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//------------------------------------------------------------
// Copyright (c) Microsoft Corporation. All rights reserved.
//------------------------------------------------------------
namespace System.IdentityModel.Selectors
{
using System.Collections.Generic;
using System.IdentityModel.Tokens;
using System.Net;
using System.Runtime;
using System.Runtime.InteropServices;
using System.Security;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Security.Permissions;
using System.Text;
using FILETIME = System.Runtime.InteropServices.ComTypes.FILETIME;
// Most of codes are copied from \ndp\fx\src\security\system\security\cryptography\x509\X509Chain.cs
class X509CertificateChain
{
public const uint DefaultChainPolicyOID = CAPI.CERT_CHAIN_POLICY_BASE;
bool useMachineContext;
X509ChainPolicy chainPolicy;
uint chainPolicyOID = X509CertificateChain.DefaultChainPolicyOID;
public X509CertificateChain()
: this(false)
{
}
public X509CertificateChain(bool useMachineContext)
{
this.useMachineContext = useMachineContext;
}
public X509CertificateChain(bool useMachineContext, uint chainPolicyOID)
{
this.useMachineContext = useMachineContext;
// One of the condition to pass NT_AUTH is the issuer of the cert must be trusted by NT auth.
// Simply add to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\EnterpriseCertificates\NTAuth\Certificates
this.chainPolicyOID = chainPolicyOID;
}
public X509ChainPolicy ChainPolicy
{
get
{
if (this.chainPolicy == null)
{
this.chainPolicy = new X509ChainPolicy();
}
return this.chainPolicy;
}
set
{
this.chainPolicy = value;
}
}
public X509ChainStatus[] ChainStatus
{
#pragma warning suppress 56503
get { throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new NotSupportedException()); }
}
// There are 2 steps in chain validation.
// 1) BuildChain by calling CAPI.CertGetCertificateChain. The result is
// the chain context containing the chain and status.
// 2) VerifyChain by calling CAPI.CertVerifyCertificateChainPolicy.
// Refer to MB50916, Since Vista out-of-the-box will trust the chain with PeerTrust,
// we include the flag to ignore PeerTrust for CAPI.CertVerifyCertificateChainPolicy.
[Fx.Tag.SecurityNote(Critical = "Builds chain trust through interop calls.",
Safe = "Proteced by StorePermission and WebPermission demands.")]
[SecuritySafeCritical]
[StorePermission(SecurityAction.Demand, CreateStore = true, OpenStore = true, EnumerateCertificates = true)]
public bool Build(X509Certificate2 certificate)
{
if (certificate == null)
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull("certificate");
if (certificate.Handle == IntPtr.Zero)
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgument("certificate", SR.GetString(SR.ArgumentInvalidCertificate));
SafeCertChainHandle safeCertChainHandle = SafeCertChainHandle.InvalidHandle;
X509ChainPolicy chainPolicy = this.ChainPolicy;
chainPolicy.VerificationTime = DateTime.Now;
if (chainPolicy.RevocationMode == X509RevocationMode.Online)
{
if (certificate.Extensions[CAPI.szOID_CRL_DIST_POINTS] != null ||
certificate.Extensions[CAPI.szOID_AUTHORITY_INFO_ACCESS] != null)
{
// If there is a CDP or AIA extension, we demand unrestricted network access and store add permission
// since CAPI can download certificates into the CA store from the network.
PermissionSet ps = new PermissionSet(PermissionState.None);
ps.AddPermission(new WebPermission(PermissionState.Unrestricted));
ps.AddPermission(new StorePermission(StorePermissionFlags.AddToStore));
ps.Demand();
}
}
BuildChain(this.useMachineContext ? new IntPtr(CAPI.HCCE_LOCAL_MACHINE) : new IntPtr(CAPI.HCCE_CURRENT_USER),
certificate.Handle,
chainPolicy.ExtraStore,
chainPolicy.ApplicationPolicy,
chainPolicy.CertificatePolicy,
chainPolicy.RevocationMode,
chainPolicy.RevocationFlag,
chainPolicy.VerificationTime,
chainPolicy.UrlRetrievalTimeout,
out safeCertChainHandle);
// Verify the chain using the specified policy.
CAPI.CERT_CHAIN_POLICY_PARA PolicyPara = new CAPI.CERT_CHAIN_POLICY_PARA(Marshal.SizeOf(typeof(CAPI.CERT_CHAIN_POLICY_PARA)));
CAPI.CERT_CHAIN_POLICY_STATUS PolicyStatus = new CAPI.CERT_CHAIN_POLICY_STATUS(Marshal.SizeOf(typeof(CAPI.CERT_CHAIN_POLICY_STATUS)));
// Ignore peertrust. Peer trust caused the chain to succeed out-of-the-box in Vista.
// This new flag is only available in Vista.
PolicyPara.dwFlags = (uint)chainPolicy.VerificationFlags | CAPI.CERT_CHAIN_POLICY_IGNORE_PEER_TRUST_FLAG;
if (!CAPI.CertVerifyCertificateChainPolicy(new IntPtr(this.chainPolicyOID),
safeCertChainHandle,
ref PolicyPara,
ref PolicyStatus))
{
int error = Marshal.GetLastWin32Error();
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new CryptographicException(error));
}
if (PolicyStatus.dwError != CAPI.S_OK)
{
int error = (int)PolicyStatus.dwError;
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new SecurityTokenValidationException(SR.GetString(SR.X509ChainBuildFail,
SecurityUtils.GetCertificateId(certificate), new CryptographicException(error).Message)));
}
return true;
}
[SecurityCritical]
static unsafe void BuildChain(IntPtr hChainEngine,
IntPtr pCertContext,
X509Certificate2Collection extraStore,
OidCollection applicationPolicy,
OidCollection certificatePolicy,
X509RevocationMode revocationMode,
X509RevocationFlag revocationFlag,
DateTime verificationTime,
TimeSpan timeout,
out SafeCertChainHandle ppChainContext)
{
SafeCertStoreHandle hCertStore = ExportToMemoryStore(extraStore, pCertContext);
CAPI.CERT_CHAIN_PARA ChainPara = new CAPI.CERT_CHAIN_PARA();
ChainPara.cbSize = (uint)Marshal.SizeOf(typeof(CAPI.CERT_CHAIN_PARA));
// Application policy
SafeHGlobalHandle applicationPolicyHandle = SafeHGlobalHandle.InvalidHandle;
SafeHGlobalHandle certificatePolicyHandle = SafeHGlobalHandle.InvalidHandle;
try
{
if (applicationPolicy != null && applicationPolicy.Count > 0)
{
ChainPara.RequestedUsage.dwType = CAPI.USAGE_MATCH_TYPE_AND;
ChainPara.RequestedUsage.Usage.cUsageIdentifier = (uint)applicationPolicy.Count;
applicationPolicyHandle = CopyOidsToUnmanagedMemory(applicationPolicy);
ChainPara.RequestedUsage.Usage.rgpszUsageIdentifier = applicationPolicyHandle.DangerousGetHandle();
}
// Certificate policy
if (certificatePolicy != null && certificatePolicy.Count > 0)
{
ChainPara.RequestedIssuancePolicy.dwType = CAPI.USAGE_MATCH_TYPE_AND;
ChainPara.RequestedIssuancePolicy.Usage.cUsageIdentifier = (uint)certificatePolicy.Count;
certificatePolicyHandle = CopyOidsToUnmanagedMemory(certificatePolicy);
ChainPara.RequestedIssuancePolicy.Usage.rgpszUsageIdentifier = certificatePolicyHandle.DangerousGetHandle();
}
ChainPara.dwUrlRetrievalTimeout = (uint)timeout.Milliseconds;
FILETIME ft = new FILETIME();
*((long*)&ft) = verificationTime.ToFileTime();
uint flags = MapRevocationFlags(revocationMode, revocationFlag);
// Build the chain.
if (!CAPI.CertGetCertificateChain(hChainEngine,
pCertContext,
ref ft,
hCertStore,
ref ChainPara,
flags,
IntPtr.Zero,
out ppChainContext))
{
int error = Marshal.GetLastWin32Error();
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new CryptographicException(error));
}
}
finally
{
if (applicationPolicyHandle != null)
applicationPolicyHandle.Dispose();
if (certificatePolicyHandle != null)
certificatePolicyHandle.Dispose();
hCertStore.Close();
}
}
[Fx.Tag.SecurityNote(Critical = "Uses unmanaged code to create an in memory store which links to the original cert store."
+ "User must protect the store handle.")]
[SecurityCritical]
static SafeCertStoreHandle ExportToMemoryStore(X509Certificate2Collection collection, IntPtr pCertContext)
{
CAPI.CERT_CONTEXT certContext = (CAPI.CERT_CONTEXT)Marshal.PtrToStructure(pCertContext, typeof(CAPI.CERT_CONTEXT));
// No extra store nor intermediate certificates
if ((collection == null || collection.Count <= 0) && certContext.hCertStore == IntPtr.Zero)
{
return SafeCertStoreHandle.InvalidHandle;
}
// we always want to use CERT_STORE_ENUM_ARCHIVED_FLAG since we want to preserve the collection in this operation.
// By default, Archived certificates will not be included.
SafeCertStoreHandle certStoreHandle = CAPI.CertOpenStore(
new IntPtr(CAPI.CERT_STORE_PROV_MEMORY),
CAPI.X509_ASN_ENCODING | CAPI.PKCS_7_ASN_ENCODING,
IntPtr.Zero,
CAPI.CERT_STORE_ENUM_ARCHIVED_FLAG | CAPI.CERT_STORE_CREATE_NEW_FLAG,
null);
if (certStoreHandle == null || certStoreHandle.IsInvalid)
{
int error = Marshal.GetLastWin32Error();
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new CryptographicException(error));
}
//
// We use CertAddCertificateLinkToStore to keep a link to the original store, so any property changes get
// applied to the original store. This has a limit of 99 links per cert context however.
//
// Add extra store
if (collection != null && collection.Count > 0)
{
foreach (X509Certificate2 x509 in collection)
{
if (!CAPI.CertAddCertificateLinkToStore(certStoreHandle,
x509.Handle,
CAPI.CERT_STORE_ADD_ALWAYS,
SafeCertContextHandle.InvalidHandle))
{
int error = Marshal.GetLastWin32Error();
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new CryptographicException(error));
}
}
}
// Add intermediates
// The hCertStore needs to be acquired from an X509Certificate2 object
// constructed using a fresh cert context handle. If we simply refer to the hCertStore
// property of the certContext local variable directly, there is a risk that we are accessing
// a closed store. This is because if the X509Certificate2(rawdata) constructor closes the store handle (hCertStore).
// There is no way to know which constructor was used at this point.
//
using ( SafeCertContextHandle safeCertContext
= CAPI.CertCreateCertificateContext( certContext.dwCertEncodingType,
certContext.pbCertEncoded,
certContext.cbCertEncoded ) )
{
//
// Create an X509Certificate2 using the new cert context that dup's the provided certificate.
//
X509Certificate2 intermediatesCert = new X509Certificate2( safeCertContext.DangerousGetHandle() );
//
// Dereference the handle to this intermediate cert and use it to access the handle
// of this certificate's cert store. Then, call CAPI.CertAddCertificateLinkToStore
// on each cert in this store by wrapping this cert store handle with an X509Store
// object.
//
CAPI.CERT_CONTEXT intermediatesCertContext = (CAPI.CERT_CONTEXT) Marshal.PtrToStructure( intermediatesCert.Handle, typeof( CAPI.CERT_CONTEXT ) );
if (intermediatesCertContext.hCertStore != IntPtr.Zero)
{
X509Certificate2Collection intermediates = null;
X509Store store = new X509Store(intermediatesCertContext.hCertStore);
try
{
intermediates = store.Certificates;
foreach (X509Certificate2 x509 in intermediates)
{
if (!CAPI.CertAddCertificateLinkToStore(certStoreHandle,
x509.Handle,
CAPI.CERT_STORE_ADD_ALWAYS,
SafeCertContextHandle.InvalidHandle))
{
int error = Marshal.GetLastWin32Error();
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new CryptographicException(error));
}
}
}
finally
{
SecurityUtils.ResetAllCertificates(intermediates);
store.Close();
}
}
}
return certStoreHandle;
}
[Fx.Tag.SecurityNote(Critical = "Copies the oid collection to unamanged memory."
+ "User must protect the handle.")]
[SecurityCritical]
static SafeHGlobalHandle CopyOidsToUnmanagedMemory(OidCollection oids)
{
SafeHGlobalHandle safeAllocHandle = SafeHGlobalHandle.InvalidHandle;
if (oids == null || oids.Count == 0)
return safeAllocHandle;
// Copy the oid strings to a local list to prevent a security race condition where
// the OidCollection or individual oids can be modified by another thread and
// potentially cause a buffer overflow
List<string> oidStrs = new List<string>();
foreach (Oid oid in oids) {
oidStrs.Add(oid.Value);
}
IntPtr pOid = IntPtr.Zero;
IntPtr pNullTerminator = IntPtr.Zero;
// Needs to be checked to avoid having large sets of oids overflow the sizes and allow
// a potential buffer overflow
checked {
int ptrSize = oidStrs.Count * Marshal.SizeOf(typeof(IntPtr));
int oidSize = 0;
foreach (string oidStr in oidStrs) {
oidSize += (oidStr.Length + 1);
}
safeAllocHandle = SafeHGlobalHandle.AllocHGlobal(ptrSize + oidSize);
pOid = new IntPtr((long)safeAllocHandle.DangerousGetHandle() + ptrSize);
}
for (int index = 0; index < oidStrs.Count; index++) {
Marshal.WriteIntPtr(new IntPtr((long) safeAllocHandle.DangerousGetHandle() + index * Marshal.SizeOf(typeof(IntPtr))), pOid);
byte[] ansiOid = Encoding.ASCII.GetBytes(oidStrs[index]);
if (ansiOid.Length != oidStrs[index].Length) {
// We assumed single byte characters, fail if this is not the case. The exception is not ideal.
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new InvalidOperationException(SR.GetString(SR.CollectionWasModified)));
}
Marshal.Copy(ansiOid, 0, pOid, ansiOid.Length);
pNullTerminator = new IntPtr((long) pOid + ansiOid.Length);
Marshal.WriteByte(pNullTerminator, 0);
pOid = new IntPtr((long)pOid + oidStrs[index].Length + 1);
}
return safeAllocHandle;
}
static uint MapRevocationFlags(X509RevocationMode revocationMode, X509RevocationFlag revocationFlag)
{
uint dwFlags = 0;
if (revocationMode == X509RevocationMode.NoCheck)
return dwFlags;
if (revocationMode == X509RevocationMode.Offline)
dwFlags |= CAPI.CERT_CHAIN_REVOCATION_CHECK_CACHE_ONLY;
if (revocationFlag == X509RevocationFlag.EndCertificateOnly)
dwFlags |= CAPI.CERT_CHAIN_REVOCATION_CHECK_END_CERT;
else if (revocationFlag == X509RevocationFlag.EntireChain)
dwFlags |= CAPI.CERT_CHAIN_REVOCATION_CHECK_CHAIN;
else
dwFlags |= CAPI.CERT_CHAIN_REVOCATION_CHECK_CHAIN_EXCLUDE_ROOT;
return dwFlags;
}
}
}
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