Monitoring is vulnerable to Archive Slip due to missing checks in sanitization

The sanitizeArchivePath function in pkg/extract/extract.go (lines 248–254) 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 when using the extractor CLI tool or the extract.DumpOTelCollector library function.

Vulnerable Code

File: pkg/extract/extract.go, lines 248–254

func sanitizeArchivePath(d, t string) (v string, err error) {
    v = filepath.Join(d, t)
    if strings.HasPrefix(v, filepath.Clean(d)) {   // ← missing trailing separator
        return v, nil
    }
    return "", fmt.Errorf("filepath is tainted: %s", t)
}

The function is called at line 219 inside untar, which is invoked by copyFromPod (line 205) during the Cold Extract data dump workflow.

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 the monitoring stack with ColdExtract: true. The OTEL Collector begins writing signal data (otel_traces, otel_metrics, otel_logs) to the shared PVC.

2. Place the PoC tar on the PVC. Any pod with write access to the ReadWriteMany PVC (or the compromised OTEL Collector itself) copies a poc-path-traversal.tar into the /data/collector mount path. The archive contains three real-looking OTLP telemetry files alongside two crafted entries with path-traversal names.

3. Run the extractor against the namespace:

   extractor \
     --namespace monitoring \
     --pvc-name <signals-pvc-name> \
     --directory /home/user/extract-output
   

4. Observe the bypass. untar processes the tar 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 three legitimate OTLP files land correctly inside it.

Impact

Successful exploitation gives an attacker arbitrary file write on the machine running the extractor. 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 OTEL Collector itself.