ssl: Fix -Wconversion warnings in pem_password_callback

The OpenSSL API is how it is, so adapt with casts.

Change-Id: I053ddbb71cc5b9ae16c5a49be833035d943d7eba
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1137
Message-Id: <20250922204158.23319-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg33154.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

Author: flichtenheld

src/openvpn/ssl.c

@@ -264,10 +264,10 @@ pem_password_callback(char *buf, int size, int rwflag, void *u)
         /* prompt for password even if --askpass wasn't specified */
         pem_password_setup(NULL);
         ASSERT(!passbuf.protected);
-        strncpynt(buf, passbuf.password, size);
+        strncpynt(buf, passbuf.password, (size_t)size);
         purge_user_pass(&passbuf, false);
 
-        return strlen(buf);
+        return (int)strlen(buf);
     }
     return 0;
 }