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Workhorse bypass allows files in /tmp to be read via Maven Repository APIs

HackerOne report #908796 by ledz1996 on 2020-06-26, assigned to @ankelly:

Summary

Similar issue to #848415 and #876998
As far as we know there exists an UploadedFile.from_params leads to a series of Workhorse bypass vulnerability.
There exists one in maven APIs before but have been patched due to this issue

#209080 (closed)

However, the route Detecting in Workhorse sees %2f as /.
So this mean

  • If a full path for a project to put in for the API is 000173%2fpackages%2fmaven, the Workhorse will see this as 000173/packages/maven and treat this as a valid path for

internal/upstream/routes.go

		route("PUT", apiPattern+`v4/projects/[0-9]+/packages/maven/`, upload.BodyUploader(api, signingProxy, preparers.packages)),

This will proceed us to bypass the Workhorse authorizing in RoR part, thus result in system file/object storage enumerating by using file.path or file.remote_id.

Steps to reproduce

  1. Create an Project and Note the ID of the Project. For example: ID 40
  2. Create a subgroup and project with the following path: 0040/packages/maven
  3. Send the PUT request to the following URL: /api/v4/projects/0040%2fpackages%2fmaven/package/?file.path=../../../../../../../../../../../../etc/passwd Along with Header: Private-Token: which is the token for accessing the API
    or /api/v4/projects/0040%2fpackages%2fmaven/package/?file.remote_id=object-id for Object Storage
  4. If its response with 500 -> the file/ object is not exists, 400 -> The file exists.
    Why 500 code means not exists:
    fileenum1.PNG

Uploaded a video for this:
bandicam_2020-06-26_17-13-53-860.mp4

Results of GitLab environment info


System information  
System:		Ubuntu 16.04  
Proxy:		no  
Current User:	git  
Using RVM:	no  
Ruby Version:	2.6.6p146  
Gem Version:	2.7.10  
Bundler Version:1.17.3  
Rake Version:	12.3.3  
Redis Version:	5.0.9  
Git Version:	2.27.0  
Sidekiq Version:5.2.7  
Go Version:	unknown

GitLab information  
Version:	13.1.0-ee  
Revision:	1fa237df2f4  
Directory:	/opt/gitlab/embedded/service/gitlab-rails  
DB Adapter:	PostgreSQL  
DB Version:	11.7  
URL:		http://gitlab.example.vm  
HTTP Clone URL:	http://gitlab.example.vm/some-group/some-project.git  
SSH Clone URL:	git@gitlab.example.vm:some-group/some-project.git  
Elasticsearch:	no  
Geo:		no  
Using LDAP:	no  
Using Omniauth:	yes  
Omniauth Providers: saml

GitLab Shell  
Version:	13.3.0  
Repository storage paths:  
- default: 	/var/opt/gitlab/git-data/repositories  
GitLab Shell path:		/opt/gitlab/embedded/service/gitlab-shell  
Git:		/opt/gitlab/embedded/bin/git

Impact

Disclose existence of a file in system, Object Storage, etc.

Attachments

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Edited by Andrew Kelly