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.TH TLS 3 

.SH NAME

tls \- TLS1 and SSL3 record layer

.SH SYNOPSIS

.nf

.B bind -a #a /net

.B /net/tls/clone

.B /net/tls/encalgs

.B /net/tls/hashalgs

.BI /net/tls/ n 

.BI /net/tls/ n /ctl

.BI /net/tls/ n /data

.BI /net/tls/ n /hand

.BI /net/tls/ n /stats

.BI /net/tls/ n /status

.fi

.SH DESCRIPTION

The TLS device implements the record layer protocols

of Transport Layer Security version 1.0 and Secure Sockets Layer version 3.0.

It does not implement the handshake protocols, which are responsible for

mutual authentication and key exchange.

The

.I tls

device can be thought of as filters providing optional encryption and anti-tampering.

.PP

The top level directory contains a

.B clone

file and subdirectories numbered from zero through at least the last active filter.

Opening the

.B clone

file reserves a filter.

The file descriptor returned from the

.IR open (2)

will point to the control file,

.BR ctl ,

of the newly allocated filter.

Reading the

.B ctl

file returns a text string containing the number of the filter directory.

.PP

The filter initially cannot be used to pass messages

and will not encrypt or digest messages.

It is configured and controlled by writing commands to

.BR ctl .

.PP

The following commands are supported:

.TP

.BI fd \ open-fd\ vers

Pass record messages over the communications channel

.IR open-fd .

Initially, outgoing messages use version

.I vers

format records, but incoming messages of either version are accepted.

Valid versions are

.B 0x300

for SSLv3.0 and

.B 0x301

for TLSv1.0 (which could be known as SSLv3.01.)

This command must be issued before any other command

and before reading or writing any messages;

it may only be executed once.

.TP

.BI version \ vers

Use

.I vers

format records for all future records,

both outgoing and incoming.

This command may only be executed once.

.TP

.BI secret \ hashalg\ encalg\ isclient\ secretdata

Set up the digesting and encryption algorithms and secrets.

.I Hashalg

and

.I encalg

must be algorithm names returned by the corresponding files.

.I Secretdata

is the base-64 encoded (see

.IR encode (2))

secret data used for the algorithms.

It must contain at least enough data to populate the

secrets for digesting and encrypting.

These secrets are divided into three categories: digest secrets, keys, and initialization vectors.

The secrets are packed in this order, with no extra padding.

Within each category, the secret for data traveling from the client to the server comes first.

The incoming and outgoing secrets are automatically selected by devtls based on the

.I isclient

argument, which must be non-zero for the client of the TLS handshake,

and zero for the server.

.br

This command must be issued after

.BR version ,

and may be issued more than once.

At least one new

.I secret

command must be issued before each

.I changecipher

command; similarly, at least one new

.I secret command

must precede each incoming changecipher message.

.TP

.BI changecipher

Enable outgoing encryption and digesting as configured by the previous

.I secret

command.

This command sends a

.I changecipher

message.

.TP

.BI opened

Enable data messages.

This command may be issued any number of times,

although only the first is significant.

It must follow at least one successful

.I changecipher

command.

.TP

.BI alert \ alertno

Send an alert message.

.I Alertno

may be a valid alert code for either SSLv3.0 or TLSv1.0,

and is mapped to an appropriate code for the protocol in use.

If it is a fatal alert, the filter is set into an error state.

.PP

Application messages and handshake messages are communicated using

.I data

and

.IR hand ,

respectively.

Only one

.IR open (2)

of

.I hand

is allowed at a time.

.PP

Any record layer headers and trailers are inserted and

stripped automatically, and are not visible from the outside.

The device tries to synchronize record boundaries with reads and writes.

Each read will return data from exactly one record,

and will return all of the data from the record as long as

the buffer is big enough.

Each write will be converted into an integral number of records,

with all but potentially the last being maximal size.

The maximum record length supported is 16384 bytes.

This behavior is not specified in the protocols,

and may not be followed by other implementations.

.PP

If a fatal alert message is received, or a fatal

.I alert

command issued, the filter is set into an error state.

All further correspondence is halted,

although some pending operations may not be terminated.

Operations on

.I data

will fail with a

.BR "'tls error'" ,

and operations on

.I hand

will fail with a textual decoding of the alert.

The current non-fatal alert messages are

.BR "'close notify'" ,

.BR "'no renegotiation'" ,

and

.B "'handshake canceled by user'"

(sic).

Receipt of one of these alerts cause the next read on

.I hand

to terminate with an error.

If the alert is

.BR "'close notify'" ,

all future reads will terminate with a

.B "tls hungup"

error.

A

.B "'close notify'"

.I alert

command will terminate all future writes or reads from

.I data

with a

.B "'tls hungup'"

error.

.PP

If an error is encountered while reading or writing

the underlying communications channel, the error is returned

to the offending operation.

If the error is not

.BR "'interrupted'" ,

the filter is set into the error state.

In this case, all future operations on

.I hand

will fail with a

.BR "'channel error'" .

.PP

When all file descriptors for a filter have been closed,

the session is terminated and the filter reclaimed for future use.

A

.B "'close notify'"

alert will be sent on the underlying communications channel

unless one has already been sent or the filter is in the error state.

.PP

Reading

.I stats

or

.I status

returns information about the filter.

Each datum is returned on a single line of the form

.IB tag ": " data .

.I Stats

returns the number of bytes communicated by the

.B data

and

.B hand

channels.

The four lines returned are tagged by, in order,

.BR DataIn ,

.BR DataOut ,

.BR HandIn ,

and

.BR HandOut .

.I Status

returns lines following tags:

.BR State ,

.BR Version ,

.BR EncIn ,

.BR HashIn ,

.BR NewEncIn ,

.BR NewHashIn ,

.BR EncOut ,

.BR HashOut ,

.BR NewEncOut ,

and

.BR NewHashOut .

.BR State 's

value is a string describing the status of the connection,

and is one of the following:

.BR 'Handshaking' ,

.BR 'Established' ,

.BR 'RemoteClosed' ,

.BR 'LocalClosed' ,

.BR 'Alerting' ,

.BR 'Errored' ,

or

.BR 'Closed' .

.BR Version 's

give the hexadecimal record layer version in use.

The

.B Enc

and

.B Hash

fields return name of the current algorithms in use

or ready to be used, if any.

.PP

Reading

.I encalgs

and 

.I hashalgs

will give the space-separated list of algorithms implemented.

This will always include

.BR clear ,

meaning no encryption or digesting.

Currently implemented encryption algorithms are

.BR 'rc4_128' ,

.BR '3des_ede_cbc' ,

.B 'aes_128_cbc'

and

.BR 'aes_256_cbc' .

Currently implemented hashing algorithms are

.B 'md5'

and

.BR 'sha1' .

.SH "SEE ALSO"

.IR listen (8),

.IR dial (2),

.IR pushtls (2)

.SH SOURCE

.B /sys/src/9/port/devtls.c