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gss_krb5_unseal.c
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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 <[email protected]>
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
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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 #ifdef RPC_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  u64 seqnum;
154  u8 *ptr = read_token->data;
155  u8 *cksumkey;
156  u8 flags;
157  int i;
158  unsigned int cksum_usage;
159 
160  dprintk("RPC: %s\n", __func__);
161 
162  if (be16_to_cpu(*((__be16 *)ptr)) != KG2_TOK_MIC)
163  return GSS_S_DEFECTIVE_TOKEN;
164 
165  flags = ptr[2];
166  if ((!ctx->initiate && (flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)) ||
167  (ctx->initiate && !(flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)))
168  return GSS_S_BAD_SIG;
169 
170  if (flags & KG2_TOKEN_FLAG_SEALED) {
171  dprintk("%s: token has unexpected sealed flag\n", __func__);
172  return GSS_S_FAILURE;
173  }
174 
175  for (i = 3; i < 8; i++)
176  if (ptr[i] != 0xff)
177  return GSS_S_DEFECTIVE_TOKEN;
178 
179  if (ctx->initiate) {
180  cksumkey = ctx->acceptor_sign;
181  cksum_usage = KG_USAGE_ACCEPTOR_SIGN;
182  } else {
183  cksumkey = ctx->initiator_sign;
184  cksum_usage = KG_USAGE_INITIATOR_SIGN;
185  }
186 
187  if (make_checksum_v2(ctx, ptr, GSS_KRB5_TOK_HDR_LEN, message_buffer, 0,
188  cksumkey, cksum_usage, &cksumobj))
189  return GSS_S_FAILURE;
190 
191  if (memcmp(cksumobj.data, ptr + GSS_KRB5_TOK_HDR_LEN,
192  ctx->gk5e->cksumlength))
193  return GSS_S_BAD_SIG;
194 
195  /* it got through unscathed. Make sure the context is unexpired */
196  now = get_seconds();
197  if (now > ctx->endtime)
198  return GSS_S_CONTEXT_EXPIRED;
199 
200  /* do sequencing checks */
201 
202  seqnum = be64_to_cpup((__be64 *)ptr + 8);
203 
204  return GSS_S_COMPLETE;
205 }
206 
207 u32
208 gss_verify_mic_kerberos(struct gss_ctx *gss_ctx,
209  struct xdr_buf *message_buffer,
210  struct xdr_netobj *read_token)
211 {
212  struct krb5_ctx *ctx = gss_ctx->internal_ctx_id;
213 
214  switch (ctx->enctype) {
215  default:
216  BUG();
217  case ENCTYPE_DES_CBC_RAW:
218  case ENCTYPE_DES3_CBC_RAW:
219  case ENCTYPE_ARCFOUR_HMAC:
220  return gss_verify_mic_v1(ctx, message_buffer, read_token);
221  case ENCTYPE_AES128_CTS_HMAC_SHA1_96:
222  case ENCTYPE_AES256_CTS_HMAC_SHA1_96:
223  return gss_verify_mic_v2(ctx, message_buffer, read_token);
224  }
225 }
226 
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