ValidationResult ValidateChain (string host, bool server, X509Certificate leaf,
X509Chain chain, X509CertificateCollection certs,
SslPolicyErrors errors)
{
var oldChain = chain;
var ownsChain = chain == null;
try {
var result = ValidateChain (host, server, leaf, ref chain, certs, errors);
if (chain != oldChain)
ownsChain = true;
return result;
} finally {
// If ValidateChain() changed the chain, then we need to free it.
if (ownsChain && chain != null)
chain.Dispose ();
}
}
/*++
AcquireCredentials - Attempts to find Client Credential
Information, that can be sent to the server. In our case,
this is only Client Certificates, that we have Credential Info.
How it works:
case 0: Cert Selection delegate is present
Always use its result as the client cert answer.
Try to use cached credential handle whenever feasible.
Do not use cached anonymous creds if the delegate has returned null
and the collection is not empty (allow responding with the cert later).
case 1: Certs collection is empty
Always use the same statically acquired anonymous SSL Credential
case 2: Before our Connection with the Server
If we have a cached credential handle keyed by first X509Certificate
**content** in the passed collection, then we use that cached
credential and hoping to restart a session.
Otherwise create a new anonymous (allow responding with the cert later).
case 3: After our Connection with the Server (i.e. during handshake or re-handshake)
The server has requested that we send it a Certificate then
we Enumerate a list of server sent Issuers trying to match against
our list of Certificates, the first match is sent to the server.
Once we got a cert we again try to match cached credential handle if possible.
This will not restart a session but helps minimizing the number of handles we create.
In the case of an error getting a Certificate or checking its private Key we fall back
to the behavior of having no certs, case 1.
Returns: True if cached creds were used, false otherwise.
--*/
private bool AcquireClientCredentials(ref byte[] thumbPrint)
{
GlobalLog.Enter("SecureChannel#" + Logging.HashString(this) + "::AcquireClientCredentials");
// Acquire possible Client Certificate information and set it on the handle.
X509Certificate clientCertificate = null; // This is a candidate that can come from the user callback or be guessed when targeting a session restart.
ArrayList filteredCerts = new ArrayList(); // This is an intermediate client certs collection that try to use if no selectedCert is available yet.
string[] issuers = null; // This is a list of issuers sent by the server, only valid is we do know what the server cert is.
bool sessionRestartAttempt = false; // If true and no cached creds we will use anonymous creds.
if (_certSelectionDelegate != null)
{
issuers = GetRequestCertificateAuthorities();
GlobalLog.Print("SecureChannel#" + Logging.HashString(this) + "::AcquireClientCredentials() calling CertificateSelectionCallback");
X509Certificate2 remoteCert = null;
try
{
X509Certificate2Collection dummyCollection;
remoteCert = GetRemoteCertificate(out dummyCollection);
clientCertificate = _certSelectionDelegate(_hostName, ClientCertificates, remoteCert, issuers);
}
finally
{
if (remoteCert != null)
{
remoteCert.Dispose();
}
}
if (clientCertificate != null)
{
if (_credentialsHandle == null)
{
sessionRestartAttempt = true;
}
filteredCerts.Add(clientCertificate);
if (Logging.On)
{
Logging.PrintInfo(Logging.Web, this, SR.net_log_got_certificate_from_delegate);
}
}
else
{
if (ClientCertificates.Count == 0)
{
if (Logging.On)
{
Logging.PrintInfo(Logging.Web, this, SR.net_log_no_delegate_and_have_no_client_cert);
}
sessionRestartAttempt = true;
}
else
{
if (Logging.On)
{
Logging.PrintInfo(Logging.Web, this, SR.net_log_no_delegate_but_have_client_cert);
}
}
}
}
else if (_credentialsHandle == null && _clientCertificates != null && _clientCertificates.Count > 0)
{
// This is where we attempt to restart a session by picking the FIRST cert from the collection.
// Otherwise it is either server sending a client cert request or the session is renegotiated.
clientCertificate = ClientCertificates[0];
sessionRestartAttempt = true;
if (clientCertificate != null)
{
filteredCerts.Add(clientCertificate);
}
if (Logging.On)
{
Logging.PrintInfo(Logging.Web, this, SR.Format(SR.net_log_attempting_restart_using_cert, (clientCertificate == null ? "null" : clientCertificate.ToString(true))));
}
}
else if (_clientCertificates != null && _clientCertificates.Count > 0)
{
//
// This should be a server request for the client cert sent over currently anonymous sessions.
//
issuers = GetRequestCertificateAuthorities();
if (Logging.On)
{
if (issuers == null || issuers.Length == 0)
{
Logging.PrintInfo(Logging.Web, this, SR.net_log_no_issuers_try_all_certs);
}
else
{
Logging.PrintInfo(Logging.Web, this, SR.Format(SR.net_log_server_issuers_look_for_matching_certs, issuers.Length));
}
}
for (int i = 0; i < _clientCertificates.Count; ++i)
{
//
// Make sure we add only if the cert matches one of the issuers.
// If no issuers were sent and then try all client certs starting with the first one.
//
if (issuers != null && issuers.Length != 0)
{
X509Certificate2 certificateEx = null;
X509Chain chain = null;
try
{
certificateEx = MakeEx(_clientCertificates[i]);
if (certificateEx == null)
{
continue;
}
GlobalLog.Print("SecureChannel#" + Logging.HashString(this) + "::AcquireClientCredentials() root cert:" + certificateEx.Issuer);
chain = new X509Chain();
chain.ChainPolicy.RevocationMode = X509RevocationMode.NoCheck;
chain.ChainPolicy.VerificationFlags = X509VerificationFlags.IgnoreInvalidName;
chain.Build(certificateEx);
bool found = false;
//
// We ignore any errors happened with chain.
//
if (chain.ChainElements.Count > 0)
{
for (int ii = 0; ii < chain.ChainElements.Count; ++ii)
{
string issuer = chain.ChainElements[ii].Certificate.Issuer;
found = Array.IndexOf(issuers, issuer) != -1;
if (found)
{
GlobalLog.Print("SecureChannel#" + Logging.HashString(this) + "::AcquireClientCredentials() matched:" + issuer);
break;
}
GlobalLog.Print("SecureChannel#" + Logging.HashString(this) + "::AcquireClientCredentials() no match:" + issuer);
}
}
if (!found)
{
continue;
}
}
finally
{
if (chain != null)
{
chain.Dispose();
}
if (certificateEx != null && (object)certificateEx != (object)_clientCertificates[i])
{
certificateEx.Dispose();
}
}
}
if (Logging.On)
{
Logging.PrintInfo(Logging.Web, this, SR.Format(SR.net_log_selected_cert, _clientCertificates[i].ToString(true)));
}
filteredCerts.Add(_clientCertificates[i]);
}
}
bool cachedCred = false; // This is a return result from this method.
X509Certificate2 selectedCert = null; // This is a final selected cert (ensured that it does have private key with it).
clientCertificate = null;
if (Logging.On)
{
Logging.PrintInfo(Logging.Web, this, SR.Format(SR.net_log_n_certs_after_filtering, filteredCerts.Count));
if (filteredCerts.Count != 0)
{
Logging.PrintInfo(Logging.Web, this, SR.net_log_finding_matching_certs);
}
}
//
// ATTN: When the client cert was returned by the user callback OR it was guessed AND it has no private key,
// THEN anonymous (no client cert) credential will be used.
//
// SECURITY: Accessing X509 cert Credential is disabled for semitrust.
// We no longer need to demand for unmanaged code permissions.
// EnsurePrivateKey should do the right demand for us.
for (int i = 0; i < filteredCerts.Count; ++i)
{
clientCertificate = filteredCerts[i] as X509Certificate;
if ((selectedCert = EnsurePrivateKey(clientCertificate)) != null)
{
break;
}
clientCertificate = null;
selectedCert = null;
}
GlobalLog.Assert(((object)clientCertificate == (object)selectedCert) || clientCertificate.Equals(selectedCert), "AcquireClientCredentials()|'selectedCert' does not match 'clientCertificate'.");
GlobalLog.Print("SecureChannel#" + Logging.HashString(this) + "::AcquireClientCredentials() Selected Cert = " + (selectedCert == null ? "null" : selectedCert.Subject));
try
{
// Try to locate cached creds first.
//
// SECURITY: selectedCert ref if not null is a safe object that does not depend on possible **user** inherited X509Certificate type.
//
byte[] guessedThumbPrint = selectedCert == null ? null : selectedCert.GetCertHash();
SafeFreeCredentials cachedCredentialHandle = SslSessionsCache.TryCachedCredential(guessedThumbPrint, _protocolFlags, _encryptionPolicy);
// We can probably do some optimization here. If the selectedCert is returned by the delegate
// we can always go ahead and use the certificate to create our credential
// (instead of going anonymous as we do here).
if (sessionRestartAttempt && cachedCredentialHandle == null && selectedCert != null)
{
GlobalLog.Print("SecureChannel#" + Logging.HashString(this) + "::AcquireClientCredentials() Reset to anonymous session.");
// IIS does not renegotiate a restarted session if client cert is needed.
// So we don't want to reuse **anonymous** cached credential for a new SSL connection if the client has passed some certificate.
// The following block happens if client did specify a certificate but no cached creds were found in the cache.
// Since we don't restart a session the server side can still challenge for a client cert.
if ((object)clientCertificate != (object)selectedCert)
{
selectedCert.Dispose();
}
guessedThumbPrint = null;
selectedCert = null;
clientCertificate = null;
}
if (cachedCredentialHandle != null)
{
if (Logging.On)
{
Logging.PrintInfo(Logging.Web, SR.net_log_using_cached_credential);
}
_credentialsHandle = cachedCredentialHandle;
_selectedClientCertificate = clientCertificate;
cachedCred = true;
}
else
{
Interop.Secur32.SecureCredential.Flags flags = Interop.Secur32.SecureCredential.Flags.ValidateManual | Interop.Secur32.SecureCredential.Flags.NoDefaultCred;
// CoreFX: always opt-in SCH_USE_STRONG_CRYPTO except for SSL3.
if (((_protocolFlags & (Interop.SChannel.SP_PROT_TLS1_0 | Interop.SChannel.SP_PROT_TLS1_1 | Interop.SChannel.SP_PROT_TLS1_2)) != 0)
&& (_encryptionPolicy != EncryptionPolicy.AllowNoEncryption) && (_encryptionPolicy != EncryptionPolicy.NoEncryption))
{
flags |= Interop.Secur32.SecureCredential.Flags.UseStrongCrypto;
}
Interop.Secur32.SecureCredential secureCredential = CreateSecureCredential(
Interop.Secur32.SecureCredential.CurrentVersion,
selectedCert,
flags,
_protocolFlags,
_encryptionPolicy);
_credentialsHandle = AcquireCredentialsHandle(Interop.Secur32.CredentialUse.Outbound, secureCredential);
thumbPrint = guessedThumbPrint; // Delay until here in case something above threw.
_selectedClientCertificate = clientCertificate;
}
}
finally
{
// An extra cert could have been created, dispose it now.
if (selectedCert != null && (object)clientCertificate != (object)selectedCert)
{
selectedCert.Dispose();
}
}
GlobalLog.Leave("SecureChannel#" + Logging.HashString(this) + "::AcquireClientCredentials, cachedCreds = " + cachedCred.ToString(), Logging.ObjectToString(_credentialsHandle));
return cachedCred;
}
/*++
AcquireCredentials - Attempts to find Client Credential
Information, that can be sent to the server. In our case,
this is only Client Certificates, that we have Credential Info.
How it works:
case 0: Cert Selection delegate is present
Always use its result as the client cert answer.
Try to use cached credential handle whenever feasible.
Do not use cached anonymous creds if the delegate has returned null
and the collection is not empty (allow responding with the cert later).
case 1: Certs collection is empty
Always use the same statically acquired anonymous SSL Credential
case 2: Before our Connection with the Server
If we have a cached credential handle keyed by first X509Certificate
**content** in the passed collection, then we use that cached
credential and hoping to restart a session.
Otherwise create a new anonymous (allow responding with the cert later).
case 3: After our Connection with the Server (i.e. during handshake or re-handshake)
The server has requested that we send it a Certificate then
we Enumerate a list of server sent Issuers trying to match against
our list of Certificates, the first match is sent to the server.
Once we got a cert we again try to match cached credential handle if possible.
This will not restart a session but helps minimizing the number of handles we create.
In the case of an error getting a Certificate or checking its private Key we fall back
to the behavior of having no certs, case 1.
Returns: True if cached creds were used, false otherwise.
--*/
private bool AcquireClientCredentials(ref byte[] thumbPrint)
{
if (GlobalLog.IsEnabled)
{
GlobalLog.Enter("SecureChannel#" + LoggingHash.HashString(this) + "::AcquireClientCredentials");
}
// Acquire possible Client Certificate information and set it on the handle.
X509Certificate clientCertificate = null; // This is a candidate that can come from the user callback or be guessed when targeting a session restart.
var filteredCerts = new List<X509Certificate>(); // This is an intermediate client certs collection that try to use if no selectedCert is available yet.
string[] issuers = null; // This is a list of issuers sent by the server, only valid is we do know what the server cert is.
bool sessionRestartAttempt = false; // If true and no cached creds we will use anonymous creds.
if (_certSelectionDelegate != null)
{
issuers = GetRequestCertificateAuthorities();
if (GlobalLog.IsEnabled)
{
GlobalLog.Print("SecureChannel#" + LoggingHash.HashString(this) + "::AcquireClientCredentials() calling CertificateSelectionCallback");
}
X509Certificate2 remoteCert = null;
try
{
X509Certificate2Collection dummyCollection;
remoteCert = CertificateValidationPal.GetRemoteCertificate(_securityContext, out dummyCollection);
clientCertificate = _certSelectionDelegate(_hostName, ClientCertificates, remoteCert, issuers);
}
finally
{
if (remoteCert != null)
{
remoteCert.Dispose();
}
}
if (clientCertificate != null)
{
if (_credentialsHandle == null)
{
sessionRestartAttempt = true;
}
filteredCerts.Add(clientCertificate);
if (SecurityEventSource.Log.IsEnabled())
{
SecurityEventSource.Log.CertificateFromDelegate(LoggingHash.HashInt(this));
}
}
else
{
if (ClientCertificates.Count == 0)
{
if (SecurityEventSource.Log.IsEnabled())
{
SecurityEventSource.Log.NoDelegateNoClientCert(LoggingHash.HashInt(this));
}
sessionRestartAttempt = true;
}
else
{
if (SecurityEventSource.Log.IsEnabled())
{
SecurityEventSource.Log.NoDelegateButClientCert(LoggingHash.HashInt(this));
}
}
}
}
else if (_credentialsHandle == null && _clientCertificates != null && _clientCertificates.Count > 0)
{
// This is where we attempt to restart a session by picking the FIRST cert from the collection.
// Otherwise it is either server sending a client cert request or the session is renegotiated.
clientCertificate = ClientCertificates[0];
sessionRestartAttempt = true;
if (clientCertificate != null)
{
filteredCerts.Add(clientCertificate);
}
if (SecurityEventSource.Log.IsEnabled())
{
SecurityEventSource.Log.AttemptingRestartUsingCert(clientCertificate == null ? "null" : clientCertificate.ToString(true), LoggingHash.HashInt(this));
}
}
else if (_clientCertificates != null && _clientCertificates.Count > 0)
{
//
// This should be a server request for the client cert sent over currently anonymous sessions.
//
issuers = GetRequestCertificateAuthorities();
if (SecurityEventSource.Log.IsEnabled())
{
if (issuers == null || issuers.Length == 0)
{
SecurityEventSource.Log.NoIssuersTryAllCerts(LoggingHash.HashInt(this));
}
else
{
SecurityEventSource.Log.LookForMatchingCerts(issuers.Length, LoggingHash.HashInt(this));
}
}
for (int i = 0; i < _clientCertificates.Count; ++i)
{
//
// Make sure we add only if the cert matches one of the issuers.
// If no issuers were sent and then try all client certs starting with the first one.
//
if (issuers != null && issuers.Length != 0)
{
X509Certificate2 certificateEx = null;
X509Chain chain = null;
try
{
certificateEx = MakeEx(_clientCertificates[i]);
if (certificateEx == null)
{
continue;
}
if (GlobalLog.IsEnabled)
{
GlobalLog.Print("SecureChannel#" + LoggingHash.HashString(this) + "::AcquireClientCredentials() root cert:" + certificateEx.Issuer);
}
chain = new X509Chain();
chain.ChainPolicy.RevocationMode = X509RevocationMode.NoCheck;
chain.ChainPolicy.VerificationFlags = X509VerificationFlags.IgnoreInvalidName;
chain.Build(certificateEx);
bool found = false;
//
// We ignore any errors happened with chain.
//
if (chain.ChainElements.Count > 0)
{
for (int ii = 0; ii < chain.ChainElements.Count; ++ii)
{
string issuer = chain.ChainElements[ii].Certificate.Issuer;
found = Array.IndexOf(issuers, issuer) != -1;
if (found)
{
if (GlobalLog.IsEnabled)
{
GlobalLog.Print("SecureChannel#" + LoggingHash.HashString(this) + "::AcquireClientCredentials() matched:" + issuer);
}
break;
}
if (GlobalLog.IsEnabled)
{
GlobalLog.Print("SecureChannel#" + LoggingHash.HashString(this) + "::AcquireClientCredentials() no match:" + issuer);
}
}
}
if (!found)
{
continue;
}
}
finally
{
if (chain != null)
{
chain.Dispose();
}
if (certificateEx != null && (object)certificateEx != (object)_clientCertificates[i])
{
certificateEx.Dispose();
}
}
}
if (SecurityEventSource.Log.IsEnabled())
{
SecurityEventSource.Log.SelectedCert(_clientCertificates[i].ToString(true), LoggingHash.HashInt(this));
}
filteredCerts.Add(_clientCertificates[i]);
}
}
bool cachedCred = false; // This is a return result from this method.
X509Certificate2 selectedCert = null; // This is a final selected cert (ensured that it does have private key with it).
clientCertificate = null;
if (SecurityEventSource.Log.IsEnabled())
{
SecurityEventSource.Log.CertsAfterFiltering(filteredCerts.Count, LoggingHash.HashInt(this));
if (filteredCerts.Count != 0)
{
SecurityEventSource.Log.FindingMatchingCerts(LoggingHash.HashInt(this));
}
}
//
// ATTN: When the client cert was returned by the user callback OR it was guessed AND it has no private key,
// THEN anonymous (no client cert) credential will be used.
//
// SECURITY: Accessing X509 cert Credential is disabled for semitrust.
// We no longer need to demand for unmanaged code permissions.
// EnsurePrivateKey should do the right demand for us.
for (int i = 0; i < filteredCerts.Count; ++i)
{
clientCertificate = filteredCerts[i];
if ((selectedCert = EnsurePrivateKey(clientCertificate)) != null)
{
break;
}
clientCertificate = null;
selectedCert = null;
}
if ((object)clientCertificate != (object)selectedCert && !clientCertificate.Equals(selectedCert))
{
if (GlobalLog.IsEnabled)
{
GlobalLog.Assert("AcquireClientCredentials()|'selectedCert' does not match 'clientCertificate'.");
}
Debug.Fail("AcquireClientCredentials()|'selectedCert' does not match 'clientCertificate'.");
}
if (GlobalLog.IsEnabled)
{
GlobalLog.Print("SecureChannel#" + LoggingHash.HashString(this) + "::AcquireClientCredentials() Selected Cert = " + (selectedCert == null ? "null" : selectedCert.Subject));
}
try
{
// Try to locate cached creds first.
//
// SECURITY: selectedCert ref if not null is a safe object that does not depend on possible **user** inherited X509Certificate type.
//
byte[] guessedThumbPrint = selectedCert == null ? null : selectedCert.GetCertHash();
SafeFreeCredentials cachedCredentialHandle = SslSessionsCache.TryCachedCredential(guessedThumbPrint, _sslProtocols, _serverMode, _encryptionPolicy);
// We can probably do some optimization here. If the selectedCert is returned by the delegate
// we can always go ahead and use the certificate to create our credential
// (instead of going anonymous as we do here).
if (sessionRestartAttempt &&
cachedCredentialHandle == null &&
selectedCert != null &&
SslStreamPal.StartMutualAuthAsAnonymous)
{
if (GlobalLog.IsEnabled)
{
GlobalLog.Print("SecureChannel#" + LoggingHash.HashString(this) + "::AcquireClientCredentials() Reset to anonymous session.");
}
// IIS does not renegotiate a restarted session if client cert is needed.
// So we don't want to reuse **anonymous** cached credential for a new SSL connection if the client has passed some certificate.
// The following block happens if client did specify a certificate but no cached creds were found in the cache.
// Since we don't restart a session the server side can still challenge for a client cert.
if ((object)clientCertificate != (object)selectedCert)
{
selectedCert.Dispose();
}
guessedThumbPrint = null;
selectedCert = null;
clientCertificate = null;
}
if (cachedCredentialHandle != null)
{
if (SecurityEventSource.Log.IsEnabled())
{
SecurityEventSource.Log.UsingCachedCredential(LoggingHash.HashInt(this));
}
_credentialsHandle = cachedCredentialHandle;
_selectedClientCertificate = clientCertificate;
cachedCred = true;
}
else
{
_credentialsHandle = SslStreamPal.AcquireCredentialsHandle(selectedCert, _sslProtocols, _encryptionPolicy, _serverMode);
thumbPrint = guessedThumbPrint; // Delay until here in case something above threw.
_selectedClientCertificate = clientCertificate;
}
}
finally
{
// An extra cert could have been created, dispose it now.
if (selectedCert != null && (object)clientCertificate != (object)selectedCert)
{
selectedCert.Dispose();
}
}
if (GlobalLog.IsEnabled)
{
GlobalLog.Leave("SecureChannel#" + LoggingHash.HashString(this) + "::AcquireClientCredentials, cachedCreds = " + cachedCred.ToString(), LoggingHash.ObjectToString(_credentialsHandle));
}
return cachedCred;
}
internal static X509Chain BuildNewChain(X509Certificate2 certificate, bool includeClientApplicationPolicy)
{
var chain = new X509Chain();
chain.ChainPolicy.VerificationFlags = X509VerificationFlags.AllFlags;
chain.ChainPolicy.RevocationFlag = X509RevocationFlag.ExcludeRoot;
if (includeClientApplicationPolicy)
{
chain.ChainPolicy.ApplicationPolicy.Add(s_clientCertOidInst);
}
if (chain.Build(certificate))
{
return chain;
}
else
{
chain.Dispose();
return null;
}
}
