Summary
BundlePack currently allows packages with up to 20 GiB of expanded data, while the compression-ratio guard only rejects archives larger than 1 GiB whose integer ratio exceeds 1,000. A structurally valid package can therefore consume most or all of a system volume during extraction.
On macOS, the current flow validates and expands into a temporary directory and then copies the payload to the final destination, so peak disk usage can approach twice the expanded size.
Impact
Opening and extracting an attacker-controlled but structurally valid package can exhaust the system or destination volume and disrupt BundlePack or other processes.
Evidence
Windows/BundlePack.Core/BundlePackConstants.cs:20-23Windows/BundlePack.Core/BundlePackArchive.Validation.cs:236-241macOS/BundlePack/Shared/ZipArchiveInspector.Validation.swift:219-225macOS/BundlePack/App/PackageBuilder.swift:221-299
Reproduction outline
Create a valid archive whose expanded total is below 20 GiB and whose overall compression ratio is at most 1,000. A mix of highly compressible zero-filled files and a small amount of incompressible data can satisfy the current checks while causing large writes.
The audit did not generate the full-size fixture; the pass conditions are confirmed from the validation code.
Proposed change
- Preflight available capacity before extraction.
- Check temporary and destination volumes independently on macOS.
- Include a safety margin and currently existing files in the budget.
- Require explicit caller confirmation above a documented high-expansion threshold.
- Add practical per-entry and total compression-ratio policy without silently changing the v1 numeric field layout.
Acceptance criteria
- Extraction fails before writing payload bytes when capacity is insufficient.
- Capacity checks are injectable and testable without allocating multi-GiB fixtures.
- Boundary tests cover exact limit, limit minus one, and limit plus one.
- Cancellation and failure leave no published partial destination.
Docs/FORMAT.md documents any reader policy limit changed by the fix.
Compatibility constraints
Do not silently change the v1 20 GiB field representation, ZIP32 layout, CRC and actual-size validation, or the requirement to extract only the reviewed archive bytes.
Summary
BundlePack currently allows packages with up to 20 GiB of expanded data, while the compression-ratio guard only rejects archives larger than 1 GiB whose integer ratio exceeds 1,000. A structurally valid package can therefore consume most or all of a system volume during extraction.
On macOS, the current flow validates and expands into a temporary directory and then copies the payload to the final destination, so peak disk usage can approach twice the expanded size.
Impact
Opening and extracting an attacker-controlled but structurally valid package can exhaust the system or destination volume and disrupt BundlePack or other processes.
Evidence
Windows/BundlePack.Core/BundlePackConstants.cs:20-23Windows/BundlePack.Core/BundlePackArchive.Validation.cs:236-241macOS/BundlePack/Shared/ZipArchiveInspector.Validation.swift:219-225macOS/BundlePack/App/PackageBuilder.swift:221-299Reproduction outline
Create a valid archive whose expanded total is below 20 GiB and whose overall compression ratio is at most 1,000. A mix of highly compressible zero-filled files and a small amount of incompressible data can satisfy the current checks while causing large writes.
The audit did not generate the full-size fixture; the pass conditions are confirmed from the validation code.
Proposed change
Acceptance criteria
Docs/FORMAT.mddocuments any reader policy limit changed by the fix.Compatibility constraints
Do not silently change the v1 20 GiB field representation, ZIP32 layout, CRC and actual-size validation, or the requirement to extract only the reviewed archive bytes.