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) 2000-2008 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 <crypto/algapi.h>
61 #include <linux/types.h>
62 #include <linux/jiffies.h>
63 #include <linux/sunrpc/gss_krb5.h>
64 #include <linux/crypto.h>
65 
66 #include "gss_krb5_internal.h"
67 
68 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
69 # define RPCDBG_FACILITY        RPCDBG_AUTH
70 #endif
71 
72 u32
73 gss_krb5_verify_mic_v2(struct krb5_ctx *ctx, struct xdr_buf *message_buffer,
74 		       struct xdr_netobj *read_token)
75 {
76 	struct crypto_ahash *tfm = ctx->initiate ?
77 				   ctx->acceptor_sign : ctx->initiator_sign;
78 	char cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
79 	struct xdr_netobj cksumobj = {
80 		.len	= ctx->gk5e->cksumlength,
81 		.data	= cksumdata,
82 	};
83 	u8 *ptr = read_token->data;
84 	__be16 be16_ptr;
85 	time64_t now;
86 	u8 flags;
87 	int i;
88 
89 	dprintk("RPC:       %s\n", __func__);
90 
91 	memcpy(&be16_ptr, (char *) ptr, 2);
92 	if (be16_to_cpu(be16_ptr) != KG2_TOK_MIC)
93 		return GSS_S_DEFECTIVE_TOKEN;
94 
95 	flags = ptr[2];
96 	if ((!ctx->initiate && (flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)) ||
97 	    (ctx->initiate && !(flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)))
98 		return GSS_S_BAD_SIG;
99 
100 	if (flags & KG2_TOKEN_FLAG_SEALED) {
101 		dprintk("%s: token has unexpected sealed flag\n", __func__);
102 		return GSS_S_FAILURE;
103 	}
104 
105 	for (i = 3; i < 8; i++)
106 		if (ptr[i] != 0xff)
107 			return GSS_S_DEFECTIVE_TOKEN;
108 
109 	if (gss_krb5_checksum(tfm, ptr, GSS_KRB5_TOK_HDR_LEN,
110 			      message_buffer, 0, &cksumobj))
111 		return GSS_S_FAILURE;
112 
113 	if (memcmp(cksumobj.data, ptr + GSS_KRB5_TOK_HDR_LEN,
114 				ctx->gk5e->cksumlength))
115 		return GSS_S_BAD_SIG;
116 
117 	/* it got through unscathed.  Make sure the context is unexpired */
118 	now = ktime_get_real_seconds();
119 	if (now > ctx->endtime)
120 		return GSS_S_CONTEXT_EXPIRED;
121 
122 	/*
123 	 * NOTE: the sequence number at ptr + 8 is skipped, rpcsec_gss
124 	 * doesn't want it checked; see page 6 of rfc 2203.
125 	 */
126 
127 	return GSS_S_COMPLETE;
128 }
129