1/* $OpenBSD: gss-genr.c,v 1.29 2024/02/01 02:37:33 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 <stdlib.h>
38#include <unistd.h>
39
40#include "xmalloc.h"
41#include "ssherr.h"
42#include "sshbuf.h"
43#include "log.h"
44#include "ssh2.h"
45
46#include "ssh-gss.h"
47
48/* sshbuf_get for gss_buffer_desc */
49int
50ssh_gssapi_get_buffer_desc(struct sshbuf *b, gss_buffer_desc *g)
51{
52	int r;
53	u_char *p;
54	size_t len;
55
56	if ((r = sshbuf_get_string(b, &p, &len)) != 0)
57		return r;
58	g->value = p;
59	g->length = len;
60	return 0;
61}
62
63/* Check that the OID in a data stream matches that in the context */
64int
65ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
66{
67	return (ctx != NULL && ctx->oid != GSS_C_NO_OID &&
68	    ctx->oid->length == len &&
69	    memcmp(ctx->oid->elements, data, len) == 0);
70}
71
72/* Set the contexts OID from a data stream */
73void
74ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len)
75{
76	if (ctx->oid != GSS_C_NO_OID) {
77		free(ctx->oid->elements);
78		free(ctx->oid);
79	}
80	ctx->oid = xcalloc(1, sizeof(gss_OID_desc));
81	ctx->oid->length = len;
82	ctx->oid->elements = xmalloc(len);
83	memcpy(ctx->oid->elements, data, len);
84}
85
86/* Set the contexts OID */
87void
88ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid)
89{
90	ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length);
91}
92
93/* All this effort to report an error ... */
94void
95ssh_gssapi_error(Gssctxt *ctxt)
96{
97	char *s;
98
99	s = ssh_gssapi_last_error(ctxt, NULL, NULL);
100	debug("%s", s);
101	free(s);
102}
103
104char *
105ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status,
106    OM_uint32 *minor_status)
107{
108	OM_uint32 lmin;
109	gss_buffer_desc msg = GSS_C_EMPTY_BUFFER;
110	OM_uint32 ctx;
111	struct sshbuf *b;
112	char *ret;
113	int r;
114
115	if ((b = sshbuf_new()) == NULL)
116		fatal_f("sshbuf_new failed");
117
118	if (major_status != NULL)
119		*major_status = ctxt->major;
120	if (minor_status != NULL)
121		*minor_status = ctxt->minor;
122
123	ctx = 0;
124	/* The GSSAPI error */
125	do {
126		gss_display_status(&lmin, ctxt->major,
127		    GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg);
128
129		if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 ||
130		    (r = sshbuf_put_u8(b, '\n')) != 0)
131			fatal_fr(r, "assemble GSS_CODE");
132
133		gss_release_buffer(&lmin, &msg);
134	} while (ctx != 0);
135
136	/* The mechanism specific error */
137	do {
138		gss_display_status(&lmin, ctxt->minor,
139		    GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg);
140
141		if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 ||
142		    (r = sshbuf_put_u8(b, '\n')) != 0)
143			fatal_fr(r, "assemble MECH_CODE");
144
145		gss_release_buffer(&lmin, &msg);
146	} while (ctx != 0);
147
148	if ((r = sshbuf_put_u8(b, '\n')) != 0)
149		fatal_fr(r, "assemble newline");
150	ret = xstrdup((const char *)sshbuf_ptr(b));
151	sshbuf_free(b);
152	return (ret);
153}
154
155/*
156 * Initialise our GSSAPI context. We use this opaque structure to contain all
157 * of the data which both the client and server need to persist across
158 * {accept,init}_sec_context calls, so that when we do it from the userauth
159 * stuff life is a little easier
160 */
161void
162ssh_gssapi_build_ctx(Gssctxt **ctx)
163{
164	*ctx = xcalloc(1, sizeof (Gssctxt));
165	(*ctx)->context = GSS_C_NO_CONTEXT;
166	(*ctx)->name = GSS_C_NO_NAME;
167	(*ctx)->oid = GSS_C_NO_OID;
168	(*ctx)->creds = GSS_C_NO_CREDENTIAL;
169	(*ctx)->client = GSS_C_NO_NAME;
170	(*ctx)->client_creds = GSS_C_NO_CREDENTIAL;
171}
172
173/* Delete our context, providing it has been built correctly */
174void
175ssh_gssapi_delete_ctx(Gssctxt **ctx)
176{
177	OM_uint32 ms;
178
179	if ((*ctx) == NULL)
180		return;
181	if ((*ctx)->context != GSS_C_NO_CONTEXT)
182		gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER);
183	if ((*ctx)->name != GSS_C_NO_NAME)
184		gss_release_name(&ms, &(*ctx)->name);
185	if ((*ctx)->oid != GSS_C_NO_OID) {
186		free((*ctx)->oid->elements);
187		free((*ctx)->oid);
188		(*ctx)->oid = GSS_C_NO_OID;
189	}
190	if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
191		gss_release_cred(&ms, &(*ctx)->creds);
192	if ((*ctx)->client != GSS_C_NO_NAME)
193		gss_release_name(&ms, &(*ctx)->client);
194	if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
195		gss_release_cred(&ms, &(*ctx)->client_creds);
196
197	free(*ctx);
198	*ctx = NULL;
199}
200
201/*
202 * Wrapper to init_sec_context
203 * Requires that the context contains:
204 *	oid
205 *	server name (from ssh_gssapi_import_name)
206 */
207OM_uint32
208ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
209    gss_buffer_desc* send_tok, OM_uint32 *flags)
210{
211	int deleg_flag = 0;
212
213	if (deleg_creds) {
214		deleg_flag = GSS_C_DELEG_FLAG;
215		debug("Delegating credentials");
216	}
217
218	ctx->major = gss_init_sec_context(&ctx->minor,
219	    GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid,
220	    GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
221	    0, NULL, recv_tok, NULL, send_tok, flags, NULL);
222
223	if (GSS_ERROR(ctx->major))
224		ssh_gssapi_error(ctx);
225
226	return (ctx->major);
227}
228
229/* Create a service name for the given host */
230OM_uint32
231ssh_gssapi_import_name(Gssctxt *ctx, const char *host)
232{
233	gss_buffer_desc gssbuf;
234	char *val;
235
236	xasprintf(&val, "host@%s", host);
237	gssbuf.value = val;
238	gssbuf.length = strlen(gssbuf.value);
239
240	if ((ctx->major = gss_import_name(&ctx->minor,
241	    &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name)))
242		ssh_gssapi_error(ctx);
243
244	free(gssbuf.value);
245	return (ctx->major);
246}
247
248OM_uint32
249ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
250{
251	if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
252	    GSS_C_QOP_DEFAULT, buffer, hash)))
253		ssh_gssapi_error(ctx);
254
255	return (ctx->major);
256}
257
258void
259ssh_gssapi_buildmic(struct sshbuf *b, const char *user, const char *service,
260    const char *context, const struct sshbuf *session_id)
261{
262	int r;
263
264	sshbuf_reset(b);
265	if ((r = sshbuf_put_stringb(b, session_id)) != 0 ||
266	    (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
267	    (r = sshbuf_put_cstring(b, user)) != 0 ||
268	    (r = sshbuf_put_cstring(b, service)) != 0 ||
269	    (r = sshbuf_put_cstring(b, context)) != 0)
270		fatal_fr(r, "assemble buildmic");
271}
272
273int
274ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
275{
276	gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
277	OM_uint32 major, minor;
278	gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
279
280	/* RFC 4462 says we MUST NOT do SPNEGO */
281	if (oid->length == spnego_oid.length &&
282	    (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0))
283		return 0; /* false */
284
285	ssh_gssapi_build_ctx(ctx);
286	ssh_gssapi_set_oid(*ctx, oid);
287	major = ssh_gssapi_import_name(*ctx, host);
288	if (!GSS_ERROR(major)) {
289		major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token,
290		    NULL);
291		gss_release_buffer(&minor, &token);
292		if ((*ctx)->context != GSS_C_NO_CONTEXT)
293			gss_delete_sec_context(&minor, &(*ctx)->context,
294			    GSS_C_NO_BUFFER);
295	}
296
297	if (GSS_ERROR(major))
298		ssh_gssapi_delete_ctx(ctx);
299
300	return (!GSS_ERROR(major));
301}
302
303#endif /* GSSAPI */
304