Attack Surface: 1. Compromised fvm Release
Description: Attackers distribute a malicious version of the fvm tool itself, compromising the entire Flutter SDK management process.
How fvm Contributes: fvm is the direct target and vector. A compromised fvm controls all subsequent SDK operations.
Example: An attacker compromises the fvm GitHub repository or pub.dev listing and replaces the legitimate release with a backdoored version.
Impact: Arbitrary code execution on developer machines and CI/CD servers, leading to complete compromise of the development pipeline.
Risk Severity: Critical
Mitigation Strategies:
* Package Verification: Attempt to verify downloaded fvm package integrity (checksums, if available – often impractical).
* Trusted Sources: Install fvm only from official sources (pub.dev, GitHub releases).
* Internal Mirroring: Maintain an internal, vetted mirror of fvm (for larger organizations).
* Monitoring: Actively monitor the fvm project for security advisories.
Attack Surface: 2. Dependency Confusion/Substitution (for fvm itself)
Description: Attackers exploit fvm's dependencies by publishing malicious packages with the same names as legitimate fvm dependencies.
How fvm Contributes: The attack targets fvm's own dependency resolution process, making fvm the direct conduit for the malicious code.
Example: fvm depends on "downloader". An attacker publishes a malicious "downloader" on pub.dev, and fvm installs it.
Impact: Arbitrary code execution on systems running fvm, compromising the development environment.
Risk Severity: High
Mitigation Strategies:
* Lockfiles: Use pubspec.lock to strictly pin fvm's dependency versions. Commit the lockfile.
* Private Repositories: Prioritize trusted, private package repositories for fvm and its dependencies.
* Dependency Auditing: Regularly audit fvm's dependencies for vulnerabilities.
Attack Surface: 3. Malicious Flutter SDK Installation (via fvm command)
Description: Attackers use fvm commands to install a compromised or malicious Flutter SDK.
How fvm Contributes: fvm is the direct tool used to perform the malicious installation. This is distinct from .fvmrc manipulation, where fvm is used indirectly.
Example: An attacker with access to a developer's terminal or a CI/CD script executes fvm install <malicious-sdk-version> or fvm use <malicious-sdk-version>.
Impact: The compiled application contains vulnerabilities from the malicious SDK, leading to potential exploits.
Risk Severity: Critical
Mitigation Strategies:
* Command Auditing: Audit and monitor fvm commands executed in CI/CD environments and on developer machines.
* Restricted Shell Access: Limit shell access to CI/CD servers and developer machines to authorized personnel only.
* Least Privilege: Run CI/CD processes and developer tools with the least necessary privileges.
* Input Validation (for CI/CD): If SDK versions are provided as input to CI/CD pipelines, strictly validate and sanitize these inputs.
Attack Surface: 4. Cache Poisoning (of fvm's cache)
Description: Attackers with write access to the fvm cache directory replace legitimate SDK files with malicious ones.
How fvm Contributes: fvm's caching mechanism is the direct target. The attacker leverages fvm's reliance on the cache.
Example: An attacker gains access to a CI/CD server and modifies the contents of the fvm cache, replacing a legitimate Flutter SDK.
Impact: Subsequent builds using the poisoned cache result in a vulnerable application.
Risk Severity: High
Mitigation Strategies:
* Strict Permissions: Enforce very restrictive permissions on the fvm cache directory, allowing write access only to the specific user account running fvm.
* Isolated Build Environments: Use isolated build environments (e.g., Docker containers) to minimize the risk and impact of cache poisoning. Each build should ideally start with a clean cache.
* Cache Clearing: Regularly clear the fvm cache, especially before critical builds.
* Immutable Caches (Ideal): If possible, configure the build environment to treat the cache as read-only after the initial download.