From: Tomas Mraz <tmraz@fedoraproject.org>
Date: Tue, 18 Dec 2018 15:32:13 +0000 (+0100)
Subject: usermod: Guard against unsafe change of ownership of home directory content
X-Git-Tag: 4.7~13^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=refs%2Fpull%2F143%2Fhead;p=thirdparty%2Fshadow.git

usermod: Guard against unsafe change of ownership of home directory content

In case the home directory is not a real home directory
(owned by the user) but things like / or /var or similar,
it is unsafe to change ownership of home directory content.

The test checks whether the home directory is owned by the
user him/herself, if not no ownership modification of contents
is performed.
---

diff --git a/src/usermod.c b/src/usermod.c
index 72eeb8b2e..68775272d 100644
--- a/src/usermod.c
+++ b/src/usermod.c
@@ -2313,7 +2313,10 @@ int main (int argc, char **argv)
 	}
 
 	if (!mflg && (uflg || gflg)) {
-		if (access (dflg ? prefix_user_newhome : prefix_user_home, F_OK) == 0) {
+		struct stat sb;
+
+		if (stat (dflg ? prefix_user_newhome : prefix_user_home, &sb) == 0 &&
+			((uflg && sb.st_uid == user_newid) || sb.st_uid == user_id)) {
 			/*
 			 * Change the UID on all of the files owned by
 			 * `user_id' to `user_newid' in the user's home