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use crate::entry::Entry;
use crate::handle::{Fdflags, Filetype, Handle, HandleRights, Lookupflags, Oflags};
use crate::{Error, Result};
use std::path::{Component, Path};
use std::str;
pub(crate) use crate::sys::path::{from_host, open_rights};
/// Normalizes a path to ensure that the target path is located under the directory provided.
///
/// This is a workaround for not having Capsicum support in the OS.
pub(crate) fn get(
entry: &Entry,
required_rights: &HandleRights,
dirflags: Lookupflags,
path: &str,
needs_final_component: bool,
) -> Result<(Box<dyn Handle>, String)> {
const MAX_SYMLINK_EXPANSIONS: usize = 128;
tracing::trace!(path = path);
if path.contains('\0') {
// if contains NUL, return Ilseq
return Err(Error::Ilseq);
}
if entry.get_file_type() != Filetype::Directory {
// if `dirfd` doesn't refer to a directory, return `Notdir`.
return Err(Error::Notdir);
}
let handle = entry.as_handle(required_rights)?;
let dirfd = handle.try_clone()?;
// Stack of directory file descriptors. Index 0 always corresponds with the directory provided
// to this function. Entering a directory causes a file descriptor to be pushed, while handling
// ".." entries causes an entry to be popped. Index 0 cannot be popped, as this would imply
// escaping the base directory.
let mut dir_stack = vec![dirfd];
// Stack of paths left to process. This is initially the `path` argument to this function, but
// any symlinks we encounter are processed by pushing them on the stack.
let mut path_stack = vec![path.to_owned()];
// Track the number of symlinks we've expanded, so we can return `ELOOP` after too many.
let mut symlink_expansions = 0;
// TODO: rewrite this using a custom posix path type, with a component iterator that respects
// trailing slashes. This version does way too much allocation, and is way too fiddly.
loop {
match path_stack.pop() {
Some(cur_path) => {
tracing::debug!(cur_path = tracing::field::display(&cur_path), "path get");
let ends_with_slash = cur_path.ends_with('/');
let mut components = Path::new(&cur_path).components();
let head = match components.next() {
None => return Err(Error::Noent),
Some(p) => p,
};
let tail = components.as_path();
if tail.components().next().is_some() {
let mut tail = from_host(tail.as_os_str())?;
if ends_with_slash {
tail.push('/');
}
path_stack.push(tail);
}
tracing::debug!(path_stack = tracing::field::debug(&path_stack), "path_get");
match head {
Component::Prefix(_) | Component::RootDir => {
// path is absolute!
return Err(Error::Notcapable);
}
Component::CurDir => {
// "." so skip
}
Component::ParentDir => {
// ".." so pop a dir
let _ = dir_stack.pop().ok_or(Error::Notcapable)?;
// we're not allowed to pop past the original directory
if dir_stack.is_empty() {
return Err(Error::Notcapable);
}
}
Component::Normal(head) => {
let mut head = from_host(head)?;
if ends_with_slash {
// preserve trailing slash
head.push('/');
}
if !path_stack.is_empty() || (ends_with_slash && !needs_final_component) {
let fd = dir_stack.last().ok_or(Error::Notcapable)?;
match fd.openat(
&head,
false,
false,
Oflags::DIRECTORY,
Fdflags::empty(),
) {
Ok(new_dir) => {
dir_stack.push(new_dir);
}
Err(e) => {
match e {
Error::Loop | Error::Mlink | Error::Notdir =>
// Check to see if it was a symlink. Linux indicates
// this with ENOTDIR because of the O_DIRECTORY flag.
{
// attempt symlink expansion
let fd = dir_stack.last().ok_or(Error::Notcapable)?;
let mut link_path = fd.readlinkat(&head)?;
symlink_expansions += 1;
if symlink_expansions > MAX_SYMLINK_EXPANSIONS {
return Err(Error::Loop);
}
if head.ends_with('/') {
link_path.push('/');
}
tracing::debug!(
"attempted symlink expansion link_path={:?}",
link_path
);
path_stack.push(link_path);
}
_ => {
return Err(e);
}
}
}
}
continue;
} else if ends_with_slash || dirflags.contains(&Lookupflags::SYMLINK_FOLLOW)
{
// if there's a trailing slash, or if `LOOKUP_SYMLINK_FOLLOW` is set, attempt
// symlink expansion
let fd = dir_stack.last().ok_or(Error::Notcapable)?;
match fd.readlinkat(&head) {
Ok(mut link_path) => {
symlink_expansions += 1;
if symlink_expansions > MAX_SYMLINK_EXPANSIONS {
return Err(Error::Loop);
}
if head.ends_with('/') {
link_path.push('/');
}
tracing::debug!(
"attempted symlink expansion link_path={:?}",
link_path
);
path_stack.push(link_path);
continue;
}
Err(Error::Inval) | Err(Error::Noent) | Err(Error::Notdir) => {
// this handles the cases when trying to link to
// a destination that already exists, and the target
// path contains a slash
}
Err(e) => {
return Err(e);
}
}
}
// not a symlink, so we're done;
return Ok((dir_stack.pop().ok_or(Error::Notcapable)?, head));
}
}
}
None => {
// no further components to process. means we've hit a case like "." or "a/..", or if the
// input path has trailing slashes and `needs_final_component` is not set
return Ok((dir_stack.pop().ok_or(Error::Notcapable)?, String::from(".")));
}
}
}
}