[v5,09/11] authz: add QAuthZListFile object type for a file access control list

Add a QAuthZListFile object type that implements the QAuthZ interface. This
built-in implementation is a proxy around the QAtuhZList object type,
initializing it from an external file, and optionally, automatically
reloading it whenever it changes.

To create an instance of this object via the QMP monitor, the syntax
used would be:

      {
        "execute": "object-add",
        "arguments": {
          "qom-type": "authz-list-file",
          "id": "authz0",
          "parameters": {
            "filename": "/etc/qemu/vnc.acl",
	    "refresh": "yes"
          }
        }
      }

If "refresh" is "yes", inotify is used to monitor the file,
automatically reloading changes. If an error occurs during reloading,
all authorizations will fail until the file is next successfully
loaded.

The /etc/qemu/vnc.acl file would contain a JSON representation of a
QAuthZList object

    {
      "rules": [
         { "match": "fred", "policy": "allow", "format": "exact" },
         { "match": "bob", "policy": "allow", "format": "exact" },
         { "match": "danb", "policy": "deny", "format": "glob" },
         { "match": "dan*", "policy": "allow", "format": "exact" },
      ],
      "policy": "deny"
    }

This sets up an authorization rule that allows 'fred', 'bob' and anyone
whose name starts with 'dan', except for 'danb'. Everyone unmatched is
denied.

The object can be loaded on the comand line using

   -object authz-list-file,id=authz0,filename=/etc/qemu/vnc.acl,refresh=yes

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 authz/Makefile.objs      |   1 +
 authz/listfile.c         | 284 +++++++++++++++++++++++++++++++++++++++
 authz/trace-events       |   4 +
 include/authz/listfile.h | 110 +++++++++++++++
 qemu-options.hx          |  47 +++++++
 5 files changed, 446 insertions(+)
 create mode 100644 authz/listfile.c
 create mode 100644 include/authz/listfile.h

On 09/10/2018 15:04, Daniel P. Berrangé wrote:
> Add a QAuthZListFile object type that implements the QAuthZ interface. This
> built-in implementation is a proxy around the QAtuhZList object type,
> initializing it from an external file, and optionally, automatically
> reloading it whenever it changes.
> 
> To create an instance of this object via the QMP monitor, the syntax
> used would be:
> 
>       {
>         "execute": "object-add",
>         "arguments": {
>           "qom-type": "authz-list-file",
>           "id": "authz0",
>           "parameters": {
>             "filename": "/etc/qemu/vnc.acl",
> 	    "refresh": "yes"
>           }
>         }
>       }
> 
> If "refresh" is "yes", inotify is used to monitor the file,
> automatically reloading changes. If an error occurs during reloading,
> all authorizations will fail until the file is next successfully
> loaded.
> 
> The /etc/qemu/vnc.acl file would contain a JSON representation of a
> QAuthZList object
> 
>     {
>       "rules": [
>          { "match": "fred", "policy": "allow", "format": "exact" },
>          { "match": "bob", "policy": "allow", "format": "exact" },
>          { "match": "danb", "policy": "deny", "format": "glob" },
>          { "match": "dan*", "policy": "allow", "format": "exact" },
>       ],
>       "policy": "deny"
>     }
> 
> This sets up an authorization rule that allows 'fred', 'bob' and anyone
> whose name starts with 'dan', except for 'danb'. Everyone unmatched is
> denied.
> 
> The object can be loaded on the comand line using
> 
>    -object authz-list-file,id=authz0,filename=/etc/qemu/vnc.acl,refresh=yes
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  authz/Makefile.objs      |   1 +
>  authz/listfile.c         | 284 +++++++++++++++++++++++++++++++++++++++
>  authz/trace-events       |   4 +
>  include/authz/listfile.h | 110 +++++++++++++++
>  qemu-options.hx          |  47 +++++++
>  5 files changed, 446 insertions(+)
>  create mode 100644 authz/listfile.c
>  create mode 100644 include/authz/listfile.h
> 
> diff --git a/authz/Makefile.objs b/authz/Makefile.objs
> index 921fa624d7..8351bf181d 100644
> --- a/authz/Makefile.objs
> +++ b/authz/Makefile.objs
> @@ -1,3 +1,4 @@
>  authz-obj-y += base.o
>  authz-obj-y += simple.o
>  authz-obj-y += list.o
> +authz-obj-y += listfile.o
> diff --git a/authz/listfile.c b/authz/listfile.c
> new file mode 100644
> index 0000000000..5bd3e37f7e
> --- /dev/null
> +++ b/authz/listfile.c
> @@ -0,0 +1,284 @@
> +/*
> + * QEMU access control list file authorization driver
> + *
> + * Copyright (c) 2018 Red Hat, Inc.
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, see <http://www.gnu.org/licenses/>.
> + *
> + */
> +
> +#include "qemu/osdep.h"
> +#include "authz/listfile.h"
> +#include "authz/trace.h"
> +#include "qemu/error-report.h"
> +#include "qemu/main-loop.h"
> +#include "qemu/sockets.h"
> +#include "qemu/filemonitor.h"
> +#include "qom/object_interfaces.h"
> +#include "qapi/qapi-visit-authz.h"
> +#include "qapi/qmp/qjson.h"
> +#include "qapi/qmp/qobject.h"
> +#include "qapi/qmp/qerror.h"
> +#include "qapi/qobject-input-visitor.h"
> +
> +
> +static bool
> +qauthz_list_file_is_allowed(QAuthZ *authz,
> +                            const char *identity,
> +                            Error **errp)
> +{
> +    QAuthZListFile *fauthz = QAUTHZ_LIST_FILE(authz);
> +    if (fauthz->list) {
> +        return qauthz_is_allowed(fauthz->list, identity, errp);
> +    }
> +
> +    return false;
> +}
> +
> +
> +static QAuthZ *
> +qauthz_list_file_load(QAuthZListFile *fauthz, Error **errp)
> +{
> +    GError *err = NULL;
> +    gchar *content = NULL;
> +    gsize len;
> +    QObject *obj = NULL;
> +    QDict *pdict;
> +    Visitor *v = NULL;
> +    QAuthZ *ret = NULL;
> +
> +    trace_qauthz_list_file_load(fauthz, fauthz->filename);
> +    if (!g_file_get_contents(fauthz->filename, &content, &len, &err)) {
> +        error_setg(errp, "Unable to read '%s': %s",
> +                   fauthz->filename, err->message);
> +        goto cleanup;
> +    }
> +
> +    obj = qobject_from_json(content, errp);
> +    if (!obj) {
> +        goto cleanup;
> +    }
> +
> +    pdict = qobject_to(QDict, obj);
> +    if (!pdict) {
> +        error_setg(errp, QERR_INVALID_PARAMETER_TYPE, "obj", "dict");
> +        goto cleanup;
> +    }
> +
> +    v = qobject_input_visitor_new(obj);
> +
> +    ret = (QAuthZ *)user_creatable_add_type(TYPE_QAUTHZ_LIST,
> +                                            NULL, pdict, v, errp);
> +
> + cleanup:
> +    visit_free(v);
> +    qobject_unref(obj);
> +    if (err) {
> +        g_error_free(err);
> +    }
> +    g_free(content);
> +    return ret;
> +}
> +
> +
> +static void
> +qauthz_list_file_event(int wd G_GNUC_UNUSED,
> +                       QFileMonitorEvent ev G_GNUC_UNUSED,
> +                       const char *name G_GNUC_UNUSED,
> +                       void *opaque)
> +{
> +    QAuthZListFile *fauthz = opaque;
> +    Error *err = NULL;
> +
> +    if (ev != QFILE_MONITOR_EVENT_MODIFIED &&
> +        ev != QFILE_MONITOR_EVENT_CREATED)

You missed:

                                              {

> +        return;

       }

> +
> +    object_unref(OBJECT(fauthz->list));
> +    fauthz->list = qauthz_list_file_load(fauthz, &err);
> +    trace_qauthz_list_file_refresh(fauthz,
> +                                   fauthz->filename, fauthz->list ? 1 : 0);
> +    if (!fauthz->list) {
> +        error_report_err(err);
> +    }
> +}
> +
> +static void
> +qauthz_list_file_complete(UserCreatable *uc, Error **errp)
> +{
> +    QAuthZListFile *fauthz = QAUTHZ_LIST_FILE(uc);
> +
> +    fauthz->list = qauthz_list_file_load(fauthz, errp);
> +
> +    if (fauthz->refresh) {

Can we invert this condition?

> +        gchar *dir, *file;
> +        fauthz->file_monitor = qemu_file_monitor_get_instance(errp);
> +        if (!fauthz->file_monitor) {
> +            return;
> +        }
> +
> +        dir = g_path_get_dirname(fauthz->filename);
> +        if (g_str_equal(dir, ".")) {
> +            error_setg(errp, "Filename must be an absolute path");

What about:

               goto cleanup;

> +            g_free(dir);
> +            return;
> +        }
> +        file = g_path_get_basename(fauthz->filename);
> +        if (g_str_equal(file, ".")) {
> +            error_setg(errp, "Path has no trailing filename component");

               goto cleanup;

> +            g_free(file);
> +            g_free(dir);
> +            return;
> +        }
> +
> +        fauthz->file_watch = qemu_file_monitor_add_watch(
> +            fauthz->file_monitor, dir, file,
> +            qauthz_list_file_event, fauthz, errp);
> +        g_free(file);
> +        g_free(dir);
> +        if (fauthz->file_watch < 0) {

Is this really useful? Do you plan to add more code here?

> +            return;
> +        }
> +    }
> +}
> +
> +
> +static void
> +qauthz_list_file_prop_set_filename(Object *obj,
> +                                   const char *value,
> +                                   Error **errp G_GNUC_UNUSED)
> +{
> +    QAuthZListFile *authz = QAUTHZ_LIST_FILE(obj);
> +
> +    authz->filename = g_strdup(value);
> +}
> +
> +
> +static char *
> +qauthz_list_file_prop_get_filename(Object *obj,
> +                                   Error **errp G_GNUC_UNUSED)
> +{
> +    QAuthZListFile *authz = QAUTHZ_LIST_FILE(obj);
> +
> +    return g_strdup(authz->filename);
> +}
> +
> +
> +static void
> +qauthz_list_file_prop_set_refresh(Object *obj,
> +                                  bool value,
> +                                  Error **errp G_GNUC_UNUSED)
> +{
> +    QAuthZListFile *authz = QAUTHZ_LIST_FILE(obj);
> +
> +    authz->refresh = value;
> +}
> +
> +
> +static bool
> +qauthz_list_file_prop_get_refresh(Object *obj,
> +                                  Error **errp G_GNUC_UNUSED)
> +{
> +    QAuthZListFile *authz = QAUTHZ_LIST_FILE(obj);
> +
> +    return authz->refresh;
> +}
> +
> +
> +static void
> +qauthz_list_file_finalize(Object *obj)
> +{
> +    QAuthZListFile *authz = QAUTHZ_LIST_FILE(obj);
> +
> +    if (authz->file_watch != -1 && authz->file_monitor) {
> +        gchar *dir = g_path_get_dirname(authz->filename);
> +        qemu_file_monitor_remove_watch(authz->file_monitor,
> +                                       dir,
> +                                       authz->file_watch);
> +        g_free(dir);
> +    }
> +    object_unref(OBJECT(authz->list));
> +    g_free(authz->filename);
> +}
> +
> +
> +static void
> +qauthz_list_file_class_init(ObjectClass *oc, void *data)
> +{
> +    UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
> +    QAuthZClass *authz = QAUTHZ_CLASS(oc);
> +
> +    ucc->complete = qauthz_list_file_complete;
> +
> +    object_class_property_add_str(oc, "filename",
> +                                  qauthz_list_file_prop_get_filename,
> +                                  qauthz_list_file_prop_set_filename,
> +                                  NULL);
> +    object_class_property_add_bool(oc, "refresh",
> +                                   qauthz_list_file_prop_get_refresh,
> +                                   qauthz_list_file_prop_set_refresh,
> +                                   NULL);
> +
> +    authz->is_allowed = qauthz_list_file_is_allowed;
> +}
> +
> +
> +static void
> +qauthz_list_file_init(Object *obj)
> +{
> +    QAuthZListFile *authz = QAUTHZ_LIST_FILE(obj);
> +
> +    authz->file_watch = -1;
> +#ifdef CONFIG_INOTIFY1
> +    authz->refresh = TRUE;
> +#endif
> +}
> +
> +
> +QAuthZListFile *qauthz_list_file_new(const char *id,
> +                                     const char *filename,
> +                                     Error **errp)
> +{
> +    return QAUTHZ_LIST_FILE(
> +        object_new_with_props(TYPE_QAUTHZ_LIST_FILE,
> +                              object_get_objects_root(),
> +                              id, errp,
> +                              "filename", filename,
> +                              NULL));
> +}
> +
> +
> +static const TypeInfo qauthz_list_file_info = {
> +    .parent = TYPE_QAUTHZ_LIST,
> +    .name = TYPE_QAUTHZ_LIST_FILE,
> +    .instance_init = qauthz_list_file_init,
> +    .instance_size = sizeof(QAuthZListFile),
> +    .instance_finalize = qauthz_list_file_finalize,
> +    .class_size = sizeof(QAuthZListFileClass),
> +    .class_init = qauthz_list_file_class_init,
> +    .interfaces = (InterfaceInfo[]) {
> +        { TYPE_USER_CREATABLE },
> +        { }
> +    }
> +};
> +
> +
> +static void
> +qauthz_list_file_register_types(void)
> +{
> +    type_register_static(&qauthz_list_file_info);
> +}
> +
> +
> +type_init(qauthz_list_file_register_types);
> diff --git a/authz/trace-events b/authz/trace-events
> index a896d876e8..fb65349a90 100644
> --- a/authz/trace-events
> +++ b/authz/trace-events
> @@ -9,3 +9,7 @@ qauthz_simple_is_allowed(void *authz, const char *wantidentity, const char *goti
>  # auth/list.c
>  qauthz_list_check_rule(void *authz, const char *identity, const char *rule, int format, int policy) "AuthZ list %p check rule=%s identity=%s format=%d policy=%d"
>  qauthz_list_default_policy(void *authz, const char *identity, int policy) "AuthZ list %p default identity=%s policy=%d"
> +
> +# auth/listfile.c
> +qauthz_list_file_load(void *authz, const char *filename) "AuthZ file %p load filename=%s"
> +qauthz_list_file_refresh(void *authz, const char *filename, int success) "AuthZ file %p load filename=%s success=%d"
> diff --git a/include/authz/listfile.h b/include/authz/listfile.h
> new file mode 100644
> index 0000000000..244aadc064
> --- /dev/null
> +++ b/include/authz/listfile.h
> @@ -0,0 +1,110 @@
> +/*
> + * QEMU list file authorization driver
> + *
> + * Copyright (c) 2018 Red Hat, Inc.
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, see <http://www.gnu.org/licenses/>.
> + *
> + */
> +
> +#ifndef QAUTHZ_LIST_FILE_H__
> +#define QAUTHZ_LIST_FILE_H__
> +
> +#include "authz/list.h"
> +#include "qapi/qapi-types-authz.h"
> +#include "qemu/filemonitor.h"
> +
> +#define TYPE_QAUTHZ_LIST_FILE "authz-list-file"
> +
> +#define QAUTHZ_LIST_FILE_CLASS(klass)                        \
> +    OBJECT_CLASS_CHECK(QAuthZListFileClass, (klass),        \
> +                       TYPE_QAUTHZ_LIST_FILE)
> +#define QAUTHZ_LIST_FILE_GET_CLASS(obj)              \
> +    OBJECT_GET_CLASS(QAuthZListFileClass, (obj),    \
> +                      TYPE_QAUTHZ_LIST_FILE)
> +#define QAUTHZ_LIST_FILE(obj) \
> +    INTERFACE_CHECK(QAuthZListFile, (obj),          \
> +                    TYPE_QAUTHZ_LIST_FILE)
> +
> +typedef struct QAuthZListFile QAuthZListFile;
> +typedef struct QAuthZListFileClass QAuthZListFileClass;
> +
> +
> +/**
> + * QAuthZListFile:
> + *
> + * This authorization driver provides a file mechanism
> + * for granting access by matching user names against a
> + * file of globs. Each match rule has an associated policy
> + * and a catch all policy applies if no rule matches
> + *
> + * To create an instance of this class via QMP:
> + *
> + *  {
> + *    "execute": "object-add",
> + *    "arguments": {
> + *      "qom-type": "authz-list-file",
> + *      "id": "authz0",
> + *      "parameters": {
> + *        "filename": "/etc/qemu/myvm-vnc.acl",
> + *        "refresh": "yes"
> + *      }
> + *    }
> + *  }
> + *
> + * If 'refresh' is 'yes', inotify is used to monitor for changes
> + * to the file and auto-reload the rules.
> + *
> + * The myvm-vnc.acl file should contain the parameters for
> + * the QAuthZList object in JSON format:
> + *
> + *      {
> + *        "rules": [
> + *           { "match": "fred", "policy": "allow", "format": "exact" },
> + *           { "match": "bob", "policy": "allow", "format": "exact" },
> + *           { "match": "danb", "policy": "deny", "format": "exact" },
> + *           { "match": "dan*", "policy": "allow", "format": "glob" }
> + *        ],
> + *        "policy": "deny"
> + *      }
> + *
> + * The object can be created on the command line using
> + *
> + *   -object authz-list-file,id=authz0,\
> + *           filename=/etc/qemu/myvm-vnc.acl,refresh=yes
> + *
> + */
> +struct QAuthZListFile {
> +    QAuthZ parent_obj;
> +
> +    QAuthZ *list;
> +    char *filename;
> +    bool refresh;
> +    QFileMonitor *file_monitor;
> +    int file_watch;
> +};
> +
> +
> +struct QAuthZListFileClass {
> +    QAuthZClass parent_class;
> +};
> +
> +
> +QAuthZListFile *qauthz_list_file_new(const char *id,
> +                                     const char *filename,
> +                                     Error **errp);
> +
> +
> +#endif /* QAUTHZ_LIST_FILE_H__ */
> +
> diff --git a/qemu-options.hx b/qemu-options.hx
> index ef38ff19e2..fcf7d627fc 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -4398,6 +4398,53 @@ would look like:
>       ...
>  @end example
>  
> +
> +@item -object authz-listfile,id=@var{id},filename=@var{path},refresh=@var{yes|no}
> +
> +Create an authorization object that will control access to network services.
> +
> +The @option{filename} parameter is the fully qualified path to a file
> +containing the access control list rules in JSON format.
> +
> +An example set of rules that match against SASL usernames might look
> +like:
> +
> +@example
> +  @{
> +    "rules": [
> +       @{ "match": "fred", "policy": "allow", "format": "exact" @},
> +       @{ "match": "bob", "policy": "allow", "format": "exact" @},
> +       @{ "match": "danb", "policy": "deny", "format": "glob" @},
> +       @{ "match": "dan*", "policy": "allow", "format": "exact" @},
> +    ],
> +    "policy": "deny"
> +  @}
> +@end example
> +
> +When checking access the object will iterate over all the rules and
> +the first rule to match will have its @option{policy} value returned
> +as the result. If no rules match, then the default @option{policy}
> +value is returned.
> +
> +The rules can either be an exact string match, or they can use the
> +simple UNIX glob pattern matching to allow wildcards to be used.
> +
> +If @option{refresh} is set to true the file will be monitored
> +and automatically reloaded whenever its content changes.
> +
> +As with the @code{authz-simple} object, the format of the identity
> +strings being matched depends on the network service, but is usually
> +a TLS x509 distinguished name, or a SASL username.
> +
> +An example authorization object to validate a SASL username
> +would look like:
> +@example
> + # $QEMU \
> +     ...
> +     -object authz-simple,id=auth0,filename=/etc/qemu/vnc-sasl.acl,refresh=yes
> +     ...
> +@end example
> +
>  @end table
>  
>  ETEXI
> 

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

On Fri, Oct 19, 2018 at 11:41:45AM +0200, Philippe Mathieu-Daudé wrote:
> On 09/10/2018 15:04, Daniel P. Berrangé wrote:
> > Add a QAuthZListFile object type that implements the QAuthZ interface. This
> > built-in implementation is a proxy around the QAtuhZList object type,
> > initializing it from an external file, and optionally, automatically
> > reloading it whenever it changes.
> > 
> > To create an instance of this object via the QMP monitor, the syntax
> > used would be:
> > 
> >       {
> >         "execute": "object-add",
> >         "arguments": {
> >           "qom-type": "authz-list-file",
> >           "id": "authz0",
> >           "parameters": {
> >             "filename": "/etc/qemu/vnc.acl",
> > 	    "refresh": "yes"
> >           }
> >         }
> >       }
> > 
> > If "refresh" is "yes", inotify is used to monitor the file,
> > automatically reloading changes. If an error occurs during reloading,
> > all authorizations will fail until the file is next successfully
> > loaded.
> > 
> > The /etc/qemu/vnc.acl file would contain a JSON representation of a
> > QAuthZList object
> > 
> >     {
> >       "rules": [
> >          { "match": "fred", "policy": "allow", "format": "exact" },
> >          { "match": "bob", "policy": "allow", "format": "exact" },
> >          { "match": "danb", "policy": "deny", "format": "glob" },
> >          { "match": "dan*", "policy": "allow", "format": "exact" },
> >       ],
> >       "policy": "deny"
> >     }
> > 
> > This sets up an authorization rule that allows 'fred', 'bob' and anyone
> > whose name starts with 'dan', except for 'danb'. Everyone unmatched is
> > denied.
> > 
> > The object can be loaded on the comand line using
> > 
> >    -object authz-list-file,id=authz0,filename=/etc/qemu/vnc.acl,refresh=yes
> > 
> > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> > ---
> >  authz/Makefile.objs      |   1 +
> >  authz/listfile.c         | 284 +++++++++++++++++++++++++++++++++++++++
> >  authz/trace-events       |   4 +
> >  include/authz/listfile.h | 110 +++++++++++++++
> >  qemu-options.hx          |  47 +++++++
> >  5 files changed, 446 insertions(+)
> >  create mode 100644 authz/listfile.c
> >  create mode 100644 include/authz/listfile.h
> > 

> > +static void
> > +qauthz_list_file_event(int wd G_GNUC_UNUSED,
> > +                       QFileMonitorEvent ev G_GNUC_UNUSED,
> > +                       const char *name G_GNUC_UNUSED,
> > +                       void *opaque)
> > +{
> > +    QAuthZListFile *fauthz = opaque;
> > +    Error *err = NULL;
> > +
> > +    if (ev != QFILE_MONITOR_EVENT_MODIFIED &&
> > +        ev != QFILE_MONITOR_EVENT_CREATED)
> 
> You missed:
> 
>                                               {
> 
> > +        return;
> 
>        }

Opps, yes.


> > +static void
> > +qauthz_list_file_complete(UserCreatable *uc, Error **errp)
> > +{
> > +    QAuthZListFile *fauthz = QAUTHZ_LIST_FILE(uc);
> > +
> > +    fauthz->list = qauthz_list_file_load(fauthz, errp);
> > +
> > +    if (fauthz->refresh) {
> 
> Can we invert this condition?

Yes, will do

> 
> > +        gchar *dir, *file;
> > +        fauthz->file_monitor = qemu_file_monitor_get_instance(errp);
> > +        if (!fauthz->file_monitor) {
> > +            return;
> > +        }
> > +
> > +        dir = g_path_get_dirname(fauthz->filename);
> > +        if (g_str_equal(dir, ".")) {
> > +            error_setg(errp, "Filename must be an absolute path");
> 
> What about:
> 
>                goto cleanup;

Yep.

> 
> > +            g_free(dir);
> > +            return;
> > +        }
> > +        file = g_path_get_basename(fauthz->filename);
> > +        if (g_str_equal(file, ".")) {
> > +            error_setg(errp, "Path has no trailing filename component");
> 
>                goto cleanup;
> 
> > +            g_free(file);
> > +            g_free(dir);
> > +            return;
> > +        }
> > +
> > +        fauthz->file_watch = qemu_file_monitor_add_watch(
> > +            fauthz->file_monitor, dir, file,
> > +            qauthz_list_file_event, fauthz, errp);
> > +        g_free(file);
> > +        g_free(dir);
> > +        if (fauthz->file_watch < 0) {
> 
> Is this really useful? Do you plan to add more code here?

I just want to make it clear to anyone who changes the code
in future that there's an expected failure condition here.

> > +            return;
> > +        }
> > +    }
> > +}

Regards,
Daniel

On 19/10/2018 14:53, Daniel P. Berrangé wrote:
> On Fri, Oct 19, 2018 at 11:41:45AM +0200, Philippe Mathieu-Daudé wrote:
>> On 09/10/2018 15:04, Daniel P. Berrangé wrote:
>>> Add a QAuthZListFile object type that implements the QAuthZ interface. This
>>> built-in implementation is a proxy around the QAtuhZList object type,
>>> initializing it from an external file, and optionally, automatically
>>> reloading it whenever it changes.
>>>
>>> To create an instance of this object via the QMP monitor, the syntax
>>> used would be:
>>>
>>>       {
>>>         "execute": "object-add",
>>>         "arguments": {
>>>           "qom-type": "authz-list-file",
>>>           "id": "authz0",
>>>           "parameters": {
>>>             "filename": "/etc/qemu/vnc.acl",
>>> 	    "refresh": "yes"
>>>           }
>>>         }
>>>       }
>>>
>>> If "refresh" is "yes", inotify is used to monitor the file,
>>> automatically reloading changes. If an error occurs during reloading,
>>> all authorizations will fail until the file is next successfully
>>> loaded.
>>>
>>> The /etc/qemu/vnc.acl file would contain a JSON representation of a
>>> QAuthZList object
>>>
>>>     {
>>>       "rules": [
>>>          { "match": "fred", "policy": "allow", "format": "exact" },
>>>          { "match": "bob", "policy": "allow", "format": "exact" },
>>>          { "match": "danb", "policy": "deny", "format": "glob" },
>>>          { "match": "dan*", "policy": "allow", "format": "exact" },
>>>       ],
>>>       "policy": "deny"
>>>     }
>>>
>>> This sets up an authorization rule that allows 'fred', 'bob' and anyone
>>> whose name starts with 'dan', except for 'danb'. Everyone unmatched is
>>> denied.
>>>
>>> The object can be loaded on the comand line using
>>>
>>>    -object authz-list-file,id=authz0,filename=/etc/qemu/vnc.acl,refresh=yes
>>>
>>> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
>>> ---
>>>  authz/Makefile.objs      |   1 +
>>>  authz/listfile.c         | 284 +++++++++++++++++++++++++++++++++++++++
>>>  authz/trace-events       |   4 +
>>>  include/authz/listfile.h | 110 +++++++++++++++
>>>  qemu-options.hx          |  47 +++++++
>>>  5 files changed, 446 insertions(+)
>>>  create mode 100644 authz/listfile.c
>>>  create mode 100644 include/authz/listfile.h
>>>
> 
>>> +static void
>>> +qauthz_list_file_event(int wd G_GNUC_UNUSED,
>>> +                       QFileMonitorEvent ev G_GNUC_UNUSED,
>>> +                       const char *name G_GNUC_UNUSED,
>>> +                       void *opaque)
>>> +{
>>> +    QAuthZListFile *fauthz = opaque;
>>> +    Error *err = NULL;
>>> +
>>> +    if (ev != QFILE_MONITOR_EVENT_MODIFIED &&
>>> +        ev != QFILE_MONITOR_EVENT_CREATED)
>>
>> You missed:
>>
>>                                               {
>>
>>> +        return;
>>
>>        }
> 
> Opps, yes.
> 
> 
>>> +static void
>>> +qauthz_list_file_complete(UserCreatable *uc, Error **errp)
>>> +{
>>> +    QAuthZListFile *fauthz = QAUTHZ_LIST_FILE(uc);
>>> +
>>> +    fauthz->list = qauthz_list_file_load(fauthz, errp);
>>> +
>>> +    if (fauthz->refresh) {
>>
>> Can we invert this condition?
> 
> Yes, will do
> 
>>
>>> +        gchar *dir, *file;
>>> +        fauthz->file_monitor = qemu_file_monitor_get_instance(errp);
>>> +        if (!fauthz->file_monitor) {
>>> +            return;
>>> +        }
>>> +
>>> +        dir = g_path_get_dirname(fauthz->filename);
>>> +        if (g_str_equal(dir, ".")) {
>>> +            error_setg(errp, "Filename must be an absolute path");
>>
>> What about:
>>
>>                goto cleanup;
> 
> Yep.
> 
>>
>>> +            g_free(dir);
>>> +            return;
>>> +        }
>>> +        file = g_path_get_basename(fauthz->filename);
>>> +        if (g_str_equal(file, ".")) {
>>> +            error_setg(errp, "Path has no trailing filename component");
>>
>>                goto cleanup;
>>
>>> +            g_free(file);
>>> +            g_free(dir);
>>> +            return;
>>> +        }
>>> +
>>> +        fauthz->file_watch = qemu_file_monitor_add_watch(
>>> +            fauthz->file_monitor, dir, file,
>>> +            qauthz_list_file_event, fauthz, errp);
>>> +        g_free(file);
>>> +        g_free(dir);
>>> +        if (fauthz->file_watch < 0) {
>>
>> Is this really useful? Do you plan to add more code here?
> 
> I just want to make it clear to anyone who changes the code
> in future that there's an expected failure condition here.

I thought so. Just add a simple /* comment */ about it :)

> 
>>> +            return;
>>> +        }
>>> +    }
>>> +}
> 
> Regards,
> Daniel
>