--- /dev/null
+/* -*-c-*-
+ *
+ * Encrypting keys with passphrases
+ *
+ * (c) 1999 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------*
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * Catacomb is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with Catacomb; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <mLib/dstr.h>
+
+#include "key-data.h"
+#include "paranoia.h"
+#include "passphrase.h"
+#include "rand.h"
+
+#include "blowfish-cbc.h"
+#include "rmd160.h"
+#include "rmd160-mgf.h"
+#include "rmd160-hmac.h"
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- Format --- *
+ *
+ * Choose a random 160-bit string %$R$%. Take the passphrase %$P$%, and
+ * the message %$m$%. Now, compute %$K_E \cat K_T = H(R \cat P)$%,
+ * %$y_0 = E_{K_E}(m)$% and %$\tau = T_{K_T}(y_0)$%. The ciphertext is
+ * %$y = N \cat \tau \cat y_0$%.
+ *
+ * This is not the original format. The original format was insecure, and
+ * has been replaced incompatibly.
+ */
+
+/* --- @key_lock@ --- *
+ *
+ * Arguments: @key_data **kt@ = where to store the destination pointer
+ * @key_data *k@ = source key data block or null to use @*kt@
+ * @const void *e@ = secret to encrypt key with
+ * @size_t esz@ = size of the secret
+ *
+ * Returns: ---
+ *
+ * Use: Encrypts a key data block using a secret.
+ */
+
+void key_lock(key_data **kt, key_data *k, const void *e, size_t esz)
+{
+ dstr d = DSTR_INIT;
+ octet b[RMD160_HASHSZ * 2];
+ octet *m;
+ size_t msz;
+ rmd160_mgfctx r;
+ blowfish_cbcctx c;
+ rmd160_mackey mk;
+ rmd160_macctx mc;
+
+ /* --- Sanity check --- */
+
+ if (k) key_incref(k); else k = *kt;
+ assert(((void)"Key data is already encrypted",
+ (k->e & KF_ENCMASK) != KENC_ENCRYPT));
+
+ /* --- Format the stuff in the buffer --- */
+
+ DENSURE(&d, RMD160_HASHSZ * 2);
+ rand_get(RAND_GLOBAL, d.buf, RMD160_HASHSZ);
+ d.len += RMD160_HASHSZ * 2;
+ key_encode(k, &d, 0);
+ m = (octet *)d.buf + RMD160_HASHSZ * 2;
+ msz = d.len - RMD160_HASHSZ * 2;
+
+ /* --- Hash the passphrase to make a key --- */
+
+ rmd160_mgfkeybegin(&r);
+ rmd160_mgfkeyadd(&r, d.buf, RMD160_HASHSZ);
+ rmd160_mgfkeyadd(&r, e, esz);
+ rmd160_mgfencrypt(&r, 0, b, sizeof(b));
+ BURN(r);
+
+ /* --- Encrypt the plaintext --- */
+
+ blowfish_cbcinit(&c, b, RMD160_HASHSZ, 0);
+ blowfish_cbcencrypt(&c, m, m, msz);
+ BURN(c);
+
+ /* --- MAC the ciphertext --- */
+
+ rmd160_hmacinit(&mk, b + RMD160_HASHSZ, RMD160_HASHSZ);
+ rmd160_macinit(&mc, &mk);
+ rmd160_machash(&mc, m, msz);
+ rmd160_macdone(&mc, d.buf + RMD160_HASHSZ);
+ BURN(mk);
+ BURN(mc);
+
+ /* --- Done --- */
+
+ BURN(b);
+ *kt = key_newencrypted(0, d.buf, d.len);
+ key_drop(k);
+ dstr_destroy(&d);
+}
+
+/* --- @key_unlock@ --- *
+ *
+ * Arguments: @key_data **kt@ = where to store the destination pointer
+ * @key_data *k@ = source key data block or null to use @*kt@
+ * @const void *e@ = secret to decrypt the block with
+ * @size_t esz@ = size of the secret
+ *
+ * Returns: Zero for success, or a @KERR_@ error code.
+ *
+ * Use: Unlocks a key using a secret.
+ */
+
+int key_unlock(key_data **kt, key_data *k, const void *e, size_t esz)
+{
+ octet b[RMD160_HASHSZ * 2];
+ octet *p = 0;
+ int rc;
+ int drop = 0;
+ key_data *kd;
+ rmd160_mgfctx r;
+ blowfish_cbcctx c;
+ rmd160_mackey mk;
+ rmd160_macctx mc;
+ size_t sz;
+
+ /* --- Sanity check --- */
+
+ if (!k) { k = *kt; drop = 1; }
+ assert(((void)"Key data isn't encrypted",
+ (k->e & KF_ENCMASK) == KENC_ENCRYPT));
+
+ /* --- Check the size --- */
+
+ if (k->u.k.sz < RMD160_HASHSZ * 2)
+ return (KERR_MALFORMED);
+ sz = k->u.k.sz - RMD160_HASHSZ * 2;
+
+ /* --- Hash the passphrase to make a key --- */
+
+ rmd160_mgfkeybegin(&r);
+ rmd160_mgfkeyadd(&r, k->u.k.k, RMD160_HASHSZ);
+ rmd160_mgfkeyadd(&r, e, esz);
+ rmd160_mgfencrypt(&r, 0, b, sizeof(b));
+ BURN(r);
+
+ /* --- Verify the MAC --- */
+
+ rmd160_hmacinit(&mk, b + RMD160_HASHSZ, RMD160_HASHSZ);
+ rmd160_macinit(&mc, &mk);
+ rmd160_machash(&mc, k->u.k.k + RMD160_HASHSZ * 2, sz);
+ rmd160_macdone(&mc, b + RMD160_HASHSZ);
+ if (memcmp(b + RMD160_HASHSZ, k->u.k.k + RMD160_HASHSZ,
+ RMD160_HASHSZ) != 0) {
+ rc = KERR_BADPASS;
+ goto fail;
+ }
+ BURN(mk);
+ BURN(mc);
+
+ /* --- Allocate a destination buffer --- */
+
+ p = xmalloc(sz);
+
+ /* --- Decrypt the key data --- */
+
+ blowfish_cbcinit(&c, b, RMD160_HASHSZ, 0);
+ blowfish_cbcdecrypt(&c, k->u.k.k + RMD160_HASHSZ * 2, p, sz);
+ BURN(c);
+
+ /* --- Decode the key data into the destination buffer --- */
+
+ if ((kd = key_decode(p, sz)) == 0) {
+ rc = KERR_MALFORMED;
+ goto fail;
+ }
+ *kt = kd;
+
+ /* --- Done --- */
+
+ xfree(p);
+ if (drop) key_drop(k);
+ return (0);
+
+ /* --- Tidy up if things went wrong --- */
+
+fail:
+ BURN(b);
+ xfree(p);
+ return (rc);
+}
+
+/* --- @key_plock@ --- *
+ *
+ * Arguments: @key_data **kt@ = where to store the destination pointer
+ * @key_data *k@ = source key data block or null to use @*kt@
+ * @const char *tag@ = tag to use for passphrase
+ *
+ * Returns: Zero if successful, a @KERR@ error code on failure.
+ *
+ * Use: Locks a key by encrypting it with a passphrase.
+ */
+
+int key_plock(key_data **kt, key_data *k, const char *tag)
+{
+ char buf[256];
+
+ if (passphrase_read(tag, PMODE_VERIFY, buf, sizeof(buf)))
+ return (KERR_IO);
+ key_lock(kt, k, buf, strlen(buf));
+ BURN(buf);
+ return (0);
+}
+
+/* --- @key_punlock@ --- *
+ *
+ * Arguments: @key_data **kt@ = where to store the destination pointer
+ * @key_data *k@ = source key data block or null to use @*kt@
+ * @const char *tag@ = tag to use for passphrase
+ *
+ * Returns: Zero if it worked, a @KERR_@ error code on failure.
+ *
+ * Use: Unlocks a passphrase-locked key.
+ */
+
+int key_punlock(key_data **kt, key_data *k, const char *tag)
+{
+ char buf[256];
+ int rc;
+
+ if (passphrase_read(tag, PMODE_READ, buf, sizeof(buf)))
+ return (KERR_IO);
+ rc = key_unlock(kt, k, buf, strlen(buf));
+ BURN(buf);
+ if (rc == KERR_BADPASS || !k)
+ passphrase_cancel(tag);
+ return (rc);
+}
+
+/*----- That's all, folks -------------------------------------------------*/
projects / u / mdw / catacomb / blobdiff