3 * Encrypting keys with passphrases
5 * (c) 1999 Straylight/Edgeware
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of Catacomb.
12 * Catacomb is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU Library General Public License as
14 * published by the Free Software Foundation; either version 2 of the
15 * License, or (at your option) any later version.
17 * Catacomb is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU Library General Public License for more details.
22 * You should have received a copy of the GNU Library General Public
23 * License along with Catacomb; if not, write to the Free
24 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
28 /*----- Header files ------------------------------------------------------*/
30 #include <mLib/dstr.h>
34 #include "passphrase.h"
37 #include "blowfish-cbc.h"
39 #include "rmd160-mgf.h"
40 #include "rmd160-hmac.h"
42 /*----- Main code ---------------------------------------------------------*/
46 * Choose a random 160-bit string %$R$%. Take the passphrase %$P$%, and
47 * the message %$m$%. Now, compute %$K_E \cat K_T = H(R \cat P)$%,
48 * %$y_0 = E_{K_E}(m)$% and %$\tau = T_{K_T}(y_0)$%. The ciphertext is
49 * %$y = N \cat \tau \cat y_0$%.
51 * This is not the original format. The original format was insecure, and
52 * has been replaced incompatibly.
55 /* --- @key_lock@ --- *
57 * Arguments: @key_data **kt@ = where to store the destination pointer
58 * @key_data *k@ = source key data block or null to use @*kt@
59 * @const void *e@ = secret to encrypt key with
60 * @size_t esz@ = size of the secret
64 * Use: Encrypts a key data block using a secret.
67 void key_lock(key_data **kt, key_data *k, const void *e, size_t esz)
70 octet b[RMD160_HASHSZ * 2];
78 /* --- Sanity check --- */
80 if (k) key_incref(k); else k = *kt;
81 assert(((void)"Key data is already encrypted",
82 (k->e & KF_ENCMASK) != KENC_ENCRYPT));
84 /* --- Format the stuff in the buffer --- */
86 DENSURE(&d, RMD160_HASHSZ * 2);
87 rand_get(RAND_GLOBAL, d.buf, RMD160_HASHSZ);
88 d.len += RMD160_HASHSZ * 2;
90 m = (octet *)d.buf + RMD160_HASHSZ * 2;
91 msz = d.len - RMD160_HASHSZ * 2;
93 /* --- Hash the passphrase to make a key --- */
95 rmd160_mgfkeybegin(&r);
96 rmd160_mgfkeyadd(&r, d.buf, RMD160_HASHSZ);
97 rmd160_mgfkeyadd(&r, e, esz);
98 rmd160_mgfencrypt(&r, 0, b, sizeof(b));
101 /* --- Encrypt the plaintext --- */
103 blowfish_cbcinit(&c, b, RMD160_HASHSZ, 0);
104 blowfish_cbcencrypt(&c, m, m, msz);
107 /* --- MAC the ciphertext --- */
109 rmd160_hmacinit(&mk, b + RMD160_HASHSZ, RMD160_HASHSZ);
110 rmd160_macinit(&mc, &mk);
111 rmd160_machash(&mc, m, msz);
112 rmd160_macdone(&mc, d.buf + RMD160_HASHSZ);
119 *kt = key_newencrypted(0, d.buf, d.len);
124 /* --- @key_unlock@ --- *
126 * Arguments: @key_data **kt@ = where to store the destination pointer
127 * @key_data *k@ = source key data block or null to use @*kt@
128 * @const void *e@ = secret to decrypt the block with
129 * @size_t esz@ = size of the secret
131 * Returns: Zero for success, or a @KERR_@ error code.
133 * Use: Unlocks a key using a secret.
136 int key_unlock(key_data **kt, key_data *k, const void *e, size_t esz)
138 octet b[RMD160_HASHSZ * 2];
149 /* --- Sanity check --- */
151 if (!k) { k = *kt; drop = 1; }
152 assert(((void)"Key data isn't encrypted",
153 (k->e & KF_ENCMASK) == KENC_ENCRYPT));
155 /* --- Check the size --- */
157 if (k->u.k.sz < RMD160_HASHSZ * 2)
158 return (KERR_MALFORMED);
159 sz = k->u.k.sz - RMD160_HASHSZ * 2;
161 /* --- Hash the passphrase to make a key --- */
163 rmd160_mgfkeybegin(&r);
164 rmd160_mgfkeyadd(&r, k->u.k.k, RMD160_HASHSZ);
165 rmd160_mgfkeyadd(&r, e, esz);
166 rmd160_mgfencrypt(&r, 0, b, sizeof(b));
169 /* --- Verify the MAC --- */
171 rmd160_hmacinit(&mk, b + RMD160_HASHSZ, RMD160_HASHSZ);
172 rmd160_macinit(&mc, &mk);
173 rmd160_machash(&mc, k->u.k.k + RMD160_HASHSZ * 2, sz);
174 rmd160_macdone(&mc, b + RMD160_HASHSZ);
175 if (memcmp(b + RMD160_HASHSZ, k->u.k.k + RMD160_HASHSZ,
176 RMD160_HASHSZ) != 0) {
183 /* --- Allocate a destination buffer --- */
187 /* --- Decrypt the key data --- */
189 blowfish_cbcinit(&c, b, RMD160_HASHSZ, 0);
190 blowfish_cbcdecrypt(&c, k->u.k.k + RMD160_HASHSZ * 2, p, sz);
193 /* --- Decode the key data into the destination buffer --- */
195 if ((kd = key_decode(p, sz)) == 0) {
204 if (drop) key_drop(k);
207 /* --- Tidy up if things went wrong --- */
215 /* --- @key_plock@ --- *
217 * Arguments: @key_data **kt@ = where to store the destination pointer
218 * @key_data *k@ = source key data block or null to use @*kt@
219 * @const char *tag@ = tag to use for passphrase
221 * Returns: Zero if successful, a @KERR@ error code on failure.
223 * Use: Locks a key by encrypting it with a passphrase.
226 int key_plock(key_data **kt, key_data *k, const char *tag)
230 if (passphrase_read(tag, PMODE_VERIFY, buf, sizeof(buf)))
232 key_lock(kt, k, buf, strlen(buf));
237 /* --- @key_punlock@ --- *
239 * Arguments: @key_data **kt@ = where to store the destination pointer
240 * @key_data *k@ = source key data block or null to use @*kt@
241 * @const char *tag@ = tag to use for passphrase
243 * Returns: Zero if it worked, a @KERR_@ error code on failure.
245 * Use: Unlocks a passphrase-locked key.
248 int key_punlock(key_data **kt, key_data *k, const char *tag)
253 if (passphrase_read(tag, PMODE_READ, buf, sizeof(buf)))
255 rc = key_unlock(kt, k, buf, strlen(buf));
257 if (rc == KERR_BADPASS || !k)
258 passphrase_cancel(tag);
262 /*----- That's all, folks -------------------------------------------------*/