/* * Copyright 1986, 1987, 1988 by the Massachusetts Institute * of Technology. * For copying and distribution information, please see the file * . * * 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 1.1.1.1 1994/09/30 14:50:03 csgr Exp $ */ #ifndef lint static char rcsid[] = "$Id: rd_safe.c,v 1.1.1.1 1994/09/30 14:50:03 csgr Exp $"; #endif /* lint */ /* system include files */ #include #include #include #include #include /* application include files */ #include #include #include #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 */ }