zaino serve gRPC: bind loopback, not 0.0.0.0 - #56
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The embedded zaino serves its gRPC on 0.0.0.0:P+10001 while the JSON-RPC one line above binds 127.0.0.1. On a faucet node that gRPC serves RequestFaucetDonation, a direct path to the mining wallet that bypasses any operator-side rate limiting, so exposing it on all interfaces is a wallet-drain risk that only a firewall stands in front of. There is no config knob for the bind, so this is the one-line fix: match the JSON-RPC and bind loopback.
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Found this while auditing which ports a faucet node exposes.
How we found it
Listed the listeners on the box and spotted
*:29234(the zaino serve gRPC, atP+10001) bound to0.0.0.0, while the JSON-RPC one line above it in the source binds127.0.0.1. That mismatch is the tell.The reason it matters: that gRPC serves
RequestFaucetDonation, which pays straight out of the mining wallet and skips any operator-side rate limiting. So an all-interfaces bind on that port is a direct wallet-drain path the moment a firewall slips. Right now only ufw is standing in front of it.Went looking for a config knob to move it to loopback and there isn't one, the address is hardcoded in
start.rs. So this is the one-line fix: make the gRPC bind match the JSON-RPC and sit on loopback.Testing
Deployed on a live feature-net node.
ss -lntpnow shows127.0.0.1:29234and the node runs normally.