X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/tripe/blobdiff_plain/a50f9a0eaed03dfe85ff3d7a4c24da20ac705dae..46401b81fe5fab9b0d3d3a5f5764bafa3f9c0b86:/server/keyset.c

diff --git a/server/keyset.c b/server/keyset.c
index 9dd17fac..1f580ff7 100644
--- a/server/keyset.c
+++ b/server/keyset.c
@@ -30,18 +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 ------------------------------------------------------*/
 
@@ -153,7 +143,7 @@ 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 = KSERR_REGEN;
@@ -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 (KSERR_DECRYPT);
+    return (KSERR_MALFORMED);
   }
   sz = psz - ivsz - SEQSZ - tagsz;
   pmac = BCUR(b); pseq = pmac + tagsz; piv = pseq + SEQSZ; ppk = piv + ivsz;
@@ -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;
@@ -430,7 +421,7 @@ 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; @KSERR_DECRYPT@ on failure.  Also returns
+ * Returns:	Zero on success; @KSERR_...@ on failure.  Also returns
  *		zero if there was insufficient buffer (but the output buffer
  *		is broken in this case).
  *
@@ -443,12 +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 (KSERR_DECRYPT);
+  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);
 }
 
@@ -583,24 +574,26 @@ 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 (KSERR_DECRYPT);
+    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;
       }
       if (seq_check(&ks->iseq, seq, "SYMM"))
-	return (KSERR_DECRYPT);
+	return (KSERR_SEQ);
       else
 	return (0);
     }
+    if (err != KSERR_DECRYPT) return (err);
   }
   T( trace(T_KEYSET, "keyset: no matching keys, or incorrect MAC"); )
   return (KSERR_DECRYPT);