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1 | /* $OpenBSD: gss-serv.c,v 1.22 2008/05/08 12:02:23 djm 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 | |
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 | |
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 | |
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 | |
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 | |
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 (ename->length < offset+name->length) | |
233 | return GSS_S_FAILURE; | |
234 | ||
235 | name->value = xmalloc(name->length+1); | |
236 | memcpy(name->value, tok+offset, name->length); | |
237 | ((char *)name->value)[name->length] = 0; | |
238 | ||
239 | return GSS_S_COMPLETE; | |
240 | } | |
241 | ||
242 | /* Extract the client details from a given context. This can only reliably | |
243 | * be called once for a context */ | |
244 | ||
245 | /* Privileged (called from accept_secure_ctx) */ | |
246 | OM_uint32 | |
247 | ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client) | |
248 | { | |
249 | int i = 0; | |
250 | ||
251 | gss_buffer_desc ename; | |
252 | ||
253 | client->mech = NULL; | |
254 | ||
255 | while (supported_mechs[i]->name != NULL) { | |
256 | if (supported_mechs[i]->oid.length == ctx->oid->length && | |
257 | (memcmp(supported_mechs[i]->oid.elements, | |
258 | ctx->oid->elements, ctx->oid->length) == 0)) | |
259 | client->mech = supported_mechs[i]; | |
260 | i++; | |
261 | } | |
262 | ||
263 | if (client->mech == NULL) | |
264 | return GSS_S_FAILURE; | |
265 | ||
266 | if ((ctx->major = gss_display_name(&ctx->minor, ctx->client, | |
267 | &client->displayname, NULL))) { | |
268 | ssh_gssapi_error(ctx); | |
269 | return (ctx->major); | |
270 | } | |
271 | ||
272 | if ((ctx->major = gss_export_name(&ctx->minor, ctx->client, | |
273 | &ename))) { | |
274 | ssh_gssapi_error(ctx); | |
275 | return (ctx->major); | |
276 | } | |
277 | ||
278 | if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename, | |
279 | &client->exportedname))) { | |
280 | return (ctx->major); | |
281 | } | |
282 | ||
283 | /* We can't copy this structure, so we just move the pointer to it */ | |
284 | client->creds = ctx->client_creds; | |
285 | ctx->client_creds = GSS_C_NO_CREDENTIAL; | |
286 | return (ctx->major); | |
287 | } | |
288 | ||
289 | /* As user - called on fatal/exit */ | |
290 | void | |
291 | ssh_gssapi_cleanup_creds(void) | |
292 | { | |
293 | if (gssapi_client.store.filename != NULL) { | |
294 | /* Unlink probably isn't sufficient */ | |
295 | debug("removing gssapi cred file\"%s\"", | |
296 | gssapi_client.store.filename); | |
297 | unlink(gssapi_client.store.filename); | |
298 | } | |
299 | } | |
300 | ||
301 | /* As user */ | |
302 | void | |
303 | ssh_gssapi_storecreds(void) | |
304 | { | |
305 | if (gssapi_client.mech && gssapi_client.mech->storecreds) { | |
306 | (*gssapi_client.mech->storecreds)(&gssapi_client); | |
307 | } else | |
308 | debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism"); | |
309 | } | |
310 | ||
311 | /* This allows GSSAPI methods to do things to the childs environment based | |
312 | * on the passed authentication process and credentials. | |
313 | */ | |
314 | /* As user */ | |
315 | void | |
316 | ssh_gssapi_do_child(char ***envp, u_int *envsizep) | |
317 | { | |
318 | ||
319 | if (gssapi_client.store.envvar != NULL && | |
320 | gssapi_client.store.envval != NULL) { | |
321 | debug("Setting %s to %s", gssapi_client.store.envvar, | |
322 | gssapi_client.store.envval); | |
323 | child_set_env(envp, envsizep, gssapi_client.store.envvar, | |
324 | gssapi_client.store.envval); | |
325 | } | |
326 | } | |
327 | ||
328 | /* Privileged */ | |
329 | int | |
330 | ssh_gssapi_userok(char *user) | |
331 | { | |
332 | OM_uint32 lmin; | |
333 | ||
334 | if (gssapi_client.exportedname.length == 0 || | |
335 | gssapi_client.exportedname.value == NULL) { | |
336 | debug("No suitable client data"); | |
337 | return 0; | |
338 | } | |
339 | if (gssapi_client.mech && gssapi_client.mech->userok) | |
340 | if ((*gssapi_client.mech->userok)(&gssapi_client, user)) | |
341 | return 1; | |
342 | else { | |
343 | /* Destroy delegated credentials if userok fails */ | |
344 | gss_release_buffer(&lmin, &gssapi_client.displayname); | |
345 | gss_release_buffer(&lmin, &gssapi_client.exportedname); | |
346 | gss_release_cred(&lmin, &gssapi_client.creds); | |
347 | memset(&gssapi_client, 0, sizeof(ssh_gssapi_client)); | |
348 | return 0; | |
349 | } | |
350 | else | |
351 | debug("ssh_gssapi_userok: Unknown GSSAPI mechanism"); | |
352 | return (0); | |
353 | } | |
354 | ||
355 | /* Privileged */ | |
356 | OM_uint32 | |
357 | ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic) | |
358 | { | |
359 | ctx->major = gss_verify_mic(&ctx->minor, ctx->context, | |
360 | gssbuf, gssmic, NULL); | |
361 | ||
362 | return (ctx->major); | |
363 | } | |
364 | ||
365 | #endif |