+.\" $Source: /usr/src/kerberosIV/man/RCS/kerberos.3,v $
+.\" $Author: kfall $
+.\" $Header: /usr/src/kerberosIV/man/RCS/kerberos.3,v 4.10 90/06/25 21:12:11 kfall Exp $
+.\" Copyright 1989 by the Massachusetts Institute of Technology.
+.\"
+.\" For copying and distribution information,
+.\" please see the file <mit-copyright.h>.
+.\"
+.TH KERBEROS 3 "Kerberos Version 4.0" "MIT Project Athena"
+.SH NAME
+krb_mk_req, krb_rd_req, krb_kntoln, krb_set_key, krb_get_cred,
+krb_mk_priv, krb_rd_priv, krb_mk_safe, krb_rd_safe, krb_mk_err,
+krb_rd_err, krb_ck_repl \- Kerberos authentication library
+.SH SYNOPSIS
+.nf
+.nj
+.ft B
+#include <kerberosIV/des.h>
+#include <kerberosIV/krb.h>
+.PP
+.ft B
+extern char *krb_err_txt[];
+.PP
+.ft B
+int krb_mk_req(authent,service,instance,realm,checksum)
+KTEXT authent;
+char *service;
+char *instance;
+char *realm;
+u_long checksum;
+.PP
+.ft B
+int krb_rd_req(authent,service,instance,from_addr,ad,fn)
+KTEXT authent;
+char *service;
+char *instance;
+u_long from_addr;
+AUTH_DAT *ad;
+char *fn;
+.PP
+.ft B
+int krb_kntoln(ad,lname)
+AUTH_DAT *ad;
+char *lname;
+.PP
+.ft B
+int krb_set_key(key,cvt)
+char *key;
+int cvt;
+.PP
+.ft B
+int krb_get_cred(service,instance,realm,c)
+char *service;
+char *instance;
+char *realm;
+CREDENTIALS *c;
+.PP
+.ft B
+long krb_mk_priv(in,out,in_length,schedule,key,sender,receiver)
+u_char *in;
+u_char *out;
+u_long in_length;
+des_cblock key;
+des_key_schedule schedule;
+struct sockaddr_in *sender;
+struct sockaddr_in *receiver;
+.PP
+.ft B
+long krb_rd_priv(in,in_length,schedule,key,sender,receiver,msg_data)
+u_char *in;
+u_long in_length;
+Key_schedule schedule;
+des_cblock key;
+struct sockaddr_in *sender;
+struct sockaddr_in *receiver;
+MSG_DAT *msg_data;
+.PP
+.ft B
+long krb_mk_safe(in,out,in_length,key,sender,receiver)
+u_char *in;
+u_char *out;
+u_long in_length;
+des_cblock key;
+struct sockaddr_in *sender;
+struct sockaddr_in *receiver;
+.PP
+.ft B
+long krb_rd_safe(in,length,key,sender,receiver,msg_data)
+u_char *in;
+u_long length;
+des_cblock key;
+struct sockaddr_in *sender;
+struct sockaddr_in *receiver;
+MSG_DAT *msg_data;
+.PP
+.ft B
+long krb_mk_err(out,code,string)
+u_char *out;
+long code;
+char *string;
+.PP
+.ft B
+long krb_rd_err(in,length,code,msg_data)
+u_char *in;
+u_long length;
+long code;
+MSG_DAT *msg_data;
+.fi
+.ft R
+.SH DESCRIPTION
+This library supports network authentication and various related
+operations. The library contains many routines beyond those described
+in this man page, but they are not intended to be used directly.
+Instead, they are called by the routines that are described, the
+authentication server and the login program.
+.PP
+.I krb_err_txt[]
+contains text string descriptions of various Kerberos error codes returned
+by some of the routines below.
+.PP
+.I krb_mk_req
+takes a pointer to a text structure in which an authenticator is to be
+built. It also takes the name, instance, and realm of the service to be
+used and an optional checksum. It is up to the application to decide
+how to generate the checksum.
+.I krb_mk_req
+then retrieves a ticket for the desired service and creates an
+authenticator. The authenticator is built in
+.I authent
+and is accessible
+to the calling procedure.
+.PP
+It is up to the application to get the authenticator to the service
+where it will be read by
+.I krb_rd_req.
+Unless an attacker posesses the session key contained in the ticket, it
+will be unable to modify the authenticator. Thus, the checksum can be
+used to verify the authenticity of the other data that will pass through
+a connection.
+.PP
+.I krb_rd_req
+takes an authenticator of type
+.B KTEXT,
+a service name, an instance, the address of the
+host originating the request, and a pointer to a structure of type
+.B AUTH_DAT
+which is filled in with information obtained from the authenticator.
+It also optionally takes the name of the file in which it will find the
+secret key(s) for the service.
+If the supplied
+.I instance
+contains "*", then the first service key with the same service name
+found in the service key file will be used, and the
+.I instance
+argument will be filled in with the chosen instance. This means that
+the caller must provide space for such an instance name.
+.PP
+It is used to find out information about the principal when a request
+has been made to a service. It is up to the application protocol to get
+the authenticator from the client to the service. The authenticator is
+then passed to
+.I krb_rd_req
+to extract the desired information.
+.PP
+.I krb_rd_req
+returns zero (RD_AP_OK) upon successful authentication. If a packet was
+forged, modified, or replayed, authentication will fail. If the
+authentication fails, a non-zero value is returned indicating the
+particular problem encountered. See
+.I krb.h
+for the list of error codes.
+.PP
+If the last argument is the null string (""), krb_rd_req will use the
+file /etc/srvtab to find its keys. If the last argument is NULL, it
+will assume that the key has been set by
+.I krb_set_key
+and will not bother looking further.
+.PP
+.I krb_kntoln
+converts a Kerberos name to a local name. It takes a structure
+of type AUTH_DAT and uses the name and instance to look in the database
+/etc/aname to find the corresponding local name. The local name is
+returned and can be used by an application to change uids, directories,
+or other parameters. It is not an integral part of Kerberos, but is
+instead provided to support the use of Kerberos in existing utilities.
+.PP
+.I krb_set_key
+takes as an argument a des key. It then creates
+a key schedule from it and saves the original key to be used as an
+initialization vector.
+It is used to set the server's key which
+must be used to decrypt tickets.
+.PP
+If called with a non-zero second argument,
+.I krb_set_key
+will first convert the input from a string of arbitrary length to a DES
+key by encrypting it with a one-way function.
+.PP
+In most cases it should not be necessary to call
+.I krb_set_key.
+The necessary keys will usually be obtained and set inside
+.I krb_rd_req. krb_set_key
+is provided for those applications that do not wish to place the
+application keys on disk.
+.PP
+.I krb_get_cred
+searches the caller's ticket file for a ticket for the given service, instance,
+and realm; and, if a ticket is found, fills in the given CREDENTIALS structure
+with the ticket information.
+.PP
+If the ticket was found,
+.I krb_get_cred
+returns GC_OK.
+If the ticket file can't be found, can't be read, doesn't belong to
+the user (other than root), isn't a regular file, or is in the wrong
+mode, the error GC_TKFIL is returned.
+.PP
+.I krb_mk_priv
+creates an encrypted, authenticated
+message from any arbitrary application data, pointed to by
+.I in
+and
+.I in_length
+bytes long.
+The private session key, pointed to by
+.I key
+and the key schedule,
+.I schedule,
+are used to encrypt the data and some header information using
+.I pcbc_encrypt.
+.I sender
+and
+.I receiver
+point to the Internet address of the two parties.
+In addition to providing privacy, this protocol message protects
+against modifications, insertions or replays. The encapsulated message and
+header are placed in the area pointed to by
+.I out
+and the routine returns the length of the output, or -1 indicating
+an error.
+.PP
+.I krb_rd_priv
+decrypts and authenticates a received
+.I krb_mk_priv
+message.
+.I in
+points to the beginning of the received message, whose length
+is specified in
+.I in_length.
+The private session key, pointed to by
+.I key,
+and the key schedule,
+.I schedule,
+are used to decrypt and verify the received message.
+.I msg_data
+is a pointer to a
+.I MSG_DAT
+struct, defined in
+.I krb.h.
+The routine fills in the
+.I app_data
+field with a pointer to the decrypted application data,
+.I app_length
+with the length of the
+.I app_data
+field,
+.I time_sec
+and
+.I time_5ms
+with the timestamps in the message, and
+.I swap
+with a 1 if the byte order of the receiver is different than that of
+the sender. (The application must still determine if it is appropriate
+to byte-swap application data; the Kerberos protocol fields are already taken
+care of). The
+.I hash
+field returns a value useful as input to the
+.I krb_ck_repl
+routine.
+
+The routine returns zero if ok, or a Kerberos error code. Modified messages
+and old messages cause errors, but it is up to the caller to
+check the time sequence of messages, and to check against recently replayed
+messages using
+.I krb_ck_repl
+if so desired.
+.PP
+.I krb_mk_safe
+creates an authenticated, but unencrypted message from any arbitrary
+application data,
+pointed to by
+.I in
+and
+.I in_length
+bytes long.
+The private session key, pointed to by
+.I key,
+is used to seed the
+.I quad_cksum()
+checksum algorithm used as part of the authentication.
+.I sender
+and
+.I receiver
+point to the Internet address of the two parties.
+This message does not provide privacy, but does protect (via detection)
+against modifications, insertions or replays. The encapsulated message and
+header are placed in the area pointed to by
+.I out
+and the routine returns the length of the output, or -1 indicating
+an error.
+The authentication provided by this routine is not as strong as that
+provided by
+.I krb_mk_priv
+or by computing the checksum using
+.I cbc_cksum
+instead, both of which authenticate via DES.
+.PP
+
+.I krb_rd_safe
+authenticates a received
+.I krb_mk_safe
+message.
+.I in
+points to the beginning of the received message, whose length
+is specified in
+.I in_length.
+The private session key, pointed to by
+.I key,
+is used to seed the quad_cksum() routine as part of the authentication.
+.I msg_data
+is a pointer to a
+.I MSG_DAT
+struct, defined in
+.I krb.h .
+The routine fills in these
+.I MSG_DAT
+fields:
+the
+.I app_data
+field with a pointer to the application data,
+.I app_length
+with the length of the
+.I app_data
+field,
+.I time_sec
+and
+.I time_5ms
+with the timestamps in the message, and
+.I swap
+with a 1 if the byte order of the receiver is different than that of
+the sender.
+(The application must still determine if it is appropriate
+to byte-swap application data; the Kerberos protocol fields are already taken
+care of). The
+.I hash
+field returns a value useful as input to the
+.I krb_ck_repl
+routine.
+
+The routine returns zero if ok, or a Kerberos error code. Modified messages
+and old messages cause errors, but it is up to the caller to
+check the time sequence of messages, and to check against recently replayed
+messages using
+.I krb_ck_repl
+if so desired.
+.PP
+.I krb_mk_err
+constructs an application level error message that may be used along
+with
+.I krb_mk_priv
+or
+.I krb_mk_safe.
+.I out
+is a pointer to the output buffer,
+.I code
+is an application specific error code, and
+.I string
+is an application specific error string.
+
+.PP
+.I krb_rd_err
+unpacks a received
+.I krb_mk_err
+message.
+.I in
+points to the beginning of the received message, whose length
+is specified in
+.I in_length.
+.I code
+is a pointer to a value to be filled in with the error
+value provided by the application.
+.I msg_data
+is a pointer to a
+.I MSG_DAT
+struct, defined in
+.I krb.h .
+The routine fills in these
+.I MSG_DAT
+fields: the
+.I app_data
+field with a pointer to the application error text,
+.I app_length
+with the length of the
+.I app_data
+field, and
+.I swap
+with a 1 if the byte order of the receiver is different than that of
+the sender. (The application must still determine if it is appropriate
+to byte-swap application data; the Kerberos protocol fields are already taken
+care of).
+
+The routine returns zero if the error message has been successfully received,
+or a Kerberos error code.
+.PP
+The
+.I KTEXT
+structure is used to pass around text of varying lengths. It consists
+of a buffer for the data, and a length. krb_rd_req takes an argument of this
+type containing the authenticator, and krb_mk_req returns the
+authenticator in a structure of this type. KTEXT itself is really a
+pointer to the structure. The actual structure is of type KTEXT_ST.
+.PP
+The
+.I AUTH_DAT
+structure is filled in by krb_rd_req. It must be allocated before
+calling krb_rd_req, and a pointer to it is passed. The structure is
+filled in with data obtained from Kerberos.
+.I MSG_DAT
+structure is filled in by either krb_rd_priv, krb_rd_safe, or
+krb_rd_err. It must be allocated before the call and a pointer to it
+is passed. The structure is
+filled in with data obtained from Kerberos.
+.PP
+.SH FILES
+/usr/include/kerberosIV/krb.h
+.br
+/usr/lib/libkrb.a
+.br
+/usr/include/kerberosIV/des.h
+.br
+/usr/lib/libdes.a
+.br
+/etc/kerberosIV/aname
+.br
+/etc/kerberosIV/srvtab
+.br
+/tmp/tkt[uid]
+.SH "SEE ALSO"
+kerberos(1), des_crypt(3)
+.SH DIAGNOSTICS
+.SH BUGS
+The caller of
+.I krb_rd_req, krb_rd_priv, and krb_rd_safe
+must check time order and for replay attempts.
+.I krb_ck_repl
+is not implemented yet.
+.SH AUTHORS
+Clifford Neuman, MIT Project Athena
+.br
+Steve Miller, MIT Project Athena/Digital Equipment Corporation
+.SH RESTRICTIONS
+COPYRIGHT 1985,1986,1989 Massachusetts Institute of Technology
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