private PkixCertPathBuilderResult Build(
IX509AttributeCertificate attrCert,
X509Certificate tbvCert,
PkixBuilderParameters pkixParams,
IList tbvPath)
{
// If tbvCert is readily present in tbvPath, it indicates having run
// into a cycle in the
// PKI graph.
if (tbvPath.Contains(tbvCert))
{
return(null);
}
// step out, the certificate is not allowed to appear in a certification
// chain
if (pkixParams.GetExcludedCerts().Contains(tbvCert))
{
return(null);
}
// test if certificate path exceeds maximum length
if (pkixParams.MaxPathLength != -1)
{
if (tbvPath.Count - 1 > pkixParams.MaxPathLength)
{
return(null);
}
}
tbvPath.Add(tbvCert);
PkixCertPathBuilderResult builderResult = null;
// X509CertificateParser certParser = new X509CertificateParser();
PkixAttrCertPathValidator validator = new PkixAttrCertPathValidator();
try
{
// check whether the issuer of <tbvCert> is a TrustAnchor
if (PkixCertPathValidatorUtilities.FindTrustAnchor(tbvCert, pkixParams.GetTrustAnchors()) != null)
{
PkixCertPath certPath = new PkixCertPath(tbvPath);
PkixCertPathValidatorResult result;
try
{
result = validator.Validate(certPath, pkixParams);
}
catch (Exception e)
{
throw new Exception("Certification path could not be validated.", e);
}
return(new PkixCertPathBuilderResult(certPath, result.TrustAnchor,
result.PolicyTree, result.SubjectPublicKey));
}
else
{
// add additional X.509 stores from locations in certificate
try
{
PkixCertPathValidatorUtilities.AddAdditionalStoresFromAltNames(tbvCert, pkixParams);
}
catch (CertificateParsingException e)
{
throw new Exception("No additional X.509 stores can be added from certificate locations.", e);
}
// try to get the issuer certificate from one of the stores
ISet issuers = new HashSet();
try
{
issuers.AddAll(PkixCertPathValidatorUtilities.FindIssuerCerts(tbvCert, pkixParams));
}
catch (Exception e)
{
throw new Exception("Cannot find issuer certificate for certificate in certification path.", e);
}
if (issuers.IsEmpty)
{
throw new Exception("No issuer certificate for certificate in certification path found.");
}
foreach (X509Certificate issuer in issuers)
{
// if untrusted self signed certificate continue
if (PkixCertPathValidatorUtilities.IsSelfIssued(issuer))
{
continue;
}
builderResult = Build(attrCert, issuer, pkixParams, tbvPath);
if (builderResult != null)
{
break;
}
}
}
}
catch (Exception e)
{
certPathException = new Exception("No valid certification path could be build.", e);
}
if (builderResult == null)
{
tbvPath.Remove(tbvCert);
}
return(builderResult);
}