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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: key-pass.c,v 1.3 2004/03/27 00:04:19 mdw Exp $ |
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4 | * |
5 | * Encrypting keys with passphrases |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of Catacomb. |
13 | * |
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. |
18 | * |
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. |
23 | * |
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, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: key-pass.c,v $ |
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33 | * Revision 1.3 2004/03/27 00:04:19 mdw |
34 | * INCOMPATIBLE CHANGE. Use proper authentication on encrypted keys. |
35 | * |
bbded534 |
36 | * Revision 1.2 2000/06/17 11:26:35 mdw |
37 | * `rand_getgood' is deprecated. |
38 | * |
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39 | * Revision 1.1 1999/12/22 15:47:48 mdw |
40 | * Major key-management revision. |
41 | * |
42 | */ |
43 | |
44 | /*----- Header files ------------------------------------------------------*/ |
45 | |
46 | #include <mLib/dstr.h> |
47 | |
48 | #include "key.h" |
49 | #include "paranoia.h" |
50 | #include "passphrase.h" |
51 | #include "rand.h" |
52 | |
53 | #include "blowfish-cbc.h" |
54 | #include "rmd160.h" |
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55 | #include "rmd160-mgf.h" |
56 | #include "rmd160-hmac.h" |
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57 | |
58 | /*----- Main code ---------------------------------------------------------*/ |
59 | |
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60 | /* --- Format --- * |
61 | * |
62 | * Choose a random 160-bit string %$R$%. Take the passphrase %$P$%, and |
63 | * the message %$m$%. Now, compute %$K_E \cat K_T = H(R \cat P)$%, |
64 | * %$y_0 = E_{K_E}(m)$% and %$\tau = T_{K_T}(y_0)$%. The ciphertext is |
65 | * %$y = N \cat \tau \cat y_0$%. |
66 | * |
67 | * This is not the original format. The original format was insecure, and |
68 | * has been replaced incompatibly. |
69 | */ |
70 | |
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71 | /* --- @key_plock@ --- * |
72 | * |
73 | * Arguments: @const char *tag@ = tag to use for passphrase |
74 | * @key_data *k@ = source key data block |
75 | * @key_data *kt@ = target key data block |
76 | * |
77 | * Returns: Zero if successful, nonzero if there was a problem. |
78 | * |
79 | * Use: Locks a key by encrypting it with a passphrase. |
80 | */ |
81 | |
82 | int key_plock(const char *tag, key_data *k, key_data *kt) |
83 | { |
84 | dstr d = DSTR_INIT; |
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85 | octet b[RMD160_HASHSZ * 2]; |
86 | octet *m; |
87 | size_t msz; |
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88 | char buf[256]; |
89 | |
90 | /* --- Sanity check --- */ |
91 | |
92 | assert(((void)"Key data is already encrypted", |
93 | (k->e & KF_ENCMASK) != KENC_ENCRYPT)); |
94 | |
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95 | /* --- Format the stuff in the buffer --- */ |
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96 | |
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97 | DENSURE(&d, RMD160_HASHSZ * 2); |
98 | rand_get(RAND_GLOBAL, d.buf, RMD160_HASHSZ); |
99 | d.len += RMD160_HASHSZ * 2; |
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100 | key_encode(k, &d, 0); |
101 | if (k == kt) |
102 | key_destroy(k); |
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103 | m = (octet *)d.buf + RMD160_HASHSZ * 2; |
104 | msz = d.len - RMD160_HASHSZ * 2; |
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105 | |
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106 | /* --- Read the passphrase --- */ |
107 | |
108 | if (passphrase_read(tag, PMODE_VERIFY, buf, sizeof(buf))) { |
109 | dstr_destroy(&d); |
110 | return (-1); |
111 | } |
112 | |
113 | /* --- Hash the passphrase to make a key --- */ |
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114 | |
115 | { |
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116 | rmd160_mgfctx r; |
117 | rmd160_mgfkeybegin(&r); |
118 | rmd160_mgfkeyadd(&r, d.buf, RMD160_HASHSZ); |
119 | rmd160_mgfkeyadd(&r, buf, strlen(buf)); |
120 | rmd160_mgfencrypt(&r, 0, b, sizeof(b)); |
121 | BURN(r); |
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122 | BURN(buf); |
123 | } |
124 | |
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125 | /* --- Encrypt the plaintext --- */ |
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126 | |
127 | { |
128 | blowfish_cbcctx c; |
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129 | blowfish_cbcinit(&c, b, RMD160_HASHSZ, 0); |
130 | blowfish_cbcencrypt(&c, m, m, msz); |
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131 | BURN(c); |
132 | } |
133 | |
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134 | /* --- MAC the ciphertext --- */ |
135 | |
136 | { |
137 | rmd160_mackey mk; |
138 | rmd160_macctx mc; |
139 | rmd160_hmacinit(&mk, b + RMD160_HASHSZ, RMD160_HASHSZ); |
140 | rmd160_macinit(&mc, &mk); |
141 | rmd160_machash(&mc, m, msz); |
142 | rmd160_macdone(&mc, d.buf + RMD160_HASHSZ); |
143 | BURN(mk); |
144 | BURN(mc); |
145 | } |
146 | |
147 | /* --- Done --- */ |
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148 | |
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149 | BURN(b); |
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150 | key_encrypted(kt, d.buf, d.len); |
151 | dstr_destroy(&d); |
152 | return (0); |
153 | } |
154 | |
155 | /* --- @key_punlock@ --- * |
156 | * |
157 | * Arguments: @const char *tag@ = tag to use for passphrase |
158 | * @key_data *k@ = source key data block |
159 | * @key_data *kt@ = target key data block |
160 | * |
161 | * Returns: Zero if it worked, nonzero if it didn't. |
162 | * |
163 | * Use: Unlocks a passphrase-locked key. |
164 | */ |
165 | |
166 | int key_punlock(const char *tag, key_data *k, key_data *kt) |
167 | { |
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168 | octet b[RMD160_HASHSZ * 2]; |
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169 | char buf[256]; |
170 | octet *p; |
171 | size_t sz; |
172 | |
173 | /* --- Sanity check --- */ |
174 | |
175 | assert(((void)"Key data isn't encrypted", |
176 | (k->e & KF_ENCMASK) == KENC_ENCRYPT)); |
177 | |
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178 | /* --- Allocate a destination buffer --- */ |
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179 | |
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180 | if (k->u.k.sz < RMD160_HASHSZ * 2) |
181 | return (-1);; |
182 | sz = k->u.k.sz - RMD160_HASHSZ * 2; |
183 | p = xmalloc(k->u.k.sz); |
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184 | |
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185 | /* --- Fetch the passphrase --- */ |
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186 | |
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187 | if (passphrase_read(tag, PMODE_READ, buf, sizeof(buf))) |
188 | goto fail; |
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189 | |
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190 | /* --- Hash the passphrase to make a key --- */ |
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191 | |
192 | { |
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193 | rmd160_mgfctx r; |
194 | rmd160_mgfkeybegin(&r); |
195 | rmd160_mgfkeyadd(&r, k->u.k.k, RMD160_HASHSZ); |
196 | rmd160_mgfkeyadd(&r, buf, strlen(buf)); |
197 | rmd160_mgfencrypt(&r, 0, b, sizeof(b)); |
198 | BURN(r); |
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199 | BURN(buf); |
200 | } |
201 | |
202 | /* --- Decrypt the key data --- */ |
203 | |
204 | { |
205 | blowfish_cbcctx c; |
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206 | blowfish_cbcinit(&c, b, sizeof(b), 0); |
207 | blowfish_cbcdecrypt(&c, k->u.k.k + RMD160_HASHSZ, p, sz); |
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208 | BURN(c); |
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209 | } |
210 | |
211 | /* --- Verify the MAC --- */ |
212 | |
213 | { |
214 | rmd160_mackey mk; |
215 | rmd160_macctx mc; |
216 | rmd160_hmacinit(&mk, b + RMD160_HASHSZ, RMD160_HASHSZ); |
217 | rmd160_macinit(&mc, &mk); |
218 | rmd160_machash(&mc, p, sz); |
219 | rmd160_macdone(&mc, b); |
220 | if (memcmp(b, k->u.k.k + RMD160_HASHSZ, RMD160_HASHSZ) != 0) { |
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221 | passphrase_cancel(tag); |
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222 | goto fail; |
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223 | } |
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224 | BURN(mk); |
225 | BURN(mc); |
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226 | } |
227 | |
228 | /* --- Decode the key data into the destination buffer --- */ |
229 | |
230 | if (k == kt) { |
231 | key_destroy(k); |
232 | passphrase_cancel(tag); |
233 | } |
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234 | if (key_decode(p, sz, kt)) |
235 | goto fail; |
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236 | |
237 | /* --- Done --- */ |
238 | |
239 | free(p); |
240 | return (0); |
241 | |
242 | /* --- Tidy up if things went wrong --- */ |
243 | |
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244 | fail: |
245 | BURN(b); |
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246 | free(p); |
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247 | return (-1); |
248 | } |
249 | |
250 | /*----- That's all, folks -------------------------------------------------*/ |