X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/tripe/blobdiff_plain/786989941b7b4504f0234c4a318f929802e981ad..12a26b8b34df23103d4da6d7e40705485266a4d6:/server/keyset.c

diff --git a/server/keyset.c b/server/keyset.c
index bb2397fc..1f580ff7 100644
--- a/server/keyset.c
+++ b/server/keyset.c
@@ -1,13 +1,11 @@
 /* -*-c-*-
- *
- * $Id$
  *
  * Handling of symmetric keysets
  *
  * (c) 2001 Straylight/Edgeware
  */
 
-/*----- Licensing notice --------------------------------------------------* 
+/*----- Licensing notice --------------------------------------------------*
  *
  * This file is part of Trivial IP Encryption (TrIPE).
  *
@@ -15,12 +13,12 @@
  * 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.
- * 
+ *
  * 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.
@@ -32,18 +30,8 @@
 
 /*----- 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 ------------------------------------------------------*/
 
@@ -56,7 +44,7 @@
 /* --- Encrypted data format --- *
  *
  * Let %$p_i$% be the %$i$%-th plaintext message, with type %$t$%.  We first
- * compute 
+ * compute
  *
  *   %$c_i = \mathcal{E}\textrm{-CBC}_{K_{\text{E}}}(p_i)$%
  *
@@ -84,7 +72,9 @@
  *		@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.
@@ -153,13 +143,13 @@ static int doencrypt(keyset *ks, unsigned ty, buf *b, buf *bb)
     nsz = osz - sz;
   else
     nsz = 0;
-  if (osz >= SZ_REGEN && nsz < SZ_REGEN) {
+  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);  
+  return (rc);
 }
 
 /* --- @dodecrypt@ --- *
@@ -170,7 +160,7 @@ static int doencrypt(keyset *ks, unsigned ty, buf *b, buf *bb)
  *		@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
@@ -198,7 +188,7 @@ static int dodecrypt(keyset *ks, unsigned ty, buf *b, buf *bb, uint32 *seq)
 
   if (psz < ivsz + SEQSZ + tagsz) {
     T( trace(T_KEYSET, "keyset: block too small for keyset %u", ks->seq); )
-    return (-1);
+    return (KSERR_MALFORMED);
   }
   sz = psz - ivsz - SEQSZ - tagsz;
   pmac = BCUR(b); pseq = pmac + tagsz; piv = pseq + SEQSZ; ppk = piv + ivsz;
@@ -226,7 +216,7 @@ static int dodecrypt(keyset *ks, unsigned ty, buf *b, buf *bb, uint32 *seq)
 	trace(T_KEYSET, "keyset: incorrect MAC: decryption failed");
 	trace_block(T_CRYPTO, "crypto: expected MAC", pmac, tagsz);
       })
-      return (-1);
+      return (KSERR_DECRYPT);
     }
   }
 
@@ -277,7 +267,7 @@ void ks_drop(keyset *ks)
  *
  * 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.
  *
@@ -357,7 +347,8 @@ keyset *ks_gen(const void *k, size_t x, size_t y, size_t z, peer *p)
   T( ks->seq = seq++; )
   ks->ref = 1;
   ks->t_exp = now + T_EXP;
-  ks->sz_exp = SZ_EXP;
+  ks->sz_exp = algs.expsz;
+  ks->sz_regen = algs.expsz/2;
   ks->oseq = 0;
   seq_reset(&ks->iseq);
   ks->next = 0;
@@ -401,9 +392,10 @@ void ks_activate(keyset *ks)
  *		@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
@@ -417,7 +409,7 @@ 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));
 }
@@ -429,7 +421,9 @@ int ks_encrypt(keyset *ks, unsigned ty, buf *b, buf *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
@@ -440,12 +434,12 @@ 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);
 }
 
@@ -534,7 +528,10 @@ void ksl_prune(keyset **ksroot)
  *		@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.
  */
@@ -548,7 +545,7 @@ int ksl_encrypt(keyset **ksroot, unsigned ty, buf *b, buf *bb)
     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;
@@ -565,7 +562,9 @@ int ksl_encrypt(keyset **ksroot, unsigned ty, buf *b, buf *bb)
  *		@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.
  */
@@ -575,24 +574,29 @@ int ksl_decrypt(keyset **ksroot, unsigned ty, buf *b, buf *bb)
   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 -------------------------------------------------*/