artifactize_core/platform/
unix.rs

1//! Unix private file modes, process control, signals, and termios.
2//! Pinned file access lives in artifactize-tools.
3
4pub(crate) mod ipc;
5mod process;
6
7use std::{
8    fs::{self, DirBuilder, File, OpenOptions, Permissions},
9    future::Future,
10    io,
11    os::unix::{
12        fs::{DirBuilderExt, MetadataExt, OpenOptionsExt, PermissionsExt},
13        process::ExitStatusExt,
14    },
15    path::Path,
16    process::ExitStatus,
17};
18
19pub(crate) use tempfile::TempDir as PrivateTempDir;
20use tokio::signal::unix::{SignalKind, signal};
21
22pub(crate) use process::{
23    Child, kill_saved_group, kill_saved_session, process_start_time, running_process_start_time,
24    spawn_detached, spawn_gated, spawn_run, spawn_watched,
25};
26
27/// No Windows-style pending sharing disposition survives group cleanup.
28pub(crate) fn remove_abandoned_directory(path: &Path) -> io::Result<()> {
29    std::fs::remove_dir_all(path)
30}
31
32/// POSIX file locks are advisory, and unlinking a name never invalidates another handle's
33/// access to it, so a plain metadata or open race like Windows's never happens here.
34pub(crate) fn transient_file_access(_error: &io::Error) -> bool {
35    false
36}
37
38/// Owner-only directory mode (rwx------): these directories hold credentials, Agent sessions,
39/// sockets and review state, so no other local user may list or enter them.
40const PRIVATE_DIR_MODE: u32 = 0o700;
41
42/// Owner-only file mode (rw-------): these files hold credentials, Agent transcripts and review
43/// evidence, so no other local user may read them.
44const PRIVATE_FILE_MODE: u32 = 0o600;
45
46/// How a private directory and file are described in messages.
47pub(crate) const PRIVATE_DIRECTORY: &str = "owner-only (mode 0700)";
48pub(crate) const PRIVATE_FILE: &str = "readable by their owner only (mode 0600)";
49
50/// The group and other permission bits; a private path has none of them set.
51pub(crate) const GROUP_OTHER_BITS: u32 = 0o077;
52
53/// Group/other write bits let another user replace system-alias or IPC parent
54/// directories, so neither the alias nor the endpoint under them can be trusted.
55const GROUP_OTHER_WRITE_BITS: u32 = 0o022;
56
57/// The permission bits of a mode, without the file type and set-id bits, so a file can be
58/// compared with [`PRIVATE_FILE_MODE`] exactly.
59const PERMISSION_BITS: u32 = 0o777;
60
61/// Create a directory and its missing parents as 0700; existing ones keep their mode.
62pub(crate) fn create_private_dir_all(path: &Path) -> io::Result<()> {
63    DirBuilder::new()
64        .recursive(true)
65        .mode(PRIVATE_DIR_MODE)
66        .create(path)
67}
68
69/// Create one directory as exactly 0700, whatever the umask.
70pub(crate) fn create_private_dir(path: &Path) -> io::Result<()> {
71    DirBuilder::new().mode(PRIVATE_DIR_MODE).create(path)?;
72    fs::set_permissions(path, Permissions::from_mode(PRIVATE_DIR_MODE))
73}
74
75/// A new 0700 temporary directory below `parent`.
76pub(crate) fn private_tempdir_in(prefix: &str, parent: &Path) -> io::Result<PrivateTempDir> {
77    let directory = tempfile::Builder::new()
78        .prefix(prefix)
79        .permissions(Permissions::from_mode(PRIVATE_DIR_MODE))
80        .tempdir_in(parent)?;
81    fs::set_permissions(directory.path(), Permissions::from_mode(PRIVATE_DIR_MODE))?;
82    Ok(directory)
83}
84
85/// Whether a directory grants nothing to its group or others.
86pub(crate) fn is_private_dir(path: &Path) -> io::Result<bool> {
87    Ok(fs::metadata(path)?.mode() & GROUP_OTHER_BITS == 0)
88}
89
90/// Whether an open file is a regular, single-link 0600 file.
91pub(crate) fn is_private_file(file: &File) -> io::Result<bool> {
92    let metadata = file.metadata()?;
93    Ok(metadata.is_file()
94        && metadata.mode() & PERMISSION_BITS == PRIVATE_FILE_MODE
95        && metadata.nlink() == 1)
96}
97
98/// Options that create files as 0600.
99pub(crate) fn private_options() -> OpenOptions {
100    let mut options = OpenOptions::new();
101    options.mode(PRIVATE_FILE_MODE);
102    options
103}
104
105/// Make an open file 0600.
106pub(crate) fn restrict_file(file: &File) -> io::Result<()> {
107    file.set_permissions(Permissions::from_mode(PRIVATE_FILE_MODE))
108}
109
110/// Persist a directory's entries, such as a file just renamed into it.
111pub(crate) fn sync_dir(path: &Path) -> io::Result<()> {
112    File::open(path).and_then(|directory| directory.sync_all())
113}
114
115/// A file's identity on its volume: its device and inode.
116pub(crate) fn file_identity(file: &File) -> io::Result<super::FileIdentity> {
117    let metadata = file.metadata()?;
118    Ok(super::FileIdentity {
119        volume: metadata.dev(),
120        index: metadata.ino(),
121    })
122}
123
124/// The effective user, the owner that private paths must have.
125pub(crate) fn current_user() -> u32 {
126    // SAFETY: geteuid has no preconditions and does not mutate process identity.
127    unsafe { libc::geteuid() }
128}
129
130/// Whether an open file or directory belongs to the current user and grants nothing to its
131/// group or others.
132pub(crate) fn is_owner_only(file: &File) -> io::Result<bool> {
133    let metadata = file.metadata()?;
134    Ok(metadata.mode() & GROUP_OTHER_BITS == 0 && metadata.uid() == current_user())
135}
136
137/// Environment variable names compare exactly.
138pub(crate) const ENV_NAMES_IGNORE_CASE: bool = false;
139
140/// The variable naming the user's home directory.
141pub(crate) const HOME_VARIABLE: &str = "HOME";
142
143/// Variables programs read their temporary directory from. `TMP` and `TEMP` are set too, for
144/// programs written for Windows.
145pub(crate) const TEMP_VARIABLES: &[&str] = &["TMPDIR", "TMP", "TEMP"];
146
147/// Variables naming a per-user state directory, in order; artifactize keeps its state in an
148/// `artifactize` folder below the first one set, and otherwise below `HOME`.
149pub(crate) const STATE_VARIABLES: &[&str] = &["XDG_STATE_HOME"];
150
151/// The variables naming the signed-in user, in order.
152pub(crate) const USER_VARIABLES: &[&str] = &["USER", "LOGNAME"];
153
154/// The user's home directory.
155pub(crate) fn home_directory() -> Option<std::path::PathBuf> {
156    std::env::var_os(HOME_VARIABLE)
157        .filter(|path| !path.is_empty())
158        .map(Into::into)
159}
160
161/// A path from the raw bytes a tool such as git prints: any bytes name a Unix path.
162pub(crate) fn path_from_bytes(bytes: &[u8]) -> std::path::PathBuf {
163    use std::os::unix::ffi::OsStringExt;
164    std::ffi::OsString::from_vec(bytes.to_vec()).into()
165}
166
167/// Unix programs end a line with LF only.
168pub(crate) const CRLF_LINE_ENDINGS: bool = false;
169
170/// Whether a terminal that cannot hide input is still read, visibly, after a warning. A Unix
171/// terminal always can; failing to hide input is an error.
172pub const VISIBLE_INPUT_FALLBACK: bool = false;
173
174/// The signal that ended a process, if one did.
175pub(crate) fn exit_signal(status: &ExitStatus) -> Option<i32> {
176    status.signal()
177}
178
179/// The operating system's host name, without depending on a proc filesystem.
180pub(crate) fn host_name() -> Option<String> {
181    hostname::get().ok()?.into_string().ok()
182}
183
184/// The absolute form of `path` with a leading macOS system alias (`/tmp`, `/var`, `/etc`)
185/// replaced by its fixed `/private` target. The alias and its parents must be root-owned
186/// and not replaceable; descendants are left for the caller to open without following links.
187#[cfg(target_os = "macos")]
188pub(crate) fn resolve_system_aliases(path: &Path) -> io::Result<std::path::PathBuf> {
189    let absolute = std::path::absolute(path)?;
190    for name in ["tmp", "var", "etc"] {
191        let alias = Path::new("/").join(name);
192        if let Ok(suffix) = absolute.strip_prefix(&alias) {
193            let metadata = alias.symlink_metadata()?;
194            let target = Path::new("/private").join(name);
195            let link = fs::read_link(&alias)?;
196            let link = if link.is_absolute() {
197                link
198            } else {
199                Path::new("/").join(link)
200            };
201            if !metadata.is_symlink() || metadata.uid() != 0 || link != target {
202                return Err(io::Error::other(format!(
203                    "Refusing an untrusted system alias: {}",
204                    alias.display()
205                )));
206            }
207            for parent in [Path::new("/"), Path::new("/private")] {
208                let metadata = parent.symlink_metadata()?;
209                if !metadata.is_dir()
210                    || metadata.uid() != 0
211                    || metadata.mode() & GROUP_OTHER_WRITE_BITS != 0
212                {
213                    return Err(io::Error::other(
214                        "System alias parents must not be replaceable.",
215                    ));
216                }
217            }
218            return Ok(target.join(suffix));
219        }
220    }
221    Ok(absolute)
222}
223
224/// The absolute form of `path`; this system has no aliased system roots.
225#[cfg(not(target_os = "macos"))]
226pub(crate) fn resolve_system_aliases(path: &Path) -> io::Result<std::path::PathBuf> {
227    std::path::absolute(path)
228}
229
230/// Register for SIGINT and SIGTERM now; the future completes at the first of them.
231pub fn stop_requested() -> io::Result<impl Future<Output = ()> + Send + 'static> {
232    let mut interrupt = signal(SignalKind::interrupt())?;
233    let mut terminate = signal(SignalKind::terminate())?;
234    Ok(async move {
235        tokio::select! { _ = interrupt.recv() => {}, _ = terminate.recv() => {} }
236    })
237}
238
239/// Turns terminal echo off until dropped, so a pasted secret is not shown.
240pub struct HiddenInput(libc::termios);
241
242impl HiddenInput {
243    pub fn new() -> io::Result<Self> {
244        let mut termios = std::mem::MaybeUninit::uninit();
245        // SAFETY: tcgetattr fills the struct on success; it is read only then.
246        let saved = unsafe {
247            if libc::tcgetattr(libc::STDIN_FILENO, termios.as_mut_ptr()) != 0 {
248                return Err(io::Error::last_os_error());
249            }
250            termios.assume_init()
251        };
252        let mut hidden = saved;
253        hidden.c_lflag &= !libc::ECHO;
254        // SAFETY: a valid termios for the same descriptor.
255        if unsafe { libc::tcsetattr(libc::STDIN_FILENO, libc::TCSANOW, &hidden) } != 0 {
256            return Err(io::Error::last_os_error());
257        }
258        Ok(Self(saved))
259    }
260}
261
262impl Drop for HiddenInput {
263    fn drop(&mut self) {
264        // SAFETY: restores the attributes read in `new`.
265        unsafe { libc::tcsetattr(libc::STDIN_FILENO, libc::TCSANOW, &self.0) };
266    }
267}
268
269#[cfg(test)]
270mod tests {
271    use super::*;
272
273    /// Unlike Windows, no error here is ever transient in this sense; the predicate is a
274    /// permanent no-op, not a gap in detecting a race that would need retrying.
275    #[test]
276    fn transient_file_access_is_always_false() {
277        assert!(!transient_file_access(&io::Error::from_raw_os_error(5)));
278        assert!(!transient_file_access(&io::Error::new(
279            io::ErrorKind::PermissionDenied,
280            "permission denied"
281        )));
282    }
283}
artifactize_core/platform/unix.rs

artifactize_core/platform/
unix.rs
