5 * Encrypting keys with passphrases
7 * (c) 1999 Straylight/Edgeware
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of Catacomb.
14 * Catacomb is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU Library General Public License as
16 * published by the Free Software Foundation; either version 2 of the
17 * License, or (at your option) any later version.
19 * Catacomb is distributed in the hope that it will be useful,
20 * but WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 * GNU Library General Public License for more details.
24 * You should have received a copy of the GNU Library General Public
25 * License along with Catacomb; if not, write to the Free
26 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
30 /*----- Header files ------------------------------------------------------*/
32 #include <mLib/dstr.h>
36 #include "passphrase.h"
39 #include "blowfish-cbc.h"
41 #include "rmd160-mgf.h"
42 #include "rmd160-hmac.h"
44 /*----- Main code ---------------------------------------------------------*/
48 * Choose a random 160-bit string %$R$%. Take the passphrase %$P$%, and
49 * the message %$m$%. Now, compute %$K_E \cat K_T = H(R \cat P)$%,
50 * %$y_0 = E_{K_E}(m)$% and %$\tau = T_{K_T}(y_0)$%. The ciphertext is
51 * %$y = N \cat \tau \cat y_0$%.
53 * This is not the original format. The original format was insecure, and
54 * has been replaced incompatibly.
57 /* --- @key_lock@ --- *
59 * Arguments: @key_data *kt@ = destination block
60 * @key_data *k@ = source key data block
61 * @const void *e@ = secret to encrypt key with
62 * @size_t esz@ = size of the secret
66 * Use: Encrypts a key data block using a secret.
69 void key_lock(key_data
*kt
, key_data
*k
, const void *e
, size_t esz
)
72 octet b
[RMD160_HASHSZ
* 2];
80 /* --- Sanity check --- */
82 assert(((void)"Key data is already encrypted",
83 (k
->e
& KF_ENCMASK
) != KENC_ENCRYPT
));
85 /* --- Format the stuff in the buffer --- */
87 DENSURE(&d
, RMD160_HASHSZ
* 2);
88 rand_get(RAND_GLOBAL
, d
.buf
, RMD160_HASHSZ
);
89 d
.len
+= RMD160_HASHSZ
* 2;
93 m
= (octet
*)d
.buf
+ RMD160_HASHSZ
* 2;
94 msz
= d
.len
- RMD160_HASHSZ
* 2;
96 /* --- Hash the passphrase to make a key --- */
98 rmd160_mgfkeybegin(&r
);
99 rmd160_mgfkeyadd(&r
, d
.buf
, RMD160_HASHSZ
);
100 rmd160_mgfkeyadd(&r
, e
, esz
);
101 rmd160_mgfencrypt(&r
, 0, b
, sizeof(b
));
104 /* --- Encrypt the plaintext --- */
106 blowfish_cbcinit(&c
, b
, RMD160_HASHSZ
, 0);
107 blowfish_cbcencrypt(&c
, m
, m
, msz
);
110 /* --- MAC the ciphertext --- */
112 rmd160_hmacinit(&mk
, b
+ RMD160_HASHSZ
, RMD160_HASHSZ
);
113 rmd160_macinit(&mc
, &mk
);
114 rmd160_machash(&mc
, m
, msz
);
115 rmd160_macdone(&mc
, d
.buf
+ RMD160_HASHSZ
);
122 key_encrypted(kt
, d
.buf
, d
.len
);
126 /* --- @key_unlock@ --- *
128 * Arguments: @key_data *kt@ = target block
129 * @key_data *k@ = source key data block
130 * @const void *e@ = secret to decrypt the block with
131 * @size_t esz@ = size of the secret
133 * Returns: Zero for success, or a @KERR_@ error code.
135 * Use: Unlocks a key using a secret.
138 int key_unlock(key_data
*kt
, key_data
*k
, const void *e
, size_t esz
)
140 octet b
[RMD160_HASHSZ
* 2];
149 /* --- Sanity check --- */
151 assert(((void)"Key data isn't encrypted",
152 (k
->e
& KF_ENCMASK
) == KENC_ENCRYPT
));
154 /* --- Check the size --- */
156 if (k
->u
.k
.sz
< RMD160_HASHSZ
* 2)
157 return (KERR_MALFORMED
);
158 sz
= k
->u
.k
.sz
- RMD160_HASHSZ
* 2;
160 /* --- Hash the passphrase to make a key --- */
162 rmd160_mgfkeybegin(&r
);
163 rmd160_mgfkeyadd(&r
, k
->u
.k
.k
, RMD160_HASHSZ
);
164 rmd160_mgfkeyadd(&r
, e
, esz
);
165 rmd160_mgfencrypt(&r
, 0, b
, sizeof(b
));
168 /* --- Verify the MAC --- */
170 rmd160_hmacinit(&mk
, b
+ RMD160_HASHSZ
, RMD160_HASHSZ
);
171 rmd160_macinit(&mc
, &mk
);
172 rmd160_machash(&mc
, k
->u
.k
.k
+ RMD160_HASHSZ
* 2, sz
);
173 rmd160_macdone(&mc
, b
+ RMD160_HASHSZ
);
174 if (memcmp(b
+ RMD160_HASHSZ
, k
->u
.k
.k
+ RMD160_HASHSZ
,
175 RMD160_HASHSZ
) != 0) {
182 /* --- Allocate a destination buffer --- */
186 /* --- Decrypt the key data --- */
188 blowfish_cbcinit(&c
, b
, RMD160_HASHSZ
, 0);
189 blowfish_cbcdecrypt(&c
, k
->u
.k
.k
+ RMD160_HASHSZ
* 2, p
, sz
);
192 /* --- Decode the key data into the destination buffer --- */
196 if (key_decode(p
, sz
, kt
)) {
206 /* --- Tidy up if things went wrong --- */
214 /* --- @key_plock@ --- *
216 * Arguments: @const char *tag@ = tag to use for passphrase
217 * @key_data *k@ = source key data block
218 * @key_data *kt@ = target key data block
220 * Returns: Zero if successful, a @KERR@ error code on failure.
222 * Use: Locks a key by encrypting it with a passphrase.
225 int key_plock(const char *tag
, key_data
*k
, key_data
*kt
)
229 if (passphrase_read(tag
, PMODE_VERIFY
, buf
, sizeof(buf
)))
231 key_lock(kt
, k
, buf
, strlen(buf
));
236 /* --- @key_punlock@ --- *
238 * Arguments: @const char *tag@ = tag to use for passphrase
239 * @key_data *k@ = source key data block
240 * @key_data *kt@ = target key data block
242 * Returns: Zero if it worked, a @KERR_@ error code on failure.
244 * Use: Unlocks a passphrase-locked key.
247 int key_punlock(const char *tag
, key_data
*k
, key_data
*kt
)
252 if (passphrase_read(tag
, PMODE_READ
, buf
, sizeof(buf
)))
254 rc
= key_unlock(kt
, k
, buf
, strlen(buf
));
256 if (rc
== KERR_BADPASS
|| k
== kt
)
257 passphrase_cancel(tag
);
261 /*----- That's all, folks -------------------------------------------------*/