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/* Nessuslib -- the Nessus Library
* Copyright (C) 2000 Renaud Deraison
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free
* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*
* Banner comparison functions. The problem with banner comparison is that
* a lot of banners display the current time of the day along their lines.
* This does not ease our task which will be to determine if a change in
* two banners is due to a time change or something else.
*/
#include <includes.h>
#undef DEBUG
/*------------------------------------------------------------------------*
* Private definitions *
*------------------------------------------------------------------------*/
#define abs(x) ((x)>0?(x):-(x))
#define NO_DATE 0
#define IS_DATE 1
#define NEED_CONTEXT 2
/*
* Return <1> if <a> appears to be a date.
*
* <a> will not be a valid date if :
* - the timezone changes
* - two numbers are separated by spaces. For instance "4 12 Sep" is
* *not* a date
*
* - it contains something else than a digit, space, comma, semi-column,
* {Mon...Sun} or {Jan..Dec}
*/
static int
is_date(a)
char *a;
{
int i, l;
int space = 0;
int digit = 0;
l = strlen(a);
if(l==1)return NEED_CONTEXT;
for(i=0;i<l;i++)
{
if(isdigit(a[i])){
if(space && digit){
return 0;
}
digit++;
space = 0;
continue;
}
else if(a[i]==':'){
space = 0;
continue;
}
else if(a[i]=='+'){
space = 0;
continue;
}
else if(a[i]==' '){
space++;
continue;
}
else if(a[i]==','){
space = 0;
continue;
}
else {
if((!strncmp(a+i, "Mon", 3))||
(!strncmp(a+i, "Tue", 3))||
(!strncmp(a+i, "Wed", 3))||
(!strncmp(a+i, "Thu", 3))||
(!strncmp(a+i, "Fri", 3))||
(!strncmp(a+i, "Sat", 3))||
(!strncmp(a+i, "Sun", 3))||
(!strncmp(a+i, "Jan", 3))||
(!strncmp(a+i, "Feb", 3))||
(!strncmp(a+i, "Mar", 3))||
(!strncmp(a+i, "Apr", 3))||
(!strncmp(a+i, "May", 3))||
(!strncmp(a+i, "Jun", 3))||
(!strncmp(a+i, "Jul", 3))||
(!strncmp(a+i, "Aug", 3))||
(!strncmp(a+i, "Sep", 3))||
(!strncmp(a+i, "Oct", 3))||
(!strncmp(a+i, "Nov", 3))||
(!strncmp(a+i, "Dec", 3))){
i+=2;
space = 0;
digit = 0;
continue;
}
}
return 0; /* this is not a date */
}
return 1; /* no error - this is a date */
}
/*------------------------------------------------------------------------*
* Public functions *
*------------------------------------------------------------------------*/
/*
* Returns <1> if <a> and <b> are not the same. This is more complicated
* than a strcmp() as dates are taken in account.
*/
int banner_diff(a,b)
char * a, * b;
{
int l_a, l_b , i_a, i_b;
char * copy = NULL;
l_a = strlen(a);
l_b = strlen(b);
/*
* We tolerate a difference in length of 3 chars at max
*/
if(abs(l_a - l_b) > 3)
{
return 1;
}
/*
* <b> must always be the longest string
*/
if(l_b < l_a)
{
char * t = a;
int t_i;
a = b;
b = t;
t_i = l_a;
l_a = l_b;
l_b = t_i;
}
for(i_a=0, i_b=0;(i_b<l_b) && (i_a<l_a);i_a++, i_b++)
{
if(a[i_a] != b[i_b])
{
/*
* Once we spot a difference, we
* go through the string backward, until we
* find another place which differs.
*/
int j = 0, k = 0;
int res;
#ifdef DEBUG
printf("SPOTTED %c != %c\n", a[i_a], b[i_b]);
#endif
copy = (char*)malloc(l_b - i_b + 1);
bzero(copy, l_b - i_b + 1);
for(j=strlen(a), k=strlen(b);(j>i_a)&&(k>i_b)&&(a[j]==b[k]);j--,k--);
#ifdef DEBUG
printf("END : %s\n", b+k);
#endif
bcopy (b + i_b, copy, (k-i_b) + 1);
#ifdef DEBUG
printf("Copy : '%s'\n", copy);
#endif
res = is_date(copy);
#ifdef DEBUG
printf("isdate(copy) = %d\n", res);
#endif
if(res == NEED_CONTEXT)
{
copy = realloc(copy, (k-i_b) + 1 + 4);
bcopy (b + i_b, copy, (k-i_b) + 1 + 4);
res = is_date(copy);
}
free(copy);
i_b+=(k-i_b);
i_a+=(j-i_a);
if(res==IS_DATE)continue;
else return 1;
}
}
return 0;
}
#ifdef DEBUG
void main()
{
printf("%d (should be 1)\n", banner_diff("Sendmail 1.2.3",
"Sendmail 1.4.3"));
printf("%d (should be 0)\n", banner_diff("Sendmail 1.2.3, 4 Oct 2000", "Sendmail 1.2.3, 29 Dec 2002"));
printf("%d (should be 1)\n", banner_diff("Sendmail 1.2.4 3 Oct 2000",
"Sendmail 1.2.5 3 Oct 2000"));
}
#endif
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