feat(cooldown): respect trusted_packages in dependency cooldown (#342)

* feat(cooldown): respect trusted_packages in dependency cooldown

Trusted packages are now treated as a superset waiver that bypasses every
PMG control (malware analysis, cooldown, and any future controls). A
globally trusted package is automatically exempt from the cooldown window
and no longer needs a duplicate entry in dependency_cooldown.skip.

The skip list remains the narrower, cooldown-only waiver for packages
that must bypass the cooldown wait but still be malware-scanned.

* refactor(cooldown): tag skip reason and audit-log skipped packages

Address review feedback on #342:

- Restore cooldownSkip to a pure single-list function (SRP); the merge
  into trusted_packages now happens in a separate mergeCooldownSkip step,
  driven by the exported CooldownSkip wrapper.
- Extend CooldownSkipInfo with a CooldownSkipReason (TrustedPackage /
  CooldownSkipList) on both SkipAll and per-version entries, so callers
  can tell apart the broad waiver from the cooldown-only one. When both
  lists match the same package, trusted_packages wins.
- Add audit.LogCooldownSkipped and emit it from the npm and PyPI
  interceptors on the SkipAll path, alongside the existing info log,
  carrying the source list as the reason.

* refactor(cooldown): inline list merge, audit per-version exemptions

Address further review feedback:

- Drop the separate mergeCooldownSkip helper; cooldownSkip now writes
  into a shared *CooldownSkipInfo and is called twice from CooldownSkip
  (cooldown skip list first, trusted_packages on top so trusted entries
  override the reason on overlap).
- Audit log every exemption, not just SkipAll: a new auditCooldownSkip
  helper in proxy/interceptors/cooldown.go emits one event per match
  (package-wide or per-version), each tagged with its source list.
  LogCooldownSkipped gains a version argument for the per-version case.
- Cover the trusted_packages reason path in TestCooldownSkip.

* fix(cooldown): avoid double-auditing trusted package exemptions

auditCooldownSkip now only emits EventTypeCooldownSkipped for entries
that came from dependency_cooldown.skip. Trusted-package exemptions
already get an EventTypeInstallTrustedAllowed event at tarball-download
time (proxy/interceptors/base_registry.go), so emitting a cooldown event
for them too would double-count the same waiver.

* emit trusted and cooldown skip events to cloud

* fix tests

* refactor(cooldown): return value from collectCooldownSkip, short-circuit on trusted SkipAll

Address PR review feedback:
- Rename cooldownSkip to collectCooldownSkip and return CooldownSkipInfo
  instead of mutating an input pointer.
- Add mergeCooldownSkip to combine per-list results with trusted_packages
  taking precedence on overlap.
- CooldownSkip now consults trusted_packages first and returns immediately
  on a package-wide trusted exemption (DC skip list cannot add anything).
- Extend tests to cover disjoint pinned entries across both lists and the
  case where DC version-less subsumes a trusted pinned entry.

* fix(audit): address cooldown review feedback

* fix(cooldown): audit cooldown skips at download time with concrete version

Backend rejects PackageVersion messages without a version, and audit logs
should reflect the runtime fact (a specific version was skipped) rather
than the config rule. Move the audit emission from metadata-request
handling to download-request handling, where the concrete version is
known, and require version in LogCooldownSkipped.

* chore(audit): drop dead scope assignment in LogCooldownSkipped

* refactor(cooldown): move skip-list logic into cooldown handlers

Registry interceptors no longer compute CooldownSkip or branch on SkipAll;
they just call HandleMetadataRequest. The npm and pypi cooldown handlers
own the skip lookup, the package-wide exemption short-circuit, and (for
pypi) the canonical-name denormalization. Also align LogCooldownSkipped
with other LogXxx signatures by taking *packagev1.PackageVersion.

* fix: Simplify audit logging for dependency cooldown skip

* refactor: Simplify cooldown handling and maintain separation of concepts for trusted and DC skip packages

* fix: Code review fixes

* fix: Emit cooldown skipped audit event ONLY when an in-window version is skipped

---------

Co-authored-by: Abhisek Datta <abhisek.datta@gmail.com>

proxy/interceptors/npm_cooldown.go

@@ -8,6 +8,7 @@ import (
 
 	packagev1 "buf.build/gen/go/safedep/api/protocolbuffers/go/safedep/messages/package/v1"
 	"github.com/safedep/dry/log"
+	pmgconfig "github.com/safedep/pmg/config"
 	"github.com/safedep/pmg/proxy"
 )
 
@@ -32,8 +33,17 @@ func newNpmCooldownHandler(statsCollector *AnalysisStatsCollector) *npmCooldownH
 
 // HandleMetadataRequest overrides the Accept header to force the registry to return
 // a full packument (which includes publish dates in the "time" field), then registers
-// a response modifier that strips versions within the cooldown window.
-func (h *npmCooldownHandler) HandleMetadataRequest(ctx *proxy.RequestContext, packageName string, cooldownDays int, pinnedVersion string, exemptVersions map[string]bool) (*proxy.InterceptorResponse, error) {
+// a response modifier that strips versions within the cooldown window. Skip-list
+// semantics are handled here so callers do not need to consult the config.
+func (h *npmCooldownHandler) HandleMetadataRequest(ctx *proxy.RequestContext, packageName string, cooldownDays int, pinnedVersion string) (*proxy.InterceptorResponse, error) {
+	skip := pmgconfig.CooldownSkip(packagev1.Ecosystem_ECOSYSTEM_NPM, packageName)
+	if skip.SkipAll {
+		// Whole package is on the cooldown skip list: pass metadata through
+		// unmodified. The tarball download still hits analyzePackage, so malware
+		// analysis is preserved.
+		return &proxy.InterceptorResponse{Action: proxy.ActionAllow}, nil
+	}
+
 	log.Debugf("[%s] Cooldown: registering metadata modifier for %s", ctx.RequestID, packageName)
 
 	// Force full packument so the response always contains the "time" field.
@@ -62,7 +72,9 @@ func (h *npmCooldownHandler) HandleMetadataRequest(ctx *proxy.RequestContext, pa
 
 		log.Debugf("[%s] Cooldown: parsed %d publish dates for %s", ctx.RequestID, len(dates), packageName)
 
-		strippedBody, stripped, remaining := h.stripCooldownVersions(body, dates, cooldownDays, exemptVersions)
+		exempt := cooldownExemptVersions(packagev1.Ecosystem_ECOSYSTEM_NPM, packageName, skip, dates, cooldownDays)
+		auditCooldownSkips(ctx.RequestID, packagev1.Ecosystem_ECOSYSTEM_NPM, packageName, exempt)
+		strippedBody, stripped, remaining := h.stripCooldownVersions(body, dates, cooldownDays, exempt.all)
 		if stripped > 0 {
 			log.Infof("[%s] Cooldown: stripped %d version(s) from %s metadata (%d days, %d eligible remain)",
 				ctx.RequestID, stripped, packageName, cooldownDays, remaining)