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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: key-pass.c,v 1.5 2004/04/08 01:36:15 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 | |
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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_plock@ --- * |
58 | * |
59 | * Arguments: @const char *tag@ = tag to use for passphrase |
60 | * @key_data *k@ = source key data block |
61 | * @key_data *kt@ = target key data block |
62 | * |
63 | * Returns: Zero if successful, nonzero if there was a problem. |
64 | * |
65 | * Use: Locks a key by encrypting it with a passphrase. |
66 | */ |
67 | |
68 | int key_plock(const char *tag, key_data *k, key_data *kt) |
69 | { |
70 | dstr d = DSTR_INIT; |
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71 | octet b[RMD160_HASHSZ * 2]; |
72 | octet *m; |
73 | size_t msz; |
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74 | char buf[256]; |
75 | |
76 | /* --- Sanity check --- */ |
77 | |
78 | assert(((void)"Key data is already encrypted", |
79 | (k->e & KF_ENCMASK) != KENC_ENCRYPT)); |
80 | |
59b2b448 |
81 | /* --- Format the stuff in the buffer --- */ |
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82 | |
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83 | DENSURE(&d, RMD160_HASHSZ * 2); |
84 | rand_get(RAND_GLOBAL, d.buf, RMD160_HASHSZ); |
85 | d.len += RMD160_HASHSZ * 2; |
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86 | key_encode(k, &d, 0); |
87 | if (k == kt) |
88 | key_destroy(k); |
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89 | m = (octet *)d.buf + RMD160_HASHSZ * 2; |
90 | msz = d.len - RMD160_HASHSZ * 2; |
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91 | |
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92 | /* --- Read the passphrase --- */ |
93 | |
94 | if (passphrase_read(tag, PMODE_VERIFY, buf, sizeof(buf))) { |
95 | dstr_destroy(&d); |
96 | return (-1); |
97 | } |
98 | |
99 | /* --- Hash the passphrase to make a key --- */ |
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100 | |
101 | { |
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102 | rmd160_mgfctx r; |
103 | rmd160_mgfkeybegin(&r); |
104 | rmd160_mgfkeyadd(&r, d.buf, RMD160_HASHSZ); |
105 | rmd160_mgfkeyadd(&r, buf, strlen(buf)); |
106 | rmd160_mgfencrypt(&r, 0, b, sizeof(b)); |
107 | BURN(r); |
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108 | BURN(buf); |
109 | } |
110 | |
59b2b448 |
111 | /* --- Encrypt the plaintext --- */ |
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112 | |
113 | { |
114 | blowfish_cbcctx c; |
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115 | blowfish_cbcinit(&c, b, RMD160_HASHSZ, 0); |
116 | blowfish_cbcencrypt(&c, m, m, msz); |
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117 | BURN(c); |
118 | } |
119 | |
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120 | /* --- MAC the ciphertext --- */ |
121 | |
122 | { |
123 | rmd160_mackey mk; |
124 | rmd160_macctx mc; |
125 | rmd160_hmacinit(&mk, b + RMD160_HASHSZ, RMD160_HASHSZ); |
126 | rmd160_macinit(&mc, &mk); |
127 | rmd160_machash(&mc, m, msz); |
128 | rmd160_macdone(&mc, d.buf + RMD160_HASHSZ); |
129 | BURN(mk); |
130 | BURN(mc); |
131 | } |
132 | |
133 | /* --- Done --- */ |
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134 | |
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135 | BURN(b); |
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136 | key_encrypted(kt, d.buf, d.len); |
137 | dstr_destroy(&d); |
138 | return (0); |
139 | } |
140 | |
141 | /* --- @key_punlock@ --- * |
142 | * |
143 | * Arguments: @const char *tag@ = tag to use for passphrase |
144 | * @key_data *k@ = source key data block |
145 | * @key_data *kt@ = target key data block |
146 | * |
147 | * Returns: Zero if it worked, nonzero if it didn't. |
148 | * |
149 | * Use: Unlocks a passphrase-locked key. |
150 | */ |
151 | |
152 | int key_punlock(const char *tag, key_data *k, key_data *kt) |
153 | { |
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154 | octet b[RMD160_HASHSZ * 2]; |
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155 | char buf[256]; |
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156 | octet *p = 0; |
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157 | size_t sz; |
158 | |
159 | /* --- Sanity check --- */ |
160 | |
161 | assert(((void)"Key data isn't encrypted", |
162 | (k->e & KF_ENCMASK) == KENC_ENCRYPT)); |
163 | |
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164 | /* --- Check the size --- */ |
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165 | |
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166 | if (k->u.k.sz < RMD160_HASHSZ * 2) |
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167 | return (-1); |
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168 | sz = k->u.k.sz - RMD160_HASHSZ * 2; |
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169 | |
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170 | /* --- Fetch the passphrase --- */ |
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171 | |
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172 | if (passphrase_read(tag, PMODE_READ, buf, sizeof(buf))) |
173 | goto fail; |
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174 | |
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175 | /* --- Hash the passphrase to make a key --- */ |
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176 | |
177 | { |
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178 | rmd160_mgfctx r; |
179 | rmd160_mgfkeybegin(&r); |
180 | rmd160_mgfkeyadd(&r, k->u.k.k, RMD160_HASHSZ); |
181 | rmd160_mgfkeyadd(&r, buf, strlen(buf)); |
182 | rmd160_mgfencrypt(&r, 0, b, sizeof(b)); |
183 | BURN(r); |
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184 | BURN(buf); |
185 | } |
186 | |
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187 | /* --- Verify the MAC --- */ |
188 | |
189 | { |
190 | rmd160_mackey mk; |
191 | rmd160_macctx mc; |
192 | rmd160_hmacinit(&mk, b + RMD160_HASHSZ, RMD160_HASHSZ); |
193 | rmd160_macinit(&mc, &mk); |
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194 | rmd160_machash(&mc, k->u.k.k + RMD160_HASHSZ * 2, sz); |
195 | rmd160_macdone(&mc, b + RMD160_HASHSZ); |
196 | if (memcmp(b + RMD160_HASHSZ, k->u.k.k + RMD160_HASHSZ, |
197 | RMD160_HASHSZ) != 0) { |
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198 | passphrase_cancel(tag); |
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199 | goto fail; |
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200 | } |
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201 | BURN(mk); |
202 | BURN(mc); |
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203 | } |
204 | |
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205 | /* --- Allocate a destination buffer --- */ |
206 | |
207 | p = xmalloc(sz); |
208 | |
209 | /* --- Decrypt the key data --- */ |
210 | |
211 | { |
212 | blowfish_cbcctx c; |
213 | blowfish_cbcinit(&c, b, RMD160_HASHSZ, 0); |
214 | blowfish_cbcdecrypt(&c, k->u.k.k + RMD160_HASHSZ * 2, p, sz); |
215 | BURN(c); |
216 | } |
217 | |
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218 | /* --- Decode the key data into the destination buffer --- */ |
219 | |
220 | if (k == kt) { |
221 | key_destroy(k); |
222 | passphrase_cancel(tag); |
223 | } |
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224 | if (key_decode(p, sz, kt)) |
225 | goto fail; |
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226 | |
227 | /* --- Done --- */ |
228 | |
229 | free(p); |
230 | return (0); |
231 | |
232 | /* --- Tidy up if things went wrong --- */ |
233 | |
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234 | fail: |
235 | BURN(b); |
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236 | free(p); |
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237 | return (-1); |
238 | } |
239 | |
240 | /*----- That's all, folks -------------------------------------------------*/ |