Initial reorg.
This is largely the same as #305, but updated for the current tree.
This commit is contained in:
Dan Gohman
213
crates/wasi-common/src/hostcalls_impl/fs_helpers.rs
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213
crates/wasi-common/src/hostcalls_impl/fs_helpers.rs
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@@ -0,0 +1,213 @@
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#![allow(non_camel_case_types)]
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use crate::sys::host_impl;
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use crate::sys::hostcalls_impl::fs_helpers::*;
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use crate::{fdentry::FdEntry, wasi, Error, Result};
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use std::fs::File;
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use std::path::{Component, Path};
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#[derive(Debug)]
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pub(crate) struct PathGet {
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dirfd: File,
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path: String,
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}
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impl PathGet {
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pub(crate) fn dirfd(&self) -> &File {
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&self.dirfd
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}
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pub(crate) fn path(&self) -> &str {
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&self.path
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}
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}
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/// Normalizes a path to ensure that the target path is located under the directory provided.
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///
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/// This is a workaround for not having Capsicum support in the OS.
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pub(crate) fn path_get(
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fe: &FdEntry,
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rights_base: wasi::__wasi_rights_t,
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rights_inheriting: wasi::__wasi_rights_t,
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dirflags: wasi::__wasi_lookupflags_t,
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path: &str,
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needs_final_component: bool,
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) -> Result<PathGet> {
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const MAX_SYMLINK_EXPANSIONS: usize = 128;
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if path.contains('\0') {
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// if contains NUL, return EILSEQ
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return Err(Error::EILSEQ);
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}
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if fe.file_type != wasi::__WASI_FILETYPE_DIRECTORY {
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// if `dirfd` doesn't refer to a directory, return `ENOTDIR`.
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return Err(Error::ENOTDIR);
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}
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let dirfd = fe
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.as_descriptor(rights_base, rights_inheriting)?
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.as_file()?
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.try_clone()?;
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// Stack of directory file descriptors. Index 0 always corresponds with the directory provided
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// to this function. Entering a directory causes a file descriptor to be pushed, while handling
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// ".." entries causes an entry to be popped. Index 0 cannot be popped, as this would imply
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// escaping the base directory.
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let mut dir_stack = vec![dirfd];
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// Stack of paths left to process. This is initially the `path` argument to this function, but
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// any symlinks we encounter are processed by pushing them on the stack.
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let mut path_stack = vec![path.to_owned()];
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// Track the number of symlinks we've expanded, so we can return `ELOOP` after too many.
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let mut symlink_expansions = 0;
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// TODO: rewrite this using a custom posix path type, with a component iterator that respects
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// trailing slashes. This version does way too much allocation, and is way too fiddly.
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loop {
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match path_stack.pop() {
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Some(cur_path) => {
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log::debug!("path_get cur_path = {:?}", cur_path);
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let ends_with_slash = cur_path.ends_with('/');
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let mut components = Path::new(&cur_path).components();
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let head = match components.next() {
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None => return Err(Error::ENOENT),
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Some(p) => p,
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};
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let tail = components.as_path();
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if tail.components().next().is_some() {
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let mut tail = host_impl::path_from_host(tail.as_os_str())?;
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if ends_with_slash {
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tail.push('/');
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}
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path_stack.push(tail);
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}
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log::debug!("path_get path_stack = {:?}", path_stack);
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match head {
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Component::Prefix(_) | Component::RootDir => {
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// path is absolute!
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return Err(Error::ENOTCAPABLE);
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}
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Component::CurDir => {
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// "." so skip
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}
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Component::ParentDir => {
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// ".." so pop a dir
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let _ = dir_stack.pop().ok_or(Error::ENOTCAPABLE)?;
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// we're not allowed to pop past the original directory
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if dir_stack.is_empty() {
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return Err(Error::ENOTCAPABLE);
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}
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}
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Component::Normal(head) => {
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let mut head = host_impl::path_from_host(head)?;
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if ends_with_slash {
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// preserve trailing slash
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head.push('/');
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}
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if !path_stack.is_empty() || (ends_with_slash && !needs_final_component) {
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match openat(dir_stack.last().ok_or(Error::ENOTCAPABLE)?, &head) {
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Ok(new_dir) => {
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dir_stack.push(new_dir);
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}
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Err(e) => {
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match e.as_wasi_errno() {
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wasi::__WASI_ELOOP
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| wasi::__WASI_EMLINK
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| wasi::__WASI_ENOTDIR =>
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// Check to see if it was a symlink. Linux indicates
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// this with ENOTDIR because of the O_DIRECTORY flag.
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{
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// attempt symlink expansion
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let mut link_path = readlinkat(
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dir_stack.last().ok_or(Error::ENOTCAPABLE)?,
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&head,
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)?;
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symlink_expansions += 1;
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if symlink_expansions > MAX_SYMLINK_EXPANSIONS {
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return Err(Error::ELOOP);
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}
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if head.ends_with('/') {
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link_path.push('/');
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}
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log::debug!(
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"attempted symlink expansion link_path={:?}",
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link_path
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);
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path_stack.push(link_path);
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}
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_ => {
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return Err(e);
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}
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}
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}
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}
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continue;
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} else if ends_with_slash
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|| (dirflags & wasi::__WASI_LOOKUP_SYMLINK_FOLLOW) != 0
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{
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// if there's a trailing slash, or if `LOOKUP_SYMLINK_FOLLOW` is set, attempt
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// symlink expansion
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match readlinkat(dir_stack.last().ok_or(Error::ENOTCAPABLE)?, &head) {
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Ok(mut link_path) => {
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symlink_expansions += 1;
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if symlink_expansions > MAX_SYMLINK_EXPANSIONS {
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return Err(Error::ELOOP);
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}
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if head.ends_with('/') {
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link_path.push('/');
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}
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log::debug!(
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"attempted symlink expansion link_path={:?}",
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link_path
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);
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path_stack.push(link_path);
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continue;
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}
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Err(e) => {
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if e.as_wasi_errno() != wasi::__WASI_EINVAL
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&& e.as_wasi_errno() != wasi::__WASI_ENOENT
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// this handles the cases when trying to link to
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// a destination that already exists, and the target
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// path contains a slash
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&& e.as_wasi_errno() != wasi::__WASI_ENOTDIR
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{
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return Err(e);
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}
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}
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}
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}
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// not a symlink, so we're done;
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return Ok(PathGet {
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dirfd: dir_stack.pop().ok_or(Error::ENOTCAPABLE)?,
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path: head,
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});
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}
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}
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}
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None => {
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// no further components to process. means we've hit a case like "." or "a/..", or if the
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// input path has trailing slashes and `needs_final_component` is not set
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return Ok(PathGet {
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dirfd: dir_stack.pop().ok_or(Error::ENOTCAPABLE)?,
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path: String::from("."),
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});
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}
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}
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}
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}
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