T09 · Insecure Skill Coding Practices
Warning
- Location
- scripts/git_clone_or_update.sh:23
- Finding
- Existing Repository Origin Is Not Validated Against the Requested Remote URL## Vulnerability Details **File Location**: `scripts/git_clone_or_update.sh`, lines 23-29 **Vulnerability Type**: Repository origin confusion and unsafe update behavior **Risk Level**: Medium ```bash if [ -d "${GIT_LOCAL_PATH}" ]; then # Directory exists — fetch and pull latest changes cd "${GIT_LOCAL_PATH}" || { echo "ERROR: Failed to enter directory ${GIT_LOCAL_PATH}. Check: $0" exit 1 } git fetch origin "${GIT_BRANCH}" git pull origin "${GIT_BRANCH}" ``` ### Technical Analysis When `GIT_LOCAL_PATH` already exists, the script changes into that directory and fetches from its configured `origin`. It does not: - Confirm that the directory is a valid Git working tree. - Compare `git remote get-url origin` with the supplied `GIT_REMOTE_URL`. - Use the supplied `GIT_REMOTE_URL` during the update. - Require a fast-forward-only update. Consequently, the required `GIT_REMOTE_URL` input is effectively ignored for existing directories. The update source is instead determined by mutable configuration inside the selected local repository. This creates a repository-origin confusion vulnerability: a caller may believe that content is being updated from a trusted URL while the script actually retrieves it from a different or attacker-controlled origin. ### Attack Path 1. An attacker prepares or influences an existing directory at the path later supplied through `GIT_LOCAL_PATH`. 2. The directory is configured as a Git repository with `origin` pointing to an attacker-controlled repository. 3. A caller invokes the skill with that local path and supplies an expected trusted repository through `GIT_REMOTE_URL`. 4. Because the local directory already exists, the script ignores the supplied URL. 5. `git fetch origin` and `git pull origin` retrieve and integrate content from the attacker-controlled origin. 6. The attacker can alter files in the working tree. If the existing local reposit ...[truncated 794 chars]
- Remediation
- ## Remediation Suggestions - Verify that an existing target is a valid Git working tree before updating it, for example with `git rev-parse --is-inside-work-tree`. - Read the configured origin using `git remote get-url origin` and compare its canonicalized value with `GIT_REMOTE_URL`. - Reject origin mismatches by default. If changing the origin is supported, require explicit caller confirmation before using `git remote set-url origin`. - Validate `GIT_BRANCH` as a permitted Git branch or ref name and reject option-like or malformed input. - Use a fast-forward-only update, such as `git pull --ff-only origin "${GIT_BRANCH}"`, to prevent unexpected merge commits. - Consider fetching first and explicitly checking the intended commit or ref before modifying the working tree. - Produce a clear error when an existing path is not a Git repository or does not have the expected remote.