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Improper Access Control in Onionshare

Moderate severity GitHub Reviewed Published Jan 18, 2022 in onionshare/onionshare • Updated Oct 7, 2024

Package

pip onionshare-cli (pip)

Affected versions

>= 2.3, < 2.5

Patched versions

2.5

Description

Between September 26, 2021 and October 8, 2021, Radically Open Security conducted a penetration test of OnionShare 2.4, funded by the Open Technology Fund's Red Team lab. This is an issue from that penetration test.

  • Vulnerability ID: OTF-003
  • Vulnerability type: Improper Access Control
  • Threat level: Moderate

Description:

Anyone with access to the chat environment can write messages disguised as another chat participant.

Technical description:

Prerequisites:

  • Alice and Bob are legitimate users
  • A third user has access to the chat environment

otf-003-a

This screenshot shows Alice (glimpse-depress) and Bob (blinker-doorpost) joined a chatroom and are the only participants in the chatroom. Then the non-listed user squad-nursing writes a message in the chatroom without being visible in the list of users. The sending of the message itself is not required but was done here to show the initial access. The non-listed participant now renames himself to Bob and writes another message, seemingly coming from Bob.

This can be reproduced by slightly modifying the client-side JavaScript. The joined emit needs to be removed from the socket.on(connect) event handler. Therefore a client is not listed in the userlist and has no active session.

https://github.com/onionshare/onionshare/blob/d08d5f0f32f755f504494d80794886f346fbafdb/cli/onionshare_cli/resources/static/js/chat.js#L16-L18

This can be done either via a crafted client or runtime modification of the chat.js script in the browser's internal debugger.

It is still possible to call the text method and send text to the chat via websocket.

https://github.com/onionshare/onionshare/blob/d08d5f0f32f755f504494d80794886f346fbafdb/cli/onionshare_cli/web/chat_mode.py#L131-L139

It is also possible to call the update_username function and choose an existing username from the chat.

https://github.com/onionshare/onionshare/blob/d08d5f0f32f755f504494d80794886f346fbafdb/cli/onionshare_cli/web/chat_mode.py#L141-L162

Afterwards the hidden user can send messages that are displayed as coming from the impersonated user. There is no way to distinguish between the fake and original message.

Impact:

An adversary with access to the chat environment can impersonate existing chat participants and write messages but not read the conversation. The similar exploit described in OTF-004 (page 19) has only slightly more requirements but also allows for reading.

Recommendation:

  • Implement proper session handling

References

@micahflee micahflee published to onionshare/onionshare Jan 18, 2022
Published by the National Vulnerability Database Jan 18, 2022
Reviewed Jan 19, 2022
Published to the GitHub Advisory Database Jan 21, 2022
Last updated Oct 7, 2024

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality Low
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

EPSS score

0.053%
(23rd percentile)

Weaknesses

CVE ID

CVE-2022-21692

GHSA ID

GHSA-gjj5-998g-v36v

Source code

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