The only way object_property_add() can fail is when a property with
the same name already exists. Since our property names are all
hardcoded, failure is a programming error, and the appropriate way to
handle it is passing &error_abort.
Same for its variants, except for object_property_add_child(), which
additionally fails when the child already has a parent. Parentage is
also under program control, so this is a programming error, too.
We have a bit over 500 callers. Almost half of them pass
&error_abort, slightly fewer ignore errors, one test case handles
errors, and the remaining few callers pass them to their own callers.
The previous few commits demonstrated once again that ignoring
programming errors is a bad idea.
Of the few ones that pass on errors, several violate the Error API.
The Error ** argument must be NULL, &error_abort, &error_fatal, or a
pointer to a variable containing NULL. Passing an argument of the
latter kind twice without clearing it in between is wrong: if the
first call sets an error, it no longer points to NULL for the second
call. ich9_pm_add_properties(), sparc32_ledma_realize(),
sparc32_dma_realize(), xilinx_axidma_realize(), xilinx_enet_realize()
are wrong that way.
When the one appropriate choice of argument is &error_abort, letting
users pick the argument is a bad idea.
Drop parameter @errp and assert the preconditions instead.
There's one exception to "duplicate property name is a programming
error": the way object_property_add() implements the magic (and
undocumented) "automatic arrayification". Don't drop @errp there.
Instead, rename object_property_add() to object_property_try_add(),
and add the obvious wrapper object_property_add().
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20200505152926.18877-15-armbru@redhat.com>
[Two semantic rebase conflicts resolved]
Include the generated trace.h the same way as we do everywhere else.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190315145123.28030-3-armbru@redhat.com>
Acked-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Add an authorization backend that talks to PAM to check whether the user
identity is allowed. This only uses the PAM account validation facility,
which is essentially just a check to see if the provided username is permitted
access. It doesn't use the authentication or session parts of PAM, since
that's dealt with by the relevant part of QEMU (eg VNC server).
Consider starting QEMU with a VNC server and telling it to use TLS with
x509 client certificates and configuring it to use an PAM to validate
the x509 distinguished name. In this example we're telling it to use PAM
for the QAuthZ impl with a service name of "qemu-vnc"
$ qemu-system-x86_64 \
-object tls-creds-x509,id=tls0,dir=/home/berrange/security/qemutls,\
endpoint=server,verify-peer=yes \
-object authz-pam,id=authz0,service=qemu-vnc \
-vnc :1,tls-creds=tls0,tls-authz=authz0
This requires an /etc/pam/qemu-vnc file to be created with the auth
rules. A very simple file based whitelist can be setup using
$ cat > /etc/pam/qemu-vnc <<EOF
account requisite pam_listfile.so item=user sense=allow file=/etc/qemu/vnc.allow
EOF
The /etc/qemu/vnc.allow file simply contains one username per line. Any
username not in the file is denied. The usernames in this example are
the x509 distinguished name from the client's x509 cert.
$ cat > /etc/qemu/vnc.allow <<EOF
CN=laptop.berrange.com,O=Berrange Home,L=London,ST=London,C=GB
EOF
More interesting would be to configure PAM to use an LDAP backend, so
that the QEMU authorization check data can be centralized instead of
requiring each compute host to have file maintained.
The main limitation with this PAM module is that the rules apply to all
QEMU instances on the host. Setting up different rules per VM, would
require creating a separate PAM service name & config file for every
guest. An alternative approach for the future might be to not pass in
the plain username to PAM, but instead combine the VM name or UUID with
the username. This requires further consideration though.
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Markus Armbruster