a9ecbdfcaa15499644d16e9c8ad2c63dfc45b37b test: add more inactive filter tests to p2p_filter.py (Sebastian Falbesoner)
5eae034996b340c19cebab9efb6c89d20fe051ef net: limit BIP37 filter lifespan (active between 'filterload' and 'filterclear') (Sebastian Falbesoner)
Pull request description:
This PR fixes https://github.com/bitcoin/bitcoin/issues/18483. On the master branch, there is currently _always_ a BIP37 filter set for every peer: if not a specific filter is set through a `filterload` message, a default match-everything filter is instanciated and pointed to via the `CBloomFilter` default constructor; that happens both initially, when the containing structure `TxRelay` is constructed:
c0b389b335/src/net.h (L812)
and after a loaded filter is removed again through a `filterclear` message:
c0b389b335/src/net_processing.cpp (L3201)
The behaviour was introduced by commit 37c6389c5a (an intentional covert fix for [CVE-2013-5700](https://github.com/bitcoin/bitcoin/pull/18515), according to gmaxwell).
This default match-everything filter leads to some unintended side-effects:
1. `getdata` request for filtered blocks (i.e. type `MSG_FILTERED_BLOCK`) are always responded to with `merkleblock`s, even if no filter was set by the peer, see issue #18483 (strictly speaking, this is a violation of BIP37) c0b389b335/src/net_processing.cpp (L1504-L1507)
2. if a peer sends a `filteradd` message without having loaded a filter via `filterload` before, the intended increasing of the banscore never happens (triggered if `bad` is set to true, a few lines below) c0b389b335/src/net_processing.cpp (L3182-L3186)
This PR basically activates the `else`-branch code paths for all checks of `pfilter` again (on the master branch, they are dead code) by limiting the pointer's lifespan: instead of always having a filter set, the `pfilter` is only pointing to a `CBloomFilter`-instance after receiving a `filterload` message and the instance is destroyed again (and the pointer nullified) after receiving a `filterclear` message.
Here is a before/after comparison in behaviour:
| code part / scenario | master branch | PR branch |
| --------------------------------------------- | ---------------------------------- | ---------------------------------------------------- |
| `getdata` processing for `MSG_FILTERED_BLOCK` | always responds with `merkleblock` | only responds if filter was set via `filterload` |
| `filteradd` processing, no filter was loaded | nothing | peer's banscore increases by 100 (i.e. disconnect) |
On the other code parts where `pfilter` is checked there is no change in the logic behaviour (except that `CBloomFilter::IsRelevantAndUpdate()` is unnecessarily called and immediately returned in the master branch).
Note that the default constructor of `CBloomFilter` is only used for deserializing the received `filterload` message and nowhere else. The PR also contains a functional test checking that sending `getdata` for filtered blocks is ignored by the node if no bloom filter is set.
ACKs for top commit:
MarcoFalke:
re-ACK a9ecbdfcaa, only change is in test code 🕙
Tree-SHA512: 1a656a6d74ccaf628e7fdca063ba63fbab2089e0b6d0a11be9bbd387c2ee6d3230706ff8ffc1a55711481df3d4547137dd7c9d9184d89eaa43ade4927792d0b6
a0b608d5a5