1 /* $OpenBSD: gss-serv.c,v 1.23 2011/08/01 19:18:15 markus Exp $ */
2
3 /*
4 * Copyright (c) 2001-2003 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 <stdarg.h>
35 #include <string.h>
36 #include <unistd.h>
37
38 #include "openbsd-compat/sys-queue.h"
39 #include "xmalloc.h"
40 #include "buffer.h"
41 #include "key.h"
42 #include "hostfile.h"
43 #include "auth.h"
44 #include "log.h"
45 #include "channels.h"
46 #include "session.h"
47 #include "misc.h"
48
49 #include "ssh-gss.h"
50
51 static ssh_gssapi_client gssapi_client =
52 { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
53 GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL}};
54
55 ssh_gssapi_mech gssapi_null_mech =
56 { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
57
58 #ifdef KRB5
59 extern ssh_gssapi_mech gssapi_kerberos_mech;
60 #endif
61
62 ssh_gssapi_mech* supported_mechs[]= {
63 #ifdef KRB5
64 &gssapi_kerberos_mech,
65 #endif
66 &gssapi_null_mech,
67 };
68
69
70 /*
71 * Acquire credentials for a server running on the current host.
72 * Requires that the context structure contains a valid OID
73 */
74
75 /* Returns a GSSAPI error code */
76 /* Privileged (called from ssh_gssapi_server_ctx) */
77 static OM_uint32
ssh_gssapi_acquire_cred(Gssctxt * ctx)78 ssh_gssapi_acquire_cred(Gssctxt *ctx)
79 {
80 OM_uint32 status;
81 char lname[MAXHOSTNAMELEN];
82 gss_OID_set oidset;
83
84 gss_create_empty_oid_set(&status, &oidset);
85 gss_add_oid_set_member(&status, ctx->oid, &oidset);
86
87 if (gethostname(lname, MAXHOSTNAMELEN)) {
88 gss_release_oid_set(&status, &oidset);
89 return (-1);
90 }
91
92 if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) {
93 gss_release_oid_set(&status, &oidset);
94 return (ctx->major);
95 }
96
97 if ((ctx->major = gss_acquire_cred(&ctx->minor,
98 ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds, NULL, NULL)))
99 ssh_gssapi_error(ctx);
100
101 gss_release_oid_set(&status, &oidset);
102 return (ctx->major);
103 }
104
105 /* Privileged */
106 OM_uint32
ssh_gssapi_server_ctx(Gssctxt ** ctx,gss_OID oid)107 ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid)
108 {
109 if (*ctx)
110 ssh_gssapi_delete_ctx(ctx);
111 ssh_gssapi_build_ctx(ctx);
112 ssh_gssapi_set_oid(*ctx, oid);
113 return (ssh_gssapi_acquire_cred(*ctx));
114 }
115
116 /* Unprivileged */
117 void
ssh_gssapi_supported_oids(gss_OID_set * oidset)118 ssh_gssapi_supported_oids(gss_OID_set *oidset)
119 {
120 int i = 0;
121 OM_uint32 min_status;
122 int present;
123 gss_OID_set supported;
124
125 gss_create_empty_oid_set(&min_status, oidset);
126 gss_indicate_mechs(&min_status, &supported);
127
128 while (supported_mechs[i]->name != NULL) {
129 if (GSS_ERROR(gss_test_oid_set_member(&min_status,
130 &supported_mechs[i]->oid, supported, &present)))
131 present = 0;
132 if (present)
133 gss_add_oid_set_member(&min_status,
134 &supported_mechs[i]->oid, oidset);
135 i++;
136 }
137
138 gss_release_oid_set(&min_status, &supported);
139 }
140
141
142 /* Wrapper around accept_sec_context
143 * Requires that the context contains:
144 * oid
145 * credentials (from ssh_gssapi_acquire_cred)
146 */
147 /* Privileged */
148 OM_uint32
ssh_gssapi_accept_ctx(Gssctxt * ctx,gss_buffer_desc * recv_tok,gss_buffer_desc * send_tok,OM_uint32 * flags)149 ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok,
150 gss_buffer_desc *send_tok, OM_uint32 *flags)
151 {
152 OM_uint32 status;
153 gss_OID mech;
154
155 ctx->major = gss_accept_sec_context(&ctx->minor,
156 &ctx->context, ctx->creds, recv_tok,
157 GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech,
158 send_tok, flags, NULL, &ctx->client_creds);
159
160 if (GSS_ERROR(ctx->major))
161 ssh_gssapi_error(ctx);
162
163 if (ctx->client_creds)
164 debug("Received some client credentials");
165 else
166 debug("Got no client credentials");
167
168 status = ctx->major;
169
170 /* Now, if we're complete and we have the right flags, then
171 * we flag the user as also having been authenticated
172 */
173
174 if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
175 (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) {
176 if (ssh_gssapi_getclient(ctx, &gssapi_client))
177 fatal("Couldn't convert client name");
178 }
179
180 return (status);
181 }
182
183 /*
184 * This parses an exported name, extracting the mechanism specific portion
185 * to use for ACL checking. It verifies that the name belongs the mechanism
186 * originally selected.
187 */
188 static OM_uint32
ssh_gssapi_parse_ename(Gssctxt * ctx,gss_buffer_t ename,gss_buffer_t name)189 ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name)
190 {
191 u_char *tok;
192 OM_uint32 offset;
193 OM_uint32 oidl;
194
195 tok = ename->value;
196
197 /*
198 * Check that ename is long enough for all of the fixed length
199 * header, and that the initial ID bytes are correct
200 */
201
202 if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0)
203 return GSS_S_FAILURE;
204
205 /*
206 * Extract the OID, and check it. Here GSSAPI breaks with tradition
207 * and does use the OID type and length bytes. To confuse things
208 * there are two lengths - the first including these, and the
209 * second without.
210 */
211
212 oidl = get_u16(tok+2); /* length including next two bytes */
213 oidl = oidl-2; /* turn it into the _real_ length of the variable OID */
214
215 /*
216 * Check the BER encoding for correct type and length, that the
217 * string is long enough and that the OID matches that in our context
218 */
219 if (tok[4] != 0x06 || tok[5] != oidl ||
220 ename->length < oidl+6 ||
221 !ssh_gssapi_check_oid(ctx, tok+6, oidl))
222 return GSS_S_FAILURE;
223
224 offset = oidl+6;
225
226 if (ename->length < offset+4)
227 return GSS_S_FAILURE;
228
229 name->length = get_u32(tok+offset);
230 offset += 4;
231
232 if (UINT_MAX - offset < name->length)
233 return GSS_S_FAILURE;
234 if (ename->length < offset+name->length)
235 return GSS_S_FAILURE;
236
237 name->value = xmalloc(name->length+1);
238 memcpy(name->value, tok+offset, name->length);
239 ((char *)name->value)[name->length] = 0;
240
241 return GSS_S_COMPLETE;
242 }
243
244 /* Extract the client details from a given context. This can only reliably
245 * be called once for a context */
246
247 /* Privileged (called from accept_secure_ctx) */
248 OM_uint32
ssh_gssapi_getclient(Gssctxt * ctx,ssh_gssapi_client * client)249 ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
250 {
251 int i = 0;
252
253 gss_buffer_desc ename;
254
255 client->mech = NULL;
256
257 while (supported_mechs[i]->name != NULL) {
258 if (supported_mechs[i]->oid.length == ctx->oid->length &&
259 (memcmp(supported_mechs[i]->oid.elements,
260 ctx->oid->elements, ctx->oid->length) == 0))
261 client->mech = supported_mechs[i];
262 i++;
263 }
264
265 if (client->mech == NULL)
266 return GSS_S_FAILURE;
267
268 if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
269 &client->displayname, NULL))) {
270 ssh_gssapi_error(ctx);
271 return (ctx->major);
272 }
273
274 if ((ctx->major = gss_export_name(&ctx->minor, ctx->client,
275 &ename))) {
276 ssh_gssapi_error(ctx);
277 return (ctx->major);
278 }
279
280 if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename,
281 &client->exportedname))) {
282 return (ctx->major);
283 }
284
285 /* We can't copy this structure, so we just move the pointer to it */
286 client->creds = ctx->client_creds;
287 ctx->client_creds = GSS_C_NO_CREDENTIAL;
288 return (ctx->major);
289 }
290
291 /* As user - called on fatal/exit */
292 void
ssh_gssapi_cleanup_creds(void)293 ssh_gssapi_cleanup_creds(void)
294 {
295 if (gssapi_client.store.filename != NULL) {
296 /* Unlink probably isn't sufficient */
297 debug("removing gssapi cred file\"%s\"",
298 gssapi_client.store.filename);
299 unlink(gssapi_client.store.filename);
300 }
301 }
302
303 /* As user */
304 void
ssh_gssapi_storecreds(void)305 ssh_gssapi_storecreds(void)
306 {
307 if (gssapi_client.mech && gssapi_client.mech->storecreds) {
308 (*gssapi_client.mech->storecreds)(&gssapi_client);
309 } else
310 debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism");
311 }
312
313 /* This allows GSSAPI methods to do things to the childs environment based
314 * on the passed authentication process and credentials.
315 */
316 /* As user */
317 void
ssh_gssapi_do_child(char *** envp,u_int * envsizep)318 ssh_gssapi_do_child(char ***envp, u_int *envsizep)
319 {
320
321 if (gssapi_client.store.envvar != NULL &&
322 gssapi_client.store.envval != NULL) {
323 debug("Setting %s to %s", gssapi_client.store.envvar,
324 gssapi_client.store.envval);
325 child_set_env(envp, envsizep, gssapi_client.store.envvar,
326 gssapi_client.store.envval);
327 }
328 }
329
330 /* Privileged */
331 int
ssh_gssapi_userok(char * user)332 ssh_gssapi_userok(char *user)
333 {
334 OM_uint32 lmin;
335
336 if (gssapi_client.exportedname.length == 0 ||
337 gssapi_client.exportedname.value == NULL) {
338 debug("No suitable client data");
339 return 0;
340 }
341 if (gssapi_client.mech && gssapi_client.mech->userok)
342 if ((*gssapi_client.mech->userok)(&gssapi_client, user))
343 return 1;
344 else {
345 /* Destroy delegated credentials if userok fails */
346 gss_release_buffer(&lmin, &gssapi_client.displayname);
347 gss_release_buffer(&lmin, &gssapi_client.exportedname);
348 gss_release_cred(&lmin, &gssapi_client.creds);
349 memset(&gssapi_client, 0, sizeof(ssh_gssapi_client));
350 return 0;
351 }
352 else
353 debug("ssh_gssapi_userok: Unknown GSSAPI mechanism");
354 return (0);
355 }
356
357 /* Privileged */
358 OM_uint32
ssh_gssapi_checkmic(Gssctxt * ctx,gss_buffer_t gssbuf,gss_buffer_t gssmic)359 ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
360 {
361 ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
362 gssbuf, gssmic, NULL);
363
364 return (ctx->major);
365 }
366
367 #endif
368