add ParseSignature

README.md

@@ -109,6 +109,24 @@ err := verifier.VerifyWithActor("https://yodangang.express/@juunini")
 err := verifier.VerifyWithBody([]byte("{...}"))
 ```
 
+### Parse `Signature` header
+
+```go
+import (
+  signature_header "github.com/cloudmatelabs/go-activitypub-signature-header"
+)
+
+// map[string]string
+params := signature_header.ParseSignature(signature)
+// or given Signature authorization header
+// params := signature_header.ParseSignature(authorization)
+
+params["keyId"]
+params["algorithm"]
+params["headers"]
+params["signature"]
+```
+
 ## License
 
 [MIT](LICENSE)

signature.go

@@ -62,3 +62,20 @@ digest: %s`,
 		fmt.Sprintf(`signature="%s"`, signature),
 	}, ","), nil
 }
+
+func ParseSignature(signatureStr string) map[string]string {
+	parsedSignature := map[string]string{}
+
+	for _, param := range strings.Split(strings.Replace(signatureStr, "Signature ", "", 1), ",") {
+		split := strings.Split(param, "=")
+		key := split[0]
+		value := strings.ReplaceAll(
+			strings.Join(split[1:], "="),
+			`"`, "",
+		)
+
+		parsedSignature[key] = value
+	}
+
+	return parsedSignature
+}

test/signature_test.go

@@ -0,0 +1,63 @@
+package signature_header_test
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+
+	signature_header "github.com/cloudmatelabs/go-activitypub-signature-header"
+)
+
+var (
+	keyId         = `https://snippet.social/@juunini#main-key`
+	algorithm     = `rsa-sha256`
+	_headers      = `(request-target) date host digest`
+	signatureHash = "g99dh20dygasd=="
+)
+
+var signature = strings.Join([]string{
+	fmt.Sprintf(`keyId="%s"`, keyId),
+	fmt.Sprintf(`algorithm="%s"`, algorithm),
+	fmt.Sprintf(`headers="%s"`, headers),
+	fmt.Sprintf(`signature="%s"`, signatureHash),
+}, ",")
+
+func Test_ParseSignature(t *testing.T) {
+	params := signature_header.ParseSignature(signature)
+
+	if params["algorithm"] != algorithm {
+		t.Errorf("Algorithm is not correct: %s", params["algorithm"])
+	}
+
+	if params["keyId"] != keyId {
+		t.Errorf("KeyID is not correct: %s", params["keyId"])
+	}
+
+	if params["signature"] != signatureHash {
+		t.Errorf("Signature is not correct: %s", params["signature"])
+	}
+
+	if params["headers"] != _headers {
+		t.Errorf("Headers is not correct: %s", params["headers"])
+	}
+}
+
+func Test_ParseSignature_WithAuthorization(t *testing.T) {
+	params := signature_header.ParseSignature("Signature " + signature)
+
+	if params["algorithm"] != algorithm {
+		t.Errorf("Algorithm is not correct: %s", params["algorithm"])
+	}
+
+	if params["keyId"] != keyId {
+		t.Errorf("KeyID is not correct: %s", params["keyId"])
+	}
+
+	if params["signature"] != signatureHash {
+		t.Errorf("Signature is not correct: %s", params["signature"])
+	}
+
+	if params["headers"] != _headers {
+		t.Errorf("Headers is not correct: %s", params["headers"])
+	}
+}