The document discusses different storage classes in C - automatic, register, static, and external. Automatic variables are local to the block they are defined in and don't retain their value between function calls. Register variables are stored in processor registers for faster access but the compiler decides where to store them. Static variables retain their value between function calls of the same block. External variables are visible to all translation units and their storage is allocated globally.
lFuzzer - Learning Input Tokens for Effective FuzzingBjörn Mathis
Modern fuzzing tools like AFL operate at a lexical level: They explore the input space of tested programs one byte after another. For inputs with complex syntactical properties, this is very inefficient, as keywords and other tokens have to be composed one character at a time. Fuzzers thus allow to specify dictionaries listing possible tokens the input can be composed from; such dictionaries speed up fuzzers dramatically. Also, fuzzers make use of dynamic tainting to track input tokens and infer values that are expected in the input validation phase. Unfortunately, such tokens are usually implicitly converted to program specific values which causes a loss of the taints attached to the input data in the lexical phase.
In this paper we present a technique to extend dynamic tainting to not only track explicit data flows but also taint implicitly converted data without suffering from taint explosion. This extension makes it possible to augment existing techniques and automatically infer a set of tokens and seed inputs for the input language of a program given nothing but the source code. Specifically targeting the lexical analysis of an input processor, our lFuzzer test generator systematically explores branches of the lexical analysis, producing a set of tokens that fully cover all decisions seen. The resulting set of tokens can be directly used as a dictionary for fuzzing. Along with the token extraction seed inputs are generated which give further fuzzing processes a head start. In our experiments, the lFuzzer-AFL combination achieves up to 17% more coverage on complex input formats like JSON, LISP, tinyC, and JavaScript compared to AFL.
lFuzzer - Learning Input Tokens for Effective FuzzingBjörn Mathis
Modern fuzzing tools like AFL operate at a lexical level: They explore the input space of tested programs one byte after another. For inputs with complex syntactical properties, this is very inefficient, as keywords and other tokens have to be composed one character at a time. Fuzzers thus allow to specify dictionaries listing possible tokens the input can be composed from; such dictionaries speed up fuzzers dramatically. Also, fuzzers make use of dynamic tainting to track input tokens and infer values that are expected in the input validation phase. Unfortunately, such tokens are usually implicitly converted to program specific values which causes a loss of the taints attached to the input data in the lexical phase.
In this paper we present a technique to extend dynamic tainting to not only track explicit data flows but also taint implicitly converted data without suffering from taint explosion. This extension makes it possible to augment existing techniques and automatically infer a set of tokens and seed inputs for the input language of a program given nothing but the source code. Specifically targeting the lexical analysis of an input processor, our lFuzzer test generator systematically explores branches of the lexical analysis, producing a set of tokens that fully cover all decisions seen. The resulting set of tokens can be directly used as a dictionary for fuzzing. Along with the token extraction seed inputs are generated which give further fuzzing processes a head start. In our experiments, the lFuzzer-AFL combination achieves up to 17% more coverage on complex input formats like JSON, LISP, tinyC, and JavaScript compared to AFL.
As a global leader in WordPress backups and security, our job involves receiving mails from distraught customers who have been hacked. Maintaining a completely secure WordPress site isn't practical, but there are ways to make things harder for hackers. Here are a few essential practices to follow to harden your WordPress site's security.
State of WordPress Security: Today and BeyondBlogVault Inc
There is concern about WordPress security. However, WordPress core itself is very secure. On the other hand, with WP growing in popularity it is natural to see a rise in security concern as well. Of course, there is not such thing as a perfectly secure CMS. It is up to the community to stay informed, and act according to best practices to fend off security concerns.
Pearls for Tackling canalicular injuries of Lacrimal Apparatus Presentation b...Dr Suresh Pandey
Pearls for Tackling canalicular injuries of Lacrimal Apparatus Presentation by dr vidushi sharma dr suresh k pandey suvi eye institute kota india (email:suvieye@gmail.com)
It is an attempt to make the students of IT understand the basics of programming in C in a simple and easy way. Send your feedback for rectification/further development.
1. Static Storage Class
Storage
Default Initial Value
Scope
Life
Memory
0
Local to the block in which
the variable is defined
Variable persists between
different function calls
2. main( )
{
increment( ) ;
increment( ) ;
increment( ) ;
}
increment( )
{
auto int i = 1 ;
register int j = 1 ;
static int k = 1 ;
i++ ;
j++ ; k++ ;
printf ( ”%d %d %d”, i, j, k ) ;
2 2 2
2 2 3
2 2 4
}
3. When to Use Static
main( )
{
f( )
f( ) ;
p =
int a = 20 ;
return ( &a ) ;
}
printf ( ”%d”, *p ) ;
}
int *p ; int * f( ) ;
{
a p
20 250
250
int * f( ) char ** char ** ff (( iinntt **,, ffllooaatt ** )) ;;
static int a = 20 ;
4. External Storage Class
main( )
{
printf ( ”%d”, a ) ;
increment( ) ;
increment( ) ;
decrement( ) ;
printf ( ”%d”, a ) ;
}
increment( )
{
a++ ; printf ( ”%d”, a ) ;
} decrement( )
{
a-- ; printf ( ”%d”, a ) ;
}
10
11
12
11
11
int a = 10 ;
Output
5. Declaration V/s Definition main( )
{
extern int a ;
printf ( ”%d”, a ) ;
increment( ) ;
increment( ) ;
decrement( ) ;
printf ( ”%d”, a ) ;
ncrement( )
{
extern int a ;
float square ( float ) ;
float square ( float )
{
..
..
}
DDeeccllaarraattiioonn
} a++ ; printf ( ”%d”, a ) ;
decrement( )
{
extern int a ;
} a-- ; printf ( ”%d”, a ) ;
}i
int a = 10 ;
DDeeccllaarraattiioonn
DDeeccllaarraattiioonn
DDeeffiinniittiioonn
float square ( float ) ;
float square ( float )
{
..
..
}
DDeeffiinniittiioonn
6. Declaration V/s Definition main( )
{
extern int a ;
printf ( ”%d”, a ) ;
increment( ) ;
increment( ) ;
decrement( ) ;
printf ( ”%d”, a ) ;
extern int a ;
int a = 10 ;
decrement( )
{
extern int a ;
}i
ncrement( )
{
a++ ; printf ( ”%d”, a ) ;
}
a-- ; printf ( ”%d”, a ) ;
}
7. Declaration V/s Definition main( )
{
extern int a ;
printf ( ”%d”, a ) ;
increment( ) ;
increment( ) ;
decrement( ) ;
printf ( ”%d”, a ) ;
int a = 10 ;
increment( )
{
extern int a ;
decrement( )
{
extern int a ;
}
a++ ; printf ( ”%d”, a ) ;
}
a-- ; printf ( ”%d”, a ) ;
}
8. Two Types Of Conflicts
int a = 10 ;
main( )
{
int a = 20 ;
{
int a = 30 ;
printf ( ”%d”, a ) ;
}
printf ( ”%d”, a ) ;
}
printf ( ”%d”, a ) ;
30
20
9. External Storage Class
Storage
Default Initial Value
Scope
Life
Memory
0
Global
Till execution of the
program doesn’t end
10. Which is The Most Powerful
Automatic
Register
Static
External
All other cases
For frequently
used variables
If variable is to live
across function calls
If variable required by
all functions
11. Ctrl F9
F9
F7
F8
C Preprocessor
Compile and Execute
Compile
Step into
Step over
13. A Closer Look
Hand written program
Text Editor
C Source Code
Preprocessor
Expanded source code
Compiler
Object code
Linker
Executable code
C :
Helps in typing TC
WS4 . .
a program
WORKS
Helps in typing
a program
Expands the
source code
Expands the
source code
Converts expanded source
code into machine language
Converts expanded source
code into machine language
14. Why IDE
Editor
Preprocessor
Compiler
Linker
Ctrl F9
TTuurrbboo CC//CC++++
Preprocesses,
Compiles, Links
and Executes
17. Unresolved
Externals
gotorc( - , - )
{
-
-
-
} Compiler
main( )
{
-
-
-
}
machine language
code of gotorc( )
machine language
code of main( )
Error Why?
18. Solution
m/c language code
of gotorc( )
m/c language code
of main( )
m/c language code
of clrscr( )
m/c language code
of printf( )
LLiinnkkeerr
Executable code
19. Your wish
# include ”goto.c”
# include goto.c
C :
TC
WS4 . .
WORKS
INCLUDE
INCLUDE DIRECTORIES
LIBRARY DIRECTORIES
C: TC INCLUDE
C: TC LIB
C: TC WORKS
C: TC
OUTPUT DIRECTORY
SOURCE DIRECTORIES