#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 actually check the certificate signature. An error is returned if the issuer or the subject are incomplete certificates.
X509_check_issued() returns X509_V_OK if all checks are successful or some X509_V_ERR* constant to indicate an error.
X509_verify_cert(3), X509_verify(3), X509_check_ca(3), openssl-verify(1), X509_self_signed(3)
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