From a6f795ba3d6048b32d7863468688bf7f42b2cafd Mon Sep 17 00:00:00 2001
From: Sumit Bose <sbose@redhat.com>
Date: Fri, 11 Oct 2019 16:39:25 +0200
Subject: [PATCH 4/6] Use GSS-SPNEGO if available

Currently adcli uses the GSSAPI SASL mechanism for LDAP authentication
and to establish encryption. While this works in general it does not
handle some of the more advanced features which can be required by AD
DCs.

The GSS-SPNEGO mechanism can handle them and is used with this patch by
adcli if the AD DC indicates that it supports it.

Related to https://bugzilla.redhat.com/show_bug.cgi?id=1762420
---
 library/adconn.c | 35 ++++++++++++++++++++++++++++++++++-
 library/adconn.h |  3 +++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/library/adconn.c b/library/adconn.c
index bcaced8..ffb54f9 100644
--- a/library/adconn.c
+++ b/library/adconn.c
@@ -77,6 +77,7 @@ struct _adcli_conn_ctx {
 	char *default_naming_context;
 	char *configuration_naming_context;
 	char **supported_capabilities;
+	char **supported_sasl_mechs;
 
 	/* Connect state */
 	LDAP *ldap;
@@ -845,6 +846,7 @@ connect_and_lookup_naming (adcli_conn *conn,
 		"defaultNamingContext",
 		"configurationNamingContext",
 		"supportedCapabilities",
+		"supportedSASLMechanisms",
 		NULL
 	};
 
@@ -897,6 +899,11 @@ connect_and_lookup_naming (adcli_conn *conn,
 		                                                         "supportedCapabilities");
 	}
 
+	if (conn->supported_sasl_mechs == NULL) {
+		conn->supported_sasl_mechs = _adcli_ldap_parse_values (ldap, results,
+		                                                       "supportedSASLMechanisms");
+	}
+
 	ldap_msgfree (results);
 
 	if (conn->default_naming_context == NULL) {
@@ -1022,6 +1029,7 @@ authenticate_to_directory (adcli_conn *conn)
 	OM_uint32 minor;
 	ber_len_t ssf;
 	int ret;
+	const char *mech = "GSSAPI";
 
 	if (conn->ldap_authenticated)
 		return ADCLI_SUCCESS;
@@ -1038,7 +1046,11 @@ authenticate_to_directory (adcli_conn *conn)
 	ret = ldap_set_option (conn->ldap, LDAP_OPT_X_SASL_SSF_MIN, &ssf);
 	return_unexpected_if_fail (ret == 0);
 
-	ret = ldap_sasl_interactive_bind_s (conn->ldap, NULL, "GSSAPI", NULL, NULL,
+	if (adcli_conn_server_has_sasl_mech (conn, "GSS-SPNEGO")) {
+		mech =  "GSS-SPNEGO";
+	}
+
+	ret = ldap_sasl_interactive_bind_s (conn->ldap, NULL, mech, NULL, NULL,
 	                                    LDAP_SASL_QUIET, sasl_interact, NULL);
 
 	/* Clear the credential cache GSSAPI to use (for this thread) */
@@ -1231,6 +1243,7 @@ conn_free (adcli_conn *conn)
 	free (conn->default_naming_context);
 	free (conn->configuration_naming_context);
 	_adcli_strv_free (conn->supported_capabilities);
+	_adcli_strv_free (conn->supported_sasl_mechs);
 
 	free (conn->computer_name);
 	free (conn->host_fqdn);
@@ -1606,6 +1619,26 @@ adcli_conn_server_has_capability (adcli_conn *conn,
 	return 0;
 }
 
+bool
+adcli_conn_server_has_sasl_mech (adcli_conn *conn,
+                                 const char *mech)
+{
+	int i;
+
+	return_val_if_fail (conn != NULL, false);
+	return_val_if_fail (mech != NULL, false);
+
+	if (!conn->supported_sasl_mechs)
+		return false;
+
+	for (i = 0; conn->supported_sasl_mechs[i] != NULL; i++) {
+		if (strcasecmp (mech, conn->supported_sasl_mechs[i]) == 0)
+			return true;
+	}
+
+	return false;
+}
+
 bool adcli_conn_is_writeable (adcli_conn *conn)
 {
 	disco_dance_if_necessary (conn);
diff --git a/library/adconn.h b/library/adconn.h
index 1ad5715..37ebdd9 100644
--- a/library/adconn.h
+++ b/library/adconn.h
@@ -149,6 +149,9 @@ void                adcli_conn_set_krb5_conf_dir     (adcli_conn *conn,
 int                 adcli_conn_server_has_capability (adcli_conn *conn,
                                                       const char *capability);
 
+bool                adcli_conn_server_has_sasl_mech  (adcli_conn *conn,
+                                                      const char *mech);
+
 bool                adcli_conn_is_writeable          (adcli_conn *conn);
 
 #endif /* ADCONN_H_ */
-- 
2.25.1