chriseth

Answers to Deep Questions about Solidity

The following list of questions was taken from https://www.reddit.com/r/ethereum/comments/72reba/do_you_have_deep_questions_about_solidity_or_the/

An updated summary on the different ways one could have two contracts interact (DELEGATECALL, STATICCALL, libraries, all that stuff) with clear pros/cons for each (gas cost, whether it requires EVM assembly directives, etc)

Question by /u/drcode

I won't talk about low-level opcodes here because of the brevity of the answer. In general, there are four ways functions can be called in Solidity:

Siguza

Sadly I don't have a dev device on iOS 10, but for anyone playing around with zIVA caring about the kernel task port:

Starting with iOS 10.3 (and macOS 10.12.4), Apple changed convert_port_to_locked_task (and a few other port-to-something conversion functions) to blacklist the kernel task by means of a direct check. As a result, you can still obtain the kernel task port, but almost all APIs will simply treat it like MACH_PORT_NULL, thus rendering it useless. The check is a simple pointer comparison though, so it can be circumvented by just remapping the task struct at an additional virtual address and creating a new port from that with a ROP equivalent of:

vm_map_remap(
    kernel_map,
    &remap_addr,
    sizeof(task_t),
    0,

VM_FLAGS_ANYWHERE | VM_FLAGS_RETURN_DATA_ADDR,

williballenthin

'''
example of:
  - using ctypes with the IDA SDK
  - providing custom UI hints with dynamic data from Python

in this silly example, we display UI hints with the current timestamp.
a more useful plugin might inspect the hovered line, and display some documentation.

Author: Willi Ballenthin <william.ballenthin@fireeye.com>
Licence: Apache 2.0

pakt

#
# read/write access to python's memory, using a custom bytearray.
# some code taken from: http://tinyurl.com/q7duzxj
#
# tested on:
# Python 2.7.10, ubuntu 32bit
# Python 2.7.8, win32
#
# example of correct output:
# inspecting int=0x41424344, at 0x0228f898

yamaya

# Xcode 4.3.3
Apple clang version 3.1 (tags/Apple/clang-318.0.61) (based on LLVM 3.1svn)
Target: x86_64-apple-darwin11.4.0
Thread model: posix

# Xcode 4.3.2
Apple clang version 3.1 (tags/Apple/clang-318.0.58) (based on LLVM 3.1svn)
Target: x86_64-apple-darwin11.4.0
Thread model: posix