1 files changed, 58 insertions, 35 deletions

diff --git a/src/lib/libcrypto/bn/bn_convert.c b/src/lib/libcrypto/bn/bn_convert.c
index 60075e53ed..2b12670ea5 100644
--- a/src/lib/libcrypto/bn/bn_convert.c
+++ b/src/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);