X509_check_issued - checks if certificate is apparently issued by another
  certificate
 #include <openssl/x509v3.h>
 int X509_check_issued(X509 *issuer, X509 *subject);
X509_check_issued() checks if certificate subject was apparently
  issued using (CA) certificate issuer. This function takes into account
  not only matching of the issuer field of subject with the subject field
  of issuer, but also compares all sub-fields of the
  authorityKeyIdentifier extension of subject, as far as present,
  with the respective subjectKeyIdentifier, serial number, and issuer
  fields of issuer, as far as present. It also checks if the
  keyUsage field (if present) of issuer allows certificate
  signing. It does not check the certificate signature.
Function return X509_V_OK if certificate subject is issued by
  issuer or some X509_V_ERR* constant to indicate an error.
X509_verify_cert(3), X509_check_ca(3), verify(1)
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Licensed under the OpenSSL license (the "License"). You
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