krb_sendauth, krb_recvauth, krb_net_write, krb_net_read -
Kerberos routines for sending authentication via network
stream sockets
#include <krb.h>
#include <des.h>
#include <netinet/in.h>
int krb_sendauth(options, fd, ktext, service, inst, realm,
checksum, msg_data, cred, schedule, laddr,
faddr, version)
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;
int krb_recvauth(options, fd, ktext, service, inst, faddr,
laddr, auth_data, filename, schedule, version)
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;
int krb_net_write(fd, buf, len)
int fd;
char *buf;
int len;
int krb_net_read(fd, buf, len)
int fd;
char *buf;
int len;
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 krb_sendauth
function sends an authenticated ticket from the client
program to the server program by writing the ticket to a
network socket. The krb_recvauth function receives the
ticket from the client by reading from a network socket.
This function writes the ticket to the network socket
specified by the file descriptor fd, returning KSUCCESS if
the write proceeds successfully, and an error code if it
does not.
The ktext argument should point to an allocated KTEXT_ST
structure. The service, inst, and 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 realm argument to
NULL.
The 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
version string can be up to KSEND_VNO_LEN (see <krb.h>)
characters in length.
The 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
krb_sendauth passes it over the network in encrypted form.
The checksum argument is passed as the checksum argument
to krb_mk_req.
You can set 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.
KRB_SENDAUTH AND MUTUAL AUTHENTICATION [Toc] [Back] If you want mutual authentication, make sure that you read
all pending data from the local socket before calling
krb_sendauth. Set krb_sendauth's options argument to
KOPT_DO_MUTUAL (this macro is defined in the krb.h file);
make sure that the laddr argument points to the address of
the local socket, and that faddr points to the foreign
socket's network address.
Krb_sendauth fills in the other arguments-- msg_data,
cred, and schedule--before sending the ticket to the
server program. You must, however, allocate space for
these arguments before calling the function.
Krb_sendauth supports two other options: KOPT_DONT_MK_REQ,
and KOPT_DONT_CANON. If called with options set as
KOPT_DONT_MK_REQ, krb_sendauth will not use the krb_mk_req
function to retrieve the ticket from the Kerberos server.
The ktext argument must point to an existing ticket and
authenticator (such as would be created by krb_mk_req),
and the service, inst, and realm arguments can be set to
NULL.
If called with options set as KOPT_DONT_CANON,
krb_sendauth will not convert the service's instance to
canonical form using krb_get_phost(3).
If you want to call krb_sendauth with a multiple options
specification, construct options as a bitwise-OR of the
options you want to specify.
The krb_recvauth function reads a ticket/authenticator
pair from the socket pointed to by the fd argument. Set
the options argument as a bitwise-OR of the options
desired. Currently only KOPT_DO_MUTUAL is useful to the
receiver.
The ktext argument should point to an allocated KTEXT_ST
structure. Krb_recvauth fills ktext with the
ticket/authenticator pair read from fd, then passes it to
krb_rd_req.
The service and inst arguments specify the expected service
and instance for which the ticket was generated.
They are also passed to krb_rd_req. The inst argument may
be set to "*" if the caller wishes krb_mk_req to fill in
the instance used (note that there must be space in the
inst argument to hold a full instance name, see
krb_mk_req(3)).
The faddr argument should point to the address of the peer
which is presenting the ticket. It is also passed to
krb_rd_req.
If the client and server plan to mutually authenticate one
another, the laddr argument should point to the local
address of the file descriptor. Otherwise you can set
this argument to NULL.
The auth_data argument should point to an allocated
AUTH_DAT area. It is passed to and filled in by
krb_rd_req. The checksum passed to the corresponding
krb_sendauth is available as part of the filled-in
AUTH_DAT area.
The filename argument specifies the filename which the
service program should use to obtain its service key.
Krb_recvauth passes filename to the krb_rd_req function.
If you set this argument to "", krb_rd_req looks for the
service key in the file /etc/srvtab.
If the client and server are performing mutual authenication,
the schedule argument should point to an allocated
Key_schedule. Otherwise it is ignored and may be NULL.
The 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 krb_sendauth.
KRB_NET_WRITE AND KRB_NET_READ [Toc] [Back] The krb_net_write function emulates the write(2) system
call, but guarantees that all data specified is written to
fd before returning, unless an error condition occurs.
The krb_net_read function emulates the read(2) system
call, but guarantees that the requested amount of data is
read from fd before returning, unless an error condition
occurs.
krb_sendauth, krb_recvauth, krb_net_write, and
krb_net_read will not work properly on sockets set to nonblocking
I/O mode.
krb_mk_req(3), krb_rd_req(3), krb_get_phost(3)
John T. Kohl, MIT Project Athena
Copyright 1988, Massachusetts Instititute of Technology.
For copying and distribution information, please see the
file <mit-copyright.h>.
MIT Project Athena Kerberos Version 4.0 KRB_SENDAUTH(3)
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