Crate proc_canonicalize 

proc-canonicalize

A patch for std::fs::canonicalize that preserves Linux /proc/PID/root and /proc/PID/cwd namespace boundaries.

The Problem

On Linux, /proc/PID/root is a “magic symlink” that crosses into a process’s mount namespace. However, std::fs::canonicalize resolves it to /, losing the namespace context:

std::fs::canonicalize("/proc/1234/root")           -> "/"
std::fs::canonicalize("/proc/1234/root/etc/passwd") -> "/etc/passwd"

This breaks security tools that use /proc/PID/root as a boundary for container filesystem access, because the boundary resolves to the host root!

The Fix

This crate detects /proc/PID/root and /proc/PID/cwd prefixes and preserves them:

proc_canonicalize::canonicalize("/proc/1234/root")           -> "/proc/1234/root"
proc_canonicalize::canonicalize("/proc/1234/root/etc/passwd") -> "/proc/1234/root/etc/passwd"

For all other paths, behavior is identical to std::fs::canonicalize.

Platform Support

• Linux: Full functionality - preserves /proc/PID/root and /proc/PID/cwd
• Other platforms: Falls back to std::fs::canonicalize (no-op)

Zero Dependencies

This crate has no dependencies beyond the Rust standard library.

Optional Features

• dunce (Windows only): Simplifies Windows extended-length paths by removing the \\?\ prefix when possible (e.g., \\?\C:\foo becomes C:\foo). This makes paths more readable but may lose some Windows path capabilities. Enable with features = ["dunce"] in your Cargo.toml.

Functions

canonicalize

Canonicalize a path, preserving Linux /proc/PID/root and /proc/PID/cwd boundaries.