Paul Gofman : bcrypt: Fix padding in format_gnutls_signature().

[Alexandre Julliard]

Module: wine
Branch: master
Commit: 085f9fb198ecf0eeb3116b22660bd45439d7ddf0
URL:    https://source.winehq.org/git/wine.git/?a=commit;h=085f9fb198ecf0eeb3116b226...

Author: Paul Gofman 
Date:   Mon Jan 18 12:38:29 2021 +0100

bcrypt: Fix padding in format_gnutls_signature().

Signed-off-by: Paul Gofman 
Signed-off-by: Hans Leidekker 
Signed-off-by: Alexandre Julliard

---

dlls/bcrypt/gnutls.c | 27 ++++-----------------------
 1 file changed, 4 insertions(+), 23 deletions(-)

diff --git a/dlls/bcrypt/gnutls.c b/dlls/bcrypt/gnutls.c
index 2981dc6bc9c..efab65b8315 100644
--- a/dlls/bcrypt/gnutls.c
+++ b/dlls/bcrypt/gnutls.c
@@ -1641,9 +1641,8 @@ static NTSTATUS format_gnutls_signature( enum alg_id type, gnutls_datum_t signat
     case ALG_ID_DSA:
     {
         int err;
-        unsigned int pad_size_r, pad_size_s, sig_len = get_signature_length( type );
+        unsigned int sig_len = get_signature_length( type );
         gnutls_datum_t r, s; /* format as r||s */
-        unsigned char *r_data, *s_data;

if ((err = pgnutls_decode_rs_value( &signature, &r, &s )))
         {
@@ -1654,21 +1653,7 @@ static NTSTATUS format_gnutls_signature( enum alg_id type, gnutls_datum_t signat
         *ret_len = sig_len;
         if (output_len < sig_len) return STATUS_BUFFER_TOO_SMALL;

-        if (r.size % 2) /* remove prepended zero byte */
-        {
-            r.size--;
-            r_data = r.data + 1;
-        }
-        else r_data = r.data;
-
-        if (s.size % 2)
-        {
-            s.size--;
-            s_data = s.data + 1;
-        }
-        else s_data = s.data;
-
-        if (r.size + s.size > sig_len)
+        if (r.size > sig_len / 2 + 1 || s.size > sig_len / 2 + 1)
         {
             ERR( "we didn't get a correct signature\n" );
             return STATUS_INTERNAL_ERROR;
@@ -1676,12 +1661,8 @@ static NTSTATUS format_gnutls_signature( enum alg_id type, gnutls_datum_t signat

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 );
+            export_gnutls_datum( output, sig_len / 2, &r, NULL );
+            export_gnutls_datum( output + sig_len / 2, sig_len / 2, &s, NULL );
         }

free( r.data ); free( s.data );