1 /* $OpenBSD: gss-genr.c,v 1.23 2015/01/20 23:14:00 deraadt Exp $ */
2
3 /*
4 * Copyright (c) 2001-2007 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 <limits.h>
35 #include <stdarg.h>
36 #include <string.h>
37 #include <unistd.h>
38
39 #include "xmalloc.h"
40 #include "buffer.h"
41 #include "log.h"
42 #include "ssh2.h"
43
44 #include "ssh-gss.h"
45
46 extern u_char *session_id2;
47 extern u_int session_id2_len;
48
49 /* Check that the OID in a data stream matches that in the context */
50 int
ssh_gssapi_check_oid(Gssctxt * ctx,void * data,size_t len)51 ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
52 {
53 return (ctx != NULL && ctx->oid != GSS_C_NO_OID &&
54 ctx->oid->length == len &&
55 memcmp(ctx->oid->elements, data, len) == 0);
56 }
57
58 /* Set the contexts OID from a data stream */
59 void
ssh_gssapi_set_oid_data(Gssctxt * ctx,void * data,size_t len)60 ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len)
61 {
62 if (ctx->oid != GSS_C_NO_OID) {
63 free(ctx->oid->elements);
64 free(ctx->oid);
65 }
66 ctx->oid = xcalloc(1, sizeof(gss_OID_desc));
67 ctx->oid->length = len;
68 ctx->oid->elements = xmalloc(len);
69 memcpy(ctx->oid->elements, data, len);
70 }
71
72 /* Set the contexts OID */
73 void
ssh_gssapi_set_oid(Gssctxt * ctx,gss_OID oid)74 ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid)
75 {
76 ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length);
77 }
78
79 /* All this effort to report an error ... */
80 void
ssh_gssapi_error(Gssctxt * ctxt)81 ssh_gssapi_error(Gssctxt *ctxt)
82 {
83 char *s;
84
85 s = ssh_gssapi_last_error(ctxt, NULL, NULL);
86 debug("%s", s);
87 free(s);
88 }
89
90 char *
ssh_gssapi_last_error(Gssctxt * ctxt,OM_uint32 * major_status,OM_uint32 * minor_status)91 ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status,
92 OM_uint32 *minor_status)
93 {
94 OM_uint32 lmin;
95 gss_buffer_desc msg = GSS_C_EMPTY_BUFFER;
96 OM_uint32 ctx;
97 Buffer b;
98 char *ret;
99
100 buffer_init(&b);
101
102 if (major_status != NULL)
103 *major_status = ctxt->major;
104 if (minor_status != NULL)
105 *minor_status = ctxt->minor;
106
107 ctx = 0;
108 /* The GSSAPI error */
109 do {
110 gss_display_status(&lmin, ctxt->major,
111 GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg);
112
113 buffer_append(&b, msg.value, msg.length);
114 buffer_put_char(&b, '\n');
115
116 gss_release_buffer(&lmin, &msg);
117 } while (ctx != 0);
118
119 /* The mechanism specific error */
120 do {
121 gss_display_status(&lmin, ctxt->minor,
122 GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg);
123
124 buffer_append(&b, msg.value, msg.length);
125 buffer_put_char(&b, '\n');
126
127 gss_release_buffer(&lmin, &msg);
128 } while (ctx != 0);
129
130 buffer_put_char(&b, '\0');
131 ret = xmalloc(buffer_len(&b));
132 buffer_get(&b, ret, buffer_len(&b));
133 buffer_free(&b);
134 return (ret);
135 }
136
137 /*
138 * Initialise our GSSAPI context. We use this opaque structure to contain all
139 * of the data which both the client and server need to persist across
140 * {accept,init}_sec_context calls, so that when we do it from the userauth
141 * stuff life is a little easier
142 */
143 void
ssh_gssapi_build_ctx(Gssctxt ** ctx)144 ssh_gssapi_build_ctx(Gssctxt **ctx)
145 {
146 *ctx = xcalloc(1, sizeof (Gssctxt));
147 (*ctx)->context = GSS_C_NO_CONTEXT;
148 (*ctx)->name = GSS_C_NO_NAME;
149 (*ctx)->oid = GSS_C_NO_OID;
150 (*ctx)->creds = GSS_C_NO_CREDENTIAL;
151 (*ctx)->client = GSS_C_NO_NAME;
152 (*ctx)->client_creds = GSS_C_NO_CREDENTIAL;
153 }
154
155 /* Delete our context, providing it has been built correctly */
156 void
ssh_gssapi_delete_ctx(Gssctxt ** ctx)157 ssh_gssapi_delete_ctx(Gssctxt **ctx)
158 {
159 OM_uint32 ms;
160
161 if ((*ctx) == NULL)
162 return;
163 if ((*ctx)->context != GSS_C_NO_CONTEXT)
164 gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER);
165 if ((*ctx)->name != GSS_C_NO_NAME)
166 gss_release_name(&ms, &(*ctx)->name);
167 if ((*ctx)->oid != GSS_C_NO_OID) {
168 free((*ctx)->oid->elements);
169 free((*ctx)->oid);
170 (*ctx)->oid = GSS_C_NO_OID;
171 }
172 if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
173 gss_release_cred(&ms, &(*ctx)->creds);
174 if ((*ctx)->client != GSS_C_NO_NAME)
175 gss_release_name(&ms, &(*ctx)->client);
176 if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
177 gss_release_cred(&ms, &(*ctx)->client_creds);
178
179 free(*ctx);
180 *ctx = NULL;
181 }
182
183 /*
184 * Wrapper to init_sec_context
185 * Requires that the context contains:
186 * oid
187 * server name (from ssh_gssapi_import_name)
188 */
189 OM_uint32
ssh_gssapi_init_ctx(Gssctxt * ctx,int deleg_creds,gss_buffer_desc * recv_tok,gss_buffer_desc * send_tok,OM_uint32 * flags)190 ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
191 gss_buffer_desc* send_tok, OM_uint32 *flags)
192 {
193 int deleg_flag = 0;
194
195 if (deleg_creds) {
196 deleg_flag = GSS_C_DELEG_FLAG;
197 debug("Delegating credentials");
198 }
199
200 ctx->major = gss_init_sec_context(&ctx->minor,
201 GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid,
202 GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
203 0, NULL, recv_tok, NULL, send_tok, flags, NULL);
204
205 if (GSS_ERROR(ctx->major))
206 ssh_gssapi_error(ctx);
207
208 return (ctx->major);
209 }
210
211 /* Create a service name for the given host */
212 OM_uint32
ssh_gssapi_import_name(Gssctxt * ctx,const char * host)213 ssh_gssapi_import_name(Gssctxt *ctx, const char *host)
214 {
215 gss_buffer_desc gssbuf;
216 char *val;
217
218 xasprintf(&val, "host@%s", host);
219 gssbuf.value = val;
220 gssbuf.length = strlen(gssbuf.value);
221
222 if ((ctx->major = gss_import_name(&ctx->minor,
223 &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name)))
224 ssh_gssapi_error(ctx);
225
226 free(gssbuf.value);
227 return (ctx->major);
228 }
229
230 OM_uint32
ssh_gssapi_sign(Gssctxt * ctx,gss_buffer_t buffer,gss_buffer_t hash)231 ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
232 {
233 if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
234 GSS_C_QOP_DEFAULT, buffer, hash)))
235 ssh_gssapi_error(ctx);
236
237 return (ctx->major);
238 }
239
240 void
ssh_gssapi_buildmic(Buffer * b,const char * user,const char * service,const char * context)241 ssh_gssapi_buildmic(Buffer *b, const char *user, const char *service,
242 const char *context)
243 {
244 buffer_init(b);
245 buffer_put_string(b, session_id2, session_id2_len);
246 buffer_put_char(b, SSH2_MSG_USERAUTH_REQUEST);
247 buffer_put_cstring(b, user);
248 buffer_put_cstring(b, service);
249 buffer_put_cstring(b, context);
250 }
251
252 int
ssh_gssapi_check_mechanism(Gssctxt ** ctx,gss_OID oid,const char * host)253 ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
254 {
255 gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
256 OM_uint32 major, minor;
257 gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
258
259 /* RFC 4462 says we MUST NOT do SPNEGO */
260 if (oid->length == spnego_oid.length &&
261 (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0))
262 return 0; /* false */
263
264 ssh_gssapi_build_ctx(ctx);
265 ssh_gssapi_set_oid(*ctx, oid);
266 major = ssh_gssapi_import_name(*ctx, host);
267 if (!GSS_ERROR(major)) {
268 major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token,
269 NULL);
270 gss_release_buffer(&minor, &token);
271 if ((*ctx)->context != GSS_C_NO_CONTEXT)
272 gss_delete_sec_context(&minor, &(*ctx)->context,
273 GSS_C_NO_BUFFER);
274 }
275
276 if (GSS_ERROR(major))
277 ssh_gssapi_delete_ctx(ctx);
278
279 return (!GSS_ERROR(major));
280 }
281
282 #endif /* GSSAPI */
283