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External service interaction (HTTP & DNS) #9929
Comments
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Thank you for the detailed report. This endpoint doesn't need to be accessible without authentication and should be limited to authenticated users. Beyond that, we do need this endpoint to be able to provide arbitrary link previews to users in their posts. The scope of allowed URLs is too wide to implement a meaningful allowlist. That said, we could cache the response for a while node-wide to prevent ping backs systems from gathering too much data. So two improvements axes:
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It's really nice hear that \o/ For this specific endpoint I understood that is about giving an URL to share with others users. Another thing that I'd like to ask you is, may I proceed with the opening of a CVE? |
No, the point of this endpoint is to extract title, description and image from the target URL to create a link preview card in a post. As such it does have to do a DNS and HTTP request. However, making it authenticated will remove the opportunity to use for nefarious means by anonymous users, and caching the answer will prevent potential spam/tracking by severely limiting the amount of outgoing HTTP requests actually sent out when this endpoint is used.
I have no idea what this means for us, can you please elaborate? |
Thanks for the explaining.
CVE, short for Common Vulnerabilities and Exposures, is a list of publicly disclosed computer security flaws. When someone refers to a CVE, they mean a security flaw that's been assigned a CVE ID number. Basically, having a CVE ID assigned to a specific vulnerability makes it easier for enterprises who uses your software to check for security issues. For you it means you guys care for security and are willing to let this vulnerability be part of a security database. Like MITRE wrote:
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Thank you for your explanation, we don't have any presence with enterprises so it probably won't help anyone but it won't do us any harm either, please go forward if you feel it's warranted. |
Hello Friendica Team.
Issue detail
I found a vulnerability issue while testing frendica locally.
It is possible to induce the application to perform server-side DNS lookups of arbitrary domain names and HTTP request.
Bug Description
The ability to send requests to other systems can allow the vulnerable server to be used as an attack proxy. By submitting suitable payloads, an attacker can cause the application server to attack other systems that it can interact with. This may include public third-party systems, internal systems within the same organization, or services available on the local loopback adapter of the application server itself. Depending on the network architecture, this may expose highly vulnerable internal services that are not otherwise accessible to external attackers.
Steps to Reproduce
The request:
The response:
The DNS and HTTP request received:

More details
To make this request doesn't need to be authenticated, the friendica application accepts any request as an attachment and next do the DNS lookup and the HTTP request.
Issue remediation
You should review the purpose and intended use of the relevant application functionality, and determine whether the ability to trigger arbitrary external service interactions is intended behavior. If so, you should be aware of the types of attacks that can be performed via this behavior and take appropriate measures.
These measures might include blocking network access from the application server to other internal systems, and hardening the application server itself to remove any services available on the local loopback adapter. If the ability to trigger arbitrary external service interactions is not intended behavior, then you should implement a whitelist of permitted services and hosts, and block any interactions that do not appear on this whitelist.
References
Platform Info
This is Friendica, version 2021.01 that is running at the web location localhost
The database version is 1384/1384, the post update version is 1383/.
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