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1 | /* -*-c-*- |
2 | * |
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3 | * $Id$ |
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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 | |
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30 | /*----- Header files ------------------------------------------------------*/ |
31 | |
32 | #include <mLib/dstr.h> |
33 | |
34 | #include "key.h" |
35 | #include "paranoia.h" |
36 | #include "passphrase.h" |
37 | #include "rand.h" |
38 | |
39 | #include "blowfish-cbc.h" |
40 | #include "rmd160.h" |
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41 | #include "rmd160-mgf.h" |
42 | #include "rmd160-hmac.h" |
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43 | |
44 | /*----- Main code ---------------------------------------------------------*/ |
45 | |
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46 | /* --- Format --- * |
47 | * |
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 | * %$y = N \cat \tau \cat y_0$%. |
52 | * |
53 | * This is not the original format. The original format was insecure, and |
54 | * has been replaced incompatibly. |
55 | */ |
56 | |
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57 | /* --- @key_lock@ --- * |
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58 | * |
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59 | * Arguments: @key_data *kt@ = destination block |
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60 | * @key_data *k@ = source key data block |
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61 | * @const void *e@ = secret to encrypt key with |
62 | * @size_t esz@ = size of the secret |
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63 | * |
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64 | * Returns: --- |
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65 | * |
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66 | * Use: Encrypts a key data block using a secret. |
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67 | */ |
68 | |
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69 | void key_lock(key_data *kt, key_data *k, const void *e, size_t esz) |
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70 | { |
71 | dstr d = DSTR_INIT; |
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72 | octet b[RMD160_HASHSZ * 2]; |
73 | octet *m; |
74 | size_t msz; |
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75 | rmd160_mgfctx r; |
76 | blowfish_cbcctx c; |
77 | rmd160_mackey mk; |
78 | rmd160_macctx mc; |
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79 | |
80 | /* --- Sanity check --- */ |
81 | |
82 | assert(((void)"Key data is already encrypted", |
83 | (k->e & KF_ENCMASK) != KENC_ENCRYPT)); |
84 | |
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85 | /* --- Format the stuff in the buffer --- */ |
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86 | |
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87 | DENSURE(&d, RMD160_HASHSZ * 2); |
88 | rand_get(RAND_GLOBAL, d.buf, RMD160_HASHSZ); |
89 | d.len += RMD160_HASHSZ * 2; |
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90 | key_encode(k, &d, 0); |
91 | if (k == kt) |
92 | key_destroy(k); |
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93 | m = (octet *)d.buf + RMD160_HASHSZ * 2; |
94 | msz = d.len - RMD160_HASHSZ * 2; |
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95 | |
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96 | /* --- Hash the passphrase to make a key --- */ |
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97 | |
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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)); |
102 | BURN(r); |
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103 | |
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104 | /* --- Encrypt the plaintext --- */ |
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105 | |
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106 | blowfish_cbcinit(&c, b, RMD160_HASHSZ, 0); |
107 | blowfish_cbcencrypt(&c, m, m, msz); |
108 | BURN(c); |
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109 | |
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110 | /* --- MAC the ciphertext --- */ |
111 | |
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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); |
116 | BURN(mk); |
117 | BURN(mc); |
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118 | |
119 | /* --- Done --- */ |
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120 | |
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121 | BURN(b); |
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122 | key_encrypted(kt, d.buf, d.len); |
123 | dstr_destroy(&d); |
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124 | } |
125 | |
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126 | /* --- @key_unlock@ --- * |
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127 | * |
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128 | * Arguments: @key_data *kt@ = target block |
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129 | * @key_data *k@ = source key data block |
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130 | * @const void *e@ = secret to decrypt the block with |
131 | * @size_t esz@ = size of the secret |
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132 | * |
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133 | * Returns: Zero for success, or a @KERR_@ error code. |
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134 | * |
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135 | * Use: Unlocks a key using a secret. |
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136 | */ |
137 | |
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138 | int key_unlock(key_data *kt, key_data *k, const void *e, size_t esz) |
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139 | { |
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140 | octet b[RMD160_HASHSZ * 2]; |
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141 | octet *p = 0; |
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142 | int rc; |
143 | rmd160_mgfctx r; |
144 | blowfish_cbcctx c; |
145 | rmd160_mackey mk; |
146 | rmd160_macctx mc; |
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147 | size_t sz; |
148 | |
149 | /* --- Sanity check --- */ |
150 | |
151 | assert(((void)"Key data isn't encrypted", |
152 | (k->e & KF_ENCMASK) == KENC_ENCRYPT)); |
153 | |
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154 | /* --- Check the size --- */ |
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155 | |
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156 | if (k->u.k.sz < RMD160_HASHSZ * 2) |
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157 | return (KERR_MALFORMED); |
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158 | sz = k->u.k.sz - RMD160_HASHSZ * 2; |
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159 | |
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160 | /* --- Hash the passphrase to make a key --- */ |
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161 | |
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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)); |
166 | BURN(r); |
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167 | |
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168 | /* --- Verify the MAC --- */ |
169 | |
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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) { |
176 | rc = KERR_BADPASS; |
177 | goto fail; |
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178 | } |
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179 | BURN(mk); |
180 | BURN(mc); |
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181 | |
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182 | /* --- Allocate a destination buffer --- */ |
183 | |
184 | p = xmalloc(sz); |
185 | |
186 | /* --- Decrypt the key data --- */ |
187 | |
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188 | blowfish_cbcinit(&c, b, RMD160_HASHSZ, 0); |
189 | blowfish_cbcdecrypt(&c, k->u.k.k + RMD160_HASHSZ * 2, p, sz); |
190 | BURN(c); |
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191 | |
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192 | /* --- Decode the key data into the destination buffer --- */ |
193 | |
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194 | if (k == kt) |
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195 | key_destroy(k); |
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196 | if (key_decode(p, sz, kt)) { |
197 | rc = KERR_MALFORMED; |
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198 | goto fail; |
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199 | } |
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200 | |
201 | /* --- Done --- */ |
202 | |
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203 | xfree(p); |
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204 | return (0); |
205 | |
206 | /* --- Tidy up if things went wrong --- */ |
207 | |
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208 | fail: |
209 | BURN(b); |
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210 | xfree(p); |
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211 | return (rc); |
212 | } |
213 | |
214 | /* --- @key_plock@ --- * |
215 | * |
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 |
219 | * |
220 | * Returns: Zero if successful, a @KERR@ error code on failure. |
221 | * |
222 | * Use: Locks a key by encrypting it with a passphrase. |
223 | */ |
224 | |
225 | int key_plock(const char *tag, key_data *k, key_data *kt) |
226 | { |
227 | char buf[256]; |
228 | |
229 | if (passphrase_read(tag, PMODE_VERIFY, buf, sizeof(buf))) |
230 | return (KERR_IO); |
231 | key_lock(kt, k, buf, strlen(buf)); |
232 | BURN(buf); |
233 | return (0); |
234 | } |
235 | |
236 | /* --- @key_punlock@ --- * |
237 | * |
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 |
241 | * |
242 | * Returns: Zero if it worked, a @KERR_@ error code on failure. |
243 | * |
244 | * Use: Unlocks a passphrase-locked key. |
245 | */ |
246 | |
247 | int key_punlock(const char *tag, key_data *k, key_data *kt) |
248 | { |
249 | char buf[256]; |
250 | int rc; |
251 | |
252 | if (passphrase_read(tag, PMODE_READ, buf, sizeof(buf))) |
253 | return (KERR_IO); |
254 | rc = key_unlock(kt, k, buf, strlen(buf)); |
255 | BURN(buf); |
256 | if (rc == KERR_BADPASS || k == kt) |
257 | passphrase_cancel(tag); |
258 | return (rc); |
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259 | } |
260 | |
261 | /*----- That's all, folks -------------------------------------------------*/ |