xref: /freebsd/crypto/openssh/gss-genr.c (revision 7fdf597e96a02165cfe22ff357b857d5fa15ed8a)
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 */
49 int
50 ssh_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 */
64 int
65 ssh_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 */
73 void
74 ssh_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 */
87 void
88 ssh_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 ... */
94 void
95 ssh_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 
104 char *
105 ssh_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  */
161 void
162 ssh_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 */
174 void
175 ssh_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  */
207 OM_uint32
208 ssh_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 */
230 OM_uint32
231 ssh_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 
248 OM_uint32
249 ssh_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 
258 void
259 ssh_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 
273 int
274 ssh_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