a self-checking program in standard C

R

RoSsIaCrIiLoIA

Do you know how to write a self-checking program in standard C?
Do I can think that if I write in a file.c
static g[100]="1234567";
in the file.exe (or file) there is in some place
1234567'\0''\0''\0''\0''\0''\0''\0'...'\0'

This is my first attempt:

/* file.c -> file.exe */
#include <stdio.h>
#include <string.h>

char* estr(char* nome)
{
char *a = nome, *b;
char c;
if(nome == 0)
return 0;
while( 1 )
{b = a;
while( (c = *a) && c != '\\' && c != '/' )
++a;
if(c == 0) break;
++a;
}
return b;
}

int main(int c, char** argv)
{
(void) c;
printf("I'm a self-checking program\n");
if(strncmp("dc.exe", estr(argv[0]), 6) != 0)
{printf("File corrupted\n"); return 0;}
printf("Continue\n");
return 0;
}
 
V

Victor Nazarov

RoSsIaCrIiLoIA said:
Do you know how to write a self-checking program in standard C?
Do I can think that if I write in a file.c
static g[100]="1234567";
in the file.exe (or file) there is in some place
1234567'\0''\0''\0''\0''\0''\0''\0'...'\0'
Click to expand...

I think you can. But it is out of Standard C scope.

This is my first attempt:

/* file.c -> file.exe */
#include <stdio.h>
#include <string.h>

char* estr(char* nome)
{
char *a = nome, *b;
char c;
if(nome == 0)
return 0;
while( 1 )
{b = a;
while( (c = *a) && c != '\\' && c != '/' )
Click to expand...

what about c != '\0'
++a;
if(c == 0) break;
++a;
}
return b;
}

int main(int c, char** argv)
{
(void) c;
printf("I'm a self-checking program\n");
if(strncmp("dc.exe", estr(argv[0]), 6) != 0)
{printf("File corrupted\n"); return 0;}
Click to expand...

Why do you think this garanties that file is corrupted? Why user
shouldn't rename files? If he shouldn't then you must consider that file
may had more than one name in some environments (hard and symbolic links).
printf("Continue\n");
return 0;
}
Click to expand...

How does this code relate with your proposal made in the begining.

Anyway all of this is offtopic here.

vir
 
R

RoSsIaCrIiLoIA

RoSsIaCrIiLoIA said:
Do you know how to write a self-checking program in standard C?
Do I can think that if I write in a file.c
static g[100]="1234567";
in the file.exe (or file) there is in some place
1234567'\0''\0''\0''\0''\0''\0''\0'...'\0'
Click to expand...

I think you can. But it is out of Standard C scope.
Click to expand...

But are there any system where this is not true?
what about c != '\0'
Click to expand...

ok (c = *a)!=0
++a;
if(c == 0) break;
++a;
}
return b;
}

int main(int c, char** argv)
{
(void) c;
printf("I'm a self-checking program\n");
if(strncmp("dc.exe", estr(argv[0]), 6) != 0)
{printf("File corrupted\n"); return 0;}
Click to expand...

Why do you think this garanties that file is corrupted? Why user
shouldn't rename files? If he shouldn't then you must consider that file
may had more than one name in some environments (hard and symbolic links).
Click to expand...

I'm thinking some of this type:

/* my1.c */
#include <string.h>
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#define UNS unsigned

char* estr(char* nome)
{
char *a = nome, *b;
char c;
if(nome == 0)
return 0;
while( 1 )
{b = a;
while( (c = *a)!=0 && c!='\\' && c!='/' )
++a;
if(c == 0) break;
++a;
}
return b;
}


int info_p(char* );

int main(int c, char** argv)
{
if(c != 2)
{
if( c==0 || !argv[0] )
printf("Use:> this_prog prog\n");
else printf("Use:> %s prog[.exe]\n", estr(argv[0]));

return 0;
}
if( info_p( argv[1] )==0 )
{ printf("Not signed %s\n", estr(argv[1])); return 0;}

printf("Ok signed %s\n", estr(argv[1]));
return 0;
}

void printu(char* a)
{
int i;
for( i = 0; i < sizeof(UNS); ++i)
printf(" %d ", (int) a);
}


int f(const char* a, FILE* fp)
{
int i, j;
for( i= 0, j= EOF + 1 ; i < sizeof(UNS) && j!=EOF; ++i)
j= fputc(a, fp);
return j;
}

int info_p(char* as)
{int c, r, k, cp;
FILE *fp;
unsigned count= 0, rox= 0, sum= 0, *p1, buffer= 0;
char acount[ sizeof(UNS) + 8 ] = {0},
arox [ sizeof(UNS) + 8 ] = {0},
asum [ sizeof(UNS) + 8 ] = {0};
char *pc1 = acount, *pc2 = arox, *pc3 = asum;
long ove;

if( (fp = fopen( as, "r+b"))==NULL )
{printf("Problemi di apertura\n");
return 0;
}
r = 0; cp = 0;
label:
while( (c = fgetc(fp))!=EOF && !(cp=='1' && c=='2') )
{
sum += c; ++count;
cp = c;
buffer = (buffer << CHAR_BIT) | ((UNS)(unsigned char) c);
if(count % sizeof(UNS) ==0)
rox = rox ^ buffer;
}
if( c!=EOF && r==0 )
{k = 2;
while( (c = fgetc(fp))!=EOF && c-'0'== ++k )
{sum += c; ++count;
cp = c;
buffer = (buffer << CHAR_BIT) | (UNS)((unsigned char) c);
if(count % sizeof(UNS) == 0)
rox = rox ^ buffer;
} /*34567*/
if( k==8 && c!=EOF )
{
if((ove = ftell( fp ))== -1)
{ printf("Error\n"); exit(0); }
printf("Find\n");
r=1;
}
else if(c != EOF) goto label;
else goto fine;
while( (c = fgetc(fp))!=EOF && k!=512 ) ++k;
if(c !=EOF) goto label;
}
if(c == EOF) goto fine;
goto label;
fine:
*(UNS*) pc1 = count; *(UNS*) pc2 = rox; *(UNS*) pc3 = sum;
if(r == 1)
{
fseek(fp, ove, SEEK_SET);
clearerr(fp);
if(f(acount, fp)==EOF || f(arox, fp)==EOF || f(asum, fp)==EOF)
{r=0; printf("Error in writing\n");}
}
fclose(fp);
printf("count=%u rox=%u sum=%u\n", count, rox, sum );
printf("String=%s%s%s\nIn_num=", acount, arox, asum);
printu(acount); printf("M") ;printu(arox);printf("M");
printu(asum) ; printf("\n");
return r;
}
/*end my1.c*/
____________________

/* ali.c */
#include <string.h>
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>

#define UNS unsigned


char* estr(char* nome)
{
char *a = nome, *b;
char c;

if(nome == 0)
return 0;
while( 1 )
{
b = a;
while( (c = *a)!=0 && c!='\\' && c!='/' ) ++a;
if(c == 0) break;
++a;
}
return b;
}

int info_p(char* );

int main(int c, char** argv)
{
printf("Start \n");
if( c==0 || !argv[0] )
return 0;
if( info_p(argv[0]) == 0 )
{ printf("File corrupted\n"); return 0; }
printf("oK continue\n");
return 0;
}


void printu(char* a)
{
int i;

for( i = 0 ; i < sizeof(UNS) ; ++i)
printf(" %d ", (int) a);
}

int f(const char* a, FILE* fp)
{
int i, j;

for( i = 0 ; i < sizeof(UNS) ; ++i)
{
if( (j = fgetc( fp ))==EOF ) return 0;
if( j != (unsigned char) a) return 0;
}
return 1;
}

/* ###### HERE WE HAVE TO WRITE ###### */
char al[512] = "1234567 ";


int info_p(char* as)
{
int l, c, r, k, cp;
FILE *fp;
unsigned count = 0, rox = 0, sum = 0, *p1, buffer = 0;
char acount[ sizeof(UNS) + 8 ] = {0},
arox [ sizeof(UNS) + 8 ] = {0},
asum [ sizeof(UNS) + 8 ] = {0};
char *pc1 = acount, *pc2 = arox, *pc3 = asum;
long ove;

if((fp = fopen( as, "rb"))==NULL)
{
printf("Problemi di apertura\n");
return 0;
}
r = 0; cp = 0;
label:
while((c = fgetc(fp))!=EOF && !(cp=='1' && c=='2'))
{
sum += c; ++count;
cp = c;
buffer = (buffer << CHAR_BIT) | ((UNS)(unsigned char) c);
if(count % sizeof(UNS) ==0)
rox = rox ^ buffer;
}
if(c!=EOF && r==0)
{
k = 2;
while((c = fgetc(fp))!=EOF && c== ++k + '0' )
{
sum += c; ++count;
cp = c;
buffer = (buffer << CHAR_BIT) | (UNS)((unsigned char) c);
if(count % sizeof(UNS) == 0)
rox = rox ^ buffer;
} /*34567*/
if(k==8 && c!=EOF)
{
if( (ove = ftell(fp)) == -1)
{ printf( "Error\n" ); exit( 0 ); }
r = 1;
}
else if(c != EOF) goto label;
else goto fine;
while((c = fgetc(fp))!=EOF && k!=512) ++k;
if(c !=EOF ) goto label;
}
if(c == EOF) goto fine;
goto label;
fine:
*(UNS*) pc1 = count; *(UNS*) pc2 = rox; *(UNS*) pc3 = sum;
if(r == 1){
fseek(fp, ove, SEEK_SET);
clearerr(fp);
if( f(acount, fp)==0 || f(arox, fp)==0 || f(asum, fp)==0 )
r = 0;
}
fclose(fp);
return r;
}
/*end ali.c*/
__________________


C:\b>ali
Start
File corrupted

C:\b>my1 ali.exe
Find
count=59909 rox=3806249208 sum=5559428
String=?Û°+ÌÔäÈT
In_num= 5 -22 0 0 M -8 -64 -34 -30 M -124 -44 84 0
Ok signed ali.exe

C:\b>ali
Start
oK continue
_______________

Are there errors?
Are there system where this doesn't run with success?
 
D

Dan Pop

In said:
Do you know how to write a self-checking program in standard C?
Click to expand...

I don't know what a self-checking program is in the first place.
Do I can think that if I write in a file.c
static g[100]="1234567";
in the file.exe (or file) there is in some place
1234567'\0''\0''\0''\0''\0''\0''\0'...'\0'
Click to expand...

Not necessarily. Long sequences of null bytes are so common that some
linkers compress them.
This is my first attempt:

/* file.c -> file.exe */
#include <stdio.h>
#include <string.h>

char* estr(char* nome)
{
char *a = nome, *b;
char c;
if(nome == 0)
return 0;
while( 1 )
{b = a;
while( (c = *a) && c != '\\' && c != '/' )
++a;
if(c == 0) break;
++a;
}
return b;
}

int main(int c, char** argv)
{
(void) c;
printf("I'm a self-checking program\n");
if(strncmp("dc.exe", estr(argv[0]), 6) != 0)
{printf("File corrupted\n"); return 0;}
printf("Continue\n");
return 0;
}
Click to expand...

Let's try it:

fangorn:~/tmp 371> gcc test.c
fangorn:~/tmp 372> ./a.out
I'm a self-checking program
File corrupted

Which file is corrupted and why? And how can you determine whether a
file is corrupted or not by examining argv[0]?

Dan
 
V

Victor Nazarov

RoSsIaCrIiLoIA said:
C:\b>ali
Start
File corrupted

C:\b>my1 ali.exe
Find
count=59909 rox=3806249208 sum=5559428
String=?Û°+ÌÔäÈT
In_num= 5 -22 0 0 M -8 -64 -34 -30 M -124 -44 84 0
Ok signed ali.exe

C:\b>ali
Start
oK continue
_______________

Are there errors?
Are there system where this doesn't run with success?
Click to expand...

This is not portable anyway. Really It depends on the executable format.
Executables often get comressed. Try another newsgroup...

vir
 
P

Paul M.

In said:
Do you know how to write a self-checking program in standard C?
Click to expand...

I don't know what a self-checking program is in the first place.
Do I can think that if I write in a file.c
static g[100]="1234567";
in the file.exe (or file) there is in some place
1234567'\0''\0''\0''\0''\0''\0''\0'...'\0'
Click to expand...

Not necessarily. Long sequences of null bytes are so common that some
linkers compress them.
This is my first attempt:

/* file.c -> file.exe */
#include <stdio.h>
#include <string.h>

char* estr(char* nome)
{
char *a = nome, *b;
char c;
if(nome == 0)
return 0;
while( 1 )
{b = a;
while( (c = *a) && c != '\\' && c != '/' )
++a;
if(c == 0) break;
++a;
} return b;
}

int main(int c, char** argv)
{
(void) c;
printf("I'm a self-checking program\n");
if(strncmp("dc.exe", estr(argv[0]), 6) != 0)
{printf("File corrupted\n"); return 0;}
printf("Continue\n");
return 0;
}
Click to expand...

Let's try it:

fangorn:~/tmp 371> gcc test.c
fangorn:~/tmp 372> ./a.out
I'm a self-checking program
File corrupted

Which file is corrupted and why? And how can you determine whether a
file is corrupted or not by examining argv[0]?

Dan
Click to expand...


A lot of work along these lines has already been done. A company that
I used to work for had visual studio add-in tools. See the page:
http://www.arxan.com/home/index.php

Paul
 
R

RoSsIaCrIiLoIA

[comp.lang.c, sci.crypt]
This is not portable anyway. Really It depends on the executable format.
Executables often get comressed. Try another newsgroup...
Click to expand...

yes compressed or *encrypted*
If the OS has a database of all the public key of software houses,
if M.exe is a encrypted program of Company XX
the loader of the OS could take the public key of Company XX
encrypt it [on the fly] and jump on it.

If a crakker want to crack M.exe he has to know the secret key of
Company XX or change the code in the memory space of that running
program.(in many OSes seems to me that the memory space of a program
is closed to other process)

Regarding Internet **why** OSes seems to have the default in allowing
*every* FTP-telnet-http-all *fu?king* protocol- IN EXIT for the
home-PC ( and change it in a world server of resources) ???
__________________
Il popolo dell'iraaq non vuole eserciti oppressori sia onu o altro
(se non ci credete fate un referendum)
Come ragionate con i piedi?
 
R

RoSsIaCrIiLoIA

#include <string.h>
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#define UNS unsigned

char* estr(char* nome)
{
char *a = nome, *b;
char c;
if(nome == 0)
return 0;
while( 1 )
{b = a;
while( (c = *a)!=0 && c!='\\' && c!='/' )
++a;
if(c == 0) break;
++a;
}
return b;
}


int info_p(char* , int );

int main(int c, char** ar)
{
char *pc;
int sign;

if(c == 2)
{
pc = ar[1];
sign = 0;
}
else if( c==3 && ar!=0 && ar[1]!=0 )
{
if( ar[1][0]!='-' || ar[1][1]!='s' || ar[1][2]!=0 )
goto label;
pc = ar[2];
sign = 1;
}
else
{
label:
printf("This program sign [-s] if possible an .exe\n");
printf("or calc and print its value on the screen\n");
if( c==0 || !ar[0] )
printf("Usage:> this_prog [-s] prog\n");
else printf("Usage:> %s [-s] prog[.exe]\n", estr(ar[0]));
return 0;
}
if( info_p( pc, sign )==0 )
{
if(sign)
printf("Not signed %s\n", estr(ar[1]));
return 0;
}

if(sign)
printf("Ok signed %s\n", estr(ar[2]));
return 0;
}


void printu(char* a)
{
int i;
for( i = 0; i < sizeof(UNS); ++i)
printf(" %u ", (UNS)(unsigned char) a);
}


int f(const char* a, FILE* fp)
{
int i, j;
for( i= 0, j= EOF + 1 ; i < sizeof(UNS) && j!=EOF; ++i)
j= fputc(a, fp);
return j;
}

int info_p(char* as, int sign)
{
int c, r, k, cp;
FILE *fp;
unsigned count= 0, rox= 0, sum= 0, *p1, buffer= 0;
char acount[ sizeof(UNS) + 8 ] = {0},
arox [ sizeof(UNS) + 8 ] = {0},
asum [ sizeof(UNS) + 8 ] = {0};
char *pc1 = acount, *pc2 = arox, *pc3 = asum;
long ove;

if(3*sizeof(UNS)>=512) return 0;
if( (fp = fopen( as, "r+b"))==NULL )
{
printf("Problemi di apertura\n");
return 0;
}
r = 0; cp = 0;
label:
while( (c = fgetc(fp))!=EOF && !(cp=='1' && c=='2') )
{
sum += c; ++count;
cp = c;
buffer = (buffer << CHAR_BIT) | ((UNS)(unsigned char) c);
if(count % sizeof(UNS) ==0)
rox = rox ^ buffer;
}
if( c!=EOF && r==0 )
{k = 2;
while( (c = fgetc(fp))!=EOF && c-'0'== ++k )
{
sum += c; ++count;
cp = c;
buffer = (buffer << CHAR_BIT) | (UNS)((unsigned char) c);
if(count % sizeof(UNS) == 0)
rox = rox ^ buffer;
} /*34567*/
if( k==8 && c!=EOF )
{
if((ove = ftell( fp ))== -1)
{ printf("Error\n"); exit(0); }
printf("Find\n");
r=1;
}
else if(c != EOF) goto label;
else goto fine;
while( (c = fgetc(fp))!=EOF && k!=512 ) ++k;
if( c!=EOF ) goto label;
}
if( c==EOF ) goto fine;
goto label;
fine:
*(UNS*) pc1 = count; *(UNS*) pc2 = rox; *(UNS*) pc3 = sum;
if( r==1 && sign )
{
if( fseek(fp, ove, SEEK_SET) )
goto erro;
clearerr(fp);
if(f(acount, fp)==EOF || f(arox, fp)==EOF || f(asum, fp)==EOF)
{
erro:
r=0;
printf("Error in writing\n");
}
}
fclose(fp);

printf("count=%u rox=%u sum=%u\n", count, rox, sum );
printf("String=\"%s%s%s\"\nIn_num=", acount, arox, asum);
printu(acount); printf("M") ;printu(arox);printf("M");
printu(asum) ; printf("\n");
return r;
}

___________________________________


#include <string.h>
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>

#define UNS unsigned


char* estr(char* nome)
{
char *a = nome, *b;
char c;

if(nome == 0)
return 0;
while( 1 )
{
b = a;
while( (c = *a)!=0 && c!='\\' && c!='/' ) ++a;
if(c == 0) break;
++a;
}
return b;
}

int info_p(char* );

int main(int c, char** argv)
{
printf("Start \n");
if( c==0 || !argv[0] )
return 0;
if( info_p(argv[0]) == 0 )
{ printf("File corrupted\n"); return 0; }
printf("oK continue\n");
return 0;
}


void printu(char* a)
{
int i;

for( i = 0 ; i < sizeof(UNS) ; ++i)
printf(" %u ", (UNS) (unsigned char) a);
}

int f(const char* a, FILE* fp)
{
int i, j;

for( i = 0 ; i < sizeof(UNS) ; ++i)
{
if( (j = fgetc( fp ))==EOF ) return 0;
if( j != (unsigned char) a) return 0;
}
return 1;
}

char al[512] = "1234567 ";

int info_p(char* as)
{
int l, c, r, k, cp;
FILE *fp;
unsigned count = 0, rox = 0, sum = 0, *p1, buffer = 0;
char acount[ sizeof(UNS) + 8 ] = {0},
arox [ sizeof(UNS) + 8 ] = {0},
asum [ sizeof(UNS) + 8 ] = {0};
char *pc1 = acount, *pc2 = arox, *pc3 = asum;
long ove;

if(3*sizeof(UNS)>=512) return 0;
if((fp = fopen( as, "rb"))==NULL)
{
printf("Problemi di apertura\n");
return 0;
}
r = 0; cp = 0;
label:
while((c = fgetc(fp))!=EOF && !(cp=='1' && c=='2'))
{
sum += c; ++count;
cp = c;
buffer = (buffer << CHAR_BIT) | ((UNS)(unsigned char) c);
if(count % sizeof(UNS) ==0)
rox = rox ^ buffer;
}
if(c!=EOF && r==0)
{
k = 2;
while((c = fgetc(fp))!=EOF && c== ++k + '0' )
{
sum += c; ++count;
cp = c;
buffer = (buffer << CHAR_BIT) | (UNS)((unsigned char) c);
if(count % sizeof(UNS) == 0)
rox = rox ^ buffer;
} /*34567*/
if(k==8 && c!=EOF)
{
if( (ove = ftell(fp)) == -1)
{ printf( "Error\n" ); exit( 0 ); }
r = 1;
}
else if(c != EOF) goto label;
else goto fine;
while((c = fgetc(fp))!=EOF && k!=512) ++k;
if(c !=EOF ) goto label;
}
if(c == EOF) goto fine;
goto label;
fine:
*(UNS*) pc1 = count; *(UNS*) pc2 = rox; *(UNS*) pc3 = sum;
if(r == 1){
if(fseek(fp, ove, SEEK_SET) != 0)
goto labbel;
clearerr(fp);
if( f(acount, fp)==0 || f(arox, fp)==0 || f(asum, fp)==0 )
{labbel:
r = 0;
}
}
fclose(fp);
return r;
}
 
R

RoSsIaCrIiLoIA

if(f(acount, fp)==EOF || f(arox, fp)==EOF || f(asum, fp)==EOF)
{
erro:
r=0;
printf("Error in writing\n");
}
}
fclose(fp);
Click to expand...
^^^^^^^^^^^^^
if(fclose(fp)==EOF)
{
r = 0;
printf("Error\n");
}
printf("count=%u rox=%u sum=%u\n", count, rox, sum );
printf("String=\"%s%s%s\"\nIn_num=", acount, arox, asum);
printu(acount); printf("M") ;printu(arox);printf("M");
printu(asum) ; printf("\n");
return r;
}
Click to expand...
clearerr(fp);
if( f(acount, fp)==0 || f(arox, fp)==0 || f(asum, fp)==0 )
{labbel:
r = 0;
}
}
fclose(fp);
Click to expand...
^^^^^^^^^^^^^
if(fclose(fp)==EOF)
{
r = 0;
printf("Error\n");
}
 

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