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, hide_console_window, kill_saved_group, kill_saved_session, process_start_time,
24    running_process_start_time, spawn_detached, spawn_gated, spawn_now, spawn_run, spawn_watched,
25};
26
27/// Give the heap memory freed so far back to the system. glibc keeps freed memory in its
28/// arenas for reuse, so a long-lived process that once read much stays that large; macOS's
29/// allocator returns it by itself.
30pub(crate) fn release_free_memory() {
31    #[cfg(all(target_os = "linux", target_env = "gnu"))]
32    // SAFETY: malloc_trim only releases memory that is already free, under glibc's own locks.
33    unsafe {
34        libc::malloc_trim(0);
35    }
36}
37
38/// No Windows-style pending sharing disposition survives group cleanup.
39pub(crate) fn remove_abandoned_directory(path: &Path) -> io::Result<()> {
40    std::fs::remove_dir_all(path)
41}
42
43/// POSIX file locks are advisory, and unlinking a name never invalidates another handle's
44/// access to it, so a plain metadata or open race like Windows's never happens here.
45pub(crate) fn transient_file_access(_error: &io::Error) -> bool {
46    false
47}
48
49/// Owner-only directory mode (rwx------): these directories hold credentials, Agent sessions,
50/// sockets and review state, so no other local user may list or enter them.
51const PRIVATE_DIR_MODE: u32 = 0o700;
52
53/// Owner-only file mode (rw-------): these files hold credentials, Agent transcripts and review
54/// evidence, so no other local user may read them.
55const PRIVATE_FILE_MODE: u32 = 0o600;
56
57/// How a private directory and file are described in messages.
58pub(crate) const PRIVATE_DIRECTORY: &str = "owner-only (mode 0700)";
59pub(crate) const PRIVATE_FILE: &str = "readable by their owner only (mode 0600)";
60
61/// The group and other permission bits; a private path has none of them set.
62pub(crate) const GROUP_OTHER_BITS: u32 = 0o077;
63
64/// Group/other write bits let another user replace system-alias or IPC parent
65/// directories, so neither the alias nor the endpoint under them can be trusted.
66const GROUP_OTHER_WRITE_BITS: u32 = 0o022;
67
68/// The permission bits of a mode, without the file type and set-id bits, so a file can be
69/// compared with [`PRIVATE_FILE_MODE`] exactly.
70const PERMISSION_BITS: u32 = 0o777;
71
72/// Create a directory and its missing parents as 0700; existing ones keep their mode.
73pub(crate) fn create_private_dir_all(path: &Path) -> io::Result<()> {
74    DirBuilder::new()
75        .recursive(true)
76        .mode(PRIVATE_DIR_MODE)
77        .create(path)
78}
79
80/// Create one directory as exactly 0700, whatever the umask.
81pub(crate) fn create_private_dir(path: &Path) -> io::Result<()> {
82    DirBuilder::new().mode(PRIVATE_DIR_MODE).create(path)?;
83    fs::set_permissions(path, Permissions::from_mode(PRIVATE_DIR_MODE))
84}
85
86/// A new 0700 temporary directory below `parent`.
87pub(crate) fn private_tempdir_in(prefix: &str, parent: &Path) -> io::Result<PrivateTempDir> {
88    let directory = tempfile::Builder::new()
89        .prefix(prefix)
90        .permissions(Permissions::from_mode(PRIVATE_DIR_MODE))
91        .tempdir_in(parent)?;
92    fs::set_permissions(directory.path(), Permissions::from_mode(PRIVATE_DIR_MODE))?;
93    Ok(directory)
94}
95
96/// Whether a directory grants nothing to its group or others.
97pub(crate) fn is_private_dir(path: &Path) -> io::Result<bool> {
98    Ok(fs::metadata(path)?.mode() & GROUP_OTHER_BITS == 0)
99}
100
101/// Whether an open file is a regular, single-link 0600 file.
102pub(crate) fn is_private_file(file: &File) -> io::Result<bool> {
103    let metadata = file.metadata()?;
104    Ok(metadata.is_file()
105        && metadata.mode() & PERMISSION_BITS == PRIVATE_FILE_MODE
106        && metadata.nlink() == 1)
107}
108
109/// Options that create files as 0600.
110pub(crate) fn private_options() -> OpenOptions {
111    let mut options = OpenOptions::new();
112    options.mode(PRIVATE_FILE_MODE);
113    options
114}
115
116/// Make an open file 0600.
117pub(crate) fn restrict_file(file: &File) -> io::Result<()> {
118    file.set_permissions(Permissions::from_mode(PRIVATE_FILE_MODE))
119}
120
121/// Persist a directory's entries, such as a file just renamed into it.
122pub(crate) fn sync_dir(path: &Path) -> io::Result<()> {
123    File::open(path).and_then(|directory| directory.sync_all())
124}
125
126/// A file's identity on its volume: its device and inode.
127pub(crate) fn file_identity(file: &File) -> io::Result<super::FileIdentity> {
128    let metadata = file.metadata()?;
129    Ok(super::FileIdentity {
130        volume: metadata.dev(),
131        index: metadata.ino(),
132    })
133}
134
135/// The effective user, the owner that private paths must have.
136pub(crate) fn current_user() -> u32 {
137    // SAFETY: geteuid has no preconditions and does not mutate process identity.
138    unsafe { libc::geteuid() }
139}
140
141/// Whether an open file or directory belongs to the current user and grants nothing to its
142/// group or others.
143pub(crate) fn is_owner_only(file: &File) -> io::Result<bool> {
144    let metadata = file.metadata()?;
145    Ok(metadata.mode() & GROUP_OTHER_BITS == 0 && metadata.uid() == current_user())
146}
147
148/// Environment variable names compare exactly.
149pub(crate) const ENV_NAMES_IGNORE_CASE: bool = false;
150
151/// The variable naming the user's home directory.
152pub(crate) const HOME_VARIABLE: &str = "HOME";
153
154/// Variables programs read their temporary directory from. `TMP` and `TEMP` are set too, for
155/// programs written for Windows.
156pub(crate) const TEMP_VARIABLES: &[&str] = &["TMPDIR", "TMP", "TEMP"];
157
158/// Variables naming a per-user state directory, in order; artifactize keeps its state in an
159/// `artifactize` folder below the first one set, and otherwise below `HOME`.
160pub(crate) const STATE_VARIABLES: &[&str] = &["XDG_STATE_HOME"];
161
162/// The variables naming the signed-in user, in order.
163pub(crate) const USER_VARIABLES: &[&str] = &["USER", "LOGNAME"];
164
165/// The user's home directory.
166pub(crate) fn home_directory() -> Option<std::path::PathBuf> {
167    std::env::var_os(HOME_VARIABLE)
168        .filter(|path| !path.is_empty())
169        .map(Into::into)
170}
171
172/// A path from the raw bytes a tool such as git prints: any bytes name a Unix path.
173pub(crate) fn path_from_bytes(bytes: &[u8]) -> std::path::PathBuf {
174    use std::os::unix::ffi::OsStringExt;
175    std::ffi::OsString::from_vec(bytes.to_vec()).into()
176}
177
178/// Unix programs end a line with LF only.
179pub(crate) const CRLF_LINE_ENDINGS: bool = false;
180
181/// Whether a terminal that cannot hide input is still read, visibly, after a warning. A Unix
182/// terminal always can; failing to hide input is an error.
183pub const VISIBLE_INPUT_FALLBACK: bool = false;
184
185/// The signal that ended a process, if one did.
186pub(crate) fn exit_signal(status: &ExitStatus) -> Option<i32> {
187    status.signal()
188}
189
190/// The operating system's host name, without depending on a proc filesystem.
191pub(crate) fn host_name() -> Option<String> {
192    hostname::get().ok()?.into_string().ok()
193}
194
195/// The absolute form of `path` with a leading macOS system alias (`/tmp`, `/var`, `/etc`)
196/// replaced by its fixed `/private` target. The alias and its parents must be root-owned
197/// and not replaceable; descendants are left for the caller to open without following links.
198#[cfg(target_os = "macos")]
199pub(crate) fn resolve_system_aliases(path: &Path) -> io::Result<std::path::PathBuf> {
200    let absolute = std::path::absolute(path)?;
201    for name in ["tmp", "var", "etc"] {
202        let alias = Path::new("/").join(name);
203        if let Ok(suffix) = absolute.strip_prefix(&alias) {
204            let metadata = alias.symlink_metadata()?;
205            let target = Path::new("/private").join(name);
206            let link = fs::read_link(&alias)?;
207            let link = if link.is_absolute() {
208                link
209            } else {
210                Path::new("/").join(link)
211            };
212            if !metadata.is_symlink() || metadata.uid() != 0 || link != target {
213                return Err(io::Error::other(format!(
214                    "Refusing an untrusted system alias: {}",
215                    alias.display()
216                )));
217            }
218            for parent in [Path::new("/"), Path::new("/private")] {
219                let metadata = parent.symlink_metadata()?;
220                if !metadata.is_dir()
221                    || metadata.uid() != 0
222                    || metadata.mode() & GROUP_OTHER_WRITE_BITS != 0
223                {
224                    return Err(io::Error::other(
225                        "System alias parents must not be replaceable.",
226                    ));
227                }
228            }
229            return Ok(target.join(suffix));
230        }
231    }
232    Ok(absolute)
233}
234
235/// The absolute form of `path`; this system has no aliased system roots.
236#[cfg(not(target_os = "macos"))]
237pub(crate) fn resolve_system_aliases(path: &Path) -> io::Result<std::path::PathBuf> {
238    std::path::absolute(path)
239}
240
241/// Register for SIGINT and SIGTERM now; the future completes at the first of them.
242pub fn stop_requested() -> io::Result<impl Future<Output = ()> + Send + 'static> {
243    let mut interrupt = signal(SignalKind::interrupt())?;
244    let mut terminate = signal(SignalKind::terminate())?;
245    Ok(async move {
246        tokio::select! { _ = interrupt.recv() => {}, _ = terminate.recv() => {} }
247    })
248}
249
250/// Turns terminal echo off until dropped, so a pasted secret is not shown.
251pub struct HiddenInput(libc::termios);
252
253impl HiddenInput {
254    pub fn new() -> io::Result<Self> {
255        let mut termios = std::mem::MaybeUninit::uninit();
256        // SAFETY: tcgetattr fills the struct on success; it is read only then.
257        let saved = unsafe {
258            if libc::tcgetattr(libc::STDIN_FILENO, termios.as_mut_ptr()) != 0 {
259                return Err(io::Error::last_os_error());
260            }
261            termios.assume_init()
262        };
263        let mut hidden = saved;
264        hidden.c_lflag &= !libc::ECHO;
265        // SAFETY: a valid termios for the same descriptor.
266        if unsafe { libc::tcsetattr(libc::STDIN_FILENO, libc::TCSANOW, &hidden) } != 0 {
267            return Err(io::Error::last_os_error());
268        }
269        Ok(Self(saved))
270    }
271}
272
273impl Drop for HiddenInput {
274    fn drop(&mut self) {
275        // SAFETY: restores the attributes read in `new`.
276        unsafe { libc::tcsetattr(libc::STDIN_FILENO, libc::TCSANOW, &self.0) };
277    }
278}
279
280#[cfg(test)]
281mod tests {
282    use super::*;
283
284    /// Unlike Windows, no error here is ever transient in this sense; the predicate is a
285    /// permanent no-op, not a gap in detecting a race that would need retrying.
286    #[test]
287    fn transient_file_access_is_always_false() {
288        assert!(!transient_file_access(&io::Error::from_raw_os_error(5)));
289        assert!(!transient_file_access(&io::Error::new(
290            io::ErrorKind::PermissionDenied,
291            "permission denied"
292        )));
293    }
294}
artifactize_core/platform/unix.rs

artifactize_core/platform/
unix.rs
