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1/* $OpenBSD: gss-serv.c,v 1.3 2003/08/31 13:31:57 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 "bufaux.h"
32#include "compat.h"
33#include "auth.h"
34#include "log.h"
35#include "channels.h"
36#include "session.h"
37#include "servconf.h"
38#include "monitor_wrap.h"
39#include "xmalloc.h"
40#include "getput.h"
41
42#include "ssh-gss.h"
43
44extern ServerOptions options;
45
46static ssh_gssapi_client gssapi_client =
47 { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
48 GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL}};
49
50ssh_gssapi_mech gssapi_null_mech =
51 { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
52
53#ifdef KRB5
54extern ssh_gssapi_mech gssapi_kerberos_mech;
55#endif
56
57ssh_gssapi_mech* supported_mechs[]= {
58#ifdef KRB5
59 &gssapi_kerberos_mech,
60#endif
61 &gssapi_null_mech,
62};
63
64/* Unpriviledged */
65void
66ssh_gssapi_supported_oids(gss_OID_set *oidset)
67{
68 int i = 0;
69 OM_uint32 min_status;
70 int present;
71 gss_OID_set supported;
72
73 gss_create_empty_oid_set(&min_status, oidset);
74 gss_indicate_mechs(&min_status, &supported);
75
76 while (supported_mechs[i]->name != NULL) {
77 if (GSS_ERROR(gss_test_oid_set_member(&min_status,
78 &supported_mechs[i]->oid, supported, &present)))
79 present = 0;
80 if (present)
81 gss_add_oid_set_member(&min_status,
82 &supported_mechs[i]->oid, oidset);
83 i++;
84 }
85}
86
87
88/* Wrapper around accept_sec_context
89 * Requires that the context contains:
90 * oid
91 * credentials (from ssh_gssapi_acquire_cred)
92 */
93/* Priviledged */
94OM_uint32
95ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok,
96 gss_buffer_desc *send_tok, OM_uint32 *flags)
97{
98 OM_uint32 status;
99 gss_OID mech;
100
101 ctx->major = gss_accept_sec_context(&ctx->minor,
102 &ctx->context, ctx->creds, recv_tok,
103 GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech,
104 send_tok, flags, NULL, &ctx->client_creds);
105
106 if (GSS_ERROR(ctx->major))
107 ssh_gssapi_error(ctx);
108
109 if (ctx->client_creds)
110 debug("Received some client credentials");
111 else
112 debug("Got no client credentials");
113
114 status = ctx->major;
115
116 /* Now, if we're complete and we have the right flags, then
117 * we flag the user as also having been authenticated
118 */
119
120 if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
121 (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) {
122 if (ssh_gssapi_getclient(ctx, &gssapi_client))
123 fatal("Couldn't convert client name");
124 }
125
126 return (status);
127}
128
129/*
130 * This parses an exported name, extracting the mechanism specific portion
131 * to use for ACL checking. It verifies that the name belongs the mechanism
132 * originally selected.
133 */
134static OM_uint32
135ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name)
136{
137 char *tok;
138 OM_uint32 offset;
139 OM_uint32 oidl;
140
141 tok=ename->value;
142
143 /*
144 * Check that ename is long enough for all of the fixed length
145 * header, and that the initial ID bytes are correct
146 */
147
148 if (ename->length<6 || memcmp(tok,"\x04\x01", 2)!=0)
149 return GSS_S_FAILURE;
150
151 /*
152 * Extract the OID, and check it. Here GSSAPI breaks with tradition
153 * and does use the OID type and length bytes. To confuse things
154 * there are two lengths - the first including these, and the
155 * second without.
156 */
157
158 oidl = GET_16BIT(tok+2); /* length including next two bytes */
159 oidl = oidl-2; /* turn it into the _real_ length of the variable OID */
160
161 /*
162 * Check the BER encoding for correct type and length, that the
163 * string is long enough and that the OID matches that in our context
164 */
165 if (tok[4] != 0x06 || tok[5] != oidl ||
166 ename->length < oidl+6 ||
167 !ssh_gssapi_check_oid(ctx,tok+6,oidl))
168 return GSS_S_FAILURE;
169
170 offset = oidl+6;
171
172 if (ename->length < offset+4)
173 return GSS_S_FAILURE;
174
175 name->length = GET_32BIT(tok+offset);
176 offset += 4;
177
178 if (ename->length < offset+name->length)
179 return GSS_S_FAILURE;
180
181 name->value = xmalloc(name->length+1);
182 memcpy(name->value,tok+offset,name->length);
183 ((char *)name->value)[name->length] = 0;
184
185 return GSS_S_COMPLETE;
186}
187
188/* Extract the client details from a given context. This can only reliably
189 * be called once for a context */
190
191/* Priviledged (called from accept_secure_ctx) */
192OM_uint32
193ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
194{
195 int i = 0;
196
197 gss_buffer_desc ename;
198
199 client->mech = NULL;
200
201 while (supported_mechs[i]->name != NULL) {
202 if (supported_mechs[i]->oid.length == ctx->oid->length &&
203 (memcmp(supported_mechs[i]->oid.elements,
204 ctx->oid->elements, ctx->oid->length) == 0))
205 client->mech = supported_mechs[i];
206 i++;
207 }
208
209 if (client->mech == NULL)
210 return GSS_S_FAILURE;
211
212 if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
213 &client->displayname, NULL))) {
214 ssh_gssapi_error(ctx);
215 return (ctx->major);
216 }
217
218 if ((ctx->major = gss_export_name(&ctx->minor, ctx->client,
219 &ename))) {
220 ssh_gssapi_error(ctx);
221 return (ctx->major);
222 }
223
224 if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename,
225 &client->exportedname))) {
226 return (ctx->major);
227 }
228
229 /* We can't copy this structure, so we just move the pointer to it */
230 client->creds = ctx->client_creds;
231 ctx->client_creds = GSS_C_NO_CREDENTIAL;
232 return (ctx->major);
233}
234
235/* As user - called through fatal cleanup hook */
236void
237ssh_gssapi_cleanup_creds(void *ignored)
238{
239 if (gssapi_client.store.filename != NULL) {
240 /* Unlink probably isn't sufficient */
241 debug("removing gssapi cred file\"%s\"", gssapi_client.store.filename);
242 unlink(gssapi_client.store.filename);
243 }
244}
245
246/* As user */
247void
248ssh_gssapi_storecreds(void)
249{
250 if (gssapi_client.mech && gssapi_client.mech->storecreds) {
251 (*gssapi_client.mech->storecreds)(&gssapi_client);
252 if (options.gss_cleanup_creds)
253 fatal_add_cleanup(ssh_gssapi_cleanup_creds, NULL);
254 } else
255 debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism");
256}
257
258/* This allows GSSAPI methods to do things to the childs environment based
259 * on the passed authentication process and credentials.
260 */
261/* As user */
262void
263ssh_gssapi_do_child(char ***envp, u_int *envsizep)
264{
265
266 if (gssapi_client.store.envvar != NULL &&
267 gssapi_client.store.envval != NULL) {
268
269 debug("Setting %s to %s", gssapi_client.store.envvar,
270 gssapi_client.store.envval);
271 child_set_env(envp, envsizep, gssapi_client.store.envvar,
272 gssapi_client.store.envval);
273 }
274}
275
276/* Priviledged */
277int
278ssh_gssapi_userok(char *user)
279{
280 if (gssapi_client.exportedname.length == 0 ||
281 gssapi_client.exportedname.value == NULL) {
282 debug("No suitable client data");
283 return 0;
284 }
285 if (gssapi_client.mech && gssapi_client.mech->userok)
286 return ((*gssapi_client.mech->userok)(&gssapi_client, user));
287 else
288 debug("ssh_gssapi_userok: Unknown GSSAPI mechanism");
289 return (0);
290}
291
292#endif