Vector35 / Vector35/debugger

Step return lets x86 target run freely if the first instruction after the return is `jmp`

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#421 3 comments 0 reactions 0 assignees View on GitHub

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bug DbgEng Adapter functionality Impact: Medium
Dominant language
C++
Stars
331
Forks
33
PR merge metrics
No merged PRs in 30d

Description

For the following code,

_start:
004012d5  call    ___security_init_cookie
004012da  jmp     sub_401153

If I step into the function ___security_init_cookie, and then hit step return, the target will run freely, as if I send a Go command. There are several requirements for this issue:

  1. It must be an x86 binary
  2. The first instruction on the return address is an jmp

Note, this is actually a windbg bug -- that I can reproduce it directly in windbg.

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the issue with the shown x86 call/jmp sequence by stepping into ___security_init_cookie and using step return. Trace the x86 step-return handling and compare its behavior with WinDbg. Done means step return stops at the expected return location instead of running freely when that location begins with jmp.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
devtools, reverse-engineering
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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