The padding may be also necessary to prevent from a kind of attacks, besides hiding the length. But I cannot recall the details.
Removing padding may be not the direction. Instead, a padding length customizable solution may be more flexible. Here is an enhancement request in JBS (https://bugs.openjdk.org/browse/JDK-8244983 <https://bugs.openjdk.org/browse/JDK-8244983>), please feel free to take it. Xuelei > On Nov 4, 2022, at 4:21 AM, Daniel Jeliński <djelins...@gmail.com> wrote: > > Hello, > I noticed that we're padding every TLS 1.3 record with exactly 16 zeros [1]. > I'd like to remove that padding to conserve network bandwidth and processing > power. Thoughts? > > Some background: > - TLS 1.3 RFC [2] defines padding as a means to hide the size of the traffic. > Constant-length padding does not hide it, obviously. The RFC does not define > any padding policies ("Selecting a padding policy that suggests when and how > much to pad is a complex topic and is beyond the scope of this > specification.") > - OpenSSL [3] defines 2 methods to select the length of the padding block: > the user may provide a callback that selects adequate padding length, or > provide block length, and then every record is padded to a multiple of block > length. By default OpenSSL does not pad records. > - I'm not aware of any discussions around record padding on this list, which > suggests that there's no demand for more complex padding schemes. > > Regards, > Daniel > > [1] > https://github.com/openjdk/jdk/blob/4cec141a90bc5d3b8ec17c024291d9c74a112cd4/src/java.base/share/classes/sun/security/ssl/OutputRecord.java#L302 > > <https://github.com/openjdk/jdk/blob/4cec141a90bc5d3b8ec17c024291d9c74a112cd4/src/java.base/share/classes/sun/security/ssl/OutputRecord.java#L302> > [2] https://www.rfc-editor.org/rfc/rfc8446.html#section-5.4 > <https://www.rfc-editor.org/rfc/rfc8446.html#section-5.4> > [3] > https://www.openssl.org/docs/man1.1.1/man3/SSL_set_record_padding_callback.html > > <https://www.openssl.org/docs/man1.1.1/man3/SSL_set_record_padding_callback.html>
