What is meant by stack smashing?
Stack smashing is a form of vulnerability where the stack of a computer application or OS is forced to overflow. When the function returns, it jumps to the malicious code on the stack, which might corrupt the entire system. The adjacent data on the stack is affected and forces the program to crash.
What does a stack frame hold?
The call stack is divided up into contiguous pieces called stack frames, or frames for short; each frame is the data associated with one call to one function. The frame contains the arguments given to the function, the function’s local variables, and the address at which the function is executing.
How is a canary used to prevent stack smashing attacks?
The idea behind using a canary is that an attacker attempting to mount a stack-smashing attack will have to overwrite the canary to overwrite the control flow information. By choosing a random value for the canary, the attacker cannot know what it is and thus cannot include it in the data used to “smash” the stack.
What do you need to know about stack smashing?
Understanding the basics of stack-smashing attacks can teach admins what OSes are best protected against them and developers how to protect their programs from stack buffer overflow vulnerabilities. A memory structure used in many programming languages to store state — variable values, for instance — is known as the “stack.”
Why is stack smashing detected in runtime library?
Because the buffer can only contain 16 characters, the remaining characters will be written past its end. This is stack smashing, and undefined behavior. A number of implementations of either the runtime library or your OS may detect this situation in some conditions and terminate the program. Either you are doing something wrong or the library is.
How does a non executable stack smashing attack work?
They work by differentiating between executable stacks and non-executable stacks, so that data not intended to be executed can be stored in non-executable stack. Then, if a malicious security cracker (or a bug in your program) overwrites the end of a variable, the operating system at least won’t try to execute the malformed data.
How does stack smashing affect program control flow?
If it does, that additional data can overwrite other data stored on the stack and cause problems for other variables and program control flow. If a malicious security cracker is able to intentionally exceed the stack space allocated to a variable, he or she can use malformed data to actually affect program control flow in a deliberate way.