There are only a few call sites of these throughout the codebase, so
move the functionality into FastRandomContext, and rewrite all call sites.
This requires the callers to explicit construct FastRandomContext objects,
which do add to the verbosity, but also make potentially apparent locations
where the code can be improved by reusing a FastRandomContext object (see
further commit).
The existing code uses GetRand(nMax), with a default value for nMax, where nMax is the
range of values (not the maximum!) that the output is allowed to take. This will always
miss the last possible value (e.g. GetRand<uint32_t>() will never return 0xffffffff).
Fix this, by moving the functionality largely in RandomMixin, and also adding a
separate RandomMixin::rand function, which returns a value in the entire (non-negative)
range of an integer.
The existing code provides two randomness mechanisms for test purposes:
- g_insecure_rand_ctx (with its wrappers InsecureRand*), which during tests is
initialized using either zeros (SeedRand::ZEROS), or using environment-provided
randomness (SeedRand::SEED).
- g_mock_deterministic_tests, which controls some (but not all) of the normal
randomness output if set, but then makes it extremely predictable (identical
output repeatedly).
Replace this with a single mechanism, which retains the SeedRand modes to control
all randomness. There is a new internal deterministic PRNG inside the random
module, which is used in GetRandBytes() when in test mode, and which is also used
to initialize g_insecure_rand_ctx. This means that during tests, all random numbers
are made deterministic. There is one exception, GetStrongRandBytes(), which even
in test mode still uses the normal PRNG state.
This probably opens the door to removing a lot of the ad-hoc "deterministic" mode
functions littered through the codebase (by simply running relevant tests in
SeedRand::ZEROS mode), but this isn't done yet.
Convert XoRoShiRo128PlusPlus into a full RandomMixin-based RNG class,
providing all utility functionality that FastRandomContext has. In doing so,
it is renamed to InsecureRandomContext, highlighting its non-cryptographic
nature.
To do this, a fillrand fallback is added to RandomMixin (where it is used by
InsecureRandomContext), but FastRandomContext still uses its own fillrand.
In many cases, it is known at compile time how many bits are requested from
randbits. Provide a variant of randbits that accepts this number as a template,
to make sure the compiler can make use of this knowledge. This is used immediately
in rand32() and randbool(), and a few further call sites.
The previous randbits code would, when requesting more randomness than available
in its random bits buffer, discard the remaining entropy and generate new.
Benchmarks show that it's usually better to first consume the existing randomness
and only then generate new ones. This adds some complexity to randbits, but it
doesn't weigh up against the reduced need to generate more randomness.
Rather than make all the useful types of randomness be exclusive to
FastRandomContext, move it to a separate RandomMixin class where it can be reused by
other RNGs.
A Curiously Recurring Template Pattern (CRTP) is used for this, to provide the ability
for individual RNG classes to override one or more randomness functions, without
needing the runtime-cost of virtual classes.
Specifically, RNGs are expected to only provide fillrand and rand64, while all others
are derived from those:
- randbits
- randrange
- randbytes
- rand32
- rand256
- randbool
- rand_uniform_delay
- rand_uniform_duration
- min(), max(), operator()(), to comply with C++ URBG concept.
511aa4f1c7 Add unit test for ChaCha20's new caching (Pieter Wuille)
fb243d25f7 Improve test vectors for ChaCha20 (Pieter Wuille)
93aee8bbda Inline ChaCha20 32-byte specific constants (Pieter Wuille)
62ec713961 Only support 32-byte keys in ChaCha20{,Aligned} (Pieter Wuille)
f21994a02e Use ChaCha20Aligned in MuHash3072 code (Pieter Wuille)
5d16f75763 Use ChaCha20 caching in FastRandomContext (Pieter Wuille)
38eaece67b Add fuzz test for testing that ChaCha20 works as a stream (Pieter Wuille)
5f05b27841 Add xoroshiro128++ PRNG (Martin Leitner-Ankerl)
12ff72476a Make unrestricted ChaCha20 cipher not waste keystream bytes (Pieter Wuille)
6babf40213 Rename ChaCha20::Seek -> Seek64 to clarify multiple of 64 (Pieter Wuille)
e37bcaa0a6 Split ChaCha20 into aligned/unaligned variants (Pieter Wuille)
Pull request description:
This is an alternative to #25354 (by my benchmarking, somewhat faster), subsumes #25712, and adds additional test vectors.
It separates the multiple-of-64-bytes-only "core" logic (which becomes simpler) from a layer around which performs caching/slicing to support arbitrary byte amounts. Both have their uses (in particular, the MuHash3072 code can benefit from multiple-of-64-bytes assumptions), plus the separation results in more readable code. Also, since FastRandomContext effectively had its own (more naive) caching on top of ChaCha20, that can be dropped in favor of ChaCha20's new built-in caching.
I thought about rebasing #25712 on top of this, but the changes before are fairly extensive, so redid it instead.
ACKs for top commit:
ajtowns:
ut reACK 511aa4f1c7
dhruv:
tACK crACK 511aa4f1c7
Tree-SHA512: 3aa80971322a93e780c75a8d35bd39da3a9ea570fbae4491eaf0c45242f5f670a24a592c50ad870d5fd09b9f88ec06e274e8aa3cefd9561d623c63f7198cf2c7
935acdcc79 refactor: modernize the implementation of uint256.* (pasta)
Pull request description:
- Constructors of uint256 to utilize Span instead of requiring a std::vector
- converts m_data into a std::array
- Prefers using `WIDTH` instead of `sizeof(m_data)`
- make all the things constexpr
- replace C style functions with c++ equivalents
- memset -> std::fill
This may also be replaced by std::memset, but I think that std::fill is more idiomatic of modern c++ and readable.
- memcpy -> std::copy
Note: In practice, implementations of std::copy avoid multiple assignments and use bulk copy functions such as std::memmove if the value type is TriviallyCopyable and the iterator types satisfy LegacyContiguousIterator. (https://en.cppreference.com/w/cpp/algorithm/copy)
This could also likely be replaced by std::memcpy, but as said above, I believe the using std::copy is the more c++ way to do anything and is almost guaranteed to compile to the same asm
- memcmp -> std::memcmp
ACKs for top commit:
achow101:
ACK 935acdcc79
hebasto:
Approach ACK 935acdcc79.
aureleoules:
reACK 935acdcc79
john-moffett:
ACK 935acdcc79
stickies-v:
Approach ACK 935acdcc7
Tree-SHA512: 4f1ba54ff2198eea0e505d41e73d552c84c60f6878d5c85a94a8ab57f39afc94ef8d79258e7afd01fa84ec2a99f4404bb877eecd671f65e1ee9273f3129fc650
- Constructors of uint256 to utilize Span instead of requiring a std::vector
- converts m_data into a std::array
- Prefers using `WIDTH` instead of `sizeof(m_data)`
- make all the things constexpr
- replace C style functions with c++ equivalents
- memset -> std::fill
- memcpy -> std::copy
Note: In practice, implementations of std::copy avoid multiple assignments and use bulk copy functions such as std::memmove if the value type is TriviallyCopyable and the iterator types satisfy LegacyContiguousIterator. (https://en.cppreference.com/w/cpp/algorithm/copy)
- memcmp -> std::memcmp
ab1ea29ba1 refactor: make GetRand a template, remove GetRandInt (pasta)
Pull request description:
makes GetRand a template for which any integral type can be used, where the default behavior is to return a random integral up to the max of the integral unless a max is provided.
This simplifies a lot of code from GetRand(std::numeric_limits<uint64_t>::max() -> GetRand<uint64_t>()
ACKs for top commit:
laanwj:
Code review ACK ab1ea29ba1
Tree-SHA512: db5082a0e21783389f1be898ae73e097b31ab48cab1a2c0e29348a4adeb545d4098193aa72a547c6baa6e8205699aafec38d6a27b3d65522fb3246f91b4daae9
This distribution is used for more than just the next inv send, so make
the name more generic.
Also rename to "exponential" to avoid the confusion that this is a
poisson distribution.
-BEGIN VERIFY SCRIPT-
ren() { sed -i "s/\<$1\>/$2/g" $(git grep -l "$1" ./src) ; }
ren PoissonNextSend GetExponentialRand
ren "a poisson timer" "an exponential timer"
-END VERIFY SCRIPT-
50fc4df6c4 [mempool] Persist unbroadcast set to mempool.dat (Amiti Uttarwar)
297a178536 [test] Integration tests for unbroadcast functionality (Amiti Uttarwar)
6851502472 [refactor/test] Extract P2PTxInvStore into test framework (Amiti Uttarwar)
dc1da48dc5 [wallet] Update the rebroadcast frequency to be ~1/day. (Amiti Uttarwar)
e25e42f20a [p2p] Reattempt initial send of unbroadcast transactions (Amiti Uttarwar)
7e93eecce3 [util] Add method that returns random time in milliseconds (Amiti Uttarwar)
89eeb4a333 [mempool] Track "unbroadcast" transactions (Amiti Uttarwar)
Pull request description:
This PR introduces mempool tracking of unbroadcast transactions and periodic reattempts at initial broadcast. This is a part of the rebroadcast project, and a standalone privacy win.
The current rebroadcast logic is terrible for privacy because 1. only the source wallet rebroadcasts transactions and 2. it does so quite frequently. In the current system, if a user submits a transaction that does not immediately get broadcast to the network (eg. they are offline), this "rebroadcast" behavior is the safety net that can actually serve as the initial broadcast. So, keeping the attempts frequent is important for initial delivery within a reasonable timespan.
This PR aims to improve # 2 by reducing the wallet rebroadcast frequency to ~1/day from ~1/15 min. It achieves this by separating the notion of initial broadcast from rebroadcasts. With these changes, the mempool tracks locally submitted transactions & periodically reattempts initial broadcast. Transactions submitted via the wallet or RPC are added to an "unbroadcast" set & are removed when a peer sends a `getdata` request, or the transaction is removed from the mempool. Every 10-15 minutes, the node reattempts an initial broadcast. This enables reducing the wallet rebroadcast frequency while ensuring the transactions will be propagated to the network.
For privacy improvements around # 1, please see #16698.
Thank you to gmaxwell for the idea of how to break out this subset of functionality (https://github.com/bitcoin/bitcoin/pull/16698#issuecomment-571399346)
ACKs for top commit:
fjahr:
Code review ACK 50fc4df6c4
MarcoFalke:
ACK 50fc4df6c4, I think this is ready for merge now 👻
amitiuttarwar:
The current tip `50fc4df` currently has 6 ACKs on it, so I've opened #18807 to address the last bits.
jnewbery:
utACK 50fc4df6c4.
ariard:
Code Review ACK 50fc4df (minor points no need to invalid other ACKs)
robot-visions:
ACK 50fc4df6c4
sipa:
utACK 50fc4df6c4
naumenkogs:
utACK 50fc4df
Tree-SHA512: 2dd935d645d5e209f8abf87bfaa3ef0e4492705ce7e89ea64279cb27ffd37f4727fa94ad62d41be331177332f8edbebf3c7f4972f8cda10dd951b80a28ab3c0f
55b2cb199c random: mark RandAddPeriodic and SeedPeriodic as noexcept (fanquake)
461e547877 doc: correct random.h docs after #17270 (fanquake)
Pull request description:
The usage of `MilliSleep()` in SeedPeriodic (previously SeedSleep) was
[removed](d61f2bb076) in #17270, meaning it, and its users can now be marked `noexcept`.
This also corrects the docs in random.h for some of the changes in #17270.
ACKs for top commit:
practicalswift:
ACK 55b2cb199c
laanwj:
ACK 55b2cb199c
sipa:
ACK 55b2cb199c
Tree-SHA512: 672d369796e7c4f9b4d98dc545e5454999fa1bef373871994a26041d6163c58909e2255e4f820d3ef011679aa3392754eb57477306a89f5fd3d57e2bd7f0811a
On the ::SLOW path we would use OpenSSL as an additional source of
random bytes. This commit removes that functionality. Note that this was
always only an additional source, and that we never checked the return
value
RAND_bytes(): https://www.openssl.org/docs/manmaster/man3/RAND_bytes.html
RAND_bytes() puts num cryptographically strong pseudo-random bytes into buf.
* Instead of calling RandAddSeedSleep anytime the scheduler goes
idle, call its replacement (RandAddSeedPeriodic) just once per
minute. This has better guarantees of actually being run, and
helps limit how frequently the dynamic env data is gathered.
* Since this code runs once per minute regardless now, we no
longer need to keep track of the last time strengthening was
run; just do it always.
* Make strengthening time context dependent (100 ms at startup,
10 ms once per minute afterwards).
