1 /* $NetBSD: gss-genr.c,v 1.12 2024/06/25 16:36:54 christos Exp $ */
2 /* $OpenBSD: gss-genr.c,v 1.29 2024/02/01 02:37:33 djm Exp $ */
3
4 /*
5 * Copyright (c) 2001-2007 Simon Wilkinson. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28 #include "includes.h"
29 __RCSID("$NetBSD");
30 #ifdef GSSAPI
31
32
33 #include <stdarg.h>
34 #include <string.h>
35 #include <unistd.h>
36 #include <stdarg.h>
37 #include <limits.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 /* sshbuf_get for gss_buffer_desc */
48 int
ssh_gssapi_get_buffer_desc(struct sshbuf * b,gss_buffer_desc * g)49 ssh_gssapi_get_buffer_desc(struct sshbuf *b, gss_buffer_desc *g)
50 {
51 int r;
52 u_char *p;
53 size_t len;
54
55 if ((r = sshbuf_get_string(b, &p, &len)) != 0)
56 return r;
57 g->value = p;
58 g->length = len;
59 return 0;
60 }
61
62 /* Check that the OID in a data stream matches that in the context */
63 int
ssh_gssapi_check_oid(Gssctxt * ctx,void * data,size_t len)64 ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
65 {
66 return (ctx != NULL && ctx->oid != GSS_C_NO_OID &&
67 ctx->oid->length == len &&
68 memcmp(ctx->oid->elements, data, len) == 0);
69 }
70
71 /* Set the contexts OID from a data stream */
72 void
ssh_gssapi_set_oid_data(Gssctxt * ctx,void * data,size_t len)73 ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len)
74 {
75 if (ctx->oid != GSS_C_NO_OID) {
76 free(ctx->oid->elements);
77 free(ctx->oid);
78 }
79 ctx->oid = xcalloc(1, sizeof(gss_OID_desc));
80 ctx->oid->length = len;
81 ctx->oid->elements = xmalloc(len);
82 memcpy(ctx->oid->elements, data, len);
83 }
84
85 /* Set the contexts OID */
86 void
ssh_gssapi_set_oid(Gssctxt * ctx,gss_OID oid)87 ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid)
88 {
89 ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length);
90 }
91
92 /* All this effort to report an error ... */
93 void
ssh_gssapi_error(Gssctxt * ctxt)94 ssh_gssapi_error(Gssctxt *ctxt)
95 {
96 char *s;
97
98 s = ssh_gssapi_last_error(ctxt, NULL, NULL);
99 debug("%s", s);
100 free(s);
101 }
102
103 char *
ssh_gssapi_last_error(Gssctxt * ctxt,OM_uint32 * major_status,OM_uint32 * minor_status)104 ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status,
105 OM_uint32 *minor_status)
106 {
107 OM_uint32 lmin;
108 gss_buffer_desc msg = GSS_C_EMPTY_BUFFER;
109 OM_uint32 ctx;
110 struct sshbuf *b;
111 char *ret;
112 int r;
113
114 if ((b = sshbuf_new()) == NULL)
115 fatal_f("sshbuf_new failed");
116
117 if (major_status != NULL)
118 *major_status = ctxt->major;
119 if (minor_status != NULL)
120 *minor_status = ctxt->minor;
121
122 ctx = 0;
123 /* The GSSAPI error */
124 do {
125 gss_display_status(&lmin, ctxt->major,
126 GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg);
127
128 if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 ||
129 (r = sshbuf_put_u8(b, '\n')) != 0)
130 fatal_fr(r, "assemble GSS_CODE");
131
132 gss_release_buffer(&lmin, &msg);
133 } while (ctx != 0);
134
135 /* The mechanism specific error */
136 do {
137 gss_display_status(&lmin, ctxt->minor,
138 GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg);
139
140 if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 ||
141 (r = sshbuf_put_u8(b, '\n')) != 0)
142 fatal_fr(r, "assemble MECH_CODE");
143
144 gss_release_buffer(&lmin, &msg);
145 } while (ctx != 0);
146
147 if ((r = sshbuf_put_u8(b, '\n')) != 0)
148 fatal_fr(r, "assemble newline");
149 ret = xstrdup((const char *)sshbuf_ptr(b));
150 sshbuf_free(b);
151 return (ret);
152 }
153
154 /*
155 * Initialise our GSSAPI context. We use this opaque structure to contain all
156 * of the data which both the client and server need to persist across
157 * {accept,init}_sec_context calls, so that when we do it from the userauth
158 * stuff life is a little easier
159 */
160 void
ssh_gssapi_build_ctx(Gssctxt ** ctx)161 ssh_gssapi_build_ctx(Gssctxt **ctx)
162 {
163 *ctx = xcalloc(1, sizeof (Gssctxt));
164 (*ctx)->context = GSS_C_NO_CONTEXT;
165 (*ctx)->name = GSS_C_NO_NAME;
166 (*ctx)->oid = GSS_C_NO_OID;
167 (*ctx)->creds = GSS_C_NO_CREDENTIAL;
168 (*ctx)->client = GSS_C_NO_NAME;
169 (*ctx)->client_creds = GSS_C_NO_CREDENTIAL;
170 }
171
172 /* Delete our context, providing it has been built correctly */
173 void
ssh_gssapi_delete_ctx(Gssctxt ** ctx)174 ssh_gssapi_delete_ctx(Gssctxt **ctx)
175 {
176 OM_uint32 ms;
177
178 if ((*ctx) == NULL)
179 return;
180 if ((*ctx)->context != GSS_C_NO_CONTEXT)
181 gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER);
182 if ((*ctx)->name != GSS_C_NO_NAME)
183 gss_release_name(&ms, &(*ctx)->name);
184 if ((*ctx)->oid != GSS_C_NO_OID) {
185 free((*ctx)->oid->elements);
186 free((*ctx)->oid);
187 (*ctx)->oid = GSS_C_NO_OID;
188 }
189 if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
190 gss_release_cred(&ms, &(*ctx)->creds);
191 if ((*ctx)->client != GSS_C_NO_NAME)
192 gss_release_name(&ms, &(*ctx)->client);
193 if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
194 gss_release_cred(&ms, &(*ctx)->client_creds);
195
196 free(*ctx);
197 *ctx = NULL;
198 }
199
200 /*
201 * Wrapper to init_sec_context
202 * Requires that the context contains:
203 * oid
204 * server name (from ssh_gssapi_import_name)
205 */
206 OM_uint32
ssh_gssapi_init_ctx(Gssctxt * ctx,int deleg_creds,gss_buffer_desc * recv_tok,gss_buffer_desc * send_tok,OM_uint32 * flags)207 ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
208 gss_buffer_desc* send_tok, OM_uint32 *flags)
209 {
210 int deleg_flag = 0;
211
212 if (deleg_creds) {
213 deleg_flag = GSS_C_DELEG_FLAG;
214 debug("Delegating credentials");
215 }
216
217 ctx->major = gss_init_sec_context(&ctx->minor,
218 GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid,
219 GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
220 0, NULL, recv_tok, NULL, send_tok, flags, NULL);
221
222 if (GSS_ERROR(ctx->major))
223 ssh_gssapi_error(ctx);
224
225 return (ctx->major);
226 }
227
228 /* Create a service name for the given host */
229 OM_uint32
ssh_gssapi_import_name(Gssctxt * ctx,const char * host)230 ssh_gssapi_import_name(Gssctxt *ctx, const char *host)
231 {
232 gss_buffer_desc gssbuf;
233 char *val;
234
235 xasprintf(&val, "host@%s", host);
236 gssbuf.value = val;
237 gssbuf.length = strlen(gssbuf.value);
238
239 if ((ctx->major = gss_import_name(&ctx->minor,
240 &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name)))
241 ssh_gssapi_error(ctx);
242
243 free(gssbuf.value);
244 return (ctx->major);
245 }
246
247 OM_uint32
ssh_gssapi_sign(Gssctxt * ctx,gss_buffer_t buffer,gss_buffer_t hash)248 ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
249 {
250 if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
251 GSS_C_QOP_DEFAULT, buffer, hash)))
252 ssh_gssapi_error(ctx);
253
254 return (ctx->major);
255 }
256
257 void
ssh_gssapi_buildmic(struct sshbuf * b,const char * user,const char * service,const char * context,const struct sshbuf * session_id)258 ssh_gssapi_buildmic(struct sshbuf *b, const char *user, const char *service,
259 const char *context, const struct sshbuf *session_id)
260 {
261 int r;
262
263 sshbuf_reset(b);
264 if ((r = sshbuf_put_stringb(b, session_id)) != 0 ||
265 (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
266 (r = sshbuf_put_cstring(b, user)) != 0 ||
267 (r = sshbuf_put_cstring(b, service)) != 0 ||
268 (r = sshbuf_put_cstring(b, context)) != 0)
269 fatal_fr(r, "assemble buildmic");
270 }
271
272 int
ssh_gssapi_check_mechanism(Gssctxt ** ctx,gss_OID oid,const char * host)273 ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
274 {
275 gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
276 OM_uint32 major, minor;
277 gss_OID_desc spnego_oid = {6, __UNCONST("\x2B\x06\x01\x05\x05\x02")};
278
279 /* RFC 4462 says we MUST NOT do SPNEGO */
280 if (oid->length == spnego_oid.length &&
281 (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0))
282 return 0; /* false */
283
284 ssh_gssapi_build_ctx(ctx);
285 ssh_gssapi_set_oid(*ctx, oid);
286 major = ssh_gssapi_import_name(*ctx, host);
287 if (!GSS_ERROR(major)) {
288 major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token,
289 NULL);
290 gss_release_buffer(&minor, &token);
291 if ((*ctx)->context != GSS_C_NO_CONTEXT)
292 gss_delete_sec_context(&minor, &(*ctx)->context,
293 GSS_C_NO_BUFFER);
294 }
295
296 if (GSS_ERROR(major))
297 ssh_gssapi_delete_ctx(ctx);
298
299 return (!GSS_ERROR(major));
300 }
301
302 #endif /* GSSAPI */
303