1 files changed, 335 insertions, 0 deletions
diff --git a/auth2-gss.c b/auth2-gss.c
new file mode 100644
index 0000000..9351e04
--- /dev/null
+++ b/auth2-gss.c
@@ -0,0 +1,335 @@
+/* $OpenBSD: auth2-gss.c,v 1.29 2018/07/31 03:10:27 djm 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 <sys/types.h>
+
+#include <stdarg.h>
+
+#include "xmalloc.h"
+#include "sshkey.h"
+#include "hostfile.h"
+#include "auth.h"
+#include "ssh2.h"
+#include "log.h"
+#include "dispatch.h"
+#include "sshbuf.h"
+#include "ssherr.h"
+#include "misc.h"
+#include "servconf.h"
+#include "packet.h"
+#include "ssh-gss.h"
+#include "monitor_wrap.h"
+
+extern ServerOptions options;
+
+static int input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh);
+static int input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh);
+static int input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh);
+static int input_gssapi_errtok(int, u_int32_t, struct ssh *);
+
+/*
+ * 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(struct ssh *ssh)
+{
+	Authctxt *authctxt = ssh->authctxt;
+	gss_OID_desc goid = {0, NULL};
+	Gssctxt *ctxt = NULL;
+	int r, present;
+	u_int mechs;
+	OM_uint32 ms;
+	size_t len;
+	u_char *doid = NULL;
+
+	if ((r = sshpkt_get_u32(ssh, &mechs)) != 0)
+		fatal("%s: %s", __func__, ssh_err(r));
+
+	if (mechs == 0) {
+		debug("Mechanism negotiation is not supported");
+		return (0);
+	}
+
+	do {
+		mechs--;
+
+		free(doid);
+
+		present = 0;
+		if ((r = sshpkt_get_string(ssh, &doid, &len)) != 0)
+			fatal("%s: %s", __func__, ssh_err(r));
+
+		if (len > 2 && doid[0] == SSH_GSS_OIDTYPE &&
+		    doid[1] == len - 2) {
+			goid.elements = doid + 2;
+			goid.length   = len - 2;
+			ssh_gssapi_test_oid_supported(&ms, &goid, &present);
+		} else {
+			logit("Badly formed OID received");
+		}
+	} while (mechs > 0 && !present);
+
+	if (!present) {
+		free(doid);
+		authctxt->server_caused_failure = 1;
+		return (0);
+	}
+
+	if (!authctxt->valid || authctxt->user == NULL) {
+		debug2("%s: disabled because of invalid user", __func__);
+		free(doid);
+		return (0);
+	}
+
+	if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
+		if (ctxt != NULL)
+			ssh_gssapi_delete_ctx(&ctxt);
+		free(doid);
+		authctxt->server_caused_failure = 1;
+		return (0);
+	}
+
+	authctxt->methoddata = (void *)ctxt;
+
+	/* Return the OID that we received */
+	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_GSSAPI_RESPONSE)) != 0 ||
+	    (r = sshpkt_put_string(ssh, doid, len)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		fatal("%s: %s", __func__, ssh_err(r));
+
+	free(doid);
+
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
+	authctxt->postponed = 1;
+
+	return (0);
+}
+
+static int
+input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh)
+{
+	Authctxt *authctxt = ssh->authctxt;
+	Gssctxt *gssctxt;
+	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
+	gss_buffer_desc recv_tok;
+	OM_uint32 maj_status, min_status, flags;
+	u_char *p;
+	size_t len;
+	int r;
+
+	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
+		fatal("No authentication or GSSAPI context");
+
+	gssctxt = authctxt->methoddata;
+	if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		fatal("%s: %s", __func__, ssh_err(r));
+
+	recv_tok.value = p;
+	recv_tok.length = len;
+	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
+	    &send_tok, &flags));
+
+	free(p);
+
+	if (GSS_ERROR(maj_status)) {
+		if (send_tok.length != 0) {
+			if ((r = sshpkt_start(ssh,
+			    SSH2_MSG_USERAUTH_GSSAPI_ERRTOK)) != 0 ||
+			    (r = sshpkt_put_string(ssh, send_tok.value,
+			    send_tok.length)) != 0 ||
+			    (r = sshpkt_send(ssh)) != 0)
+				fatal("%s: %s", __func__, ssh_err(r));
+		}
+		authctxt->postponed = 0;
+		ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
+		userauth_finish(ssh, 0, "gssapi-with-mic", NULL);
+	} else {
+		if (send_tok.length != 0) {
+			if ((r = sshpkt_start(ssh,
+			    SSH2_MSG_USERAUTH_GSSAPI_TOKEN)) != 0 ||
+			    (r = sshpkt_put_string(ssh, send_tok.value,
+			    send_tok.length)) != 0 ||
+			    (r = sshpkt_send(ssh)) != 0)
+				fatal("%s: %s", __func__, ssh_err(r));
+		}
+		if (maj_status == GSS_S_COMPLETE) {
+			ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
+			if (flags & GSS_C_INTEG_FLAG)
+				ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC,
+				    &input_gssapi_mic);
+			else
+				ssh_dispatch_set(ssh,
+				    SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
+				    &input_gssapi_exchange_complete);
+		}
+	}
+
+	gss_release_buffer(&min_status, &send_tok);
+	return 0;
+}
+
+static int
+input_gssapi_errtok(int type, u_int32_t plen, struct ssh *ssh)
+{
+	Authctxt *authctxt = ssh->authctxt;
+	Gssctxt *gssctxt;
+	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
+	gss_buffer_desc recv_tok;
+	OM_uint32 maj_status;
+	int r;
+	u_char *p;
+	size_t len;
+
+	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
+		fatal("No authentication or GSSAPI context");
+
+	gssctxt = authctxt->methoddata;
+	if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		fatal("%s: %s", __func__, ssh_err(r));
+	recv_tok.value = p;
+	recv_tok.length = len;
+
+	/* Push the error token into GSSAPI to see what it says */
+	maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
+	    &send_tok, NULL));
+
+	free(recv_tok.value);
+
+	/* We can't return anything to the client, even if we wanted to */
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
+
+	/* The client will have already moved on to the next auth */
+
+	gss_release_buffer(&maj_status, &send_tok);
+	return 0;
+}
+
+/*
+ * 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 int
+input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh)
+{
+	Authctxt *authctxt = ssh->authctxt;
+	int r, authenticated;
+	const char *displayname;
+
+	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
+		fatal("No authentication or GSSAPI context");
+
+	/*
+	 * We don't need to check the status, because we're only enabled in
+	 * the dispatcher once the exchange is complete
+	 */
+
+	if ((r = sshpkt_get_end(ssh)) != 0)
+		fatal("%s: %s", __func__, ssh_err(r));
+
+	authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
+
+	if ((!use_privsep || mm_is_monitor()) &&
+	    (displayname = ssh_gssapi_displayname()) != NULL)
+		auth2_record_info(authctxt, "%s", displayname);
+
+	authctxt->postponed = 0;
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
+	userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL);
+	return 0;
+}
+
+static int
+input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh)
+{
+	Authctxt *authctxt = ssh->authctxt;
+	Gssctxt *gssctxt;
+	int r, authenticated = 0;
+	struct sshbuf *b;
+	gss_buffer_desc mic, gssbuf;
+	const char *displayname;
+	u_char *p;
+	size_t len;
+
+	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
+		fatal("No authentication or GSSAPI context");
+
+	gssctxt = authctxt->methoddata;
+
+	if ((r = sshpkt_get_string(ssh, &p, &len)) != 0)
+		fatal("%s: %s", __func__, ssh_err(r));
+	if ((b = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new failed", __func__);
+	mic.value = p;
+	mic.length = len;
+	ssh_gssapi_buildmic(b, authctxt->user, authctxt->service,
+	    "gssapi-with-mic");
+
+	if ((gssbuf.value = sshbuf_mutable_ptr(b)) == NULL)
+		fatal("%s: sshbuf_mutable_ptr failed", __func__);
+	gssbuf.length = sshbuf_len(b);
+
+	if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
+		authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
+	else
+		logit("GSSAPI MIC check failed");
+
+	sshbuf_free(b);
+	free(mic.value);
+
+	if ((!use_privsep || mm_is_monitor()) &&
+	    (displayname = ssh_gssapi_displayname()) != NULL)
+		auth2_record_info(authctxt, "%s", displayname);
+
+	authctxt->postponed = 0;
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
+	userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL);
+	return 0;
+}
+
+Authmethod method_gssapi = {
+	"gssapi-with-mic",
+	userauth_gssapi,
+	&options.gss_authentication
+};
+
+#endif /* GSSAPI */