1 /*-
2  * Copyright (c) 2008 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 
33 #include "utils.h"
34 
35 OM_uint32
36 gss_decapsulate_token(const gss_buffer_t input_token, gss_OID oid,
37     gss_buffer_t output_token)
38 {
39 	unsigned char *p = input_token->value;
40 	size_t len = input_token->length;
41 	size_t a, b;
42 	gss_OID_desc mech_oid;
43 
44 	_gss_buffer_zero(output_token);
45 
46 	/*
47 	 * Token must start with [APPLICATION 0] SEQUENCE.
48 	 */
49 	if (len == 0 || *p != 0x60)
50 		return (GSS_S_DEFECTIVE_TOKEN);
51 	p++;
52 	len--;
53 
54 	/*
55 	 * Decode the length and make sure it agrees with the
56 	 * token length.
57 	 */
58 	if (len == 0)
59 		return (GSS_S_DEFECTIVE_TOKEN);
60 	if ((*p & 0x80) == 0) {
61 		a = *p;
62 		p++;
63 		len--;
64 	} else {
65 		b = *p & 0x7f;
66 		p++;
67 		len--;
68 		if (len < b)
69 			return (GSS_S_DEFECTIVE_TOKEN);
70 		a = 0;
71 		while (b) {
72 			a = (a << 8) | *p;
73 			p++;
74 			len--;
75 			b--;
76 		}
77 	}
78 	if (a != len)
79 		return (GSS_S_DEFECTIVE_TOKEN);
80 
81 	/*
82 	 * Decode the OID for the mechanism. Simplify life by
83 	 * assuming that the OID length is less than 128 bytes.
84 	 */
85 	if (len < 2 || *p != 0x06)
86 		return (GSS_S_DEFECTIVE_TOKEN);
87 	if ((p[1] & 0x80) || p[1] > (len - 2))
88 		return (GSS_S_DEFECTIVE_TOKEN);
89 	mech_oid.length = p[1];
90 	p += 2;
91 	len -= 2;
92 	mech_oid.elements = p;
93 
94 	if (!gss_oid_equal(&mech_oid, oid))
95 		return (GSS_S_FAILURE);
96 
97 	p += mech_oid.length;
98 	len -= mech_oid.length;
99 
100 	output_token->length = len;
101 	output_token->value = malloc(len);
102 	if (!output_token->value)
103 		return (GSS_S_DEFECTIVE_TOKEN);
104 	memcpy(output_token->value, p, len);
105 
106 	return (GSS_S_COMPLETE);
107 }
108