/// <summary>
/// Throws an exception if validation fails.
/// </summary>
/// <param name="certificates">The certificates to be checked.</param>
/// <exception cref="ServiceResultException">If certificate[0] cannot be accepted</exception>
protected virtual async Task InternalValidate(X509Certificate2Collection certificates)
{
X509Certificate2 certificate = certificates[0];
// check for previously validated certificate.
X509Certificate2 certificate2 = null;
if (m_validatedCertificates.TryGetValue(certificate.Thumbprint, out certificate2))
{
if (Utils.IsEqual(certificate2.RawData, certificate.RawData))
{
return;
}
}
CertificateIdentifier trustedCertificate = await GetTrustedCertificate(certificate);
// get the issuers (checks the revocation lists if using directory stores).
List <CertificateIdentifier> issuers = new List <CertificateIdentifier>();
bool isIssuerTrusted = await GetIssuers(certificates, issuers);
// setup policy chain
X509ChainPolicy policy = new X509ChainPolicy();
policy.RevocationFlag = X509RevocationFlag.EntireChain;
policy.RevocationMode = X509RevocationMode.NoCheck;
policy.VerificationFlags = X509VerificationFlags.NoFlag;
foreach (CertificateIdentifier issuer in issuers)
{
if ((issuer.ValidationOptions & CertificateValidationOptions.SuppressRevocationStatusUnknown) != 0)
{
policy.VerificationFlags |= X509VerificationFlags.IgnoreCertificateAuthorityRevocationUnknown;
policy.VerificationFlags |= X509VerificationFlags.IgnoreCtlSignerRevocationUnknown;
policy.VerificationFlags |= X509VerificationFlags.IgnoreEndRevocationUnknown;
policy.VerificationFlags |= X509VerificationFlags.IgnoreRootRevocationUnknown;
}
// we did the revocation check in the GetIssuers call. No need here.
policy.RevocationMode = X509RevocationMode.NoCheck;
policy.ExtraStore.Add(issuer.Certificate);
}
// build chain.
bool chainStatusChecked = false;
X509Chain chain = new X509Chain();
chain.ChainPolicy = policy;
chain.Build(certificate);
// check the chain results.
CertificateIdentifier target = trustedCertificate;
if (target == null)
{
target = new CertificateIdentifier(certificate);
}
for (int ii = 0; ii < chain.ChainElements.Count; ii++)
{
X509ChainElement element = chain.ChainElements[ii];
CertificateIdentifier issuer = null;
if (ii < issuers.Count)
{
issuer = issuers[ii];
}
// check for chain status errors.
foreach (X509ChainStatus status in element.ChainElementStatus)
{
ServiceResult result = CheckChainStatus(status, target, issuer, (ii != 0));
if (ServiceResult.IsBad(result))
{
// check untrusted certificates.
if (trustedCertificate == null)
{
throw new ServiceResultException(StatusCodes.BadSecurityChecksFailed);
}
throw new ServiceResultException(result);
}
chainStatusChecked = true;
}
if (issuer != null)
{
target = issuer;
}
}
// check whether the chain is complete (if there is a chain)
bool issuedByCA = !Utils.CompareDistinguishedName(certificate.Subject, certificate.Issuer);
bool chainIncomplete = false;
if (issuers.Count > 0)
{
var rootCertificate = issuers[issuers.Count - 1].Certificate;
if (!Utils.CompareDistinguishedName(rootCertificate.Subject, rootCertificate.Issuer))
{
chainIncomplete = true;
}
}
else
{
if (issuedByCA)
{
// no issuer found at all
chainIncomplete = true;
}
}
if (issuedByCA && (!chainStatusChecked || chainIncomplete))
{
throw ServiceResultException.Create(
StatusCodes.BadCertificateChainIncomplete,
"Certificate chain validation incomplete.\r\nSubjectName: {0}\r\nIssuerName: {1}",
certificate.SubjectName.Name,
certificate.IssuerName.Name);
}
// check if certificate issuer is trusted.
if (issuedByCA && !isIssuerTrusted && trustedCertificate == null)
{
if (m_applicationCertificate == null || !Utils.IsEqual(m_applicationCertificate.RawData, certificate.RawData))
{
throw ServiceResultException.Create(
StatusCodes.BadCertificateUntrusted,
"Certificate issuer is not trusted.\r\nSubjectName: {0}\r\nIssuerName: {1}",
certificate.SubjectName.Name,
certificate.IssuerName.Name);
}
}
// check if certificate is trusted.
if (trustedCertificate == null && !isIssuerTrusted)
{
if (m_applicationCertificate == null || !Utils.IsEqual(m_applicationCertificate.RawData, certificate.RawData))
{
throw ServiceResultException.Create(
StatusCodes.BadCertificateUntrusted,
"Certificate is not trusted.\r\nSubjectName: {0}\r\nIssuerName: {1}",
certificate.SubjectName.Name,
certificate.IssuerName.Name);
}
}
// check if certificate is valid for use as app/sw or user cert
X509KeyUsageFlags certificateKeyUsage = CertificateFactory.GetKeyUsage(certificate);
if ((certificateKeyUsage & X509KeyUsageFlags.DataEncipherment) == 0)
{
throw new ServiceResultException(StatusCodes.BadCertificateUseNotAllowed, "Usage of certificate is not allowed.");
}
// check if minimum requirements are met
if (m_rejectSHA1SignedCertificates && IsSHA1SignatureAlgorithm(certificate.SignatureAlgorithm))
{
throw new ServiceResultException(StatusCodes.BadCertificatePolicyCheckFailed, "SHA1 signed certificates are not trusted");
}
if (certificate.GetRSAPublicKey().KeySize < m_minimumCertificateKeySize)
{
throw new ServiceResultException(StatusCodes.BadCertificatePolicyCheckFailed, "Certificate doesn't meet minimum key length requirement");
}
}