CMS_GET0_SIGNERINFOS(3)

💅 CMS_GET0_SIGNERINFOS(3) — Library Functions Manual, bestie edition 🎀

okay so this is the libcrypto manual page for the CMS SignedData signer functions, and we're gonna make it make sense. No cap.

🌸 NAME 🌸

CMS_get0_SignerInfos, CMS_SignerInfo_get_version, CMS_SignerInfo_get0_signer_id, CMS_SignerInfo_get0_signature, CMS_SignerInfo_cert_cmp, CMS_SignerInfo_set1_signer_cert — CMS SignedData signer functions. Periodt.

✨ SYNOPSIS ✨

The library is “libcrypto”, and you include this:

#include <openssl/cms.h>

Then the function lineup is literally this:

STACK_OF(CMS_SignerInfo) *
CMS_get0_SignerInfos(CMS_ContentInfo *cms);

int
CMS_SignerInfo_get_version(CMS_SignerInfo *si, long *version);

int
CMS_SignerInfo_get0_signer_id(CMS_SignerInfo *si,
    ASN1_OCTET_STRING **keyid, X509_NAME **issuer, ASN1_INTEGER **sno);

ASN1_OCTET_STRING *
CMS_SignerInfo_get0_signature(CMS_SignerInfo *si);

int
CMS_SignerInfo_cert_cmp(CMS_SignerInfo *si, X509 *certificate);

void
CMS_SignerInfo_set1_signer_cert(CMS_SignerInfo *si, X509 *signer);

🦋 DESCRIPTION 🦋

• CMS_get0_SignerInfos() — returns all the SignerInfo structures associated with the SignedData structure cms. It's giving "gimme the whole squad."
• CMS_SignerInfo_get_version() — sets *version to the syntax version number of the SignerInfo structure si.
• CMS_SignerInfo_get0_signer_id() — retrieves the certificate SignerIdentifier associated with the SignerInfo structure si. Either the SubjectKeyIdentifier will be set in keyid, or both issuer name and serial number will be set in issuer and sno.
• CMS_SignerInfo_get0_signature() — retrieves the signature field of si. The application program is allowed to modify the data pointed to. Yeah bestie, allowed.
• CMS_SignerInfo_cert_cmp() — compares the certificate against the signer identifier of si.
• CMS_SignerInfo_set1_signer_cert() — sets the signer certificate of si to signer.

The main purpose of these functions is to enable an application to look up signer certificates using any appropriate technique when the simpler method of CMS_verify(3) is not appropriate.

In typical usage, an application retrieves all CMS_SignerInfo structures using CMS_get0_SignerInfos() and retrieves the identifier information using CMS. It will then obtain the signer certificate by some unspecified means (or return an error if it cannot be found) and set it using CMS_SignerInfo_set1_signer_cert(). Once all signer certificates have been set, CMS_verify(3) can be used. Slay.

💖 RETURN VALUES 💖

• CMS_get0_SignerInfos() returns an internal pointer to all the CMS_SignerInfo structures, or NULL if there are no signers or if cms is not of the type SignedData.
• CMS_SignerInfo_get_version() always succeeds and returns 1.
• CMS_SignerInfo_get0_signer_id() returns 1 for success or 0 for failure.
• CMS_SignerInfo_get0_signature() returns an internal pointer to the signature.
• CMS_SignerInfo_cert_cmp() returns 0 for a match or non-zero otherwise.
• Any error can be obtained from ERR_get_error(3).

👑 SEE ALSO 👑

• CMS_ContentInfo_new(3)
• CMS_signed_add1_attr(3)
• CMS_verify(3)

🌈 STANDARDS 🌈

• RFC 5652: Cryptographic Message Syntax (CMS)
  • section 5.1: SignedData Type
  • section 5.3: SignerInfo Type

🎀 HISTORY 🎀

CMS_get0_SignerInfos(), CMS_SignerInfo_get0_signer_id(), CMS_SignerInfo_cert_cmp(), and CMS_SignerInfo_set1_signer_cert() first appeared in OpenSSL 0.9.8h, and CMS_SignerInfo_get0_signature() in OpenSSL 1.0.2. These functions have been available since OpenBSD 6.7.

CMS_SignerInfo_get_version() first appeared in OpenBSD 7.4.

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xoxo 💜 this cutie is from Debian, dated June 8, 2025, and it lives under the header CMS_GET0_SIGNERINFOS(3) — iconic.