| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id$ |
| 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 | /*----- 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" |
| 41 | #include "rmd160-mgf.h" |
| 42 | #include "rmd160-hmac.h" |
| 43 | |
| 44 | /*----- Main code ---------------------------------------------------------*/ |
| 45 | |
| 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 | |
| 57 | /* --- @key_lock@ --- * |
| 58 | * |
| 59 | * Arguments: @key_data **kt@ = where to store the destination pointer |
| 60 | * @key_data *k@ = source key data block or null to use @*kt@ |
| 61 | * @const void *e@ = secret to encrypt key with |
| 62 | * @size_t esz@ = size of the secret |
| 63 | * |
| 64 | * Returns: --- |
| 65 | * |
| 66 | * Use: Encrypts a key data block using a secret. |
| 67 | */ |
| 68 | |
| 69 | void key_lock(key_data **kt, key_data *k, const void *e, size_t esz) |
| 70 | { |
| 71 | dstr d = DSTR_INIT; |
| 72 | octet b[RMD160_HASHSZ * 2]; |
| 73 | octet *m; |
| 74 | size_t msz; |
| 75 | rmd160_mgfctx r; |
| 76 | blowfish_cbcctx c; |
| 77 | rmd160_mackey mk; |
| 78 | rmd160_macctx mc; |
| 79 | |
| 80 | /* --- Sanity check --- */ |
| 81 | |
| 82 | if (k) key_incref(k); else k = *kt; |
| 83 | assert(((void)"Key data is already encrypted", |
| 84 | (k->e & KF_ENCMASK) != KENC_ENCRYPT)); |
| 85 | |
| 86 | /* --- Format the stuff in the buffer --- */ |
| 87 | |
| 88 | DENSURE(&d, RMD160_HASHSZ * 2); |
| 89 | rand_get(RAND_GLOBAL, d.buf, RMD160_HASHSZ); |
| 90 | d.len += RMD160_HASHSZ * 2; |
| 91 | key_encode(k, &d, 0); |
| 92 | m = (octet *)d.buf + RMD160_HASHSZ * 2; |
| 93 | msz = d.len - RMD160_HASHSZ * 2; |
| 94 | |
| 95 | /* --- Hash the passphrase to make a key --- */ |
| 96 | |
| 97 | rmd160_mgfkeybegin(&r); |
| 98 | rmd160_mgfkeyadd(&r, d.buf, RMD160_HASHSZ); |
| 99 | rmd160_mgfkeyadd(&r, e, esz); |
| 100 | rmd160_mgfencrypt(&r, 0, b, sizeof(b)); |
| 101 | BURN(r); |
| 102 | |
| 103 | /* --- Encrypt the plaintext --- */ |
| 104 | |
| 105 | blowfish_cbcinit(&c, b, RMD160_HASHSZ, 0); |
| 106 | blowfish_cbcencrypt(&c, m, m, msz); |
| 107 | BURN(c); |
| 108 | |
| 109 | /* --- MAC the ciphertext --- */ |
| 110 | |
| 111 | rmd160_hmacinit(&mk, b + RMD160_HASHSZ, RMD160_HASHSZ); |
| 112 | rmd160_macinit(&mc, &mk); |
| 113 | rmd160_machash(&mc, m, msz); |
| 114 | rmd160_macdone(&mc, d.buf + RMD160_HASHSZ); |
| 115 | BURN(mk); |
| 116 | BURN(mc); |
| 117 | |
| 118 | /* --- Done --- */ |
| 119 | |
| 120 | BURN(b); |
| 121 | *kt = key_newencrypted(0, d.buf, d.len); |
| 122 | key_drop(k); |
| 123 | dstr_destroy(&d); |
| 124 | } |
| 125 | |
| 126 | /* --- @key_unlock@ --- * |
| 127 | * |
| 128 | * Arguments: @key_data **kt@ = where to store the destination pointer |
| 129 | * @key_data *k@ = source key data block or null to use @*kt@ |
| 130 | * @const void *e@ = secret to decrypt the block with |
| 131 | * @size_t esz@ = size of the secret |
| 132 | * |
| 133 | * Returns: Zero for success, or a @KERR_@ error code. |
| 134 | * |
| 135 | * Use: Unlocks a key using a secret. |
| 136 | */ |
| 137 | |
| 138 | int key_unlock(key_data **kt, key_data *k, const void *e, size_t esz) |
| 139 | { |
| 140 | octet b[RMD160_HASHSZ * 2]; |
| 141 | octet *p = 0; |
| 142 | int rc; |
| 143 | int drop = 0; |
| 144 | key_data *kd; |
| 145 | rmd160_mgfctx r; |
| 146 | blowfish_cbcctx c; |
| 147 | rmd160_mackey mk; |
| 148 | rmd160_macctx mc; |
| 149 | size_t sz; |
| 150 | |
| 151 | /* --- Sanity check --- */ |
| 152 | |
| 153 | if (!k) { k = *kt; drop = 1; } |
| 154 | assert(((void)"Key data isn't encrypted", |
| 155 | (k->e & KF_ENCMASK) == KENC_ENCRYPT)); |
| 156 | |
| 157 | /* --- Check the size --- */ |
| 158 | |
| 159 | if (k->u.k.sz < RMD160_HASHSZ * 2) |
| 160 | return (KERR_MALFORMED); |
| 161 | sz = k->u.k.sz - RMD160_HASHSZ * 2; |
| 162 | |
| 163 | /* --- Hash the passphrase to make a key --- */ |
| 164 | |
| 165 | rmd160_mgfkeybegin(&r); |
| 166 | rmd160_mgfkeyadd(&r, k->u.k.k, RMD160_HASHSZ); |
| 167 | rmd160_mgfkeyadd(&r, e, esz); |
| 168 | rmd160_mgfencrypt(&r, 0, b, sizeof(b)); |
| 169 | BURN(r); |
| 170 | |
| 171 | /* --- Verify the MAC --- */ |
| 172 | |
| 173 | rmd160_hmacinit(&mk, b + RMD160_HASHSZ, RMD160_HASHSZ); |
| 174 | rmd160_macinit(&mc, &mk); |
| 175 | rmd160_machash(&mc, k->u.k.k + RMD160_HASHSZ * 2, sz); |
| 176 | rmd160_macdone(&mc, b + RMD160_HASHSZ); |
| 177 | if (memcmp(b + RMD160_HASHSZ, k->u.k.k + RMD160_HASHSZ, |
| 178 | RMD160_HASHSZ) != 0) { |
| 179 | rc = KERR_BADPASS; |
| 180 | goto fail; |
| 181 | } |
| 182 | BURN(mk); |
| 183 | BURN(mc); |
| 184 | |
| 185 | /* --- Allocate a destination buffer --- */ |
| 186 | |
| 187 | p = xmalloc(sz); |
| 188 | |
| 189 | /* --- Decrypt the key data --- */ |
| 190 | |
| 191 | blowfish_cbcinit(&c, b, RMD160_HASHSZ, 0); |
| 192 | blowfish_cbcdecrypt(&c, k->u.k.k + RMD160_HASHSZ * 2, p, sz); |
| 193 | BURN(c); |
| 194 | |
| 195 | /* --- Decode the key data into the destination buffer --- */ |
| 196 | |
| 197 | if ((kd = key_decode(p, sz)) == 0) { |
| 198 | rc = KERR_MALFORMED; |
| 199 | goto fail; |
| 200 | } |
| 201 | *kt = kd; |
| 202 | |
| 203 | /* --- Done --- */ |
| 204 | |
| 205 | xfree(p); |
| 206 | if (drop) key_drop(k); |
| 207 | return (0); |
| 208 | |
| 209 | /* --- Tidy up if things went wrong --- */ |
| 210 | |
| 211 | fail: |
| 212 | BURN(b); |
| 213 | xfree(p); |
| 214 | return (rc); |
| 215 | } |
| 216 | |
| 217 | /* --- @key_plock@ --- * |
| 218 | * |
| 219 | * Arguments: @key_data **kt@ = where to store the destination pointer |
| 220 | * @key_data *k@ = source key data block or null to use @*kt@ |
| 221 | * @const char *tag@ = tag to use for passphrase |
| 222 | * |
| 223 | * Returns: Zero if successful, a @KERR@ error code on failure. |
| 224 | * |
| 225 | * Use: Locks a key by encrypting it with a passphrase. |
| 226 | */ |
| 227 | |
| 228 | int key_plock(key_data **kt, key_data *k, const char *tag) |
| 229 | { |
| 230 | char buf[256]; |
| 231 | |
| 232 | if (passphrase_read(tag, PMODE_VERIFY, buf, sizeof(buf))) |
| 233 | return (KERR_IO); |
| 234 | key_lock(kt, k, buf, strlen(buf)); |
| 235 | BURN(buf); |
| 236 | return (0); |
| 237 | } |
| 238 | |
| 239 | /* --- @key_punlock@ --- * |
| 240 | * |
| 241 | * Arguments: @key_data **kt@ = where to store the destination pointer |
| 242 | * @key_data *k@ = source key data block or null to use @*kt@ |
| 243 | * @const char *tag@ = tag to use for passphrase |
| 244 | * |
| 245 | * Returns: Zero if it worked, a @KERR_@ error code on failure. |
| 246 | * |
| 247 | * Use: Unlocks a passphrase-locked key. |
| 248 | */ |
| 249 | |
| 250 | int key_punlock(key_data **kt, key_data *k, const char *tag) |
| 251 | { |
| 252 | char buf[256]; |
| 253 | int rc; |
| 254 | |
| 255 | if (passphrase_read(tag, PMODE_READ, buf, sizeof(buf))) |
| 256 | return (KERR_IO); |
| 257 | rc = key_unlock(kt, k, buf, strlen(buf)); |
| 258 | BURN(buf); |
| 259 | if (rc == KERR_BADPASS || !k) |
| 260 | passphrase_cancel(tag); |
| 261 | return (rc); |
| 262 | } |
| 263 | |
| 264 | /*----- That's all, folks -------------------------------------------------*/ |