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463 lines
12 KiB
Groff
463 lines
12 KiB
Groff
.\" $Source: /usr/src/kerberosIV/man/RCS/krb.3,v $
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.\" $Author: bostic $
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.\" $Header: /usr/src/kerberosIV/man/RCS/krb.3,v 4.11 1994/04/19 14:16:56 bostic Exp $
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.\" Copyright 1989 by the Massachusetts Institute of Technology.
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.\"
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.\" For copying and distribution information,
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.\" please see the file <mit-copyright.h>.
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.\"
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.TH KERBEROS 3 "Kerberos Version 4.0" "MIT Project Athena"
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.SH NAME
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krb_mk_req, krb_rd_req, krb_kntoln, krb_set_key, krb_get_cred,
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krb_mk_priv, krb_rd_priv, krb_mk_safe, krb_rd_safe, krb_mk_err,
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krb_rd_err, krb_ck_repl \- Kerberos authentication library
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.SH SYNOPSIS
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.nf
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.nj
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.ft B
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#include <kerberosIV/des.h>
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#include <kerberosIV/krb.h>
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.PP
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.ft B
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extern char *krb_err_txt[];
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.PP
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.ft B
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int krb_mk_req(authent,service,instance,realm,checksum)
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KTEXT authent;
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char *service;
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char *instance;
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char *realm;
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u_long checksum;
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.PP
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.ft B
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int krb_rd_req(authent,service,instance,from_addr,ad,fn)
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KTEXT authent;
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char *service;
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char *instance;
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u_long from_addr;
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AUTH_DAT *ad;
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char *fn;
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.PP
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.ft B
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int krb_kntoln(ad,lname)
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AUTH_DAT *ad;
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char *lname;
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.PP
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.ft B
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int krb_set_key(key,cvt)
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char *key;
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int cvt;
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.PP
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.ft B
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int krb_get_cred(service,instance,realm,c)
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char *service;
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char *instance;
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char *realm;
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CREDENTIALS *c;
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.PP
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.ft B
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long krb_mk_priv(in,out,in_length,schedule,key,sender,receiver)
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u_char *in;
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u_char *out;
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u_long in_length;
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des_cblock key;
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des_key_schedule schedule;
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struct sockaddr_in *sender;
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struct sockaddr_in *receiver;
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.PP
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.ft B
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long krb_rd_priv(in,in_length,schedule,key,sender,receiver,msg_data)
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u_char *in;
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u_long in_length;
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Key_schedule schedule;
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des_cblock key;
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struct sockaddr_in *sender;
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struct sockaddr_in *receiver;
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MSG_DAT *msg_data;
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.PP
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.ft B
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long krb_mk_safe(in,out,in_length,key,sender,receiver)
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u_char *in;
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u_char *out;
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u_long in_length;
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des_cblock key;
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struct sockaddr_in *sender;
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struct sockaddr_in *receiver;
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.PP
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.ft B
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long krb_rd_safe(in,length,key,sender,receiver,msg_data)
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u_char *in;
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u_long length;
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des_cblock key;
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struct sockaddr_in *sender;
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struct sockaddr_in *receiver;
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MSG_DAT *msg_data;
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.PP
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.ft B
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long krb_mk_err(out,code,string)
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u_char *out;
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long code;
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char *string;
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.PP
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.ft B
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long krb_rd_err(in,length,code,msg_data)
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u_char *in;
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u_long length;
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long code;
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MSG_DAT *msg_data;
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.fi
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.ft R
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.SH DESCRIPTION
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This library supports network authentication and various related
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operations. The library contains many routines beyond those described
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in this man page, but they are not intended to be used directly.
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Instead, they are called by the routines that are described, the
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authentication server and the login program.
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.PP
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.I krb_err_txt[]
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contains text string descriptions of various Kerberos error codes returned
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by some of the routines below.
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.PP
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.I krb_mk_req
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takes a pointer to a text structure in which an authenticator is to be
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built. It also takes the name, instance, and realm of the service to be
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used and an optional checksum. It is up to the application to decide
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how to generate the checksum.
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.I krb_mk_req
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then retrieves a ticket for the desired service and creates an
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authenticator. The authenticator is built in
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.I authent
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and is accessible
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to the calling procedure.
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.PP
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It is up to the application to get the authenticator to the service
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where it will be read by
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.I krb_rd_req.
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Unless an attacker possesses the session key contained in the ticket, it
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will be unable to modify the authenticator. Thus, the checksum can be
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used to verify the authenticity of the other data that will pass through
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a connection.
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.PP
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.I krb_rd_req
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takes an authenticator of type
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.B KTEXT,
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a service name, an instance, the address of the
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host originating the request, and a pointer to a structure of type
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.B AUTH_DAT
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which is filled in with information obtained from the authenticator.
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It also optionally takes the name of the file in which it will find the
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secret key(s) for the service.
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If the supplied
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.I instance
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contains "*", then the first service key with the same service name
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found in the service key file will be used, and the
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.I instance
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argument will be filled in with the chosen instance. This means that
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the caller must provide space for such an instance name.
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.PP
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It is used to find out information about the principal when a request
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has been made to a service. It is up to the application protocol to get
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the authenticator from the client to the service. The authenticator is
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then passed to
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.I krb_rd_req
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to extract the desired information.
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.PP
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.I krb_rd_req
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returns zero (RD_AP_OK) upon successful authentication. If a packet was
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forged, modified, or replayed, authentication will fail. If the
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authentication fails, a non-zero value is returned indicating the
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particular problem encountered. See
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.I krb.h
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for the list of error codes.
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.PP
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If the last argument is the null string (""), krb_rd_req will use the
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file /etc/srvtab to find its keys. If the last argument is NULL, it
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will assume that the key has been set by
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.I krb_set_key
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and will not bother looking further.
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.PP
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.I krb_kntoln
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converts a Kerberos name to a local name. It takes a structure
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of type AUTH_DAT and uses the name and instance to look in the database
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/etc/aname to find the corresponding local name. The local name is
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returned and can be used by an application to change uids, directories,
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or other parameters. It is not an integral part of Kerberos, but is
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instead provided to support the use of Kerberos in existing utilities.
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.PP
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.I krb_set_key
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takes as an argument a des key. It then creates
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a key schedule from it and saves the original key to be used as an
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initialization vector.
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It is used to set the server's key which
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must be used to decrypt tickets.
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.PP
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If called with a non-zero second argument,
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.I krb_set_key
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will first convert the input from a string of arbitrary length to a DES
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key by encrypting it with a one-way function.
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.PP
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In most cases it should not be necessary to call
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.I krb_set_key.
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The necessary keys will usually be obtained and set inside
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.I krb_rd_req. krb_set_key
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is provided for those applications that do not wish to place the
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application keys on disk.
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.PP
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.I krb_get_cred
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searches the caller's ticket file for a ticket for the given service, instance,
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and realm; and, if a ticket is found, fills in the given CREDENTIALS structure
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with the ticket information.
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.PP
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If the ticket was found,
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.I krb_get_cred
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returns GC_OK.
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If the ticket file can't be found, can't be read, doesn't belong to
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the user (other than root), isn't a regular file, or is in the wrong
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mode, the error GC_TKFIL is returned.
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.PP
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.I krb_mk_priv
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creates an encrypted, authenticated
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message from any arbitrary application data, pointed to by
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.I in
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and
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.I in_length
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bytes long.
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The private session key, pointed to by
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.I key
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and the key schedule,
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.I schedule,
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are used to encrypt the data and some header information using
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.I pcbc_encrypt.
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.I sender
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and
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.I receiver
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point to the Internet address of the two parties.
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In addition to providing privacy, this protocol message protects
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against modifications, insertions or replays. The encapsulated message and
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header are placed in the area pointed to by
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.I out
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and the routine returns the length of the output, or -1 indicating
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an error.
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.PP
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.I krb_rd_priv
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decrypts and authenticates a received
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.I krb_mk_priv
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message.
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.I in
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points to the beginning of the received message, whose length
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is specified in
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.I in_length.
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The private session key, pointed to by
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.I key,
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and the key schedule,
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.I schedule,
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are used to decrypt and verify the received message.
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.I msg_data
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is a pointer to a
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.I MSG_DAT
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struct, defined in
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.I krb.h.
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The routine fills in the
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.I app_data
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field with a pointer to the decrypted application data,
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.I app_length
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with the length of the
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.I app_data
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field,
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.I time_sec
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and
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.I time_5ms
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with the timestamps in the message, and
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.I swap
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with a 1 if the byte order of the receiver is different than that of
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the sender. (The application must still determine if it is appropriate
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to byte-swap application data; the Kerberos protocol fields are already taken
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care of). The
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.I hash
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field returns a value useful as input to the
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.I krb_ck_repl
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routine.
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The routine returns zero if ok, or a Kerberos error code. Modified messages
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and old messages cause errors, but it is up to the caller to
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check the time sequence of messages, and to check against recently replayed
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messages using
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.I krb_ck_repl
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if so desired.
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.PP
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.I krb_mk_safe
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creates an authenticated, but unencrypted message from any arbitrary
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application data,
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pointed to by
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.I in
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and
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.I in_length
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bytes long.
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The private session key, pointed to by
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.I key,
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is used to seed the
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.I quad_cksum()
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checksum algorithm used as part of the authentication.
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.I sender
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and
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.I receiver
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point to the Internet address of the two parties.
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This message does not provide privacy, but does protect (via detection)
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against modifications, insertions or replays. The encapsulated message and
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header are placed in the area pointed to by
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.I out
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and the routine returns the length of the output, or -1 indicating
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an error.
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The authentication provided by this routine is not as strong as that
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provided by
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.I krb_mk_priv
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or by computing the checksum using
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.I cbc_cksum
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instead, both of which authenticate via DES.
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.PP
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.I krb_rd_safe
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authenticates a received
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.I krb_mk_safe
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message.
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.I in
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points to the beginning of the received message, whose length
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is specified in
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.I in_length.
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The private session key, pointed to by
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.I key,
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is used to seed the quad_cksum() routine as part of the authentication.
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.I msg_data
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is a pointer to a
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.I MSG_DAT
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struct, defined in
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.I krb.h .
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The routine fills in these
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.I MSG_DAT
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fields:
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the
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.I app_data
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field with a pointer to the application data,
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.I app_length
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with the length of the
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.I app_data
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field,
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.I time_sec
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and
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.I time_5ms
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with the timestamps in the message, and
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.I swap
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with a 1 if the byte order of the receiver is different than that of
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the sender.
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(The application must still determine if it is appropriate
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to byte-swap application data; the Kerberos protocol fields are already taken
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care of). The
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.I hash
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field returns a value useful as input to the
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.I krb_ck_repl
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routine.
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The routine returns zero if ok, or a Kerberos error code. Modified messages
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and old messages cause errors, but it is up to the caller to
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check the time sequence of messages, and to check against recently replayed
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messages using
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.I krb_ck_repl
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if so desired.
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.PP
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.I krb_mk_err
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constructs an application level error message that may be used along
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with
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.I krb_mk_priv
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or
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.I krb_mk_safe.
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.I out
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is a pointer to the output buffer,
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.I code
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is an application specific error code, and
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.I string
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is an application specific error string.
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.PP
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.I krb_rd_err
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unpacks a received
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.I krb_mk_err
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message.
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.I in
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points to the beginning of the received message, whose length
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is specified in
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.I in_length.
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.I code
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is a pointer to a value to be filled in with the error
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value provided by the application.
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.I msg_data
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is a pointer to a
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.I MSG_DAT
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struct, defined in
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.I krb.h .
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The routine fills in these
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.I MSG_DAT
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fields: the
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.I app_data
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field with a pointer to the application error text,
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.I app_length
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with the length of the
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.I app_data
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field, and
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.I swap
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with a 1 if the byte order of the receiver is different than that of
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the sender. (The application must still determine if it is appropriate
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to byte-swap application data; the Kerberos protocol fields are already taken
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care of).
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The routine returns zero if the error message has been successfully received,
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or a Kerberos error code.
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.PP
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The
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.I KTEXT
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structure is used to pass around text of varying lengths. It consists
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of a buffer for the data, and a length. krb_rd_req takes an argument of this
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type containing the authenticator, and krb_mk_req returns the
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authenticator in a structure of this type. KTEXT itself is really a
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pointer to the structure. The actual structure is of type KTEXT_ST.
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.PP
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The
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.I AUTH_DAT
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structure is filled in by krb_rd_req. It must be allocated before
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calling krb_rd_req, and a pointer to it is passed. The structure is
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filled in with data obtained from Kerberos.
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.I MSG_DAT
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structure is filled in by either krb_rd_priv, krb_rd_safe, or
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krb_rd_err. It must be allocated before the call and a pointer to it
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is passed. The structure is
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filled in with data obtained from Kerberos.
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.PP
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.SH FILES
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/usr/include/kerberosIV/krb.h
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.br
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/usr/lib/libkrb.a
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.br
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/usr/include/kerberosIV/des.h
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.br
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/usr/lib/libdes.a
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.br
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/etc/kerberosIV/aname
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.br
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/etc/kerberosIV/srvtab
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.br
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/tmp/tkt[uid]
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.SH "SEE ALSO"
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kerberos(1), des_crypt(3)
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.SH DIAGNOSTICS
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.SH BUGS
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The caller of
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.I krb_rd_req, krb_rd_priv, and krb_rd_safe
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must check time order and for replay attempts.
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.I krb_ck_repl
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is not implemented yet.
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.SH AUTHORS
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Clifford Neuman, MIT Project Athena
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.br
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Steve Miller, MIT Project Athena/Digital Equipment Corporation
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.SH RESTRICTIONS
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COPYRIGHT 1985,1986,1989 Massachusetts Institute of Technology
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