Daemons intended for public use can be set up to require payment
in the form of hashes in exchange for RPC service. This enables
public daemons to receive payment for their work over a large
number of calls. This system behaves similarly to a pool, so
payment takes the form of valid blocks every so often, yielding
a large one off payment, rather than constant micropayments.
This system can also be used by third parties as a "paywall"
layer, where users of a service can pay for use by mining Monero
to the service provider's address. An example of this for web
site access is Primo, a Monero mining based website "paywall":
https://github.com/selene-kovri/primo
This has some advantages:
- incentive to run a node providing RPC services, thereby promoting the availability of third party nodes for those who can't run their own
- incentive to run your own node instead of using a third party's, thereby promoting decentralization
- decentralized: payment is done between a client and server, with no third party needed
- private: since the system is "pay as you go", you don't need to identify yourself to claim a long lived balance
- no payment occurs on the blockchain, so there is no extra transactional load
- one may mine with a beefy server, and use those credits from a phone, by reusing the client ID (at the cost of some privacy)
- no barrier to entry: anyone may run a RPC node, and your expected revenue depends on how much work you do
- Sybil resistant: if you run 1000 idle RPC nodes, you don't magically get more revenue
- no large credit balance maintained on servers, so they have no incentive to exit scam
- you can use any/many node(s), since there's little cost in switching servers
- market based prices: competition between servers to lower costs
- incentive for a distributed third party node system: if some public nodes are overused/slow, traffic can move to others
- increases network security
- helps counteract mining pools' share of the network hash rate
- zero incentive for a payer to "double spend" since a reorg does not give any money back to the miner
And some disadvantages:
- low power clients will have difficulty mining (but one can optionally mine in advance and/or with a faster machine)
- payment is "random", so a server might go a long time without a block before getting one
- a public node's overall expected payment may be small
Public nodes are expected to compete to find a suitable level for
cost of service.
The daemon can be set up this way to require payment for RPC services:
monerod --rpc-payment-address 4xxxxxx \
--rpc-payment-credits 250 --rpc-payment-difficulty 1000
These values are an example only.
The --rpc-payment-difficulty switch selects how hard each "share" should
be, similar to a mining pool. The higher the difficulty, the fewer
shares a client will find.
The --rpc-payment-credits switch selects how many credits are awarded
for each share a client finds.
Considering both options, clients will be awarded credits/difficulty
credits for every hash they calculate. For example, in the command line
above, 0.25 credits per hash. A client mining at 100 H/s will therefore
get an average of 25 credits per second.
For reference, in the current implementation, a credit is enough to
sync 20 blocks, so a 100 H/s client that's just starting to use Monero
and uses this daemon will be able to sync 500 blocks per second.
The wallet can be set to automatically mine if connected to a daemon
which requires payment for RPC usage. It will try to keep a balance
of 50000 credits, stopping mining when it's at this level, and starting
again as credits are spent. With the example above, a new client will
mine this much credits in about half an hour, and this target is enough
to sync 500000 blocks (currently about a third of the monero blockchain).
There are three new settings in the wallet:
- credits-target: this is the amount of credits a wallet will try to
reach before stopping mining. The default of 0 means 50000 credits.
- auto-mine-for-rpc-payment-threshold: this controls the minimum
credit rate which the wallet considers worth mining for. If the
daemon credits less than this ratio, the wallet will consider mining
to be not worth it. In the example above, the rate is 0.25
- persistent-rpc-client-id: if set, this allows the wallet to reuse
a client id across runs. This means a public node can tell a wallet
that's connecting is the same as one that connected previously, but
allows a wallet to keep their credit balance from one run to the
other. Since the wallet only mines to keep a small credit balance,
this is not normally worth doing. However, someone may want to mine
on a fast server, and use that credit balance on a low power device
such as a phone. If left unset, a new client ID is generated at
each wallet start, for privacy reasons.
To mine and use a credit balance on two different devices, you can
use the --rpc-client-secret-key switch. A wallet's client secret key
can be found using the new rpc_payments command in the wallet.
Note: anyone knowing your RPC client secret key is able to use your
credit balance.
The wallet has a few new commands too:
- start_mining_for_rpc: start mining to acquire more credits,
regardless of the auto mining settings
- stop_mining_for_rpc: stop mining to acquire more credits
- rpc_payments: display information about current credits with
the currently selected daemon
The node has an extra command:
- rpc_payments: display information about clients and their
balances
The node will forget about any balance for clients which have
been inactive for 6 months. Balances carry over on node restart.
new cli options (RPC ones also apply to wallet):
--p2p-bind-ipv6-address (default = "::")
--p2p-bind-port-ipv6 (default same as ipv4 port for given nettype)
--rpc-bind-ipv6-address (default = "::1")
--p2p-use-ipv6 (default false)
--rpc-use-ipv6 (default false)
--p2p-require-ipv4 (default true, if ipv4 bind fails and this is
true, will not continue even if ipv6 bind
successful)
--rpc-require-ipv4 (default true, description as above)
ipv6 addresses are to be specified as "[xx:xx:xx::xx:xx]:port" except
in the cases of the cli args for bind address. For those the square
braces can be omitted.
add two RSA based ciphers for Windows/depends compatibility
also enforce server cipher ordering
also set ECDH to auto because vtnerd says it is good :)
When built with the depends system, openssl does not include any
cipher on the current whitelist, so add this one, which fixes the
problem, and does seem sensible.
An override for the wallet to daemon connection is provided, but not for
other SSL contexts. The intent is to prevent users from supplying a
system CA as the "user" whitelisted certificate, which is less secure
since the key is controlled by a third party.
This allows "chain" certificates to be used with the fingerprint
whitelist option. A user can get a system-ca signature as backup while
clients explicitly whitelist the server certificate. The user specified
CA can also be combined with fingerprint whitelisting.
The former has the same behavior with single self signed certificates
while allowing the server to have separate short-term authentication
keys with long-term authorization keys.
If the verification mode is `system_ca`, clients will now do hostname
verification. Thus, only certificates from expected hostnames are
allowed when SSL is enabled. This can be overridden by forcible setting
the SSL mode to autodetect.
Clients will also send the hostname even when `system_ca` is not being
performed. This leaks possible metadata, but allows servers providing
multiple hostnames to respond with the correct certificate. One example
is cloudflare, which getmonero.org is currently using.
If SSL is "enabled" via command line without specifying a fingerprint or
certificate, the system CA list is checked for server verification and
_now_ fails the handshake if that check fails. This change was made to
remain consistent with standard SSL/TLS client behavior. This can still
be overridden by using the allow any certificate flag.
If the SSL behavior is autodetect, the system CA list is still checked
but a warning is logged if this fails. The stream is not rejected
because a re-connect will be attempted - its better to have an
unverified encrypted stream than an unverified + unencrypted stream.
Using `verify_peer` on server side requests a certificate from the
client. If no certificate is provided, the server silently accepts the
connection and rejects if the client sends an unexpected certificate.
Adding `verify_fail_if_no_cert` has no affect on client and for server
requires that the peer sends a certificate or fails the handshake. This
is the desired behavior when the user specifies a fingerprint or CA file.
Currently a client must provide a certificate, even if the server is
configured to allow all certificates. This drops that requirement from
the client - unless the server is configured to use a CA file or
fingerprint(s) for verification - which is the standard behavior for SSL
servers.
The "system-wide" CA is not being used as a "fallback" to verify clients
before or after this patch.
Specifying SSL certificates for peer verification does an exact match,
making it a not-so-obvious alias for the fingerprints option. This
changes the checks to OpenSSL which loads concatenated certificate(s)
from a single file and does a certificate-authority (chain of trust)
check instead. There is no drop in security - a compromised exact match
fingerprint has the same worse case failure. There is increased security
in allowing separate long-term CA key and short-term SSL server keys.
This also removes loading of the system-default CA files if a custom
CA file or certificate fingerprint is specified.
