fix(prose/golang): access response headers while processing reponse body

Previously, we were accessing ContentType header of the request, while
attempting to analyze the body of both request and response. Now, we correctly
save and access response headers for response body, while still using request
headers for request body.

privacy-profile-composer/pkg/envoyfilter/filter.go

@@ -32,7 +32,8 @@ type Filter struct {
 
 	// Runtime state of the filter
 	parentSpanContext model.SpanContext
-	headerMetadata    common.HeaderMetadata
+	reqHeaderMetadata common.RequestHeaderMetadata
+	resHeaderMetadata common.ResponseHeaderMetadata
 	thirdPartyURL     string
 	processDecodeBody bool
 	decodeDataBuffer  string
@@ -52,7 +53,7 @@ func (f *Filter) DecodeHeaders(header api.RequestHeaderMap, endStream bool) api.
 	span.Tag("SIDECAR_DIRECTION", string(f.config.direction))
 	span.Tag("DATA_FLOW", "DECODE_HEADERS")
 
-	f.headerMetadata = common.ExtractHeaderData(header)
+	f.reqHeaderMetadata = common.ExtractRequestHeaderData(header)
 
 	// common.LogDecodeHeaderData(header)
 
@@ -88,7 +89,7 @@ func (f *Filter) DecodeHeaders(header api.RequestHeaderMap, endStream bool) api.
 			return api.Continue
 		}
 
-		f.thirdPartyURL = f.headerMetadata.Host
+		f.thirdPartyURL = f.reqHeaderMetadata.Host
 		f.processDecodeBody = true
 
 	default:
@@ -169,6 +170,8 @@ func (f *Filter) EncodeHeaders(header api.ResponseHeaderMap, endStream bool) api
 	span.Tag("SIDECAR_DIRECTION", string(f.config.direction))
 	span.Tag("DATA_FLOW", "ENCODE_HEADERS")
 
+	f.resHeaderMetadata = common.ExtractResponseHeaderData(header)
+
 	if endStream {
 		// here we have a header-only request
 		return api.Continue
@@ -262,14 +265,21 @@ func (f *Filter) processBody(ctx context.Context, body string, isDecode bool) (s
 
 	proseTags[PROSE_SIDECAR_DIRECTION] = string(f.config.direction)
 
-	jsonBody, err := common.GetJSONBody(ctx, f.headerMetadata, body)
+	var contentType *string
+	if isDecode {
+		contentType = f.reqHeaderMetadata.ContentType
+	} else {
+		contentType = f.resHeaderMetadata.ContentType
+	}
+
+	jsonBody, err := common.GetJSONBody(ctx, contentType, body)
 	if err != nil {
 		proseTags[PROSE_JSON_BODY_ERROR] = fmt.Sprintf("%s", err)
 		return false, err, proseTags
 	}
 
 	// Run Presidio and add tags for PII types or an error from Presidio
-	piiTypes, err := common.PiiAnalysis(ctx, f.config.presidioUrl, f.headerMetadata.SvcName, jsonBody)
+	piiTypes, err := common.PiiAnalysis(ctx, f.config.presidioUrl, f.reqHeaderMetadata.SvcName, jsonBody)
 	if err != nil {
 		proseTags[PROSE_PRESIDIO_ERROR] = fmt.Sprintf("%s", err)
 		return false, err, proseTags

privacy-profile-composer/pkg/envoyfilter/internal/common/packet_processing.go

@@ -14,7 +14,7 @@ import (
 const anyPurpose = "ANY"
 const unknownSvcName = "UNKNOWN SVC"
 
-type HeaderMetadata struct {
+type RequestHeaderMetadata struct {
 	Host   string
 	Method string
 	Path   string
@@ -27,6 +27,11 @@ type HeaderMetadata struct {
 	Purpose string
 }
 
+type ResponseHeaderMetadata struct {
+	ContentType   *string
+	ContentLength *string
+}
+
 type SidecarDirection string
 
 const (
@@ -51,8 +56,8 @@ func LogEncodeHeaderData(header api.ResponseHeaderMap) {
 	//})
 }
 
-func ExtractHeaderData(header api.RequestHeaderMap) HeaderMetadata {
-	metadata := HeaderMetadata{
+func ExtractRequestHeaderData(header api.RequestHeaderMap) RequestHeaderMetadata {
+	metadata := RequestHeaderMetadata{
 		Host:   header.Host(),
 		Method: header.Method(),
 		Path:   header.Path(),
@@ -99,6 +104,22 @@ func ExtractHeaderData(header api.RequestHeaderMap) HeaderMetadata {
 	return metadata
 }
 
+func ExtractResponseHeaderData(headers api.ResponseHeaderMap) ResponseHeaderMetadata {
+	metadata := ResponseHeaderMetadata{}
+
+	contentType, exists := headers.Get("content-type")
+	if exists {
+		metadata.ContentType = &contentType
+	}
+
+	contentLength, exists := headers.Get("content-length")
+	if exists {
+		metadata.ContentLength = &contentLength
+	}
+
+	return metadata
+}
+
 func GetDirection(callbacks api.FilterCallbackHandler) (SidecarDirection, error) {
 	directionEnum, err := callbacks.GetProperty("xds.listener_direction")
 	if err != nil {
@@ -128,15 +149,15 @@ func GetDirection(callbacks api.FilterCallbackHandler) (SidecarDirection, error)
 		"check the Envoy docs for the range of values for this key", directionInt)
 }
 
-func GetJSONBody(ctx context.Context, headerMetadata HeaderMetadata, body string) (interface{}, error) {
+func GetJSONBody(ctx context.Context, contentType *string, body string) (interface{}, error) {
 	span, ctx := GlobalTracer.StartSpanFromContext(ctx, "getJSONBody")
 	defer span.Finish()
 
-	if headerMetadata.ContentType == nil {
+	if contentType == nil {
 		return nil, fmt.Errorf("cannot analyze body, since 'ContentType' header is not set")
 	}
 
-	switch *headerMetadata.ContentType {
+	switch *contentType {
 	case "application/json":
 		var data interface{}
 
@@ -154,6 +175,6 @@ func GetJSONBody(ctx context.Context, headerMetadata HeaderMetadata, body string
 
 		return query, nil
 	default:
-		return nil, fmt.Errorf("cannot analyze a body with ContentType '%s'", *headerMetadata.ContentType)
+		return nil, fmt.Errorf("cannot analyze a body with ContentType '%s'", *contentType)
 	}
 }