tower_web/extract/
pathbuf.rs

1use extract::{Context, Error, Extract, Immediate};
2use std::ffi::{OsStr, OsString};
3use std::path::{self, Path, PathBuf};
4use util::buf_stream::BufStream;
5
6// https://www.owasp.org/index.php/Path_Traversal
7fn check_for_path_traversal(path: &Path) -> Result<(), Error> {
8    use self::path::Component::*;
9
10    let path_traversal_error = || Error::invalid_argument(&"Path traversal detected");
11
12    let mut depth = 0u32;
13    for c in path.components() {
14        match c {
15            Prefix(_) | RootDir => {
16                // Escaping to the root is immediately a failure
17                Err(path_traversal_error())?
18            }
19            CurDir => {
20                // no-op
21            }
22            ParentDir => {
23                depth = match depth.checked_sub(1) {
24                    Some(v) => v,
25                    None => Err(path_traversal_error())?,
26                }
27            }
28            Normal(_) => {
29                depth += 1;
30            }
31        }
32    }
33
34    Ok(())
35}
36
37fn decode(s: &OsStr) -> Result<PathBuf, Error> {
38    let path = PathBuf::from(s);
39    check_for_path_traversal(&path)?;
40    Ok(path)
41}
42
43impl<B: BufStream> Extract<B> for PathBuf {
44    type Future = Immediate<Self>;
45
46    fn extract(ctx: &Context) -> Self::Future {
47        use extract::ExtractFuture;
48
49        let s = <OsString as Extract<B>>::extract(ctx).extract();
50        Immediate::result(decode(&s))
51    }
52}
53
54#[cfg(test)]
55mod test {
56    use super::*;
57    use std::path::Path;
58
59    #[test]
60    fn extract() {
61        assert_eq!(
62            decode(OsStr::new("hello, world")).unwrap(),
63            Path::new("hello, world")
64        );
65    }
66
67    #[test]
68    fn disallows_path_traversal() {
69        assert!(decode(OsStr::new("/")).unwrap_err().is_invalid_argument());
70        assert!(decode(OsStr::new("..")).unwrap_err().is_invalid_argument());
71        assert_eq!(decode(OsStr::new("a/..")).unwrap(), Path::new("a/.."));
72        assert!(
73            decode(OsStr::new("../a"))
74                .unwrap_err()
75                .is_invalid_argument()
76        );
77        assert!(
78            decode(OsStr::new("../a/b"))
79                .unwrap_err()
80                .is_invalid_argument()
81        );
82        assert_eq!(decode(OsStr::new("a/../b")).unwrap(), Path::new("a/../b"));
83        assert_eq!(decode(OsStr::new("a/b/..")).unwrap(), Path::new("a/b/.."));
84    }
85}
tower_web/extract/pathbuf.rs

tower_web/extract/
pathbuf.rs
