Directory Traversal Affecting apache-airflow-providers-google package, versions [,22.2.0rc1)

apache-airflow-providers-google is a Provider for Apache Airflow. Implements apache-airflow-providers-google package

Affected versions of this package are vulnerable to Directory Traversal through GCSToSFTPOperator._resolve_destination_path in airflow/providers/google/cloud/transfers/gcs_to_sftp.py. An attacker can overwrite files outside the configured SFTP destination_path by uploading a GCS object whose name contains .. segments or an absolute path and then triggering the DAG run that copies it to SFTP. The operator joins the attacker-controlled object name directly onto the destination path without containment checks, so the resulting transfer can land at arbitrary locations on the SFTP server instead of the intended upload directory, putting files such as ~/.ssh/authorized_keys at risk.

Notes

• Affected deployments are the ones that let less-trusted principals write object names into the source GCS bucket; the operator uses those bucket-listing names directly, so partner uploads, ingest-only service accounts, or public-data buckets widen exposure.
• Relative destination_path values of . or "" map to the SFTP login/current directory, so containment is relative to that directory rather than a fixed subfolder when those settings are used.

A Directory Traversal attack (also known as path traversal) aims to access files and directories that are stored outside the intended folder. By manipulating files with "dot-dot-slash (../)" sequences and its variations, or by using absolute file paths, it may be possible to access arbitrary files and directories stored on file system, including application source code, configuration, and other critical system files.

Directory Traversal vulnerabilities can be generally divided into two types:

• Information Disclosure: Allows the attacker to gain information about the folder structure or read the contents of sensitive files on the system.

st is a module for serving static files on web pages, and contains a vulnerability of this type. In our example, we will serve files from the public route.

If an attacker requests the following URL from our server, it will in turn leak the sensitive private key of the root user.

curl http://localhost:8080/public/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/root/.ssh/id_rsa

Note %2e is the URL encoded version of . (dot).

• Writing arbitrary files: Allows the attacker to create or replace existing files. This type of vulnerability is also known as Zip-Slip.

One way to achieve this is by using a malicious zip archive that holds path traversal filenames. When each filename in the zip archive gets concatenated to the target extraction folder, without validation, the final path ends up outside of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicious file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:

2018-04-15 22:04:29 .....           19           19  good.txt
2018-04-15 22:04:42 .....           20           20  ../../../../../../root/.ssh/authorized_keys

• Apache Security Advisory
• GitHub Commit
• GitHub PR