security: apply 2026-06 source-review fixes (consensus, memory, crypto, FFI, P2P, wallet)

[VictorLux]

Summary

Applies the fixes from a full multi-domain security review of the ZClassic source (crypto, C/C++ memory safety, Rust/FFI, consensus, P2P/DoS, wallet/RPC, performance/stability, supply chain). Each fix is traced to verified source lines and was functionally exercised on a mainnet node at tip ~3.14M.

18 files changed, +297 / −65. This is not a consensus change versus the network — every fix is either non-consensus, node-local, or (for BLK-01) brings an import code path in line with the block-size rule CheckBlock already enforces. No hard fork; nothing here changes block/transaction acceptance for peers.

Fixes

Consensus / validation

ID	File	Change
BLK-01	consensus/consensus.h, main.cpp	Shared GENEROUS_BLOCK_SIZE_LIMIT; widen LoadExternalBlockFile buffer and the nSize gate so -reindex / -loadblock import the 1,272 canonical mainnet blocks between 200 KB and 2 MB that the old MAX_BLOCK_SIZE cap silently skipped (which would otherwise produce a divergent/incomplete chainstate on rebuild).
CON-01	main.cpp	LoadBlockIndexDB value-pool rebuild now uses overflow-safe CheckedAdd (was raw signed + on CAmount — undefined behaviour on overflow, feeding the ZIP-209 turnstile).
CON-05	main.cpp	Drop the no-op vtx.size() > GENEROUS_BLOCK_SIZE_LIMIT conjunct (tx count vs a byte constant) in CheckBlock; the serialized-size check is the real guard.

Memory safety

ID	File	Change
MEM-01	streams.h	CBaseDataStream::read/ignore compute bounds in size_t with a pre-addition overflow guard (was unsigned int narrowing of a size_t length → latent OOB memcpy).
MEM-02	serialize.h	ReadVarInt guards against overflow of I before the shift and before n++ (upstream Bitcoin Core form) — prevents value wrap / signed UB (VARINT is used on signed fields like nFile/nPos) and unbounded spin.
MEM-03	bootstrap.cpp	Bound the addr element count before allocating the vector in bootstrap discovery (was deserialize-then-check).

Cryptography

ID	File	Change
CRY-01	zcash/NoteEncryption.cpp	Zeroize the symmetric key K and dhsecret via a RAII MemoryCleanser declared right after each buffer — cleared on every scope exit (normal/early return, AEAD-failure, and the KDF/DH-failure throw).
CRY-03	zcash/Proof.cpp	Explicit G1 prime-order subgroup check in to_libsnark_g1(), mirroring the existing G2 check (defense-in-depth; rejects nothing today as G1 cofactor = 1).

Rust / FFI

ID	File	Change
RUST-01	transaction_builder.cpp	Check the bool returns of librustzcash_sapling_spend_sig / _binding_sig; free the proving ctx and return an error instead of building a silently zero-signed transaction.
RUST-02	init.cpp	ferror guard in the check_file_hash read loop — no infinite 100%-CPU spin on a real I/O error during startup.

P2P / performance / stability

ID	File	Change
NET-01	main.cpp	uintptr_t (not unsigned int) for the addr-relay pointer hash so the full 64-bit pointer mixes in.
NET-02	net.cpp	Prune expired setBanned entries on each Ban() (bounds map growth / the per-connection linear scan).
PERF-01	wallet/wallet.cpp	Drop the redundant LOCK(mempool.cs) in ReacceptWalletTransactions (ATMP takes it internally) — removes the flagged cs_wallet → mempool.cs lock-order edge.
PERF-03	net.cpp	Cap mapRelay growth (evict oldest) so a unique-txid flood can't grow it unbounded before the 15-min timer.
PERF-04	bootstrapvalidation.cpp	Reduce the background validator's cs_main batch budget 80 → 20 ms (shorter stalls to live message processing).

Wallet / RPC

ID	File	Change
WAL-01	wallet/rpcwallet.cpp	z_sendmany help text warns that -debug=zrpcunsafe / =all writes shielded sender/recipients/amounts/memo to debug.log.
WAL-02	httpserver.cpp	Warn when -rpcallowip is set without -rpcbind (RPC then binds all interfaces).
WAL-03	wallet/wallet.cpp	Raise the wallet KDF iteration floor 25,000 → 100,000 (encrypt + change-passphrase).
WAL-05	wallet/rpcdump.cpp	dumpwallet sets the export file to 0600 immediately (it contains all private keys + the HD seed).
WAL-06	rpc/server.h, wallet/rpcwallet.cpp, rpc/misc.cpp	nWalletUnlockTime → std::atomic<int64_t>; reads use .load() (no torn read vs the relock timer). Writes still under the lock.

CI

ID	File	Change
SUP-04	qa/pull-tester/rpc-tests.sh	Re-enable the shielded regression tests (incl. zcjoinsplitdoublespend.py, shieldcoinbase, nullifiers, treestate, anchorfork, zkey import/export, NU-activation).

Documentation only (no behaviour change)

• CON-02/03 — documented the ZIP-209 invariant: on a per-block overflow nChainSaplingValue becomes none and propagates, so the turnstile is skipped (not enforced) across the unknown window — corrupted data can never cause a wrong turnstile pass, but it is also not enforced there (acceptable for corruption recovery).
• CON-04 — restoring the tight 102 KB post-Sapling tx-size limit for new blocks is a soft fork and must be staged at a fixed future activation height in ContextualCheckTransaction; left unchanged.

Out of scope / deferred (tracked, not in this PR)

• CON-06 — Buttercup "triple-halving" emission: confirm-intent only.
• CON-07 — Bubbly and Buttercup share consensus branch ID 0x930b540d (upgrades.cpp:38,43). Immutable (active since height 707000; baked into the sighashes of all v4 transactions since) — must not be changed retroactively; the next network upgrade must use a fresh, unique branch ID.
• SUP-01/02/03 — dependency bumps (OpenSSL 1.1.1w EOL, Rust 1.70/rand 0.4.2, libevent/leveldb/proton): require maintainer re-pinning of verified sha256 hashes + cargo audit.
• PERF-02 (-maxmempool eviction), WAL-04 (passphrase mlock), SUP-05 (orphaned crate_*.mk).

Verification

• Builds and runs: rebuilt and restarted; clean startup, full block-index load, block verify with no inconsistencies, wallet load, sync to tip.
• MEM-02 / CON-01 exercised: VARINT decoding ran across all ~3.14M blocks during index load with no errors; index value-pool rebuild clean (no turnstile/overflow lines).
• CRY-01 + RUST-01 exercised end-to-end: a shielded z_sendmany round-trip succeeded — note encrypted, spend + binding signatures created (the RUST-01 error branch did not fire), broadcast, mined, and decrypted on receipt at the destination. Sapling note decryption (balance read) also confirmed.
• BLK-01 confirmed by a full -reindex on a datadir copy: the block at height 6587 (hash 000000077ff04de591789d4e11b26e4387e14753cc14a997168acf6cea788f70, 226 001 bytes — the first block over the old 200 000-byte MAX_BLOCK_SIZE) was read and connected, and the chain advanced past it (6588, 6589, …). The unpatched LoadExternalBlockFile would have skipped it and stalled at 6586. Hash matches the audit-full.json oversized-block record.
• git diff --check is clean.

Reviewer checklist

• Build with the depends tree.
• Run qa/pull-tester/rpc-tests.sh — the re-enabled shielded tests are not yet run in CI here; triage any failure rather than re-commenting it.
• -reindex on a copy of a full-history datadir to confirm BLK-01 imports the large historical blocks — done (height 6587 / 226 KB connected, hash-matched; see Verification). Reviewers may re-run to a full matching tip if desired.
• Spot-check the consensus diff in main.cpp (LoadBlockIndexDB, CheckBlock).

Notes

• No new dependencies. No public API/RPC removed (only a warning + help-text addition).
• The shielded-test re-enable (SUP-04) may surface pre-existing failures; those should be triaged, not hidden.

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