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