Merge pull request #50 from puerco/context-parse

Light parse VEX data to find Context locator

Author: puerco

pkg/vex/vex.go

@@ -12,7 +12,6 @@ import (
 	"fmt"
 	"io"
 	"os"
-	"regexp"
 	"sort"
 	"strconv"
 	"strings"
@@ -58,11 +57,6 @@ const (
 // documents and nodes. It is set to the OpenVEX public namespace by default.
 var DefaultNamespace = PublicNamespace
 
-var (
-	contextRegExpPattern = fmt.Sprintf(`"@context":\s+"(%s\S*)"`, Context)
-	contextRegExp        *regexp.Regexp
-)
-
 // The VEX type represents a VEX document and all of its contained information.
 type VEX struct {
 	Metadata
@@ -265,28 +259,38 @@ func SortDocuments(docs []*VEX) []*VEX {
 	return docs
 }
 
+// parseContext light parses a JSON document to look for the OpenVEX context locator
+func parseContext(rawDoc []byte) (string, error) {
+	pd := struct {
+		Context string `json:"@context"`
+	}{}
+
+	if err := json.Unmarshal(rawDoc, &pd); err != nil {
+		return "", fmt.Errorf("parsing context from json data: %w", err)
+	}
+
+	if strings.HasPrefix(pd.Context, Context) {
+		return pd.Context, nil
+	}
+	return "", nil
+}
+
 // Open tries to autodetect the vex format and open it
 func Open(path string) (*VEX, error) {
 	data, err := os.ReadFile(path)
 	if err != nil {
 		return nil, fmt.Errorf("opening VEX file: %w", err)
 	}
 
-	if bytes.Contains(data, []byte(ContextLocator())) {
-		logrus.Info("opening current vex")
-		return Parse(data)
-	} else if bytes.Contains(data, []byte(Context)) {
-		logrus.Info("Opening older openvex")
-		if contextRegExp == nil {
-			contextRegExp = regexp.MustCompile(contextRegExpPattern)
-		}
-
-		res := contextRegExp.FindSubmatch(data)
-		if len(res) == 0 {
-			return nil, fmt.Errorf("unable to parse OpenVEX version in document context")
-		}
+	documentContextLocator, err := parseContext(data)
+	if err != nil {
+		return nil, err
+	}
 
-		version := strings.TrimPrefix(string(res[1]), Context)
+	if documentContextLocator == ContextLocator() {
+		return Parse(data)
+	} else if documentContextLocator != "" {
+		version := strings.TrimPrefix(documentContextLocator, Context)
 		version = strings.TrimPrefix(version, "/")
 
 		// If version is nil, then we assume v0.0.1

pkg/vex/vex_test.go

@@ -413,3 +413,24 @@ func TestDocumentMatches(t *testing.T) {
 		require.Equal(t, tc.numMatches, len(matches), fmt.Sprintf("failed: %s", testCase))
 	}
 }
+
+func TestParseContext(t *testing.T) {
+	for tCase, tc := range map[string]struct {
+		docData   string
+		expected  string
+		shouldErr bool
+	}{
+		"Normal":        {`{"@context": "https://openvex.dev/ns"}`, "https://openvex.dev/ns", false},
+		"Other JSON":    {`{"document": { "category": "csaf_vex" } }`, "", false},
+		"Invalid JSON":  {`@context": "https://openvex.dev/ns`, "", true},
+		"Other json-ld": {`{"@context": "https://spdx.dev/"}`, "", false},
+	} {
+		res, err := parseContext([]byte(tc.docData))
+		if tc.shouldErr {
+			require.Error(t, err, tCase)
+			continue
+		}
+		require.NoError(t, err, tCase)
+		require.Equal(t, res, tc.expected, tCase)
+	}
+}