path: root/kerberosIV/krb/krb_sendauth.3

.\" Copyright 1988 by the Massachusetts Institute of Technology.
.\"
.\" For copying and distribution information,
.\" please see the file <mit-copyright.h>.
.\"
.\"	$OpenBSD: krb_sendauth.3,v 1.2 1997/05/30 03:11:29 gene Exp $
.TH KRB_SENDAUTH 3 "Kerberos Version 4.0" "MIT Project Athena"
.SH NAME
krb_sendauth, krb_recvauth, krb_net_write, krb_net_read \-
Kerberos routines for sending authentication via network stream sockets
.SH SYNOPSIS
.nf
.nj
.ft B
#include <kerberosIV/krb.h>
#include <kerberosIV/des.h>
#include <kerberosIV/netinet/in.h>
.PP
.fi
.HP 1i
.ft B
int krb_sendauth(options, fd, ktext, service, inst, realm, checksum,
msg_data, cred, schedule, laddr, faddr, version)
.nf
.RS 0
.ft B
long options;
int fd;
KTEXT ktext;
char *service, *inst, *realm;
u_long checksum;
MSG_DAT *msg_data;
CREDENTIALS *cred;
Key_schedule schedule;
struct sockaddr_in *laddr, *faddr;
char *version;
.PP
.fi
.HP 1i
.ft B
int krb_recvauth(options, fd, ktext, service, inst, faddr, laddr,
auth_data, filename, schedule, version)
.nf
.RS 0
.ft B
long options;
int fd;
KTEXT ktext;
char *service, *inst;
struct sockaddr_in *faddr, *laddr;
AUTH_DAT *auth_data;
char *filename;
Key_schedule schedule;
char *version;			
.PP
.ft B
int krb_net_write(fd, buf, len)
int fd;
char *buf;
int len;
.PP
.ft B
int krb_net_read(fd, buf, len)
int fd;
char *buf;
int len;
.fi
.SH DESCRIPTION
.PP
These functions,
which are built on top of the core Kerberos library,
provide a convenient means for client and server
programs to send authentication messages
to one another through network connections.
The
.I krb_sendauth
function sends an authenticated ticket from the client program to
the server program by writing the ticket to a network socket.
The
.I krb_recvauth
function receives the ticket from the client by
reading from a network socket.

.SH KRB_SENDAUTH
.PP
This function writes the ticket to
the network socket specified by the
file descriptor
.IR fd,
returning KSUCCESS if the write proceeds successfully,
and an error code if it does not.

The
.I ktext
argument should point to an allocated KTEXT_ST structure.
The
.IR service,
.IR inst,
and
.IR realm
arguments specify the server program's Kerberos principal name,
instance, and realm.
If you are writing a client that uses the local realm exclusively,
you can set the
.I realm
argument to NULL.

The
.I version
argument allows the client program to pass an application-specific
version string that the server program can then match against
its own version string.
The
.I version
string can be up to KSEND_VNO_LEN (see 
.IR <krb.h> )
characters in length.

The
.I checksum
argument can be used to pass checksum information to the
server program.
The client program is responsible for specifying this information.
This checksum information is difficult to corrupt because
.I krb_sendauth
passes it over the network in encrypted form.
The
.I checksum
argument is passed as the checksum argument to
.IR krb_mk_req .

You can set
.IR krb_sendauth's
other arguments to NULL unless you want the
client and server programs to mutually authenticate
themselves.
In the case of mutual authentication,
the client authenticates itself to the server program,
and demands that the server in turn authenticate itself to
the client.

.SH KRB_SENDAUTH AND MUTUAL AUTHENTICATION
.PP
If you want mutual authentication,
make sure that you read all pending data from the local socket
before calling
.IR krb_sendauth.
Set
.IR krb_sendauth's
.I options
argument to
.BR KOPT_DO_MUTUAL
(this macro is defined in the
.IR krb.h
file);
make sure that the
.I laddr
argument points to
the address of the local socket,
and that
.I faddr
points to the foreign socket's network address.

.I Krb_sendauth
fills in the other arguments--
.IR msg_data ,
.IR cred ,
and
.IR schedule --before
sending the ticket to the server program.
You must, however, allocate space for these arguments
before calling the function.

.I Krb_sendauth
supports two other options:
.BR KOPT_DONT_MK_REQ,
and
.BR KOPT_DONT_CANON.
If called with
.I options
set as KOPT_DONT_MK_REQ,
.I krb_sendauth
will not use the
.I krb_mk_req
function to retrieve the ticket from the Kerberos server.
The
.I ktext
argument must point to an existing ticket and authenticator (such as
would be created by 
.IR krb_mk_req ),
and the
.IR service,
.IR inst,
and
.IR realm
arguments can be set to NULL.

If called with
.I options
set as KOPT_DONT_CANON,
.I krb_sendauth
will not convert the service's instance to canonical form using 
.IR krb_get_phost (3).

If you want to call
.I krb_sendauth
with a multiple
.I options
specification,
construct
.I options
as a bitwise-OR of the options you want to specify.

.SH KRB_RECVAUTH
.PP
The
.I krb_recvauth
function
reads a ticket/authenticator pair from the socket pointed to by the
.I fd
argument.
Set the
.I options
argument
as a bitwise-OR of the options desired.
Currently only KOPT_DO_MUTUAL is useful to the receiver.

The
.I ktext
argument
should point to an allocated KTEXT_ST structure.
.I Krb_recvauth
fills
.I ktext
with the
ticket/authenticator pair read from
.IR fd ,
then passes it to
.IR krb_rd_req .

The
.I service
and
.I inst
arguments
specify the expected service and instance for which the ticket was
generated.  They are also passed to
.IR krb_rd_req.
The
.I inst
argument may be set to "*" if the caller wishes
.I krb_mk_req
to fill in the instance used (note that there must be space in the
.I inst
argument to hold a full instance name, see 
.IR krb_mk_req (3)).

The
.I faddr
argument
should point to the address of the peer which is presenting the ticket.
It is also passed to
.IR krb_rd_req .

If the client and server plan to mutually authenticate
one another,
the
.I laddr
argument
should point to the local address of the file descriptor.
Otherwise you can set this argument to NULL.

The
.I auth_data
argument
should point to an allocated AUTH_DAT area.
It is passed to and filled in by
.IR krb_rd_req .
The checksum passed to the corresponding
.I krb_sendauth
is available as part of the filled-in AUTH_DAT area.

The
.I filename
argument
specifies the filename
which the service program should use to obtain its service key.
.I Krb_recvauth
passes
.I filename
to the
.I krb_rd_req
function.
If you set this argument to "",
.I krb_rd_req
looks for the service key in the file
.IR /etc/srvtab.

If the client and server are performing mutual authenication,
the
.I schedule
argument
should point to an allocated Key_schedule.
Otherwise it is ignored and may be NULL.

The
.I version
argument should point to a character array of at least KSEND_VNO_LEN
characters.  It is filled in with the version string passed by the client to
.IR krb_sendauth.
.PP
.SH KRB_NET_WRITE AND KRB_NET_READ
.PP
The
.I krb_net_write
function
emulates the write(2) system call, but guarantees that all data
specified is written to
.I fd
before returning, unless an error condition occurs.
.PP
The
.I krb_net_read
function
emulates the read(2) system call, but guarantees that the requested
amount of data is read from
.I fd
before returning, unless an error condition occurs.
.PP
.SH BUGS
.IR krb_sendauth,
.IR krb_recvauth,
.IR krb_net_write,
and
.IR krb_net_read
will not work properly on sockets set to non-blocking I/O mode.

.SH SEE ALSO

krb_mk_req(3), krb_rd_req(3), krb_get_phost(3)

.SH AUTHOR
John T. Kohl, MIT Project Athena
.SH RESTRICTIONS
Copyright 1988, Massachusetts Instititute of Technology.
For copying and distribution information,
please see the file <mit-copyright.h>.