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nvx-rs: lay out execution-helper configurations with one function #689

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Merged
Pedro Henrique Penna (ppenna) merged 1 commit into from
Oct 22, 2026
Merged

nvx-rs: lay out execution-helper configurations with one function #689

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83 changes: 36 additions & 47 deletions nvx-rs/src/guest/managed_agent/exec_config.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -50,16 +50,29 @@ fn encode(execution: &GuestExecPayload, cwd_entered: bool) -> Result<Vec<u8>, Er
if execution.inherit_default_env {
flags |= EXEC_INHERIT_DEFAULT_ENV;
}
let environment = execution.environment.as_deref().unwrap_or_default();
encode_fields(
flags,
cwd.unwrap_or_default(),
execution.environment.as_deref().unwrap_or_default(),
)
}

/// Lays out the private helper configuration format with `flags`, the working directory `cwd`,
/// empty without one, and the `environment` entries: the little-endian flags, entry count, and
/// working-directory length, then the working directory, then each entry after its
/// little-endian length. Tests also lay out configurations that [`encode`] never produces.
pub(super) fn encode_fields(
flags: u16,
cwd: &[u8],
environment: &[Vec<u8>],
) -> Result<Vec<u8>, Errno> {
let count = u16::try_from(environment.len()).map_err(|_| Errno::EOVERFLOW)?;
let cwd_len = u32::try_from(cwd.map_or(0, <[u8]>::len)).map_err(|_| Errno::EOVERFLOW)?;
let cwd_len = u32::try_from(cwd.len()).map_err(|_| Errno::EOVERFLOW)?;
let mut bytes = Vec::new();
bytes.extend_from_slice(&flags.to_le_bytes());
bytes.extend_from_slice(&count.to_le_bytes());
bytes.extend_from_slice(&cwd_len.to_le_bytes());
if let Some(cwd) = cwd {
bytes.extend_from_slice(cwd);
}
bytes.extend_from_slice(cwd);
for entry in environment {
let length = u32::try_from(entry.len()).map_err(|_| Errno::EOVERFLOW)?;
bytes.extend_from_slice(&length.to_le_bytes());
Expand Down Expand Up @@ -119,10 +132,20 @@ pub(crate) fn read(descriptor: &FileDescriptor) -> Result<HelperConfig, Errno> {
})
}

/// Returns a descriptor of a file that holds `bytes`, from which [`read`] reads a configuration
/// as it reads a sealed one.
#[cfg(test)]
mod tests {
pub(super) fn file_with(bytes: &[u8]) -> FileDescriptor {
use std::io::{Seek, Write};

let mut file = tempfile::tempfile().unwrap();
file.write_all(bytes).unwrap();
file.rewind().unwrap();
FileDescriptor::from_owned(file.into())
}

#[cfg(test)]
mod tests {
use super::*;

fn execution() -> GuestExecPayload {
Expand All @@ -135,13 +158,6 @@ mod tests {
}
}

fn file_with(bytes: &[u8]) -> FileDescriptor {
let mut file = tempfile::tempfile().unwrap();
file.write_all(bytes).unwrap();
file.rewind().unwrap();
FileDescriptor::from_owned(file.into())
}

#[test]
fn helper_configuration_round_trips_empty_exact_and_large_environments() {
for environment in [
Expand Down Expand Up @@ -178,40 +194,13 @@ mod tests {
#[test]
fn helper_defensively_rejects_unknown_flags_and_malformed_environment() {
for bytes in [
{
let mut bytes = Vec::new();
bytes.extend_from_slice(&0x4000u16.to_le_bytes());
bytes.extend_from_slice(&0u16.to_le_bytes());
bytes.extend_from_slice(&0u32.to_le_bytes());
bytes
},
{
let mut bytes = Vec::new();
bytes.extend_from_slice(&EXEC_ENVIRONMENT_PRESENT.to_le_bytes());
bytes.extend_from_slice(&1u16.to_le_bytes());
bytes.extend_from_slice(&0u32.to_le_bytes());
bytes.extend_from_slice(&9u32.to_le_bytes());
bytes.extend_from_slice(b"NO_EQUALS");
bytes
},
{
let mut bytes = Vec::new();
bytes.extend_from_slice(&EXEC_ENVIRONMENT_PRESENT.to_le_bytes());
bytes.extend_from_slice(&1u16.to_le_bytes());
bytes.extend_from_slice(&0u32.to_le_bytes());
bytes.extend_from_slice(&6u32.to_le_bytes());
bytes.extend_from_slice(b"=value");
bytes
},
{
let mut bytes = Vec::new();
bytes.extend_from_slice(&EXEC_CWD_ENTERED.to_le_bytes());
bytes.extend_from_slice(&0u16.to_le_bytes());
bytes.extend_from_slice(&1u32.to_le_bytes());
bytes.push(b'/');
bytes
},
] {
encode_fields(0x4000, b"", &[]),
encode_fields(EXEC_ENVIRONMENT_PRESENT, b"", &[b"NO_EQUALS".to_vec()]),
encode_fields(EXEC_ENVIRONMENT_PRESENT, b"", &[b"=value".to_vec()]),
encode_fields(EXEC_CWD_ENTERED, b"/", &[]),
]
.map(Result::unwrap)
{
let descriptor = file_with(&bytes);
assert!(read(&descriptor).is_err(), "{bytes:?}");
}
Expand Down
32 changes: 9 additions & 23 deletions nvx-rs/src/guest/managed_agent/helper.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -133,8 +133,6 @@ pub(crate) fn safe_path(path: &[u8]) -> bool {

#[cfg(test)]
mod tests {
use std::io::{Seek, Write};

use crate::guest::sys::FileDescriptor;
use crate::protocol::{self, GuestExecPayload};

Expand Down Expand Up @@ -166,13 +164,6 @@ mod tests {
arguments
}

fn file_with(bytes: &[u8]) -> FileDescriptor {
let mut file = tempfile::tempfile().unwrap();
file.write_all(bytes).unwrap();
file.rewind().unwrap();
FileDescriptor::from_owned(file.into())
}

/// Returns the inherited environment without the helper's descriptor variable.
fn inherited() -> Vec<Vec<u8>> {
let mut environment = environment::inherited().unwrap();
Expand Down Expand Up @@ -224,26 +215,21 @@ mod tests {
);
assert!(system.execs.is_empty());

let mut relative = Vec::new();
relative.extend_from_slice(&protocol::EXEC_CWD_PRESENT.to_le_bytes());
relative.extend_from_slice(&0u16.to_le_bytes());
relative.extend_from_slice(&1u32.to_le_bytes());
relative.push(b'.');
let fd = file_with(&relative);
let relative = exec_config::encode_fields(protocol::EXEC_CWD_PRESENT, b".", &[]).unwrap();
let fd = exec_config::file_with(&relative);
let helper_arguments = arguments(&mut system, fd, &[b"/bin/pwd"]);
assert_eq!(
run(&mut system, &helper_arguments),
Err(CommandError::Agent)
);

let mut conflicting = Vec::new();
conflicting.extend_from_slice(
&(protocol::EXEC_CWD_PRESENT | exec_config::EXEC_CWD_ENTERED).to_le_bytes(),
);
conflicting.extend_from_slice(&0u16.to_le_bytes());
conflicting.extend_from_slice(&1u32.to_le_bytes());
conflicting.push(b'/');
let fd = file_with(&conflicting);
let conflicting = exec_config::encode_fields(
protocol::EXEC_CWD_PRESENT | exec_config::EXEC_CWD_ENTERED,
b"/",
&[],
)
.unwrap();
let fd = exec_config::file_with(&conflicting);
let helper_arguments = arguments(&mut system, fd, &[b"/bin/pwd"]);
assert_eq!(
run(&mut system, &helper_arguments),
Expand Down
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