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Date: Wed, 27 Jul 2022 11:06:19 +0200
From: Fabian =?iso-8859-1?q?Gr=FCnbichler?= <f.gruenbichler@proxmox.com>
To: Oguz Bektas <o.bektas@proxmox.com>, pve-devel@lists.proxmox.com
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Subject: Re: [pve-devel] [PATCH v4 access-control 05/18] api: allow
superusers to edit tfa and password settings
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On June 2, 2022 9:24 am, Oguz Bektas wrote:
> - prevent non-SU to change SU passwords
> - warning messages on raise_perm_exc()
> - log who did the password change
> - has_superuser_anywhere helper
>=20
> Suggested-by: Fabian Gr=C3=BCnbichler <f.gruenbichler@proxmox.com>
> Signed-off-by: Oguz Bektas <o.bektas@proxmox.com>
> ---
> src/PVE/API2/AccessControl.pm | 24 ++++++++++++++----------
> src/PVE/API2/TFA.pm | 16 +++++++++++++++-
> src/PVE/RPCEnvironment.pm | 15 +++++++++++++++
> 3 files changed, 44 insertions(+), 11 deletions(-)
>=20
> diff --git a/src/PVE/API2/AccessControl.pm b/src/PVE/API2/AccessControl.p=
m
> index 5d78c6f..2a584ab 100644
> --- a/src/PVE/API2/AccessControl.pm
> +++ b/src/PVE/API2/AccessControl.pm
> @@ -378,23 +378,27 @@ __PACKAGE__->register_method ({
> =20
> $rpcenv->check_user_exist($userid);
> =20
> + my $is_superuser =3D $rpcenv->check($authuser, "/access", ['SuperUser']=
, 1);
> +
> if ($authuser eq 'root@pam') {
> # OK - root can change anything
> - } else {
> - if ($authuser eq $userid) {
> - $rpcenv->check_user_enabled($userid);
> - # OK - each user can change its own password
> - } else {
> - # only root may change root password
> - raise_perm_exc() if $userid eq 'root@pam';
> - # do not allow to change system user passwords
> - raise_perm_exc() if $realm eq 'pam';
> + } elsif ($authuser eq $userid) {
> + $rpcenv->check_user_enabled($userid);
> + # OK - each user can change its own password
> + } else { # changing someone else's password
> + raise_perm_exc("only root\@pam may change their password!\n") if $u=
serid eq 'root@pam';
> + raise_perm_exc("changing system user passwords is not allowed!\n") =
if $realm eq 'pam';
> +
> + if (!$is_superuser) {
> + # check if the target user has SU privileges
> + raise_perm_exc("only superusers can change another superuser's passwor=
d!\n")
> + if $rpcenv->has_superuser_anywhere($userid);
> }
> }
> =20
> PVE::AccessControl::domain_set_password($realm, $ruid, $param->{passwor=
d});
> =20
> - PVE::Cluster::log_msg('info', 'root@pam', "changed password for user '$=
userid'");
> + PVE::Cluster::log_msg('info', "$authuser", "changed password for user '=
$userid'");
> =20
> return undef;
> }});
> diff --git a/src/PVE/API2/TFA.pm b/src/PVE/API2/TFA.pm
> index bee4dee..c1cdd5e 100644
> --- a/src/PVE/API2/TFA.pm
> +++ b/src/PVE/API2/TFA.pm
> @@ -96,22 +96,36 @@ my $TFA_UPDATE_INFO_SCHEMA =3D {
> };
> =20
> # Only root may modify root, regular users need to specify their passwor=
d.
> +# Only users with SU on /access may modify other users with SU anywhere
> #
> # Returns the userid returned from `verify_username`.
> # Or ($userid, $realm) in list context.
> my sub root_permission_check : prototype($$$$) {
> my ($rpcenv, $authuser, $userid, $password) =3D @_;
> =20
> + # authuser =3D the user making the change
> + # userid =3D the user to be changed
> +
> + if ($userid eq 'root@pam') {
> + raise_perm_exc("only root\@pam may edit themselves!\n")
> + if $authuser ne 'root@pam';
> + }
if ($foo && $bar) {
baz();
}
or
baz() if $foo && $bar;
also, the escaping can be avoided if you just quote with '' instead of=20
"" in the message.
> +
> ($userid, undef, my $realm) =3D PVE::AccessControl::verify_username(=
$userid);
> $rpcenv->check_user_exist($userid);
> =20
> - raise_perm_exc() if $userid eq 'root@pam' && $authuser ne 'root@pam'=
;
> + my $is_superuser =3D $rpcenv->check($authuser, "/access", ['SuperUse=
r'], 1);
only used once, inside the next if, please move it there (I told you=20
this already?)
> =20
> # Regular users need to confirm their password to change TFA setting=
s.
> if ($authuser ne 'root@pam') {
> raise_param_exc({ 'password' =3D> 'password is required to modify TFA d=
ata' })
> if !defined($password);
> =20
> + if (!$is_superuser && $authuser ne $userid) {
> + raise_perm_exc("only superusers can change another superuser's TFA =
settings!\n")
> + if $rpcenv->has_superuser_anywhere($userid);
could actually be ordered by order of expensiveness here, but it's not=20
too important..
if ($authuser ne $userid) {
my $is_superuser =3D ...;
raise_perm_exc..
if !is_superuser && $rpcenv->has_superuser_anywhere(..);
}
or
raise_perm_exc
if user_mismatch_check
&& isnt_superuser_check
&& has_superuser_check;
that way each check is only actually done if needed, after the previous=20
check made us go down further. the current way is just hard to parse=20
with no benefit at all.
> + }
> +
> ($authuser, my $auth_username, my $auth_realm) =3D
> PVE::AccessControl::verify_username($authuser);
the whole code here is rather similar to the check in change_password,=20
have you thought about unifying them?
> =20
> diff --git a/src/PVE/RPCEnvironment.pm b/src/PVE/RPCEnvironment.pm
> index 4c55b25..5bcb4ba 100644
> --- a/src/PVE/RPCEnvironment.pm
> +++ b/src/PVE/RPCEnvironment.pm
> @@ -479,6 +479,21 @@ sub check_api2_permissions {
> raise_perm_exc();
> }
> =20
> +sub has_superuser_anywhere {
> + my ($self, $username) =3D @_;
> +
> + return 1 if $username eq 'root@pam';
> +
> + # get all ACL paths from config and check for SU privilege
> + my $acls =3D $self->{user_cfg}->{acl};
> + my @acl_paths =3D keys(%$acls);
> + @acl_paths =3D ['/'] if !@acl_paths;
> + foreach my $path (@acl_paths) {
> + return 1 if $self->check($username, $path, ['SuperUser'], 1);
> + }
> + return 0;
> +}
this is basically a reduced $rpcenv->get_effective_permissions with=20
early abort. some possible options:
- extend it (add a '$needle' parameter, early return 1 if any path=20
matches that check)
- just use it (and drop the early abort)
- factor out the "get all ACL paths" part for re-using
else we risk missing this helper here if we ever add another layer of=20
indirection for ACL path resolution, like we currently have for pools..
> +
> sub log_cluster_msg {
> my ($self, $pri, $user, $msg) =3D @_;
> =20
> --=20
> 2.30.2
>=20
>=20