7e6dcd9 random: Add fallback if getrandom syscall not available (Wladimir J. van der Laan)
7cad849 sanity: Move OS random to sanity check function (Wladimir J. van der Laan)
aa09ccb squashme: comment that NUM_OS_RANDOM_BYTES should not be changed lightly (Wladimir J. van der Laan)
224e6eb util: Specific GetOSRandom for Linux/FreeBSD/OpenBSD (Wladimir J. van der Laan)
Tree-SHA512: 9fd408b1316c69de86674f342339b2f89192fd317c8c036b5df4320f828fa263c7966146bfc1904c51137ee4a26e4cb0f560b2cd05e18cde4d808b9b92ad15c4
19cafc6 test: Replace remaining sprintf with snprintf (Wladimir J. van der Laan)
0a17714 uint256: replace sprintf with HexStr and reverse-iterator (Wladimir J. van der Laan)
Tree-SHA512: 2ba1dd4d25e1cbfff4d67b2f483448aa7c34ab5c799cddd48ba5826e5fa6df425abe35e244aaf4c52db9fccfb4d2a25a14bb4597bf9d1fce95991f270da6bb26
83ac719 Change bitcoin address in RPC helpaddress to an invalid address, so people don't accidentally send coins there (like I did). (Marijn Stollenga)
Tree-SHA512: ca1163466a149d567b97efbfcfa8fdfe2d474245b4dd5a1a92555b4e87f8e99df5fee4cd79ef1ce6a98db2337846af78f37c2e6b31d02008b11fa0e151ce6590
Use of `sprintf` is seen as a red flag as many of its uses are insecure.
OpenBSD warns about it while compiling, and some modern platforms, e.g.
[cloudlibc from cloudabi](https://github.com/NuxiNL/cloudlibc) don't
even provide it anymore.
Although our uses of these functions are secure, it can't hurt to
replace them anyway. There are only 3 occurences left, all in the
tests.
- Change initializeResult(int) to initializeResult(bool) to avoid
implicit type conversion.
- Use EXIT_FAILURE and EXIT_SUCCESS instead of magic numbers.
- Remove the argument from shutdownResult(int); it was called with a
constant argument.
An effort to reduce the size of AppInitMain().
The removed code upgrades the location of the block files when
upgrading to 0.8. 0.8 seems to be the oldest version still in use.
If the code was compiled with newer (>=3.17) kernel headers but executed
on a system without the system call, every use of random would crash the
program. Add a fallback for that case.
Move the OS random test to a sanity check function that is called every
time bitcoind is initialized.
Keep `src/test/random_tests.cpp` for the case that later random tests
are added, and keep a rudimentary test that just calls the sanity check.
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
