From d4dda9b5583d19e2eee268fec59aa487d61fc079 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Valent=C3=ADn=20Guti=C3=A9rrez?= <vgutierrez@wikimedia.org>
Date: Thu, 21 Nov 2024 03:54:03 +0100
Subject: [PATCH] Invoke initgroups() iff we got enough privileges (#11869)
 (#11872)

Follow up of #11855, that rendered unusable ATS as root when spawned via traffic_manager.
---
 src/tscore/ink_cap.cc | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/tscore/ink_cap.cc b/src/tscore/ink_cap.cc
index 0f0d6f869e2..f464daad3b1 100644
--- a/src/tscore/ink_cap.cc
+++ b/src/tscore/ink_cap.cc
@@ -156,8 +156,10 @@ impersonate(const struct passwd *pwd, ImpersonationLevel level)
 #endif
 
   // Always repopulate the supplementary group list for the new user.
-  if (initgroups(pwd->pw_name, pwd->pw_gid) != 0) {
-    Fatal("switching to user %s, failed to initialize supplementary groups ID %ld", pwd->pw_name, (long)pwd->pw_gid);
+  if (geteuid() == 0) { // check that we have enough rights to call initgroups()
+    if (initgroups(pwd->pw_name, pwd->pw_gid) != 0) {
+      Fatal("switching to user %s, failed to initialize supplementary groups ID %ld", pwd->pw_name, (long)pwd->pw_gid);
+    }
   }
 
   switch (level) {
