+/*
+ * $Source: /mit/kerberos/src/lib/krb/RCS/rd_priv.c,v $
+ * $Author: jtkohl $
+ *
+ * Copyright 1986, 1987, 1988 by the Massachusetts Institute
+ * of Technology.
+ *
+ * For copying and distribution information, please see the file
+ * <mit-copyright.h>.
+ *
+ * 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
+ */
+
+#ifndef lint
+static char *rcsid_rd_priv_c=
+"$Header: rd_priv.c,v 4.14 89/04/28 11:59:42 jtkohl Exp $";
+#endif /* lint */
+
+#include <mit-copyright.h>
+
+/* 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 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"
+#ifdef NOENCRYPTION
+ * and "key", and the network addresses of the
+#else
+ * and "key" to decrypt with, and the network addresses of the
+#endif
+ * "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
+#ifdef NOENCRYPTION
+ * "m_data". The pointer to the application data
+#else
+ * "m_data". The pointer to the decrypted application data
+#endif
+ * (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;
+
+#ifndef NOENCRYPTION
+ /*
+ * decrypt to obtain length, timestamps, app_data, and checksum
+ * use the session key as an ivec
+ */
+#endif
+
+ q = p; /* mark start of encrypted stuff */
+
+#ifndef NOENCRYPTION
+ /* pcbc decrypt, use key as ivec */
+ pcbc_encrypt((C_Block *) q,(C_Block *) q, (long) c_length,
+ schedule,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 = %d",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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