Source added

app/jni/utils/org_thoughtcrime_securesms_util_FileUtils.cpp

@@ -0,0 +1,45 @@
+#include "org_thoughtcrime_securesms_util_FileUtils.h"
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <linux/memfd.h>
+#include <syscall.h>
+
+jint JNICALL Java_org_thoughtcrime_securesms_util_FileUtils_getFileDescriptorOwner
+  (JNIEnv *env, jclass clazz, jobject fileDescriptor)
+{
+  jclass fdClass = env->GetObjectClass(fileDescriptor);
+
+  if (fdClass == NULL) {
+    return -1;
+  }
+
+  jfieldID fdFieldId = env->GetFieldID(fdClass, "descriptor", "I");
+
+  if (fdFieldId == NULL) {
+    return -1;
+  }
+
+  int fd = env->GetIntField(fileDescriptor, fdFieldId);
+
+  struct stat stat_struct;
+
+  if (fstat(fd, &stat_struct) != 0) {
+    return -1;
+  }
+
+  return stat_struct.st_uid;
+}
+
+JNIEXPORT jint JNICALL Java_org_thoughtcrime_securesms_util_FileUtils_createMemoryFileDescriptor
+  (JNIEnv *env, jclass clazz, jstring jname)
+{
+  const char *name = env->GetStringUTFChars(jname, NULL);
+
+  int fd = syscall(SYS_memfd_create, name, MFD_CLOEXEC);
+
+  env->ReleaseStringUTFChars(jname, name);
+
+  return fd;
+}