Extract issuer (CN) from SSL Certificate using openssl in iOS

Question

I want to extract Issuer CN (Common name) from SSL certificate using openSSL in iOS. I am using the link http://pastebin.com/Vn797Sc0 for extracting the information from the certificate. I am getting the issuer name but could not extract Issuer Common name(Common name) in iOS. Thanks in advance

Answer 1

You can extract the Common Name like the Organization field in the code you linked (Not tested)

static NSString * CertificateGetIssuerCommonName(X509 *certificateX509) {
    NSString *issuerCN = nil;
    if (certificateX509 != NULL) {
        X509_NAME *issuerX509Name = X509_get_issuer_name(certificateX509);
        if (issuerX509Name != NULL) {
            int nid = OBJ_txt2nid("CN");
            int index = X509_NAME_get_index_by_NID(issuerX509Name, nid, -1);
            if (index != -1) {
                X509_NAME_ENTRY *issuerNameCommonName = X509_NAME_get_entry(issuerX509Name, index);

                if (issuerNameEntry) {
                    ASN1_STRING *issuerCNASN1 = X509_NAME_ENTRY_get_data(issuerNameEntry);

                    if (issuerCNASN1 != NULL) {
                        unsigned char *issuerCName = ASN1_STRING_data(issuerCNASN1);
                        issuerCN = [NSString stringWithUTF8String:(char *)issuerCName];
                    }
                }
            }
        }
    }

    return issuerCN;
}

Answer 2

static NSString * CertificateGetIssuerName(X509 *certificateX509)
{
    NSString *issuer = nil;
    if (certificateX509 != NULL) {
        X509_NAME *issuerX509Name = X509_get_issuer_name(certificateX509);

        if (issuerX509Name != NULL) {
             //NID_commonName extract the common name of the issuer
            int index = X509_NAME_get_index_by_NID(issuerX509Name, NID_commonName, -1);

            X509_NAME_ENTRY *issuerNameEntry = X509_NAME_get_entry(issuerX509Name, index);

            if (issuerNameEntry) {
                ASN1_STRING *issuerNameASN1 = X509_NAME_ENTRY_get_data(issuerNameEntry);

                if (issuerNameASN1 != NULL) {
                    unsigned char *issuerName = ASN1_STRING_data(issuerNameASN1);
                    issuer = [NSString stringWithUTF8String:(char *)issuerName];
                }
            }
        }
    }

    return issuer;
}