1/* $OpenBSD: gss-genr.c,v 1.26 2018/07/10 09:13:30 djm Exp $ */
2
3/*
4 * Copyright (c) 2001-2007 Simon Wilkinson. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include "includes.h"
28
29#ifdef GSSAPI
30
31#include <sys/types.h>
32
33#include <limits.h>
34#include <stdarg.h>
35#include <string.h>
36#include <signal.h>
37#include <unistd.h>
38
39#include "xmalloc.h"
40#include "ssherr.h"
41#include "sshbuf.h"
42#include "log.h"
43#include "ssh2.h"
44
45#include "ssh-gss.h"
46
47extern u_char *session_id2;
48extern u_int session_id2_len;
49
50/* sshbuf_get for gss_buffer_desc */
51int
52ssh_gssapi_get_buffer_desc(struct sshbuf *b, gss_buffer_desc *g)
53{
54	int r;
55	u_char *p;
56	size_t len;
57
58	if ((r = sshbuf_get_string(b, &p, &len)) != 0)
59		return r;
60	g->value = p;
61	g->length = len;
62	return 0;
63}
64
65/* Check that the OID in a data stream matches that in the context */
66int
67ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
68{
69	return (ctx != NULL && ctx->oid != GSS_C_NO_OID &&
70	    ctx->oid->length == len &&
71	    memcmp(ctx->oid->elements, data, len) == 0);
72}
73
74/* Set the contexts OID from a data stream */
75void
76ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len)
77{
78	if (ctx->oid != GSS_C_NO_OID) {
79		free(ctx->oid->elements);
80		free(ctx->oid);
81	}
82	ctx->oid = xcalloc(1, sizeof(gss_OID_desc));
83	ctx->oid->length = len;
84	ctx->oid->elements = xmalloc(len);
85	memcpy(ctx->oid->elements, data, len);
86}
87
88/* Set the contexts OID */
89void
90ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid)
91{
92	ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length);
93}
94
95/* All this effort to report an error ... */
96void
97ssh_gssapi_error(Gssctxt *ctxt)
98{
99	char *s;
100
101	s = ssh_gssapi_last_error(ctxt, NULL, NULL);
102	debug("%s", s);
103	free(s);
104}
105
106char *
107ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status,
108    OM_uint32 *minor_status)
109{
110	OM_uint32 lmin;
111	gss_buffer_desc msg = GSS_C_EMPTY_BUFFER;
112	OM_uint32 ctx;
113	struct sshbuf *b;
114	char *ret;
115	int r;
116
117	if ((b = sshbuf_new()) == NULL)
118		fatal("%s: sshbuf_new failed", __func__);
119
120	if (major_status != NULL)
121		*major_status = ctxt->major;
122	if (minor_status != NULL)
123		*minor_status = ctxt->minor;
124
125	ctx = 0;
126	/* The GSSAPI error */
127	do {
128		gss_display_status(&lmin, ctxt->major,
129		    GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg);
130
131		if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 ||
132		    (r = sshbuf_put_u8(b, '\n')) != 0)
133			fatal("%s: buffer error: %s", __func__, ssh_err(r));
134
135		gss_release_buffer(&lmin, &msg);
136	} while (ctx != 0);
137
138	/* The mechanism specific error */
139	do {
140		gss_display_status(&lmin, ctxt->minor,
141		    GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg);
142
143		if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 ||
144		    (r = sshbuf_put_u8(b, '\n')) != 0)
145			fatal("%s: buffer error: %s", __func__, ssh_err(r));
146
147		gss_release_buffer(&lmin, &msg);
148	} while (ctx != 0);
149
150	if ((r = sshbuf_put_u8(b, '\n')) != 0)
151		fatal("%s: buffer error: %s", __func__, ssh_err(r));
152	ret = xstrdup((const char *)sshbuf_ptr(b));
153	sshbuf_free(b);
154	return (ret);
155}
156
157/*
158 * Initialise our GSSAPI context. We use this opaque structure to contain all
159 * of the data which both the client and server need to persist across
160 * {accept,init}_sec_context calls, so that when we do it from the userauth
161 * stuff life is a little easier
162 */
163void
164ssh_gssapi_build_ctx(Gssctxt **ctx)
165{
166	*ctx = xcalloc(1, sizeof (Gssctxt));
167	(*ctx)->context = GSS_C_NO_CONTEXT;
168	(*ctx)->name = GSS_C_NO_NAME;
169	(*ctx)->oid = GSS_C_NO_OID;
170	(*ctx)->creds = GSS_C_NO_CREDENTIAL;
171	(*ctx)->client = GSS_C_NO_NAME;
172	(*ctx)->client_creds = GSS_C_NO_CREDENTIAL;
173}
174
175/* Delete our context, providing it has been built correctly */
176void
177ssh_gssapi_delete_ctx(Gssctxt **ctx)
178{
179	OM_uint32 ms;
180
181	if ((*ctx) == NULL)
182		return;
183	if ((*ctx)->context != GSS_C_NO_CONTEXT)
184		gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER);
185	if ((*ctx)->name != GSS_C_NO_NAME)
186		gss_release_name(&ms, &(*ctx)->name);
187	if ((*ctx)->oid != GSS_C_NO_OID) {
188		free((*ctx)->oid->elements);
189		free((*ctx)->oid);
190		(*ctx)->oid = GSS_C_NO_OID;
191	}
192	if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
193		gss_release_cred(&ms, &(*ctx)->creds);
194	if ((*ctx)->client != GSS_C_NO_NAME)
195		gss_release_name(&ms, &(*ctx)->client);
196	if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
197		gss_release_cred(&ms, &(*ctx)->client_creds);
198
199	free(*ctx);
200	*ctx = NULL;
201}
202
203/*
204 * Wrapper to init_sec_context
205 * Requires that the context contains:
206 *	oid
207 *	server name (from ssh_gssapi_import_name)
208 */
209OM_uint32
210ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
211    gss_buffer_desc* send_tok, OM_uint32 *flags)
212{
213	int deleg_flag = 0;
214
215	if (deleg_creds) {
216		deleg_flag = GSS_C_DELEG_FLAG;
217		debug("Delegating credentials");
218	}
219
220	ctx->major = gss_init_sec_context(&ctx->minor,
221	    GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid,
222	    GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
223	    0, NULL, recv_tok, NULL, send_tok, flags, NULL);
224
225	if (GSS_ERROR(ctx->major))
226		ssh_gssapi_error(ctx);
227
228	return (ctx->major);
229}
230
231/* Create a service name for the given host */
232OM_uint32
233ssh_gssapi_import_name(Gssctxt *ctx, const char *host)
234{
235	gss_buffer_desc gssbuf;
236	char *val;
237
238	xasprintf(&val, "host@%s", host);
239	gssbuf.value = val;
240	gssbuf.length = strlen(gssbuf.value);
241
242	if ((ctx->major = gss_import_name(&ctx->minor,
243	    &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name)))
244		ssh_gssapi_error(ctx);
245
246	free(gssbuf.value);
247	return (ctx->major);
248}
249
250OM_uint32
251ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
252{
253	if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
254	    GSS_C_QOP_DEFAULT, buffer, hash)))
255		ssh_gssapi_error(ctx);
256
257	return (ctx->major);
258}
259
260void
261ssh_gssapi_buildmic(struct sshbuf *b, const char *user, const char *service,
262    const char *context)
263{
264	int r;
265
266	sshbuf_reset(b);
267	if ((r = sshbuf_put_string(b, session_id2, session_id2_len)) != 0 ||
268	    (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
269	    (r = sshbuf_put_cstring(b, user)) != 0 ||
270	    (r = sshbuf_put_cstring(b, service)) != 0 ||
271	    (r = sshbuf_put_cstring(b, context)) != 0)
272		fatal("%s: buffer error: %s", __func__, ssh_err(r));
273}
274
275int
276ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
277{
278	gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
279	OM_uint32 major, minor;
280	gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
281
282	/* RFC 4462 says we MUST NOT do SPNEGO */
283	if (oid->length == spnego_oid.length &&
284	    (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0))
285		return 0; /* false */
286
287	ssh_gssapi_build_ctx(ctx);
288	ssh_gssapi_set_oid(*ctx, oid);
289	major = ssh_gssapi_import_name(*ctx, host);
290	if (!GSS_ERROR(major)) {
291		major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token,
292		    NULL);
293		gss_release_buffer(&minor, &token);
294		if ((*ctx)->context != GSS_C_NO_CONTEXT)
295			gss_delete_sec_context(&minor, &(*ctx)->context,
296			    GSS_C_NO_BUFFER);
297	}
298
299	if (GSS_ERROR(major))
300		ssh_gssapi_delete_ctx(ctx);
301
302	return (!GSS_ERROR(major));
303}
304
305#endif /* GSSAPI */
306