Harden permissions for pipe used in SharedServer.

[cincuranet]

No description provided.

[Copilot]

Pull request overview

This PR tightens Unix named-pipe (Unix domain socket) filesystem permissions when PipeOptions.CurrentUserOnly is used, by explicitly setting the socket file’s mode to user-only (0600). This aligns the on-disk endpoint permissions with the “current user only” intent and adds a regression test.

Changes:

• Set the Unix domain socket file mode to UserRead | UserWrite when creating a SharedServer for CurrentUserOnly.
• Add a Unix test validating the socket file mode when CurrentUserOnly is specified.
• Minor refactors to use PipeOptions.HasFlag(...) in a few places.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
src/libraries/System.IO.Pipes/src/System/IO/Pipes/NamedPipeServerStream.Unix.cs	Applies 0600 permissions to the bound socket path for CurrentUserOnly; adds cleanup on failure; refactors option checks.
src/libraries/System.IO.Pipes/tests/NamedPipeTests/NamedPipeTest.CurrentUserOnly.Unix.cs	Adds a regression test asserting the created socket path has user-only permissions.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

[JanKrivanek]

Thank you!

[cincuranet]

/ba-g Failures are unrelated.

[dotnet-policy-service]

Added needs-breaking-change-doc-created label because this PR has the breaking-change label.

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Tagging @dotnet/compat for awareness of the breaking change.