From: Todd C. Miller <Todd.Miller@courtesan.com>
Date: Mon, 18 Jan 2016 20:12:50 +0000 (-0700)
Subject: Need to be root when switching to a different user.
X-Git-Tag: SUDO_1_8_16^2~62
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=4b96e94f37f89f741cbeaeb84a7d3d02b88a130e;p=sudo

Need to be root when switching to a different user.
---

diff --git a/src/sudo_edit.c b/src/sudo_edit.c
index 6e7162423..c63d4b603 100644
--- a/src/sudo_edit.c
+++ b/src/sudo_edit.c
@@ -254,8 +254,21 @@ dir_is_writable(int dfd, struct user_details *ud, struct command_details *cd)
     debug_decl(dir_is_writable, SUDO_DEBUG_EDIT)
     int rc;
 
+    /* Change uid/gid/groups to invoking user, usually needs root perms. */
+    if (cd->euid != ROOT_UID) {
+	if (seteuid(ROOT_UID) != 0)
+	    sudo_fatal("seteuid(ROOT_UID)");
+    }
     switch_user(ud->uid, ud->gid, ud->ngroups, ud->groups);
+
+    /* Access checks are done using the euid/egid and group vector. */
     rc = faccessat(dfd, ".", W_OK, AT_EACCESS);
+
+    /* Change uid/gid/groups back to target user, may need root perms. */
+    if (ud->uid != ROOT_UID) {
+	if (seteuid(ROOT_UID) != 0)
+	    sudo_fatal("seteuid(ROOT_UID)");
+    }
     switch_user(cd->euid, cd->egid, cd->ngroups, cd->groups);
 
     if (rc == 0)