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| 1 | +// SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved. |
| 2 | +// SPDX-License-Identifier: Apache-2.0 |
| 3 | + |
| 4 | +//! Public Unix-socket transport helpers for out-of-process drivers. |
| 5 | +
|
| 6 | +use std::io; |
| 7 | +use std::os::unix::fs::{FileTypeExt, MetadataExt, PermissionsExt}; |
| 8 | +use std::path::{Path, PathBuf}; |
| 9 | +use std::pin::Pin; |
| 10 | +use std::task::{Context, Poll}; |
| 11 | + |
| 12 | +use tokio::net::{UnixListener, UnixStream}; |
| 13 | +use tokio_stream::Stream; |
| 14 | + |
| 15 | +/// Prepare and bind a private Unix socket owned by the current effective UID. |
| 16 | +pub fn bind_private(path: &Path) -> Result<UnixListener, String> { |
| 17 | + let parent = path |
| 18 | + .parent() |
| 19 | + .ok_or_else(|| format!("driver socket path '{}' has no parent", path.display()))?; |
| 20 | + let expected_uid = rustix::process::geteuid().as_raw(); |
| 21 | + std::fs::create_dir_all(parent) |
| 22 | + .map_err(|err| format!("create socket directory {}: {err}", parent.display()))?; |
| 23 | + let parent_metadata = std::fs::symlink_metadata(parent) |
| 24 | + .map_err(|err| format!("stat socket directory {}: {err}", parent.display()))?; |
| 25 | + if parent_metadata.file_type().is_symlink() || !parent_metadata.file_type().is_dir() { |
| 26 | + return Err(format!( |
| 27 | + "driver socket parent '{}' must be a directory, not a symlink", |
| 28 | + parent.display() |
| 29 | + )); |
| 30 | + } |
| 31 | + if parent_metadata.uid() != expected_uid { |
| 32 | + return Err(format!( |
| 33 | + "driver socket parent '{}' is owned by uid {}, expected {}", |
| 34 | + parent.display(), |
| 35 | + parent_metadata.uid(), |
| 36 | + expected_uid |
| 37 | + )); |
| 38 | + } |
| 39 | + std::fs::set_permissions(parent, std::fs::Permissions::from_mode(0o700)) |
| 40 | + .map_err(|err| format!("chmod socket directory {}: {err}", parent.display()))?; |
| 41 | + |
| 42 | + match std::fs::symlink_metadata(path) { |
| 43 | + Ok(metadata) |
| 44 | + if metadata.file_type().is_socket() |
| 45 | + && !metadata.file_type().is_symlink() |
| 46 | + && metadata.uid() == expected_uid => |
| 47 | + { |
| 48 | + std::fs::remove_file(path) |
| 49 | + .map_err(|err| format!("remove stale socket {}: {err}", path.display()))?; |
| 50 | + } |
| 51 | + Ok(_) => { |
| 52 | + return Err(format!( |
| 53 | + "driver socket path '{}' exists but is not an owned Unix socket", |
| 54 | + path.display() |
| 55 | + )); |
| 56 | + } |
| 57 | + Err(err) if err.kind() == io::ErrorKind::NotFound => {} |
| 58 | + Err(err) => return Err(format!("stat driver socket {}: {err}", path.display())), |
| 59 | + } |
| 60 | + |
| 61 | + let listener = UnixListener::bind(path) |
| 62 | + .map_err(|err| format!("bind driver socket {}: {err}", path.display()))?; |
| 63 | + std::fs::set_permissions(path, std::fs::Permissions::from_mode(0o600)) |
| 64 | + .map_err(|err| format!("chmod driver socket {}: {err}", path.display()))?; |
| 65 | + Ok(listener) |
| 66 | +} |
| 67 | + |
| 68 | +/// Remove a socket created by [`bind_private`]. |
| 69 | +pub struct SocketCleanup(PathBuf); |
| 70 | + |
| 71 | +impl SocketCleanup { |
| 72 | + #[must_use] |
| 73 | + pub fn new(path: PathBuf) -> Self { |
| 74 | + Self(path) |
| 75 | + } |
| 76 | +} |
| 77 | + |
| 78 | +impl Drop for SocketCleanup { |
| 79 | + fn drop(&mut self) { |
| 80 | + let _ = std::fs::remove_file(&self.0); |
| 81 | + } |
| 82 | +} |
| 83 | + |
| 84 | +/// Incoming UDS connections restricted to the driver's effective UID. |
| 85 | +pub struct SameUidUnixIncoming { |
| 86 | + listener: UnixListener, |
| 87 | + expected_uid: u32, |
| 88 | +} |
| 89 | + |
| 90 | +impl SameUidUnixIncoming { |
| 91 | + #[must_use] |
| 92 | + pub fn new(listener: UnixListener) -> Self { |
| 93 | + Self { |
| 94 | + listener, |
| 95 | + expected_uid: rustix::process::geteuid().as_raw(), |
| 96 | + } |
| 97 | + } |
| 98 | +} |
| 99 | + |
| 100 | +impl Stream for SameUidUnixIncoming { |
| 101 | + type Item = io::Result<UnixStream>; |
| 102 | + |
| 103 | + fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> { |
| 104 | + let this = self.get_mut(); |
| 105 | + loop { |
| 106 | + match this.listener.poll_accept(cx) { |
| 107 | + Poll::Ready(Ok((stream, _))) => match stream.peer_cred() { |
| 108 | + Ok(credentials) if credentials.uid() == this.expected_uid => { |
| 109 | + return Poll::Ready(Some(Ok(stream))); |
| 110 | + } |
| 111 | + Ok(credentials) => tracing::warn!( |
| 112 | + peer_uid = credentials.uid(), |
| 113 | + expected_uid = this.expected_uid, |
| 114 | + "rejected external driver socket client" |
| 115 | + ), |
| 116 | + Err(err) => { |
| 117 | + tracing::warn!(error = %err, "failed to authenticate driver socket client"); |
| 118 | + } |
| 119 | + }, |
| 120 | + Poll::Ready(Err(err)) => return Poll::Ready(Some(Err(err))), |
| 121 | + Poll::Pending => return Poll::Pending, |
| 122 | + } |
| 123 | + } |
| 124 | + } |
| 125 | +} |
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