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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 'private msg', decrypting it,
* 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_...). If
* the return value is RD_AP_TIME, then either the times are too far
* out of synch, OR the packet was modified.
*
* Steve Miller Project Athena MIT/DEC
*
* from: rd_priv.c,v 4.14 89/04/28 11:59:42 jtkohl Exp $
* $FreeBSD$
*/
#if 0
#ifndef lint
static char rcsid[]=
"$FreeBSD$";
#endif /* lint */
#endif
/* system include files */
#include <string.h>
#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 int krb_debug;
/* static storage */
static u_long c_length;
static int swap_bytes;
static struct timeval local_time;
static long delta_t;
int private_msg_ver = KRB_PROT_VERSION;
/*
#ifdef NOENCRPYTION
* krb_rd_priv() checks the integrity of an
#else
* krb_rd_priv() decrypts and checks the integrity of an
#endif
* AUTH_MSG_PRIVATE message. Given the message received, "in",
* the length of that message, "in_length", the key "schedule"
* and "key", and the network addresses of the
* "sender" and "receiver" of the message, krb_rd_safe() returns
* RD_AP_OK if the message is okay, otherwise some error code.
*
* The message data retrieved from "in" are 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_priv.c" for the format of the AUTH_MSG_PRIVATE
* message. The structure containing the extracted message
* information, MSG_DAT, is defined in "krb.h".
*/
long
krb_rd_priv(in,in_length,schedule,key,sender,receiver,m_data)
u_char *in; /* pointer to the msg received */
u_long in_length; /* length of "in" msg */
Key_schedule schedule; /* precomputed key schedule */
C_Block key; /* encryption key for seed and ivec */
struct sockaddr_in *sender;
struct sockaddr_in *receiver;
MSG_DAT *m_data; /*various input/output data from msg */
{
register u_char *p,*q;
static u_long src_addr; /* Can't send structs since no
* guarantees on size */
if (gettimeofday(&local_time,(struct timezone *)0))
return -1;
p = in; /* beginning of message */
swap_bytes = 0;
if (*p++ != KRB_PROT_VERSION && *(p-1) != 3)
return RD_AP_VERSION;
private_msg_ver = *(p-1);
if (((*p) & ~1) != AUTH_MSG_PRIVATE)
return RD_AP_MSG_TYPE;
if ((*p++ & 1) != HOST_BYTE_ORDER)
swap_bytes++;
/* get cipher length */
bcopy((char *)p,(char *)&c_length,sizeof(c_length));
if (swap_bytes)
swap_u_long(c_length);
p += sizeof(c_length);
/* check for rational length so we don't go comatose */
if (VERSION_SZ + MSG_TYPE_SZ + c_length > in_length)
return RD_AP_MODIFIED;
q = p; /* mark start of encrypted stuff */
#ifndef NOENCRYPTION
pcbc_encrypt((C_Block *)q,(C_Block *)q,(long)c_length,schedule,
(C_Block *)key,DECRYPT);
#endif
/* safely get application data 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(c_length) + sizeof(in_length) +
sizeof(m_data->time_sec) + sizeof(m_data->time_5ms) +
sizeof(src_addr) + VERSION_SZ + MSG_TYPE_SZ
> in_length)
return RD_AP_MODIFIED;
#ifndef NOENCRYPTION
/* we're now at the decrypted application data */
#endif
m_data->app_data = p;
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;
if (krb_debug)
printf("\ndelta_t = %ld",delta_t);
/*
* 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.
*/
#ifdef notdef
bcopy((char *) p,(char *)&cksum,sizeof(cksum));
if (swap_bytes) swap_u_long(cksum)
/*
* calculate the checksum of the length, sequence,
* and input data, on the sending byte order!!
*/
calc_cksum = quad_cksum(q,NULL,p-q,0,key);
if (krb_debug)
printf("\ncalc_cksum = %u, received cksum = %u",
calc_cksum, cksum);
if (cksum != calc_cksum)
return RD_AP_MODIFIED;
#endif
return RD_AP_OK; /* OK == 0 */
}
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