🐛 bug: Fix MIME type equality checks (#3602)

Author: gaby

helpers.go

@@ -245,9 +245,12 @@ func acceptsOfferType(spec, offerType string, specParams headerParams) bool {
 	}
 
 	s := strings.IndexByte(mimetype, '/')
+	specSlash := strings.IndexByte(spec, '/')
 	// Accept: <MIME_type>/*
-	if strings.HasPrefix(spec, mimetype[:s]) && (spec[s:] == "/*" || mimetype[s:] == "/*") {
-		return paramsMatch(specParams, offerParams)
+	if s != -1 && specSlash != -1 {
+		if utils.EqualFold(spec[:specSlash], mimetype[:s]) && (spec[specSlash:] == "/*" || mimetype[s:] == "/*") {
+			return paramsMatch(specParams, offerParams)
+		}
 	}
 
 	return false

helpers_test.go

@@ -243,6 +243,12 @@ func Test_Utils_AcceptsOfferType(t *testing.T) {
 			offerType:   "application/xml",
 			accepts:     false,
 		},
+		{
+			description: "mismatch with subtype prefix",
+			spec:        "application/json",
+			offerType:   "application/json+xml",
+			accepts:     false,
+		},
 		{
 			description: "params match",
 			spec:        "application/json",