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1 | /* $OpenBSD: gss-serv.c,v 1.11 2005/10/13 14:20:37 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 "bufaux.h" | |
32 | #include "auth.h" | |
33 | #include "log.h" | |
34 | #include "channels.h" | |
35 | #include "session.h" | |
36 | #include "servconf.h" | |
37 | #include "xmalloc.h" | |
38 | #include "getput.h" | |
39 | ||
40 | #include "ssh-gss.h" | |
41 | ||
42 | extern ServerOptions options; | |
43 | ||
44 | static ssh_gssapi_client gssapi_client = | |
45 | { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER, | |
46 | GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL}}; | |
47 | ||
48 | ssh_gssapi_mech gssapi_null_mech = | |
49 | { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL}; | |
50 | ||
51 | #ifdef KRB5 | |
52 | extern ssh_gssapi_mech gssapi_kerberos_mech; | |
53 | #endif | |
54 | ||
55 | ssh_gssapi_mech* supported_mechs[]= { | |
56 | #ifdef KRB5 | |
57 | &gssapi_kerberos_mech, | |
58 | #endif | |
59 | &gssapi_null_mech, | |
60 | }; | |
61 | ||
62 | /* Unprivileged */ | |
63 | void | |
64 | ssh_gssapi_supported_oids(gss_OID_set *oidset) | |
65 | { | |
66 | int i = 0; | |
67 | OM_uint32 min_status; | |
68 | int present; | |
69 | gss_OID_set supported; | |
70 | ||
71 | gss_create_empty_oid_set(&min_status, oidset); | |
72 | gss_indicate_mechs(&min_status, &supported); | |
73 | ||
74 | while (supported_mechs[i]->name != NULL) { | |
75 | if (GSS_ERROR(gss_test_oid_set_member(&min_status, | |
76 | &supported_mechs[i]->oid, supported, &present))) | |
77 | present = 0; | |
78 | if (present) | |
79 | gss_add_oid_set_member(&min_status, | |
80 | &supported_mechs[i]->oid, oidset); | |
81 | i++; | |
82 | } | |
83 | } | |
84 | ||
85 | ||
86 | /* Wrapper around accept_sec_context | |
87 | * Requires that the context contains: | |
88 | * oid | |
89 | * credentials (from ssh_gssapi_acquire_cred) | |
90 | */ | |
91 | /* Privileged */ | |
92 | OM_uint32 | |
93 | ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok, | |
94 | gss_buffer_desc *send_tok, OM_uint32 *flags) | |
95 | { | |
96 | OM_uint32 status; | |
97 | gss_OID mech; | |
98 | ||
99 | ctx->major = gss_accept_sec_context(&ctx->minor, | |
100 | &ctx->context, ctx->creds, recv_tok, | |
101 | GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech, | |
102 | send_tok, flags, NULL, &ctx->client_creds); | |
103 | ||
104 | if (GSS_ERROR(ctx->major)) | |
105 | ssh_gssapi_error(ctx); | |
106 | ||
107 | if (ctx->client_creds) | |
108 | debug("Received some client credentials"); | |
109 | else | |
110 | debug("Got no client credentials"); | |
111 | ||
112 | status = ctx->major; | |
113 | ||
114 | /* Now, if we're complete and we have the right flags, then | |
115 | * we flag the user as also having been authenticated | |
116 | */ | |
117 | ||
118 | if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) && | |
119 | (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) { | |
120 | if (ssh_gssapi_getclient(ctx, &gssapi_client)) | |
121 | fatal("Couldn't convert client name"); | |
122 | } | |
123 | ||
124 | return (status); | |
125 | } | |
126 | ||
127 | /* | |
128 | * This parses an exported name, extracting the mechanism specific portion | |
129 | * to use for ACL checking. It verifies that the name belongs the mechanism | |
130 | * originally selected. | |
131 | */ | |
132 | static OM_uint32 | |
133 | ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name) | |
134 | { | |
135 | u_char *tok; | |
136 | OM_uint32 offset; | |
137 | OM_uint32 oidl; | |
138 | ||
139 | tok=ename->value; | |
140 | ||
141 | /* | |
142 | * Check that ename is long enough for all of the fixed length | |
143 | * header, and that the initial ID bytes are correct | |
144 | */ | |
145 | ||
146 | if (ename->length<6 || memcmp(tok,"\x04\x01", 2)!=0) | |
147 | return GSS_S_FAILURE; | |
148 | ||
149 | /* | |
150 | * Extract the OID, and check it. Here GSSAPI breaks with tradition | |
151 | * and does use the OID type and length bytes. To confuse things | |
152 | * there are two lengths - the first including these, and the | |
153 | * second without. | |
154 | */ | |
155 | ||
156 | oidl = GET_16BIT(tok+2); /* length including next two bytes */ | |
157 | oidl = oidl-2; /* turn it into the _real_ length of the variable OID */ | |
158 | ||
159 | /* | |
160 | * Check the BER encoding for correct type and length, that the | |
161 | * string is long enough and that the OID matches that in our context | |
162 | */ | |
163 | if (tok[4] != 0x06 || tok[5] != oidl || | |
164 | ename->length < oidl+6 || | |
165 | !ssh_gssapi_check_oid(ctx,tok+6,oidl)) | |
166 | return GSS_S_FAILURE; | |
167 | ||
168 | offset = oidl+6; | |
169 | ||
170 | if (ename->length < offset+4) | |
171 | return GSS_S_FAILURE; | |
172 | ||
173 | name->length = GET_32BIT(tok+offset); | |
174 | offset += 4; | |
175 | ||
176 | if (ename->length < offset+name->length) | |
177 | return GSS_S_FAILURE; | |
178 | ||
179 | name->value = xmalloc(name->length+1); | |
180 | memcpy(name->value,tok+offset,name->length); | |
181 | ((char *)name->value)[name->length] = 0; | |
182 | ||
183 | return GSS_S_COMPLETE; | |
184 | } | |
185 | ||
186 | /* Extract the client details from a given context. This can only reliably | |
187 | * be called once for a context */ | |
188 | ||
189 | /* Privileged (called from accept_secure_ctx) */ | |
190 | OM_uint32 | |
191 | ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client) | |
192 | { | |
193 | int i = 0; | |
194 | ||
195 | gss_buffer_desc ename; | |
196 | ||
197 | client->mech = NULL; | |
198 | ||
199 | while (supported_mechs[i]->name != NULL) { | |
200 | if (supported_mechs[i]->oid.length == ctx->oid->length && | |
201 | (memcmp(supported_mechs[i]->oid.elements, | |
202 | ctx->oid->elements, ctx->oid->length) == 0)) | |
203 | client->mech = supported_mechs[i]; | |
204 | i++; | |
205 | } | |
206 | ||
207 | if (client->mech == NULL) | |
208 | return GSS_S_FAILURE; | |
209 | ||
210 | if ((ctx->major = gss_display_name(&ctx->minor, ctx->client, | |
211 | &client->displayname, NULL))) { | |
212 | ssh_gssapi_error(ctx); | |
213 | return (ctx->major); | |
214 | } | |
215 | ||
216 | if ((ctx->major = gss_export_name(&ctx->minor, ctx->client, | |
217 | &ename))) { | |
218 | ssh_gssapi_error(ctx); | |
219 | return (ctx->major); | |
220 | } | |
221 | ||
222 | if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename, | |
223 | &client->exportedname))) { | |
224 | return (ctx->major); | |
225 | } | |
226 | ||
227 | /* We can't copy this structure, so we just move the pointer to it */ | |
228 | client->creds = ctx->client_creds; | |
229 | ctx->client_creds = GSS_C_NO_CREDENTIAL; | |
230 | return (ctx->major); | |
231 | } | |
232 | ||
233 | /* As user - called on fatal/exit */ | |
234 | void | |
235 | ssh_gssapi_cleanup_creds(void) | |
236 | { | |
237 | if (gssapi_client.store.filename != NULL) { | |
238 | /* Unlink probably isn't sufficient */ | |
239 | debug("removing gssapi cred file\"%s\"", gssapi_client.store.filename); | |
240 | unlink(gssapi_client.store.filename); | |
241 | } | |
242 | } | |
243 | ||
244 | /* As user */ | |
245 | void | |
246 | ssh_gssapi_storecreds(void) | |
247 | { | |
248 | if (gssapi_client.mech && gssapi_client.mech->storecreds) { | |
249 | (*gssapi_client.mech->storecreds)(&gssapi_client); | |
250 | } else | |
251 | debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism"); | |
252 | } | |
253 | ||
254 | /* This allows GSSAPI methods to do things to the childs environment based | |
255 | * on the passed authentication process and credentials. | |
256 | */ | |
257 | /* As user */ | |
258 | void | |
259 | ssh_gssapi_do_child(char ***envp, u_int *envsizep) | |
260 | { | |
261 | ||
262 | if (gssapi_client.store.envvar != NULL && | |
263 | gssapi_client.store.envval != NULL) { | |
264 | ||
265 | debug("Setting %s to %s", gssapi_client.store.envvar, | |
266 | gssapi_client.store.envval); | |
267 | child_set_env(envp, envsizep, gssapi_client.store.envvar, | |
268 | gssapi_client.store.envval); | |
269 | } | |
270 | } | |
271 | ||
272 | /* Privileged */ | |
273 | int | |
274 | ssh_gssapi_userok(char *user) | |
275 | { | |
276 | OM_uint32 lmin; | |
277 | ||
278 | if (gssapi_client.exportedname.length == 0 || | |
279 | gssapi_client.exportedname.value == NULL) { | |
280 | debug("No suitable client data"); | |
281 | return 0; | |
282 | } | |
283 | if (gssapi_client.mech && gssapi_client.mech->userok) | |
284 | if ((*gssapi_client.mech->userok)(&gssapi_client, user)) | |
285 | return 1; | |
286 | else { | |
287 | /* Destroy delegated credentials if userok fails */ | |
288 | gss_release_buffer(&lmin, &gssapi_client.displayname); | |
289 | gss_release_buffer(&lmin, &gssapi_client.exportedname); | |
290 | gss_release_cred(&lmin, &gssapi_client.creds); | |
291 | memset(&gssapi_client, 0, sizeof(ssh_gssapi_client)); | |
292 | return 0; | |
293 | } | |
294 | else | |
295 | debug("ssh_gssapi_userok: Unknown GSSAPI mechanism"); | |
296 | return (0); | |
297 | } | |
298 | ||
299 | /* Privileged */ | |
300 | OM_uint32 | |
301 | ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic) | |
302 | { | |
303 | ctx->major = gss_verify_mic(&ctx->minor, ctx->context, | |
304 | gssbuf, gssmic, NULL); | |
305 | ||
306 | return (ctx->major); | |
307 | } | |
308 | ||
309 | #endif |