1 /* $OpenBSD: gss-genr.c,v 1.26 2018/07/10 09:13:30 djm 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
33 #include <limits.h>
34 #include <stdarg.h>
35 #include <string.h>
36 #include <signal.h>
37 #include <unistd.h>
38
39 #include "xmalloc.h"
40 #include "ssherr.h"
41 #include "sshbuf.h"
42 #include "log.h"
43 #include "ssh2.h"
44
45 #include "ssh-gss.h"
46
47 extern u_char *session_id2;
48 extern u_int session_id2_len;
49
50 /* sshbuf_get for gss_buffer_desc */
51 int
ssh_gssapi_get_buffer_desc(struct sshbuf * b,gss_buffer_desc * g)52 ssh_gssapi_get_buffer_desc(struct sshbuf *b, gss_buffer_desc *g)
53 {
54 int r;
55 u_char *p;
56 size_t len;
57
58 if ((r = sshbuf_get_string(b, &p, &len)) != 0)
59 return r;
60 g->value = p;
61 g->length = len;
62 return 0;
63 }
64
65 /* Check that the OID in a data stream matches that in the context */
66 int
ssh_gssapi_check_oid(Gssctxt * ctx,void * data,size_t len)67 ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
68 {
69 return (ctx != NULL && ctx->oid != GSS_C_NO_OID &&
70 ctx->oid->length == len &&
71 memcmp(ctx->oid->elements, data, len) == 0);
72 }
73
74 /* Set the contexts OID from a data stream */
75 void
ssh_gssapi_set_oid_data(Gssctxt * ctx,void * data,size_t len)76 ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len)
77 {
78 if (ctx->oid != GSS_C_NO_OID) {
79 free(ctx->oid->elements);
80 free(ctx->oid);
81 }
82 ctx->oid = xcalloc(1, sizeof(gss_OID_desc));
83 ctx->oid->length = len;
84 ctx->oid->elements = xmalloc(len);
85 memcpy(ctx->oid->elements, data, len);
86 }
87
88 /* Set the contexts OID */
89 void
ssh_gssapi_set_oid(Gssctxt * ctx,gss_OID oid)90 ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid)
91 {
92 ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length);
93 }
94
95 /* All this effort to report an error ... */
96 void
ssh_gssapi_error(Gssctxt * ctxt)97 ssh_gssapi_error(Gssctxt *ctxt)
98 {
99 char *s;
100
101 s = ssh_gssapi_last_error(ctxt, NULL, NULL);
102 debug("%s", s);
103 free(s);
104 }
105
106 char *
ssh_gssapi_last_error(Gssctxt * ctxt,OM_uint32 * major_status,OM_uint32 * minor_status)107 ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status,
108 OM_uint32 *minor_status)
109 {
110 OM_uint32 lmin;
111 gss_buffer_desc msg = GSS_C_EMPTY_BUFFER;
112 OM_uint32 ctx;
113 struct sshbuf *b;
114 char *ret;
115 int r;
116
117 if ((b = sshbuf_new()) == NULL)
118 fatal("%s: sshbuf_new failed", __func__);
119
120 if (major_status != NULL)
121 *major_status = ctxt->major;
122 if (minor_status != NULL)
123 *minor_status = ctxt->minor;
124
125 ctx = 0;
126 /* The GSSAPI error */
127 do {
128 gss_display_status(&lmin, ctxt->major,
129 GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg);
130
131 if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 ||
132 (r = sshbuf_put_u8(b, '\n')) != 0)
133 fatal("%s: buffer error: %s", __func__, ssh_err(r));
134
135 gss_release_buffer(&lmin, &msg);
136 } while (ctx != 0);
137
138 /* The mechanism specific error */
139 do {
140 gss_display_status(&lmin, ctxt->minor,
141 GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg);
142
143 if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 ||
144 (r = sshbuf_put_u8(b, '\n')) != 0)
145 fatal("%s: buffer error: %s", __func__, ssh_err(r));
146
147 gss_release_buffer(&lmin, &msg);
148 } while (ctx != 0);
149
150 if ((r = sshbuf_put_u8(b, '\n')) != 0)
151 fatal("%s: buffer error: %s", __func__, ssh_err(r));
152 ret = xstrdup((const char *)sshbuf_ptr(b));
153 sshbuf_free(b);
154 return (ret);
155 }
156
157 /*
158 * Initialise our GSSAPI context. We use this opaque structure to contain all
159 * of the data which both the client and server need to persist across
160 * {accept,init}_sec_context calls, so that when we do it from the userauth
161 * stuff life is a little easier
162 */
163 void
ssh_gssapi_build_ctx(Gssctxt ** ctx)164 ssh_gssapi_build_ctx(Gssctxt **ctx)
165 {
166 *ctx = xcalloc(1, sizeof (Gssctxt));
167 (*ctx)->context = GSS_C_NO_CONTEXT;
168 (*ctx)->name = GSS_C_NO_NAME;
169 (*ctx)->oid = GSS_C_NO_OID;
170 (*ctx)->creds = GSS_C_NO_CREDENTIAL;
171 (*ctx)->client = GSS_C_NO_NAME;
172 (*ctx)->client_creds = GSS_C_NO_CREDENTIAL;
173 }
174
175 /* Delete our context, providing it has been built correctly */
176 void
ssh_gssapi_delete_ctx(Gssctxt ** ctx)177 ssh_gssapi_delete_ctx(Gssctxt **ctx)
178 {
179 OM_uint32 ms;
180
181 if ((*ctx) == NULL)
182 return;
183 if ((*ctx)->context != GSS_C_NO_CONTEXT)
184 gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER);
185 if ((*ctx)->name != GSS_C_NO_NAME)
186 gss_release_name(&ms, &(*ctx)->name);
187 if ((*ctx)->oid != GSS_C_NO_OID) {
188 free((*ctx)->oid->elements);
189 free((*ctx)->oid);
190 (*ctx)->oid = GSS_C_NO_OID;
191 }
192 if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
193 gss_release_cred(&ms, &(*ctx)->creds);
194 if ((*ctx)->client != GSS_C_NO_NAME)
195 gss_release_name(&ms, &(*ctx)->client);
196 if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
197 gss_release_cred(&ms, &(*ctx)->client_creds);
198
199 free(*ctx);
200 *ctx = NULL;
201 }
202
203 /*
204 * Wrapper to init_sec_context
205 * Requires that the context contains:
206 * oid
207 * server name (from ssh_gssapi_import_name)
208 */
209 OM_uint32
ssh_gssapi_init_ctx(Gssctxt * ctx,int deleg_creds,gss_buffer_desc * recv_tok,gss_buffer_desc * send_tok,OM_uint32 * flags)210 ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
211 gss_buffer_desc* send_tok, OM_uint32 *flags)
212 {
213 int deleg_flag = 0;
214
215 if (deleg_creds) {
216 deleg_flag = GSS_C_DELEG_FLAG;
217 debug("Delegating credentials");
218 }
219
220 ctx->major = gss_init_sec_context(&ctx->minor,
221 GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid,
222 GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
223 0, NULL, recv_tok, NULL, send_tok, flags, NULL);
224
225 if (GSS_ERROR(ctx->major))
226 ssh_gssapi_error(ctx);
227
228 return (ctx->major);
229 }
230
231 /* Create a service name for the given host */
232 OM_uint32
ssh_gssapi_import_name(Gssctxt * ctx,const char * host)233 ssh_gssapi_import_name(Gssctxt *ctx, const char *host)
234 {
235 gss_buffer_desc gssbuf;
236 char *val;
237
238 xasprintf(&val, "host@%s", host);
239 gssbuf.value = val;
240 gssbuf.length = strlen(gssbuf.value);
241
242 if ((ctx->major = gss_import_name(&ctx->minor,
243 &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name)))
244 ssh_gssapi_error(ctx);
245
246 free(gssbuf.value);
247 return (ctx->major);
248 }
249
250 OM_uint32
ssh_gssapi_sign(Gssctxt * ctx,gss_buffer_t buffer,gss_buffer_t hash)251 ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
252 {
253 if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
254 GSS_C_QOP_DEFAULT, buffer, hash)))
255 ssh_gssapi_error(ctx);
256
257 return (ctx->major);
258 }
259
260 void
ssh_gssapi_buildmic(struct sshbuf * b,const char * user,const char * service,const char * context)261 ssh_gssapi_buildmic(struct sshbuf *b, const char *user, const char *service,
262 const char *context)
263 {
264 int r;
265
266 sshbuf_reset(b);
267 if ((r = sshbuf_put_string(b, session_id2, session_id2_len)) != 0 ||
268 (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
269 (r = sshbuf_put_cstring(b, user)) != 0 ||
270 (r = sshbuf_put_cstring(b, service)) != 0 ||
271 (r = sshbuf_put_cstring(b, context)) != 0)
272 fatal("%s: buffer error: %s", __func__, ssh_err(r));
273 }
274
275 int
ssh_gssapi_check_mechanism(Gssctxt ** ctx,gss_OID oid,const char * host)276 ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
277 {
278 gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
279 OM_uint32 major, minor;
280 gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
281
282 /* RFC 4462 says we MUST NOT do SPNEGO */
283 if (oid->length == spnego_oid.length &&
284 (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0))
285 return 0; /* false */
286
287 ssh_gssapi_build_ctx(ctx);
288 ssh_gssapi_set_oid(*ctx, oid);
289 major = ssh_gssapi_import_name(*ctx, host);
290 if (!GSS_ERROR(major)) {
291 major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token,
292 NULL);
293 gss_release_buffer(&minor, &token);
294 if ((*ctx)->context != GSS_C_NO_CONTEXT)
295 gss_delete_sec_context(&minor, &(*ctx)->context,
296 GSS_C_NO_BUFFER);
297 }
298
299 if (GSS_ERROR(major))
300 ssh_gssapi_delete_ctx(ctx);
301
302 return (!GSS_ERROR(major));
303 }
304
305 #endif /* GSSAPI */
306