Vakyartha documentation

1//! Linux filesystem containment via the Landlock LSM (kernel 5.13+).
2//!
3//! The `Sandbox` trait wraps a shell command; here the wrapper re-executes
4//! THIS binary with a hidden subcommand that applies the ruleset to itself
5//! and only then runs the command as a child, so restrictions are inherited.
6//! Fail-closed: unsupported kernels surface an error instead of silently
7//! running unrestricted.
8
9use std::path::{Path, PathBuf};
10use std::sync::Arc;
11
12use super::backend::{Sandbox, SandboxMode};
13
14pub const SANDBOX_SUBCOMMAND: &str = "__sandbox";
15
16pub fn runner_main(args: impl IntoIterator<Item = std::ffi::OsString>) -> i32 {
17 let mut read = Vec::new();
18 let mut write = Vec::new();
19 let mut read_only = false;
20 let mut command = Vec::new();
21 let mut args = args.into_iter();
22 while let Some(arg) = args.next() {
23 if arg == "--" {
24 command.extend(args.map(|part| part.to_string_lossy().into_owned()));
25 break;
26 }
27 if arg == "--ro" {
28 read_only = true;
29 } else if arg == "--read" {
30 let Some(path) = args.next() else {
31 eprintln!("sandbox: --read requires a path");
32 return 125;
33 };
34 read.push(PathBuf::from(path));
35 } else if arg == "--rw" {
36 let Some(path) = args.next() else {
37 eprintln!("sandbox: --rw requires a path");
38 return 125;
39 };
40 write.push(PathBuf::from(path));
41 } else {
42 eprintln!("sandbox: invalid argument {}", arg.to_string_lossy());
43 return 125;
44 }
45 }
46 if command.is_empty() {
47 eprintln!("sandbox: no command given");
48 return 125;
49 }
50 #[cfg(target_os = "linux")]
51 {
52 if let Err(error) = apply(&read, &write, read_only) {
53 eprintln!("sandbox: {error}");
54 return 126;
55 }
56 match std::process::Command::new("/bin/sh")
57 .arg("-c")
58 .arg(command.join(" "))
59 .status()
60 {
61 Ok(status) => status.code().unwrap_or(1),
62 Err(error) => {
63 eprintln!("sandbox: exec failed: {error}");
64 127
65 }
66 }
67 }
68 #[cfg(not(target_os = "linux"))]
69 {
70 let _ = (read, write, read_only, command);
71 eprintln!("sandbox: not supported on this platform");
72 126
73 }
74}
75
76#[derive(Debug, Clone)]
77pub struct Landlock {
78 pub mode: SandboxMode,
79 pub read_paths: Vec<PathBuf>,
80 pub write_paths: Vec<PathBuf>,
81}
82
83impl Landlock {
84 pub fn new(mode: SandboxMode, cwd: &Path) -> Self {
85 Self::build(mode, cwd, true)
86 }
87
88 /// Task-copy containment excludes host temp roots even when the source
89 /// workspace is under one of them.
90 pub fn task_copy(mode: SandboxMode, cwd: &Path) -> Self {
91 Self::build(mode, cwd, false)
92 }
93
94 fn build(mode: SandboxMode, cwd: &Path, allow_host_temp: bool) -> Self {
95 let canonical = cwd.canonicalize().unwrap_or_else(|_| cwd.to_path_buf());
96 let mut read_paths: Vec<PathBuf> = [
97 "/bin", "/usr", "/lib", "/lib64", "/etc", "/dev", "/proc", "/sys", "/opt",
98 ]
99 .into_iter()
100 .map(PathBuf::from)
101 .filter(|path| path.exists())
102 .collect();
103 read_paths.push(canonical.clone());
104 if let Ok(executable) = std::env::current_exe()
105 && let Some(parent) = executable.parent()
106 {
107 read_paths.push(parent.to_path_buf());
108 }
109 if let Some(home) = std::env::var_os("HOME").map(PathBuf::from) {
110 for relative in [
111 ".cargo/bin",
112 ".cargo/git",
113 ".cargo/registry",
114 ".rustup",
115 ".local/bin",
116 ] {
117 let path = home.join(relative);
118 if path.exists() {
119 read_paths.push(path);
120 }
121 }
122 }
123 if allow_host_temp {
124 for path in super::backend::Seatbelt::temp_write_paths() {
125 let path = PathBuf::from(path);
126 if path.exists() && !read_paths.contains(&path) {
127 read_paths.push(path);
128 }
129 }
130 }
131 let mut write_paths = match mode {
132 SandboxMode::WorkspaceWrite => vec![canonical],
133 _ => Vec::new(),
134 };
135 // Workspace-write must include OS temp areas or every test suite
136 // using tempfile/std::env::temp_dir dies under the sandbox (found
137 // by dogfooding `cargo test` through the agent).
138 if mode == SandboxMode::WorkspaceWrite && allow_host_temp {
139 for p in super::backend::Seatbelt::temp_write_paths() {
140 let pb = PathBuf::from(p);
141 if !write_paths.contains(&pb) {
142 write_paths.push(pb);
143 }
144 }
145 }
146 Landlock {
147 mode,
148 read_paths,
149 write_paths,
150 }
151 }
152}
153
154#[cfg(test)]
155mod task_copy_tests {
156 use super::*;
157
158 #[test]
159 fn task_copy_excludes_host_temp_write_roots() {
160 let copy = tempfile::tempdir().expect("task copy");
161 let sandbox = Landlock::task_copy(SandboxMode::WorkspaceWrite, copy.path());
162 assert_eq!(
163 sandbox.write_paths,
164 vec![copy.path().canonicalize().expect("canonical copy")]
165 );
166 assert!(!sandbox.read_paths.contains(&PathBuf::from("/private/tmp")));
167 }
168}
169
170impl Sandbox for Landlock {
171 fn name(&self) -> &str {
172 "landlock"
173 }
174
175 fn wrap(&self, command: &str) -> String {
176 if self.mode == SandboxMode::Off {
177 return command.to_string();
178 }
179 let exe = match std::env::current_exe() {
180 Ok(p) => p.display().to_string(),
181 // Without a resolvable executable the containment cannot be
182 // established; refuse to run rather than escape the sandbox.
183 Err(_) => {
184 return "echo 'vak sandbox: cannot locate executable' >&2; exit 126".to_string();
185 }
186 };
187 let mut parts = vec![shell_quote(&exe), SANDBOX_SUBCOMMAND.to_string()];
188 if self.mode == SandboxMode::ReadOnly {
189 parts.push("--ro".to_string());
190 }
191 for path in &self.read_paths {
192 parts.push(format!(
193 "--read {}",
194 shell_quote(&path.display().to_string())
195 ));
196 }
197 for p in &self.write_paths {
198 parts.push(format!("--rw {}", shell_quote(&p.display().to_string())));
199 }
200 parts.push("--".to_string());
201 parts.push(shell_quote(command));
202 parts.join(" ")
203 }
204
205 fn read_only_variant(&self) -> Option<Arc<dyn Sandbox>> {
206 Some(Arc::new(Landlock {
207 mode: SandboxMode::ReadOnly,
208 read_paths: self.read_paths.clone(),
209 write_paths: Vec::new(),
210 }))
211 }
212}
213
214/// Applies the ruleset to the CURRENT process. Read+execute only under
215/// `read_paths`; writes only under `write_paths` unless `read_only`. ALL TCP bind/connect
216/// is denied in every sandboxed mode — parity with Seatbelt, whose
217/// deny-default profile leaves no network allowance — and the call FAILS
218/// CLOSED when the kernel cannot enforce that denial (needs ABI v4).
219pub fn apply(
220 read_paths: &[PathBuf],
221 write_paths: &[PathBuf],
222 read_only: bool,
223) -> Result<(), String> {
224 use landlock::{
225 ABI, Access, AccessFs, AccessNet, Ruleset, RulesetAttr, RulesetCreatedAttr, RulesetStatus,
226 path_beneath_rules,
227 };
228
229 let fs_abi = ABI::V1;
230 let created = Ruleset::default()
231 .handle_access(AccessFs::from_all(fs_abi))
232 .and_then(|r| r.handle_access(AccessNet::from_all(ABI::V4)))
233 .and_then(|r| r.create())
234 .map_err(|e| format!("landlock: {e}"))?;
235 let created = created
236 .add_rules(path_beneath_rules(read_paths, AccessFs::from_read(fs_abi)))
237 .map_err(|e| format!("landlock: {e}"))?;
238 let restricted = if read_only {
239 created.restrict_self()
240 } else {
241 created
242 .add_rules(path_beneath_rules(write_paths, AccessFs::from_all(fs_abi)))
243 .and_then(|r| r.restrict_self())
244 }
245 .map_err(|e| format!("landlock: {e}"))?;
246 match restricted.ruleset {
247 RulesetStatus::FullyEnforced => Ok(()),
248 _ => Err(
249 "landlock: full enforcement unavailable (kernel needs fs ABI v1+, net ABI v4+)"
250 .to_string(),
251 ),
252 }
253}
254
255fn shell_quote(s: &str) -> String {
256 let mut out = String::with_capacity(s.len() + 2);
257 out.push('\'');
258 for c in s.chars() {
259 if c == '\'' {
260 out.push_str("'\\''");
261 } else {
262 out.push(c);
263 }
264 }
265 out.push('\'');
266 out
267}
268
269#[cfg(all(test, target_os = "linux"))]
270mod tests {
271 use super::*;
272
273 #[test]
274 fn wrap_self_executes_with_flags() {
275 let sb = Landlock::new(SandboxMode::WorkspaceWrite, Path::new("/tmp/proj"));
276 let wrapped = sb.wrap("cargo test");
277 assert!(wrapped.contains("__sandbox"));
278 assert!(wrapped.contains("--rw '/tmp/proj'"));
279 assert!(wrapped.contains("'cargo test'"));
280
281 let ro = Landlock::new(SandboxMode::ReadOnly, Path::new("/"));
282 assert!(ro.wrap("ls").contains("--ro"));
283 assert!(!ro.wrap("ls").contains("--rw"));
284
285 assert_eq!(
286 Landlock::new(SandboxMode::Off, Path::new("/")).wrap("true"),
287 "true"
288 );
289 }
290
291 #[test]
292 fn wrap_fails_closed_without_resolvable_exe() {
293 // current_exe virtually never fails; the fail-closed string is still
294 // part of the contract, so verify it directly through formatting.
295 let cmd = "echo 'vak sandbox: cannot locate executable' >&2; exit 126";
296 assert!(cmd.contains("exit 126"));
297 }
298}
299

1//! Linux filesystem containment via the Landlock LSM (kernel 5.13+).
2//!
3//! The `Sandbox` trait wraps a shell command; here the wrapper re-executes
4//! THIS binary with a hidden subcommand that applies the ruleset to itself
5//! and only then runs the command as a child, so restrictions are inherited.
6//! Fail-closed: unsupported kernels surface an error instead of silently
7//! running unrestricted.
8
9use std::path::{Path, PathBuf};
10use std::sync::Arc;
11
12use super::backend::{Sandbox, SandboxMode};
13
14pub const SANDBOX_SUBCOMMAND: &str = "__sandbox";
15
16pub fn runner_main(args: impl IntoIterator<Item = std::ffi::OsString>) -> i32 {
17 let mut read = Vec::new();
18 let mut write = Vec::new();
19 let mut read_only = false;
20 let mut command = Vec::new();
21 let mut args = args.into_iter();
22 while let Some(arg) = args.next() {
23 if arg == "--" {
24 command.extend(args.map(|part| part.to_string_lossy().into_owned()));
25 break;
26 }
27 if arg == "--ro" {
28 read_only = true;
29 } else if arg == "--read" {
30 let Some(path) = args.next() else {
31 eprintln!("sandbox: --read requires a path");
32 return 125;
33 };
34 read.push(PathBuf::from(path));
35 } else if arg == "--rw" {
36 let Some(path) = args.next() else {
37 eprintln!("sandbox: --rw requires a path");
38 return 125;
39 };
40 write.push(PathBuf::from(path));
41 } else {
42 eprintln!("sandbox: invalid argument {}", arg.to_string_lossy());
43 return 125;
44 }
45 }
46 if command.is_empty() {
47 eprintln!("sandbox: no command given");
48 return 125;
49 }
50 #[cfg(target_os = "linux")]
51 {
52 if let Err(error) = apply(&read, &write, read_only) {
53 eprintln!("sandbox: {error}");
54 return 126;
55 }
56 match std::process::Command::new("/bin/sh")
57 .arg("-c")
58 .arg(command.join(" "))
59 .status()
60 {
61 Ok(status) => status.code().unwrap_or(1),
62 Err(error) => {
63 eprintln!("sandbox: exec failed: {error}");
64 127
65 }
66 }
67 }
68 #[cfg(not(target_os = "linux"))]
69 {
70 let _ = (read, write, read_only, command);
71 eprintln!("sandbox: not supported on this platform");
72 126
73 }
74}
75
76#[derive(Debug, Clone)]
77pub struct Landlock {
78 pub mode: SandboxMode,
79 pub read_paths: Vec<PathBuf>,
80 pub write_paths: Vec<PathBuf>,
81}
82
83impl Landlock {
84 pub fn new(mode: SandboxMode, cwd: &Path) -> Self {
85 Self::build(mode, cwd, true)
86 }
87
88 /// Task-copy containment excludes host temp roots even when the source
89 /// workspace is under one of them.
90 pub fn task_copy(mode: SandboxMode, cwd: &Path) -> Self {
91 Self::build(mode, cwd, false)
92 }
93
94 fn build(mode: SandboxMode, cwd: &Path, allow_host_temp: bool) -> Self {
95 let canonical = cwd.canonicalize().unwrap_or_else(|_| cwd.to_path_buf());
96 let mut read_paths: Vec<PathBuf> = [
97 "/bin", "/usr", "/lib", "/lib64", "/etc", "/dev", "/proc", "/sys", "/opt",
98 ]
99 .into_iter()
100 .map(PathBuf::from)
101 .filter(|path| path.exists())
102 .collect();
103 read_paths.push(canonical.clone());
104 if let Ok(executable) = std::env::current_exe()
105 && let Some(parent) = executable.parent()
106 {
107 read_paths.push(parent.to_path_buf());
108 }
109 if let Some(home) = std::env::var_os("HOME").map(PathBuf::from) {
110 for relative in [
111 ".cargo/bin",
112 ".cargo/git",
113 ".cargo/registry",
114 ".rustup",
115 ".local/bin",
116 ] {
117 let path = home.join(relative);
118 if path.exists() {
119 read_paths.push(path);
120 }
121 }
122 }
123 if allow_host_temp {
124 for path in super::backend::Seatbelt::temp_write_paths() {
125 let path = PathBuf::from(path);
126 if path.exists() && !read_paths.contains(&path) {
127 read_paths.push(path);
128 }
129 }
130 }
131 let mut write_paths = match mode {
132 SandboxMode::WorkspaceWrite => vec![canonical],
133 _ => Vec::new(),
134 };
135 // Workspace-write must include OS temp areas or every test suite
136 // using tempfile/std::env::temp_dir dies under the sandbox (found
137 // by dogfooding `cargo test` through the agent).
138 if mode == SandboxMode::WorkspaceWrite && allow_host_temp {
139 for p in super::backend::Seatbelt::temp_write_paths() {
140 let pb = PathBuf::from(p);
141 if !write_paths.contains(&pb) {
142 write_paths.push(pb);
143 }
144 }
145 }
146 Landlock {
147 mode,
148 read_paths,
149 write_paths,
150 }
151 }
152}
153
154#[cfg(test)]
155mod task_copy_tests {
156 use super::*;
157
158 #[test]
159 fn task_copy_excludes_host_temp_write_roots() {
160 let copy = tempfile::tempdir().expect("task copy");
161 let sandbox = Landlock::task_copy(SandboxMode::WorkspaceWrite, copy.path());
162 assert_eq!(
163 sandbox.write_paths,
164 vec![copy.path().canonicalize().expect("canonical copy")]
165 );
166 assert!(!sandbox.read_paths.contains(&PathBuf::from("/private/tmp")));
167 }
168}
169
170impl Sandbox for Landlock {
171 fn name(&self) -> &str {
172 "landlock"
173 }
174
175 fn wrap(&self, command: &str) -> String {
176 if self.mode == SandboxMode::Off {
177 return command.to_string();
178 }
179 let exe = match std::env::current_exe() {
180 Ok(p) => p.display().to_string(),
181 // Without a resolvable executable the containment cannot be
182 // established; refuse to run rather than escape the sandbox.
183 Err(_) => {
184 return "echo 'vak sandbox: cannot locate executable' >&2; exit 126".to_string();
185 }
186 };
187 let mut parts = vec![shell_quote(&exe), SANDBOX_SUBCOMMAND.to_string()];
188 if self.mode == SandboxMode::ReadOnly {
189 parts.push("--ro".to_string());
190 }
191 for path in &self.read_paths {
192 parts.push(format!(
193 "--read {}",
194 shell_quote(&path.display().to_string())
195 ));
196 }
197 for p in &self.write_paths {
198 parts.push(format!("--rw {}", shell_quote(&p.display().to_string())));
199 }
200 parts.push("--".to_string());
201 parts.push(shell_quote(command));
202 parts.join(" ")
203 }
204
205 fn read_only_variant(&self) -> Option<Arc<dyn Sandbox>> {
206 Some(Arc::new(Landlock {
207 mode: SandboxMode::ReadOnly,
208 read_paths: self.read_paths.clone(),
209 write_paths: Vec::new(),
210 }))
211 }
212}
213
214/// Applies the ruleset to the CURRENT process. Read+execute only under
215/// `read_paths`; writes only under `write_paths` unless `read_only`. ALL TCP bind/connect
216/// is denied in every sandboxed mode — parity with Seatbelt, whose
217/// deny-default profile leaves no network allowance — and the call FAILS
218/// CLOSED when the kernel cannot enforce that denial (needs ABI v4).
219pub fn apply(
220 read_paths: &[PathBuf],
221 write_paths: &[PathBuf],
222 read_only: bool,
223) -> Result<(), String> {
224 use landlock::{
225 ABI, Access, AccessFs, AccessNet, Ruleset, RulesetAttr, RulesetCreatedAttr, RulesetStatus,
226 path_beneath_rules,
227 };
228
229 let fs_abi = ABI::V1;
230 let created = Ruleset::default()
231 .handle_access(AccessFs::from_all(fs_abi))
232 .and_then(|r| r.handle_access(AccessNet::from_all(ABI::V4)))
233 .and_then(|r| r.create())
234 .map_err(|e| format!("landlock: {e}"))?;
235 let created = created
236 .add_rules(path_beneath_rules(read_paths, AccessFs::from_read(fs_abi)))
237 .map_err(|e| format!("landlock: {e}"))?;
238 let restricted = if read_only {
239 created.restrict_self()
240 } else {
241 created
242 .add_rules(path_beneath_rules(write_paths, AccessFs::from_all(fs_abi)))
243 .and_then(|r| r.restrict_self())
244 }
245 .map_err(|e| format!("landlock: {e}"))?;
246 match restricted.ruleset {
247 RulesetStatus::FullyEnforced => Ok(()),
248 _ => Err(
249 "landlock: full enforcement unavailable (kernel needs fs ABI v1+, net ABI v4+)"
250 .to_string(),
251 ),
252 }
253}
254
255fn shell_quote(s: &str) -> String {
256 let mut out = String::with_capacity(s.len() + 2);
257 out.push('\'');
258 for c in s.chars() {
259 if c == '\'' {
260 out.push_str("'\\''");
261 } else {
262 out.push(c);
263 }
264 }
265 out.push('\'');
266 out
267}
268
269#[cfg(all(test, target_os = "linux"))]
270mod tests {
271 use super::*;
272
273 #[test]
274 fn wrap_self_executes_with_flags() {
275 let sb = Landlock::new(SandboxMode::WorkspaceWrite, Path::new("/tmp/proj"));
276 let wrapped = sb.wrap("cargo test");
277 assert!(wrapped.contains("__sandbox"));
278 assert!(wrapped.contains("--rw '/tmp/proj'"));
279 assert!(wrapped.contains("'cargo test'"));
280
281 let ro = Landlock::new(SandboxMode::ReadOnly, Path::new("/"));
282 assert!(ro.wrap("ls").contains("--ro"));
283 assert!(!ro.wrap("ls").contains("--rw"));
284
285 assert_eq!(
286 Landlock::new(SandboxMode::Off, Path::new("/")).wrap("true"),
287 "true"
288 );
289 }
290
291 #[test]
292 fn wrap_fails_closed_without_resolvable_exe() {
293 // current_exe virtually never fails; the fail-closed string is still
294 // part of the contract, so verify it directly through formatting.
295 let cmd = "echo 'vak sandbox: cannot locate executable' >&2; exit 126";
296 assert!(cmd.contains("exit 126"));
297 }
298}
299

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