Setuid programs triggering upcalls could trick the program here. Also,
the d_automount method is done with credentials overridden so if you
can end up with mismatched creds and env vars due to that as well.
It's a hack, but the only recourse I can see is to avoid doing this
when the uid is 0. That means we can rely on this for getting to root's
credcache, but hopefully that's not a huge issue.
Reported-by: Chad William Seys <cwseys@xxxxxxxxxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxx>
---
cifs.upcall.8.in | 5 ++++-
cifs.upcall.c | 10 +++++++++-
2 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/cifs.upcall.8.in b/cifs.upcall.8.in
index e1f3956e176a..81481a482fb4 100644
--- a/cifs.upcall.8.in
+++ b/cifs.upcall.8.in
@@ -44,7 +44,10 @@ Normally, cifs.upcall will probe the environment variable space of the process
that initiated the upcall in order to fetch the value of $KRB5CCNAME. This can
assist the program with finding credential caches in non-default locations. If
this option is set, then the program won't do this and will rely on finding
-credcaches in the default locations specified in krb5.conf.
+credcaches in the default locations specified in krb5.conf. Note that this is
+never performed when the uid is 0. The default credcache location is always
+used when the uid is 0, regardless of the environment variable setting in the
+process.
.RE
.PP
\--krb5conf=/path/to/krb5.conf|-k /path/to/krb5.conf
diff --git a/cifs.upcall.c b/cifs.upcall.c
index f766a8b5799e..8f6bb761a27e 100644
--- a/cifs.upcall.c
+++ b/cifs.upcall.c
@@ -1018,11 +1018,19 @@ int main(const int argc, char *const argv[])
}
/*
+ * We can't reasonably do this for root. Mounting a DFS share, for
+ * instance we can end up with creds being overridden, but the env
+ * variable left intact.
+ */
+ if (uid == 0)
+ env_probe = false;
+
+ /*
* Must do this before setuid, as we need elevated capabilities to
* look at the environ file.
*/
env_cachename =
- get_cachename_from_process_env(env_probe ? arg.pid : 0);
+ get_cachename_from_process_env(env_probe ? arg.pid : 0);
rc = setuid(uid);
if (rc == -1) {
--
2.9.3
--
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