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crypto/tls: set Deadline before sending close notify alert

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This change also documents the need to set a Deadline before
calling Read or Write.

Fixes #31224

Change-Id: I89d6fe3ecb0a0076b4c61765f61c88056f951406
Reviewed-on: https://go-review.googlesource.com/c/go/+/266037
Trust: Katie Hockman <katie@golang.org>
Run-TryBot: Katie Hockman <katie@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
This commit is contained in:
Katie Hockman 2020-10-28 15:13:33 -04:00
parent f7ef5ca54a
commit c9b9cd73bb
2 changed files with 26 additions and 6 deletions
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10
doc/go1.16.html
View File

@ -237,12 +237,18 @@ Do not send CLs removing the interior tags from such phrases.
<p><!-- CL 256897 -->
I/O operations on closing or closed TLS connections can now be detected using
the new <a href="/pkg/net/#ErrClosed">ErrClosed</a> error. A typical use
would be <code>errors.Is(err, net.ErrClosed)</code>. In earlier releases
the new <a href="/pkg/net/#ErrClosed">ErrClosed</a> error. A typical use
would be <code>errors.Is(err, net.ErrClosed)</code>. In earlier releases
the only way to reliably detect this case was to match the string returned
by the <code>Error</code> method with <code>"tls: use of closed connection"</code>.
</p>
<p><!-- CL 266037 -->
A default deadline is set in <a href="/pkg/crypto/tls/#Conn.Close">Close</a>
before sending the close notify alert, in order to prevent blocking
indefinitely.
</p>
<h3 id="crypto/x509"><a href="/pkg/crypto/x509">crypto/x509</a></h3>
<p><!-- CL 235078 -->

22
src/crypto/tls/conn.go
View File

@ -1074,6 +1074,11 @@ var (
)
// Write writes data to the connection.
//
// As Write calls Handshake, in order to prevent indefinite blocking a deadline
// must be set for both Read and Write before Write is called when the handshake
// has not yet completed. See SetDeadline, SetReadDeadline, and
// SetWriteDeadline.
func (c *Conn) Write(b []byte) (int, error) {
// interlock with Close below
for {
@ -1232,8 +1237,12 @@ func (c *Conn) handleKeyUpdate(keyUpdate *keyUpdateMsg) error {
return nil
}
// Read can be made to time out and return a net.Error with Timeout() == true
// after a fixed time limit; see SetDeadline and SetReadDeadline.
// Read reads data from the connection.
//
// As Read calls Handshake, in order to prevent indefinite blocking a deadline
// must be set for both Read and Write before Read is called when the handshake
// has not yet completed. See SetDeadline, SetReadDeadline, and
// SetWriteDeadline.
func (c *Conn) Read(b []byte) (int, error) {
if err := c.Handshake(); err != nil {
return 0, err
@ -1301,9 +1310,10 @@ func (c *Conn) Close() error {
}
var alertErr error
if c.handshakeComplete() {
alertErr = c.closeNotify()
if err := c.closeNotify(); err != nil {
alertErr = fmt.Errorf("tls: failed to send closeNotify alert (but connection was closed anyway): %w", err)
}
}
if err := c.conn.Close(); err != nil {
@ -1330,8 +1340,12 @@ func (c *Conn) closeNotify() error {
defer c.out.Unlock()
if !c.closeNotifySent {
// Set a Write Deadline to prevent possibly blocking forever.
c.SetWriteDeadline(time.Now().Add(time.Second * 5))
c.closeNotifyErr = c.sendAlertLocked(alertCloseNotify)
c.closeNotifySent = true
// Any subsequent writes will fail.
c.SetWriteDeadline(time.Now())
}
return c.closeNotifyErr
}