linuxdcpp-team team mailing list archive

[eMTee <1682798@xxxxxxxxxxxxxxxxxx>]

<eMTee> A missing safeguard but it means here we rely on hubs to
distribute the CCPM flag correctly to both sides and according to a
comment in AirDC++'s source, some hubs don't do this. Also hubs can
remove this feature bit to maliciously force users to unencrypted chat
through the hub. Question is here what's best to do, stick to the
protocol, accept the hubs' ability to change the advertised features as
they wish (which is the common practice on other protocol elements) or
leave as is and ignore the missing feature flag for safety reasons.

<cologic> It's an intersting question, yeah. Because it's ultimately the same C-C mechanism as file transfers, at some point if DC++ or other clients decided to push the issue, hubs would find it hard to enforce this downgrade attack you describe.
The status quo seems okay, I guess. Gating it on the CCPM support would give hubs more control than they have now, a material loss for that feature, without necessarily gaining much. Specifically when (hubs disable CCPM) and (hubs filter spam), it can provide a nicer experience, but I don't know how worthwhile it is to cater to that. I also just don't have much feel for largeish public hubs, though. Maybe it's a real problem, worth the tradeoff.
For the (hubs disable CCPM) and (hubs don't usefully filter spam) scenario it's a pure loss. And for the (hubs don't disable CCPM) cases, it's a no-op.

<eMTee> AirDC++ has, but commented out a code checking for the CCPM flag to be present and my question came from a comment there weighing this situation. So they (the mostly used DC client), as currently the state of their side of the bug entry reflects, have not applied any fix.
Maybe it's worth to give the freedom of the decision to the user then and add an opt-out per hub setting for automatically accepting incoming CCPM connections so on problematic hubs only the user can initiate CCPM towards those whom it wishes to talk securely to.

<cologic> Yeah, I think your proposal about letting users choose is
ideal, and absent that, I'm okay with the status quo, regarding
requiring CCPM supports


** Changed in: dcplusplus
       Status: New => Confirmed

** Changed in: dcplusplus
   Importance: Undecided => Medium

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https://bugs.launchpad.net/bugs/1682798

Title:
  CCPM connections are accepted from users that don't advertise CCPM
  support

Status in AirDC++:
  New
Status in DC++:
  Confirmed

Bug description:
  This can be used by spam bots and other malicious clients to randomly
  establish CCPM connections in hubs that have disabled the CCPM
  feature.

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