1 /*
2  *  linux/net/sunrpc/gss_krb5_unseal.c
3  *
4  *  Adapted from MIT Kerberos 5-1.2.1 lib/gssapi/krb5/k5unseal.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 /*
35  * Copyright (C) 1998 by the FundsXpress, INC.
36  *
37  * All rights reserved.
38  *
39  * Export of this software from the United States of America may require
40  * a specific license from the United States Government.  It is the
41  * responsibility of any person or organization contemplating export to
42  * obtain such a license before exporting.
43  *
44  * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
45  * distribute this software and its documentation for any purpose and
46  * without fee is hereby granted, provided that the above copyright
47  * notice appear in all copies and that both that copyright notice and
48  * this permission notice appear in supporting documentation, and that
49  * the name of FundsXpress. not be used in advertising or publicity pertaining
50  * to distribution of the software without specific, written prior
51  * permission.  FundsXpress makes no representations about the suitability of
52  * this software for any purpose.  It is provided "as is" without express
53  * or implied warranty.
54  *
55  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
56  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
57  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
58  */
59 
60 #include <linux/types.h>
61 #include <linux/slab.h>
62 #include <linux/jiffies.h>
63 #include <linux/sunrpc/gss_krb5.h>
64 #include <linux/crypto.h>
65 
66 #ifdef RPC_DEBUG
67 # define RPCDBG_FACILITY        RPCDBG_AUTH
68 #endif
69 
70 
71 /* read_token is a mic token, and message_buffer is the data that the mic was
72  * supposedly taken over. */
73 
74 u32
75 gss_verify_mic_kerberos(struct gss_ctx *gss_ctx,
76 		struct xdr_buf *message_buffer, struct xdr_netobj *read_token)
77 {
78 	struct krb5_ctx		*ctx = gss_ctx->internal_ctx_id;
79 	int			signalg;
80 	int			sealalg;
81 	char			cksumdata[16];
82 	struct xdr_netobj	md5cksum = {.len = 0, .data = cksumdata};
83 	s32			now;
84 	int			direction;
85 	u32			seqnum;
86 	unsigned char		*ptr = (unsigned char *)read_token->data;
87 	int			bodysize;
88 
89 	dprintk("RPC:       krb5_read_token\n");
90 
91 	if (g_verify_token_header(&ctx->mech_used, &bodysize, &ptr,
92 					read_token->len))
93 		return GSS_S_DEFECTIVE_TOKEN;
94 
95 	if ((ptr[0] != ((KG_TOK_MIC_MSG >> 8) & 0xff)) ||
96 	    (ptr[1] !=  (KG_TOK_MIC_MSG & 0xff)))
97 		return GSS_S_DEFECTIVE_TOKEN;
98 
99 	/* XXX sanity-check bodysize?? */
100 
101 	signalg = ptr[2] + (ptr[3] << 8);
102 	if (signalg != SGN_ALG_DES_MAC_MD5)
103 		return GSS_S_DEFECTIVE_TOKEN;
104 
105 	sealalg = ptr[4] + (ptr[5] << 8);
106 	if (sealalg != SEAL_ALG_NONE)
107 		return GSS_S_DEFECTIVE_TOKEN;
108 
109 	if ((ptr[6] != 0xff) || (ptr[7] != 0xff))
110 		return GSS_S_DEFECTIVE_TOKEN;
111 
112 	if (make_checksum("md5", ptr, 8, message_buffer, 0, &md5cksum))
113 		return GSS_S_FAILURE;
114 
115 	if (krb5_encrypt(ctx->seq, NULL, md5cksum.data, md5cksum.data, 16))
116 		return GSS_S_FAILURE;
117 
118 	if (memcmp(md5cksum.data + 8, ptr + GSS_KRB5_TOK_HDR_LEN, 8))
119 		return GSS_S_BAD_SIG;
120 
121 	/* it got through unscathed.  Make sure the context is unexpired */
122 
123 	now = get_seconds();
124 
125 	if (now > ctx->endtime)
126 		return GSS_S_CONTEXT_EXPIRED;
127 
128 	/* do sequencing checks */
129 
130 	if (krb5_get_seq_num(ctx->seq, ptr + GSS_KRB5_TOK_HDR_LEN, ptr + 8, &direction, &seqnum))
131 		return GSS_S_FAILURE;
132 
133 	if ((ctx->initiate && direction != 0xff) ||
134 	    (!ctx->initiate && direction != 0))
135 		return GSS_S_BAD_SIG;
136 
137 	return GSS_S_COMPLETE;
138 }
139