gnutls_certificate_get_issuer - Linux

Overview

gnutls_certificate_get_issuer is a library function used to retrieve the issuer information from a provided X.509 certificate. This is useful for tracing the chain of trust and verifying the certificate authority (CA) that issued the target certificate.

Syntax

#include <gnutls/gnutls.h>

int gnutls_certificate_get_issuer(gnutls_certificate_type_t type,
                                  gnutls_datum_t cert, gnutls_x509_crt_t *issuer);

Options/Flags

None.

Examples

Retrieve the issuer from a certificate stored in a file:

#include <gnutls/gnutls.h>

int main(int argc, char *argv[]) {
  gnutls_certificate_type_t type = GNUTLS_CRT_X509;
  gnutls_datum_t cert = { .data = (unsigned char *)"certificate.pem",
                           .size = strlen("certificate.pem") };
  gnutls_x509_crt_t issuer;

  if (gnutls_certificate_get_issuer(type, cert, &issuer) == 0) {
    // issuer information is now available in the issuer variable
    // ... process the issuer information as needed
  }

  gnutls_x509_crt_deinit(issuer);

  return 0;
}

Common Issues

• Ensure that the provided certificate is in a recognizable format (e.g., X.509).
• Check the return value of the function to ensure successful retrieval of the issuer.

Integration

gnutls_certificate_get_issuer can be used with other GNUTLS functions to validate certificates and establish secure connections. For example, it can be used in conjunction with gnutls_certificate_get_dn to extract specific fields from the issuer’s distinguished name.

Related Commands

• gnutls_certificate_get_subject
• gnutls_certificate_get_subject_alt_name
• gnutls_certificate_get_validity