Summary:
Ref T12961. In Mercurial, it's possible to have "subrepos" which may use a different protocol than the main repository.
By putting an SSH repository inside an HTTP repository, an attacker can theoretically get us to execute `hg` without overriding `ui.ssh`, then execute code via the SSH hostname attack.
As an immediate mitigation to this attack, specify `ui.ssh` unconditionally. Normally, this will have no effect (it will just be ignored). In the specific case of an SSH repo inside an HTTP repo, it will defuse the `ssh` protocol.
For good measure and consistency, do the same for Subversion and Git. However, we don't normally maintain working copies for either Subversion or Git so it's unlikely that similar attacks exist there.
Test Plan:
- Put an SSH subrepo with an attack URI inside an HTTP outer repo in Mercurial.
- Ran `hg up` with and without `ui.ssh` specified.
- Got dangerous badness without `ui.ssh` and safe `ssh` subprocesses with `ui.ssh`.
I'm not yet able to confirm that `hg pull -u -- <uri>` can actually trigger this, but this can't hurt and our SSH wrapper is safer than the native behavior for all Subversion, Git and Mercurial versions released prior to today.
Reviewers: chad
Reviewed By: chad
Subscribers: cspeckmim
Maniphest Tasks: T12961
Differential Revision: https://secure.phabricator.com/D18389
Summary:
Ref T4292. Ref T10366. Depends on D15751. Today, generating repository commands is purely a function of the repository, so they use protocols and credentials based on the repository configuration.
For example, a repository with an SSH "remote URI" always generate SSH "remote commands".
This needs to change in the future:
- After T10366, repositories won't necessarily just have one type of remote URI. They can only have one at a time still, but the repository itself won't change based on which one is currently active.
- For T4292, I need to generate intracluster commands, regardless of repository configuration. These will have different protocols and credentials.
Prepare for these cases by separating out command construction, so they'll be able to generate commands in a more flexible way.
Test Plan:
- Added unit tests.
- Browsed diffusion.
- Ran `bin/phd debug pull` to pull a bunch of repos.
- Ran daemons.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T4292, T10366
Differential Revision: https://secure.phabricator.com/D15752
