Improving Git protocol security on GitHub
github.blog
github.blog
Seems reasonable to me. Since github is a git-as-a-service provider it makes sense to do this. From the headline I had thought they were making their own variant on the git protocol.
To be fair, extending, extending, and extinguishing does sound like something Microsoft might do.
2. EEE is dead (at least in MS)
SSH is used to authenticate to GitHub as a specific user. GitHub can use this for access control and logging. This isn't new or surprising.
If you don't want to authenticate to GitHub as a specific user, you can clone repositories over HTTPS. This isn't new either. You can't authenticate over HTTPS anymore, but if you were concerned about being "controlled and recorded", you weren't doing that anyway.
You can, just no longer using username and password. Instead you must use an access token.
I see here [0] a few benefits listed:
> Unique – tokens are specific to GitHub and can be generated per use or per device
> Revocable – tokens can can be individually revoked at any time without needing to update unaffected credentials
> Limited – tokens can be narrowly scoped to allow only the access necessary for the use case
> Random – tokens are not subject to the types of dictionary or brute force attempts that simpler passwords that you need to remember or enter regularly might be
...but if you can trivially obtain it by supplying username/password, then it's effectively equivalent anyway.
[0] https://github.blog/2020-12-15-token-authentication-requirem...
Not a big deal but just something that to my knowledge you won't be able to do going forward.
[url "git@github.com:foo/bar"]
insteadOf = git://github.com/foo/barIt's akin using HostName in an ssh config file, though with what I'd consider to be a kind of odd reversed directionality to how you define it (and obviously letting you protocol-jump like this).
What I'm talking about is this: with a git:// URL, if you plug it into Git and that repo is private, you just get "Repository not found" immediately. With an HTTPS URL, if you're routinely using HTTPS for Git, you probably have credentials saved and you might miss that something's not publicly accessible which should be.
Further, if you do have some problem like this then the issue's arguably less clear, as the behavior of a private or simply nonexistent HTTPS repo URL for users without saved credentials is to prompt for login, which can be confusing, making a user think they need a Github account or that there's some problem with theirs.
Like I said though, it's not really a big deal.
The argument for why, according to every vendor I've reported this to, is their users are stupid and will get confused by the strange new detail that if their key is copied to a server that hasn't been upgraded in 8 years, that server might not be able to read the private key [locally]. It is much easier to just use the insecure defaults. For an SSH key.
It's not that bad actually. Debian 9, still supported and updated, does not accept RSA SHA2 keys or certificates.
That said, according to packages.debian.org it ships with OpenSSH 7.4 and support for sha2 have been included since 7.2. And ed25519 has been included since 6.5, so you should be fine.
Yeah, but LTS is still support :P
> That said, according to packages.debian.org it ships with OpenSSH 7.4 and support for sha2 have been included since 7.2. And ed25519 has been included since 6.5, so you should be fine.
You'd think that, but Debian do their own thing. I don't recall the exact versions, but the Include directive for sshd_config should be present in the version shipped in Debian 9, but isn't[0]. I can't find the exact listing, but for instance you can see that `ssh-keygen` in Debian 9, of version 7.4, doesn't support rsa-sha2[1]; it does support `ed25519` however.
0 - https://manpages.debian.org/stretch/openssh-server/sshd_conf...
1 - https://manpages.debian.org/stretch/openssh-client/ssh-keyge...
Let me use a password if I want, these security requirements are becoming increasing absurd - I could realistically see people just checking out of services if these invasive procedures continue. Just kidding, a lad can dream. Yeah it's not rocket surgery to add the ssh key and then clone it to your different machines but if you have strict sprint deadline or something and you haven't pulled from your repo in a day and suddenly you can't run your workflow, then that's really pretty annoying to have to run the context switch and do some random bullshit to appease your vendor's obnoxious requirements. If Millenials ever learn software engineering en-masse maybe they would decry this lack of consent in daily software engineering operations. (Haha jk... not really, but I'm a Millenial so it's ok for me to say this)
Passwords are 100% the weakest link in our beep boop chain of trust, of course - we know this. But maybe they should just be rethought from the ground up instead of randomly affecting your users all the time with security nonsense.
EDIT: WOW speak of the devil, I literally just received an email saying on of my earlier keys is about to expire (personal account vs my employer GitHub account). Seriously shoot me in the face, why do I have to constantly update stuff to comply with requirements without getting paid? Just kidding, but almost not.
:rage_face:
Never was an issue for me because I'd always been using keys in the first place. I imagine it's less common for folks who don't manage servers, but all of my prior ssh usage had switched to keys over a decade ago.
>Like procedurally its simple but I have a bunch of accounts, a bunch of different repos.
Definitely recommend looking into creating a ssh config if you're using different keys per account. (Notably you can set your IdentityFile (key to use) per host (which can also be set as something arbitrary like "gh-username")
There's a pretty friendly post here: https://nerderati.com/2011/03/17/simplify-your-life-with-an-...
>Let me use a password if I want, these security requirements are becoming increasing absurd
I don't want my software dependencies to be compromised just because someone reused a password.
>Passwords are 100% the weakest link in our beep boop chain of trust, of course - we know this. But maybe they should just be rethought from the ground up instead of randomly affecting your users all the time with security nonsense.
Keys are rethinking it from the ground up (which seems to be the complaint), though there certainly are challenges in managing keys as well.
I do a lot of data ingestion work, I run my own servers within a ZeroTier setup that links a bunch of machines together. I can only access it from my machines that have a set SSH key setup, so I agree, that's a great system. I ingest data from a bunch of data providers as well as some exchanges/brokers. But for example, look at the disparity for some of these web operators - Gemini only uses Authy for 2FA management iirc + password, Coinbase is Authenticator (or whatever you want) + password, Interactive Brokers has some weird bespoke setup that requires an initial mobile login and then another layer of auth that I can't fully describe. DigitalOcean is authenticator + password, GitHub is authenticator or SMS + password [I'm referring to actually accessing the website from a client device for all of these] Then they all have API key generation which has variable definitions. AWS is nice for its consistency with its AWS access key + private key combo that you can generate whenever you need with IAM profiles.
It's just... this is a lot to even need to know. I wish I didn't have to know the intricacies of all these crazy systems. I want to get some stuff done. I'd be down to have it be biometric or something. I'm tired of having to think about how I log into stuff and managing keys for all this shit. Literally - that's my complaint. It's all too much to keep in my head and I'm frequently frustrated by needing to recall this stuff. Sure, lastpass is fine for what it is and I also do try to keep my SSH keys safely stored for re-use where desired or generate machine specific configurations when that is reasonable for the project specification, but it's really just a headache for me.
I'd love a ssh key management solution that doesn't drive me bonkers - if you have any suggestions I'll owe you a coffee next time youre in town lol.
Kinda in the same boat here, taken a glance at Vault [1] but it seems like something that I'd probably spend more time figuring out than get benefit from it given my relatively small footprint.
Definitely have a lot more ssh authorized_hosts entries lingering around from old systems than I'm happy about.
Shout HN: Does anyone here that might be watching this space have any experience using Vault...?
At that time (this may have changed in the interim; I'm not using Linode nearly as much these days), Linode didn't offer private LANs between groups of servers. They did offer private IP addresses, but they had only a single LAN that was shared by every machine in each data center. But I figured; hey, that'd probably be good enough -- Those private IPs weren't publicly accessible, after all!
Anyhow, long story short, less than twelve hours later all three machines were furiously mining bitcoin.
Lesson learned: when software says that you need a private network, you need a private network.
>Lesson learned: when software says that you need a private network, you need a private network.
Hah yeah, I imagine a properly secured (famous last words) VPN setup is kinda necessary when dealing with stuff like that.
Having your secrets in one place (especially remotely accessible) is a very attractive target and you don't want to find out there's a 0day (or general misconfiguration) on your management system the hard way.
I'd like to think that I could make something like that work, but it's certainly more than setup and forget about it.
Though yeah, I'd also like a better key management setup for myself. I have not been able to get either gpg-agent or ssh-agent to where I want in terms or privacy or usability.
Github is not in a position to "rethink passwords from the ground up". They are however in a position where it's their responsibility to ensure the security of what they host.
These changes are good. That you're calling them "absurd" and "security nonsense" speaks volumes, to be honest.
And if one of your keys is about to expire (I'm guessing a GPG key since SSH keys traditionally have no expiration), that'd be because you put an expiration date on it. One you chose…
P.S. no the email that came is was related to a personal access token for my own special projects account. Maybe they defaulted to some expiration period, don't care enough to go out of my way to find out right now.
SSH key stored on multiple devices which amounts to a saved password: wow, so secure, much better.
I still don't get it.
Passwords are just not viable for public-facing services any more. If they let people use passwords, those people would keep getting hacked, and the support burden (or the reputation burden if they just shrugged their shoulders) would be too high.
Frankly, between using passwords that you're forced to rotate / expire / use x special characters and y numbers, using some opaque ML system that blocks your login whenever you're travelling, and just actually using ssh keys, I know which option I prefer.
Also why on earth would I want to type a password every time I do something, even when it was an option I usually cancelled my push and set up an ssh key.
It is, actually. https://manpages.ubuntu.com/manpages/xenial/man1/ssh-keygen.... look for "-V validity_interval". Admittedly that's on the certificate rather than the key itself (yes, SSH keys can have proper CA infrastructure!) and not something most people have to worry about.
> Github drops it after a year and requires you to add it again
That's pretty clearly what GP was referring to. And I completely understand how annoying it would be, too. Consider this, you might not even use it again before it expires again, but if you don't re-add it promptly you probably won't be able to figure out why stuff isn't working the next time you do use it...
Nowadays if copy/pasting the CLI commands github gives you and putting that in your profile settings is offputting, a lot of GUIs exist that will automate the setup process. It's not something where you're going to lose lots of time adjusting your settings, and it's not like github did not give a lot of warning on this change.
There's plenty of security behaviours I find overbearing, but I have to say I'm pretty ok with how github has been handling their transitions.
Haha just kidding, here what's up - this is what a friend of mine does that has nothing to do with my own operations of course. Probably violating many contractual arrangements bigly but honestly the whole security side of this stuff is so anal retentive that I will, for the greater good of my boy generationP.
You just go into your dev settings on GitHub. (Top right when youre on GitHub.com, dev profile pic, click on Settings then on Developer Settings, then you'll be confused because it asks you to register a dumbass GitHub app - ignore this)
Then click on "Personal access tokens" on the lower left of the left most menu.
Then generate with the desired permissions (wow, guess what most people will select in a rush...? shocking, unimaginable...)
Anyways once you have the token, which will only be generated once, so save it down - I just make a environment variable and export it because I have a finite amount of time in my life and this stuff beyond annoys me.
The just repoint your local repo clones to an instance with the following convention:
git://<username>:<personal_access_token>@github.com/<username OR orgname>/<repo name>
Good luck, old sport. Post on here if you have any problems. You can also modify all the crap in your .git subdirectory within a repo but that's deep in the danger zone.
$ git remote set-url origin git://<my userid>:<my token>@github.com/<repository owner's userid>/<repository name>
$ git pull
fatal: unable to look up <my userid>:<my token>@github.com (port 9418) (Non-recoverable failure in name resolution)
(The set-url worked fine -- the new URL is indeed in the .git/config.)
An easier route might be GCM Core (https://github.com/microsoft/Git-Credential-Manager-Core). And of course, disclosure, I'm the product manager for GCM Core and author of this blog post.
I'll keep your manager in mind for when I need multi-factor auth, which so far hasn't happened.
EDIT: this is kind of a joke, but the spirit is still in play.
I also don't want to register apps at them and don't want to wait until they acknowledge access. The market is too competitive for that.
An overall it doesn't really add security to my threat model. A complicated authentication isn't necessarily a secure authentication. Given, passwords have to be handled with care, but any ssh key could just as well be scraped by the OS vendor as any password or by someone that compromised your system.
> GitHub hasn’t traditionally offered these as host keys (server keys), but we’ll be offering them as options in the future.
These issues have been around for more than a decade, but they keep popping up. The last 3-ish years a larger push has been made to disable CBC ciphers (in SSL/TLS, SSH, etc.). See [0, 1, 2, 3, and 4] for more information.
GCM/CTR is considered to be a more secure alternative.
[0]: https://en.wikipedia.org/wiki/Padding_oracle_attack#Padding_...
[1]: https://www.openssh.com/txt/cbc.adv
[2]: https://ieeexplore.ieee.org/document/5207634 (is CPNI-957037)
[3]: https://alicegg.tech/2019/06/23/aes-cbc.html
[4]: https://docs.microsoft.com/en-us/dotnet/standard/security/vu...
[n]: You can find more information with a quick search, this also includes security advisories from HPE, RedHat, IBM, and F5.
Edit: There's a good explanation here https://crypto.stackexchange.com/questions/2310/what-is-the-...
CBC does not provide authentication, thus it does not protect your encrypted content from manipulation (which can enable all kinds of followup attacks). Generally you should avoid using unauthenticated ciphers almost always and use an AEAD.
SSH uses CBC in combination with a MAC, so it has authentication, but it combines them in an insecure way. It turns out it's practically impossible to avoid these attacks (there had been countermeasures, but it's been shown that they can be circumvented). The attacks only let an attacker decrypt a single byte in certain situations, so the practical impact is limited.
Here's the original attack: https://www.isg.rhul.ac.uk/~kp/SandPfinal.pdf
Here's an updated paper that shows that the countermeasures against the original attack don't work. https://www.isg.rhul.ac.uk/~kp/surfeit.pdf
I generally use that for grabbing stuff for inspection & evaluation as on a number of my machines, https protocol does not work (seemingly due to only supporting older versions of TLS).
I have not upgraded those machines for 'reasons'.
It can be worked around by grabbing on a newer machine, then cloning from there, but that is extra hassle. Ho hum.
(Given the Merkle hash format of the git repo's, there is really little or no need for an encrypted connection when fetching from a public repo).
The only exception is if you know the commit hash a priori perhaps, and fetch that explicitly. But you often don't; even assuming most Git/GitHub workflows did know that, you're just passing the buck because to verify that commit hash is authentic you have to use some other secure channel, and that's often HTTPS.
My workflow was to look at the site with a web browser (with working up to date TLS), and note the hash of the final commit of master. This can be done on a different machine.
Then one clones the repo from the non https capable machine, and verifies the hash for the tip of master. Rinse and repeat for any other branches of interest, especially if only performing a limited clone.
I myself have committed with a hash of 0000000 into a git repository twice, meaning it is easy to confuse those two commits.
An attacker would merely have to brute force the tip of their attacker repository, a matter which you can do within the hour on a stock standard PC.
So you think, that you can do so in a hour? How much are you willing to bet on that?
For bonus points try to "brute force a tip" for repository, containing actual contents (as opposite to randomly named binary files with gibberish).
I cloned this repo: https://github.com/bradfitz/gitbrute
Ran the command in the readme (had to do it twice for some reason) and the latest commit is now 000001 on my fork of the repo: https://github.com/Genbox/gitbrute/commit/0000019075dabc337f...
It took less than 3 minutes for the full thing.
As I said trivial to prove valid; and since I was actually reading, using, and compiling the code, quite difficult to achieve a collision in the circumstances.
Then some time later when doing a fetch, I received a TLS nego rejection complaint. Github had turned off support or earlier versions TLS, and the machine in question did not implement the later version. (I believe this was on an old macOS version).
So as a workaround, I altered the refspec in the git config file to switch to using the raw git protocol.
i.e. their earlier 'improve security' measure drove me to switch to the 'improved' unencrypted git protocol.
:-)
socat TCP-LISTEN:8080,fork,reuseaddr OPENSSL:github.com:443
However what I'm more inclined to do is simply compile up a version of git from source, ensure it includes the HTTPS transport, and links against an appropriate TLS/SSL library. I used to build it from source years ago (on a different platform).
The git protocol approach was simply to avoid that hassle, as used correctly it is safe enough.
https://www.siteground.com/kb/how_to_generate_an_ssh_key_on_...
This site isn't where I first saw this. This isn't the top hit for any search term I can come up with, but it is often on the first page of hits. So people do silly things without understanding what they're doing.
(To give somewhat of a feeling for age here, the exact wording from that tutorial is at least 5 years out of date. Putty changed the UI a bit in 0.68)
I don't know if this is the case. I always clone with `github.com:owner/repo` remotes, because it's shorter and saves me the effort of doing things differently based on whether it's my repo or not.
(Seriously asking by the way, this isn't a put-down. MS isn't in the ad business, let alone Github, and these changes primarily affect people who are logged in, so … no idea how you can make the leap)