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Questions tagged [libc]

C standard library for the C programming language as specified in the C specification (ANSI C, C99, C11, ...).

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How can I intercept syscall libc function in C++ without writing any code in C file

How can intercept libc function in C++ using LD_PRELOAD. I want to write code only in C++ file and all the logic of symbol fishing (dlsym) must be in C++ file. Please give an example.
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`dmi libc puts~GLOBAL` does not show puts, just putspent?

On the tutorial by Megabeets, "A journey into Radare 2 – Part 2: Exploitation" [0x080483d0]> dmi libc puts~&GLOBAL, puts:0 532 0x000fdd60 0xf7e0bd60 GLOBAL FUNC 1181 putspent [0x080483d0]&...
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1answer
88 views

Found the adress of a function LIBC without GDB

How to calculate the address of a function in the LIBC, when ASLR is not active. I only have the address where to load the LIBC (with ldd /bin/bash). Thank you for the explanations EDIT: When I use ...
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1answer
56 views

Why is j_free function and free_ptr pointer needed in glibc?

I am disassembling libc-2.23.so, there exists a thunk method called j_free which jumps at the location pointed to by free_ptr pointer in glibc. Why do those even exist while free() itself is exported?
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2answers
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How does glibc malloc work?

Wishing to dig in the internals of dynamic memory allocation on Linux, the best I could find is an article titled Understanding glibc malloc. The explanation, though detailed, is not quite ...
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2answers
1k views

Recognizing CLib functions in Ollydbg or IDA

I'm just learning Olly/IDA and writing simple programs in C and looking at the .EXE code in Ollydbg and IDA. Below I have a simple printf Hello World program which I compile in Visual Studio 6. I ...
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1answer
118 views

Exploitability of Stack-based Buffer Overflows on functions ending with fclose()

I have been discussing the effectiveness of GNU libc's fclose() function to thwart successful exploitation of trivial vulnerabilities due to segmentation fault when called without a valid pointer to a ...
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0answers
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dlmalloc free pointers

I was looking at the implementation of "free" in my current dlmalloc(both the source and the disassembly). However, I could not find the code section the inserts the FD and BK into free chunks. What ...