We previously identified if we relay addresses to the connection by checking
for the existence of the m_addr_known data structure. With this commit, we
answer this question based on the connection type.
IsAddrRelayPeer() checked for the existence of the m_addr_known
With this commit, the files in /usr/local/ will not be included in
`make cov` or `make cov_fuzz` coverage reports. This behavior could
be observed when generating the reports on macOS with brew-installed
clang.
Onion peers are disadvantaged under our eviction criteria, so prevent eventual
eviction of them in the presence of contention for inbound slots by reserving
some slots for localhost peers (sorted by longest uptime).
Block-relay-only connections exist as a protection against eclipse attacks, by
creating a path for block propagation that may be unknown to adversaries.
Protect against inbound peer connection slot attacks from disconnecting such
peers by attempting to protect up to 8 peers that are not relaying transactions
but appear to be full-nodes, sorted by recency of last delivered block.
Thanks to gmaxwell for suggesting these strategies.
b893688357 depends: Specify LDFLAGS to cmake as well (Carl Dong)
b3f541f618 depends: Prepend CPPFLAGS to C{,XX}FLAGS for CMake (Carl Dong)
8e121e5509 depends: Cleanup CMake invocation (Carl Dong)
8c7cd0c6d9 depends: More robust cmake invocation (Carl Dong)
3ecf0eca63 depends: Use $($(package)_cmake) instead of cmake (Carl Dong)
Pull request description:
- Use `$($(package)_cmake)` instead of invoking `cmake` directly
- Use well-known env vars instead of overriding CMake variables
ACKs for top commit:
ryanofsky:
Code review ACK b893688357. Only changes since last review are new commits adding whitespace, cppflags and ldflags to cmake invocation
Tree-SHA512: cfcd8cc9dcd0b336cf48b82fca9fe4bbc7930ed397cb7a68a07066680eb4c1906a6a9b5bd2589b4b4999e8f16232fa30ee9b376b60f4456d0fff931fbf9cc19a
d780293e1e net: improve nLastBlockTime and nLastTXTime documentation (Jon Atack)
Pull request description:
Follow-up to #19731 to help alleviate confusion around `nLastBlockTime` and `nLastTXTime`, now also provided by the JSON-RPC API as `last_block` and `last_transaction` in `getpeerinfo` output.
Thanks to John Newbery, credited in the commit, and to Dave Harding and Adam Jonas during discussions on how to best explain these in this week's Optech newsletter.
ACKs for top commit:
practicalswift:
ACK d780293e1e
MarcoFalke:
ACK d780293e1e
harding:
ACK d780293e1e . The added documentation matches my reading of the code and answers a question I had after seeing #19731
0xB10C:
ACK d780293e1e
Tree-SHA512: 72d47cf50a099913c7e4753cb80e11785b26fb66fa3a8b6c382fde4ea725116f3d215f93d32a567246d269768e66159f8dcf017a1bbc6d5f2489a35f81c316fa
fb56d37612 p2p: ensure inv is GenMsgTx before ToGenTxid in inv processing (John Newbery)
aa3621385e test: use CInv::MSG_WITNESS_TX flag in p2p_segwit (Jon Atack)
24ee4f01ea p2p: make gtxid(.hash) and fAlreadyHave localvars const (Jon Atack)
b1c855453b p2p: use CInv block message helpers in net_processing.cpp (Jon Atack)
acd6642167 [net processing] Change AlreadyHaveTx() to take a GenTxid (John Newbery)
5fdfb80b86 [net processing] Change AlreadyHaveBlock() to take block_hash argument (John Newbery)
430e183b89 [net processing] Remove mempool argument from AlreadyHaveBlock() (John Newbery)
42ca5618ca [net processing] Split AlreadyHave() into separate block and tx functions (John Newbery)
39f1dc9445 p2p: remove nFetchFlags from NetMsgType TX and INV processing (Jon Atack)
471714e1f0 p2p: add CInv block message helper methods (Jon Atack)
Pull request description:
Building on #19590 and the recent `wtxid` and `GenTxid` changes, this is a refactoring and cleanup PR to simplify and improve some of the net processing code.
Some of the diffs are best reviewed with `-w` to ignore spacing.
Co-authored by John Newbery.
ACKs for top commit:
laanwj:
Code review ACK fb56d37612
jnewbery:
utACK fb56d37612
vasild:
ACK fb56d3761
Tree-SHA512: ba39b58e6aaf850880a842fe5f6295e9f1870906ef690206acfc17140aae2ac854981e1066dbcd4238062478762fbd040ef772fdc2c50eea6869997c583e6a6d
c276df7759 zmq: enable tcp keepalive (mruddy)
Pull request description:
This addresses https://github.com/bitcoin/bitcoin/issues/12754.
These changes enable node operators to address the silent dropping (by network middle boxes) of long-lived low-activity ZMQ TCP connections via further operating system level TCP keepalive configuration. For example, ZMQ sockets that publish block hashes can be affected in this way due to the length of time it sometimes takes between finding blocks (e.g.- sometimes more than an hour).
Prior to this patch, operating system level TCP keepalive configurations would not take effect since the SO_KEEPALIVE option was not enabled on the underlying socket.
There are additional ZMQ socket options related to TCP keepalive that can be set. However, I decided not to implement those options in this changeset because doing so would require adding additional bitcoin node configuration options, and would not yield a better outcome. I preferred a small, easily reviewable patch that doesn't add a bunch of new config options, with the tradeoff that the fine tuning would have to be done via well-documented operating system specific configurations.
I tested this patch by running a node with:
`./src/qt/bitcoin-qt -regtest -txindex -datadir=/tmp/node -zmqpubhashblock=tcp://127.0.0.1:28332 &`
and connecting to it with:
`python3 ./contrib/zmq/zmq_sub.py`
Without these changes, `ss -panto | grep 28332 | grep ESTAB | grep bitcoin` will report no keepalive timer information. With these changes, the output from the prior command will show keepalive timer information consistent with the configuration at the time of connection establishment, e.g.-: `timer:(keepalive,119min,0)`.
I also tested with a non-TCP transport and did not witness any adverse effects:
`./src/qt/bitcoin-qt -regtest -txindex -datadir=/tmp/node -zmqpubhashblock=ipc:///tmp/bitcoin.block &`
ACKs for top commit:
adamjonas:
Just to summarize for those looking to review - as of c276df7759 there are 3 tACKs (n-thumann, Haaroon, and dlogemann), 1 "looks good to me" (laanwj) with no NACKs or any show-stopping concerns raised.
jonasschnelli:
utACK c276df7759
Tree-SHA512: b884c2c9814e97e666546a7188c48f9de9541499a11a934bd48dd16169a900c900fa519feb3b1cb7e9915fc7539aac2829c7806b5937b4e1409b4805f3ef6cd1
Enable the GUI to also use the load_on_startup feature.
Wallets loaded in the GUI always have load_on_startup=true.
When they are unloaded from the GUI, load_on_startup=false.
To facilitate this change, UpdateWalletSetting is moved into the wallet
module and called from within LoadWallet, RemoveWallet, and
Createwallet. This change does not actually touch the GUI code but
rather the wallet functions that are shared between the GUI and RPC.
36ec9801a4 test: Add chacha20 test vectors in muhash (Fabian Jahr)
0e2b400fea test: Add basic Python/C++ Muhash implementation parity unit test (Fabian Jahr)
b85543cb73 test: Add Python MuHash3072 implementation to test framework (Pieter Wuille)
ab30cece0e test: Move modinv to util and add unit test (Fabian Jahr)
Pull request description:
This is the second in a [series of pull requests](https://github.com/bitcoin/bitcoin/pull/18000) to implement an Index for UTXO set statistics.
This pull request adds a Python implementation of Muhash3072, a homomorphic hashing algorithm to be used for hashing the UTXO set. The Python implementation can then be used to compare behavior with the C++ version.
ACKs for top commit:
jnewbery:
utACK 36ec9801a
laanwj:
Code review ACK 36ec9801a4
Tree-SHA512: a3519c6e11031174f1ae71ecd8bcc7f3be42d7fc9c84c77f2fbea7cfc5ad54fcbe10b55116ad8d9a52ac5d675640eefed3bf260c58a02f2bf3bc0d8ec208baa6
ea74e10acf doc: Add best practice for annotating/asserting locks (Hennadii Stepanov)
2ee7743fe7 sync.h: Make runtime lock checks require compile-time lock checks (Anthony Towns)
23d71d171e Do not hide compile-time thread safety warnings (Hennadii Stepanov)
3ddc150857 Add missed thread safety annotations (Hennadii Stepanov)
af9ea55a72 Use LockAssertion utility class instead of AssertLockHeld() (Hennadii Stepanov)
Pull request description:
On the way of transit from `RecursiveMutex` to `Mutex` (see #19303) it is crucial to have run-time `AssertLockHeld()` assertion that does _not_ hide compile-time Clang Thread Safety Analysis warnings.
On master (65e4ecabd5) using `AssertLockHeld()` could hide Clang Thread Safety Analysis warnings, e.g., with the following patch applied:
```diff
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -607,7 +607,7 @@ public:
void addUnchecked(const CTxMemPoolEntry& entry, setEntries& setAncestors, bool validFeeEstimate = true) EXCLUSIVE_LOCKS_REQUIRED(cs, cs_main);
void removeRecursive(const CTransaction& tx, MemPoolRemovalReason reason) EXCLUSIVE_LOCKS_REQUIRED(cs);
- void removeForReorg(const CCoinsViewCache* pcoins, unsigned int nMemPoolHeight, int flags) EXCLUSIVE_LOCKS_REQUIRED(cs, cs_main);
+ void removeForReorg(const CCoinsViewCache* pcoins, unsigned int nMemPoolHeight, int flags) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
void removeConflicts(const CTransaction& tx) EXCLUSIVE_LOCKS_REQUIRED(cs);
void removeForBlock(const std::vector<CTransactionRef>& vtx, unsigned int nBlockHeight) EXCLUSIVE_LOCKS_REQUIRED(cs);
```
Clang compiles the code without any thread safety warnings.
See "Add missed thread safety annotations" commit for the actual thread safety warnings that are fixed in this PR.
ACKs for top commit:
MarcoFalke:
ACK ea74e10acf 🎙
jnewbery:
ACK ea74e10acf
ajtowns:
ACK ea74e10acf
Tree-SHA512: 8cba996e526751a1cb0e613c0cc1b10f027a3e9945fbfb4bd30f6355fd36b9f9c2e1e95ed3183fc254b42df7c30223278e18e5bdb5e1ef85db7fef067595d447
3340dbadd3 Remove -zapwallettxes (Andrew Chow)
Pull request description:
It's not clear what use there is to keeping `-zapwallettxes` given that it's intended usage has been superseded by `abandontransaction`. So this removes it outright.
Alternative to #19700
ACKs for top commit:
meshcollider:
utACK 3340dbadd3
fanquake:
ACK 3340dbadd3 - remaining manpage references will get cleaned up pre-release.
Tree-SHA512: 3e58e1ef6f4f94894d012b93e88baba3fb9c2ad75b8349403f9ce95b80b50b0b4f443cb623cf76c355930db109f491b3442be3aa02972e841450ce52cf545fc8
7356292e1d Have zmq reorg test cover mempool txns (Gregory Sanders)
a0f4f9c983 Add zmq test for transaction pub during reorg (Gregory Sanders)
2399a0600c Add test case for mempool->block zmq notification (Gregory Sanders)
e70512a83c Make ordering of zmq consumption irrelevant to functional test (Gregory Sanders)
Pull request description:
Tests written to better define what messages are sent when. Also did a bit of refactoring to make sure the exact notification channel ordering doesn't matter.
Confusions below aside, I believe having these more descriptive tests helps describe what behavior we expect from ZMQ notificaitons.
Remaining confusion:
1) Notification patterns seem to vary wildly with the inclusion of mempool transactions being reorg'ed. See difference between "Add zmq test for transaction pub during reorg" and "Have zmq reorg test cover mempool txns" commits for specifics.
2) Why does a reorg'ed transaction get announced 3 times? From what I understand it can get announced once for disconnected block, once for mempool entry. What's the third? It occurs a 4th time when included in a block(not added in test)
ACKs for top commit:
laanwj:
code review ACK 7356292e1d
promag:
Code review ACK 7356292e1d.
Tree-SHA512: 573662429523fd6a1af23dd907117320bc68cb51a93fba9483c9a2160bdce51fb590fcd97bcd2b2751d543d5c1148efa4e22e1c3901144f882b990ed2b450038
-zapwallettxes is made a hidden option to inform users that it is
removed and they should be using abandontransaction to do the stuck
transaction thing.
fa3d9ce325 rpc: Assert that RPCArg names are equal to CRPCCommand ones (rpcdump) (MarcoFalke)
fa32c1d5ec rpc: Assert that RPCArg names are equal to CRPCCommand ones (zmq) (MarcoFalke)
faaa46dc20 rpc: Assert that RPCArg names are equal to CRPCCommand ones (mining) (MarcoFalke)
fa93bc14c7 rpc: Remove unused return type from appendCommand (MarcoFalke)
Pull request description:
This is split out from #18531 to just touch the RPC methods in misc. Description from the main pr:
### Motivation
RPCArg names in the rpc help are currently only used for documentation. However, in the future they could be used to teach the server the named arguments. Named arguments are currently registered by the `CRPCCommand`s and duplicate the RPCArg names from the documentation. This redundancy is fragile, and has lead to errors in the past (despite having linters to catch those kind of errors). See section "bugs found" for a list of bugs that have been found as a result of the changes here.
### Changes
The changes here add an assert in the `CRPCCommand` constructor that the RPCArg names are identical to the ones in the `CRPCCommand`.
### Future work
> Here or follow up, makes sense to also assert type of returned UniValue?
Sure, but let's not get ahead of ourselves. I am going to submit any further works as follow-ups, including:
* Removing the CRPCCommand arguments, now that they are asserted to be equal and thus redundant
* Removing all python regex linters on the args, now that RPCMan can be used to generate any output, including the cli.cpp table
* Auto-formatting and sanity checking the RPCExamples with RPCMan
* Checking passed-in json in self-check. Removing redundant checks
* Checking returned json against documentation to avoid regressions or false documentation
* Compile the RPC documentation at compile-time to ensure it doesn't change at runtime and is completely static
### Bugs found
* The assert identified issue #18607
* The changes itself fixed bug #19250
ACKs for top commit:
fjahr:
tested ACK fa3d9ce325
promag:
Code review ACK fa3d9ce325.
Tree-SHA512: 068ade4b55cc195868d53b7f9a27151d45b440857bb069e261a49d102a49a38fdba5d68868516a1d66a54a73ba34681362f934ded7349e894042bde873b75719
a104caeb40 Update the vcpkg checkout commit ID in appveyor config. (Aaron Clauson)
Pull request description:
A recent appveyor vm update broke the build of the `berkeleydb` vcpkg dependency, see #19839. The temporary resolution was to switch back to the previous appveyor vm.
This PR updates the pegged vcpkg commit ID to the most recent commit as of 31 Aug 2020. That commit ID has been tested against the latest appveyor vm and is able to build Bitcoin Core successfully.
The vcpkg bump includes a [patch](https://github.com/microsoft/vcpkg/pull/12870) to the `berkeleydb` build config which allows it to be built on the latest appveyor vm.
ACKs for top commit:
MarcoFalke:
Concept ACK a104caeb40
Tree-SHA512: 6d363d1615c51bb3d4b324eb96d53950648fc97fc81ffaef91ee6e92f1336776d150d89f6e859f354ee75ce66afcef07aa19ed39b725dbb3f47ba67d26e111db
6d1f51343c [rpc] fundrawtransaction, walletcreatefundedpsbt lock manually selected coins (Sjors Provoost)
Pull request description:
When using `fundrawtransaction` and `walletcreatefundedpsbt` with `lockUnspents`, it would only lock automatically selected coins, not manually selected coins. That doesn't make much sense to me if the goal is to prevent accidentally double-spending yourself before you broadcast a transaction.
Note that when creating a transaction, manually selected coins are automatic "unlocked" (or more accurately: the lock is ignored). Earlier versions of this PR introduced an error when a locked coin is manually selected, but this idea was abandoned after some discussion. An application that uses this RPC should either rely on automatic coin selection (with `lockUnspents`) or handle lock concurrency itself with manual coin selection. In particular it needs to make sure to avoid/pause calls with automatic coin selection between calling `lockunspent` and the subsequent spending RPC.
See #7518 for historical background.
ACKs for top commit:
meshcollider:
Code review ACK 6d1f51343c
fjahr:
Code review ACK 6d1f51343c
Tree-SHA512: 8773c788d92f2656952e1beac147ba9956b8c5132d474e0880e4c89ff53642928b4cbfcd1cb3d17798b9284f02618a8830c93a9f7a4733e5bded96adff1d5d4d
772ea4844c wallet: Avoid recursive lock in IsTrusted (João Barbosa)
819f10f671 wallet, refactor: Immutable CWalletTx::pwallet (João Barbosa)
Pull request description:
This change moves `CWalletTx::IsTrusted` to `CWallet` in order to have TSAN. So now `CWallet::IsTrusted` requires `cs_wallet` and the recursive lock no longer happens.
Motivated by https://github.com/bitcoin/bitcoin/pull/19289/files#r473308226.
ACKs for top commit:
meshcollider:
utACK 772ea4844c
hebasto:
ACK 772ea4844c, reviewed and tested on Linux Mint 20 (x86_64).
Tree-SHA512: 702ffd928b2f42a8b90de398790649a5fd04e1ac3877558da928e94cdeb19134883f06c3a73a6826c11c912facf199173375a70200737e164ccaea1bec515b2a
46fcac1e4b tests: Add fuzzing harness for ec_seckey_import_der(...) and ec_seckey_export_der(...) (practicalswift)
b667a90389 tests: Add fuzzing harness for SigHasLowR(...) and ecdsa_signature_parse_der_lax(...) (practicalswift)
Pull request description:
Add fuzzing harness for `SigHasLowR(...)` and `ecdsa_signature_parse_der_lax(...)`.
See [`doc/fuzzing.md`](https://github.com/bitcoin/bitcoin/blob/master/doc/fuzzing.md) for information on how to fuzz Bitcoin Core. Don't forget to contribute any coverage increasing inputs you find to the [Bitcoin Core fuzzing corpus repo](https://github.com/bitcoin-core/qa-assets).
Happy fuzzing :)
ACKs for top commit:
Crypt-iQ:
ACK 46fcac1e4b
Tree-SHA512: 11a4856a1efd9a04030a8c8aee2413fd5be1ea248147e649a48a55bacdf732bb48a19ee1ce2761d47d4dd61c9598aec53061b961b319ad824d539dda11a8ccf4
24bf17602c gui refactor: Inline SplashScreen::ConnectWallet (Russell Yanofsky)
e4f4350471 refactor: Move wallet methods out of chain.h and node.h (Russell Yanofsky)
b266b3e0bf refactor: Create interfaces earlier during initialization (Russell Yanofsky)
Pull request description:
Add WalletClient interface so node interface is cleaner and don't need wallet-specific methods.
The new NodeContext::wallet_client pointer will also be needed to eliminate global wallet variables like ::vpwallets in #19101, because createWallet(), loadWallet(), getWallets(), etc methods called by the GUI need a way to get a reference to the list of open wallets if it is no longer a global variable.
ACKs for top commit:
promag:
Code review ACK 24bf17602c.
MarcoFalke:
ACK 24bf17602c🐚
Tree-SHA512: a70d3776cd6723093db8912028c50075ec5fa0a48b961cb1a945f922658f5363754f8380dbb8378ed128c8c858913024f8264740905b8121a35c0d63bfaed7cf
fa0572d0f3 Pass mempool reference to chainstate constructor (MarcoFalke)
Pull request description:
Next step toward #19556
Instead of relying on the mempool global, each chainstate is given a reference to a mempool to keep up to date with the tip (block connections, disconnections, reorgs, ...)
ACKs for top commit:
promag:
Code review ACK fa0572d0f3.
darosior:
ACK fa0572d0f3
hebasto:
ACK fa0572d0f3, reviewed and tested on Linux Mint 20 (x86_64).
Tree-SHA512: 12184d33ae5797438d03efd012a07ba3e4ffa0d817c7a0877743f3d7a7656fe279280c751554fc035ccd0058166153b6c6c308a98b2d6b13998922617ad95c4c
c4b85ba704 Bugfix: Define and use HAVE_FDATASYNC correctly outside LevelDB (Luke Dashjr)
Pull request description:
Fixes a bug introduced in #19614
The LevelDB-specific fdatasync check was only using `AC_SUBST`, which works for Makefiles, but doesn't define anything for C++. Furthermore, the #define is typically 0 or 1, never undefined.
This fixes both issues by defining it and checking its value instead of whether it is merely defined.
Pulled out of #14501 by fanquake's request
ACKs for top commit:
fanquake:
ACK c4b85ba704 - thanks for catching and fixing my mistake.
laanwj:
Code review ACK c4b85ba704
Tree-SHA512: 91d5d426ba000b4f3ee7e2315635e24bbb23ceff16269ddf4f65a63d25fc9e9cf94a3b236eed2f8031cc36ddcf78aeb5916efcb244f415943a8a12f907ede8f9
b35e74ba37 wallet, refactor: Remove duplicate map lookups in GetAddressBalances (João Barbosa)
Pull request description:
Now just one lookup in `balances` instead of three.
ACKs for top commit:
achow101:
ACK b35e74ba37
theStack:
ACK b35e74ba37
practicalswift:
ACK b35e74ba37
Tree-SHA512: a73c1b336406a569e3bb10290618c5950b944db58ed0b05ff202d097684bb3ba3a5942c8d30443960052aa16438c054e2d02977b67aa901cce665c4df0ee5602
3ec8f4c080 Set appveyor vm version to previous Visual Studio 2019 release. (Aaron Clauson)
Pull request description:
The Visual Studio 2019 Appveyor [update](https://www.appveyor.com/updates/2020/08/29/) includes a bump of `cmake` to `3.18.2`.
The `berkeleydb` dependency from the pegged `vcpkg` commit now fails to build with the `cmake` update.
Setting the Appveyor VM back to the previous version should fix the immediate issue while a solution is identified for updating the `berkeleydb` build configuration.
ACKs for top commit:
hebasto:
ACK 3ec8f4c080, AppVeyor build is ok now.
Tree-SHA512: 61e10d0260c1c51dc6c552c857b3013f55ee324e26b1229bf7ef6f14c3e296762148db66a994ecc33fdc43e81592a7f8442d17b407964edb774b482d84735757
This change prepares for upcoming commit "Do not hide compile-time
thread safety warnings" by replacing AssertLockHeld() with
LockAssertion() where needed.
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
