Rewrite BN_bin2bn() using CBS.

ok tb@

diff --git a/lib/libcrypto/bn/bn_convert.c b/lib/libcrypto/bn/bn_convert.c
index 60075e5..2b12670 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 1.16 2024/04/16 13:04:05 jsing Exp $ */
+/* $OpenBSD: bn_convert.c,v 1.17 2024/04/16 13:11:37 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -153,46 +153,69 @@ BN_bn2binpad(const BIGNUM *a, unsigned char *to, int tolen)
 }
 LCRYPTO_ALIAS(BN_bn2binpad);
 
-BIGNUM *
-BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
+static int
+bn_bin2bn_cbs(BIGNUM **bnp, CBS *cbs)
 {
-       unsigned int i, m;
-       unsigned int n;
-       BN_ULONG l;
        BIGNUM *bn = NULL;
+       BN_ULONG w;
+       uint8_t v;
+       int b, i;
 
-       if (len < 0)
-               return (NULL);
-       if (ret == NULL)
-               ret = bn = BN_new();
-       if (ret == NULL)
-               return (NULL);
-       l = 0;
-       n = len;
-       if (n == 0) {
-               ret->top = 0;
-               return (ret);
+       if ((bn = *bnp) == NULL)
+               bn = BN_new();
+       if (bn == NULL)
+               goto err;
+       if (!bn_expand_bytes(bn, CBS_len(cbs)))
+               goto err;
+
+       b = BN_BITS2;
+       i = 0;
+       w = 0;
+
+       while (CBS_len(cbs) > 0) {
+               if (!CBS_get_last_u8(cbs, &v))
+                       goto err;
+
+               w |= (BN_ULONG)v << (BN_BITS2 - b);
+               b -= 8;
+
+               if (b == 0 || CBS_len(cbs) == 0) {
+                       b = BN_BITS2;
+                       bn->d[i++] = w;
+                       w = 0;
+               }
        }
-       i = ((n - 1) / BN_BYTES) + 1;
-       m = ((n - 1) % (BN_BYTES));
-       if (!bn_wexpand(ret, (int)i)) {
+
+       bn->neg = 0;
+       bn->top = i;
+
+       bn_correct_top(bn);
+
+       *bnp = bn;
+
+       return 1;
+
+ err:
+       if (*bnp == NULL)
                BN_free(bn);
+
+       return 0;
+}
+
+BIGNUM *
+BN_bin2bn(const unsigned char *d, int len, BIGNUM *bn)
+{
+       CBS cbs;
+
+       if (len < 0)
                return NULL;
-       }
-       ret->top = i;
-       ret->neg = 0;
-       while (n--) {
-               l = (l << 8L) | *(s++);
-               if (m-- == 0) {
-                       ret->d[--i] = l;
-                       l = 0;
-                       m = BN_BYTES - 1;
-               }
-       }
-       /* need to call this due to clear byte at top if avoiding
-        * having the top bit set (-ve number) */
-       bn_correct_top(ret);
-       return (ret);
+
+       CBS_init(&cbs, d, len);
+
+       if (!bn_bin2bn_cbs(&bn, &cbs))
+               return NULL;
+
+       return bn;
 }
 LCRYPTO_ALIAS(BN_bin2bn);