.TH SECURITY-AUTH 2
.SH NAME
Auth: init, client, server \- authenticated connections between client and server
.SH SYNOPSIS
.EX
include "keyring.m";
include "security.m";
auth := load Auth Auth->PATH;

init:   fn(): string;
client: fn(alg: string, ai: ref Keyring->Authinfo,
            fd: ref Sys->FD): (ref Sys->FD, string);
server: fn(algs: list of string, ai: ref Keyring->Authinfo,
            fd: ref Sys->FD, setid: int): (ref Sys->FD, string);
.EE
.SH DESCRIPTION
.B Auth
establishes authenticated connections using the station to station protocol described
in
.IR auth (6).
It encapsulates the use of the primitives of
.IR keyring-auth (2)
and
.IR security-ssl (2)
for the particular case where the stations
play the rôles of `client' and `server'.
The underlying primitives must still be accessed directly in some cases,
for instance when completely symmetric authentication is needed between peers.
.PP
.B Init
must be called before using any other functions in
.BR Auth ;
it returns nil if successful, and a diagnostic message otherwise.
.PP
.B Client
authenticates a connection with the server on
.I fd
using the authentication data in
.IR ai .
If successful, and
.I alg
is neither
.B nil
nor the value
.B
"none"\c
,
.B client
will set the connection to digest or encrypt the data,
using the
digest or encryption algorithm specified in
.IR alg .
It returns the file descriptor for the connection,
and a string with information about the connection.
If an authenticated connection cannot be established,
.B client
returns a nil file descriptor and an error message.
.PP
.B Server
authenticates a client connection
.IR fd ,
as described in
.IR keyring-auth (2),
using the server's authentication data in
.IR ai .
If successful, and the client requested the use of a digest or
encryption algorithm, and that algorithm is listed in
.IR algs ,
.B server
enables the security layer
.IR ssl (3)
using the selected algorithm.
Furthermore, if
.I setid
is non-zero, the current user name is set to the
newly authenticated name.
.B Server
returns a file descriptor for the connection,
and a string with information about the connection.
If an authenticated connection cannot be established,
or the client's chosen algorithm is not listed,
.B server
returns a nil file descriptor and an error message.
.PP
Any string acceptable to
.IR ssl (3),
including
.B
"clear"\c
, can be given as an
.I alg
to
.BR client ,
or listed in
.I algs
for
.BR server .
Furthermore, the special string
.B
"none"
tells both functions
that
.IR ssl (3)
should not be used at all on a connection.
.SH EXAMPLE
This selection from
.B /appl/cmd/mount.b
illustrates client-side use.
.PP
.EX
	au := load Auth Auth->PATH;
	err := au->init();
	if(err != nil){
		sys->fprint(stderr, "mount: %s\en", err);
		exit;
	}
	fd: ref Sys->FD;
	(fd, err) = au->client("none", ai, c.dfd);
	if(fd == nil){
		sys->fprint(stderr, "mount: authentication failed: %s\en", err);
		exit;
	}
	dir := hd argv;
	ok = sys->mount(fd, dir, flags, "");
	if(ok < 0)
		sys->fprint(stderr, "mount: %r\en");
.EE
.PP
The following example from
.B /appl/lib/styxd.b
shows server-side use;
note that
.B readauthinfo
is called first to fetch the authentication data to pass to
.BR server .
.PP
.EX
	kr := load Keyring Keyring->PATH;
	...
	ai := kr->readauthinfo("/usr/"+user+"/keyring/default");
	auth->init();
	(fd, info_or_err) := auth->server(argv, ai, stdin, 1);
	if(fd == nil){
		sys->fprint(stderr, "styxd: %s\en", info_or_err);
		exit;
	}
	sys->pctl(Sys->FORKNS, nil);
	if(sys->export(fd, Sys->EXPASYNC) < 0)
		sys->fprint(stderr, "styxd: file export: %r\en");
.EE
.SH SOURCE
.B /appl/lib/auth.b
.SH "SEE ALSO"
.IR keyring-auth (2),
.IR security-ssl (2),
.IR ssl (3),
.IR auth (6)
