Qt OPC UA X509 Support

This example shows how client applications can generate their own self-signed certificate or generate a certificate signing request.

Generating RSA key

At first, an RSA key is generated:

QOpcUaKeyPair key;
key.generateRsaKey(QOpcUaKeyPair::RsaKeyStrength::Bits2048);

The private key can be saved to a file for further usage:

QByteArray keyData = key.privateKeyToByteArray(QOpcUaKeyPair::Cipher::Unencrypted, QString());

QFile keyFile(u"privateKey.pem"_s);
keyFile.open(QFile::WriteOnly);
keyFile.write(keyData);
keyFile.close();

Generating certificate signing requests

Next, a certificate signing request is created. It is also necessary to set the subject of the certificate and add all the extensions needed for OPC UA.

QOpcUaX509CertificateSigningRequest csr;

// Set the subject of the certificate
QOpcUaX509DistinguishedName dn;
dn.setEntry(QOpcUaX509DistinguishedName::Type::CommonName, u"QtOpcUaViewer"_s);
dn.setEntry(QOpcUaX509DistinguishedName::Type::CountryName, u"DE"_s);
dn.setEntry(QOpcUaX509DistinguishedName::Type::LocalityName, u"Berlin"_s);
dn.setEntry(QOpcUaX509DistinguishedName::Type::StateOrProvinceName, u"Berlin"_s);
dn.setEntry(QOpcUaX509DistinguishedName::Type::OrganizationName, u"The Qt Company"_s);
csr.setSubject(dn);

Now there are two options:

1. When you need to get your certificate signing request signed by a certificate authority, you have to use the request data.

QByteArray certificateSigningRequestData = csr.createRequest(key);

2. When there is no certificate authority, you have to self-sign the request.

QByteArray selfSignedCertificateData = csr.createSelfSignedCertificate(key);

Files:

• x509/CMakeLists.txt
• x509/main.cpp
• x509/x509.pro