1 /*
2  *  linux/net/sunrpc/gss_generic_token.c
3  *
4  *  Adapted from MIT Kerberos 5-1.2.1 lib/gssapi/generic/util_token.c
5  *
6  *  Copyright (c) 2000 The Regents of the University of Michigan.
7  *  All rights reserved.
8  *
9  *  Andy Adamson   <andros@umich.edu>
10  */
11 
12 /*
13  * Copyright 1993 by OpenVision Technologies, Inc.
14  *
15  * Permission to use, copy, modify, distribute, and sell this software
16  * and its documentation for any purpose is hereby granted without fee,
17  * provided that the above copyright notice appears in all copies and
18  * that both that copyright notice and this permission notice appear in
19  * supporting documentation, and that the name of OpenVision not be used
20  * in advertising or publicity pertaining to distribution of the software
21  * without specific, written prior permission. OpenVision makes no
22  * representations about the suitability of this software for any
23  * purpose.  It is provided "as is" without express or implied warranty.
24  *
25  * OPENVISION DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
26  * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
27  * EVENT SHALL OPENVISION BE LIABLE FOR ANY SPECIAL, INDIRECT OR
28  * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
29  * USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
30  * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
31  * PERFORMANCE OF THIS SOFTWARE.
32  */
33 
34 #include <linux/types.h>
35 #include <linux/module.h>
36 #include <linux/string.h>
37 #include <linux/sunrpc/sched.h>
38 #include <linux/sunrpc/gss_asn1.h>
39 
40 
41 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
42 # define RPCDBG_FACILITY        RPCDBG_AUTH
43 #endif
44 
45 
46 /* TWRITE_STR from gssapiP_generic.h */
47 #define TWRITE_STR(ptr, str, len) \
48 	memcpy((ptr), (char *) (str), (len)); \
49 	(ptr) += (len);
50 
51 /* XXXX this code currently makes the assumption that a mech oid will
52    never be longer than 127 bytes.  This assumption is not inherent in
53    the interfaces, so the code can be fixed if the OSI namespace
54    balloons unexpectedly. */
55 
56 /* Each token looks like this:
57 
58 0x60				tag for APPLICATION 0, SEQUENCE
59 					(constructed, definite-length)
60 	<length>		possible multiple bytes, need to parse/generate
61 	0x06			tag for OBJECT IDENTIFIER
62 		<moid_length>	compile-time constant string (assume 1 byte)
63 		<moid_bytes>	compile-time constant string
64 	<inner_bytes>		the ANY containing the application token
65 					bytes 0,1 are the token type
66 					bytes 2,n are the token data
67 
68 For the purposes of this abstraction, the token "header" consists of
69 the sequence tag and length octets, the mech OID DER encoding, and the
70 first two inner bytes, which indicate the token type.  The token
71 "body" consists of everything else.
72 
73 */
74 
75 static int
76 der_length_size( int length)
77 {
78 	if (length < (1<<7))
79 		return 1;
80 	else if (length < (1<<8))
81 		return 2;
82 #if (SIZEOF_INT == 2)
83 	else
84 		return 3;
85 #else
86 	else if (length < (1<<16))
87 		return 3;
88 	else if (length < (1<<24))
89 		return 4;
90 	else
91 		return 5;
92 #endif
93 }
94 
95 static void
96 der_write_length(unsigned char **buf, int length)
97 {
98 	if (length < (1<<7)) {
99 		*(*buf)++ = (unsigned char) length;
100 	} else {
101 		*(*buf)++ = (unsigned char) (der_length_size(length)+127);
102 #if (SIZEOF_INT > 2)
103 		if (length >= (1<<24))
104 			*(*buf)++ = (unsigned char) (length>>24);
105 		if (length >= (1<<16))
106 			*(*buf)++ = (unsigned char) ((length>>16)&0xff);
107 #endif
108 		if (length >= (1<<8))
109 			*(*buf)++ = (unsigned char) ((length>>8)&0xff);
110 		*(*buf)++ = (unsigned char) (length&0xff);
111 	}
112 }
113 
114 /* returns decoded length, or < 0 on failure.  Advances buf and
115    decrements bufsize */
116 
117 static int
118 der_read_length(unsigned char **buf, int *bufsize)
119 {
120 	unsigned char sf;
121 	int ret;
122 
123 	if (*bufsize < 1)
124 		return -1;
125 	sf = *(*buf)++;
126 	(*bufsize)--;
127 	if (sf & 0x80) {
128 		if ((sf &= 0x7f) > ((*bufsize)-1))
129 			return -1;
130 		if (sf > SIZEOF_INT)
131 			return -1;
132 		ret = 0;
133 		for (; sf; sf--) {
134 			ret = (ret<<8) + (*(*buf)++);
135 			(*bufsize)--;
136 		}
137 	} else {
138 		ret = sf;
139 	}
140 
141 	return ret;
142 }
143 
144 /* returns the length of a token, given the mech oid and the body size */
145 
146 int
147 g_token_size(struct xdr_netobj *mech, unsigned int body_size)
148 {
149 	/* set body_size to sequence contents size */
150 	body_size += 2 + (int) mech->len;         /* NEED overflow check */
151 	return 1 + der_length_size(body_size) + body_size;
152 }
153 
154 EXPORT_SYMBOL_GPL(g_token_size);
155 
156 /* fills in a buffer with the token header.  The buffer is assumed to
157    be the right size.  buf is advanced past the token header */
158 
159 void
160 g_make_token_header(struct xdr_netobj *mech, int body_size, unsigned char **buf)
161 {
162 	*(*buf)++ = 0x60;
163 	der_write_length(buf, 2 + mech->len + body_size);
164 	*(*buf)++ = 0x06;
165 	*(*buf)++ = (unsigned char) mech->len;
166 	TWRITE_STR(*buf, mech->data, ((int) mech->len));
167 }
168 
169 EXPORT_SYMBOL_GPL(g_make_token_header);
170 
171 /*
172  * Given a buffer containing a token, reads and verifies the token,
173  * leaving buf advanced past the token header, and setting body_size
174  * to the number of remaining bytes.  Returns 0 on success,
175  * G_BAD_TOK_HEADER for a variety of errors, and G_WRONG_MECH if the
176  * mechanism in the token does not match the mech argument.  buf and
177  * *body_size are left unmodified on error.
178  */
179 u32
180 g_verify_token_header(struct xdr_netobj *mech, int *body_size,
181 		      unsigned char **buf_in, int toksize)
182 {
183 	unsigned char *buf = *buf_in;
184 	int seqsize;
185 	struct xdr_netobj toid;
186 	int ret = 0;
187 
188 	if ((toksize-=1) < 0)
189 		return G_BAD_TOK_HEADER;
190 	if (*buf++ != 0x60)
191 		return G_BAD_TOK_HEADER;
192 
193 	if ((seqsize = der_read_length(&buf, &toksize)) < 0)
194 		return G_BAD_TOK_HEADER;
195 
196 	if (seqsize != toksize)
197 		return G_BAD_TOK_HEADER;
198 
199 	if ((toksize-=1) < 0)
200 		return G_BAD_TOK_HEADER;
201 	if (*buf++ != 0x06)
202 		return G_BAD_TOK_HEADER;
203 
204 	if ((toksize-=1) < 0)
205 		return G_BAD_TOK_HEADER;
206 	toid.len = *buf++;
207 
208 	if ((toksize-=toid.len) < 0)
209 		return G_BAD_TOK_HEADER;
210 	toid.data = buf;
211 	buf+=toid.len;
212 
213 	if (! g_OID_equal(&toid, mech))
214 		ret = G_WRONG_MECH;
215 
216    /* G_WRONG_MECH is not returned immediately because it's more important
217       to return G_BAD_TOK_HEADER if the token header is in fact bad */
218 
219 	if ((toksize-=2) < 0)
220 		return G_BAD_TOK_HEADER;
221 
222 	if (ret)
223 		return ret;
224 
225 	if (!ret) {
226 		*buf_in = buf;
227 		*body_size = toksize;
228 	}
229 
230 	return ret;
231 }
232 
233 EXPORT_SYMBOL_GPL(g_verify_token_header);
234