gss-genr.c revision 295367 
1/* $OpenBSD: gss-genr.c,v 1.23 2015/01/20 23:14:00 deraadt 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#include <sys/param.h>
33
34#include <limits.h>
35#include <stdarg.h>
36#include <string.h>
37#include <signal.h>
38#include <unistd.h>
39
40#include "xmalloc.h"
41#include "buffer.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/* Check that the OID in a data stream matches that in the context */
51int
52ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
53{
54	return (ctx != NULL && ctx->oid != GSS_C_NO_OID &&
55	    ctx->oid->length == len &&
56	    memcmp(ctx->oid->elements, data, len) == 0);
57}
58
59/* Set the contexts OID from a data stream */
60void
61ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len)
62{
63	if (ctx->oid != GSS_C_NO_OID) {
64		free(ctx->oid->elements);
65		free(ctx->oid);
66	}
67	ctx->oid = xcalloc(1, sizeof(gss_OID_desc));
68	ctx->oid->length = len;
69	ctx->oid->elements = xmalloc(len);
70	memcpy(ctx->oid->elements, data, len);
71}
72
73/* Set the contexts OID */
74void
75ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid)
76{
77	ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length);
78}
79
80/* All this effort to report an error ... */
81void
82ssh_gssapi_error(Gssctxt *ctxt)
83{
84	char *s;
85
86	s = ssh_gssapi_last_error(ctxt, NULL, NULL);
87	debug("%s", s);
88	free(s);
89}
90
91char *
92ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status,
93    OM_uint32 *minor_status)
94{
95	OM_uint32 lmin;
96	gss_buffer_desc msg = GSS_C_EMPTY_BUFFER;
97	OM_uint32 ctx;
98	Buffer b;
99	char *ret;
100
101	buffer_init(&b);
102
103	if (major_status != NULL)
104		*major_status = ctxt->major;
105	if (minor_status != NULL)
106		*minor_status = ctxt->minor;
107
108	ctx = 0;
109	/* The GSSAPI error */
110	do {
111		gss_display_status(&lmin, ctxt->major,
112		    GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg);
113
114		buffer_append(&b, msg.value, msg.length);
115		buffer_put_char(&b, '\n');
116
117		gss_release_buffer(&lmin, &msg);
118	} while (ctx != 0);
119
120	/* The mechanism specific error */
121	do {
122		gss_display_status(&lmin, ctxt->minor,
123		    GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg);
124
125		buffer_append(&b, msg.value, msg.length);
126		buffer_put_char(&b, '\n');
127
128		gss_release_buffer(&lmin, &msg);
129	} while (ctx != 0);
130
131	buffer_put_char(&b, '\0');
132	ret = xmalloc(buffer_len(&b));
133	buffer_get(&b, ret, buffer_len(&b));
134	buffer_free(&b);
135	return (ret);
136}
137
138/*
139 * Initialise our GSSAPI context. We use this opaque structure to contain all
140 * of the data which both the client and server need to persist across
141 * {accept,init}_sec_context calls, so that when we do it from the userauth
142 * stuff life is a little easier
143 */
144void
145ssh_gssapi_build_ctx(Gssctxt **ctx)
146{
147	*ctx = xcalloc(1, sizeof (Gssctxt));
148	(*ctx)->context = GSS_C_NO_CONTEXT;
149	(*ctx)->name = GSS_C_NO_NAME;
150	(*ctx)->oid = GSS_C_NO_OID;
151	(*ctx)->creds = GSS_C_NO_CREDENTIAL;
152	(*ctx)->client = GSS_C_NO_NAME;
153	(*ctx)->client_creds = GSS_C_NO_CREDENTIAL;
154}
155
156/* Delete our context, providing it has been built correctly */
157void
158ssh_gssapi_delete_ctx(Gssctxt **ctx)
159{
160	OM_uint32 ms;
161
162	if ((*ctx) == NULL)
163		return;
164	if ((*ctx)->context != GSS_C_NO_CONTEXT)
165		gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER);
166	if ((*ctx)->name != GSS_C_NO_NAME)
167		gss_release_name(&ms, &(*ctx)->name);
168	if ((*ctx)->oid != GSS_C_NO_OID) {
169		free((*ctx)->oid->elements);
170		free((*ctx)->oid);
171		(*ctx)->oid = GSS_C_NO_OID;
172	}
173	if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
174		gss_release_cred(&ms, &(*ctx)->creds);
175	if ((*ctx)->client != GSS_C_NO_NAME)
176		gss_release_name(&ms, &(*ctx)->client);
177	if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
178		gss_release_cred(&ms, &(*ctx)->client_creds);
179
180	free(*ctx);
181	*ctx = NULL;
182}
183
184/*
185 * Wrapper to init_sec_context
186 * Requires that the context contains:
187 *	oid
188 *	server name (from ssh_gssapi_import_name)
189 */
190OM_uint32
191ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
192    gss_buffer_desc* send_tok, OM_uint32 *flags)
193{
194	int deleg_flag = 0;
195
196	if (deleg_creds) {
197		deleg_flag = GSS_C_DELEG_FLAG;
198		debug("Delegating credentials");
199	}
200
201	ctx->major = gss_init_sec_context(&ctx->minor,
202	    GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid,
203	    GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
204	    0, NULL, recv_tok, NULL, send_tok, flags, NULL);
205
206	if (GSS_ERROR(ctx->major))
207		ssh_gssapi_error(ctx);
208
209	return (ctx->major);
210}
211
212/* Create a service name for the given host */
213OM_uint32
214ssh_gssapi_import_name(Gssctxt *ctx, const char *host)
215{
216	gss_buffer_desc gssbuf;
217	char *val;
218
219	xasprintf(&val, "host@%s", host);
220	gssbuf.value = val;
221	gssbuf.length = strlen(gssbuf.value);
222
223	if ((ctx->major = gss_import_name(&ctx->minor,
224	    &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name)))
225		ssh_gssapi_error(ctx);
226
227	free(gssbuf.value);
228	return (ctx->major);
229}
230
231OM_uint32
232ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
233{
234	if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
235	    GSS_C_QOP_DEFAULT, buffer, hash)))
236		ssh_gssapi_error(ctx);
237
238	return (ctx->major);
239}
240
241void
242ssh_gssapi_buildmic(Buffer *b, const char *user, const char *service,
243    const char *context)
244{
245	buffer_init(b);
246	buffer_put_string(b, session_id2, session_id2_len);
247	buffer_put_char(b, SSH2_MSG_USERAUTH_REQUEST);
248	buffer_put_cstring(b, user);
249	buffer_put_cstring(b, service);
250	buffer_put_cstring(b, context);
251}
252
253int
254ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
255{
256	gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
257	OM_uint32 major, minor;
258	gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
259
260	/* RFC 4462 says we MUST NOT do SPNEGO */
261	if (oid->length == spnego_oid.length &&
262	    (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0))
263		return 0; /* false */
264
265	ssh_gssapi_build_ctx(ctx);
266	ssh_gssapi_set_oid(*ctx, oid);
267	major = ssh_gssapi_import_name(*ctx, host);
268	if (!GSS_ERROR(major)) {
269		major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token,
270		    NULL);
271		gss_release_buffer(&minor, &token);
272		if ((*ctx)->context != GSS_C_NO_CONTEXT)
273			gss_delete_sec_context(&minor, &(*ctx)->context,
274			    GSS_C_NO_BUFFER);
275	}
276
277	if (GSS_ERROR(major))
278		ssh_gssapi_delete_ctx(ctx);
279
280	return (!GSS_ERROR(major));
281}
282
283#endif /* GSSAPI */
284