UA-.NETStandard/tests/Opc.Ua.Core.Security.Tests/TestCertificateFactory.cs

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using System;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using Opc.Ua.Security.Certificates;

namespace Opc.Ua.Core.Security.Tests
{
    /// <summary>
    /// Programmatically generates X.509 application instance
    /// certificates with controlled flaws (expired, not-yet-valid,
    /// wrong-CN, weak-key, SHA1, corrupted, CA-without-app-instance,
    /// CA-issued, etc.) for use by the
    /// <see cref="SecurityCertValidationTests"/> and
    /// <see cref="SecurityNoneSession10Tests"/> conformance fixtures.
    /// Backed by the existing <see cref="CertificateBuilder"/>
    /// infrastructure — no third-party dependencies.
    /// </summary>
    internal static class TestCertificateFactory
    {
        /// <summary>
        /// Default RSA key size for valid (non-flawed) certificates.
        /// </summary>
        public const ushort DefaultRsaKeySize = 2048;

        /// <summary>
        /// Default lifetime for a freshly issued certificate.
        /// </summary>
        public static readonly TimeSpan DefaultLifetime = TimeSpan.FromDays(365);

        /// <summary>
        /// Generates a fully valid RSA application instance certificate
        /// containing the supplied application URI as a UniformResourceIdentifier
        /// SAN entry (and the host name so it passes domain-name checks).
        /// </summary>
        public static Certificate CreateValidAppInstanceCert(
            string subjectName,
            string applicationUri,
            ushort keySize = DefaultRsaKeySize,
            HashAlgorithmName? hashAlgorithm = null,
            string hostName = "localhost")
        {
            ICertificateBuilder builder = CertificateBuilder.Create(subjectName)
                .SetNotBefore(DateTime.UtcNow.AddDays(-1))
                .SetLifeTime(DefaultLifetime);
            if (hashAlgorithm.HasValue)
            {
                builder = builder.SetHashAlgorithm(hashAlgorithm.Value);
            }
            return builder
                .AddExtension(BuildSubjectAlternativeName(applicationUri, hostName))
                .SetRSAKeySize(keySize)
                .CreateForRSA();
        }

        /// <summary>
        /// Returns an application instance certificate whose NotAfter
        /// is in the past.
        /// </summary>
        public static Certificate CreateExpiredAppInstanceCert(
            string subjectName,
            string applicationUri,
            string hostName = "localhost")
        {
            return CertificateBuilder.Create(subjectName)
                .SetNotBefore(DateTime.UtcNow.AddDays(-365))
                .SetNotAfter(DateTime.UtcNow.AddMinutes(-5))
                .AddExtension(BuildSubjectAlternativeName(applicationUri, hostName))
                .SetRSAKeySize(DefaultRsaKeySize)
                .CreateForRSA();
        }

        /// <summary>
        /// Returns an application instance certificate whose NotBefore
        /// is in the future.
        /// </summary>
        public static Certificate CreateNotYetValidAppInstanceCert(
            string subjectName,
            string applicationUri,
            string hostName = "localhost")
        {
            return CertificateBuilder.Create(subjectName)
                .SetNotBefore(DateTime.UtcNow.AddDays(7))
                .SetNotAfter(DateTime.UtcNow.AddDays(180))
                .AddExtension(BuildSubjectAlternativeName(applicationUri, hostName))
                .SetRSAKeySize(DefaultRsaKeySize)
                .CreateForRSA();
        }

        /// <summary>
        /// Returns an application instance certificate that contains
        /// the BasicConstraints CA:TRUE flag — a misconfiguration the
        /// server should reject because the certificate isn't an
        /// application instance certificate.
        /// </summary>
        public static Certificate CreateCaCert(
            string subjectName,
            string applicationUri,
            string hostName = "localhost")
        {
            return CertificateBuilder.Create(subjectName)
                .SetCAConstraint(0)
                .SetLifeTime(DefaultLifetime)
                .AddExtension(BuildSubjectAlternativeName(applicationUri, hostName))
                .SetRSAKeySize(DefaultRsaKeySize)
                .CreateForRSA();
        }

        /// <summary>
        /// Returns a self-signed certificate signed with SHA1 and the
        /// supplied key size — used to verify the server rejects weak
        /// crypto.
        /// </summary>
        public static Certificate CreateSha1AppInstanceCert(
            string subjectName,
            string applicationUri,
            ushort keySize,
            string hostName = "localhost")
        {
            return CertificateBuilder.Create(subjectName)
                .SetLifeTime(DefaultLifetime)
                .SetHashAlgorithm(HashAlgorithmName.SHA1)
                .AddExtension(BuildSubjectAlternativeName(applicationUri, hostName))
                .SetRSAKeySize(keySize)
                .CreateForRSA();
        }

        /// <summary>
        /// Returns a self-signed certificate whose SAN entries point at
        /// a different host name from the one the test will connect
        /// to.
        /// </summary>
        public static Certificate CreateWrongHostnameAppInstanceCert(
            string subjectName,
            string applicationUri)
        {
            return CertificateBuilder.Create(subjectName)
                .SetLifeTime(DefaultLifetime)
                .AddExtension(BuildSubjectAlternativeName(applicationUri, "remote-host.invalid"))
                .SetRSAKeySize(DefaultRsaKeySize)
                .CreateForRSA();
        }

        /// <summary>
        /// Mutates the signature bytes of the provided DER-encoded
        /// certificate so signature verification fails. The
        /// modification is made on a clone — the input certificate is
        /// not altered.
        /// </summary>
        /// <exception cref="ArgumentNullException"><paramref name="cert"/> is <c>null</c>.</exception>
        public static Certificate CorruptCertSignature(Certificate cert)
        {
            if (cert == null)
            {
                throw new ArgumentNullException(nameof(cert));
            }
            byte[] der = cert.AsX509Certificate2().Export(X509ContentType.Cert);
            // Mutate a byte near the end of the DER blob — the
            // signature value sits at the tail.
            der[^5] ^= 0xFF;
            return Certificate.FromRawData(der);
        }

        /// <summary>
        /// Returns a CA certificate suitable for issuing application
        /// instance certificates. The CA itself is self-signed.
        /// </summary>
        public static Certificate CreateIssuingCa(string subjectName)
        {
            return CertificateBuilder.Create(subjectName)
                .SetCAConstraint(0)
                .SetLifeTime(TimeSpan.FromDays(2 * 365))
                .SetRSAKeySize(DefaultRsaKeySize)
                .CreateForRSA();
        }

        /// <summary>
        /// Returns an application instance certificate signed by the
        /// supplied CA. Used to produce both trusted-issued certs and
        /// untrusted-issued certs (the trust state is decided by what
        /// is added to the server's stores).
        /// </summary>
        /// <exception cref="ArgumentNullException"><paramref name="issuerCa"/> is <c>null</c>.</exception>
        public static Certificate CreateCaIssuedAppInstanceCert(
            string subjectName,
            string applicationUri,
            Certificate issuerCa,
            string hostName = "localhost")
        {
            if (issuerCa == null)
            {
                throw new ArgumentNullException(nameof(issuerCa));
            }
            return CertificateBuilder.Create(subjectName)
                .SetLifeTime(DefaultLifetime)
                .AddExtension(BuildSubjectAlternativeName(applicationUri, hostName))
                .SetIssuer(issuerCa)
                .SetRSAKeySize(DefaultRsaKeySize)
                .CreateForRSA();
        }

        private static X509SubjectAltNameExtension BuildSubjectAlternativeName(
            string applicationUri,
            string hostName)
        {
            return new X509SubjectAltNameExtension(applicationUri, [hostName]);
        }
    }
}