first call getRandoms in pruduce some random number stored in stack. after that we can read 7 bytes from the area where originally points to the random number. this problem though has a stack overflow in the end but has canary, so we need to figure out a wey to bypass it. the key point is that after getRandoms return back, the memory area of random number will be replaced by canary. so at here we can get canary to bypass it.another question we need to figure out is how to build rop without '0a090b200d'. for if there exsit those bytes, the scanf will cut down the input, and the got and plt address contain those bytes. what we do is use ROPgadget with ROPgadget --binary Random_Generator --badbytes '0a090b200d'. we get a gadget 0x0000000000400f8f : syscall ; ret so we can do rop with this particular gadget and get a shell.
ROP and NX question
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Most of the vulnerability elements mentioned in prior attack models are still leveraged today in the ROP attack model. Modern systems attempt to mitigate this by separating data and code by memory (or page) attributes. This separation means that an essential step for a successful attack to occur is to transform data input into byte-executable code. To do so, a page attribute change has to happen; for example, a system call should be executed under privileged mode. That raises the question of how to convert input data into such a system call?
This article aims to explain clearly what ROP or Return Oriented Programming is. What is this technique? Why is it useful? What are the limits? How to implement it? We will answer these questions together.
Surely, to assume the presence of a loaded PE with SafeSEH disabled in a modern application defeats the purpose of this text, considering that SafeSEH has been enabled by default in Visual Studio since 2005? While exploring this question for myself, I wrote a PE file scanner tool able to identify the presence (or lack thereof) of exploit mitigations on a per-file basis system-wide. The results, after pointing this scanner at the SysWOW64 folder on my Windows 10 VM (and filtering for non-SafeSEH PEs) were quite surprising.
MSVC has removed the stack cookie from the function. MSVC has also placed the Buf array in the lowest region of memory, going against its typical security policy; it will not consider a GS buffer for its security reordering if the buffer is unreferenced. Thus an interesting question is posed: what constitutes a reference? Surprisingly, the answer is not what we might expect (that a reference is simply any use of a variable within the function). Some types of variable usages do not count as references and thus do not affect variable ordering.
The vulnerability in question is caused by a buffer overflow due to unsanitised user input being passed directly to a call to sscanf. The figure below shows the vulnerable code in the R7WebsSecurityHandler function of the HTTPD binary for the device.
A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix. Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:
In answer to a question, Cook said that the forward-edge CFI protectionworks fine with retpolines (whichis a Spectre mitigation), but he turned them off for his examples as itjust complicates the picture. Hardware-based forward-edge CFI might makeretpolines impossible, but he is hopeful that retpolines will becomeunnecessary well before some new scheme for CFI makes its appearance.While ROP attacks target places other than function entry, most otherattacks are calling functions "normally", so the restriction that isprovided by today's hardware CFI is not terribly useful, he said. 2ff7e9595c
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