(f) DRY: loadPayload across MB.Load, loadEnvelope, LoadMetadata

Signed-off-by: Aditya Sirish <aditya@saky.in>
in-toto · May 3, 2023 · 4cbd94d · 4cbd94d
1 parent cd9d2ff
commit 4cbd94d
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Showing 4 changed files with 60 additions and 131 deletions.
diff --git a/in_toto/envelope.go b/in_toto/envelope.go
@@ -7,8 +7,6 @@ import (
 	"errors"
 	"fmt"
 	"os"
-	"reflect"
-	"strings"
 
 	"github.com/secure-systems-lab/go-securesystemslib/cjson"
 	"github.com/secure-systems-lab/go-securesystemslib/dsse"
@@ -28,10 +26,18 @@ type Envelope struct {
 
 func loadEnvelope(env *dsse.Envelope) (*Envelope, error) {
 	e := &Envelope{envelope: env}
-	if err := e.loadPayload(); err != nil {
+
+	contentBytes, err := env.DecodeB64Payload()
+	if err != nil {
 		return nil, err
 	}
 
+	payload, err := loadPayload(contentBytes)
+	if err != nil {
+		return nil, err
+	}
+	e.payload = payload
+
 	return e, nil
 }
 
@@ -54,48 +60,6 @@ func (e *Envelope) GetPayload() any {
 	return e.payload
 }
 
-func (e *Envelope) loadPayload() error {
-	payloadBytes, err := e.envelope.DecodeB64Payload()
-	if err != nil {
-		return fmt.Errorf("error decoding payload: %w", err)
-	}
-
-	var payload map[string]any
-	if err := json.Unmarshal(payloadBytes, &payload); err != nil {
-		return fmt.Errorf("error decoding payload: %w", err)
-	}
-
-	if payload["_type"] == "link" {
-		var link Link
-		if err := checkRequiredJSONFields(payload, reflect.TypeOf(link)); err != nil {
-			return fmt.Errorf("error decoding payload: %w", err)
-		}
-
-		decoder := json.NewDecoder(strings.NewReader(string(payloadBytes)))
-		decoder.DisallowUnknownFields()
-		if err := decoder.Decode(&link); err != nil {
-			return fmt.Errorf("error decoding payload: %w", err)
-		}
-
-		e.payload = link
-	} else if payload["_type"] == "layout" {
-		var layout Layout
-		if err := checkRequiredJSONFields(payload, reflect.TypeOf(layout)); err != nil {
-			return fmt.Errorf("error decoding payload: %w", err)
-		}
-
-		decoder := json.NewDecoder(strings.NewReader(string(payloadBytes)))
-		decoder.DisallowUnknownFields()
-		if err := decoder.Decode(&layout); err != nil {
-			return fmt.Errorf("error decoding payload: %w", err)
-		}
-
-		e.payload = layout
-	}
-
-	return nil
-}
-
 func (e *Envelope) VerifySignature(key Key) error {
 	verifier, err := getSignerVerifierFromKey(key)
 	if err != nil {

diff --git a/in_toto/model.go b/in_toto/model.go
@@ -728,50 +728,12 @@ func LoadMetadata(path string) (Metadata, error) {
 		return nil, err
 	}
 
-	// Temporarily copy signed to opaque map to inspect the `_type` of signed
-	// and create link or layout accordingly
-	var signed map[string]interface{}
-	if err := json.Unmarshal(*rawData["signed"], &signed); err != nil {
+	payload, err := loadPayload(*rawData["signed"])
+	if err != nil {
 		return nil, err
 	}
 
-	if signed["_type"] == "link" {
-		var link Link
-		if err := checkRequiredJSONFields(signed, reflect.TypeOf(link)); err != nil {
-			return nil, err
-		}
-
-		data, err := rawData["signed"].MarshalJSON()
-		if err != nil {
-			return nil, err
-		}
-		decoder := json.NewDecoder(strings.NewReader(string(data)))
-		decoder.DisallowUnknownFields()
-		if err := decoder.Decode(&link); err != nil {
-			return nil, err
-		}
-		mb.Signed = link
-
-	} else if signed["_type"] == "layout" {
-		var layout Layout
-		if err := checkRequiredJSONFields(signed, reflect.TypeOf(layout)); err != nil {
-			return nil, err
-		}
-
-		data, err := rawData["signed"].MarshalJSON()
-		if err != nil {
-			return nil, err
-		}
-		decoder := json.NewDecoder(strings.NewReader(string(data)))
-		decoder.DisallowUnknownFields()
-		if err := decoder.Decode(&layout); err != nil {
-			return nil, err
-		}
-
-		mb.Signed = layout
-	} else {
-		return nil, fmt.Errorf("the '_type' field of the 'signed' part of in-toto metadata must be one of 'link' or 'layout'")
-	}
+	mb.Signed = payload
 
 	return mb, nil
 }
@@ -873,52 +835,12 @@ func (mb *Metablock) Load(path string) error {
 		return err
 	}
 
-	// Temporarily copy signed to opaque map to inspect the `_type` of signed
-	// and create link or layout accordingly
-	var signed map[string]interface{}
-	if err := json.Unmarshal(*rawMb["signed"], &signed); err != nil {
+	payload, err := loadPayload(*rawMb["signed"])
+	if err != nil {
 		return err
 	}
 
-	if signed["_type"] == "link" {
-		var link Link
-		if err := checkRequiredJSONFields(signed, reflect.TypeOf(link)); err != nil {
-			return err
-		}
-
-		data, err := rawMb["signed"].MarshalJSON()
-		if err != nil {
-			return err
-		}
-		decoder := json.NewDecoder(strings.NewReader(string(data)))
-		decoder.DisallowUnknownFields()
-		if err := decoder.Decode(&link); err != nil {
-			return err
-		}
-		mb.Signed = link
-
-	} else if signed["_type"] == "layout" {
-		var layout Layout
-		if err := checkRequiredJSONFields(signed, reflect.TypeOf(layout)); err != nil {
-			return err
-		}
-
-		data, err := rawMb["signed"].MarshalJSON()
-		if err != nil {
-			return err
-		}
-		decoder := json.NewDecoder(strings.NewReader(string(data)))
-		decoder.DisallowUnknownFields()
-		if err := decoder.Decode(&layout); err != nil {
-			return err
-		}
-
-		mb.Signed = layout
-
-	} else {
-		return fmt.Errorf("the '_type' field of the 'signed' part of in-toto" +
-			" metadata must be one of 'link' or 'layout'")
-	}
+	mb.Signed = payload
 
 	return nil
 }

diff --git a/in_toto/model_test.go b/in_toto/model_test.go
@@ -103,7 +103,7 @@ func TestMetablockLoad(t *testing.T) {
 		"requires 'signed' and 'signatures' parts",
 		"cannot unmarshal string into Go value of type []in_toto.Signature",
 		"cannot unmarshal array into Go value of type map[string]interface {}",
-		"metadata must be one of 'link' or 'layout'",
+		ErrUnknownMetadataType.Error(),
 		"cannot unmarshal string into Go struct field Link.materials",
 		"cannot unmarshal string into Go struct field Layout.steps",
 		"required field steps missing",
@@ -1667,7 +1667,7 @@ func TestLoadMetadata(t *testing.T) {
 		"requires 'signed' and 'signatures' parts",
 		"cannot unmarshal string into Go value of type []in_toto.Signature",
 		"cannot unmarshal array into Go value of type map[string]interface {}",
-		"metadata must be one of 'link' or 'layout'",
+		ErrUnknownMetadataType.Error(),
 		"cannot unmarshal string into Go struct field Link.materials",
 		"cannot unmarshal string into Go struct field Layout.steps",
 		"required field steps missing",

diff --git a/in_toto/util.go b/in_toto/util.go
@@ -1,9 +1,15 @@
 package in_toto
 
 import (
+	"encoding/json"
+	"errors"
 	"fmt"
+	"reflect"
+	"strings"
 )
 
+var ErrUnknownMetadataType = errors.New("unknown metadata type encountered: not link or layout")
+
 /*
 Set represents a data structure for set operations. See `NewSet` for how to
 create a Set, and available Set receivers for useful set operations.
@@ -145,3 +151,40 @@ func (s Set) IsSubSet(subset Set) bool {
 	}
 	return true
 }
+
+func loadPayload(payloadBytes []byte) (any, error) {
+	var payload map[string]any
+	if err := json.Unmarshal(payloadBytes, &payload); err != nil {
+		return nil, fmt.Errorf("error decoding payload: %w", err)
+	}
+
+	if payload["_type"] == "link" {
+		var link Link
+		if err := checkRequiredJSONFields(payload, reflect.TypeOf(link)); err != nil {
+			return nil, fmt.Errorf("error decoding payload: %w", err)
+		}
+
+		decoder := json.NewDecoder(strings.NewReader(string(payloadBytes)))
+		decoder.DisallowUnknownFields()
+		if err := decoder.Decode(&link); err != nil {
+			return nil, fmt.Errorf("error decoding payload: %w", err)
+		}
+
+		return link, nil
+	} else if payload["_type"] == "layout" {
+		var layout Layout
+		if err := checkRequiredJSONFields(payload, reflect.TypeOf(layout)); err != nil {
+			return nil, fmt.Errorf("error decoding payload: %w", err)
+		}
+
+		decoder := json.NewDecoder(strings.NewReader(string(payloadBytes)))
+		decoder.DisallowUnknownFields()
+		if err := decoder.Decode(&layout); err != nil {
+			return nil, fmt.Errorf("error decoding payload: %w", err)
+		}
+
+		return layout, nil
+	}
+
+	return nil, ErrUnknownMetadataType
+}