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[release/8.0] Fix server-side OCSP stapling on Linux (#96838)
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* Add entire issuer chain to trusted X509_STORE when stapling OCSP_Response (#96792)

* Add entire issuer chain to trusted X509_STORE when validating OCSP_Response

* Code review feedback

* More code review feedback

* Update src/libraries/System.Net.Security/src/System/Net/Security/SslStreamCertificateContext.Linux.cs

Co-authored-by: Jeremy Barton <jbarton@microsoft.com>

* Fix compilation

* Always include root certificate

---------

Co-authored-by: Jeremy Barton <jbarton@microsoft.com>

* Recover from failed OCSP download. (#96448)

* Recover from failed OCSP check.

* Add 5s back-off after failed OCSP querry

* Don't shorten OCSP expriation on failed server OCSP fetch (#96972)

* Don't shorten OCSP expriation on failed server OCSP fetch

* Code review feedback

---------

Co-authored-by: Jeremy Barton <jbarton@microsoft.com>
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@rzikm @bartonjs
rzikm and bartonjs authored Jan 16, 2024
1 parent 683da71 commit 85c2772
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Showing 4 changed files with 65 additions and 22 deletions.
9 changes: 6 additions & 3 deletions src/libraries/Common/src/Interop/Unix/System.Security.Cryptography.Native/Interop.OCSP.cs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -29,27 +29,30 @@ private static unsafe partial int CryptoNative_X509DecodeOcspToExpiration(
int len,
SafeOcspRequestHandle req,
IntPtr subject,
IntPtr issuer,
IntPtr* issuers,
int issuersLen,
ref long expiration);

internal static unsafe bool X509DecodeOcspToExpiration(
ReadOnlySpan<byte> buf,
SafeOcspRequestHandle request,
IntPtr x509Subject,
IntPtr x509Issuer,
ReadOnlySpan<IntPtr> x509Issuers,
out DateTimeOffset expiration)
{
long timeT = 0;
int ret;

fixed (byte* pBuf = buf)
fixed (IntPtr* pIssuers = x509Issuers)
{
ret = CryptoNative_X509DecodeOcspToExpiration(
pBuf,
buf.Length,
request,
x509Subject,
x509Issuer,
pIssuers,
x509Issuers.Length,
ref timeT);
}

Expand Down
59 changes: 45 additions & 14 deletions ...ibraries/System.Net.Security/src/System/Net/Security/SslStreamCertificateContext.Linux.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,13 +26,30 @@ public partial class SslStreamCertificateContext
private byte[]? _ocspResponse;
private DateTimeOffset _ocspExpiration;
private DateTimeOffset _nextDownload;
// Private copy of the intermediate certificates, in case the user decides to dispose the
// instances reachable through IntermediateCertificates property.
private X509Certificate2[] _privateIntermediateCertificates;
private X509Certificate2? _rootCertificate;
private Task<byte[]?>? _pendingDownload;
private List<string>? _ocspUrls;
private X509Certificate2? _ca;

private SslStreamCertificateContext(X509Certificate2 target, ReadOnlyCollection<X509Certificate2> intermediates, SslCertificateTrust? trust)
{
IntermediateCertificates = intermediates;
if (intermediates.Count > 0)
{
_privateIntermediateCertificates = new X509Certificate2[intermediates.Count];

for (int i = 0; i < intermediates.Count; i++)
{
_privateIntermediateCertificates[i] = new X509Certificate2(intermediates[i]);
}
}
else
{
_privateIntermediateCertificates = Array.Empty<X509Certificate2>();
}

TargetCertificate = target;
Trust = trust;
SslContexts = new ConcurrentDictionary<SslProtocols, SafeSslContextHandle>();
Expand Down Expand Up @@ -76,15 +93,8 @@ partial void SetNoOcspFetch(bool noOcspFetch)

partial void AddRootCertificate(X509Certificate2? rootCertificate, ref bool transferredOwnership)
{
if (IntermediateCertificates.Count == 0)
{
_ca = rootCertificate;
transferredOwnership = true;
}
else
{
_ca = IntermediateCertificates[0];
}
_rootCertificate = rootCertificate;
transferredOwnership = rootCertificate != null;

if (!_staplingForbidden)
{
Expand Down Expand Up @@ -149,7 +159,7 @@ partial void AddRootCertificate(X509Certificate2? rootCertificate, ref bool tran
return new ValueTask<byte[]?>(pending);
}

if (_ocspUrls is null && _ca is not null)
if (_ocspUrls is null && _rootCertificate is not null)
{
foreach (X509Extension ext in TargetCertificate.Extensions)
{
Expand Down Expand Up @@ -192,7 +202,9 @@ partial void AddRootCertificate(X509Certificate2? rootCertificate, ref bool tran

private async Task<byte[]?> FetchOcspAsync()
{
X509Certificate2? caCert = _ca;
Debug.Assert(_rootCertificate != null);
X509Certificate2? caCert = _privateIntermediateCertificates.Length > 0 ? _privateIntermediateCertificates[0] : _rootCertificate;

Debug.Assert(_ocspUrls is not null);
Debug.Assert(_ocspUrls.Count > 0);
Debug.Assert(caCert is not null);
Expand All @@ -211,6 +223,13 @@ partial void AddRootCertificate(X509Certificate2? rootCertificate, ref bool tran
return null;
}

IntPtr[] issuerHandles = ArrayPool<IntPtr>.Shared.Rent(_privateIntermediateCertificates.Length + 1);
for (int i = 0; i < _privateIntermediateCertificates.Length; i++)
{
issuerHandles[i] = _privateIntermediateCertificates[i].Handle;
}
issuerHandles[_privateIntermediateCertificates.Length] = _rootCertificate.Handle;

using (SafeOcspRequestHandle ocspRequest = Interop.Crypto.X509BuildOcspRequest(subject, issuer))
{
byte[] rentedBytes = ArrayPool<byte>.Shared.Rent(Interop.Crypto.GetOcspRequestDerSize(ocspRequest));
Expand All @@ -227,7 +246,7 @@ partial void AddRootCertificate(X509Certificate2? rootCertificate, ref bool tran

if (ret is not null)
{
if (!Interop.Crypto.X509DecodeOcspToExpiration(ret, ocspRequest, subject, issuer, out DateTimeOffset expiration))
if (!Interop.Crypto.X509DecodeOcspToExpiration(ret, ocspRequest, subject, issuerHandles.AsSpan(0, _privateIntermediateCertificates.Length + 1), out DateTimeOffset expiration))
{
ret = null;
continue;
Expand All @@ -247,15 +266,27 @@ partial void AddRootCertificate(X509Certificate2? rootCertificate, ref bool tran
_ocspResponse = ret;
_ocspExpiration = expiration;
_nextDownload = nextCheckA < nextCheckB ? nextCheckA : nextCheckB;
_pendingDownload = null;
break;
}
}

issuerHandles.AsSpan().Clear();
ArrayPool<IntPtr>.Shared.Return(issuerHandles);
ArrayPool<byte>.Shared.Return(rentedBytes);
ArrayPool<char>.Shared.Return(rentedChars.Array!);
GC.KeepAlive(TargetCertificate);
GC.KeepAlive(_privateIntermediateCertificates);
GC.KeepAlive(_rootCertificate);
GC.KeepAlive(caCert);

_pendingDownload = null;
if (ret == null)
{
// All download attempts failed, don't try again for 5 seconds.
// This backoff will be applied only if the OCSP staple is not expired.
// If it is expired, we will force-refresh it during next GetOcspResponseAsync call.
_nextDownload = DateTimeOffset.UtcNow.AddSeconds(5);
}
return ret;
}
}
Expand Down
17 changes: 13 additions & 4 deletions src/native/libs/System.Security.Cryptography.Native/pal_x509.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1302,11 +1302,11 @@ CryptoNative_X509ChainVerifyOcsp(X509_STORE_CTX* storeCtx, OCSP_REQUEST* req, OC
return X509ChainVerifyOcsp(storeCtx, subject, issuer, req, resp, cachePath);
}

int32_t CryptoNative_X509DecodeOcspToExpiration(const uint8_t* buf, int32_t len, OCSP_REQUEST* req, X509* subject, X509* issuer, int64_t* expiration)
int32_t CryptoNative_X509DecodeOcspToExpiration(const uint8_t* buf, int32_t len, OCSP_REQUEST* req, X509* subject, X509** issuers, int issuersLen, int64_t* expiration)
{
ERR_clear_error();

if (buf == NULL || len == 0)
if (buf == NULL || len == 0 || issuersLen == 0)
{
return 0;
}
Expand All @@ -1329,7 +1329,16 @@ int32_t CryptoNative_X509DecodeOcspToExpiration(const uint8_t* buf, int32_t len,

if (bag != NULL)
{
if (X509_STORE_add_cert(store, issuer) && sk_X509_push(bag, issuer))
int i;
for (i = 0; i < issuersLen; i++)
{
if (!X509_STORE_add_cert(store, issuers[i]) || !sk_X509_push(bag, issuers[i]))
{
break;
}
}

if (i == issuersLen)
{
ctx = X509_STORE_CTX_new();
}
Expand All @@ -1343,7 +1352,7 @@ int32_t CryptoNative_X509DecodeOcspToExpiration(const uint8_t* buf, int32_t len,
{
int canCache = 0;
time_t expiration_t = 0;
X509VerifyStatusCode code = CheckOcspGetExpiry(req, resp, subject, issuer, ctx, &canCache, &expiration_t);
X509VerifyStatusCode code = CheckOcspGetExpiry(req, resp, subject, issuers[0], ctx, &canCache, &expiration_t);

if (sizeof(time_t) == sizeof(int64_t))
{
Expand Down
2 changes: 1 addition & 1 deletion src/native/libs/System.Security.Cryptography.Native/pal_x509.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -412,4 +412,4 @@ PALEXPORT int32_t CryptoNative_X509ChainVerifyOcsp(X509_STORE_CTX* storeCtx,
Decode len bytes of buf into an OCSP response, process it against the OCSP request, and return if the bytes were valid.
If the bytes were valid, and the OCSP response had a nextUpdate value, assign it to expiration.
*/
PALEXPORT int32_t CryptoNative_X509DecodeOcspToExpiration(const uint8_t* buf, int32_t len, OCSP_REQUEST* req, X509* subject, X509* issuer, int64_t* expiration);
PALEXPORT int32_t CryptoNative_X509DecodeOcspToExpiration(const uint8_t* buf, int32_t len, OCSP_REQUEST* req, X509* subject, X509** issuers, int issuersLen, int64_t* expiration);

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