Add support for SASL bind

We introduce a ldap_sasl() method in Ldap and LdapMulti with
an optionnal array of SASL options. A module that subclasses
Ldap or Ldapmulti can use it instead of simple login().

This requires SASL bind support in Symfony, which has been
merged in the 7.3 branch. SimpleSAMLphp uses Symfony 7.2.
How should this ne handled? I can backport the patches
for Symfony 7.2, but do we have a way to fold them in
the simpleSAMLphp package?

src/Auth/Source/Ldap.php

@@ -67,13 +67,14 @@ public function __construct(array $info, array $config)
 
 
     /**
-     * Attempt to log in using the given username and password.
+     * Attempt to log in using SASL and the given username and password.
      *
      * @param string $username  The username the user wrote.
      * @param string $password  The password the user wrote.
+     * @param array|null $sasl_args  SASL options
      * @return array  Associative array with the users attributes.
      */
-    protected function login(string $username, #[\SensitiveParameter]string $password): array
+    protected function login_sasl(string $username, #[\SensitiveParameter]string $password, ?array $sasl_args): array
     {
         if (preg_match('/^\s*$/', $password)) {
             // The empty string is considered an anonymous bind to Symfony
@@ -128,7 +129,14 @@ protected function login(string $username, #[\SensitiveParameter]string $passwor
         }
 
         /* Verify the credentials */
-        $this->connector->bind($dn, $password);
+        if (isset($sasl_args)) {
+            Assert::isArray($sasl_args);
+
+            $this->connector->saslBind($dn, $password, $sasl_args['mech'], $sasl_args['realm'], $sasl_args['authc_id'], $sasl_args['authz_id'], $sasl_args['props']);
+            $dn = $this->connector->whoami();
+        } else {
+            $this->connector->bind($dn, $password);
+        }
 
         /* If the credentials were correct, rebind using a privileged account to read attributes */
         $readUsername = $this->ldapConfig->getOptionalString('priv.username', null);
@@ -145,6 +153,18 @@ protected function login(string $username, #[\SensitiveParameter]string $passwor
         return $this->processAttributes(/** @scrutinizer-ignore-type */$entry);
     }
 
+    /**
+     * Attempt to log in using the given username and password.
+     *
+     * @param string $username  The username the user wrote.
+     * @param string $password  The password the user wrote.
+     * @return array  Associative array with the users attributes.
+     */
+    protected function login(string $username, #[\SensitiveParameter]string $password): array
+    {
+        return $this->login_sasl($username, $password);
+    }
+
 
     /**
      * Attempt to find a user's attributes given its username.

src/Auth/Source/LdapMulti.php

@@ -105,13 +105,15 @@ public function __construct(array $info, array $config)
 
 
     /**
-     * Attempt to log in using the given username and password.
+     * Attempt to log in using SASL and the given username and password.
      *
      * @param string $username  The username the user wrote.
      * @param string $password  The password the user wrote.
+     * @param string $organizaion  The organization the user chose.
+     * @param array|null $sasl_args SASL options
      * @return array  Associative array with the users attributes.
      */
-    protected function login(string $username, #[\SensitiveParameter]string $password, string $organization): array
+    protected function login_sasl(string $username, #[\SensitiveParameter]string $password, string $organization, ?array $sasl_args): array
     {
         if ($this->includeOrgInUsername) {
             $username = $username . '@' . $organization;
@@ -128,15 +130,27 @@ protected function login(string $username, #[\SensitiveParameter]string $passwor
 
         $ldap = new class (['AuthId' => $authsource], $sourceConfig->toArray()) extends Ldap
         {
-            public function loginOverload(string $username, #[\SensitiveParameter]string $password): array
+            public function loginOverload(string $username, #[\SensitiveParameter]string $password, ?array $sasl_args): array
             {
-                return $this->login($username, $password);
+                return $this->login_sasl($username, $password, $sasl_args);
             }
         };
 
-        return $ldap->loginOverload($username, $password);
+        return $ldap->loginOverload($username, $password, $sasl_args);
     }
 
+    /**
+     * Attempt to log in using the given username and password.
+     *
+     * @param string $username  The username the user wrote.
+     * @param string $password  The password the user wrote.
+     * @param string $organizaion  The organization the user chose.
+     * @return array  Associative array with the users attributes.
+     */
+    protected function login(string $username, #[\SensitiveParameter]string $password, string $organization): array
+    {
+        return $this->login_sasl($username, $password, $organization);
+    }
 
     /**
      * Retrieve list of organizations.

src/Connector/Ldap.php

@@ -109,6 +109,32 @@ public function bind(?string $username, #[\SensitiveParameter]?string $password)
         }
     }
 
+    /**
+     * @inheritDoc
+     */
+    public function saslBind(?string $username, #[\SensitiveParameter]?string $password, ?string $mech, ?string $realm, ?string $authcId, ?string $authzId, ?string $props): void
+
+    {
+        try {
+            $this->connection->saslBind($username, strval($password), $mech, $realm, $authcId, $authzId, $props);
+        } catch (InvalidCredentialsException $e) {
+            throw new Error\Error($this->resolveBindError($e));
+        }
+
+        if ($username === null) {
+            Logger::debug("LDAP bind(): Anonymous bind succesful.");
+        } else {
+            Logger::debug(sprintf("LDAP bind(): Bind successful for DN '%s'.", $username));
+        }
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function whoami(): string
+    {
+        return $this->connection->whoami();
+    }
 
     /**
      * @inheritDoc

src/ConnectorInterface.php

@@ -28,6 +28,39 @@ public function bind(
     ): void;
 
 
+    /**
+     * Bind to an LDAP-server using SASL
+     *
+     * @param string|null $username
+     * @param string|null $password Null for passwordless logon
+     * @param string|null $mech 
+     * @param string|null $realm
+     * @param string|null $authcId
+     * @param string|null $authzId
+     * @param string|null $props
+     * @return void
+     *
+     * @throws \SimpleSAML\Error\Exception if none of the LDAP-servers could be contacted
+     */
+    public function saslBind(
+        ?string $username,
+        ?string $password,
+        ?string $mech,
+        ?string $realm,
+        ?string $authcId,
+        ?string $authzId,
+        ?string $props
+    ): void;
+
+
+    /**
+     * Return the authenticated DN
+     *
+     * @return string
+     */
+    public function whoami(): string;
+
+
     /**
      * Search the LDAP-directory for a specific object
      *