Hacker News Reader

Comment by nikic | Hacker News Reader

For now I'm only handling people for which I recognize the account or can confirm recent commits.

Are you requiring signed commits? If you're not, I strongly suggest that you do in the future.

I've been pointed out once that only tags should be signed - and referred to this: [1] https://news.ycombinator.com/item?id=12290873

The whole part of signing commits is providing proof that you are who you say you are with the same level of trust provided by other systems built using Public Key Crypto.

You need people to properly secure their keys of course, but it makes life a lot harder for an attacker.

I sign my work-based git commits. I've been using GPG since the late 90s. It's not a silver bullet (especially when a git server has been owned).

When you git pull, then do your work and git commit/push, if you are not careful and you do not examine git status/diff you could sign and commit the hackers change (that you pulled from the repo initially) along with your new changes. So care is required even with PGP signed commits.

This is another good reason to not interrupt developers while they are working. Doing so, makes mistakes such as this more likely.

Can you walk me a scenario where you and I are hosting our code on a malicious git server and Chuck can get their code in our our codebase? (assuming only signed commits)

See:

> if you are not careful and you do not examine git status/diff you could sign and commit the hackers change

I assume he meant that you pull, get an auto merge and then inattentively sign it. With this, you confirm the hackers change with your signature.

You could add a push hook to only allow fully signed chains, but given that we are talking about a compromised server, this does not help.

But how does the hacker's commit goes through in the first place, if all PRs with unsigned commits are rejected outright?

If he hacked the server (which was assumed in the grand parent), he can probably shut off that check rather easily

And then you have a singled commit without a signature lying there for everyone to see and call attention to you.

You don't really pull down code though, you pull down commits. I'm not seeing a case where you sign the attackers code. You might sign a merge commit that has an attack commit somewhere in the tree, but that's very different and much more easily audited.

Even if we assume the git server is completely malicious, I'm still not seeing a case where an attacker can hide a change because I didn't 'status/diff'. I'm open to considering attacks I haven't thought of though.

I think the problem on GitHub is that if you compromise someone's GitHub account (from a leaked password or whatever), you can just add a new public keypair to the account, and now you can sign code as that user.

Requiring two-factor auth for the GitHub account should be good for this though.

I assume you mean that you are only handling people for whom you can confirm their recent php username AND can verify that the specific username connects to/is owned by the same person as the github account provided?

Just to make sure that someone doesn't go in and find a PHP account with recent commits, then email you with a third party github account.

For most contributors we know GitHub identities, as PHP was using pull requests etc already from GitHub.

Aah, k, makes sense :)

The notice starts out by saying:

> Yesterday (2021-03-28) two malicious commits were pushed to the php-src repo [1] from the names of Rasmus Lerdorf and myself.

…and ends by saying:

> We're reviewing the repositories for any corruption beyond the two referenced commits. Please contact security@php.net if you notice anything.

Are you sure that using recent commits as confirmation is a good idea?

There will be increased scrutiny on this repo anyway. It's not necessarily the safest, but probably a low-risk and easy way to migrate committers.

Can you provide more details about the breach? Did they get in via munin?

Reply on news.ycombinator.com