xref: /openssh-portable/gss-genr.c (revision 0f3958c1)
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