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patch 9.0.2121: [security]: use-after-free in ex_substitute Commit: https://github.com/vim/vim/commit/26c11c56888d01e298cd8044caf860f3c26f57bb Author: Christian Brabandt <cb@256bit.org> Date: Wed Nov 22 21:26:41 2023 +0100 patch 9.0.2121: [security]: use-after-free in ex_substitute Problem: [security]: use-after-free in ex_substitute Solution: always allocate memory closes: #13552 A recursive :substitute command could cause a heap-use-after free in Vim (CVE-2023-48706). The whole reproducible test is a bit tricky, I can only reproduce this reliably when no previous substitution command has been used yet (which is the reason, the test needs to run as first one in the test_substitute.vim file) and as a combination of the `:~` command together with a :s command that contains the special substitution atom `~\=` which will make use of a sub-replace special atom and calls a vim script function. There was a comment in the existing :s code, that already makes the `sub` variable allocate memory so that a recursive :s call won't be able to cause any issues here, so this was known as a potential problem already. But for the current test-case that one does not work, because the substitution does not start with `\=` but with `~\=` (and since there does not yet exist a previous substitution atom, Vim will simply increment the `sub` pointer (which then was not allocated dynamically) and later one happily use a sub-replace special expression (which could then free the `sub` var). The following commit fixes this, by making the sub var always using allocated memory, which also means we need to free the pointer whenever we leave the function. Since sub is now always an allocated variable, we also do no longer need the sub_copy variable anymore, since this one was used to indicated when sub pointed to allocated memory (and had therefore to be freed on exit) and when not. Github Security Advisory: https://github.com/vim/vim/security/advisories/GHSA-c8qm-x72m-q53q Signed-off-by: Christian Brabandt <cb@256bit.org>
author Christian Brabandt <cb@256bit.org>
date Wed, 22 Nov 2023 22:15:05 +0100
parents dbec60b8c253
children
line wrap: on
line source

" Tests for expand()

source shared.vim

let s:sfile = expand('<sfile>')
let s:slnum = str2nr(expand('<slnum>'))
let s:sflnum = str2nr(expand('<sflnum>'))

func s:expand_sfile()
  return expand('<sfile>')
endfunc

func s:expand_slnum()
  return str2nr(expand('<slnum>'))
endfunc

func s:expand_sflnum()
  return str2nr(expand('<sflnum>'))
endfunc

" This test depends on the location in the test file, put it first.
func Test_expand_sflnum()
  call assert_equal(7, s:sflnum)
  call assert_equal(24, str2nr(expand('<sflnum>')))

  " Line-continuation
  call assert_equal(
        \ 27,
        \ str2nr(expand('<sflnum>')))

  " Call in script-local function
  call assert_equal(18, s:expand_sflnum())

  " Call in command
  command Flnum echo expand('<sflnum>')
  call assert_equal(36, str2nr(trim(execute('Flnum'))))
  delcommand Flnum
endfunc

func Test_expand_sfile_and_stack()
  call assert_match('test_expand_func\.vim$', s:sfile)
  let expected = 'script .*testdir/runtest.vim\[\d\+\]\.\.function RunTheTest\[\d\+\]\.\.Test_expand_sfile_and_stack'
  call assert_match(expected .. '$', expand('<sfile>'))
  call assert_match(expected .. '\[4\]$' , expand('<stack>'))

  " Call in script-local function
  call assert_match('script .*testdir/runtest.vim\[\d\+\]\.\.function RunTheTest\[\d\+\]\.\.Test_expand_sfile_and_stack\[7\]\.\.<SNR>\d\+_expand_sfile$', s:expand_sfile())

  " Call in command
  command Sfile echo expand('<sfile>')
  call assert_match('script .*testdir/runtest.vim\[\d\+\]\.\.function RunTheTest\[\d\+\]\.\.Test_expand_sfile_and_stack$', trim(execute('Sfile')))
  delcommand Sfile

  " Use <stack> from sourced script.
  let lines =<< trim END
    " comment here
    let g:stack_value = expand('<stack>')
  END
  call writefile(lines, 'Xstack', 'D')
  source Xstack
  call assert_match('\<Xstack\[2\]$', g:stack_value)
  unlet g:stack_value

  if exists('+shellslash')
    call mkdir('Xshellslash', 'R')
    let lines =<< trim END
      let g:stack1 = expand('<stack>')
      set noshellslash
      let g:stack2 = expand('<stack>')
      set shellslash
      let g:stack3 = expand('<stack>')
    END
    call writefile(lines, 'Xshellslash/Xstack')
    " Test that changing 'shellslash' always affects the result of expand()
    " when sourcing a script multiple times.
    for i in range(2)
      source Xshellslash/Xstack
      call assert_match('\<Xshellslash/Xstack\[1\]$', g:stack1)
      call assert_match('\<Xshellslash\\Xstack\[3\]$', g:stack2)
      call assert_match('\<Xshellslash/Xstack\[5\]$', g:stack3)
      unlet g:stack1
      unlet g:stack2
      unlet g:stack3
    endfor
  endif
endfunc

func Test_expand_slnum()
  call assert_equal(6, s:slnum)
  call assert_equal(2, str2nr(expand('<slnum>')))

  " Line-continuation
  call assert_equal(
        \ 5,
        \ str2nr(expand('<slnum>')))

  " Call in script-local function
  call assert_equal(1, s:expand_slnum())

  " Call in command
  command Slnum echo expand('<slnum>')
  call assert_equal(14, str2nr(trim(execute('Slnum'))))
  delcommand Slnum
endfunc

func Test_expand()
  new
  call assert_equal("", expand('%:S'))
  call assert_equal('3', '<slnum>'->expand())
  call assert_equal(['4'], expand('<slnum>', v:false, v:true))
  " Don't add any line above this, otherwise <slnum> will change.
  call assert_equal("", expand('%'))
  set verbose=1
  call assert_equal("", expand('%'))
  set verbose=0
  call assert_equal("", expand('%:p'))
  quit
endfunc

func s:sid_test()
  return 'works'
endfunc

func Test_expand_SID()
  let sid = expand('<SID>')
  execute 'let g:sid_result = ' .. sid .. 'sid_test()'
  call assert_equal('works', g:sid_result)
endfunc


" Test for 'wildignore' with expand()
func Test_expand_wildignore()
  set wildignore=*.vim
  call assert_equal('', expand('test_expand_func.vim'))
  call assert_equal('', expand('test_expand_func.vim', 0))
  call assert_equal([], expand('test_expand_func.vim', 0, 1))
  call assert_equal('test_expand_func.vim', expand('test_expand_func.vim', 1))
  call assert_equal(['test_expand_func.vim'],
        \ expand('test_expand_func.vim', 1, 1))
  call assert_fails("call expand('*', [])", 'E745:')
  set wildignore&
endfunc

" vim: shiftwidth=2 sts=2 expandtab