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1 | /* $OpenBSD: auth2-gss.c,v 1.16 2007/10/29 00:52:45 dtucker 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 | ||
33 | #include <stdarg.h> | |
34 | ||
35 | #include "xmalloc.h" | |
36 | #include "key.h" | |
37 | #include "hostfile.h" | |
38 | #include "auth.h" | |
39 | #include "ssh2.h" | |
40 | #include "log.h" | |
41 | #include "dispatch.h" | |
42 | #include "buffer.h" | |
43 | #include "servconf.h" | |
44 | #include "packet.h" | |
45 | #include "ssh-gss.h" | |
46 | #include "monitor_wrap.h" | |
47 | ||
48 | extern ServerOptions options; | |
49 | ||
50 | static void input_gssapi_token(int type, u_int32_t plen, void *ctxt); | |
51 | static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt); | |
52 | static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt); | |
53 | static void input_gssapi_errtok(int, u_int32_t, void *); | |
54 | ||
55 | /* | |
56 | * We only support those mechanisms that we know about (ie ones that we know | |
57 | * how to check local user kuserok and the like) | |
58 | */ | |
59 | static int | |
60 | userauth_gssapi(Authctxt *authctxt) | |
61 | { | |
62 | gss_OID_desc goid = {0, NULL}; | |
63 | Gssctxt *ctxt = NULL; | |
64 | int mechs; | |
65 | gss_OID_set supported; | |
66 | int present; | |
67 | OM_uint32 ms; | |
68 | u_int len; | |
69 | u_char *doid = NULL; | |
70 | ||
71 | if (!authctxt->valid || authctxt->user == NULL) | |
72 | return (0); | |
73 | ||
74 | mechs = packet_get_int(); | |
75 | if (mechs == 0) { | |
76 | debug("Mechanism negotiation is not supported"); | |
77 | return (0); | |
78 | } | |
79 | ||
80 | ssh_gssapi_supported_oids(&supported); | |
81 | do { | |
82 | mechs--; | |
83 | ||
84 | if (doid) | |
85 | xfree(doid); | |
86 | ||
87 | present = 0; | |
88 | doid = packet_get_string(&len); | |
89 | ||
90 | if (len > 2 && doid[0] == SSH_GSS_OIDTYPE && | |
91 | doid[1] == len - 2) { | |
92 | goid.elements = doid + 2; | |
93 | goid.length = len - 2; | |
94 | gss_test_oid_set_member(&ms, &goid, supported, | |
95 | &present); | |
96 | } else { | |
97 | logit("Badly formed OID received"); | |
98 | } | |
99 | } while (mechs > 0 && !present); | |
100 | ||
101 | gss_release_oid_set(&ms, &supported); | |
102 | ||
103 | if (!present) { | |
104 | xfree(doid); | |
105 | return (0); | |
106 | } | |
107 | ||
108 | if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) { | |
109 | if (ctxt != NULL) | |
110 | ssh_gssapi_delete_ctx(&ctxt); | |
111 | xfree(doid); | |
112 | return (0); | |
113 | } | |
114 | ||
115 | authctxt->methoddata = (void *)ctxt; | |
116 | ||
117 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE); | |
118 | ||
119 | /* Return the OID that we received */ | |
120 | packet_put_string(doid, len); | |
121 | ||
122 | packet_send(); | |
123 | xfree(doid); | |
124 | ||
125 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token); | |
126 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok); | |
127 | authctxt->postponed = 1; | |
128 | ||
129 | return (0); | |
130 | } | |
131 | ||
132 | static void | |
133 | input_gssapi_token(int type, u_int32_t plen, void *ctxt) | |
134 | { | |
135 | Authctxt *authctxt = ctxt; | |
136 | Gssctxt *gssctxt; | |
137 | gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; | |
138 | gss_buffer_desc recv_tok; | |
139 | OM_uint32 maj_status, min_status, flags; | |
140 | u_int len; | |
141 | ||
142 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
143 | fatal("No authentication or GSSAPI context"); | |
144 | ||
145 | gssctxt = authctxt->methoddata; | |
146 | recv_tok.value = packet_get_string(&len); | |
147 | recv_tok.length = len; /* u_int vs. size_t */ | |
148 | ||
149 | packet_check_eom(); | |
150 | ||
151 | maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, | |
152 | &send_tok, &flags)); | |
153 | ||
154 | xfree(recv_tok.value); | |
155 | ||
156 | if (GSS_ERROR(maj_status)) { | |
157 | if (send_tok.length != 0) { | |
158 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK); | |
159 | packet_put_string(send_tok.value, send_tok.length); | |
160 | packet_send(); | |
161 | } | |
162 | authctxt->postponed = 0; | |
163 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
164 | userauth_finish(authctxt, 0, "gssapi-with-mic"); | |
165 | } else { | |
166 | if (send_tok.length != 0) { | |
167 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN); | |
168 | packet_put_string(send_tok.value, send_tok.length); | |
169 | packet_send(); | |
170 | } | |
171 | if (maj_status == GSS_S_COMPLETE) { | |
172 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
173 | if (flags & GSS_C_INTEG_FLAG) | |
174 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, | |
175 | &input_gssapi_mic); | |
176 | else | |
177 | dispatch_set( | |
178 | SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, | |
179 | &input_gssapi_exchange_complete); | |
180 | } | |
181 | } | |
182 | ||
183 | gss_release_buffer(&min_status, &send_tok); | |
184 | } | |
185 | ||
186 | static void | |
187 | input_gssapi_errtok(int type, u_int32_t plen, void *ctxt) | |
188 | { | |
189 | Authctxt *authctxt = ctxt; | |
190 | Gssctxt *gssctxt; | |
191 | gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; | |
192 | gss_buffer_desc recv_tok; | |
193 | OM_uint32 maj_status; | |
194 | u_int len; | |
195 | ||
196 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
197 | fatal("No authentication or GSSAPI context"); | |
198 | ||
199 | gssctxt = authctxt->methoddata; | |
200 | recv_tok.value = packet_get_string(&len); | |
201 | recv_tok.length = len; | |
202 | ||
203 | packet_check_eom(); | |
204 | ||
205 | /* Push the error token into GSSAPI to see what it says */ | |
206 | maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, | |
207 | &send_tok, NULL)); | |
208 | ||
209 | xfree(recv_tok.value); | |
210 | ||
211 | /* We can't return anything to the client, even if we wanted to */ | |
212 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
213 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); | |
214 | ||
215 | /* The client will have already moved on to the next auth */ | |
216 | ||
217 | gss_release_buffer(&maj_status, &send_tok); | |
218 | } | |
219 | ||
220 | /* | |
221 | * This is called when the client thinks we've completed authentication. | |
222 | * It should only be enabled in the dispatch handler by the function above, | |
223 | * which only enables it once the GSSAPI exchange is complete. | |
224 | */ | |
225 | ||
226 | static void | |
227 | input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt) | |
228 | { | |
229 | Authctxt *authctxt = ctxt; | |
230 | Gssctxt *gssctxt; | |
231 | int authenticated; | |
232 | ||
233 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
234 | fatal("No authentication or GSSAPI context"); | |
235 | ||
236 | gssctxt = authctxt->methoddata; | |
237 | ||
238 | /* | |
239 | * We don't need to check the status, because we're only enabled in | |
240 | * the dispatcher once the exchange is complete | |
241 | */ | |
242 | ||
243 | packet_check_eom(); | |
244 | ||
245 | authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); | |
246 | ||
247 | authctxt->postponed = 0; | |
248 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
249 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); | |
250 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); | |
251 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); | |
252 | userauth_finish(authctxt, authenticated, "gssapi-with-mic"); | |
253 | } | |
254 | ||
255 | static void | |
256 | input_gssapi_mic(int type, u_int32_t plen, void *ctxt) | |
257 | { | |
258 | Authctxt *authctxt = ctxt; | |
259 | Gssctxt *gssctxt; | |
260 | int authenticated = 0; | |
261 | Buffer b; | |
262 | gss_buffer_desc mic, gssbuf; | |
263 | u_int len; | |
264 | ||
265 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
266 | fatal("No authentication or GSSAPI context"); | |
267 | ||
268 | gssctxt = authctxt->methoddata; | |
269 | ||
270 | mic.value = packet_get_string(&len); | |
271 | mic.length = len; | |
272 | ||
273 | ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service, | |
274 | "gssapi-with-mic"); | |
275 | ||
276 | gssbuf.value = buffer_ptr(&b); | |
277 | gssbuf.length = buffer_len(&b); | |
278 | ||
279 | if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) | |
280 | authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); | |
281 | else | |
282 | logit("GSSAPI MIC check failed"); | |
283 | ||
284 | buffer_free(&b); | |
285 | xfree(mic.value); | |
286 | ||
287 | authctxt->postponed = 0; | |
288 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
289 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); | |
290 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); | |
291 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); | |
292 | userauth_finish(authctxt, authenticated, "gssapi-with-mic"); | |
293 | } | |
294 | ||
295 | Authmethod method_gssapi = { | |
296 | "gssapi-with-mic", | |
297 | userauth_gssapi, | |
298 | &options.gss_authentication | |
299 | }; | |
300 | ||
301 | #endif /* GSSAPI */ |