/* -*-c-*-
*
- * $Id$
- *
* Handling of symmetric keysets
*
* (c) 2001 Straylight/Edgeware
*/
-/*----- Licensing notice --------------------------------------------------*
+/*----- Licensing notice --------------------------------------------------*
*
* This file is part of Trivial IP Encryption (TrIPE).
*
- * TrIPE is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * TrIPE 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 General Public License for more details.
- *
+ * TrIPE is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * TrIPE 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 General Public License
+ * for more details.
+ *
* You should have received a copy of the GNU General Public License
- * along with TrIPE; if not, write to the Free Software Foundation,
- * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ * along with TrIPE. If not, see <https://www.gnu.org/licenses/>.
*/
/*----- Header files ------------------------------------------------------*/
#include "tripe.h"
-/*----- Tunable parameters ------------------------------------------------*/
-
-/* --- Note on size limits --- *
- *
- * For a 64-bit block cipher (e.g., Blowfish), the probability of a collision
- * occurring after 32 MB is less than %$2^{-21}$%, and the probability of a
- * collision occurring after 64 MB is less than %$2^{-19}$%. These could be
- * adjusted dependent on the encryption scheme, but it's too much pain.
- */
-
-#define T_EXP MIN(60) /* Expiry time for a key */
-#define T_REGEN MIN(45) /* Regeneration time for a key */
-#define SZ_EXP MEG(64) /* Expiry data size for a key */
-#define SZ_REGEN MEG(32) /* Data size threshold for regen */
-
/*----- Handy macros ------------------------------------------------------*/
#define KEYOK(ks, now) ((ks)->sz_exp > 0 && (ks)->t_exp > now)
-#define SEQSZ 4 /* Size of sequence number packet */
-
/*----- Low-level packet encryption and decryption ------------------------*/
/* --- Encrypted data format --- *
*
* Let %$p_i$% be the %$i$%-th plaintext message, with type %$t$%. We first
- * compute
+ * compute
*
* %$c_i = \mathcal{E}\textrm{-CBC}_{K_{\text{E}}}(p_i)$%
*
* @buf *b@ = pointer to an input buffer
* @buf *bb@ = pointer to an output buffer
*
- * Returns: Zero if OK, nonzero if a new key is required.
+ * Returns: Zero if OK; @KSERR_REGEN@ if it's time to generate new keys.
+ * Also returns zero if there was insufficient buffer space, but
+ * the buffer is broken in this case.
*
* Use: Encrypts a message with the given key. We assume that the
* keyset is OK to use.
static int doencrypt(keyset *ks, unsigned ty, buf *b, buf *bb)
{
- ghash *h;
- gcipher *c = ks->cout;
- const octet *p = BCUR(b);
+ int rc;
size_t sz = BLEFT(b);
- octet *qmac, *qseq, *qiv, *qpk;
- uint32 oseq;
- size_t ivsz = GC_CLASS(c)->blksz;
- size_t tagsz = ks->tagsz;
size_t osz, nsz;
- octet t[4];
- int rc = 0;
- /* --- Allocate the required buffer space --- */
+ /* --- Initial tracing --- */
- if (buf_ensure(bb, tagsz + SEQSZ + ivsz + sz))
- return (0); /* Caution! */
- qmac = BCUR(bb); qseq = qmac + tagsz; qiv = qseq + SEQSZ; qpk = qiv + ivsz;
- BSTEP(bb, tagsz + SEQSZ + ivsz + sz);
- STORE32(t, ty);
-
- oseq = ks->oseq++; STORE32(qseq, oseq);
IF_TRACING(T_KEYSET, {
- trace(T_KEYSET, "keyset: encrypting packet %lu using keyset %u",
- (unsigned long)oseq, ks->seq);
- trace_block(T_CRYPTO, "crypto: plaintext packet", p, sz);
+ trace(T_KEYSET,
+ "keyset: encrypting packet %lu (type 0x%02x) using keyset %u",
+ (unsigned long)ks->oseq, ty, ks->seq);
+ trace_block(T_CRYPTO, "crypto: plaintext packet", BCUR(b), sz);
})
- /* --- Encrypt the packet --- */
+ /* --- Apply the bulk-crypto transformation --- */
- if (ivsz) {
- rand_get(RAND_GLOBAL, qiv, ivsz);
- GC_SETIV(c, qiv);
- IF_TRACING(T_KEYSET, {
- trace_block(T_CRYPTO, "crypto: initialization vector", qiv, ivsz);
- })
- }
- GC_ENCRYPT(c, p, qpk, sz);
- IF_TRACING(T_KEYSET, {
- trace_block(T_CRYPTO, "crypto: encrypted packet", qpk, sz);
- })
-
- /* --- Now compute the MAC --- */
-
- if (tagsz) {
- h = GM_INIT(ks->mout);
- GH_HASH(h, t, sizeof(t));
- GH_HASH(h, qseq, SEQSZ + ivsz + sz);
- memcpy(qmac, GH_DONE(h, 0), tagsz);
- GH_DESTROY(h);
- IF_TRACING(T_KEYSET, {
- trace_block(T_CRYPTO, "crypto: computed MAC", qmac, tagsz);
- })
- }
+ rc = ks->bulk->ops->encrypt(ks->bulk, ty, b, bb, ks->oseq);
+ if (rc || !BOK(bb)) return (rc);
+ ks->oseq++;
- /* --- Deduct the packet size from the key's data life --- */
+ /* --- Do the necessary accounting for data volume --- */
osz = ks->sz_exp;
- if (osz > sz)
- nsz = osz - sz;
- else
- nsz = 0;
- if (osz >= SZ_REGEN && nsz < SZ_REGEN) {
+ nsz = osz > sz ? osz - sz : 0;
+ if (osz >= ks->sz_regen && ks->sz_regen > nsz) {
T( trace(T_KEYSET, "keyset: keyset %u data regen limit exceeded -- "
"forcing exchange", ks->seq); )
- rc = -1;
+ rc = KSERR_REGEN;
}
ks->sz_exp = nsz;
- return (rc);
+
+ /* --- We're done --- */
+
+ return (rc);
}
/* --- @dodecrypt@ --- *
* @buf *bb@ = pointer to an output buffer
* @uint32 *seq@ = where to store the sequence number
*
- * Returns: Zero if OK, nonzero if it failed.
+ * Returns: Zero on success; @KSERR_DECRYPT@ on failure.
*
* Use: Attempts to decrypt a message with the given key. No other
* checking (e.g., sequence number checks) is performed. We
static int dodecrypt(keyset *ks, unsigned ty, buf *b, buf *bb, uint32 *seq)
{
- const octet *pmac, *piv, *pseq, *ppk;
- size_t psz = BLEFT(b);
- size_t sz;
- octet *q = BCUR(bb);
- ghash *h;
- gcipher *c = ks->cin;
- size_t ivsz = GC_CLASS(c)->blksz;
- size_t tagsz = ks->tagsz;
- octet *mac;
- int eq;
- octet t[4];
-
- /* --- Break up the packet into its components --- */
-
- if (psz < ivsz + SEQSZ + tagsz) {
- T( trace(T_KEYSET, "keyset: block too small for keyset %u", ks->seq); )
- return (-1);
- }
- sz = psz - ivsz - SEQSZ - tagsz;
- pmac = BCUR(b); pseq = pmac + tagsz; piv = pseq + SEQSZ; ppk = piv + ivsz;
- STORE32(t, ty);
+ const octet *q = BCUR(bb);
+ int rc;
IF_TRACING(T_KEYSET, {
- trace(T_KEYSET, "keyset: decrypting using keyset %u", ks->seq);
- trace_block(T_CRYPTO, "crypto: ciphertext packet", ppk, sz);
+ trace(T_KEYSET,
+ "keyset: try decrypting packet (type 0x%02x) using keyset %u",
+ ty, ks->seq);
+ trace_block(T_CRYPTO, "crypto: ciphertext packet", BCUR(b), BLEFT(b));
})
- /* --- Verify the MAC on the packet --- */
-
- if (tagsz) {
- h = GM_INIT(ks->min);
- GH_HASH(h, t, sizeof(t));
- GH_HASH(h, pseq, SEQSZ + ivsz + sz);
- mac = GH_DONE(h, 0);
- eq = !memcmp(mac, pmac, tagsz);
- IF_TRACING(T_KEYSET, {
- trace_block(T_CRYPTO, "crypto: computed MAC", mac, tagsz);
- })
- GH_DESTROY(h);
- if (!eq) {
- IF_TRACING(T_KEYSET, {
- trace(T_KEYSET, "keyset: incorrect MAC: decryption failed");
- trace_block(T_CRYPTO, "crypto: expected MAC", pmac, tagsz);
- })
- return (-1);
- }
- }
-
- /* --- Decrypt the packet --- */
+ rc = ks->bulk->ops->decrypt(ks->bulk, ty, b, bb, seq);
+ if (rc) return (rc);
- if (ivsz) {
- GC_SETIV(c, piv);
- IF_TRACING(T_KEYSET, {
- trace_block(T_CRYPTO, "crypto: initialization vector", piv, ivsz);
- })
- }
- GC_DECRYPT(c, ppk, q, sz);
- if (seq)
- *seq = LOAD32(pseq);
IF_TRACING(T_KEYSET, {
trace(T_KEYSET, "keyset: decrypted OK (sequence = %lu)",
- (unsigned long)LOAD32(pseq));
- trace_block(T_CRYPTO, "crypto: decrypted packet", q, sz);
+ (unsigned long)*seq);
+ trace_block(T_CRYPTO, "crypto: decrypted packet", q, BCUR(bb) - q);
})
- BSTEP(bb, sz);
return (0);
}
void ks_drop(keyset *ks)
{
- if (--ks->ref)
- return;
- GC_DESTROY(ks->cin);
- GC_DESTROY(ks->cout);
- GM_DESTROY(ks->min);
- GM_DESTROY(ks->mout);
+ if (--ks->ref) return;
+ ks->bulk->ops->freectx(ks->bulk);
DESTROY(ks);
}
+/* --- @ks_derivekey@ --- *
+ *
+ * Arguments: @octet *k@ = pointer to an output buffer of at least
+ * @MAXHASHSZ@ bytes
+ * @size_t ksz@ = actual size wanted (for tracing)
+ * @const struct rawkey *rk@ = a raw key, as passed into
+ * @genkeys@
+ * @int dir@ = direction for the key (@DIR_IN@ or @DIR_OUT@)
+ * @const char *what@ = label for the key (input to derivation)
+ *
+ * Returns: ---
+ *
+ * Use: Derives a session key, for use on incoming or outgoing data.
+ * This function is part of a private protocol between @ks_gen@
+ * and the bulk crypto transform @genkeys@ operation.
+ */
+
+struct rawkey {
+ const gchash *hc;
+ const octet *k;
+ size_t x, y, z;
+};
+
+void ks_derivekey(octet *k, size_t ksz, const struct rawkey *rk,
+ int dir, const char *what)
+{
+ const gchash *hc = rk->hc;
+ ghash *h;
+
+ assert(ksz <= hc->hashsz);
+ assert(hc->hashsz <= MAXHASHSZ);
+ h = GH_INIT(hc);
+ GH_HASH(h, "tripe-", 6); GH_HASH(h, what, strlen(what) + 1);
+ switch (dir) {
+ case DIR_IN:
+ GH_HASH(h, rk->k, rk->x);
+ GH_HASH(h, rk->k + rk->x, rk->y - rk->x);
+ break;
+ case DIR_OUT:
+ GH_HASH(h, rk->k + rk->x, rk->y - rk->x);
+ GH_HASH(h, rk->k, rk->x);
+ break;
+ default:
+ abort();
+ }
+ GH_HASH(h, rk->k + rk->y, rk->z - rk->y);
+ GH_DONE(h, k);
+ GH_DESTROY(h);
+ IF_TRACING(T_KEYSET, { IF_TRACING(T_CRYPTO, {
+ char _buf[32];
+ sprintf(_buf, "crypto: %s key %s", dir ? "outgoing" : "incoming", what);
+ trace_block(T_CRYPTO, _buf, k, ksz);
+ }) })
+}
+
/* --- @ks_gen@ --- *
*
* Arguments: @const void *k@ = pointer to key material
* @size_t x, y, z@ = offsets into key material (see below)
- * @peer *p@ = pointer to peer information
+ * @peer *p@ = pointer to peer information
*
* Returns: A pointer to the new keyset.
*
* the key material; between @k + x@ and @k + y@ is `your'
* contribution; and between @k + y@ and @k + z@ is a shared
* value we made together. These are used to construct two
- * pairs of symmetric keys. Each pair consists of an encryption
- * key and a message authentication key. One pair is used for
- * outgoing messages, the other for incoming messages.
+ * collections of symmetric keys: one for outgoing messages, the
+ * other for incoming messages.
*
* The new key is marked so that it won't be selected for output
* by @ksl_encrypt@. You can still encrypt data with it by
keyset *ks_gen(const void *k, size_t x, size_t y, size_t z, peer *p)
{
- ghash *h;
- const octet *hh;
keyset *ks = CREATE(keyset);
time_t now = time(0);
- const octet *pp = k;
+ const algswitch *algs = &p->kx.kpriv->algs;
+ struct rawkey rk;
T( static unsigned seq = 0; )
T( trace(T_KEYSET, "keyset: adding new keyset %u", seq); )
- /* --- Construct the various keys --- *
- *
- * This is done with macros, because it's quite tedious.
- */
-
-#define MINE GH_HASH(h, pp, x)
-#define YOURS GH_HASH(h, pp + x, y - x)
-#define OURS GH_HASH(h, pp + y, z - y)
-
-#define HASH_in MINE; YOURS; OURS
-#define HASH_out YOURS; MINE; OURS
-#define INIT_c(k) GC_INIT(algs.c, (k), algs.cksz)
-#define INIT_m(k) GM_KEY(algs.m, (k), algs.mksz)
-#define STR_c "encryption"
-#define STR_m "integrity"
-#define STR_in "incoming"
-#define STR_out "outgoing"
-
-#define SETKEY(a, dir) do { \
- h = GH_INIT(algs.h); \
- HASH_STRING(h, "tripe-" STR_##a); \
- HASH_##dir; \
- hh = GH_DONE(h, 0); \
- IF_TRACING(T_KEYSET, { \
- trace_block(T_CRYPTO, "crypto: " STR_##dir " key " STR_##a, \
- hh, algs.a##ksz); \
- }) \
- ks->a##dir = INIT_##a(hh); \
- GH_DESTROY(h); \
-} while (0)
-
- SETKEY(c, in); SETKEY(c, out);
- SETKEY(m, in); SETKEY(m, out);
-
-#undef MINE
-#undef YOURS
-#undef OURS
-#undef STR_c
-#undef STR_m
-#undef STR_in
-#undef STR_out
-#undef INIT_c
-#undef INIT_m
-#undef HASH_in
-#undef HASH_out
-#undef SETKEY
+ rk.hc = algs->h; rk.k = k; rk.x = x; rk.y = y; rk.z = z;
+ ks->bulk = algs->bulk->ops->genkeys(algs->bulk, &rk);
+ ks->bulk->ops = algs->bulk->ops;
T( ks->seq = seq++; )
ks->ref = 1;
ks->t_exp = now + T_EXP;
- ks->sz_exp = SZ_EXP;
+ ks->sz_exp = algs->bulk->ops->expsz(algs->bulk);
+ ks->sz_regen = ks->sz_exp/2;
ks->oseq = 0;
seq_reset(&ks->iseq);
ks->next = 0;
ks->p = p;
ks->f = KSF_LISTEN;
- ks->tagsz = algs.tagsz;
return (ks);
}
-/* --- @ks_tregen@ --- *
- *
- * Arguments: @keyset *ks@ = pointer to a keyset
- *
- * Returns: The time at which moves ought to be made to replace this key.
- */
-
-time_t ks_tregen(keyset *ks) { return (ks->t_exp - T_EXP + T_REGEN); }
-
/* --- @ks_activate@ --- *
*
* Arguments: @keyset *ks@ = pointer to a keyset
* @buf *b@ = pointer to input buffer
* @buf *bb@ = pointer to output buffer
*
- * Returns: Zero if OK, nonzero if the key needs replacing. If the
- * encryption failed, the output buffer is broken and zero is
- * returned.
+ * Returns: Zero if successful; @KSERR_REGEN@ if we should negotiate a
+ * new key; @KSERR_NOKEYS@ if the key is not usable. Also
+ * returns zero if there was insufficient buffer (but the output
+ * buffer is broken in this case).
*
* Use: Encrypts a block of data using the key. Note that the `key
* ought to be replaced' notification is only ever given once
* for each key. Also note that this call forces a keyset to be
* used even if it's marked as not for data output.
+ *
+ * The encryption transform is permitted to corrupt @buf_u@ for
+ * its own purposes. Neither the source nor destination should
+ * be within @buf_u@; and callers mustn't expect anything stored
+ * in @buf_u@ to still
*/
int ks_encrypt(keyset *ks, unsigned ty, buf *b, buf *bb)
if (!KEYOK(ks, now)) {
buf_break(bb);
- return (0);
+ return (KSERR_NOKEYS);
}
return (doencrypt(ks, ty, b, bb));
}
* @buf *b@ = pointer to an input buffer
* @buf *bb@ = pointer to an output buffer
*
- * Returns: Zero on success, or nonzero if there was some problem.
+ * Returns: Zero on success; @KSERR_...@ on failure. Also returns
+ * zero if there was insufficient buffer (but the output buffer
+ * is broken in this case).
*
* Use: Attempts to decrypt a message using a given key. Note that
* requesting decryption with a key directly won't clear a
* marking that it's not for encryption.
+ *
+ * The decryption transform is permitted to corrupt @buf_u@ for
+ * its own purposes. Neither the source nor destination should
+ * be within @buf_u@; and callers mustn't expect anything stored
+ * in @buf_u@ to still
*/
int ks_decrypt(keyset *ks, unsigned ty, buf *b, buf *bb)
{
time_t now = time(0);
uint32 seq;
+ int err;
- if (!KEYOK(ks, now) ||
- buf_ensure(bb, BLEN(b)) ||
- dodecrypt(ks, ty, b, bb, &seq) ||
- seq_check(&ks->iseq, seq, "SYMM"))
- return (-1);
+ if (!KEYOK(ks, now)) return (KSERR_DECRYPT);
+ if (buf_ensure(bb, BLEN(b))) return (0);
+ if ((err = dodecrypt(ks, ty, b, bb, &seq)) != 0) return (err);
+ if (seq_check(&ks->iseq, seq, "SYMM")) return (KSERR_SEQ);
return (0);
}
* @buf *b@ = pointer to input buffer
* @buf *bb@ = pointer to output buffer
*
- * Returns: Nonzero if a new key is needed.
+ * Returns: Zero if successful; @KSERR_REGEN@ if it's time to negotiate a
+ * new key; @KSERR_NOKEYS@ if there are no suitable keys
+ * available. Also returns zero if there was insufficient
+ * buffer space (but the output buffer is broken in this case).
*
* Use: Encrypts a packet.
*/
if (!ks) {
T( trace(T_KEYSET, "keyset: no suitable keysets found"); )
buf_break(bb);
- return (-1);
+ return (KSERR_NOKEYS);
}
if (KEYOK(ks, now) && !(ks->f & KSF_LISTEN))
break;
* @buf *b@ = pointer to input buffer
* @buf *bb@ = pointer to output buffer
*
- * Returns: Nonzero if the packet couldn't be decrypted.
+ * Returns: Zero on success; @KSERR_DECRYPT@ on failure. Also returns
+ * zero if there was insufficient buffer (but the output buffer
+ * is broken in this case).
*
* Use: Decrypts a packet.
*/
time_t now = time(0);
keyset *ks;
uint32 seq;
+ int err;
if (buf_ensure(bb, BLEN(b)))
- return (-1);
+ return (0);
for (ks = *ksroot; ks; ks = ks->next) {
if (!KEYOK(ks, now))
continue;
- if (!dodecrypt(ks, ty, b, bb, &seq)) {
+ if ((err = dodecrypt(ks, ty, b, bb, &seq)) == 0) {
if (ks->f & KSF_LISTEN) {
T( trace(T_KEYSET, "keyset: implicitly activating keyset %u",
ks->seq); )
ks->f &= ~KSF_LISTEN;
}
- return (seq_check(&ks->iseq, seq, "SYMM"));
+ if (seq_check(&ks->iseq, seq, "SYMM"))
+ return (KSERR_SEQ);
+ else
+ return (0);
}
+ if (err != KSERR_DECRYPT) return (err);
}
T( trace(T_KEYSET, "keyset: no matching keys, or incorrect MAC"); )
- return (-1);
+ return (KSERR_DECRYPT);
}
/*----- That's all, folks -------------------------------------------------*/