fix: correct APK CPE version comparison logic

Previously, the -r{buildindex} suffix of APK package versions were
treated as pre-release versions per the fuzzy matcher logic; however,
these should be treated as equivalent to the release version for the
purposes of collecting CPE-based matches for APK packages.

We may want to make a similar change in syft to generate cleaner CPE
versions for APK packages, but making the change in grype corrects
behaviour for previously-generated SBOMs as well.

Signed-off-by: Weston Steimel <[email protected]>

grype/matcher/apk/matcher.go

@@ -2,6 +2,7 @@ package apk
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/anchore/grype/grype/distro"
 	"github.com/anchore/grype/grype/match"
@@ -45,7 +46,8 @@ func (m *Matcher) Match(store vulnerability.Provider, d *distro.Distro, p pkg.Pa
 
 func (m *Matcher) cpeMatchesWithoutSecDBFixes(store vulnerability.Provider, d *distro.Distro, p pkg.Package) ([]match.Match, error) {
 	// find CPE-indexed vulnerability matches specific to the given package name and version
-	cpeMatches, err := search.ByPackageCPE(store, p, m.Type())
+	cpePackage := cpeComparablePackage(p)
+	cpeMatches, err := search.ByPackageCPE(store, cpePackage, m.Type())
 	if err != nil {
 		return nil, err
 	}
@@ -101,6 +103,36 @@ cveLoop:
 	return finalCpeMatches, nil
 }
 
+func cpeComparablePackage(p pkg.Package) pkg.Package {
+	// clean the alpine package version so that it compares correctly with the CPE version comparison logic
+	// alpine versions are suffixed with -r{buildindex}; however, if left intact CPE comparison logic will
+	// incorrectly treat these as a pre-release.  In actuality, we just want to treat 1.2.3-r21 as equivalent to
+	// 1.2.3 for purposes of CPE-based matching since the alpine fix should filter out any cases where a later
+	// build fixes something that was vulnerable in 1.2.3
+	components := strings.Split(p.Version, "-r")
+	cpeComparableVersion := p.Version
+
+	if len(components) == 2 {
+		cpeComparableVersion = components[0]
+	}
+
+	if cpeComparableVersion == p.Version {
+		return p
+	}
+
+	t := p
+	t.Version = cpeComparableVersion
+	t.CPEs = nil
+	t.CPEs = append(t.CPEs, p.CPEs...)
+
+	for index, cpe := range t.CPEs {
+		cpe.Version = cpeComparableVersion
+		t.CPEs[index] = cpe
+	}
+
+	return t
+}
+
 func deduplicateMatches(secDBMatches, cpeMatches []match.Match) (matches []match.Match) {
 	// add additional unique matches from CPE source that is unique from the SecDB matches
 	secDBMatchesByID := matchesByID(secDBMatches)