xref: /freebsd/lib/libgssapi/gss_accept_sec_context.c (revision 271c3a9060f2ee55607ebe146523f888e1db2654)
1 /*-
2  * Copyright (c) 2005 Doug Rabson
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24  * SUCH DAMAGE.
25  *
26  *	$FreeBSD$
27  */
28 
29 #include <gssapi/gssapi.h>
30 #include <stdlib.h>
31 #include <string.h>
32 #include <errno.h>
33 
34 #include "mech_switch.h"
35 #include "context.h"
36 #include "cred.h"
37 #include "name.h"
38 #include "utils.h"
39 
40 static OM_uint32
41 parse_header(const gss_buffer_t input_token, gss_OID mech_oid)
42 {
43 	unsigned char *p = input_token->value;
44 	size_t len = input_token->length;
45 	size_t a, b;
46 
47 	/*
48 	 * Token must start with [APPLICATION 0] SEQUENCE.
49 	 * But if it doesn't assume it is DCE-STYLE Kerberos!
50 	 */
51 	if (len == 0)
52 		return (GSS_S_DEFECTIVE_TOKEN);
53 
54 	p++;
55 	len--;
56 
57 	/*
58 	 * Decode the length and make sure it agrees with the
59 	 * token length.
60 	 */
61 	if (len == 0)
62 		return (GSS_S_DEFECTIVE_TOKEN);
63 	if ((*p & 0x80) == 0) {
64 		a = *p;
65 		p++;
66 		len--;
67 	} else {
68 		b = *p & 0x7f;
69 		p++;
70 		len--;
71 		if (len < b)
72 		    return (GSS_S_DEFECTIVE_TOKEN);
73 		a = 0;
74 		while (b) {
75 		    a = (a << 8) | *p;
76 		    p++;
77 		    len--;
78 		    b--;
79 		}
80 	}
81 	if (a != len)
82 		return (GSS_S_DEFECTIVE_TOKEN);
83 
84 	/*
85 	 * Decode the OID for the mechanism. Simplify life by
86 	 * assuming that the OID length is less than 128 bytes.
87 	 */
88 	if (len < 2 || *p != 0x06)
89 		return (GSS_S_DEFECTIVE_TOKEN);
90 	if ((p[1] & 0x80) || p[1] > (len - 2))
91 		return (GSS_S_DEFECTIVE_TOKEN);
92 	mech_oid->length = p[1];
93 	p += 2;
94 	len -= 2;
95 	mech_oid->elements = p;
96 
97 	return (GSS_S_COMPLETE);
98 }
99 
100 static gss_OID_desc krb5_mechanism =
101 {9, (void *)(uintptr_t) "\x2a\x86\x48\x86\xf7\x12\x01\x02\x02"};
102 static gss_OID_desc ntlm_mechanism =
103 {10, (void *)(uintptr_t) "\x2b\x06\x01\x04\x01\x82\x37\x02\x02\x0a"};
104 static gss_OID_desc spnego_mechanism =
105 {6, (void *)(uintptr_t) "\x2b\x06\x01\x05\x05\x02"};
106 
107 static OM_uint32
108 choose_mech(const gss_buffer_t input, gss_OID mech_oid)
109 {
110 	OM_uint32 status;
111 
112 	/*
113 	 * First try to parse the gssapi token header and see if it's a
114 	 * correct header, use that in the first hand.
115 	 */
116 
117 	status = parse_header(input, mech_oid);
118 	if (status == GSS_S_COMPLETE)
119 		return (GSS_S_COMPLETE);
120 
121 	/*
122 	 * Lets guess what mech is really is, callback function to mech ??
123 	 */
124 
125 	if (input->length > 8 &&
126 	    memcmp((const char *)input->value, "NTLMSSP\x00", 8) == 0)
127 	{
128 		*mech_oid = ntlm_mechanism;
129 		return (GSS_S_COMPLETE);
130 	} else if (input->length != 0 &&
131 	    ((const char *)input->value)[0] == 0x6E)
132 	{
133 		/* Could be a raw AP-REQ (check for APPLICATION tag) */
134 		*mech_oid = krb5_mechanism;
135 		return (GSS_S_COMPLETE);
136 	} else if (input->length == 0) {
137 		/*
138 		 * There is the a wierd mode of SPNEGO (in CIFS and
139 		 * SASL GSS-SPENGO where the first token is zero
140 		 * length and the acceptor returns a mech_list, lets
141 		 * hope that is what is happening now.
142 		 */
143 		*mech_oid = spnego_mechanism;
144 		return (GSS_S_COMPLETE);
145 	}
146 	return (status);
147 }
148 
149 OM_uint32 gss_accept_sec_context(OM_uint32 *minor_status,
150     gss_ctx_id_t *context_handle,
151     const gss_cred_id_t acceptor_cred_handle,
152     const gss_buffer_t input_token,
153     const gss_channel_bindings_t input_chan_bindings,
154     gss_name_t *src_name,
155     gss_OID *mech_type,
156     gss_buffer_t output_token,
157     OM_uint32 *ret_flags,
158     OM_uint32 *time_rec,
159     gss_cred_id_t *delegated_cred_handle)
160 {
161 	OM_uint32 major_status, mech_ret_flags;
162 	struct _gss_mech_switch *m;
163 	struct _gss_context *ctx = (struct _gss_context *) *context_handle;
164 	struct _gss_cred *cred = (struct _gss_cred *) acceptor_cred_handle;
165 	struct _gss_mechanism_cred *mc;
166 	gss_cred_id_t acceptor_mc, delegated_mc;
167 	gss_name_t src_mn;
168 	int allocated_ctx;
169 
170 	*minor_status = 0;
171 	if (src_name)
172 		*src_name = GSS_C_NO_NAME;
173 	if (mech_type)
174 		*mech_type = GSS_C_NO_OID;
175 	if (ret_flags)
176 		*ret_flags = 0;
177 	if (time_rec)
178 		*time_rec = 0;
179 	if (delegated_cred_handle)
180 		*delegated_cred_handle = GSS_C_NO_CREDENTIAL;
181 	_gss_buffer_zero(output_token);
182 
183 	/*
184 	 * If this is the first call (*context_handle is NULL), we must
185 	 * parse the input token to figure out the mechanism to use.
186 	 */
187 	if (*context_handle == GSS_C_NO_CONTEXT) {
188 		gss_OID_desc mech_oid;
189 
190 		major_status = choose_mech(input_token, &mech_oid);
191 		if (major_status != GSS_S_COMPLETE)
192 			return (major_status);
193 
194 		/*
195 		 * Now that we have a mechanism, we can find the
196 		 * implementation.
197 		 */
198 		ctx = malloc(sizeof(struct _gss_context));
199 		if (!ctx) {
200 			*minor_status = ENOMEM;
201 			return (GSS_S_DEFECTIVE_TOKEN);
202 		}
203 		memset(ctx, 0, sizeof(struct _gss_context));
204 		m = ctx->gc_mech = _gss_find_mech_switch(&mech_oid);
205 		if (!m) {
206 			free(ctx);
207 			return (GSS_S_BAD_MECH);
208 		}
209 		allocated_ctx = 1;
210 	} else {
211 		m = ctx->gc_mech;
212 		allocated_ctx = 0;
213 	}
214 
215 	if (cred) {
216 		SLIST_FOREACH(mc, &cred->gc_mc, gmc_link)
217 			if (mc->gmc_mech == m)
218 				break;
219 		if (!mc)
220 			return (GSS_S_BAD_MECH);
221 		acceptor_mc = mc->gmc_cred;
222 	} else {
223 		acceptor_mc = GSS_C_NO_CREDENTIAL;
224 	}
225 	delegated_mc = GSS_C_NO_CREDENTIAL;
226 
227 	mech_ret_flags = 0;
228 	major_status = m->gm_accept_sec_context(minor_status,
229 	    &ctx->gc_ctx,
230 	    acceptor_mc,
231 	    input_token,
232 	    input_chan_bindings,
233 	    &src_mn,
234 	    mech_type,
235 	    output_token,
236 	    &mech_ret_flags,
237 	    time_rec,
238 	    &delegated_mc);
239 	if (major_status != GSS_S_COMPLETE &&
240 	    major_status != GSS_S_CONTINUE_NEEDED) {
241 		_gss_mg_error(m, major_status, *minor_status);
242 		return (major_status);
243 	}
244 
245 	if (src_name && src_mn) {
246 		/*
247 		 * Make a new name and mark it as an MN.
248 		 */
249 		struct _gss_name *name = _gss_make_name(m, src_mn);
250 
251 		if (!name) {
252 			m->gm_release_name(minor_status, &src_mn);
253 			return (GSS_S_FAILURE);
254 		}
255 		*src_name = (gss_name_t) name;
256 	} else if (src_mn) {
257 		m->gm_release_name(minor_status, &src_mn);
258 	}
259 
260 	if (delegated_mc == GSS_C_NO_CREDENTIAL)
261 		mech_ret_flags &= ~GSS_C_DELEG_FLAG;
262 
263 	if (mech_ret_flags & GSS_C_DELEG_FLAG) {
264 		if (!delegated_cred_handle) {
265 			m->gm_release_cred(minor_status, &delegated_mc);
266 			mech_ret_flags &= ~GSS_C_DELEG_FLAG;
267 		} else {
268 			struct _gss_cred *dcred;
269 			struct _gss_mechanism_cred *dmc;
270 
271 			dcred = malloc(sizeof(struct _gss_cred));
272 			if (!dcred) {
273 				*minor_status = ENOMEM;
274 				return (GSS_S_FAILURE);
275 			}
276 			SLIST_INIT(&dcred->gc_mc);
277 			dmc = malloc(sizeof(struct _gss_mechanism_cred));
278 			if (!dmc) {
279 				free(dcred);
280 				*minor_status = ENOMEM;
281 				return (GSS_S_FAILURE);
282 			}
283 			dmc->gmc_mech = m;
284 			dmc->gmc_mech_oid = &m->gm_mech_oid;
285 			dmc->gmc_cred = delegated_mc;
286 			SLIST_INSERT_HEAD(&dcred->gc_mc, dmc, gmc_link);
287 
288 			*delegated_cred_handle = (gss_cred_id_t) dcred;
289 		}
290 	}
291 
292 	if (ret_flags)
293 		*ret_flags = mech_ret_flags;
294 	*context_handle = (gss_ctx_id_t) ctx;
295 	return (major_status);
296 }
297