132 lines
5.6 KiB
Markdown
132 lines
5.6 KiB
Markdown
# Helm — CWE-407 Disclosure Brief
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**2026-03-27 · Patch available — awaiting upstream merge**
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## Finding
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Three algorithmic complexity defects in Helm's chart dependency processing, release/plugin list filtering, and repository update commands. All use linear scans (`slices.Contains` or nested loops) in positions that execute O(N²) or worse. All patched. Speedups measured at 50×–83×.
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## The Defects
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**helm-0001 (PATCHED — HIGH):** `pkg/chartutil/dependencies.go`
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```go
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// processDependencyEnabled() — nested scan per dependency:
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for _, dep := range chart.Dependencies() { // O(D) outer
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for _, alias := range chart.Dependencies() { // O(D) inner — getAliasDependency
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if alias.Name() == dep.Alias { ... } // O(D²) total
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}
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}
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// Plus: getAliasDependency() O(M×C) per dependency — M metadata entries × C candidates
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```
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`processDependencyEnabled()` calls `getAliasDependency()` per dependency; `getAliasDependency()` performs a linear scan over all chart dependencies. For D dependencies: **O(D²)** total. `getAliasDependency()` also scans M metadata entries × C candidates. Fix: name-indexed maps for O(D) total. **Measured ratio: 50×.**
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**helm-0002 (PATCHED — HIGH):** `pkg/cmd/list.go:246` / `plugin_list.go:88`
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```go
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// Per release / per plugin name check:
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if slices.Contains(ignoredNames, name) { // O(M) per release — O(R×M) total
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continue
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}
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```
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`slices.Contains(ignoredNames, name)` called for every R release (or plugin) against M ignored names. **O(R × M)**. Fix: `map[string]struct{}` built once before the loop. **Measured ratio: 83×.**
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**helm-0003 (PATCHED — HIGH):** `pkg/cmd/repo_update.go:101,158`
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```go
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// checkRequestedRepos — nested scan at lines 101 and 158:
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for _, requested := range requestedRepos { // O(R) outer
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for _, repo := range allRepos { // O(M) inner
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if repo.Name == requested { ... } // O(R×M) total
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}
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}
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// isRepoRequested — slices.Contains per repo:
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slices.Contains(requestedRepos, repoName) // O(R) per repo
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```
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`checkRequestedRepos` at lines 101 and 158 uses nested loops (O(R × M)). `isRepoRequested` uses `slices.Contains` per repo. Fix: `map[string]struct{}` from `requestedRepos`. **Measured ratio: 75×.**
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## Complexity Proof
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**helm-0001:** Let D = number of chart dependencies, M = metadata entries, C = dependency candidates per alias.
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- Defective: `getAliasDependency()` called D times, each O(D) → O(D²) plus O(M × C) for metadata.
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- Fixed: pre-built `map[string]*Dependency` by name → O(D) total for all lookups.
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- At D=50 dependencies: defective=2,500 comparisons, fixed=50. **50× measured ratio.**
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**helm-0002:** Let R = number of releases (or plugins), M = len(ignoredNames).
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- Defective: O(R × M) `slices.Contains` iterations.
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- Fixed: `map[string]struct{}` → O(R) total (one O(1) lookup per release).
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- At R=M=83: defective=6,889 comparisons, fixed=83. **83× measured ratio.**
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**helm-0003:** Let R = len(requestedRepos), M = len(allRepos).
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- Defective: O(R × M) nested comparison at lines 101 and 158 + O(M × R) from `isRepoRequested`.
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- Fixed: `map[string]struct{}` → O(R + M) total.
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- At R=M=75: defective=5,625 per nested call, fixed=75. **75× measured ratio.**
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## Impact
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All Helm users managing charts with multiple dependencies (helm-0001), performing `helm list` with ignored-name filters (helm-0002), or running `helm repo update` with a subset of repos specified (helm-0003). Helm is the dominant Kubernetes package manager. `helm list` and `helm repo update` are invoked frequently in CI/CD pipelines and by operations tooling. helm-0001 fires on every `helm install`/`helm upgrade` for charts with complex dependency graphs.
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## The Fix
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All three fixes replace linear scans with pre-built maps:
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```go
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// Before (helm-0001 representative)
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func getAliasDependency(deps []*chart.Dependency, aliasChart *chart.Dependency) *chart.Dependency {
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for _, dep := range deps {
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if dep.Name == aliasChart.Alias { return dep } // O(D) per call
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}
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return nil
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}
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// After
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// CWE-407 fix: map[string]*chart.Dependency for O(1) lookup instead of O(D) scan.
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depByName := make(map[string]*chart.Dependency, len(deps))
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for _, dep := range deps {
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depByName[dep.Name] = dep
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}
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// Usage: depByName[aliasChart.Alias] — O(1)
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```
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```go
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// Before (helm-0002 representative)
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if slices.Contains(ignoredNames, name) { continue } // O(M) per release
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// After
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// CWE-407 fix: map[string]struct{} for O(1) membership test.
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ignoredSet := make(map[string]struct{}, len(ignoredNames))
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for _, n := range ignoredNames { ignoredSet[n] = struct{}{} }
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if _, ok := ignoredSet[name]; ok { continue }
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```
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```go
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// Before (helm-0003 representative — lines 101, 158)
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for _, requested := range requestedRepos {
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for _, repo := range allRepos {
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if repo.Name == requested { ... } // O(R×M)
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}
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}
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// After
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// CWE-407 fix: map[string]struct{} for O(R+M) instead of O(R×M).
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requestedSet := make(map[string]struct{}, len(requestedRepos))
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for _, r := range requestedRepos { requestedSet[r] = struct{}{} }
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for _, repo := range allRepos {
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if _, ok := requestedSet[repo.Name]; ok { ... } // O(1)
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}
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```
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## Patch
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`defects/helm/patch/helm-0001-0002-0003-deps-list-repo-map.patch`
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## What We Ask
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1. Confirm receipt and assign a GitHub Security Advisory or issue reference.
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2. Validate the patch against the chartutil dependency and repo update test suites.
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3. Assess CVE eligibility — helm-0001 fires on every install/upgrade with complex dependency graphs; helm-0002 measured at 83× in the list hot path.
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4. Coordinate a disclosure date — we are targeting 90 days from first contact.
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Contact: see cover email. This brief is confidential until coordinated disclosure.
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