better go mod detection from partial package builds (#3060)

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

syft/pkg/cataloger/golang/parse_go_binary.go

@@ -11,6 +11,7 @@ import (
 	"io"
 	"regexp"
 	"runtime/debug"
+	"slices"
 	"strings"
 	"time"
 
@@ -97,17 +98,19 @@ func createModuleRelationships(main pkg.Package, deps []pkg.Package) []artifact.
 	return relationships
 }
 
+var emptyModule debug.Module
+var moduleFromPartialPackageBuild = debug.Module{Path: "command-line-arguments"}
+
 func (c *goBinaryCataloger) buildGoPkgInfo(resolver file.Resolver, location file.Location, mod *extendedBuildInfo, arch string, reader io.ReadSeekCloser) (*pkg.Package, []pkg.Package) {
-	var pkgs []pkg.Package
 	if mod == nil {
-		return nil, pkgs
+		return nil, nil
 	}
 
-	var empty debug.Module
-	if mod.Main == empty && mod.Path != "" {
-		mod.Main = createMainModuleFromPath(mod.Path)
+	if missingMainModule(mod) {
+		mod.Main = createMainModuleFromPath(mod)
 	}
 
+	var pkgs []pkg.Package
 	for _, dep := range mod.Deps {
 		if dep == nil {
 			continue
@@ -130,7 +133,7 @@ func (c *goBinaryCataloger) buildGoPkgInfo(resolver file.Resolver, location file
 		}
 	}
 
-	if mod.Main == empty {
+	if mod.Main == emptyModule {
 		return nil, pkgs
 	}
 
@@ -139,6 +142,16 @@ func (c *goBinaryCataloger) buildGoPkgInfo(resolver file.Resolver, location file
 	return &main, pkgs
 }
 
+func missingMainModule(mod *extendedBuildInfo) bool {
+	if mod.Main == emptyModule && mod.Path != "" {
+		return true
+	}
+	// special case: when invoking go build with a source file and not a package (directory) then you will
+	// see "command-line-arguments" as the main module path... even though that's not the main module. In this
+	// circumstance, we should treat the main module as missing and search for it within the dependencies.
+	return mod.Main == moduleFromPartialPackageBuild
+}
+
 func (c *goBinaryCataloger) makeGoMainPackage(resolver file.Resolver, mod *extendedBuildInfo, arch string, location file.Location, reader io.ReadSeekCloser) pkg.Package {
 	gbs := getBuildSettings(mod.Settings)
 	gover, experiments := getExperimentsFromVersion(mod.GoVersion)
@@ -358,8 +371,29 @@ func getExperimentsFromVersion(version string) (string, []string) {
 	return version, experiments
 }
 
-func createMainModuleFromPath(path string) (mod debug.Module) {
-	mod.Path = path
-	mod.Version = devel
-	return
+func createMainModuleFromPath(existing *extendedBuildInfo) debug.Module {
+	// search for a main module candidate within the dependencies
+	var mainModuleCandidates []debug.Module
+	var usedIndex int
+	for i, dep := range existing.Deps {
+		if dep == nil {
+			continue
+		}
+
+		if dep.Version == devel {
+			usedIndex = i
+			mainModuleCandidates = append(mainModuleCandidates, *dep)
+		}
+	}
+	if len(mainModuleCandidates) == 1 {
+		// we need to prune the dependency from module list
+		existing.Deps = slices.Delete(existing.Deps, usedIndex, usedIndex+1)
+		return mainModuleCandidates[0]
+	}
+
+	// otherwise craft a main module from the path (a bit of a cop out, but allows us to have a main module)
+	return debug.Module{
+		Path:    existing.Path,
+		Version: devel,
+	}
 }

syft/pkg/cataloger/golang/parse_go_binary_test.go

@@ -210,7 +210,7 @@ func TestBuildGoPkgInfo(t *testing.T) {
 		},
 		{
 			name:     "buildGoPkgInfo parses a blank mod and returns no packages",
-			mod:      &extendedBuildInfo{&debug.BuildInfo{}, nil, ""},
+			mod:      &extendedBuildInfo{BuildInfo: &debug.BuildInfo{}, cryptoSettings: nil, arch: ""},
 			expected: []pkg.Package(nil),
 		},
 		{
@@ -946,6 +946,95 @@ func TestBuildGoPkgInfo(t *testing.T) {
 				},
 			}},
 		},
+		{
+			name: "parse a mod from path (partial build of package)",
+			mod: &extendedBuildInfo{
+				BuildInfo: &debug.BuildInfo{
+					GoVersion: "go1.22.2",
+					Main:      debug.Module{Path: "command-line-arguments"},
+					Settings: []debug.BuildSetting{
+						{
+							Key:   "-ldflags",
+							Value: `build	-ldflags="-w -s     -X github.com/kuskoman/logstash-exporter/config.Version=v1.7.0     -X github.com/kuskoman/logstash-exporter/config.GitCommit=db696dbcfe5a91d288d5ad44ce8ccbea97e65978     -X github.com/kuskoman/logstash-exporter/config.BuildDate=2024-07-17T08:12:17Z"`,
+						},
+						{Key: "GOARCH", Value: archDetails},
+						{Key: "GOOS", Value: "darwin"},
+						{Key: "GOAMD64", Value: "v1"},
+					},
+					Deps: []*debug.Module{
+						{
+							Path:    "github.com/kuskoman/something-else",
+							Version: "v1.2.3",
+						},
+						{
+							Path:    "github.com/kuskoman/logstash-exporter",
+							Version: "(devel)",
+						},
+					},
+				},
+				arch: archDetails,
+			},
+			expected: []pkg.Package{
+				{
+					Name:     "github.com/kuskoman/something-else",
+					Language: pkg.Go,
+					Type:     pkg.GoModulePkg,
+					Version:  "v1.2.3",
+					PURL:     "pkg:golang/github.com/kuskoman/something-else@v1.2.3",
+					Locations: file.NewLocationSet(
+						file.NewLocationFromCoordinates(
+							file.Coordinates{
+								RealPath:     "/a-path",
+								FileSystemID: "layer-id",
+							},
+						).WithAnnotation(pkg.EvidenceAnnotationKey, pkg.PrimaryEvidenceAnnotation),
+					),
+					Metadata: pkg.GolangBinaryBuildinfoEntry{
+						GoCompiledVersion: "go1.22.2",
+						Architecture:      archDetails,
+						MainModule:        "github.com/kuskoman/logstash-exporter", // correctly attached the main module
+					},
+				},
+				{
+					Name:     "github.com/kuskoman/logstash-exporter",
+					Language: pkg.Go,
+					Type:     pkg.GoModulePkg,
+					Version:  "v1.7.0",
+					PURL:     "pkg:golang/github.com/kuskoman/logstash-exporter@v1.7.0",
+					Locations: file.NewLocationSet(
+						file.NewLocationFromCoordinates(
+							file.Coordinates{
+								RealPath:     "/a-path",
+								FileSystemID: "layer-id",
+							},
+						).WithAnnotation(pkg.EvidenceAnnotationKey, pkg.PrimaryEvidenceAnnotation),
+					),
+					Metadata: pkg.GolangBinaryBuildinfoEntry{
+						GoCompiledVersion: "go1.22.2",
+						BuildSettings: []pkg.KeyValue{
+							{
+								Key:   "-ldflags",
+								Value: `build	-ldflags="-w -s     -X github.com/kuskoman/logstash-exporter/config.Version=v1.7.0     -X github.com/kuskoman/logstash-exporter/config.GitCommit=db696dbcfe5a91d288d5ad44ce8ccbea97e65978     -X github.com/kuskoman/logstash-exporter/config.BuildDate=2024-07-17T08:12:17Z"`,
+							},
+							{
+								Key:   "GOARCH",
+								Value: "amd64",
+							},
+							{
+								Key:   "GOOS",
+								Value: "darwin",
+							},
+							{
+								Key:   "GOAMD64",
+								Value: "v1",
+							},
+						},
+						Architecture: archDetails,
+						MainModule:   "github.com/kuskoman/logstash-exporter",
+					},
+				},
+			},
+		},
 	}
 
 	for _, test := range tests {
@@ -1092,6 +1181,12 @@ func Test_extractVersionFromLDFlags(t *testing.T) {
 			wantMajorVersion: "6",
 			wantFullVersion:  "v6.1.7",
 		},
+		{
+			name:             "logstash-exporter",
+			ldflags:          `build	-ldflags="-w -s     -X github.com/kuskoman/logstash-exporter/config.Version=v1.7.0     -X github.com/kuskoman/logstash-exporter/config.GitCommit=db696dbcfe5a91d288d5ad44ce8ccbea97e65978     -X github.com/kuskoman/logstash-exporter/config.BuildDate=2024-07-17T08:12:17Z"`,
+			wantMajorVersion: "1",
+			wantFullVersion:  "v1.7.0",
+		},
 		//////////////////////////////////////////////////////////////////
 		// negative cases
 		{

syft/pkg/cataloger/golang/scan_binary.go

@@ -56,7 +56,7 @@ func scanFile(reader unionreader.UnionReader, filename string) []*extendedBuildI
 			}
 		}
 
-		builds = append(builds, &extendedBuildInfo{bi, v, arch})
+		builds = append(builds, &extendedBuildInfo{BuildInfo: bi, cryptoSettings: v, arch: arch})
 	}
 	return builds
 }