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1 | /* -*-c-*- |
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2 | * |
3 | * Encrypting keys with passphrases |
4 | * |
5 | * (c) 1999 Straylight/Edgeware |
6 | */ |
7 | |
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8 | /*----- Licensing notice --------------------------------------------------* |
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9 | * |
10 | * This file is part of Catacomb. |
11 | * |
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. |
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16 | * |
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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. |
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21 | * |
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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, |
25 | * MA 02111-1307, USA. |
26 | */ |
27 | |
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28 | /*----- Header files ------------------------------------------------------*/ |
29 | |
30 | #include <mLib/dstr.h> |
31 | |
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32 | #include "key-data.h" |
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33 | #include "paranoia.h" |
34 | #include "passphrase.h" |
35 | #include "rand.h" |
36 | |
37 | #include "blowfish-cbc.h" |
38 | #include "rmd160.h" |
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39 | #include "rmd160-mgf.h" |
40 | #include "rmd160-hmac.h" |
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41 | |
42 | /*----- Main code ---------------------------------------------------------*/ |
43 | |
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44 | /* --- Format --- * |
45 | * |
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 | * %$y = N \cat \tau \cat y_0$%. |
50 | * |
51 | * This is not the original format. The original format was insecure, and |
52 | * has been replaced incompatibly. |
53 | */ |
54 | |
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55 | /* --- @key_lock@ --- * |
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56 | * |
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57 | * Arguments: @key_data **kt@ = where to store the destination pointer |
58 | * @key_data *k@ = source key data block or null to use @*kt@ |
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59 | * @const void *e@ = secret to encrypt key with |
60 | * @size_t esz@ = size of the secret |
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61 | * |
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62 | * Returns: --- |
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63 | * |
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64 | * Use: Encrypts a key data block using a secret. |
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65 | */ |
66 | |
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67 | void key_lock(key_data **kt, key_data *k, const void *e, size_t esz) |
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68 | { |
69 | dstr d = DSTR_INIT; |
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70 | octet b[RMD160_HASHSZ * 2]; |
71 | octet *m; |
72 | size_t msz; |
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73 | rmd160_mgfctx r; |
74 | blowfish_cbcctx c; |
75 | rmd160_mackey mk; |
76 | rmd160_macctx mc; |
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77 | |
78 | /* --- Sanity check --- */ |
79 | |
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80 | if (k) key_incref(k); else k = *kt; |
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81 | assert(((void)"Key data is already encrypted", |
82 | (k->e & KF_ENCMASK) != KENC_ENCRYPT)); |
83 | |
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84 | /* --- Format the stuff in the buffer --- */ |
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85 | |
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86 | DENSURE(&d, RMD160_HASHSZ * 2); |
87 | rand_get(RAND_GLOBAL, d.buf, RMD160_HASHSZ); |
88 | d.len += RMD160_HASHSZ * 2; |
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89 | key_encode(k, &d, 0); |
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90 | m = (octet *)d.buf + RMD160_HASHSZ * 2; |
91 | msz = d.len - RMD160_HASHSZ * 2; |
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92 | |
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93 | /* --- Hash the passphrase to make a key --- */ |
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94 | |
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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)); |
99 | BURN(r); |
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100 | |
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101 | /* --- Encrypt the plaintext --- */ |
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102 | |
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103 | blowfish_cbcinit(&c, b, RMD160_HASHSZ, 0); |
104 | blowfish_cbcencrypt(&c, m, m, msz); |
105 | BURN(c); |
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106 | |
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107 | /* --- MAC the ciphertext --- */ |
108 | |
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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); |
113 | BURN(mk); |
114 | BURN(mc); |
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115 | |
116 | /* --- Done --- */ |
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117 | |
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118 | BURN(b); |
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119 | *kt = key_newencrypted(0, d.buf, d.len); |
120 | key_drop(k); |
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121 | dstr_destroy(&d); |
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122 | } |
123 | |
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124 | /* --- @key_unlock@ --- * |
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125 | * |
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126 | * Arguments: @key_data **kt@ = where to store the destination pointer |
127 | * @key_data *k@ = source key data block or null to use @*kt@ |
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128 | * @const void *e@ = secret to decrypt the block with |
129 | * @size_t esz@ = size of the secret |
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130 | * |
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131 | * Returns: Zero for success, or a @KERR_@ error code. |
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132 | * |
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133 | * Use: Unlocks a key using a secret. |
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134 | */ |
135 | |
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136 | int key_unlock(key_data **kt, key_data *k, const void *e, size_t esz) |
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137 | { |
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138 | octet b[RMD160_HASHSZ * 2]; |
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139 | octet *p = 0; |
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140 | int rc; |
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141 | int drop = 0; |
142 | key_data *kd; |
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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 | |
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151 | if (!k) { k = *kt; drop = 1; } |
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152 | assert(((void)"Key data isn't encrypted", |
153 | (k->e & KF_ENCMASK) == KENC_ENCRYPT)); |
154 | |
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155 | /* --- Check the size --- */ |
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156 | |
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157 | if (k->u.k.sz < RMD160_HASHSZ * 2) |
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158 | return (KERR_MALFORMED); |
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159 | sz = k->u.k.sz - RMD160_HASHSZ * 2; |
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160 | |
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161 | /* --- Hash the passphrase to make a key --- */ |
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162 | |
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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)); |
167 | BURN(r); |
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168 | |
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169 | /* --- Verify the MAC --- */ |
170 | |
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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) { |
177 | rc = KERR_BADPASS; |
178 | goto fail; |
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179 | } |
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180 | BURN(mk); |
181 | BURN(mc); |
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182 | |
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183 | /* --- Allocate a destination buffer --- */ |
184 | |
185 | p = xmalloc(sz); |
186 | |
187 | /* --- Decrypt the key data --- */ |
188 | |
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189 | blowfish_cbcinit(&c, b, RMD160_HASHSZ, 0); |
190 | blowfish_cbcdecrypt(&c, k->u.k.k + RMD160_HASHSZ * 2, p, sz); |
191 | BURN(c); |
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192 | |
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193 | /* --- Decode the key data into the destination buffer --- */ |
194 | |
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195 | if ((kd = key_decode(p, sz)) == 0) { |
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196 | rc = KERR_MALFORMED; |
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197 | goto fail; |
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198 | } |
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199 | *kt = kd; |
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200 | |
201 | /* --- Done --- */ |
202 | |
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203 | xfree(p); |
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204 | if (drop) key_drop(k); |
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205 | return (0); |
206 | |
207 | /* --- Tidy up if things went wrong --- */ |
208 | |
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209 | fail: |
210 | BURN(b); |
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211 | xfree(p); |
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212 | return (rc); |
213 | } |
214 | |
215 | /* --- @key_plock@ --- * |
216 | * |
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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 |
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220 | * |
221 | * Returns: Zero if successful, a @KERR@ error code on failure. |
222 | * |
223 | * Use: Locks a key by encrypting it with a passphrase. |
224 | */ |
225 | |
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226 | int key_plock(key_data **kt, key_data *k, const char *tag) |
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227 | { |
228 | char buf[256]; |
229 | |
230 | if (passphrase_read(tag, PMODE_VERIFY, buf, sizeof(buf))) |
231 | return (KERR_IO); |
232 | key_lock(kt, k, buf, strlen(buf)); |
233 | BURN(buf); |
234 | return (0); |
235 | } |
236 | |
237 | /* --- @key_punlock@ --- * |
238 | * |
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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 |
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242 | * |
243 | * Returns: Zero if it worked, a @KERR_@ error code on failure. |
244 | * |
245 | * Use: Unlocks a passphrase-locked key. |
246 | */ |
247 | |
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248 | int key_punlock(key_data **kt, key_data *k, const char *tag) |
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249 | { |
250 | char buf[256]; |
251 | int rc; |
252 | |
253 | if (passphrase_read(tag, PMODE_READ, buf, sizeof(buf))) |
254 | return (KERR_IO); |
255 | rc = key_unlock(kt, k, buf, strlen(buf)); |
256 | BURN(buf); |
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257 | if (rc == KERR_BADPASS || !k) |
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258 | passphrase_cancel(tag); |
259 | return (rc); |
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260 | } |
261 | |
262 | /*----- That's all, folks -------------------------------------------------*/ |