[pve-devel] [PATCH access-control v3 3/4] ldap: add opt-in `check-connection` param to perform a bind check

[Christoph Heiss <c.heiss@proxmox.com>]

Removes the dreaded DN regex, instead introducing a optional
connect/bind check on creation/update, aligning it with the way PBS does
it.

Additionally, it has the benefit that instead of letting a sync fail on
the first try due to e.g. bad bind credentials, it gives the user some
direct feedback when trying to add/update a LDAP realm, if enabled.

Should be rather a corner case, but it's the easiest way for us to
accomodate and the most versatile for users needing this.

This is part of the result of a previous discussion [0], and the same
approach is already implemented for PBS [1].

[0] https://lists.proxmox.com/pipermail/pve-devel/2023-May/056839.html
[1] https://lists.proxmox.com/pipermail/pbs-devel/2023-June/006237.html

Signed-off-by: Christoph Heiss <c.heiss@proxmox.com>
---
N.B.: Needs a version bump of libpve-common-perl for the base properties
parameter on {create,update}Schema().

Changes v2 -> v3:
  * Move 'check-connection' out of schema definition to extra param
    Pointed out by Wolfgang, it should not be part of the (stored)
    config schema if never stored. [2]

Changes v1 -> v2:
  * Do not store the 'check-connection' parameter in the realm config

The decision to put this behind an optional (off-by-default) parameter
was made during an off-list discussion with Lukas. The summary of that
can be found as a follow-up on the previous series [3] [4].

Note that the `base_dn`/`group_dn` now goes completely unvalided - but
again, that is how it works in PBS.

[2] https://lists.proxmox.com/pipermail/pve-devel/2023-August/058724.html
[3] https://lists.proxmox.com/pipermail/pve-devel/2023-July/058540.html
[4] https://lists.proxmox.com/pipermail/pve-devel/2023-August/058582.html

 src/PVE/API2/Domains.pm | 36 +++++++++++++++++++++++++++++++++---
 src/PVE/Auth/LDAP.pm    | 18 +++++++++---------
 src/PVE/Auth/Plugin.pm  |  8 ++++++++
 3 files changed, 50 insertions(+), 12 deletions(-)

diff --git a/src/PVE/API2/Domains.pm b/src/PVE/API2/Domains.pm
index 9332aa7..e7b7d39 100644
--- a/src/PVE/API2/Domains.pm
+++ b/src/PVE/API2/Domains.pm
@@ -117,7 +117,14 @@ __PACKAGE__->register_method ({
 	check => ['perm', '/access/realm', ['Realm.Allocate']],
     },
     description => "Add an authentication server.",
-    parameters => PVE::Auth::Plugin->createSchema(),
+    parameters => PVE::Auth::Plugin->createSchema(0, {
+	'check-connection' => {
+	    description => 'Check bind connection to the server.',
+	    type => 'boolean',
+	    optional => 1,
+	    default => 0,
+	},
+    }),
     returns => { type => 'null' },
     code => sub {
 	my ($param) = @_;
@@ -133,6 +140,7 @@ __PACKAGE__->register_method ({

 		my $realm = extract_param($param, 'realm');
 		my $type = $param->{type};
+		my $check_connection = extract_param($param, 'check-connection');

 		die "domain '$realm' already exists\n"
 		    if $ids->{$realm};
@@ -143,6 +151,9 @@ __PACKAGE__->register_method ({
 		die "unable to create builtin type '$type'\n"
 		    if ($type eq 'pam' || $type eq 'pve');

+		die "'check-connection' parameter can only be set for realms of type 'ldap' or 'ad'\n"
+		    if defined($check_connection) && !($type eq 'ldap' || $type eq 'ad');
+
 		if ($type eq 'ad' || $type eq 'ldap') {
 		    $map_sync_default_options->($param, 1);
 		}
@@ -165,6 +176,10 @@ __PACKAGE__->register_method ({
 		}
 		$plugin->on_add_hook($realm, $config, password => $password);

+		# Only for LDAP/AD, implied through the existence of the 'check-connection' param
+		$plugin->check_connection($realm, $config, password => $password)
+		    if $check_connection;
+
 		cfs_write_file($domainconfigfile, $cfg);
 	    }, "add auth server failed");

@@ -180,7 +195,14 @@ __PACKAGE__->register_method ({
     },
     description => "Update authentication server settings.",
     protected => 1,
-    parameters => PVE::Auth::Plugin->updateSchema(),
+    parameters => PVE::Auth::Plugin->updateSchema(0, {
+	'check-connection' => {
+	    description => 'Check bind connection to the server.',
+	    type => 'boolean',
+	    optional => 1,
+	    default => 0,
+	},
+    }),
     returns => { type => 'null' },
     code => sub {
 	my ($param) = @_;
@@ -198,10 +220,15 @@ __PACKAGE__->register_method ({
 		PVE::SectionConfig::assert_if_modified($cfg, $digest);

 		my $realm = extract_param($param, 'realm');
+		my $type = $ids->{$realm}->{type};
+		my $check_connection = extract_param($param, 'check-connection');

 		die "domain '$realm' does not exist\n"
 		    if !$ids->{$realm};

+		die "'check-connection' parameter can only be set for realms of type 'ldap' or 'ad'\n"
+		    if defined($check_connection) && !($type eq 'ldap' || $type eq 'ad');
+
 		my $delete_str = extract_param($param, 'delete');
 		die "no options specified\n"
 		    if !$delete_str && !scalar(keys %$param) && !defined($password);
@@ -212,7 +239,6 @@ __PACKAGE__->register_method ({
 		    $delete_pw = 1 if $opt eq 'password';
 		}

-		my $type = $ids->{$realm}->{type};
 		if ($type eq 'ad' || $type eq 'ldap') {
 		    $map_sync_default_options->($param, 1);
 		}
@@ -237,6 +263,10 @@ __PACKAGE__->register_method ({
 		    $plugin->on_update_hook($realm, $config);
 		}

+		# Only for LDAP/AD, implied through the existence of the 'check-connection' param
+		$plugin->check_connection($realm, $ids->{$realm}, password => $password)
+		    if $check_connection;
+
 		cfs_write_file($domainconfigfile, $cfg);
 	    }, "update auth server failed");

diff --git a/src/PVE/Auth/LDAP.pm b/src/PVE/Auth/LDAP.pm
index fc82a17..b958f2b 100755
--- a/src/PVE/Auth/LDAP.pm
+++ b/src/PVE/Auth/LDAP.pm
@@ -10,9 +10,6 @@ use PVE::Tools;

 use base qw(PVE::Auth::Plugin);

-my  $dn_part_regex = qr!("[^"]+"|[^ ,+"/<>;=#][^,+"/<>;=]*[^ ,+"/<>;=]|[^ ,+"/<>;=#])!;
-our $dn_regex = qr!\w+=${dn_part_regex}(,\s*\w+=${dn_part_regex})*!;
-
 sub type {
     return 'ldap';
 }
@@ -22,7 +19,6 @@ sub properties {
 	base_dn => {
 	    description => "LDAP base domain name",
 	    type => 'string',
-	    pattern => $dn_regex,
 	    optional => 1,
 	    maxLength => 256,
 	},
@@ -36,7 +32,6 @@ sub properties {
 	bind_dn => {
 	    description => "LDAP bind domain name",
 	    type => 'string',
-	    pattern => $dn_regex,
 	    optional => 1,
 	    maxLength => 256,
 	},
@@ -94,7 +89,6 @@ sub properties {
 	    description => "LDAP base domain name for group sync. If not set, the"
 		." base_dn will be used.",
 	    type => 'string',
-	    pattern => $dn_regex,
 	    optional => 1,
 	    maxLength => 256,
 	},
@@ -137,7 +131,7 @@ sub properties {
 	    type => 'boolean',
 	    optional => 1,
 	    default => 1,
-	}
+	},
     };
 }

@@ -184,7 +178,7 @@ sub get_scheme_and_port {
 }

 sub connect_and_bind {
-    my ($class, $config, $realm) = @_;
+    my ($class, $config, $realm, $param) = @_;

     my $servers = [$config->{server1}];
     push @$servers, $config->{server2} if $config->{server2};
@@ -215,7 +209,7 @@ sub connect_and_bind {

     if ($config->{bind_dn}) {
 	my $bind_dn = $config->{bind_dn};
-	my $bind_pass = ldap_get_credentials($realm);
+	my $bind_pass = $param->{password} || ldap_get_credentials($realm);
 	die "missing password for realm $realm\n" if !defined($bind_pass);
 	PVE::LDAP::ldap_bind($ldap, $bind_dn, $bind_pass);
     } elsif ($config->{cert} && $config->{certkey}) {
@@ -454,4 +448,10 @@ sub on_delete_hook {
     ldap_delete_credentials($realm);
 }

+sub check_connection {
+    my ($class, $realm, $config, %param) = @_;
+
+    $class->connect_and_bind($config, $realm, \%param);
+}
+
 1;
diff --git a/src/PVE/Auth/Plugin.pm b/src/PVE/Auth/Plugin.pm
index 2f64a13..429bc88 100755
--- a/src/PVE/Auth/Plugin.pm
+++ b/src/PVE/Auth/Plugin.pm
@@ -317,4 +317,12 @@ sub on_delete_hook {
     # do nothing by default
 }

+# called during addition and updates of realms (before the new domain config gets written)
+# die to abort addition/update in case the connection/bind fails
+# NOTE: runs in a storage config *locked* context
+sub check_connection {
+    my ($class, $realm, $config, %param) = @_;
+    # do nothing by default
+}
+
 1;
--
2.41.0