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/*
* Copyright 1986, 1987, 1988 by the Massachusetts Institute
* of Technology.
* For copying and distribution information, please see the file
* <Copyright.MIT>.
*
* This routine dissects a a Kerberos 'safe msg', checking its
* integrity, and returning a pointer to the application data
* contained and its length.
*
* Returns 0 (RD_AP_OK) for success or an error code (RD_AP_...)
*
* Steve Miller Project Athena MIT/DEC
*
* from: rd_safe.c,v 4.12 89/01/23 15:16:16 steiner Exp $
* $Id: rd_safe.c,v 1.2 1994/07/19 19:26:15 g89r4222 Exp $
*/
#ifndef lint
static char rcsid[] =
"$Id: rd_safe.c,v 1.2 1994/07/19 19:26:15 g89r4222 Exp $";
#endif /* lint */
/* system include files */
#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/time.h>
/* application include files */
#include <des.h>
#include <krb.h>
#include <prot.h>
#include "lsb_addr_comp.h"
extern char *errmsg();
extern int errno;
extern int krb_debug;
/* static storage */
static C_Block calc_cksum[2];
static C_Block big_cksum[2];
static int swap_bytes;
static struct timeval local_time;
static u_long delta_t;
/*
* krb_rd_safe() checks the integrity of an AUTH_MSG_SAFE message.
* Given the message received, "in", the length of that message,
* "in_length", the "key" to compute the checksum with, and the
* network addresses of the "sender" and "receiver" of the message,
* krb_rd_safe() returns RD_AP_OK if message is okay, otherwise
* some error code.
*
* The message data retrieved from "in" is returned in the structure
* "m_data". The pointer to the application data (m_data->app_data)
* refers back to the appropriate place in "in".
*
* See the file "mk_safe.c" for the format of the AUTH_MSG_SAFE
* message. The structure containing the extracted message
* information, MSG_DAT, is defined in "krb.h".
*/
long krb_rd_safe(in,in_length,key,sender,receiver,m_data)
u_char *in; /* pointer to the msg received */
u_long in_length; /* length of "in" msg */
C_Block *key; /* encryption key for seed and ivec */
struct sockaddr_in *sender; /* sender's address */
struct sockaddr_in *receiver; /* receiver's address -- me */
MSG_DAT *m_data; /* where to put message information */
{
register u_char *p,*q;
static u_long src_addr; /* Can't send structs since no
* guarantees on size */
/* Be very conservative */
if (sizeof(u_long) != sizeof(struct in_addr)) {
fprintf(stderr,"\n\
krb_rd_safe protocol err sizeof(u_long) != sizeof(struct in_addr)");
exit(-1);
}
if (gettimeofday(&local_time,(struct timezone *)0))
return -1;
p = in; /* beginning of message */
swap_bytes = 0;
if (*p++ != KRB_PROT_VERSION) return RD_AP_VERSION;
if (((*p) & ~1) != AUTH_MSG_SAFE) return RD_AP_MSG_TYPE;
if ((*p++ & 1) != HOST_BYTE_ORDER) swap_bytes++;
q = p; /* mark start of cksum stuff */
/* safely get length */
bcopy((char *)p,(char *)&(m_data->app_length),
sizeof(m_data->app_length));
if (swap_bytes) swap_u_long(m_data->app_length);
p += sizeof(m_data->app_length); /* skip over */
if (m_data->app_length + sizeof(in_length)
+ sizeof(m_data->time_sec) + sizeof(m_data->time_5ms)
+ sizeof(big_cksum) + sizeof(src_addr)
+ VERSION_SZ + MSG_TYPE_SZ > in_length)
return(RD_AP_MODIFIED);
m_data->app_data = p; /* we're now at the application data */
/* skip app data */
p += m_data->app_length;
/* safely get time_5ms */
bcopy((char *)p, (char *)&(m_data->time_5ms),
sizeof(m_data->time_5ms));
/* don't need to swap-- one byte for now */
p += sizeof(m_data->time_5ms);
/* safely get src address */
bcopy((char *)p,(char *)&src_addr,sizeof(src_addr));
/* don't swap, net order always */
p += sizeof(src_addr);
if (src_addr != (u_long) sender->sin_addr.s_addr)
return RD_AP_MODIFIED;
/* safely get time_sec */
bcopy((char *)p, (char *)&(m_data->time_sec),
sizeof(m_data->time_sec));
if (swap_bytes)
swap_u_long(m_data->time_sec);
p += sizeof(m_data->time_sec);
/* check direction bit is the sign bit */
/* For compatibility with broken old code, compares are done in VAX
byte order (LSBFIRST) */
if (lsb_net_ulong_less(sender->sin_addr.s_addr,
receiver->sin_addr.s_addr)==-1)
/* src < recv */
m_data->time_sec = - m_data->time_sec;
else if (lsb_net_ulong_less(sender->sin_addr.s_addr,
receiver->sin_addr.s_addr)==0)
if (lsb_net_ushort_less(sender->sin_port,receiver->sin_port)==-1)
/* src < recv */
m_data->time_sec = - m_data->time_sec;
/*
* All that for one tiny bit! Heaven help those that talk to
* themselves.
*/
/* check the time integrity of the msg */
delta_t = abs((int)((long) local_time.tv_sec - m_data->time_sec));
if (delta_t > CLOCK_SKEW) return RD_AP_TIME;
/*
* caller must check timestamps for proper order and replays, since
* server might have multiple clients each with its own timestamps
* and we don't assume tightly synchronized clocks.
*/
bcopy((char *)p,(char *)big_cksum,sizeof(big_cksum));
if (swap_bytes) swap_u_16(big_cksum);
#ifdef NOENCRYPTION
bzero(calc_cksum, sizeof(calc_cksum));
#else
quad_cksum(q,calc_cksum,p-q,2,key);
#endif
if (krb_debug)
printf("\ncalc_cksum = %u, received cksum = %u",
(long) calc_cksum[0], (long) big_cksum[0]);
if (bcmp((char *)big_cksum,(char *)calc_cksum,sizeof(big_cksum)))
return(RD_AP_MODIFIED);
return(RD_AP_OK); /* OK == 0 */
}
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