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fix: check directory traversal attack without file system visit #473

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merged 1 commit into from
Apr 25, 2020
Merged

fix: check directory traversal attack without file system visit #473

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54 changes: 25 additions & 29 deletions src/server/serve_dir.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ use crate::{Body, Endpoint, Request, Response, Result, StatusCode};
use async_std::fs::File;
use async_std::io::BufReader;

use std::ffi::OsStr;
use std::path::{Path, PathBuf};

type BoxFuture<'a, T> = std::pin::Pin<Box<dyn std::future::Future<Output = T> + 'a + Send>>;
Expand All @@ -22,43 +23,38 @@ impl ServeDir {
impl<State> Endpoint<State> for ServeDir {
fn call<'a>(&'a self, req: Request<State>) -> BoxFuture<'a, Result> {
let path = req.uri().path();
let path = path.replacen(&self.prefix, "", 1);
let path = path.trim_start_matches(&self.prefix);
let path = path.trim_start_matches('/');
let mut dir = self.dir.clone();
let mut file_path = self.dir.clone();
for p in Path::new(path) {
dir.push(&p);
if p == OsStr::new(".") {
continue;
} else if p == OsStr::new("..") {
file_path.pop();
} else {
file_path.push(&p);
}
}
log::info!("Requested file: {:?}", dir);

log::info!("Requested file: {:?}", file_path);
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Ideally we could warn here with the full requested path if it contained a .. instead.


Box::pin(async move {
let file = match async_std::fs::canonicalize(&dir).await {
Err(_) => {
// This needs to return the same status code as the
// unauthorized case below to ensure we don't leak
// information of which files exist to adversaries.
log::warn!("File not found: {:?}", dir);
return Ok(Response::new(StatusCode::NotFound));
}
Ok(mut file_path) => {
// Verify this is a sub-path of the original dir.
let mut file_iter = (&mut file_path).iter();
if !dir.iter().all(|lhs| Some(lhs) == file_iter.next()) {
// This needs to return the same status code as the
// 404 case above to ensure we don't leak
// information about the local fs to adversaries.
log::warn!("Unauthorized attempt to read: {:?}", file_path);
return Ok(Response::new(StatusCode::NotFound));
}
if !file_path.starts_with(&self.dir) {
log::warn!("Unauthorized attempt to read: {:?}", file_path);
return Ok(Response::new(StatusCode::Forbidden));
}

// Open the file and send back the contents.
match File::open(&file_path).await {
Ok(file) => file,
Err(_) => {
log::warn!("Could not open {:?}", file_path);
return Ok(Response::new(StatusCode::InternalServerError));
}
let file = match File::open(&file_path).await {
Err(error) => {
return if error.kind() == async_std::io::ErrorKind::NotFound {
log::warn!("File not found: {:?}", file_path);
Ok(Response::new(StatusCode::NotFound))
} else {
log::warn!("Could not open {:?}", file_path);
Ok(Response::new(StatusCode::InternalServerError))
}
}
Ok(file) => file,
};

let len = match file.metadata().await {
Expand Down