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Wladimir J. van der Laan 4631dc5c57
Merge #18921: build: add stack-clash and control-flow protection options to hardening flags 
b536813cef build: add -fstack-clash-protection to hardening flags (fanquake)
076183b36b 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 b536813cef ([`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 b536813cef

Tree-SHA512: abc9adf23cdf1be384f5fb9aa5bfffdda86b9ecd671064298d4cda0440828b509f070f9b19c88c7ce50ead9ff32afff9f14c5e78d75f01241568fbfa077be0b7
2020-08-29 13:42:04 +02:00
.github doc: Remove label from good first issue template 2020-08-24 09:31:24 +02:00
.tx tx: Bump transifex slug to 020x 2020-03-16 10:52:55 +01:00
build-aux/m4 Merge #17396: build: modest Android improvements 2020-08-24 21:27:29 +08:00
build_msvc Move Win32 defines to configure.ac to ensure they are globally defined 2020-08-20 17:55:06 +00:00
ci ci: Set increased --timeout-factor by default 2020-08-15 09:24:46 +02:00
contrib Merge #19622: build: Drop ancient hack in gitian-linux descriptor 2020-08-10 20:15:09 +08:00
depends build: replace wingenminiupnpcstrings sed with a patch in miniupnpc package 2020-08-26 11:27:31 +08:00
doc Merge #19628: net: change CNetAddr::ip to have flexible size 2020-08-25 18:10:25 +02:00
share doc: Use precise permission flags where possible 2020-07-10 15:37:42 +02:00
src Merge #18817: doc: Document differences in bitcoind and bitcoin-qt locale handling 2020-08-29 10:03:45 +02:00
test Merge #18817: doc: Document differences in bitcoind and bitcoin-qt locale handling 2020-08-29 10:03:45 +02:00
.appveyor.yml Merge #18011: Replace current benchmarking framework with nanobench 2020-07-30 15:34:17 +02:00
.cirrus.yml ci: Set cirrus RAM to 8GB 2020-08-17 11:53:31 +02:00
.fuzzbuzz.yml ci: Add fuzzbuzz integration 2020-04-14 16:38:26 +00:00
.gitattributes Separate protocol versioning from clientversion 2014-10-29 00:24:40 -04:00
.gitignore build: Add missed fuzz.coverage/ directory to .gitignore 2020-08-08 23:52:18 +03:00
.python-version .python-version: Specify full version 3.5.6 2019-03-02 12:06:26 -05:00
.style.yapf test: .style.yapf: Set column_limit=160 2019-03-04 18:28:13 -05:00
.travis.yml ci: Run valgrind fuzzer on cirrus 2020-08-17 11:52:02 +02:00
autogen.sh scripted-diff: Bump copyright of files changed in 2019 2019-12-30 10:42:20 +13:00
configure.ac Merge #18921: build: add stack-clash and control-flow protection options to hardening flags 2020-08-29 13:42:04 +02:00
CONTRIBUTING.md Replace hidden service with onion service 2020-08-07 14:55:02 +02:00
COPYING doc: Update license year range to 2020 2019-12-26 23:11:21 +01:00
INSTALL.md Update INSTALL landing redirection notice for build instructions. 2016-10-06 12:27:23 +13:00
libbitcoinconsensus.pc.in build: remove libcrypto as internal dependency in libbitcoinconsensus.pc 2019-11-19 15:03:44 +01:00
Makefile.am build: Add missed fuzz_filtered.info to COVERAGE_INFO 2020-08-08 23:38:14 +03:00
README.md doc: Mention repo split in the READMEs 2020-06-08 10:06:14 -04:00
SECURITY.md doc: Remove explicit mention of version from SECURITY.md 2019-06-14 06:39:17 -04:00

README.md

Bitcoin Core integration/staging tree

https://bitcoincore.org

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.