Provide bn_expand_bytes().

This will be used in an upcoming change.

ok tb@

2 files changed, 16 insertions, 2 deletions

diff --git a/src/lib/libcrypto/bn/bn_lib.c b/src/lib/libcrypto/bn/bn_lib.c
index 6988a70f3b..72b988650c 100644
--- a/src/lib/libcrypto/bn/bn_lib.c
+++ b/src/lib/libcrypto/bn/bn_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_lib.c,v 1.92 2024/04/16 13:04:05 jsing Exp $ */
+/* $OpenBSD: bn_lib.c,v 1.93 2024/04/16 13:07:14 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -232,6 +232,19 @@ bn_expand_bits(BIGNUM *bn, size_t bits)
 }
 
 int
+bn_expand_bytes(BIGNUM *bn, size_t bytes)
+{
+        int words;
+
+        if (bytes > (INT_MAX - BN_BYTES + 1))
+                return 0;
+
+        words = (bytes + BN_BYTES - 1) / BN_BYTES;
+
+        return bn_wexpand(bn, words);
+}
+
+int
 bn_wexpand(BIGNUM *bn, int words)
 {
         if (words < 0)
diff --git a/src/lib/libcrypto/bn/bn_local.h b/src/lib/libcrypto/bn/bn_local.h
index cffc5a2ea1..58b5d54903 100644
--- a/src/lib/libcrypto/bn/bn_local.h
+++ b/src/lib/libcrypto/bn/bn_local.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_local.h,v 1.42 2024/04/16 13:04:05 jsing Exp $ */
+/* $OpenBSD: bn_local.h,v 1.43 2024/04/16 13:07:14 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -260,6 +260,7 @@ int bn_mul_mont(BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp,
 
 void bn_correct_top(BIGNUM *a);
 int bn_expand_bits(BIGNUM *a, size_t bits);
+int bn_expand_bytes(BIGNUM *a, size_t bytes);
 int bn_wexpand(BIGNUM *a, int words);
 
 BN_ULONG bn_add_words(BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp,