- markus@cvs.openbsd.org 2003/08/22 10:56:09

     [auth2.c auth2-gss.c auth.h compat.c compat.h gss-genr.c gss-serv-krb5.c
     gss-serv.c monitor.c monitor.h monitor_wrap.c monitor_wrap.h readconf.c
     readconf.h servconf.c servconf.h session.c session.h ssh-gss.h
     ssh_config.5 sshconnect2.c sshd_config sshd_config.5]
     support GSS API user authentication; patches from Simon Wilkinson,
     stripped down and tested by Jakob and myself.

1 files changed, 243 insertions, 0 deletions

diff --git a/auth2-gss.c b/auth2-gss.c
new file mode 100644
index 00000000..c7651112
--- /dev/null
+++ b/auth2-gss.c
@@ -0,0 +1,243 @@
+/*	$OpenBSD: auth2-gss.c,v 1.1 2003/08/22 10:56:08 markus Exp $	*/
+
+/*
+ * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "includes.h"
+
+#ifdef GSSAPI
+
+#include "auth.h"
+#include "ssh2.h"
+#include "xmalloc.h"
+#include "log.h"
+#include "dispatch.h"
+#include "servconf.h"
+#include "compat.h"
+#include "packet.h"
+#include "monitor_wrap.h"
+
+#include "ssh-gss.h"
+
+extern ServerOptions options;
+
+static void input_gssapi_token(int type, u_int32_t plen, void *ctxt);
+static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt);
+static void input_gssapi_errtok(int, u_int32_t, void *);
+
+/*
+ * We only support those mechanisms that we know about (ie ones that we know
+ * how to check local user kuserok and the like
+ */
+static int
+userauth_gssapi(Authctxt *authctxt)
+{
+	gss_OID_desc oid = {0, NULL};
+	Gssctxt *ctxt = NULL;
+	int mechs;
+	gss_OID_set supported;
+	int present;
+	OM_uint32 ms;
+	u_int len;
+	char *doid = NULL;
+
+	if (!authctxt->valid || authctxt->user == NULL)
+		return (0);
+
+	mechs = packet_get_int();
+	if (mechs == 0) {
+		debug("Mechanism negotiation is not supported");
+		return (0);
+	}
+
+	ssh_gssapi_supported_oids(&supported);
+	do {
+		mechs--;
+
+		if (doid)
+			xfree(doid);
+
+		doid = packet_get_string(&len);
+
+		if (doid[0] != SSH_GSS_OIDTYPE || doid[1] != len-2) {
+			logit("Mechanism OID received using the old encoding form");
+			oid.elements = doid;
+			oid.length = len;
+		} else {
+			oid.elements = doid + 2;
+			oid.length   = len - 2;
+		}
+		gss_test_oid_set_member(&ms, &oid, supported, &present);
+	} while (mechs > 0 && !present);
+
+	gss_release_oid_set(&ms, &supported);
+
+	if (!present) {
+		xfree(doid);
+		return (0);
+	}
+
+	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &oid))))
+		return (0);
+
+	authctxt->methoddata=(void *)ctxt;
+
+	packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
+
+	/* Return OID in same format as we received it*/
+	packet_put_string(doid, len);
+
+	packet_send();
+	xfree(doid);
+
+	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
+	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
+	authctxt->postponed = 1;
+
+	return (0);
+}
+
+static void
+input_gssapi_token(int type, u_int32_t plen, void *ctxt)
+{
+	Authctxt *authctxt = ctxt;
+	Gssctxt *gssctxt;
+	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
+	gss_buffer_desc recv_tok;
+	OM_uint32 maj_status, min_status;
+	u_int len;
+
+	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
+		fatal("No authentication or GSSAPI context");
+
+	gssctxt = authctxt->methoddata;
+	recv_tok.value = packet_get_string(&len);
+	recv_tok.length = len; /* u_int vs. size_t */
+
+	packet_check_eom();
+
+	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
+	    &send_tok, NULL));
+
+	xfree(recv_tok.value);
+
+	if (GSS_ERROR(maj_status)) {
+		if (send_tok.length != 0) {
+			packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
+			packet_put_string(send_tok.value, send_tok.length);
+			packet_send();
+		}
+		authctxt->postponed = 0;
+		dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
+		userauth_finish(authctxt, 0, "gssapi");
+	} else {
+		if (send_tok.length != 0) {
+			packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
+			packet_put_string(send_tok.value, send_tok.length);
+			packet_send();
+		}
+		if (maj_status == GSS_S_COMPLETE) {
+			dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
+			dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
+				     &input_gssapi_exchange_complete);
+		}
+	}
+
+	gss_release_buffer(&min_status, &send_tok);
+}
+
+static void
+input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
+{
+	Authctxt *authctxt = ctxt;
+	Gssctxt *gssctxt;
+	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
+	gss_buffer_desc recv_tok;
+	OM_uint32 maj_status;
+
+	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
+		fatal("No authentication or GSSAPI context");
+
+	gssctxt = authctxt->methoddata;
+	recv_tok.value = packet_get_string(&recv_tok.length);
+
+	packet_check_eom();
+
+	/* Push the error token into GSSAPI to see what it says */
+	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
+	    &send_tok, NULL));
+
+	xfree(recv_tok.value);
+
+	/* We can't return anything to the client, even if we wanted to */
+	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
+	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
+
+	/* The client will have already moved on to the next auth */
+
+	gss_release_buffer(&maj_status, &send_tok);
+}
+
+/*
+ * This is called when the client thinks we've completed authentication.
+ * It should only be enabled in the dispatch handler by the function above,
+ * which only enables it once the GSSAPI exchange is complete.
+ */
+
+static void
+input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt)
+{
+	Authctxt *authctxt = ctxt;
+	Gssctxt *gssctxt;
+	int authenticated;
+
+	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
+		fatal("No authentication or GSSAPI context");
+
+	gssctxt = authctxt->methoddata;
+
+	/*
+	 * We don't need to check the status, because the stored credentials
+	 * which userok uses are only populated once the context init step
+	 * has returned complete.
+	 */
+
+	packet_check_eom();
+
+	authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
+
+	authctxt->postponed = 0;
+	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
+	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
+	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
+	userauth_finish(authctxt, authenticated, "gssapi");
+}
+
+Authmethod method_gssapi = {
+	"gssapi",
+	userauth_gssapi,
+	&options.gss_authentication
+};
+
+#endif /* GSSAPI */