GHSA-p799-g7vv-f279 Romeo is vulnerable to Archive Slip due to missing checks in sanitization

• Go github.com/ctfer-io/romeo/webserver: < 0.2.2 → fixed in 0.2.2

Summary The `sanitizeArchivePath` function in `webserver/api/v1/decoder.go` (lines 80-88) is vulnerable to a path traversal bypass due to a missing trailing path separator in the `strings.HasPrefix` check. A crafted tar archive can write files outside the intended destination directory. Vulnerable Code File: `webserver/api/v1/decoder.go`, lines 80-88 ```go func sanitizeArchivePath(d, t string) (v string, err error) { v = filepath.Join(d, t) if strings.HasPrefix(v, filepath.Clean(d)) { return v, nil } return "", &ErrPathTainted{ Path: t, } } ``` The function is called at line 48 inside `[*Decompressor].Unzip`, which is invoked by `Decode` (line 80) during execution of the webserver CLI (command `download`). Root Cause `strings.HasPrefix(v, filepath.Clean(d))` does not append a trailing `/` to the directory prefix, causing a directory name prefix collision. If the destination is `/home/user/extract-output` and a tar entry is named `../extract-outputevil/pwned`, the joined path `/home/user/extract-outputevil/pwned` passes the prefix check — it starts with `/home/user/extract-output` — even though it is entirely outside the intended directory. Steps to Reproduce 1. Deploy Romeo. A measured app writes its coverage data. 2. Place the PoC zip on the PVC. Any pod with write access to the `ReadWriteMany` PVC (or the webserver itself) copies a `poc-path-traversal.tar` into the `coverdir` mount path. The archive contains legitimate coverage files alongside two crafted entries with path-traversal names. 3. Run the webserver CLI against the running webserver: ``` webserver download \ --server http://localhost:8080 \ --directory /home/user/extract-output ``` 4. Observe the bypass. `unzip` processes the zip stream. For the malicious entries: ``` // entry name: ../extract-outputevil/poc-proof.txt filepath.Join("/home/user/extract-output", "../extract-outputevil/poc-proof.txt") => "/home/user/extract-outputevil/poc-proof.txt" strings.HasPrefix("/home/user/extract-outputevil/poc-proof.txt", "/home/user/extract-output") => true // BUG: prefix collision; file lands OUTSIDE target dir ``` Both malicious entries are written outside `/home/user/extract-output/`. The legitimate coverage files land correctly inside it. Impact Successful exploitation gives an attacker arbitrary file write on the machine running the webserver CLI. Real-world primitives include: • Overwriting `~/.bashrc` / `~/.zshrc` / `~/.profile` for RCE on next shell login • Appending to `~/.ssh/authorized_keys` for persistent SSH backdoor • Dropping a malicious entry into `~/.kube/config` to hijack cluster access • Writing crontab entries for persistent scheduled execution The attack surface is widened by the default `ReadWriteMany` PVC access mode, which means any pod in the cluster with the PVC mounted can inject the payload — not just the Romeo webserver itself.