[pve-devel] [PATCH access-control 1/2] api: domains: add off-by-default `check-connection` parameter

[Christoph Heiss]

Removes the dreaded DN regex, instead introducing a connect/bind check
on creation/update, aligning it with the way PBS does it. This is
enabled by default for new realms, but opt-in for existing, to not break
backwards-compatibility.

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://git.proxmox.com/?p=proxmox-backup.git;a=commitdiff;h=5210f3b5

Signed-off-by: Christoph Heiss <c.heiss at proxmox.com>
---
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 [2].

Note that the `base_dn`/`group_dn` now goes completely unvalided - but
again, that is how it works in PBS. We could use canonical_dn() for this
(as implemented in the previous series [3]), depending on whether we
want this kind of "divergence" between PVE & PBS. I'm happy to re-add
that should be the way forward.

[2] https://lists.proxmox.com/pipermail/pve-devel/2023-July/058540.html
[3] https://lists.proxmox.com/pipermail/pve-devel/2023-July/058392.html

 src/PVE/API2/Domains.pm |  8 ++++++++
 src/PVE/Auth/LDAP.pm    | 26 +++++++++++++++++---------
 src/PVE/Auth/Plugin.pm  |  8 ++++++++
 3 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/src/PVE/API2/Domains.pm b/src/PVE/API2/Domains.pm
index 9332aa7..e921208 100644
--- a/src/PVE/API2/Domains.pm
+++ b/src/PVE/API2/Domains.pm
@@ -165,6 +165,10 @@ __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 => $password)
+		    if defined($param->{'check-connection'}) && $param->{'check-connection'};
+
 		cfs_write_file($domainconfigfile, $cfg);
 	    }, "add auth server failed");

@@ -237,6 +241,10 @@ __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, $config, password => $password)
+		    if defined($param->{'check-connection'}) && $param->{'check-connection'};
+
 		cfs_write_file($domainconfigfile, $cfg);
 	    }, "update auth server failed");

diff --git a/src/PVE/Auth/LDAP.pm b/src/PVE/Auth/LDAP.pm
index fc82a17..c4c4cda 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 +131,14 @@ sub properties {
 	    type => 'boolean',
 	    optional => 1,
 	    default => 1,
-	}
+	},
+	'check-connection' => {
+	    description => 'Check bind connection to LDAP server.',
+	    type => 'boolean',
+	    optional => 1,
+	    # TODO: Make it enabled-by-default with PVE 9.0?
+	    default => 0,
+	},
     };
 }

@@ -169,6 +170,7 @@ sub options {
 	'sync-defaults-options' => { optional => 1 },
 	mode => { optional => 1 },
 	'case-sensitive' => { optional => 1 },
+	'check-connection' => { optional => 1 },
     };
 }

@@ -184,7 +186,7 @@ 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 +217,7 @@ 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} && $config->{certkey}) {
@@ -454,4 +456,10 @@ sub on_delete_hook {
     ldap_delete_credentials($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