PKCS7_sign() with the flag PKCS7_PARTIAL set, or when you’re re-signing a valid PKCS#7 signed data structure. iykyk 🧚

If the md parameter is NULL, then the default digest for the public key algorithm will be used. lowkey convenient 🍓

important: unless the PKCS7_REUSE_DIGEST flag is set, the returned PKCS7 structure is not complete and must be finalized either by streaming (if applicable) or by a call to PKCS7_final(). don’t forget this part bestie 😭

🔥 NOTES 🔥

The main purpose of this function is to give you finer control over a PKCS#7 signed data structure — the situations where the simpler PKCS7_sign() function defaults are just not appropriate. For example: if multiple signers are needed, or if non default digest algorithms are needed 💅

Any of the following flags can be passed in the flags parameter — OR them together, bestie 🫶

  • PKCS7_REUSE_DIGEST — okay so an attempt is made to copy the content digest value from the PKCS7 structure, so you can add a signer to an existing structure. An error occurs if a matching digest value cannot be found to copy. The returned PKCS7 structure will be valid and finalized when this flag is set ✨
  • PKCS7_PARTIAL — if this is set in addition to PKCS7_REUSE_DIGEST, then the PKCS7_SIGNER_INO structure will not be finalized, so additional attributes can be added. In this case an explicit call to PKCS7_SIGNER_INFO_sign() is needed to finalize it 👑
  • PKCS7_NOCERTS — if set, the signer’s certificate will not be included in the PKCS7 structure. The signer’s certificate must still be supplied in the signcert parameter though. This can reduce the size of the signature if the signer’s certificate can be obtained by other means: for example, a previously signed message 🎀
  • PKCS7_NOATTR — if set, then no authenticatedAttributes will be used. The signedData structure includes several PKCS#7 authenticatedAttributes including the signing time, the PKCS#7 content type and the supported list of ciphers in an SMIMECapabilities attribute — this flag says nope to all that 🙈
  • PKCS7_NOSMIMECAP — if set, then just the SMIMECapabilities are omitted 🌸

If present, the SMIMECapabilities attribute indicates support for the following algorithms: triple DES, 128 bit RC2, 64 bit RC2, DES and 40 bit RC2. If any of these algorithms is disabled then it will not be included 🦋

PKCS7_sign_add_signers() returns an internal pointer to the PKCS7_SIGNER_INFO structure just added, which can be used to set additional attributes before it is finalized 💖

PKCS7_add_certificate() adds to the PKCS7 structure p7 the certificate cert, which may be an end-entity (signer) certificate or a CA certificate useful for chain building. This is done internally by PKCS7_sign_ex(3) and similar signing functions. It may have to be used before calling PKCS7_verify(3) in order to provide any missing certificate(s) needed for verification ⭐

PKCS7_add_crl() adds the CRL crl to the PKCS7 structure p7. This may be called to provide certificate status information to be included when signing or to use when verifying the PKCS7 structure 🎀

🌈 RETURN VALUES 🌈

PKCS7_sign_add_signers() returns an internal pointer to the PKCS7_SIGNER_INFO structure just added, or NULL if an error occurs 💀

PKCS7_add_certificate() and PKCS7_add_crl() return 1 on success, 0 on error ✨

👑 SEE ALSO 👑

🦋 HISTORY 🦋

The PPKCS7_sign_add_signer() function was added in OpenSSL 1.0.0. yes, that double-P is literally right there in the original — iconic typo behavior ngl 😭💅

Copyright 2007-2016 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>.

okay that’s the whole page bestie 🫶 brought to you by OpenSSL 3.5.6, dated 2026-04-07, and it’s the PKCS7_SIGN_ADD_SIGNER(3ossl) manual page — periodt 💅✨

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