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 <linux/types.h>
61 #include <linux/jiffies.h>
62 #include <linux/sunrpc/gss_krb5.h>
63 #include <linux/crypto.h>
64 
65 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
66 # define RPCDBG_FACILITY        RPCDBG_AUTH
67 #endif
68 
69 
70 /* read_token is a mic token, and message_buffer is the data that the mic was
71  * supposedly taken over. */
72 
73 static u32
74 gss_verify_mic_v1(struct krb5_ctx *ctx,
75 		struct xdr_buf *message_buffer, struct xdr_netobj *read_token)
76 {
77 	int			signalg;
78 	int			sealalg;
79 	char			cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
80 	struct xdr_netobj	md5cksum = {.len = sizeof(cksumdata),
81 					    .data = cksumdata};
82 	s32			now;
83 	int			direction;
84 	u32			seqnum;
85 	unsigned char		*ptr = (unsigned char *)read_token->data;
86 	int			bodysize;
87 	u8			*cksumkey;
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 != ctx->gk5e->signalg)
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 (ctx->gk5e->keyed_cksum)
113 		cksumkey = ctx->cksum;
114 	else
115 		cksumkey = NULL;
116 
117 	if (make_checksum(ctx, ptr, 8, message_buffer, 0,
118 			  cksumkey, KG_USAGE_SIGN, &md5cksum))
119 		return GSS_S_FAILURE;
120 
121 	if (memcmp(md5cksum.data, ptr + GSS_KRB5_TOK_HDR_LEN,
122 					ctx->gk5e->cksumlength))
123 		return GSS_S_BAD_SIG;
124 
125 	/* it got through unscathed.  Make sure the context is unexpired */
126 
127 	now = get_seconds();
128 
129 	if (now > ctx->endtime)
130 		return GSS_S_CONTEXT_EXPIRED;
131 
132 	/* do sequencing checks */
133 
134 	if (krb5_get_seq_num(ctx, ptr + GSS_KRB5_TOK_HDR_LEN, ptr + 8,
135 			     &direction, &seqnum))
136 		return GSS_S_FAILURE;
137 
138 	if ((ctx->initiate && direction != 0xff) ||
139 	    (!ctx->initiate && direction != 0))
140 		return GSS_S_BAD_SIG;
141 
142 	return GSS_S_COMPLETE;
143 }
144 
145 static u32
146 gss_verify_mic_v2(struct krb5_ctx *ctx,
147 		struct xdr_buf *message_buffer, struct xdr_netobj *read_token)
148 {
149 	char cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
150 	struct xdr_netobj cksumobj = {.len = sizeof(cksumdata),
151 				      .data = cksumdata};
152 	s32 now;
153 	u8 *ptr = read_token->data;
154 	u8 *cksumkey;
155 	u8 flags;
156 	int i;
157 	unsigned int cksum_usage;
158 	__be16 be16_ptr;
159 
160 	dprintk("RPC:       %s\n", __func__);
161 
162 	memcpy(&be16_ptr, (char *) ptr, 2);
163 	if (be16_to_cpu(be16_ptr) != KG2_TOK_MIC)
164 		return GSS_S_DEFECTIVE_TOKEN;
165 
166 	flags = ptr[2];
167 	if ((!ctx->initiate && (flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)) ||
168 	    (ctx->initiate && !(flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)))
169 		return GSS_S_BAD_SIG;
170 
171 	if (flags & KG2_TOKEN_FLAG_SEALED) {
172 		dprintk("%s: token has unexpected sealed flag\n", __func__);
173 		return GSS_S_FAILURE;
174 	}
175 
176 	for (i = 3; i < 8; i++)
177 		if (ptr[i] != 0xff)
178 			return GSS_S_DEFECTIVE_TOKEN;
179 
180 	if (ctx->initiate) {
181 		cksumkey = ctx->acceptor_sign;
182 		cksum_usage = KG_USAGE_ACCEPTOR_SIGN;
183 	} else {
184 		cksumkey = ctx->initiator_sign;
185 		cksum_usage = KG_USAGE_INITIATOR_SIGN;
186 	}
187 
188 	if (make_checksum_v2(ctx, ptr, GSS_KRB5_TOK_HDR_LEN, message_buffer, 0,
189 			     cksumkey, cksum_usage, &cksumobj))
190 		return GSS_S_FAILURE;
191 
192 	if (memcmp(cksumobj.data, ptr + GSS_KRB5_TOK_HDR_LEN,
193 				ctx->gk5e->cksumlength))
194 		return GSS_S_BAD_SIG;
195 
196 	/* it got through unscathed.  Make sure the context is unexpired */
197 	now = get_seconds();
198 	if (now > ctx->endtime)
199 		return GSS_S_CONTEXT_EXPIRED;
200 
201 	/*
202 	 * NOTE: the sequence number at ptr + 8 is skipped, rpcsec_gss
203 	 * doesn't want it checked; see page 6 of rfc 2203.
204 	 */
205 
206 	return GSS_S_COMPLETE;
207 }
208 
209 u32
210 gss_verify_mic_kerberos(struct gss_ctx *gss_ctx,
211 			struct xdr_buf *message_buffer,
212 			struct xdr_netobj *read_token)
213 {
214 	struct krb5_ctx *ctx = gss_ctx->internal_ctx_id;
215 
216 	switch (ctx->enctype) {
217 	default:
218 		BUG();
219 	case ENCTYPE_DES_CBC_RAW:
220 	case ENCTYPE_DES3_CBC_RAW:
221 	case ENCTYPE_ARCFOUR_HMAC:
222 		return gss_verify_mic_v1(ctx, message_buffer, read_token);
223 	case ENCTYPE_AES128_CTS_HMAC_SHA1_96:
224 	case ENCTYPE_AES256_CTS_HMAC_SHA1_96:
225 		return gss_verify_mic_v2(ctx, message_buffer, read_token);
226 	}
227 }
228