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feat(sandbox): Landlock TCP port restriction for mandatory proxy #16

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feat(sandbox): Landlock TCP port restriction for mandatory proxy #16

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56 changes: 52 additions & 4 deletions crates/openshell-sandbox/src/sandbox/linux/landlock.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,10 +3,10 @@

//! Landlock filesystem sandboxing.

use crate::policy::{LandlockCompatibility, SandboxPolicy};
use crate::policy::{LandlockCompatibility, NetworkMode, SandboxPolicy};
use landlock::{
ABI, Access, AccessFs, CompatLevel, Compatible, PathBeneath, PathFd, PathFdError, Ruleset,
RulesetAttr, RulesetCreatedAttr,
ABI, Access, AccessFs, AccessNet, CompatLevel, Compatible, NetPort, PathBeneath, PathFd,
PathFdError, Ruleset, RulesetAttr, RulesetCreatedAttr,
};
use miette::{IntoDiagnostic, Result};
use std::path::{Path, PathBuf};
Expand Down Expand Up @@ -184,6 +184,26 @@ pub fn prepare(policy: &SandboxPolicy, workdir: Option<&str>) -> Result<Option<P
.handle_access(access_all)
.into_diagnostic()?;

// Platform mode: declare intent to handle TCP connect access.
// Caught independently -- filesystem sandboxing continues even if
// TCP port restriction is unavailable (ABI < v4).
let mut tcp_handled = false;
if matches!(policy.network.mode, NetworkMode::Platform) {
match ruleset.handle_access(AccessNet::ConnectTcp) {
Ok(r) => {
ruleset = r;
tcp_handled = true;
}
Err(e) => {
tracing::warn!(
error = %e,
"Landlock handle_access(ConnectTcp) failed (ABI v4 required). \
TCP port restriction will not be applied."
);
}
}
}

let mut ruleset = ruleset.create().into_diagnostic()?;
let mut rules_applied: usize = 0;

Expand All @@ -207,6 +227,34 @@ pub fn prepare(policy: &SandboxPolicy, workdir: Option<&str>) -> Result<Option<P
}
}

if tcp_handled {
let proxy_port = policy
.network
.proxy
.as_ref()
.and_then(|p| p.http_addr)
.map_or(3128_u16, |addr| addr.port());

match ruleset.add_rule(NetPort::new(proxy_port, AccessNet::ConnectTcp)) {
Ok(r) => {
ruleset = r;
debug!(
port = proxy_port,
"Landlock allow TCP connect (proxy port only)"
);
rules_applied += 1;
}
Err(e) => {
tracing::warn!(
error = %e,
"Landlock TCP port restriction unavailable. \
Network enforcement degraded: agent can bypass proxy via direct \
connect(). Upgrade to RHEL 9.6+ for kernel-enforced TCP port restriction."
);
}
}
}

if rules_applied == 0 {
return Err(miette::miette!(
"Landlock ruleset has zero valid paths — all {} path(s) failed to open. \
Expand All @@ -215,7 +263,7 @@ pub fn prepare(policy: &SandboxPolicy, workdir: Option<&str>) -> Result<Option<P
));
}

let skipped = total_paths - rules_applied;
let skipped = total_paths.saturating_sub(rules_applied);
openshell_ocsf::ocsf_emit!(
openshell_ocsf::ConfigStateChangeBuilder::new(crate::ocsf_ctx())
.severity(openshell_ocsf::SeverityId::Informational)
Expand Down