Allow LDAP authentication to operate in search+bind mode, meaning it

does a search for the user in the directory first, and then binds with
the DN found for this user.

This allows for LDAP logins in scenarios where the DN of the user cannot
be determined simply by prefix and suffix, such as the case where different
users are located in different containers.

The old way of authentication can be significantly faster, so it's kept
as an option.

Robert Fleming and Magnus Hagander

1 files changed, 205 insertions, 43 deletions

diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
index 1e080465b67..7b6b5a5a071 100644
--- a/src/backend/libpq/auth.c
+++ b/src/backend/libpq/auth.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/libpq/auth.c,v 1.187 2009/10/16 22:08:36 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/libpq/auth.c,v 1.188 2009/12/12 21:35:21 mha Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2096,40 +2096,18 @@ CheckPAMAuth(Port *port, char *user, char *password)
  */
 #ifdef USE_LDAP
 
+/*
+ * Initialize a connection to the LDAP server, including setting up
+ * TLS if requested.
+ */
 static int
-CheckLDAPAuth(Port *port)
+InitializeLDAPConnection(Port *port, LDAP **ldap)
 {
-	char	   *passwd;
-	LDAP	   *ldap;
-	int			r;
 	int			ldapversion = LDAP_VERSION3;
-	char		fulluser[NAMEDATALEN + 256 + 1];
-
-	if (!port->hba->ldapserver || port->hba->ldapserver[0] == '\0')
-	{
-		ereport(LOG,
-				(errmsg("LDAP server not specified")));
-		return STATUS_ERROR;
-	}
-
-	if (port->hba->ldapport == 0)
-		port->hba->ldapport = LDAP_PORT;
-
-	sendAuthRequest(port, AUTH_REQ_PASSWORD);
-
-	passwd = recv_password_packet(port);
-	if (passwd == NULL)
-		return STATUS_EOF;		/* client wouldn't send password */
-
-	if (strlen(passwd) == 0)
-	{
-		ereport(LOG,
-				(errmsg("empty password returned by client")));
-		return STATUS_ERROR;
-	}
+	int			r;
 
-	ldap = ldap_init(port->hba->ldapserver, port->hba->ldapport);
-	if (!ldap)
+	*ldap = ldap_init(port->hba->ldapserver, port->hba->ldapport);
+	if (!*ldap)
 	{
 #ifndef WIN32
 		ereport(LOG,
@@ -2143,9 +2121,9 @@ CheckLDAPAuth(Port *port)
 		return STATUS_ERROR;
 	}
 
-	if ((r = ldap_set_option(ldap, LDAP_OPT_PROTOCOL_VERSION, &ldapversion)) != LDAP_SUCCESS)
+	if ((r = ldap_set_option(*ldap, LDAP_OPT_PROTOCOL_VERSION, &ldapversion)) != LDAP_SUCCESS)
 	{
-		ldap_unbind(ldap);
+		ldap_unbind(*ldap);
 		ereport(LOG,
 		  (errmsg("could not set LDAP protocol version: error code %d", r)));
 		return STATUS_ERROR;
@@ -2154,7 +2132,7 @@ CheckLDAPAuth(Port *port)
 	if (port->hba->ldaptls)
 	{
 #ifndef WIN32
-		if ((r = ldap_start_tls_s(ldap, NULL, NULL)) != LDAP_SUCCESS)
+		if ((r = ldap_start_tls_s(*ldap, NULL, NULL)) != LDAP_SUCCESS)
 #else
 		static __ldap_start_tls_sA _ldap_start_tls_sA = NULL;
 
@@ -2174,7 +2152,7 @@ CheckLDAPAuth(Port *port)
 				 * should never happen since we import other files from
 				 * wldap32, but check anyway
 				 */
-				ldap_unbind(ldap);
+				ldap_unbind(*ldap);
 				ereport(LOG,
 						(errmsg("could not load wldap32.dll")));
 				return STATUS_ERROR;
@@ -2182,7 +2160,7 @@ CheckLDAPAuth(Port *port)
 			_ldap_start_tls_sA = (__ldap_start_tls_sA) GetProcAddress(ldaphandle, "ldap_start_tls_sA");
 			if (_ldap_start_tls_sA == NULL)
 			{
-				ldap_unbind(ldap);
+				ldap_unbind(*ldap);
 				ereport(LOG,
 						(errmsg("could not load function _ldap_start_tls_sA in wldap32.dll"),
 						 errdetail("LDAP over SSL is not supported on this platform.")));
@@ -2195,21 +2173,202 @@ CheckLDAPAuth(Port *port)
 			 * per process and is automatically cleaned up on process exit.
 			 */
 		}
-		if ((r = _ldap_start_tls_sA(ldap, NULL, NULL, NULL, NULL)) != LDAP_SUCCESS)
+		if ((r = _ldap_start_tls_sA(*ldap, NULL, NULL, NULL, NULL)) != LDAP_SUCCESS)
 #endif
 		{
-			ldap_unbind(ldap);
+			ldap_unbind(*ldap);
 			ereport(LOG,
 			 (errmsg("could not start LDAP TLS session: error code %d", r)));
 			return STATUS_ERROR;
 		}
 	}
 
-	snprintf(fulluser, sizeof(fulluser), "%s%s%s",
-			 port->hba->ldapprefix ? port->hba->ldapprefix : "",
-			 port->user_name,
-			 port->hba->ldapsuffix ? port->hba->ldapsuffix : "");
-	fulluser[sizeof(fulluser) - 1] = '\0';
+	return STATUS_OK;
+}
+
+/*
+ * Perform LDAP authentication
+ */
+static int
+CheckLDAPAuth(Port *port)
+{
+	char	   *passwd;
+	LDAP	   *ldap;
+	int			r;
+	char	   *fulluser;
+
+	if (!port->hba->ldapserver || port->hba->ldapserver[0] == '\0')
+	{
+		ereport(LOG,
+				(errmsg("LDAP server not specified")));
+		return STATUS_ERROR;
+	}
+
+	if (port->hba->ldapport == 0)
+		port->hba->ldapport = LDAP_PORT;
+
+	sendAuthRequest(port, AUTH_REQ_PASSWORD);
+
+	passwd = recv_password_packet(port);
+	if (passwd == NULL)
+		return STATUS_EOF;		/* client wouldn't send password */
+
+	if (strlen(passwd) == 0)
+	{
+		ereport(LOG,
+				(errmsg("empty password returned by client")));
+		return STATUS_ERROR;
+	}
+
+	if (InitializeLDAPConnection(port, &ldap) == STATUS_ERROR)
+		/* Error message already sent */
+		return STATUS_ERROR;
+
+	if (port->hba->ldapbasedn)
+	{
+		/*
+		 * First perform an LDAP search to find the DN for the user we are trying to log
+		 * in as.
+		 */
+		char		   *filter;
+		LDAPMessage	   *search_message;
+		LDAPMessage	   *entry;
+		char		   *attributes[2];
+		char		   *dn;
+		char		   *c;
+
+		/*
+		 * Disallow any characters that we would otherwise need to escape, since they
+		 * aren't really reasonable in a username anyway. Allowing them would make it
+		 * possible to inject any kind of custom filters in the LDAP filter.
+		 */
+		for (c = port->user_name; *c; c++)
+		{
+			if (*c == '*' ||
+				*c == '(' ||
+				*c == ')' ||
+				*c == '\\' ||
+				*c == '/')
+			{
+				ereport(LOG,
+						(errmsg("invalid character in username for LDAP authentication")));
+				return STATUS_ERROR;
+			}
+		}
+
+		/*
+		 * Bind with a pre-defined username/password (if available) for searching. If
+		 * none is specified, this turns into an anonymous bind.
+		 */
+		r = ldap_simple_bind_s(ldap,
+							   port->hba->ldapbinddn ? port->hba->ldapbinddn : "",
+							   port->hba->ldapbindpasswd ? port->hba->ldapbindpasswd : "");
+		if (r != LDAP_SUCCESS)
+		{
+			ereport(LOG,
+					(errmsg("could not perform initial LDAP bind for ldapbinddn \"%s\" on server \"%s\": error code %d",
+							port->hba->ldapbinddn, port->hba->ldapserver, r)));
+			return STATUS_ERROR;
+		}
+
+		/* Fetch just one attribute, else *all* attributes are returned */
+		attributes[0] = port->hba->ldapsearchattribute ? port->hba->ldapsearchattribute : "uid";
+		attributes[1] = NULL;
+
+		filter = palloc(strlen(attributes[0])+strlen(port->user_name)+4);
+		sprintf(filter, "(%s=%s)",
+				 attributes[0],
+				 port->user_name);
+
+		r = ldap_search_s(ldap,
+						  port->hba->ldapbasedn,
+						  LDAP_SCOPE_SUBTREE,
+						  filter,
+						  attributes,
+						  0,
+						  &search_message);
+
+		if (r != LDAP_SUCCESS)
+		{
+			ereport(LOG,
+					(errmsg("could not search LDAP for filter \"%s\" on server \"%s\": error code %d",
+							filter, port->hba->ldapserver, r)));
+			pfree(filter);
+			return STATUS_ERROR;
+		}
+
+		if (ldap_count_entries(ldap, search_message) != 1)
+		{
+			if (ldap_count_entries(ldap, search_message) == 0)
+				ereport(LOG,
+						(errmsg("LDAP search failed for filter \"%s\" on server \"%s\": no such user",
+								filter, port->hba->ldapserver)));
+			else
+				ereport(LOG,
+						(errmsg("LDAP search failed for filter \"%s\" on server \"%s\": user is not unique (%d matches)",
+								filter, port->hba->ldapserver, ldap_count_entries(ldap, search_message))));
+
+			pfree(filter);
+			ldap_msgfree(search_message);
+			return STATUS_ERROR;
+		}
+
+		entry = ldap_first_entry(ldap, search_message);
+		dn = ldap_get_dn(ldap, entry);
+		if (dn == NULL)
+		{
+			int error;
+			(void)ldap_get_option(ldap, LDAP_OPT_ERROR_NUMBER, &error);
+			ereport(LOG,
+					(errmsg("could not get dn for the first entry matching \"%s\" on server \"%s\": %s",
+							filter, port->hba->ldapserver, ldap_err2string(error))));
+			pfree(filter);
+			ldap_msgfree(search_message);
+			return STATUS_ERROR;
+		}
+		fulluser = pstrdup(dn);
+
+		pfree(filter);
+		ldap_memfree(dn);
+		ldap_msgfree(search_message);
+
+		/* Unbind and disconnect from the LDAP server */
+		r = ldap_unbind_s(ldap);
+		if (r != LDAP_SUCCESS)
+		{
+			int error;
+			(void)ldap_get_option(ldap, LDAP_OPT_ERROR_NUMBER, &error);
+			ereport(LOG,
+					(errmsg("could not unbind after searching for user \"%s\" on server \"%s\": %s",
+							fulluser, port->hba->ldapserver, ldap_err2string(error))));
+			pfree(fulluser);
+			return STATUS_ERROR;
+		}
+
+		/*
+		 * Need to re-initialize the LDAP connection, so that we can bind
+		 * to it with a different username.
+		 */
+		if (InitializeLDAPConnection(port, &ldap) == STATUS_ERROR)
+		{
+			pfree(fulluser);
+
+			/* Error message already sent */
+			return STATUS_ERROR;
+		}
+	}
+	else
+	{
+		fulluser = palloc((port->hba->ldapprefix ? strlen(port->hba->ldapprefix) : 0) +
+						  strlen(port->user_name) +
+						  (port->hba->ldapsuffix ? strlen(port->hba->ldapsuffix) : 0) +
+						  1);
+
+		sprintf(fulluser, "%s%s%s",
+				 port->hba->ldapprefix ? port->hba->ldapprefix : "",
+				 port->user_name,
+				 port->hba->ldapsuffix ? port->hba->ldapsuffix : "");
+	}
 
 	r = ldap_simple_bind_s(ldap, fulluser, passwd);
 	ldap_unbind(ldap);
@@ -2219,9 +2378,12 @@ CheckLDAPAuth(Port *port)
 		ereport(LOG,
 				(errmsg("LDAP login failed for user \"%s\" on server \"%s\": error code %d",
 						fulluser, port->hba->ldapserver, r)));
+		pfree(fulluser);
 		return STATUS_ERROR;
 	}
 
+	pfree(fulluser);
+
 	return STATUS_OK;
 }
 #endif   /* USE_LDAP */