Clean up BN_mod_mul() and simplify BN_mod_sqr().

Use the same naming/code pattern in BN_mod_mul() as is used in BN_mul().
Note that the 'rr' allocation is unnecessary, since both BN_mul() and
BN_sqr() handle the case where r == a || r == b. However, it avoids a
potential copy on the exit from BN_mul()/BN_sqr(), so leave it in place
for now.

Turn BN_mod_sqr() into a wrapper that calls BN_mod_mul(), since it already
calls BN_sqr() in the a == b. The supposed gain of calling BN_mod_ct()
instead of BN_nnmod() does not really exist.

ok tb@

1 files changed, 16 insertions, 14 deletions

diff --git a/src/lib/libcrypto/bn/bn_mod.c b/src/lib/libcrypto/bn/bn_mod.c
index 4a62715974..762ffb5580 100644
--- a/src/lib/libcrypto/bn/bn_mod.c
+++ b/src/lib/libcrypto/bn/bn_mod.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_mod.c,v 1.17 2023/02/03 05:06:20 jsing Exp $ */
+/* $OpenBSD: bn_mod.c,v 1.18 2023/02/03 05:10:57 jsing Exp $ */
 /* Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
  * for the OpenSSL project. */
 /* ====================================================================
@@ -189,41 +189,43 @@ BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m)
         return BN_usub(r, m, r);
 }
 
-/* slow but works */
 int
 BN_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
     BN_CTX *ctx)
 {
-        BIGNUM *t;
+        BIGNUM *rr;
         int ret = 0;
 
-
         BN_CTX_start(ctx);
-        if ((t = BN_CTX_get(ctx)) == NULL)
+
+        rr = r;
+        if (rr == a || rr == b)
+                rr = BN_CTX_get(ctx);
+        if (rr == NULL)
                 goto err;
+
         if (a == b) {
-                if (!BN_sqr(t, a, ctx))
+                if (!BN_sqr(rr, a, ctx))
                         goto err;
         } else {
-                if (!BN_mul(t, a,b, ctx))
+                if (!BN_mul(rr, a, b, ctx))
                         goto err;
         }
-        if (!BN_nnmod(r, t,m, ctx))
+        if (!BN_nnmod(r, rr, m, ctx))
                 goto err;
+
         ret = 1;
 
-err:
+ err:
         BN_CTX_end(ctx);
-        return (ret);
+
+        return ret;
 }
 
 int
 BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
 {
-        if (!BN_sqr(r, a, ctx))
-                return 0;
-        /* r->neg == 0,  thus we don't need BN_nnmod */
-        return BN_mod_ct(r, r, m, ctx);
+        return BN_mod_mul(r, a, a, m, ctx);
 }
 
 int