Invert BN_BITS2 handling in bn_bin2bn_cbs() and bn_hex2bn_cbs().

This results in simpler code.

Suggested by tb@ during review.

diff --git a/lib/libcrypto/bn/bn_convert.c b/lib/libcrypto/bn/bn_convert.c
index 2b12670..5c3c98b 100644 (file)
--- a/lib/libcrypto/bn/bn_convert.c
+++ b/lib/libcrypto/bn/bn_convert.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_convert.c,v 1.17 2024/04/16 13:11:37 jsing Exp $ */
+/* $OpenBSD: bn_convert.c,v 1.18 2024/04/16 13:14:46 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -168,7 +168,7 @@ bn_bin2bn_cbs(BIGNUM **bnp, CBS *cbs)
        if (!bn_expand_bytes(bn, CBS_len(cbs)))
                goto err;
 
-       b = BN_BITS2;
+       b = 0;
        i = 0;
        w = 0;
 
@@ -176,11 +176,11 @@ bn_bin2bn_cbs(BIGNUM **bnp, CBS *cbs)
                if (!CBS_get_last_u8(cbs, &v))
                        goto err;
 
-               w |= (BN_ULONG)v << (BN_BITS2 - b);
-               b -= 8;
+               w |= (BN_ULONG)v << b;
+               b += 8;
 
-               if (b == 0 || CBS_len(cbs) == 0) {
-                       b = BN_BITS2;
+               if (b == BN_BITS2 || CBS_len(cbs) == 0) {
+                       b = 0;
                        bn->d[i++] = w;
                        w = 0;
                }
@@ -657,7 +657,7 @@ bn_hex2bn_cbs(BIGNUM **bnp, CBS *cbs)
        if (!CBS_get_bytes(cbs, cbs, digits))
                goto err;
 
-       b = BN_BITS2;
+       b = 0;
        i = 0;
        w = 0;
 
@@ -675,11 +675,11 @@ bn_hex2bn_cbs(BIGNUM **bnp, CBS *cbs)
                else
                        goto err;
 
-               w |= (BN_ULONG)v << (BN_BITS2 - b);
-               b -= 4;
+               w |= (BN_ULONG)v << b;
+               b += 4;
 
-               if (b == 0 || digits == 0) {
-                       b = BN_BITS2;
+               if (b == BN_BITS2 || digits == 0) {
+                       b = 0;
                        bn->d[i++] = w;
                        w = 0;
                }