The problem actually exists in two parts:
1. When sending chunks over a connection, if the queue size is
greater than N, the seed is predictable across every monero node.
>"If rand() is used before any calls to srand(), rand() behaves as if
it was seeded with srand(1). Each time rand() is seeded with the same seed, it
must produce the same sequence of values."
2. The CID speaks for itself: "'rand' should not be used for security-related
applications, because linear congruential algorithms are too easy to break."
*But* this is an area of contention.
One could argue that a CSPRNG is warranted in order to fully mitigate any
potential timing attacks based on crafting chunk responses. Others could argue
that the existing LCG, or even an MTG, would suffice (if properly seeded). As a
compromise, I've used an MTG with a full bit space. This should give a healthy
balance of security and speed without relying on the existing crypto library
(which I'm told might break on some systems since epee is not (shouldn't be)
dependent upon the existing crypto library).
The issue is triggered by the captured `this` in RPC server, which
passes reference to throwable `core_rpc_server`:
`core_rpc_server.cpp:164: m_bootstrap_daemon.reset(new bootstrap_daemon([this]{ return get_random_public_node(); }));`
The solution is to simply remove noexcept from the remaining `bootstrap_daemon`
constructors because noexcept is false in this context.
>"An exception of type "boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::asio::invalid_service_owner>>" is thrown but the throw list "noexcept" doesn't allow it to be thrown. This will cause a call to unexpected() which usually calls terminate()."
Essentially, one can send such a large amount of IDs that core exhausts
all free memory. This issue can theoretically be exploited using very
large CN blockchains, such as Monero.
This is a partial fix. Thanks and credit given to CryptoNote author
'cryptozoidberg' for collaboration and the fix. Also thanks to
'moneromooo'. Referencing HackerOne report #506595.
anonimal