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Harden permissions for pipe used in SharedServer. #127239

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31 changes: 27 additions & 4 deletions src/libraries/System.IO.Pipes/src/System/IO/Pipes/NamedPipeServerStream.Unix.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -244,6 +244,8 @@ private sealed class SharedServer
private readonly int _maxCount;
/// <summary>The concurrent number of concurrent streams using this instance.</summary>
private int _currentCount;
/// <summary>Whether the socket file mode has been tightened to current-user-only (0600).</summary>
private bool _isCurrentUserOnly;

internal static SharedServer Get(string path, int maxCount, PipeOptions pipeOptions)
{
Expand All @@ -252,9 +254,9 @@ internal static SharedServer Get(string path, int maxCount, PipeOptions pipeOpti

lock (s_servers)
{
SharedServer? server;
bool isFirstPipeInstance = (pipeOptions & PipeOptions.FirstPipeInstance) != 0;
if (s_servers.TryGetValue(path, out server))
bool isCurrentUserOnly = (pipeOptions & PipeOptions.CurrentUserOnly) != 0;
if (s_servers.TryGetValue(path, out SharedServer? server))
{
// On Windows, if a subsequent server stream is created for the same pipe and with a different
// max count, the subsequent count is largely ignored in that it doesn't change the number of
Expand All @@ -269,11 +271,21 @@ internal static SharedServer Get(string path, int maxCount, PipeOptions pipeOpti
{
throw new UnauthorizedAccessException(SR.Format(SR.UnauthorizedAccess_IODenied_Path, path));
}

// Ratchet to current-user-only if requested. We never loosen, even if a later
// instance for the same path does not request CurrentUserOnly: silently downgrading
// a security choice another caller made would be worse than the order-dependent
// surprise of a non-CurrentUserOnly server inheriting a 0600 socket.
if (isCurrentUserOnly && !server._isCurrentUserOnly)
{
File.SetUnixFileMode(path, UnixFileMode.UserRead | UnixFileMode.UserWrite);
server._isCurrentUserOnly = true;
}
}
else
{
// No instance exists yet for this path. Create one a new.
server = new SharedServer(path, maxCount, isFirstPipeInstance);
server = new SharedServer(path, maxCount, isFirstPipeInstance, isCurrentUserOnly);
s_servers.Add(path, server);
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}

Expand Down Expand Up @@ -308,7 +320,7 @@ internal void Dispose(bool disposing)
}
}

private SharedServer(string path, int maxCount, bool isFirstPipeInstance)
private SharedServer(string path, int maxCount, bool isFirstPipeInstance, bool isCurrentUserOnly)
{
if (!isFirstPipeInstance)
{
Expand All @@ -325,6 +337,13 @@ private SharedServer(string path, int maxCount, bool isFirstPipeInstance)
{
socket.Bind(new UnixDomainSocketEndPoint(path));
isSocketBound = true;

_isCurrentUserOnly = isCurrentUserOnly;
if (_isCurrentUserOnly)
{
File.SetUnixFileMode(path, UnixFileMode.UserRead | UnixFileMode.UserWrite);
}

socket.Listen(int.MaxValue);
}
catch (SocketException) when (isFirstPipeInstance && !isSocketBound)
Expand All @@ -334,6 +353,10 @@ private SharedServer(string path, int maxCount, bool isFirstPipeInstance)
}
catch
{
if (isSocketBound)
{
Interop.Sys.Unlink(path); // ignore any failures
}
socket.Dispose();
throw;
}
Expand Down
53 changes: 53 additions & 0 deletions src/libraries/System.IO.Pipes/tests/NamedPipeTests/NamedPipeTest.CurrentUserOnly.Unix.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,59 @@ public async Task Connection_UnderDifferentUsers_BehavesAsExpected(
}
}

[Fact]
[ActiveIssue("https://github.com/dotnet/runtime/issues/77469", TestPlatforms.iOS | TestPlatforms.tvOS)]
[ActiveIssue("https://github.com/dotnet/runtime/issues/77470", TestPlatforms.LinuxBionic)]
public void CurrentUserOnly_SetsUnixFileMode()
{
string pipeName = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());

using (var server = new NamedPipeServerStream(pipeName, PipeDirection.InOut, 1, PipeTransmissionMode.Byte, PipeOptions.CurrentUserOnly))
{
Assert.Equal(UnixFileMode.UserRead | UnixFileMode.UserWrite, File.GetUnixFileMode(pipeName));
}
}

[Fact]
[ActiveIssue("https://github.com/dotnet/runtime/issues/77469", TestPlatforms.iOS | TestPlatforms.tvOS)]
[ActiveIssue("https://github.com/dotnet/runtime/issues/77470", TestPlatforms.LinuxBionic)]
public void CurrentUserOnly_SubsequentInstance_TightensSharedMode()
{
string pipeName = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());

using (var first = new NamedPipeServerStream(pipeName, PipeDirection.InOut, 2, PipeTransmissionMode.Byte, PipeOptions.None))
{
UnixFileMode initialMode = File.GetUnixFileMode(pipeName);
Assert.NotEqual(UnixFileMode.UserRead | UnixFileMode.UserWrite, initialMode);

using (var second = new NamedPipeServerStream(pipeName, PipeDirection.InOut, 2, PipeTransmissionMode.Byte, PipeOptions.CurrentUserOnly))
{
Assert.Equal(UnixFileMode.UserRead | UnixFileMode.UserWrite, File.GetUnixFileMode(pipeName));
}

// Mode is one-way: it stays restrictive even after the CurrentUserOnly instance is disposed.
Assert.Equal(UnixFileMode.UserRead | UnixFileMode.UserWrite, File.GetUnixFileMode(pipeName));
}
}

[Fact]
[ActiveIssue("https://github.com/dotnet/runtime/issues/77469", TestPlatforms.iOS | TestPlatforms.tvOS)]
[ActiveIssue("https://github.com/dotnet/runtime/issues/77470", TestPlatforms.LinuxBionic)]
public void CurrentUserOnly_SubsequentInstance_DoesNotLoosenSharedMode()
{
string pipeName = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());

using (var first = new NamedPipeServerStream(pipeName, PipeDirection.InOut, 2, PipeTransmissionMode.Byte, PipeOptions.CurrentUserOnly))
{
Assert.Equal(UnixFileMode.UserRead | UnixFileMode.UserWrite, File.GetUnixFileMode(pipeName));

using (var second = new NamedPipeServerStream(pipeName, PipeDirection.InOut, 2, PipeTransmissionMode.Byte, PipeOptions.None))
{
Assert.Equal(UnixFileMode.UserRead | UnixFileMode.UserWrite, File.GetUnixFileMode(pipeName));
}
}
}

private static void ConnectClientFromRemoteInvoker(string pipeName, string isCurrentUserOnly, string isReadOnly)
{
PipeOptions pipeOptions = bool.Parse(isCurrentUserOnly) ? PipeOptions.CurrentUserOnly : PipeOptions.None;
Expand Down
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