krb_sendauth(3N)

NAME | SYNOPSIS | DESCRIPTION | ATTRIBUTES | SEE ALSO | NOTES | BUGS | AUTHOR | RESTRICTIONS

NAME

krb_sendauth, krb_recvauth, krb_net_write, krb_net_read- Kerberos routines for sending authentication via network stream sockets

SYNOPSIS

cc [ flag ... ] file ... -lkrb [ library ... ]
#include <kerberos/krb.h>
#include <netinet/in.h>

int krb_sendauth(const long options, const int fd, KTEXT ktext, const char *service, const char *inst, const char *realm, const ulong_t checksum, MSG_DAT *msg_data, CREDENTIALS *cred, Key_schedule schedule, const struct sockaddr_in *laddr, const struct sockaddr_in *faddr, const char *version);
int krb_recvauth(const long options, const int fd, KTEXT ktext, const char *service, char *inst, const struct sockaddr_in *faddr, const struct sockaddr_in *laddr, AUTH_DAT *auth_data, const char *filename, Key_schedule schedule, char *version);
int krb_net_write(const int fd, const char *buf, const int len);
int krb_net_read(const int fd, char *buf, const int len);

DESCRIPTION

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.

krb_sendauth()

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 <kerberos/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() (see kerberos(3N)).

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

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 <kerberos/krb.h>); 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() (see kerberos(3N)) 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() (see krb_realmofhost(3N)).

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.

krb_recvauth()

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() (see kerberos(3N)).

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() (see kerberos(3N)). The inst argument may be set to "*" if the caller wishes krb_mk_req() (see kerberos(3N)) 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() on kerberos(3N)).

The faddr argument should point to the address of the peer which is presenting the ticket. It is also passed to krb_rd_req() (see kerberos(3N)).

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() (see kerberos(3N)). 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, see kerberos(3N), 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 authentication, 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()

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.

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
MT-Level	Unsafe

SEE ALSO

read(2), write(2), kerberos(3N), kerberos_rpc(3N), krb_realmofhost(3N), attributes (5)

NOTES

These interfaces are unsafe in multithreaded applications. Unsafe interfaces should be called only from the main thread.

BUGS

krb_sendauth(), krb_recvauth(), krb_net_write(), and krb_net_read() will not work properly on sockets set to non-blocking I/O mode.

AUTHOR

John T. Kohl, MIT Project Athena

RESTRICTIONS

Copyright 1988, Massachusetts Institute of Technology. For copying and distribution information, please see the header <kerberos/mit-copyright.h>.

SunOS 5.7  Last Revised 30 Dec 1996

NAME | SYNOPSIS | DESCRIPTION | ATTRIBUTES | SEE ALSO | NOTES | BUGS | AUTHOR | RESTRICTIONS