These are available in sandboxes without access to files or
devices. Also [they are safer and more straightforward](https://en.wikipedia.org/wiki/Entropy-supplying_system_calls)
to use than `/dev/urandom` as reading from a file has quite a few edge
cases:
- Linux: `getrandom(buf, buflen, 0)`. [getrandom(2)](http://man7.org/linux/man-pages/man2/getrandom.2.html)
was introduced in version 3.17 of the Linux kernel.
- OpenBSD: `getentropy(buf, buflen)`. The [getentropy(2)](http://man.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man2/getentropy.2)
function appeared in OpenBSD 5.6.
- FreeBSD and NetBSD: `sysctl(KERN_ARND)`. Not sure when this was added
but it has existed for quite a while.
Alternatives:
- Linux has sysctl `CTL_KERN` / `KERN_RANDOM` / `RANDOM_UUID`
which gives 16 bytes of randomness. This may be available
on older kernels, however [sysctl is deprecated on Linux](https://lwn.net/Articles/605392/)
and even removed in some distros so we shouldn't use it.
Add tests for `GetOSRand()`:
- Test that no error happens (otherwise `RandFailure()` which aborts)
- Test that all 32 bytes are overwritten (initialize with zeros, try multiple times)
Discussion:
- When to use these? Currently they are always used when available.
Another option would be to use them only when `/dev/urandom` is not
available. But this would mean these code paths receive less testing,
and I'm not sure there is any reason to prefer `/dev/urandom`.
Closes: #9676
3ddfe29 netbase: Do not print an error on connection timeouts through proxy (Wladimir J. van der Laan)
13f6085 netbase: Make InterruptibleRecv return an error code instead of bool (Wladimir J. van der Laan)
f6d18f5 Qt/Intro: Explain a bit more what will happen first time (Luke Dashjr)
50c5657 Qt/Intro: Storage shouldn't grow significantly with pruning enabled (Luke Dashjr)
9adb694 Qt/Intro: Move sizeWarningLabel text into C++ code (Luke Dashjr)
Remove "nLowestTimestamp <= chainActive.Tip()->GetBlockTimeMax()" check from
importmulti, which is always true because nLowestTimestamp is set to the
minimum of the most recent block time and all the imported key timestamps,
which is necessarily lower than the maximum block time.
e662af3 Use 2 hour grace period for key timestamps in importmulti rescans (Russell Yanofsky)
38d3e9e [qa] Extend import-rescan.py to test imports on pruned nodes. (Russell Yanofsky)
c28583d [qa] Extend import-rescan.py to test specific key timestamps (Russell Yanofsky)
8be0866 [qa] Simplify import-rescan.py (Russell Yanofsky)
- If the -maxsigcachesize parameter is set to zero, setup a minimum sized
sigcache (2 elements) rather than segfaulting.
- Handle maxsigcachesize being negative
- Handle maxsigcachesize being too large
Get rid of partial functions so the test can be more easily extended to add
more variants of imports with options that affect rescanning (e.g. different
key timestamps).
Also change the second half of the test to send /to/ the imported addresses,
instead of /from/ the imported addresses. The goal of this part of the test was
to confirm that the wallet would pick up new transactions after an import
regardless of whether or not a rescan happened during the import. But because
the wallet can only do this reliably for incoming transactions and not outgoing
transactions (which require the wallet to look up transaction inputs) the test
previously was less meaningful than it should have been.
A new AssertLockHeld(cs_wallet) call was added in commit a58370e
"Dedup nTimeFirstKey update logic" (part of PR #9108).
The lock held assertion will fail when loading prexisting wallets files from
before the #9108 merge that have watch-only keys.
