4631dc5c57
b536813cefc13f5c54a28a7c2fce8c69e89d6624 build: add -fstack-clash-protection to hardening flags (fanquake) 076183b36b76a11438463883ff916f17aef9e001 build: add -fcf-protection=full to hardening options (fanquake) Pull request description: Beginning with Ubuntu `19.10`, it's packaged GCC now has some additional hardening options enabled by default (in addition to existing defaults like `-fstack-protector-strong` and reducing the minimum ssp buffer size). The new additions are`-fcf-protection=full` and `-fstack-clash-protection`. > -fcf-protection=[full|branch|return|none] > Enable code instrumentation of control-flow transfers to increase program security by checking that target addresses of control-flow transfer instructions (such as indirect function call, function return, indirect jump) are valid. This prevents diverting the flow of control to an unexpected target. This is intended to protect against such threats as Return-oriented Programming (ROP), and similarly call/jmp-oriented programming (COP/JOP). > -fstack-clash-protection > Generate code to prevent stack clash style attacks. When this option is enabled, the compiler will only allocate one page of stack space at a time and each page is accessed immediately after allocation. Thus, it prevents allocations from jumping over any stack guard page provided by the operating system. If your interested you can grab `gcc-9_9.3.0-10ubuntu2.debian.tar.xz` from https://packages.ubuntu.com/focal/g++-9. The relevant changes are part of the `gcc-distro-specs` patches, along with the relevant additions to the gcc manages: > NOTE: In Ubuntu 19.10 and later versions, -fcf-protection is enabled by default for C, C++, ObjC, ObjC++, if none of -fno-cf-protection nor -fcf-protection=* are found. > NOTE: In Ubuntu 19.10 and later versions, -fstack-clash-protection is enabled by default for C, C++, ObjC, ObjC++, unless -fno-stack-clash-protection is found. So, if you're C++ using GCC on Ubuntu 19.10 or later, these options will be active unless you explicitly opt out. This can be observed with a small test: ```c++ int main() { return 0; } ``` ```bash g++ --version g++ (Ubuntu 9.3.0-10ubuntu2) 9.3.0 g++ test.cpp objdump -dC a.out .. 0000000000001129 <main>: 1129: f3 0f 1e fa endbr64 112d: 55 push %rbp 112e: 48 89 e5 mov %rsp,%rbp 1131: b8 00 00 00 00 mov $0x0,%eax 1136: 5d pop %rbp 1137: c3 retq 1138: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1) 113f: 00 # recompile opting out of control flow protection g++ test.cpp -fcf-protection=none objdump -dC a.out ... 0000000000001129 <main>: 1129: 55 push %rbp 112a: 48 89 e5 mov %rsp,%rbp 112d: b8 00 00 00 00 mov $0x0,%eax 1132: 5d pop %rbp 1133: c3 retq 1134: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1) 113b: 00 00 00 113e: 66 90 xchg %ax,%ax ``` Note the insertion of an `endbr64` instruction when compiling and _not_ opting out. This instruction is part of the Intel Control-flow Enforcement Technology [spec](https://software.intel.com/sites/default/files/managed/4d/2a/control-flow-enforcement-technology-preview.pdf), which the GCC control flow implementation is based on. If we're still doing gitian builds for the `0.21.0` and `0.22.0` releases, we'd likely update the gitian image to Ubuntu Focal, which would mean that the GCC used for gitian builds would also be using these options by default. So we should decide whether we want to explicitly turn these options on as part of our hardening options (although not just for this reason), or, we should be opting-out. GCC has supported both options since 8.0.0. Clang has supported `-fcf-protection` from 7.0.0 and will support `-fstack-clash-protection` in it's upcoming [11.0.0 release](https://clang.llvm.org/docs/ReleaseNotes.html#id6). ACKs for top commit: jamesob: ACK b536813cefc13f5c54a28a7c2fce8c69e89d6624 ([`jamesob/ackr/18921.1.fanquake.build_add_stack_clash_an`](https://github.com/jamesob/bitcoin/tree/ackr/18921.1.fanquake.build_add_stack_clash_an)) laanwj: Code review ACK b536813cefc13f5c54a28a7c2fce8c69e89d6624 Tree-SHA512: abc9adf23cdf1be384f5fb9aa5bfffdda86b9ecd671064298d4cda0440828b509f070f9b19c88c7ce50ead9ff32afff9f14c5e78d75f01241568fbfa077be0b7
Bitcoin Core integration/staging tree
What is Bitcoin?
Bitcoin is an experimental digital currency that enables instant payments to anyone, anywhere in the world. Bitcoin uses peer-to-peer technology to operate with no central authority: managing transactions and issuing money are carried out collectively by the network. Bitcoin Core is the name of open source software which enables the use of this currency.
For more information, as well as an immediately usable, binary version of the Bitcoin Core software, see https://bitcoincore.org/en/download/, or read the original whitepaper.
License
Bitcoin Core is released under the terms of the MIT license. See COPYING for more information or see https://opensource.org/licenses/MIT.
Development Process
The master branch is regularly built (see doc/build-*.md for instructions) and tested, but it is not guaranteed to be
completely stable. Tags are created
regularly from release branches to indicate new official, stable release versions of Bitcoin Core.
The https://github.com/bitcoin-core/gui repository is used exclusively for the development of the GUI. Its master branch is identical in all monotree repositories. Release branches and tags do not exist, so please do not fork that repository unless it is for development reasons.
The contribution workflow is described in CONTRIBUTING.md and useful hints for developers can be found in doc/developer-notes.md.
Testing
Testing and code review is the bottleneck for development; we get more pull requests than we can review and test on short notice. Please be patient and help out by testing other people's pull requests, and remember this is a security-critical project where any mistake might cost people lots of money.
Automated Testing
Developers are strongly encouraged to write unit tests for new code, and to
submit new unit tests for old code. Unit tests can be compiled and run
(assuming they weren't disabled in configure) with: make check. Further details on running
and extending unit tests can be found in /src/test/README.md.
There are also regression and integration tests, written
in Python, that are run automatically on the build server.
These tests can be run (if the test dependencies are installed) with: test/functional/test_runner.py
The Travis CI system makes sure that every pull request is built for Windows, Linux, and macOS, and that unit/sanity tests are run automatically.
Manual Quality Assurance (QA) Testing
Changes should be tested by somebody other than the developer who wrote the code. This is especially important for large or high-risk changes. It is useful to add a test plan to the pull request description if testing the changes is not straightforward.
Translations
Changes to translations as well as new translations can be submitted to Bitcoin Core's Transifex page.
Translations are periodically pulled from Transifex and merged into the git repository. See the translation process for details on how this works.
Important: We do not accept translation changes as GitHub pull requests because the next pull from Transifex would automatically overwrite them again.
Translators should also subscribe to the mailing list.