fix(proxy): multiple analysis of truncated body (#3981)

Co-authored-by: Eliott Bouhana <[email protected]>

Author: e-n-0

instrumentation/appsec/proxy/body_buffer.go

@@ -10,6 +10,7 @@ type bodyBuffer struct {
 	buffer    []byte
 	sizeLimit int
 	truncated bool
+	analyzed  bool
 }
 
 // newBodyBuffer creates a new bodyBuffer with the specified size limit

instrumentation/appsec/proxy/message_processor.go

@@ -278,9 +278,14 @@ func (mp *Processor[O]) OnResponseTrailers(_ *RequestState) (*O, error) {
 }
 
 func processBody(ctx context.Context, bodyBuffer *bodyBuffer, body []byte, eos bool, analyzeBody func(ctx context.Context, encodable any) error) error {
+	if bodyBuffer.analyzed {
+		return nil
+	}
+
 	bodyBuffer.append(body)
 
 	if eos || bodyBuffer.truncated {
+		bodyBuffer.analyzed = true
 		return analyzeBody(ctx, json.NewEncodableFromData(bodyBuffer.buffer, bodyBuffer.truncated))
 	}