1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
|
/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
* Copyright (C) 1998 by the FundsXpress, INC.
*
* All rights reserved.
*
* Export of this software from the United States of America may require
* a specific license from the United States Government. It is the
* responsibility of any person or organization contemplating export to
* obtain such a license before exporting.
*
* WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
* distribute this software and its documentation for any purpose and
* without fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright notice and
* this permission notice appear in supporting documentation, and that
* the name of FundsXpress. not be used in advertising or publicity pertaining
* to distribution of the software without specific, written prior
* permission. FundsXpress makes no representations about the suitability of
* this software for any purpose. It is provided "as is" without express
* or implied warranty.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
#include "k5-int.h"
#include "dk.h"
#define K5CLENGTH 5 /* 32 bit net byte order integer + one byte seed */
static krb5_error_code
krb5_dk_decrypt_maybe_trunc_hmac(const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
krb5_key key,
krb5_keyusage usage,
const krb5_data *ivec,
const krb5_data *input,
krb5_data *output,
size_t hmacsize,
int ivec_mode);
krb5_error_code
krb5int_dk_decrypt(const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
krb5_key key, krb5_keyusage usage,
const krb5_data *ivec, const krb5_data *input,
krb5_data *output)
{
return krb5_dk_decrypt_maybe_trunc_hmac(enc, hash, key, usage,
ivec, input, output, 0, 0);
}
krb5_error_code
krb5int_aes_dk_decrypt(const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
krb5_key key, krb5_keyusage usage,
const krb5_data *ivec, const krb5_data *input,
krb5_data *output)
{
return krb5_dk_decrypt_maybe_trunc_hmac(enc, hash, key, usage,
ivec, input, output, 96 / 8, 1);
}
static krb5_error_code
krb5_dk_decrypt_maybe_trunc_hmac(const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
krb5_key key, krb5_keyusage usage,
const krb5_data *ivec, const krb5_data *input,
krb5_data *output, size_t hmacsize,
int ivec_mode)
{
krb5_error_code ret;
size_t hashsize, blocksize, enclen, plainlen;
unsigned char *plaindata = NULL, *cksum = NULL, *cn;
krb5_key ke = NULL, ki = NULL;
krb5_data d1, d2;
unsigned char constantdata[K5CLENGTH];
hashsize = hash->hashsize;
blocksize = enc->block_size;
if (hmacsize == 0)
hmacsize = hashsize;
else if (hmacsize > hashsize)
return KRB5KRB_AP_ERR_BAD_INTEGRITY;
enclen = input->length - hmacsize;
/* Allocate and set up ciphertext and to-be-derived keys. */
plaindata = k5alloc(enclen, &ret);
if (ret != 0)
goto cleanup;
cksum = k5alloc(hashsize, &ret);
if (ret != 0)
goto cleanup;
/* Derive the keys. */
d1.data = (char *) constantdata;
d1.length = K5CLENGTH;
store_32_be(usage, constantdata);
d1.data[4] = (char) 0xAA;
ret = krb5int_derive_key(enc, key, &ke, &d1);
if (ret != 0)
goto cleanup;
d1.data[4] = 0x55;
ret = krb5int_derive_key(enc, key, &ki, &d1);
if (ret != 0)
goto cleanup;
/* decrypt the ciphertext */
d1.length = enclen;
d1.data = input->data;
d2.length = enclen;
d2.data = (char *) plaindata;
ret = (*enc->decrypt)(ke, ivec, &d1, &d2);
if (ret != 0)
goto cleanup;
if (ivec != NULL && ivec->length == blocksize) {
if (ivec_mode == 0)
cn = (unsigned char *) d1.data + d1.length - blocksize;
else if (ivec_mode == 1) {
int nblocks = (d1.length + blocksize - 1) / blocksize;
cn = (unsigned char *) d1.data + blocksize * (nblocks - 2);
} else
abort();
} else
cn = NULL;
/* Verify the hash. */
d1.length = hashsize;
d1.data = (char *) cksum;
ret = krb5int_hmac(hash, ki, 1, &d2, &d1);
if (ret != 0)
goto cleanup;
if (memcmp(cksum, input->data+enclen, hmacsize) != 0) {
ret = KRB5KRB_AP_ERR_BAD_INTEGRITY;
goto cleanup;
}
/*
* Because this encoding isn't self-describing wrt length, the
* best we can do here is to compute the length minus the
* confounder.
*/
plainlen = enclen - blocksize;
if (output->length < plainlen)
return KRB5_BAD_MSIZE;
output->length = plainlen;
memcpy(output->data, d2.data+blocksize, output->length);
if (cn != NULL)
memcpy(ivec->data, cn, blocksize);
cleanup:
krb5_k_free_key(NULL, ke);
krb5_k_free_key(NULL, ki);
zapfree(plaindata, enclen);
zapfree(cksum, hashsize);
return ret;
}
|