400f45ec9b
65d0f1a53354fb25c8152ee5b430cf57e6508594 devtools: Add security check for separate_code (Wladimir J. van der Laan) 2e9e6377f10ab1ca5021f6ec964d22161469ba60 build: add -Wl,-z,separate-code to hardening flags (fanquake) Pull request description: TLDR: We are generally explicit about the hardening related flags we use, rather than letting the distro / toolchain decide via their defaults. This PR adds `-z,separate-code` which has been enabled by default for Linux targets since binutils 2.31. Ubuntu Bionic (currently used for gitian) ships with binutils 2.30, so this will enable the option for those builds. This flag was added to binutils/ld in the 2.30 release, see commit c11c786f0b45617bb8807ab6a57220d5ff50e414: > The new "-z separate-code" option will generate separate code LOAD segment which must be in wholly disjoint pages from any other data. It was made the default for Linux/x86 targets in the 2.31 release, see commit f6aec96dce1ddbd8961a3aa8a2925db2021719bb: > This patch adds --enable-separate-code to ld configure to turn on -z separate-code by default and enables it by default for Linux/x86. This avoids mixing code pages with data to improve cache performance as well as security. > To reduce x86-64 executable and shared object sizes, the maximum page size is reduced from 2MB to 4KB when -z separate-code is turned on by default. Note: -z max-page-size= can be used to set the maximum page size. > We compared SPEC CPU 2017 performance before and after this change on Skylake server. There are no any significant performance changes. Everything is mostly below +/-1%. Support was also added to LLVMs lld: https://reviews.llvm.org/D64903, however there it remains off by default. There were concerns about an increase in binary size, however in our case, the difference would seem negligible, given we are shipping a multi-megabyte binary, which then downloads 100's of GBs of data. Also note that most recent versions of distros are shipping a new enough version of binutils that this is available and/or already on by default (assuming the distro has not turned it off, I haven't checked everywhere): CentOS 8: 2.30 Debian Buster 2.31.1 Fedora 29: 2.31.1 FreeBSD: 2.33 GNU Guix: 2.33 / 2.34 Ubuntu 18.04: 2.30 Related threads / discussion: https://bugzilla.redhat.com/show_bug.cgi?id=1623218 The ELF header when building on Debian Buster (where it's already enabled by default in binutils): ```bash Program Header: PHDR off 0x0000000000000040 vaddr 0x0000000000000040 paddr 0x0000000000000040 align 2**3 filesz 0x00000000000002a0 memsz 0x00000000000002a0 flags r-- INTERP off 0x00000000000002e0 vaddr 0x00000000000002e0 paddr 0x00000000000002e0 align 2**0 filesz 0x000000000000001c memsz 0x000000000000001c flags r-- LOAD off 0x0000000000000000 vaddr 0x0000000000000000 paddr 0x0000000000000000 align 2**12 filesz 0x0000000000038f10 memsz 0x0000000000038f10 flags r-- LOAD off 0x0000000000039000 vaddr 0x0000000000039000 paddr 0x0000000000039000 align 2**12 filesz 0x00000000006b9389 memsz 0x00000000006b9389 flags r-x LOAD off 0x00000000006f3000 vaddr 0x00000000006f3000 paddr 0x00000000006f3000 align 2**12 filesz 0x0000000000204847 memsz 0x0000000000204847 flags r-- LOAD off 0x00000000008f7920 vaddr 0x00000000008f8920 paddr 0x00000000008f8920 align 2**12 filesz 0x00000000000183e0 memsz 0x0000000000022fd0 flags rw- DYNAMIC off 0x000000000090adb0 vaddr 0x000000000090bdb0 paddr 0x000000000090bdb0 align 2**3 filesz 0x0000000000000240 memsz 0x0000000000000240 flags rw- ``` vs when opting out using `-Wl,-z,noseparate-code`: ```bash Program Header: PHDR off 0x0000000000000040 vaddr 0x0000000000000040 paddr 0x0000000000000040 align 2**3 filesz 0x0000000000000230 memsz 0x0000000000000230 flags r-- INTERP off 0x0000000000000270 vaddr 0x0000000000000270 paddr 0x0000000000000270 align 2**0 filesz 0x000000000000001c memsz 0x000000000000001c flags r-- LOAD off 0x0000000000000000 vaddr 0x0000000000000000 paddr 0x0000000000000000 align 2**12 filesz 0x00000000008f6a87 memsz 0x00000000008f6a87 flags r-x LOAD off 0x00000000008f7920 vaddr 0x00000000008f8920 paddr 0x00000000008f8920 align 2**12 filesz 0x00000000000183e0 memsz 0x0000000000022fd0 flags rw- DYNAMIC off 0x000000000090adb0 vaddr 0x000000000090bdb0 paddr 0x000000000090bdb0 align 2**3 filesz 0x0000000000000240 memsz 0x0000000000000240 flags rw- ``` ACKs for top commit: laanwj: ACK 65d0f1a53354fb25c8152ee5b430cf57e6508594 Tree-SHA512: 6e40e434efea8a8e39f6cb244dfd16aaa5a9db5a2ea762a05d1727357b20e33b7e47c1a652ee88490c9d7952a4caa2f992396fb30346239300d37ae123e36d49
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.
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