server/keyexch.c: Don't copy group elements when registering a challenge.

Instead, just remember that ownership has been transferred.  For `c', we
don't use the original variable any more, so we can just mark it null;
but `r' gets reused, so allocate a fresh place for it.

This is the only use of `G_COPY' in the program.

diff --git a/server/keyexch.c b/server/keyexch.c
index 7b4eb0d83a7200d44f6fcec1f82bd61cbc7d5f63..0c1ed829bddc80a73e09c2a20b6a50f802ec502b 100644 (file)
--- a/server/keyexch.c
+++ b/server/keyexch.c
@@ -427,6 +427,8 @@ static void kxc_stoptimer(kxchal *kxc)
  * Returns:    A pointer to the challenge block.
  *
  * Use:                Returns a pointer to a new challenge block to fill in.
+ *             In particular, the @c@ and @r@ members are left
+ *             uninitialized.
  */
 
 static kxchal *kxc_new(keyexch *kx)
@@ -446,8 +448,6 @@ static kxchal *kxc_new(keyexch *kx)
   /* --- Fill in the new structure --- */
 
   kxc = CREATE(kxchal);
-  kxc->c = G_CREATE(kx->kpriv->g);
-  kxc->r = G_CREATE(kx->kpriv->g);
   kxc->ks = 0;
   kxc->kx = kx;
   kxc->f = 0;
@@ -693,8 +693,8 @@ static kxchal *respond(keyexch *kx, unsigned msg, buf *b)
     /* --- Fill in a new challenge block --- */
 
     kxc = kxc_new(kx);
-    G_COPY(g, kxc->c, c);
-    G_COPY(g, kxc->r, r);
+    kxc->c = c; c = 0;
+    kxc->r = r; r = G_CREATE(g);
 
     h = GH_INIT(algs->h); HASH_STRING(h, "tripe-check-hash");
     GH_HASH(h, ck, ixsz);
@@ -711,7 +711,7 @@ static kxchal *respond(keyexch *kx, unsigned msg, buf *b)
 
     /* --- Work out the shared key --- */
 
-    G_EXP(g, r, c, kx->alpha);
+    G_EXP(g, r, kxc->c, kx->alpha);
     IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, {
       trace(T_CRYPTO, "crypto: shared secret = %s", gestr(g, r));
     }))
@@ -754,7 +754,7 @@ static kxchal *respond(keyexch *kx, unsigned msg, buf *b)
     kxc->ks = ks_gen(BBASE(&bb), x, y, z, kx->p);
   }
 
-  G_DESTROY(g, c);
+  if (c) G_DESTROY(g, c);
   G_DESTROY(g, cc);
   G_DESTROY(g, r);
   mp_drop(cv);
@@ -764,7 +764,7 @@ badcheck:
   a_warn("KX", "?PEER", kx->p, "bad-expected-reply-log", A_END);
   goto bad;
 bad:
-  G_DESTROY(g, c);
+  if (c) G_DESTROY(g, c);
   G_DESTROY(g, cc);
   G_DESTROY(g, r);
   mp_drop(cv);