.\" $OpenBSD: tls_init.3,v 1.6 2015/01/01 13:30:52 schwarze Exp $
.\"
.\" Copyright (c) 2014 Ted Unangst <tedu@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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.Dd $Mdocdate: January 1 2015 $
.Dt TLS 3
.Os
.Sh NAME
.Nm tls_init ,
.Nm tls_error ,
.Nm tls_config_new ,
.Nm tls_config_free ,
.Nm tls_config_set_ca_file ,
.Nm tls_config_set_ca_path ,
.Nm tls_config_set_cert_file ,
.Nm tls_config_set_cert_mem ,
.Nm tls_config_set_ciphers ,
.Nm tls_config_set_ecdhcurve ,
.Nm tls_config_set_key_file ,
.Nm tls_config_set_key_mem ,
.Nm tls_config_set_protocols ,
.Nm tls_config_set_verify_depth ,
.Nm tls_config_clear_keys ,
.Nm tls_config_insecure_noverifyhost ,
.Nm tls_config_insecure_noverifycert ,
.Nm tls_config_verify ,
.Nm tls_client ,
.Nm tls_server ,
.Nm tls_configure ,
.Nm tls_reset ,
.Nm tls_close ,
.Nm tls_free ,
.Nm tls_connect ,
.Nm tls_connect_fds ,
.Nm tls_connect_socket ,
.Nm tls_read ,
.Nm tls_write ,
.Nd TLS client and server API
.Sh SYNOPSIS
.In tls.h
.Ft "int"
.Fn tls_init "void"
.Ft "const char *"
.Fn tls_error "struct tls *ctx"
.Ft "struct tls_config *"
.Fn tls_config_new "void"
.Ft "void"
.Fn tls_config_free "struct tls_config *config"
.Ft "int"
.Fn tls_config_set_ca_file "struct tls_config *config" "const char *ca_file"
.Ft "int"
.Fn tls_config_set_ca_path "struct tls_config *config" "const char *ca_path"
.Ft "int"
.Fn tls_config_set_cert_file "struct tls_config *config" "const char *cert_file"
.Ft "int"
.Fn tls_config_set_cert_mem  "struct tls_config *config" "const uint8_t *cert" "size_t len"
.Ft "int"
.Fn tls_config_set_ciphers "struct tls_config *config" "const char *ciphers"
.Ft "int"
.Fn tls_config_set_ecdhcurve "struct tls_config *config" "const char *name"
.Ft "int"
.Fn tls_config_set_key_file "struct tls_config *config" "const char *key_file"
.Ft "int"
.Fn tls_config_set_key_mem "struct tls_config *config" "const uint8_t *key" "size_t len"
.Ft "int"
.Fn tls_config_set_protocols "struct tls_config *config" "uint32_t protocols"
.Ft "int"
.Fn tls_config_set_verify_depth "struct tls_config *config" "int verify_depth"
.Ft "void"
.Fn tls_config_clear_keys "struct tls_config *config"
.Ft "void"
.Fn tls_config_insecure_noverifyhost "struct tls_config *config"
.Ft "void"
.Fn tls_config_insecure_noverifycert "struct tls_config *config"
.Ft "void"
.Fn tls_config_verify "struct tls_config *config"
.Ft "struct tls *"
.Fn tls_client void
.Ft "struct tls *"
.Fn tls_server void
.Ft "int"
.Fn tls_configure "struct tls *ctx" "struct tls_config *config"
.Ft "void"
.Fn tls_reset "struct tls *ctx"
.Ft "int"
.Fn tls_close "struct tls *ctx"
.Ft "void"
.Fn tls_free "struct tls *ctx"
.Ft "int"
.Fn tls_connect "struct tls *ctx" "const char *host" "const char *port"
.Ft "int"
.Fn tls_connect_fds "struct tls *ctx" "int fd_read" "int fd_write" "const char *hostname"
.Ft "int"
.Fn tls_connect_socket "struct tls *ctx" "int s" "const char *hostname"
.Ft "int"
.Fn tls_read "struct tls *ctx" "void *buf" "size_t buflen" "size_t *outlen"
.Ft "int"
.Fn tls_write "struct tls *ctx" "const void *buf" "size_t buflen" "size_t *outlen"
.Sh DESCRIPTION
The
.Nm tls
family of functions establishes a secure communications channel
using the TLS socket protocol.
Both clients and servers are supported.
.Pp
The
.Fn tls_init
function should be called once before any function is used.
.Pp
Before a connection is created, a configuration must be created.
The
.Fn tls_config_new
function returns a new default configuration that can be used for future
connections.
Several functions exist to change the options of the configuration; see below.
.Pp
A
.Em tls
connection is represented as a
.Em context .
A new
.Em context
is created by either the
.Fn tls_client
or
.Fn tls_server
functions.
The context can then be configured with the function
.Fn tls_configure .
The same
.Em tls_config
object can be used to configure multiple contexts.
.Pp
A client connection is initiated after configuration by calling
.Fn tls_connect .
This function will create a new socket, connect to the specified host and
port, and then establish a secure connection.
An already existing socket can be upgraded to a secure connection by calling
.Fn tls_connect_socket .
Alternatively, a secure connection can be established over a pair of existing
file descriptors by calling
.Fn tls_connect_fds .
.Pp
Two functions are provided for input and output,
.Fn tls_read
and
.Fn tls_write .
.Pp
After use, a tls
.Em context
should be closed with
.Fn tls_close ,
and then freed by calling
.Fn tls_free .
When no more contexts are to be created, the
.Em tls_config
object should be freed by calling
.Fn tls_config_free .
.Sh FUNCTIONS
The
.Fn tls_init
function initializes global data structures.
It should be called once before any other functions.
.Pp
The following functions create and free configuration objects.
.Bl -bullet -offset four
.It
.Fn tls_config_new
allocates a new default configuration object.
.It
.Fn tls_config_free
frees a configuration object.
.El
.Pp
The following functions modify a configuration by setting parameters.
Configuration options may apply to only clients or only servers or both.
.Bl -bullet -offset four
.It
.Fn tls_config_set_ca_file
sets the filename used to load a file
containing the root certificates.
.Em (Client)
.It
.Fn tls_config_set_ca_path
sets the path (directory) which should be searched for root
certificates.
.Em (Client)
.It
.Fn tls_config_set_cert_file
sets file from which the public certificate will be read.
.Em (Client and server)
.It
.Fn tls_config_set_cert_mem
sets the public certificate directly from memory.
.Em (Client and server)
.It
.Fn tls_config_set_ciphers
sets the list of ciphers that may be used.
.Em (Client and server)
.It
.Fn tls_config_set_key_file
sets the file from which the private key will be read.
.Em (Server)
.It
.Fn tls_config_set_key_mem
directly sets the private key from memory.
.Em (Server)
.It
.Fn tls_config_set_protocols
sets which versions of the protocol may be used.
Possible values are the bitwise OR of:
.Pp
.Bl -tag -width "TLS_PROTOCOL_TLSv1_2" -offset indent -compact
.It Dv TLS_PROTOCOL_TLSv1_0
.It Dv TLS_PROTOCOL_TLSv1_1
.It Dv TLS_PROTOCOL_TLSv1_2
.El
.Pp
Additionally, the values
.Dv TLS_PROTOCOL_TLSv1
(all TLS versions) and
.Dv TLS_PROTOCOLS_DEFAULT
(currently all TLS versions) may be used.
.Em (Client and server)
.It
.Fn tls_config_clear_keys
clears any secret keys from memory.
.Em (Server)
.It
.Fn tls_config_insecure_noverifyhost
disables hostname verification.
Be careful when using this option.
.Em (Client)
.It
.Fn tls_config_insecure_noverifycert
disables certificate verification.
Be extremely careful when using this option.
.Em (Client)
.It
.Fn tls_config_verify
reenables hostname and certificate verification.
.Em (Client)
.El
.Pp
The following functions create, prepare, and free a connection context.
.Bl -bullet -offset four
.It
.Fn tls_client
creates a new tls context for client connections.
.It
.Fn tls_server
creates a new tls context for server connections.
.It
.Fn tls_configure
readies a tls context for use by applying the configuration
options.
.It
.Fn tls_close
closes a connection after use.
If the connection was established using
.Fn tls_connect_fds ,
only the TLS layer will be closed and it is the caller's responsibility to close
the file descriptors.
.It
.Fn tls_free
frees a tls context after use.
.El
.Pp
The following functions initiate a connection and perform input and output
operations.
.Bl -bullet -offset four
.It
.Fn tls_connect
connects a client context to the server named by
.Fa host .
The
.Fa port
may be numeric or a service name.
If it is NULL then a host of the format "hostname:port" is permitted.
.It
.Fn tls_connect_fds
connects a client context to a pair of existing file descriptors.
.It
.Fn tls_connect_socket
connects a client context to an already established socket connection.
.It
.Fn tls_read
reads
.Fa buflen
bytes of data from the socket into
.Fa buf .
The amount of data read is returned in
.Fa outlen .
.It
.Fn tls_write
writes
.Fa buflen
bytes of data from
.Fa buf
to the socket.
The amount of data written is returned in
.Fa outlen .
.El
.Sh RETURN VALUES
Functions that return
.Vt int
will return 0 on success and -1 on error.
Functions that return a pointer will return NULL on error.
.\" .Sh ERRORS
.\" .Sh SEE ALSO
.Sh HISTORY
The
.Nm tls
API first appeared in
.Ox 5.6
as a response to the unnecessary challenges other APIs present in
order to use them safely.