1/* $OpenBSD: gss-genr.c,v 1.24 2016/09/12 01:22:38 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
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 "buffer.h"
41#include "log.h"
42#include "ssh2.h"
43
44#include "ssh-gss.h"
45
46extern u_char *session_id2;
47extern u_int session_id2_len;
48
49/* Check that the OID in a data stream matches that in the context */
50int
51ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
52{
53	return (ctx != NULL && ctx->oid != GSS_C_NO_OID &&
54	    ctx->oid->length == len &&
55	    memcmp(ctx->oid->elements, data, len) == 0);
56}
57
58/* Set the contexts OID from a data stream */
59void
60ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len)
61{
62	if (ctx->oid != GSS_C_NO_OID) {
63		free(ctx->oid->elements);
64		free(ctx->oid);
65	}
66	ctx->oid = xcalloc(1, sizeof(gss_OID_desc));
67	ctx->oid->length = len;
68	ctx->oid->elements = xmalloc(len);
69	memcpy(ctx->oid->elements, data, len);
70}
71
72/* Set the contexts OID */
73void
74ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid)
75{
76	ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length);
77}
78
79/* All this effort to report an error ... */
80void
81ssh_gssapi_error(Gssctxt *ctxt)
82{
83	char *s;
84
85	s = ssh_gssapi_last_error(ctxt, NULL, NULL);
86	debug("%s", s);
87	free(s);
88}
89
90char *
91ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status,
92    OM_uint32 *minor_status)
93{
94	OM_uint32 lmin;
95	gss_buffer_desc msg = GSS_C_EMPTY_BUFFER;
96	OM_uint32 ctx;
97	Buffer b;
98	char *ret;
99
100	buffer_init(&b);
101
102	if (major_status != NULL)
103		*major_status = ctxt->major;
104	if (minor_status != NULL)
105		*minor_status = ctxt->minor;
106
107	ctx = 0;
108	/* The GSSAPI error */
109	do {
110		gss_display_status(&lmin, ctxt->major,
111		    GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg);
112
113		buffer_append(&b, msg.value, msg.length);
114		buffer_put_char(&b, '\n');
115
116		gss_release_buffer(&lmin, &msg);
117	} while (ctx != 0);
118
119	/* The mechanism specific error */
120	do {
121		gss_display_status(&lmin, ctxt->minor,
122		    GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg);
123
124		buffer_append(&b, msg.value, msg.length);
125		buffer_put_char(&b, '\n');
126
127		gss_release_buffer(&lmin, &msg);
128	} while (ctx != 0);
129
130	buffer_put_char(&b, '\0');
131	ret = xmalloc(buffer_len(&b));
132	buffer_get(&b, ret, buffer_len(&b));
133	buffer_free(&b);
134	return (ret);
135}
136
137/*
138 * Initialise our GSSAPI context. We use this opaque structure to contain all
139 * of the data which both the client and server need to persist across
140 * {accept,init}_sec_context calls, so that when we do it from the userauth
141 * stuff life is a little easier
142 */
143void
144ssh_gssapi_build_ctx(Gssctxt **ctx)
145{
146	*ctx = xcalloc(1, sizeof (Gssctxt));
147	(*ctx)->context = GSS_C_NO_CONTEXT;
148	(*ctx)->name = GSS_C_NO_NAME;
149	(*ctx)->oid = GSS_C_NO_OID;
150	(*ctx)->creds = GSS_C_NO_CREDENTIAL;
151	(*ctx)->client = GSS_C_NO_NAME;
152	(*ctx)->client_creds = GSS_C_NO_CREDENTIAL;
153}
154
155/* Delete our context, providing it has been built correctly */
156void
157ssh_gssapi_delete_ctx(Gssctxt **ctx)
158{
159	OM_uint32 ms;
160
161	if ((*ctx) == NULL)
162		return;
163	if ((*ctx)->context != GSS_C_NO_CONTEXT)
164		gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER);
165	if ((*ctx)->name != GSS_C_NO_NAME)
166		gss_release_name(&ms, &(*ctx)->name);
167	if ((*ctx)->oid != GSS_C_NO_OID) {
168		free((*ctx)->oid->elements);
169		free((*ctx)->oid);
170		(*ctx)->oid = GSS_C_NO_OID;
171	}
172	if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
173		gss_release_cred(&ms, &(*ctx)->creds);
174	if ((*ctx)->client != GSS_C_NO_NAME)
175		gss_release_name(&ms, &(*ctx)->client);
176	if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
177		gss_release_cred(&ms, &(*ctx)->client_creds);
178
179	free(*ctx);
180	*ctx = NULL;
181}
182
183/*
184 * Wrapper to init_sec_context
185 * Requires that the context contains:
186 *	oid
187 *	server name (from ssh_gssapi_import_name)
188 */
189OM_uint32
190ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
191    gss_buffer_desc* send_tok, OM_uint32 *flags)
192{
193	int deleg_flag = 0;
194
195	if (deleg_creds) {
196		deleg_flag = GSS_C_DELEG_FLAG;
197		debug("Delegating credentials");
198	}
199
200	ctx->major = gss_init_sec_context(&ctx->minor,
201	    GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid,
202	    GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
203	    0, NULL, recv_tok, NULL, send_tok, flags, NULL);
204
205	if (GSS_ERROR(ctx->major))
206		ssh_gssapi_error(ctx);
207
208	return (ctx->major);
209}
210
211/* Create a service name for the given host */
212OM_uint32
213ssh_gssapi_import_name(Gssctxt *ctx, const char *host)
214{
215	gss_buffer_desc gssbuf;
216	char *val;
217
218	xasprintf(&val, "host@%s", host);
219	gssbuf.value = val;
220	gssbuf.length = strlen(gssbuf.value);
221
222	if ((ctx->major = gss_import_name(&ctx->minor,
223	    &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name)))
224		ssh_gssapi_error(ctx);
225
226	free(gssbuf.value);
227	return (ctx->major);
228}
229
230OM_uint32
231ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
232{
233	if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
234	    GSS_C_QOP_DEFAULT, buffer, hash)))
235		ssh_gssapi_error(ctx);
236
237	return (ctx->major);
238}
239
240void
241ssh_gssapi_buildmic(Buffer *b, const char *user, const char *service,
242    const char *context)
243{
244	buffer_init(b);
245	buffer_put_string(b, session_id2, session_id2_len);
246	buffer_put_char(b, SSH2_MSG_USERAUTH_REQUEST);
247	buffer_put_cstring(b, user);
248	buffer_put_cstring(b, service);
249	buffer_put_cstring(b, context);
250}
251
252int
253ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
254{
255	gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
256	OM_uint32 major, minor;
257	gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
258
259	/* RFC 4462 says we MUST NOT do SPNEGO */
260	if (oid->length == spnego_oid.length &&
261	    (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0))
262		return 0; /* false */
263
264	ssh_gssapi_build_ctx(ctx);
265	ssh_gssapi_set_oid(*ctx, oid);
266	major = ssh_gssapi_import_name(*ctx, host);
267	if (!GSS_ERROR(major)) {
268		major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token,
269		    NULL);
270		gss_release_buffer(&minor, &token);
271		if ((*ctx)->context != GSS_C_NO_CONTEXT)
272			gss_delete_sec_context(&minor, &(*ctx)->context,
273			    GSS_C_NO_BUFFER);
274	}
275
276	if (GSS_ERROR(major))
277		ssh_gssapi_delete_ctx(ctx);
278
279	return (!GSS_ERROR(major));
280}
281
282#endif /* GSSAPI */
283