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[release/6.0] add support for parsing Unified TLS hello #68425

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Merged
carlossanlop merged 3 commits into from
May 4, 2022
Merged

[release/6.0] add support for parsing Unified TLS hello #68425

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237c7df
add support for parsing Unified TLS hello
wfurt Apr 22, 2022
eb357e9
feedback from review
wfurt Apr 27, 2022
ee4f8cc
update comment
wfurt Apr 27, 2022
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11 changes: 8 additions & 3 deletions src/libraries/System.Net.Security/src/System/Net/Security/SslStream.Implementation.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,8 @@ private enum Framing
private const int FrameOverhead = 64;
private const int ReadBufferSize = 4096 * 4 + FrameOverhead; // We read in 16K chunks + headers.
private const int InitialHandshakeBufferSize = 4096 + FrameOverhead; // try to fit at least 4K ServerCertificate
private const int HandshakeTypeOffsetSsl2 = 2; // Offset of HelloType in Sslv2 and Unified frames
private const int HandshakeTypeOffsetTls = 5; // Offset of HelloType in Sslv3 and TLS frames
private ArrayBuffer _handshakeBuffer;
private bool _receivedEOF;

Expand Down Expand Up @@ -475,6 +477,7 @@ private async ValueTask<ProtocolToken> ReceiveBlobAsync<TIOAdapter>(TIOAdapter a
#pragma warning disable 0618
_lastFrame.Header.Version = SslProtocols.Ssl2;
#pragma warning restore 0618
_lastFrame.Header.Type = TlsContentType.Handshake; // Implied. We only call this during handshake and SSL2 does not have framing layer.
_lastFrame.Header.Length = GetFrameSize(_handshakeBuffer.ActiveReadOnlySpan) - TlsFrameHelper.HeaderSize;
}
else
Expand Down Expand Up @@ -506,9 +509,11 @@ private async ValueTask<ProtocolToken> ReceiveBlobAsync<TIOAdapter>(TIOAdapter a
}
break;
case TlsContentType.Handshake:
if (!_isRenego && _handshakeBuffer.ActiveReadOnlySpan[TlsFrameHelper.HeaderSize] == (byte)TlsHandshakeType.ClientHello &&
(_sslAuthenticationOptions!.ServerCertSelectionDelegate != null ||
_sslAuthenticationOptions!.ServerOptionDelegate != null))
byte handshakeType = _handshakeBuffer.ActiveReadOnlySpan[_framing == Framing.SinceSSL3 ? HandshakeTypeOffsetTls : HandshakeTypeOffsetSsl2];

if (!_isRenego &&
(_sslAuthenticationOptions!.ServerCertSelectionDelegate != null || _sslAuthenticationOptions!.ServerOptionDelegate != null) &&
(handshakeType == (byte)TlsHandshakeType.ClientHello))
{
TlsFrameHelper.ProcessingOptions options = NetEventSource.Log.IsEnabled() ?
TlsFrameHelper.ProcessingOptions.All :
Expand Down
70 changes: 45 additions & 25 deletions src/libraries/System.Net.Security/src/System/Net/Security/TlsFrameHelper.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -173,33 +173,41 @@ public override string ToString()

public static bool TryGetFrameHeader(ReadOnlySpan<byte> frame, ref TlsFrameHeader header)
{
bool result = frame.Length > 4;

if (frame.Length >= 1)
header.Type = (TlsContentType)(frame.Length >= 1 ? frame[0] : 0);
if (frame.Length < TlsFrameHelper.HeaderSize)
{
header.Type = (TlsContentType)frame[0];

if (frame.Length >= 3)
{
// SSLv3, TLS or later
if (frame[1] == 3)
{
if (frame.Length > 4)
{
header.Length = ((frame[3] << 8) | frame[4]);
}
header.Length = -1;
header.Version = SslProtocols.None;
return false;
}

header.Version = TlsMinorVersionToProtocol(frame[2]);
}
else
{
header.Length = -1;
header.Version = SslProtocols.None;
}
}
// SSLv3, TLS or later
if (frame[1] == ProtocolVersionTlsMajorValue)
{
header.Length = ((frame[3] << 8) | frame[4]);
header.Version = TlsMinorVersionToProtocol(frame[2]);
}
// Sslv2 or Unified
else if (frame[2] == (byte)TlsHandshakeType.ClientHello &&
frame[3] == ProtocolVersionTlsMajorValue) // SSL3 or above
{
header.Length = (frame[0] & 0x80) != 0 ?
(((frame[0] & 0x7f) << 8) | frame[1]) + 2 : // two bytes
(((frame[0] & 0x3f) << 8) | frame[1]) + 3; // three bytes
#pragma warning disable CS0618 // Ssl2 and Ssl3 are obsolete
header.Version = SslProtocols.Ssl2;
#pragma warning restore CS0618
header.Type = TlsContentType.Handshake;
}
else
{
// neither looks like TLS nor Ssl2 Hello
header.Length = -1;
header.Version = SslProtocols.None;
return false;
}

return result;
return true;
}

// Returns frame size e.g. header + content
Expand Down Expand Up @@ -252,6 +260,18 @@ public static bool TryGetFrameInfo(ReadOnlySpan<byte> frame, ref TlsFrameInfo in
}

info.HandshakeType = (TlsHandshakeType)frame[HandshakeTypeOffset];
#pragma warning disable CS0618 // Ssl2 and Ssl3 are obsolete
if (info.Header.Version == SslProtocols.Ssl2)
{
// This is safe. We would not get here if the length is too small.
info.SupportedVersions |= TlsMinorVersionToProtocol(frame[4]);
// We only recognize Unified ClientHello at the moment.
// This is needed to trigger certificate selection callback in SslStream.
info.HandshakeType = TlsHandshakeType.ClientHello;
// There is no more parsing for old protocols.
return true;
}
#pragma warning restore CS0618

// Check if we have full frame.
bool isComplete = frame.Length >= HeaderSize + info.Header.Length;
Expand Down Expand Up @@ -404,10 +424,10 @@ private static bool TryParseClientHello(ReadOnlySpan<byte> clientHello, ref TlsF
// Skip compression methods (max size 2^8-1 => size fits in 1 byte)
p = SkipOpaqueType1(p);

// is invalid structure or no extensions?
// no extensions
if (p.IsEmpty)
{
return false;
return true;
}

// client_hello_extension_list (max size 2^16-1 => size fits in 2 bytes)
Expand Down