[libvirt] [PATCH 2/2] virsh: Don't attempt polkit processing for non local authn/authz

[John Ferlan]

https://bugzilla.redhat.com/show_bug.cgi?id=1374126

Due to how the processing for authentication using polkit works, the
virshConnect code must first "attempt" an virConnectOpenAuth and then
check for a "special" return error code VIR_ERR_AUTH_UNAVAILABLE in
order to attempt to "retry" the authentication after performing a creation
of a pkttyagent to handle the challenge/response for the client.

However, attempting to use a remote connection, (such as perhaps
"qemu+ssh://someuser@localhost/system"), will cause a never ending
loop since attempting to generate a pkttyagent would fail for the
network client connection resulting in a never ending loop since the
return code is always VIR_ERR_AUTH_UNAVAILABLE from virPolkitCheckAuth.
The only way out of the loop is a forced quit (e.g. ctrl-c) as the
@authfail wouldn't be incremented as a result of a failed authn from
pkttyagent.

So rather than take any extra step for which the only result will be
a failure, let's check if there is a URI and if it's not using ":///",
then just fail.

This resolves the never ending loop and will generate an error:

error: failed to connect to the hypervisor
error: authentication unavailable: no polkit agent available to authenticate action 'org.libvirt.unix.manage'

NB: If the authentication was for a sufficiently privileged client, such as
qemu+ssh://root@localhost/system, then the remoteDispatchAuthList "allows"
the authentication to use libvirt since @callerUid would be 0.

Signed-off-by: John Ferlan <jferlan at redhat.com>
---
 tools/virsh.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/virsh.c b/tools/virsh.c
index 1f5c2b1..be368ba 100644
--- a/tools/virsh.c
+++ b/tools/virsh.c
@@ -166,6 +166,11 @@ virshConnect(vshControl *ctl, const char *uri, bool readonly)
         if (readonly)
             goto cleanup;
 
+        /* No URI or indication of a requesting a remote connection, then
+         * polkit will not work for the authentication/authorization */
+        if (!uri || !(strstr(uri, ":///")))
+            goto cleanup;
+
         err = virGetLastError();
         if (!agentCreated &&
             err && err->domain == VIR_FROM_POLKIT &&
-- 
2.9.3