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Hidden GitHub Commits and Methods to Reveal Them — Neodyme

Hidden GitHub Commits and Methods to Reveal Them — Neodyme

2024-02-23 09:41:13

TL;DR

We now have created a device for GitHub that may reveal commits that doubtlessly comprise delicate data and usually are not accessible by way of the general public Git historical past, however which may be of curiosity or have been deliberately deleted.

Introduction

GitHub is without doubt one of the mostly used platforms and cloud-based providers for software program improvement and model management utilizing Git.
Folks use it to share code, tasks, or customized developments on-line; the mission’s historical past is recorded within the commits (and the commit messages) and is on the market for viewing to anybody.
GitHub presents many further options, a few of that are well-known and broadly used whereas others stay nearly unknown to customers.

Generally, the shared information incorporates secrets and techniques, or data that ought to not have been revealed. There are methods to delete them, however they don’t seem to be intuitive in any respect.
Throughout a current safety analysis, we had a repo with deleted commits, and recognized a GitHub flaw that isn’t well-known.
It permits entry to commits not listed within the mission’s historical past, together with commits which were eliminated utilizing a pressured push. We now have created github-secrets to seek for and discover such commits on any public repository in order that customers can decide whether or not supposedly deleted commits are at present publicly seen of their repository.

We are going to now present a quick overview of the method concerned in deleting Git commits, emphasizing the challenges posed by a distant repository on GitHub with its caching and APIs, which make this job not possible with out reaching out to GitHub buyer help.

Desk of contents

  1. Git and Git reset
  2. GitHub API and its additional functions
  3. Security implications
  4. Github Secrets
  5. Example

Git and Git reset

Git is a robust and environment friendly software program for distributed model management.
It tracks the changes in all files stored in the repository and allows collaborative software program improvement within the codecs utilized by most programmers. The most typical options are presumably well-known so we won’t study them extra carefully right here.

xkcd git, CC BY 2.5

Suppose, nonetheless, that you’ve unintentionally dedicated and pushed an incorrect entry to a repository. What are you able to do about it?
You now have two choices: you both create one other commit and proper your error or — if you happen to don’t need anyone to see the faulty commit — you possibly can comply with the directions you’ll find in a fast on-line search and execute the next two instructions to undo the wrong commit and clear the commit historical past:

git reset --hard HEAD^
git push origin -f

Let’s talk about this selection for a second. The reset command is a flexible device that includes a variety of various choices for undoing the modifications in a repository.
A deep dive into the git reset command could be present in the atlassian tutorials. Particularly, this reset command with the flag --hard HEAD^ reverses the newest commit on this department, primarily by undoing all file modifications and making it seem that the commit by no means occurred.
The next push command with the flag -f (for power) ignores all warnings and security mechanisms of Git when pushing to the distant repository.
That is vital as Git would usually stop you from pushing over newer commits on a distant repository.
As beforehand talked about, Git is mostly used when engaged on tasks cooperatively.
Throughout improvement, it typically occurs that your native revision standing is older than the distant standing (as a result of another person pushed a commit after your checkout).
Usually, you would need to pull the distant repository once more and both merge or rebase the newer commit.
In our case, nonetheless, we need to actively delete this “newer” commit. Utilizing the -f flag, we inform Git we all know what we’re doing and the distant repository accepts our older standing of the repository.

Our on-line analysis signifies that we will right the modifications and push a brand new commit with out abandoning any hint of our earlier error.
However warning is suggested: simply because a commit is just not accessible by way of the historical past doesn’t imply that it can’t be retrieved.
Instructions like git reflog or git fsck --lost-found will make these commits seen once more and might even restore them if wanted.
For instance, this blog post describes how one can restore a misplaced commit from the pc used to create and push it.
It’s not possible, nonetheless, to make use of ‘git reflog´ to clone a repository from GitHub and see these commits.

Native git reflog

Distant git reflog

So if we had unintentionally pushed some secrets and techniques on GitHub, however force-pushed over the wrongful commit, we ought to be fantastic, proper? Under no circumstances!

Because of GitHub’s inner structure, they don’t delete force-pushed commits! Whereas they’re not cloned with a standard clone and can’t be enumerated with reflog, they’re accessible if we all know the commit hash by merely specifying the hash within the GitHub URL. With that in thoughts, allow us to take a look at the GitHub API.

GitHub API and its further capabilities

When a Git repository is about up on GitHub, a number of information and knowledge moreover the repository itself are arrange.
For instance, it’s attainable to observe or star repositories on GitHub, and this data must be saved someplace; GitHub Insights must be initialized, Points, Undertaking, Actions and lots of extra further capabilities have to be arrange for the newly created repository.
Aside from the overall Git instructions (that are equally usable in GitHub), GitHub presents an extra API for interacting with all the additional capabilities that aren’t carried out in the usual Git software program.
One instance is the statistics endpoint that collects details about the overall exercise on the repository (reminiscent of an hourly commit count for each day).
Nonetheless, this data may be gathered from the overall UI.
A much more attention-grabbing public endpoint that isn’t seen within the basic GitHub UI is the event endpoint.
The endpoint lists a large number of different events reminiscent of WatchEvents, CommitCommentEvents, DeleteEvents, GollumEvents (if you happen to’ve by no means heard of this one, no worries; it’s the occasion for a wiki web page creation or replace) and even PushEvents on a specific repository.
You possibly can question that endpoint for each public repository.

All events of a public repository

All occasions of a public repository

On condition that we’re discussing hidden commits, let’s check out the PushEvents. We particularly ask ourselves the next questions:
Does the commit historical past show all commits which have ever been pushed?
Do we discover any details about our beforehand deleted, now hidden commit?
Let’s bear in mind the scenario we described above: We now have pushed an incorrect commit and need to reverse this motion.
Our first push with the wrong commit created a PushEvent with an array of commit objects describing the pushed commits.
After we now force-push an older model onto the distant Git, we create an extra PushEvent.
As an alternative of producing a brand new commit, it merely rolls again the pinnacle of the distant repository.
The earlier incorrect commit is not a part of the historical past and isn’t seen within the GitHub commit historical past UI.
Some on-line sources discussing this subject (for instance, this StackOverflow thread) point out {that a} force-pushed commit should still be accessible by way of its SHA1-Hash.
Nonetheless, they don’t let you know how one can discover this hash if you happen to didn’t see the commit whereas it was nonetheless within the common historical past.
This may give folks the impression that if the force-push was quick sufficient and no one noticed the commit and its related hash, there is no such thing as a hint of the commit wherever (because it has been deleted from the historical past).
Don’t fall into this lure because it may provide you with a way of false safety of getting ”quick-fixed the error”.
That is additionally the case if you happen to change your repository setting from personal to public.
The occasions endpoint nonetheless lists all PushEvents even from the time it was personal and the hash of our incorrect commit can nonetheless be seen right here. The commit we tried to cover with the force-push could be discovered by anyone accessing the general public occasions API!

Example of a force-pushed repository, reset to an older commit

Instance of a force-pushed repository, reset to an older commit

Safety implications

First, let’s be clear about one factor: so long as a pushed commit stays obtainable within the regular Git historical past, anyone can clone or fork the repository with this standing, so all delicate information ought to be thought of compromised it doesn’t matter what.
We now have additionally simply described how one can retrieve all the data essential to entry the deleted commit by discovering the corresponding PushEvent, extracting the SHA1-Hash and accessing the commit by way of the hash.
However this isn’t the one technique to entry commits which are not listed within the historical past.
Generally it’s even attainable to brute-force commits utilizing not more than the primary 4 characters of the hash described within the Short SHA-1 part of this git documentation.

The one official way to utterly delete an internet commit (even from all cached views) is to contact the GitHub help immediately.

Github Secrets and techniques

We now have developed a device to determine these dangling or hidden commits and to see if any information are rendered at present seen by this error that ought to be deleted by the GitHub help.
Usually talking, there could possibly be extra commits linked to your repository than these listed within the basic commit historical past of any department.
Not all of them are errors or force-pushed commits; this could additionally occur when merging pull requests and so forth.
Utilizing a Github API key to scan bigger repositories (which could be added as an setting variable) is advisable.

Instance

Instance repository with a “deleted” commit (not on-line anymore):
https://github.com/neodyme-labs/github-secrets-demo

Example repository

Instance repository

All commits in the GitHub UI

All commits within the GitHub UI

All occasions of this repository may have been accessed by way of:
https://api.github.com/repos/neodyme-labs/github-secrets-demo/occasions

See Also

All events of a public repository

All occasions of a public repository

As you possibly can see beneath, there may be an empty PushEvent and the earlier occasion has a commit that isn’t discovered within the GitHub UI:

Example of a force-pushed reset of the git head

Instance of a force-pushed reset of the git head

Right here is the deleted commit as recovered from the occasions api:
https://github.com/neodyme-labs/github-secrets-demo/commit/ddc0ca8a18c4001fbca0ac433f1d2e7bdd882a68

Dangling commit

Dangling commit

If you now run our device, all commits will likely be displayed on to you as proven right here:

Dangling commits found with Github Secrets

Dangling commits discovered with Github Secrets and techniques

Extra data and the device itself could be discovered at GitHub.

We hope you’ve gotten discovered this weblog submit and the accompanying device useful and informative. Within the occasion that you’ve inadvertently disclosed delicate data by way of a git commit, we extremely suggest promptly biking all affected secrets and techniques. It’s essential to take this precaution, as you by no means know who might have already pulled the data.

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