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i=1;
manipulate(buffer);
i=2;
printf("The value of i is : %d\n",i);
return 0;
}
while ((buffer[i++] = getchar()) != '\n') {};
#include <stdio.h>
A race condition is anomalous behavior caused by the unexpected dependence on the relative timing of events. In other words, a programmer incorrectly assumed that a particular event would always happen before another.
A superuser process within a jailed environment has the power to:
Although stack-based attacks are by far the most common, it would also be possible to overrun the stack with a heap-based (malloc/free) attack.
An application should never assume that anything about the users environment is sane. This includes (but is certainly not limited to): user input, signals, environment variables, resources, IPC, mmaps, the filesystem working directory, file descriptors, the # of open files, etc.
Another memory copy implementation exists to get around these problems. The `strlcpy` and `strlcat` functions guarantee that they will always null terminate the destination string when given a non-zero length argument.
Avoiding Buffer Overflows
Bind to privileged ports in the Internet domain (ports < 1024)
Buffer Overflows
Buffer Overflows have been around since the very beginnings of the von Neumann <<cod,1>> architecture. They first gained widespread notoriety in 1988 with the Morris Internet worm. Unfortunately, the same basic attack remains effective today. By far the most common type of buffer overflow attack is based on corrupting the stack.
Chapter 3. Secure Programming
Compiler based run-time bounds checking
Compiler-based mechanisms are completely useless for binary-only software for which you cannot recompile. For these situations there are a number of libraries which re-implement the unsafe functions of the C-library (`strcpy`, `fscanf`, `getwd`, etc..) and ensure that these functions can never write past the stack pointer.
Example Buffer Overflow
FreeBSD's jail functionality
Let us examine what the memory image of this process would look like if we were to input 160 spaces into our little program before hitting return.
Library based run-time bounds checking
Limiting your program's environment