xref: /freebsd/crypto/heimdal/lib/gssapi/krb5/decapsulate.c (revision 195ebc7e9e4b129de810833791a19dfb4349d6a9)
1 /*
2  * Copyright (c) 1997 - 2001 Kungliga Tekniska H�gskolan
3  * (Royal Institute of Technology, Stockholm, Sweden).
4  * 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  *
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  *
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * 3. Neither the name of the Institute nor the names of its contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  */
33 
34 #include "krb5/gsskrb5_locl.h"
35 
36 RCSID("$Id: decapsulate.c 18334 2006-10-07 22:16:04Z lha $");
37 
38 /*
39  * return the length of the mechanism in token or -1
40  * (which implies that the token was bad - GSS_S_DEFECTIVE_TOKEN
41  */
42 
43 ssize_t
44 _gsskrb5_get_mech (const u_char *ptr,
45 		      size_t total_len,
46 		      const u_char **mech_ret)
47 {
48     size_t len, len_len, mech_len, foo;
49     const u_char *p = ptr;
50     int e;
51 
52     if (total_len < 1)
53 	return -1;
54     if (*p++ != 0x60)
55 	return -1;
56     e = der_get_length (p, total_len - 1, &len, &len_len);
57     if (e || 1 + len_len + len != total_len)
58 	return -1;
59     p += len_len;
60     if (*p++ != 0x06)
61 	return -1;
62     e = der_get_length (p, total_len - 1 - len_len - 1,
63 			&mech_len, &foo);
64     if (e)
65 	return -1;
66     p += foo;
67     *mech_ret = p;
68     return mech_len;
69 }
70 
71 OM_uint32
72 _gssapi_verify_mech_header(u_char **str,
73 			   size_t total_len,
74 			   gss_OID mech)
75 {
76     const u_char *p;
77     ssize_t mech_len;
78 
79     mech_len = _gsskrb5_get_mech (*str, total_len, &p);
80     if (mech_len < 0)
81 	return GSS_S_DEFECTIVE_TOKEN;
82 
83     if (mech_len != mech->length)
84 	return GSS_S_BAD_MECH;
85     if (memcmp(p,
86 	       mech->elements,
87 	       mech->length) != 0)
88 	return GSS_S_BAD_MECH;
89     p += mech_len;
90     *str = rk_UNCONST(p);
91     return GSS_S_COMPLETE;
92 }
93 
94 OM_uint32
95 _gsskrb5_verify_header(u_char **str,
96 			  size_t total_len,
97 			  const void *type,
98 			  gss_OID oid)
99 {
100     OM_uint32 ret;
101     size_t len;
102     u_char *p = *str;
103 
104     ret = _gssapi_verify_mech_header(str, total_len, oid);
105     if (ret)
106 	return ret;
107 
108     len = total_len - (*str - p);
109 
110     if (len < 2)
111 	return GSS_S_DEFECTIVE_TOKEN;
112 
113     if (memcmp (*str, type, 2) != 0)
114 	return GSS_S_DEFECTIVE_TOKEN;
115     *str += 2;
116 
117     return 0;
118 }
119 
120 /*
121  * Remove the GSS-API wrapping from `in_token' giving `out_data.
122  * Does not copy data, so just free `in_token'.
123  */
124 
125 OM_uint32
126 _gssapi_decapsulate(
127     OM_uint32 *minor_status,
128     gss_buffer_t input_token_buffer,
129     krb5_data *out_data,
130     const gss_OID mech
131 )
132 {
133     u_char *p;
134     OM_uint32 ret;
135 
136     p = input_token_buffer->value;
137     ret = _gssapi_verify_mech_header(&p,
138 				    input_token_buffer->length,
139 				    mech);
140     if (ret) {
141 	*minor_status = 0;
142 	return ret;
143     }
144 
145     out_data->length = input_token_buffer->length -
146 	(p - (u_char *)input_token_buffer->value);
147     out_data->data   = p;
148     return GSS_S_COMPLETE;
149 }
150 
151 /*
152  * Remove the GSS-API wrapping from `in_token' giving `out_data.
153  * Does not copy data, so just free `in_token'.
154  */
155 
156 OM_uint32
157 _gsskrb5_decapsulate(OM_uint32 *minor_status,
158 			gss_buffer_t input_token_buffer,
159 			krb5_data *out_data,
160 			const void *type,
161 			gss_OID oid)
162 {
163     u_char *p;
164     OM_uint32 ret;
165 
166     p = input_token_buffer->value;
167     ret = _gsskrb5_verify_header(&p,
168 				    input_token_buffer->length,
169 				    type,
170 				    oid);
171     if (ret) {
172 	*minor_status = 0;
173 	return ret;
174     }
175 
176     out_data->length = input_token_buffer->length -
177 	(p - (u_char *)input_token_buffer->value);
178     out_data->data   = p;
179     return GSS_S_COMPLETE;
180 }
181 
182 /*
183  * Verify padding of a gss wrapped message and return its length.
184  */
185 
186 OM_uint32
187 _gssapi_verify_pad(gss_buffer_t wrapped_token,
188 		   size_t datalen,
189 		   size_t *padlen)
190 {
191     u_char *pad;
192     size_t padlength;
193     int i;
194 
195     pad = (u_char *)wrapped_token->value + wrapped_token->length - 1;
196     padlength = *pad;
197 
198     if (padlength > datalen)
199 	return GSS_S_BAD_MECH;
200 
201     for (i = padlength; i > 0 && *pad == padlength; i--, pad--)
202 	;
203     if (i != 0)
204 	return GSS_S_BAD_MIC;
205 
206     *padlen = padlength;
207 
208     return 0;
209 }
210