server/bulkcrypto.c: Fix description comment for AEAD schemes.

[tripe] / server / bulkcrypto.c

diff --git a/server/bulkcrypto.c b/server/bulkcrypto.c
index 4e98ea1263408b59e9952f78fd35fc6dcf95af3d..92e67c058b924269704eb12725a0bf4c119ae01f 100644 (file)
--- a/server/bulkcrypto.c
+++ b/server/bulkcrypto.c
@@ -816,17 +816,18 @@ static int iiv_decrypt(bulkctx *bbc, unsigned ty,
 
 /*----- The AEAD transform ------------------------------------------------*
  *
- * This transform uses a general authenticated encryption scheme (the
- * additional data isn't necessary).  Good options include
- * `chacha20-poly1305' or `rijndael-ocb3'.
+ * This transform uses a general authenticated encryption scheme.  Processing
+ * additional authenticated data isn't needed for encrypting messages, but it
+ * is required for challenge generation.  Good options include `chacha20-
+ * poly1305' or `rijndael-ocb3'; alas, `salsa20-naclbox' isn't acceptable.
  *
  * To be acceptable, the scheme must accept at least a 40-bit nonce.  (All of
- * Catacomb's current AEAD schemes are suitable.)  The low 32 bits are the
- * sequence number.  The type is written to the next 8--32 bytes: if the
- * nonce size is 64 bits or more (preferred, for compatibility reasons) then
- * the type is written as 32 bits, and the remaining space is padded with
- * zero bytes; otherwise, the type is right-aligned in the remaining space.
- * Both fields are big-endian.
+ * Catacomb's current AEAD schemes are suitable in this respect.)  The low 32
+ * bits are the sequence number.  The type is written to the next 8--32
+ * bytes: if the nonce size is 64 bits or more (preferred, for compatibility
+ * reasons) then the type is written as 32 bits, and the remaining space is
+ * padded with zero bytes; otherwise, the type is right-aligned in the
+ * remaining space.  Both fields are big-endian.
  *
  *             +--------+--+
  *             |  seq   |ty|
@@ -1321,7 +1322,8 @@ static int naclbox_chaltag(bulkchal *bc, const void *m, size_t msz,
   poly1305_ctx pm;
   octet b[POLY1305_KEYSZ + POLY1305_MASKSZ];
 
-  assert(SALSA20_NONCESZ <= sizeof(b));
+  STATIC_ASSERT(SALSA20_NONCESZ <= sizeof(b), "Need more space for nonce");
+
   memset(b, 0, SALSA20_NONCESZ - 4); STORE32(b + SALSA20_NONCESZ - 4, seq);
   GC_SETIV(c->c, b); GC_ENCRYPT(c->c, 0, b, sizeof(b));
   poly1305_keyinit(&pk, b, POLY1305_KEYSZ);
@@ -1339,13 +1341,15 @@ static int naclbox_chalvrf(bulkchal *bc, const void *m, size_t msz,
   poly1305_ctx pm;
   octet b[POLY1305_KEYSZ + POLY1305_MASKSZ];
 
-  assert(SALSA20_NONCESZ <= sizeof(b));
+  STATIC_ASSERT(SALSA20_NONCESZ <= sizeof(b), "Need more space for nonce");
+  STATIC_ASSERT(POLY1305_TAGSZ <= sizeof(b), "Need more space for tag");
+
   memset(b, 0, SALSA20_NONCESZ - 4); STORE32(b + SALSA20_NONCESZ - 4, seq);
   GC_SETIV(c->c, b); GC_ENCRYPT(c->c, 0, b, sizeof(b));
   poly1305_keyinit(&pk, b, POLY1305_KEYSZ);
   poly1305_macinit(&pm, &pk, b + POLY1305_KEYSZ);
   if (msz) poly1305_hash(&pm, m, msz);
-  assert(POLY1305_TAGSZ <= sizeof(b)); poly1305_done(&pm, b);
+  poly1305_done(&pm, b);
   return (ct_memeq(t, b, POLY1305_TAGSZ) ? 0 : -1);
 }