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SecureDrop Workstation Gets Post-Audit Security Refresh

The open-source SecureDrop Workstation has undergone a security makeover after a third-party security audit flagged multiple problems, including a high-risk bug that could allow an attacker to plant files on target machines.

The SecureDrop Workstation audit, conducted by Trail of Bits and financed by the New York Times, warned that the high-risk directory traversal bug could be leveraged for code execution attacks.

“The high severity finding details case where a malicious SecureDrop server could create files in arbitrary paths in the sd-app VM, which may allow for a code execution,” according to the audit report [PDF].

“When the SecureDrop Workstation client downloads a file, it stores it in a location derived from the filename returned by the server. However, since this location is not sanitized properly in all cases, an attacker who controls responses from the server can make the client save files in arbitrary paths on the filesystem. An attacker can use this vulnerability to plant files that potentially enable further vulnerabilities.”

The Trail of Bits code auditors found two cases when a malicious SecureDrop server could plant files.

Overall, the security assessment gave SecureDrop workstation a positive security bill of health. 

“We were unable to achieve a direct compromise of the Workstation from the position of an Internet-based attacker during our engagement,” Trail of Bits said, but made it clear this doesn’t imply that such a compromise exists or that SecureDrop Workstation is free of bugs.

SecureDrop Workstation is currently managed by the Freedom of the Press Foundation. Based on Qubes OS, the platform enables secure and encrypted communications between news organizations, journalists, sources and whistleblowers. It is currently being used in a limited pilot.

The Foundation said the audit report confirmed some its  assumptions around the use of virtualization to segment sensitive workloads and was pleased with the finding that the system system “represents a complex but well researched product that has been thoughtfully designed.”

None of the issues identified were directly exploitable by an attacker, and require either compromise of the SecureDrop server, or code execution in certain key VMs within the SecureDrop Workstation, the Foundation said.

Over the course of their engagement (6 person-weeks with two pen-test/code audit engineers), Trail of Bits found and documented 1 high-risk, 6 medium-risk, 7 low and 12 informational disclosure problems.

The audit confirmed that the high-severity and six of the medium-severity issues have already been patched and released, with the fixes validated by the auditing team. 

The Foundation said it is also investigating potential architectural improvements, including the creation of a custom RPC service to handle opening of files.

“In addition to addressing the findings surfaced in this report, we are also implementing feedback from current pilot participants, and planning new features around export and integration to other communication tools. We are in the process of expanding the pilot to several other news organizations, and hope to provide general availability later this year,” the Foundation said.

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Ryan Naraine is Editor-at-Large at SecurityWeek and host of the popular Security Conversations podcast series. He is a journalist and cybersecurity strategist with more than 20 years experience covering IT security and technology trends. Ryan has built security engagement programs at major global brands, including Intel Corp., Bishop Fox and Kaspersky GReAT. He is a co-founder of Threatpost and the global SAS conference series. Ryan's career as a journalist includes bylines at major technology publications including Ziff Davis eWEEK, CBS Interactive's ZDNet, PCMag and PC World. Ryan is a director of the Security Tinkerers non-profit, and a regular speaker at security conferences around the world. Follow Ryan on Twitter @ryanaraine.