Hans Leidekker : bcrypt: Fix buffer size query in BCryptSignHash.

[Alexandre Julliard]

Module: wine
Branch: master
Commit: ab0a7d2a1b31160134d9205236fade162f0bc1dc
URL:    https://source.winehq.org/git/wine.git/?a=commit;h=ab0a7d2a1b31160134d9205236fade162f0bc1dc

Author: Hans Leidekker <hans at codeweavers.com>
Date:   Tue Oct  6 12:27:10 2020 +0200

bcrypt: Fix buffer size query in BCryptSignHash.

Signed-off-by: Hans Leidekker <hans at codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard at winehq.org>

---

 dlls/bcrypt/gnutls.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/dlls/bcrypt/gnutls.c b/dlls/bcrypt/gnutls.c
index 21520bb4a8..be1a28e472 100644
--- a/dlls/bcrypt/gnutls.c
+++ b/dlls/bcrypt/gnutls.c
@@ -1415,9 +1415,9 @@ static NTSTATUS format_gnutls_signature( enum alg_id type, gnutls_datum_t signat
     case ALG_ID_RSA:
     case ALG_ID_RSA_SIGN:
     {
-        if (output_len < signature.size) return STATUS_BUFFER_TOO_SMALL;
-        memcpy( output, signature.data, signature.size );
         *ret_len = signature.size;
+        if (output_len < signature.size) return STATUS_BUFFER_TOO_SMALL;
+        if (output) memcpy( output, signature.data, signature.size );
         return STATUS_SUCCESS;
     }
     case ALG_ID_ECDSA_P256:
@@ -1435,6 +1435,7 @@ static NTSTATUS format_gnutls_signature( enum alg_id type, gnutls_datum_t signat
             return STATUS_INTERNAL_ERROR;
         }
 
+        *ret_len = sig_len;
         if (output_len < sig_len) return STATUS_BUFFER_TOO_SMALL;
 
         if (r.size % 2) /* remove prepended zero byte */
@@ -1457,14 +1458,16 @@ static NTSTATUS format_gnutls_signature( enum alg_id type, gnutls_datum_t signat
             return STATUS_INTERNAL_ERROR;
         }
 
-        pad_size_r = (sig_len / 2) - r.size;
-        pad_size_s = (sig_len / 2) - s.size;
-        memset( output, 0, sig_len );
+        if (output)
+        {
+            pad_size_r = (sig_len / 2) - r.size;
+            pad_size_s = (sig_len / 2) - s.size;
+            memset( output, 0, sig_len );
 
-        memcpy( output + pad_size_r, r_data, r.size );
-        memcpy( output + (sig_len / 2) + pad_size_s, s_data, s.size );
+            memcpy( output + pad_size_r, r_data, r.size );
+            memcpy( output + (sig_len / 2) + pad_size_s, s_data, s.size );
+        }
 
-        *ret_len = sig_len;
         free( r.data ); free( s.data );
         return STATUS_SUCCESS;
     }