xref: /freebsd/crypto/openssh/gss-genr.c (revision 09d325677d53a12c79a43664ff29871e92247629)
1 /* $OpenBSD: gss-genr.c,v 1.21 2013/05/17 00:13:13 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 #include <sys/param.h>
33 
34 #include <stdarg.h>
35 #include <string.h>
36 #include <unistd.h>
37 
38 #include "xmalloc.h"
39 #include "buffer.h"
40 #include "log.h"
41 #include "ssh2.h"
42 
43 #include "ssh-gss.h"
44 
45 extern u_char *session_id2;
46 extern u_int session_id2_len;
47 
48 /* Check that the OID in a data stream matches that in the context */
49 int
50 ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
51 {
52 	return (ctx != NULL && ctx->oid != GSS_C_NO_OID &&
53 	    ctx->oid->length == len &&
54 	    memcmp(ctx->oid->elements, data, len) == 0);
55 }
56 
57 /* Set the contexts OID from a data stream */
58 void
59 ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len)
60 {
61 	if (ctx->oid != GSS_C_NO_OID) {
62 		free(ctx->oid->elements);
63 		free(ctx->oid);
64 	}
65 	ctx->oid = xmalloc(sizeof(gss_OID_desc));
66 	ctx->oid->length = len;
67 	ctx->oid->elements = xmalloc(len);
68 	memcpy(ctx->oid->elements, data, len);
69 }
70 
71 /* Set the contexts OID */
72 void
73 ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid)
74 {
75 	ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length);
76 }
77 
78 /* All this effort to report an error ... */
79 void
80 ssh_gssapi_error(Gssctxt *ctxt)
81 {
82 	char *s;
83 
84 	s = ssh_gssapi_last_error(ctxt, NULL, NULL);
85 	debug("%s", s);
86 	free(s);
87 }
88 
89 char *
90 ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status,
91     OM_uint32 *minor_status)
92 {
93 	OM_uint32 lmin;
94 	gss_buffer_desc msg = GSS_C_EMPTY_BUFFER;
95 	OM_uint32 ctx;
96 	Buffer b;
97 	char *ret;
98 
99 	buffer_init(&b);
100 
101 	if (major_status != NULL)
102 		*major_status = ctxt->major;
103 	if (minor_status != NULL)
104 		*minor_status = ctxt->minor;
105 
106 	ctx = 0;
107 	/* The GSSAPI error */
108 	do {
109 		gss_display_status(&lmin, ctxt->major,
110 		    GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg);
111 
112 		buffer_append(&b, msg.value, msg.length);
113 		buffer_put_char(&b, '\n');
114 
115 		gss_release_buffer(&lmin, &msg);
116 	} while (ctx != 0);
117 
118 	/* The mechanism specific error */
119 	do {
120 		gss_display_status(&lmin, ctxt->minor,
121 		    GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg);
122 
123 		buffer_append(&b, msg.value, msg.length);
124 		buffer_put_char(&b, '\n');
125 
126 		gss_release_buffer(&lmin, &msg);
127 	} while (ctx != 0);
128 
129 	buffer_put_char(&b, '\0');
130 	ret = xmalloc(buffer_len(&b));
131 	buffer_get(&b, ret, buffer_len(&b));
132 	buffer_free(&b);
133 	return (ret);
134 }
135 
136 /*
137  * Initialise our GSSAPI context. We use this opaque structure to contain all
138  * of the data which both the client and server need to persist across
139  * {accept,init}_sec_context calls, so that when we do it from the userauth
140  * stuff life is a little easier
141  */
142 void
143 ssh_gssapi_build_ctx(Gssctxt **ctx)
144 {
145 	*ctx = xcalloc(1, sizeof (Gssctxt));
146 	(*ctx)->context = GSS_C_NO_CONTEXT;
147 	(*ctx)->name = GSS_C_NO_NAME;
148 	(*ctx)->oid = GSS_C_NO_OID;
149 	(*ctx)->creds = GSS_C_NO_CREDENTIAL;
150 	(*ctx)->client = GSS_C_NO_NAME;
151 	(*ctx)->client_creds = GSS_C_NO_CREDENTIAL;
152 }
153 
154 /* Delete our context, providing it has been built correctly */
155 void
156 ssh_gssapi_delete_ctx(Gssctxt **ctx)
157 {
158 	OM_uint32 ms;
159 
160 	if ((*ctx) == NULL)
161 		return;
162 	if ((*ctx)->context != GSS_C_NO_CONTEXT)
163 		gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER);
164 	if ((*ctx)->name != GSS_C_NO_NAME)
165 		gss_release_name(&ms, &(*ctx)->name);
166 	if ((*ctx)->oid != GSS_C_NO_OID) {
167 		free((*ctx)->oid->elements);
168 		free((*ctx)->oid);
169 		(*ctx)->oid = GSS_C_NO_OID;
170 	}
171 	if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
172 		gss_release_cred(&ms, &(*ctx)->creds);
173 	if ((*ctx)->client != GSS_C_NO_NAME)
174 		gss_release_name(&ms, &(*ctx)->client);
175 	if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
176 		gss_release_cred(&ms, &(*ctx)->client_creds);
177 
178 	free(*ctx);
179 	*ctx = NULL;
180 }
181 
182 /*
183  * Wrapper to init_sec_context
184  * Requires that the context contains:
185  *	oid
186  *	server name (from ssh_gssapi_import_name)
187  */
188 OM_uint32
189 ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
190     gss_buffer_desc* send_tok, OM_uint32 *flags)
191 {
192 	int deleg_flag = 0;
193 
194 	if (deleg_creds) {
195 		deleg_flag = GSS_C_DELEG_FLAG;
196 		debug("Delegating credentials");
197 	}
198 
199 	ctx->major = gss_init_sec_context(&ctx->minor,
200 	    GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid,
201 	    GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
202 	    0, NULL, recv_tok, NULL, send_tok, flags, NULL);
203 
204 	if (GSS_ERROR(ctx->major))
205 		ssh_gssapi_error(ctx);
206 
207 	return (ctx->major);
208 }
209 
210 /* Create a service name for the given host */
211 OM_uint32
212 ssh_gssapi_import_name(Gssctxt *ctx, const char *host)
213 {
214 	gss_buffer_desc gssbuf;
215 	char *val;
216 
217 	xasprintf(&val, "host@%s", host);
218 	gssbuf.value = val;
219 	gssbuf.length = strlen(gssbuf.value);
220 
221 	if ((ctx->major = gss_import_name(&ctx->minor,
222 	    &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name)))
223 		ssh_gssapi_error(ctx);
224 
225 	free(gssbuf.value);
226 	return (ctx->major);
227 }
228 
229 OM_uint32
230 ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
231 {
232 	if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
233 	    GSS_C_QOP_DEFAULT, buffer, hash)))
234 		ssh_gssapi_error(ctx);
235 
236 	return (ctx->major);
237 }
238 
239 void
240 ssh_gssapi_buildmic(Buffer *b, const char *user, const char *service,
241     const char *context)
242 {
243 	buffer_init(b);
244 	buffer_put_string(b, session_id2, session_id2_len);
245 	buffer_put_char(b, SSH2_MSG_USERAUTH_REQUEST);
246 	buffer_put_cstring(b, user);
247 	buffer_put_cstring(b, service);
248 	buffer_put_cstring(b, context);
249 }
250 
251 int
252 ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
253 {
254 	gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
255 	OM_uint32 major, minor;
256 	gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
257 
258 	/* RFC 4462 says we MUST NOT do SPNEGO */
259 	if (oid->length == spnego_oid.length &&
260 	    (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0))
261 		return 0; /* false */
262 
263 	ssh_gssapi_build_ctx(ctx);
264 	ssh_gssapi_set_oid(*ctx, oid);
265 	major = ssh_gssapi_import_name(*ctx, host);
266 	if (!GSS_ERROR(major)) {
267 		major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token,
268 		    NULL);
269 		gss_release_buffer(&minor, &token);
270 		if ((*ctx)->context != GSS_C_NO_CONTEXT)
271 			gss_delete_sec_context(&minor, &(*ctx)->context,
272 			    GSS_C_NO_BUFFER);
273 	}
274 
275 	if (GSS_ERROR(major))
276 		ssh_gssapi_delete_ctx(ctx);
277 
278 	return (!GSS_ERROR(major));
279 }
280 
281 #endif /* GSSAPI */
282