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Update the API documentation for the latest early data changes

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Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2737)
This commit is contained in:
Matt Caswell 2017-03-02 16:05:02 +00:00
parent 09f2887482
commit cd9f7f624e
1 changed files with 28 additions and 26 deletions
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54
doc/man3/SSL_read_early.pod
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@ -30,17 +30,17 @@ SSL_get_early_data_status
=head1 DESCRIPTION
These functions are used to send and recieve early data. Early data can be sent
by the client immediately after its initial ClientHello without having to wait
for the server to complete the handshake. Early data can only be sent if a
session has previously been established with the server, and the server is known
to support it. Additionally these functions can be used to send data from the
server to the client when the client has not yet completed the authentication
stage of the handshake.
These functions are used to send and recieve early data where TLSv1.3 has been
negotiated. Early data can be sent by the client immediately after its initial
ClientHello without having to wait for the server to complete the handshake.
Early data can only be sent if a session has previously been established with
the server, and the server is known to support it. Additionally these functions
can be used to send data from the server to the client when the client has not
yet completed the authentication stage of the handshake.
Early data has weaker security properties than other data sent over an SSL/TLS
connection. In particular the data is not forward secret and the server has no
guarantees that the same early data was not replayed across multiple
connection. In particular the data does not have forward secrecy and there are
no guarantees that the same early data was not replayed across multiple
connections. For this reason extreme care should be exercised when using early
data.
@ -48,22 +48,23 @@ When a server receives early data it may opt to immediately respond by sending
application data back to the client. Data sent by the server at this stage is
done before the full handshake has been completed. Specifically the client's
authentication messages have not yet been received, i.e. the client is
unauthenticated at this point.
unauthenticated at this point and care should be taken when using this
capability.
A server or client can determine whether the full handshake has been completed
or not by calling L<SSL_is_init_finished(3)>.
On the client side the function SSL_SESSION_get_max_early_data() can be used to
determine whether a session established with a server can be used to send early
data. If the session cannot be used then this function will return 0. Otherwise
it will return the maximum number of early data bytes that can be sent.
On the client side, the function SSL_SESSION_get_max_early_data() can be used to
determine if a session established with a server can be used to send early data.
If the session cannot be used then this function will return 0. Otherwise it
will return the maximum number of early data bytes that can be sent.
A client uses the function SSL_write_early_data() to send early data. This
function works in the same way as the L<SSL_write_ex(3)> function, but with a
few differences. Refer to the L<SSL_write_ex(3)> documentation for
information on how to write bytes to the underlying connection, and how to
handle any errors that may arise. This page will detail the differences between
SSL_write_early_data() and L<SSL_write_ex(3)>.
function is similar to the L<SSL_write_ex(3)> function, but with the following
differences. See L<SSL_write_ex(3)> for information on how to write bytes to
the underlying connection, and how to handle any errors that may arise. This
page describes the differences between SSL_write_early_data() and
L<SSL_write_ex(3)>.
When called by a client, SSL_write_early_data() must be the first IO function
called on a new connection, i.e. it must occur before any calls to
@ -97,9 +98,8 @@ called on a connection, i.e. it must occur before any calls to
L<SSL_write_ex(3)>, L<SSL_read_ex(3)>, L<SSL_accept(3)>, L<SSL_do_handshake(3)>,
or other similar functions.
SSL_read_early_data() works in the same way as L<SSL_read_ex(3)> except for the
differences noted here. Refer to the L<SSL_read_ex(3)> documentation for full
details.
SSL_read_early_data() is similar to L<SSL_read_ex(3)> with the following
differences. Refer to L<SSL_read_ex(3)> for full details.
SSL_read_early_data() may return 3 possible values:
@ -129,7 +129,7 @@ has returned SSL_READ_EARLY_DATA_SUCCESS or SSL_READ_EARLY_DATA_FINISH) then the
server may choose to write data immediately to the unauthenticated client using
SSL_write_early_data(). If SSL_read_early_data() returned
SSL_READ_EARLY_DATA_FINISH then in some situations (e.g. if the client only
support TLSv1.2) the handshake may have already been completed and calls
supports TLSv1.2) the handshake may have already been completed and calls
to SSL_write_early_data() are not allowed. Call L<SSL_is_init_finished(3)> to
determine whether the handshake has completed or not. If the handshake is still
in progress then the server may interleave calls to SSL_write_early_data() with
@ -149,7 +149,8 @@ Only servers may call SSL_read_early_data().
Calls to SSL_read_early_data() may, in certain circumstances, complete the
connection immediately without further need to call a function such as
L<SSL_accept(3)>. Applications can test for this by calling
L<SSL_accept(3)>. This can happen if the client is using a protocol version less
than TLSv1.3. Applications can test for this by calling
L<SSL_is_init_finished(3)>. Alternatively, applications may choose to call
L<SSL_accept(3)> anway. Such a call will successfully return immediately with no
further action taken.
@ -174,8 +175,9 @@ failure call L<SSL_get_error(3)> to determine the correct course of action.
SSL_read_early_data() returns SSL_READ_EARLY_DATA_ERROR for failure,
SSL_READ_EARLY_DATA_SUCCESS for success with more data to read and
SSL_READ_EARLY_DATA_FINISH for no more to data be read. In the event of a
failure call L<SSL_get_error(3)> to determine the correct course of action.
SSL_READ_EARLY_DATA_FINISH for success with no more to data be read. In the
event of a failure call L<SSL_get_error(3)> to determine the correct course of
action.
SSL_get_max_early_data(), SSL_CTX_get_max_early_data() and
SSL_SESSION_get_max_early_data() return the maximum number of early data bytes