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1 | /* $OpenBSD: auth2-gss.c,v 1.12 2005/10/13 22:24:31 stevesk 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 "auth.h" | |
32 | #include "ssh2.h" | |
33 | #include "xmalloc.h" | |
34 | #include "log.h" | |
35 | #include "dispatch.h" | |
36 | #include "servconf.h" | |
37 | #include "packet.h" | |
38 | #include "monitor_wrap.h" | |
39 | ||
40 | #include "ssh-gss.h" | |
41 | ||
42 | extern ServerOptions options; | |
43 | ||
44 | static void input_gssapi_token(int type, u_int32_t plen, void *ctxt); | |
45 | static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt); | |
46 | static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt); | |
47 | static void input_gssapi_errtok(int, u_int32_t, void *); | |
48 | ||
49 | /* | |
50 | * We only support those mechanisms that we know about (ie ones that we know | |
51 | * how to check local user kuserok and the like) | |
52 | */ | |
53 | static int | |
54 | userauth_gssapi(Authctxt *authctxt) | |
55 | { | |
56 | gss_OID_desc goid = {0, NULL}; | |
57 | Gssctxt *ctxt = NULL; | |
58 | int mechs; | |
59 | gss_OID_set supported; | |
60 | int present; | |
61 | OM_uint32 ms; | |
62 | u_int len; | |
63 | u_char *doid = NULL; | |
64 | ||
65 | if (!authctxt->valid || authctxt->user == NULL) | |
66 | return (0); | |
67 | ||
68 | mechs = packet_get_int(); | |
69 | if (mechs == 0) { | |
70 | debug("Mechanism negotiation is not supported"); | |
71 | return (0); | |
72 | } | |
73 | ||
74 | ssh_gssapi_supported_oids(&supported); | |
75 | do { | |
76 | mechs--; | |
77 | ||
78 | if (doid) | |
79 | xfree(doid); | |
80 | ||
81 | present = 0; | |
82 | doid = packet_get_string(&len); | |
83 | ||
84 | if (len > 2 && doid[0] == SSH_GSS_OIDTYPE && | |
85 | doid[1] == len - 2) { | |
86 | goid.elements = doid + 2; | |
87 | goid.length = len - 2; | |
88 | gss_test_oid_set_member(&ms, &goid, supported, | |
89 | &present); | |
90 | } else { | |
91 | logit("Badly formed OID received"); | |
92 | } | |
93 | } while (mechs > 0 && !present); | |
94 | ||
95 | gss_release_oid_set(&ms, &supported); | |
96 | ||
97 | if (!present) { | |
98 | xfree(doid); | |
99 | return (0); | |
100 | } | |
101 | ||
102 | if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) { | |
103 | xfree(doid); | |
104 | return (0); | |
105 | } | |
106 | ||
107 | authctxt->methoddata = (void *)ctxt; | |
108 | ||
109 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE); | |
110 | ||
111 | /* Return the OID that we received */ | |
112 | packet_put_string(doid, len); | |
113 | ||
114 | packet_send(); | |
115 | xfree(doid); | |
116 | ||
117 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token); | |
118 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok); | |
119 | authctxt->postponed = 1; | |
120 | ||
121 | return (0); | |
122 | } | |
123 | ||
124 | static void | |
125 | input_gssapi_token(int type, u_int32_t plen, void *ctxt) | |
126 | { | |
127 | Authctxt *authctxt = ctxt; | |
128 | Gssctxt *gssctxt; | |
129 | gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; | |
130 | gss_buffer_desc recv_tok; | |
131 | OM_uint32 maj_status, min_status, flags; | |
132 | u_int len; | |
133 | ||
134 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
135 | fatal("No authentication or GSSAPI context"); | |
136 | ||
137 | gssctxt = authctxt->methoddata; | |
138 | recv_tok.value = packet_get_string(&len); | |
139 | recv_tok.length = len; /* u_int vs. size_t */ | |
140 | ||
141 | packet_check_eom(); | |
142 | ||
143 | maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, | |
144 | &send_tok, &flags)); | |
145 | ||
146 | xfree(recv_tok.value); | |
147 | ||
148 | if (GSS_ERROR(maj_status)) { | |
149 | if (send_tok.length != 0) { | |
150 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK); | |
151 | packet_put_string(send_tok.value, send_tok.length); | |
152 | packet_send(); | |
153 | } | |
154 | authctxt->postponed = 0; | |
155 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
156 | userauth_finish(authctxt, 0, "gssapi-with-mic"); | |
157 | } else { | |
158 | if (send_tok.length != 0) { | |
159 | packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN); | |
160 | packet_put_string(send_tok.value, send_tok.length); | |
161 | packet_send(); | |
162 | } | |
163 | if (maj_status == GSS_S_COMPLETE) { | |
164 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
165 | if (flags & GSS_C_INTEG_FLAG) | |
166 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, | |
167 | &input_gssapi_mic); | |
168 | else | |
169 | dispatch_set( | |
170 | SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, | |
171 | &input_gssapi_exchange_complete); | |
172 | } | |
173 | } | |
174 | ||
175 | gss_release_buffer(&min_status, &send_tok); | |
176 | } | |
177 | ||
178 | static void | |
179 | input_gssapi_errtok(int type, u_int32_t plen, void *ctxt) | |
180 | { | |
181 | Authctxt *authctxt = ctxt; | |
182 | Gssctxt *gssctxt; | |
183 | gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; | |
184 | gss_buffer_desc recv_tok; | |
185 | OM_uint32 maj_status; | |
186 | u_int len; | |
187 | ||
188 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
189 | fatal("No authentication or GSSAPI context"); | |
190 | ||
191 | gssctxt = authctxt->methoddata; | |
192 | recv_tok.value = packet_get_string(&len); | |
193 | recv_tok.length = len; | |
194 | ||
195 | packet_check_eom(); | |
196 | ||
197 | /* Push the error token into GSSAPI to see what it says */ | |
198 | maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, | |
199 | &send_tok, NULL)); | |
200 | ||
201 | xfree(recv_tok.value); | |
202 | ||
203 | /* We can't return anything to the client, even if we wanted to */ | |
204 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
205 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); | |
206 | ||
207 | /* The client will have already moved on to the next auth */ | |
208 | ||
209 | gss_release_buffer(&maj_status, &send_tok); | |
210 | } | |
211 | ||
212 | /* | |
213 | * This is called when the client thinks we've completed authentication. | |
214 | * It should only be enabled in the dispatch handler by the function above, | |
215 | * which only enables it once the GSSAPI exchange is complete. | |
216 | */ | |
217 | ||
218 | static void | |
219 | input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt) | |
220 | { | |
221 | Authctxt *authctxt = ctxt; | |
222 | Gssctxt *gssctxt; | |
223 | int authenticated; | |
224 | ||
225 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
226 | fatal("No authentication or GSSAPI context"); | |
227 | ||
228 | gssctxt = authctxt->methoddata; | |
229 | ||
230 | /* | |
231 | * We don't need to check the status, because we're only enabled in | |
232 | * the dispatcher once the exchange is complete | |
233 | */ | |
234 | ||
235 | packet_check_eom(); | |
236 | ||
237 | authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); | |
238 | ||
239 | authctxt->postponed = 0; | |
240 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
241 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); | |
242 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); | |
243 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); | |
244 | userauth_finish(authctxt, authenticated, "gssapi-with-mic"); | |
245 | } | |
246 | ||
247 | static void | |
248 | input_gssapi_mic(int type, u_int32_t plen, void *ctxt) | |
249 | { | |
250 | Authctxt *authctxt = ctxt; | |
251 | Gssctxt *gssctxt; | |
252 | int authenticated = 0; | |
253 | Buffer b; | |
254 | gss_buffer_desc mic, gssbuf; | |
255 | u_int len; | |
256 | ||
257 | if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) | |
258 | fatal("No authentication or GSSAPI context"); | |
259 | ||
260 | gssctxt = authctxt->methoddata; | |
261 | ||
262 | mic.value = packet_get_string(&len); | |
263 | mic.length = len; | |
264 | ||
265 | ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service, | |
266 | "gssapi-with-mic"); | |
267 | ||
268 | gssbuf.value = buffer_ptr(&b); | |
269 | gssbuf.length = buffer_len(&b); | |
270 | ||
271 | if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) | |
272 | authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); | |
273 | else | |
274 | logit("GSSAPI MIC check failed"); | |
275 | ||
276 | buffer_free(&b); | |
277 | xfree(mic.value); | |
278 | ||
279 | authctxt->postponed = 0; | |
280 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
281 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); | |
282 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); | |
283 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); | |
284 | userauth_finish(authctxt, authenticated, "gssapi-with-mic"); | |
285 | } | |
286 | ||
287 | Authmethod method_gssapi = { | |
288 | "gssapi-with-mic", | |
289 | userauth_gssapi, | |
290 | &options.gss_authentication | |
291 | }; | |
292 | ||
293 | #endif /* GSSAPI */ |