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/* $OpenBSD: recvauth.c,v 1.6 1998/02/25 15:51:37 art Exp $ */
/* $KTH: recvauth.c,v 1.18 1997/07/05 01:35:15 assar Exp $ */
/*
* This source code is no longer held under any constraint of USA
* `cryptographic laws' since it was exported legally. The cryptographic
* functions were removed from the code and a "Bones" distribution was
* made. A Commodity Jurisdiction Request #012-94 was filed with the
* USA State Department, who handed it to the Commerce department. The
* code was determined to fall under General License GTDA under ECCN 5D96G,
* and hence exportable. The cryptographic interfaces were re-added by Eric
* Young, and then KTH proceeded to maintain the code in the free world.
*
*/
/*
* Copyright (C) 1989 by the Massachusetts Institute of Technology
*
* Export of this software from the United States of America is assumed
* to require a specific license from the United States Government.
* It is the responsibility of any person or organization contemplating
* export to obtain such a license before exporting.
*
* WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
* distribute this software and its documentation for any purpose and
* without fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright notice and
* this permission notice appear in supporting documentation, and that
* the name of M.I.T. not be used in advertising or publicity pertaining
* to distribution of the software without specific, written prior
* permission. M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is" without express
* or implied warranty.
*
*/
#include "krb_locl.h"
#ifndef MAX
#define MAX(a,b) (((a)>(b))?(a):(b))
#endif /* MAX */
#ifndef MIN
#define MIN(a,b) (((a)<(b))?(a):(b))
#endif /* MIN */
/*
* krb_recvauth() reads (and optionally responds to) a message sent
* using krb_sendauth(). The "options" argument is a bit-field of
* selected options (see "sendauth.c" for options description).
* The only option relevant to krb_recvauth() is KOPT_DO_MUTUAL
* (mutual authentication requested). The "fd" argument supplies
* a file descriptor to read from (and write to, if mutual authenti-
* cation is requested).
*
* Part of the received message will be a Kerberos ticket sent by the
* client; this is read into the "ticket" argument. The "service" and
* "instance" arguments supply the server's Kerberos name. If the
* "instance" argument is the string "*", it is treated as a wild card
* and filled in during the krb_rd_req() call (see read_service_key()).
*
* The "faddr" and "laddr" give the sending (client) and receiving
* (local server) network addresses. ("laddr" may be left NULL unless
* mutual authentication is requested, in which case it must be set.)
*
* The authentication information extracted from the message is returned
* in "kdata". The "filename" argument indicates the file where the
* server's key can be found. (It is passed on to krb_rd_req().) If
* left null, the default "/etc/srvtab" will be used.
*
* If mutual authentication is requested, the session key schedule must
* be computed in order to reply; this schedule is returned in the
* "schedule" argument. A string containing the application version
* number from the received message is returned in "version", which
* should be large enough to hold a KRB_SENDAUTH_VLEN-character string.
*
* See krb_sendauth() for the format of the received client message.
*
* krb_recvauth() first reads the protocol version string from the
* given file descriptor. If it doesn't match the current protocol
* version (KRB_SENDAUTH_VERS), the old-style format is assumed. In
* that case, the string of characters up to the first space is read
* and interpreted as the ticket length, then the ticket is read.
*
* If the first string did match KRB_SENDAUTH_VERS, krb_recvauth()
* next reads the application protocol version string. Then the
* ticket length and ticket itself are read.
*
* The ticket is decrypted and checked by the call to krb_rd_req().
* If no mutual authentication is required, the result of the
* krb_rd_req() call is retured by this routine. If mutual authenti-
* cation is required, a message in the following format is returned
* on "fd":
*
* Size Variable Field
* ---- -------- -----
*
* 4 bytes tkt_len length of ticket or -1
* if error occurred
*
* priv_len tmp_buf "private" message created
* by krb_mk_priv() which
* contains the incremented
* checksum sent by the client
* encrypted in the session
* key. (This field is not
* present in case of error.)
*
* If all goes well, KSUCCESS is returned; otherwise KFAILURE or some
* other error code is returned.
*/
static int
send_error_reply(int fd)
{
unsigned char tmp[4] = { 255, 255, 255, 255 };
if(krb_net_write(fd, tmp, sizeof(tmp)) != sizeof(tmp))
return -1;
return 0;
}
int
krb_recvauth(int32_t options, /* bit-pattern of options */
int fd, /* file descr. to read from */
KTEXT ticket, /* storage for client's ticket */
char *service, /* service expected */
char *instance, /* inst expected (may be filled in) */
struct sockaddr_in *faddr, /* address of foreign host on fd */
struct sockaddr_in *laddr, /* local address */
AUTH_DAT *kdata, /* kerberos data (returned) */
char *filename, /* name of file with service keys */
struct des_ks_struct *schedule, /* key schedule (return) */
char *version) /* version string (filled in) */
{
int cc;
char krb_vers[KRB_SENDAUTH_VLEN + 1]; /* + 1 for the null terminator */
int rem;
int32_t priv_len;
u_char tmp_buf[MAX_KTXT_LEN+MAX(KRB_SENDAUTH_VLEN+1,21)];
if (!(options & KOPT_IGNORE_PROTOCOL)) {
/* read the protocol version number */
if (krb_net_read(fd, krb_vers, KRB_SENDAUTH_VLEN) != KRB_SENDAUTH_VLEN)
return(errno);
krb_vers[KRB_SENDAUTH_VLEN] = '\0';
}
/* read the application version string */
if (krb_net_read(fd, version, KRB_SENDAUTH_VLEN) != KRB_SENDAUTH_VLEN)
return(errno);
version[KRB_SENDAUTH_VLEN] = '\0';
/* get the length of the ticket */
{
char tmp[4];
if (krb_net_read(fd, tmp, 4) != 4)
return -1;
krb_get_int(tmp, &ticket->length, 4, 0);
}
/* sanity check */
if (ticket->length <= 0 || ticket->length > MAX_KTXT_LEN) {
if (options & KOPT_DO_MUTUAL) {
if(send_error_reply(fd))
return -1;
return KFAILURE;
} else
return KFAILURE; /* XXX there may still be junk on the fd? */
}
/* read the ticket */
if (krb_net_read(fd, ticket->dat, ticket->length) != ticket->length)
return -1;
/*
* now have the ticket. decrypt it to get the authenticated
* data.
*/
rem = krb_rd_req(ticket, service, instance, faddr->sin_addr.s_addr,
kdata, filename);
/* if we are doing mutual auth, compose a response */
if (options & KOPT_DO_MUTUAL) {
if (rem != KSUCCESS){
/* the krb_rd_req failed */
if(send_error_reply(fd))
return -1;
return rem;
}
/* add one to the (formerly) sealed checksum, and re-seal it
for return to the client */
{
unsigned char cs[4];
krb_put_int(kdata->checksum + 1, cs, 4);
#ifndef NOENCRYPTION
des_key_sched(&kdata->session,schedule);
#endif
priv_len = krb_mk_priv(cs,
tmp_buf+4,
4,
schedule,
&kdata->session,
laddr,
faddr);
}
/* mk_priv will never fail */
priv_len += krb_put_int(priv_len, tmp_buf, 4);
if((cc = krb_net_write(fd, tmp_buf, priv_len)) != priv_len)
return -1;
}
return rem;
}
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