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MDL Teller

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Releases & Branches

Last stable release is in master branch, which will match the latest tagged release.

Pull requests should target the develop branch, which is the default branch.

If you clone, make sure you git checkout master to get the latest stable release.

When a new release is published, develop will be merged to master then tagged.

Setup project


Configure teller

The config file can be specified with -c or --config from the command line.

Otherwise, the config file is loaded from the application data directory (defaulted to $HOME/.teller-mdl), or the local working directory.

The application data directory can be changed from the command line with -d or --dir.

The config file uses the toml format.

Teller's default config is config.toml. However, you should not edit this file. It is an example. Copy this config file and edit it for your needs, then use the -c or --config flag to load your custom config.

Description of the config file:

  • debug [bool]: Enable debug logging.
  • profile [bool]: Enable gops profiler.
  • logfile [string]: Log file. It can be an absolute path or be relative to the working directory.
  • dbfile [string]: Database file, saved inside the ~/.teller-mdl folder. Do not use a path.
  • btc_addresses [string]: Filepath of the btc_addresses.json file. See generate BTC addresses.
  • eth_addresses [string]: Filepath of the eth_addresses.json file. See generate ETH addresses.
  • teller.max_bound_addrs [int]: Maximum number addresses allowed to bind per MDL address.
  • teller.bind_enabled [bool]: Disable this to prevent binding of new addresses
  • sky_rpc.address [string]: Host address of the MDL node. See setup MDL node.
  • btc_rpc.server [string]: Host address of the btcd node.
  • btc_rpc.user [string]: btcd RPC username.
  • btc_rpc.pass [string]: btcd RPC password.
  • btc_rpc.cert [string]: btcd RPC certificate file. See setup btcd
  • btc_rpc.cert [bool]: Use a websocket connection instead of HTTP POST requests.
  • btc_scanner.scan_period [duration]: How often to scan for blocks.
  • btc_scanner.initial_scan_height [int]: Begin scanning from this BTC blockchain height.
  • btc_scanner.confirmations_required [int]: Number of confirmations required before sending MDL for a BTC deposit.
  • sky_exchanger.sky_btc_exchange_rate [string]: How much MDL to send per BTC. This can be written as an integer, float, or a rational fraction.
  • sky_exchanger.max_decimals [int]: Number of decimal places to truncate MDL to.
  • eth_rpc.server [string]: Host address of the geth node.
  • eth_rpc.port [string]: Host port of the geth node.
  • eth_scanner.scan_period [duration]: How often to scan for ethereum blocks.
  • eth_scanner.initial_scan_height [int]: Begin scanning from this ETH blockchain height.
  • eth_scanner.confirmations_required [int]: Number of confirmations required before sending MDL for a ETH deposit.
  • sky_exchanger.sky_eth_exchange_rate [string]: How much MDL to send per ETH. This can be written as an integer, float, or a rational fraction.
  • sky_exchanger.wallet [string]: Filepath of the MDL hot wallet. See setup MDL hot wallet.
  • sky_exchanger.tx_confirmation_check_wait [duration]: How often to check for a sent MDL transaction's confirmation.
  • sky_exchanger.send_enabled [bool]: Disable this to prevent sending of coins (all other processing functions normally, e.g.. deposits are received)
  • sky_exchanger.buy_method [string]: Options are "direct" or "passthrough". "direct" will send directly from the wallet. "passthrough" will purchase from an exchange before sending from the wallet.
  • web.behind_proxy [bool]: Set true if running behind a proxy.
  • web.static_dir [string]: Location of static web assets.
  • web.throttle_max [int]: Maximum number of API requests allowed per web.throttle_duration.
  • web.throttle_duration [int]: Duration of throttling, pairs with web.throttle_max.
  • web.http_addr [string]: Host address to expose the HTTP listener on.
  • web.https_addr [string] Host address to expose the HTTPS listener on.
  • web.auto_tls_host [string]: Hostname/domain to install an automatic HTTPS certificate for, using Let's Encrypt.
  • web.tls_cert [string]: Filepath to TLS certificate. Cannot be used with web.auto_tls_host.
  • web.tls_key [string]: Filepath to TLS key. Cannot be used with web.auto_tls_host.
  • [string] Host address of the admin panel.
  • dummy.sender [bool]: Use a fake MDL sender (See "dummy mode").
  • dummy.scanner [bool]: Use a fake BTC scanner (See "dummy mode").
  • dummy.http_addr [bool]: Host address for the dummy scanner and sender API.

Running teller without btcd, geth or mdld

Teller can be run in "dummy mode". It will ignore btcd, geth and mdld. It will still provide addresses via /api/bind and report status with /api/status. but it will not process any real deposits or send real MDL.

See the dummy API for controlling the fake deposits and sends.

Running teller with Docker

Teller can be run with Docker. Update the config.toml, to send the logs to stdout, make sure the logfile key is set to an empty string and that every addesses listen to instead of

logfile = ""
dbfile = "/data"

http_addr = ""

host = ""

http_addr = ""

Then run the following command to start teller:

docker volume create teller-data
docker run -ti --rm \
  -p 4121:4121 \
  -p 7071:7071 \
  -p 7711:7711 \
  -v $PWD/config.toml:/usr/local/teller/config.toml \
  -v $PWD/btc_addresses.json:/usr/local/teller/btc_addresses.json \
  -v $PWD/eth_addresses.json:/usr/local/teller/eth_addresses.json \
  -v teller-data:/data

Access the dashboard: http://localhost:7071.

Generate BTC addresses

Use tool to pregenerate a list of bitcoin addresses in a JSON format parseable by teller:

go run cmd/tool/tool.go -json newbtcaddress $seed $num > addresses.json

Name the addresses.json file whatever you want. Use this file as the value of btc_addresses in the config file.

Generate ETH addresses

Creating a new account

geth account new
Creates a new account and prints the address.

On the console, command (`geth console`) use:

> personal.newAccount("passphrase")
The account is saved in encrypted format. You must remember this passphrase to unlock your account in the future.

For non-interactive use the passphrase can be specified with the --password flag:

geth --password <passwordfile> account new
Note, this is meant to be used for testing only, it is a bad idea to save your password to file or expose in any other way.

then put those address into eth_addresses.json which format like btc_addresses.json

Setup MDL hot wallet

Use the MDL client or CLI to create a wallet. Copy this wallet file to the machine that teller is running on, and specify its path in the config file under sky_exchanger section, wallet parameter.

Load this wallet with a sufficient balance for your OTC.

If the balance is insufficient, the MDL sender will repeatedly try to send coins for a deposit until the balance becomes sufficient.

Run teller

Note: teller must be run from the repo root, in order to serve static content from ./web/dist

make teller

Setup MDL node


Use the MDL daemon's RPC interface address as the value of sky_rpc.address in the config. The default is already configured to so there is no need to set this value if the MDL daemon is run with defaults.

Note: MDL daemon RPC does not use encryption so only run it on the same machine as teller or on a secure LAN

Setup btcd

Follow the instructions from the btcd README to install btcd:

Update your PATH environment to include $GOPATH/bin. The default $GOPATH is ~/go.

Then, run btcd:


This creates a folder ~/.btcd.

Configure btcd

btcd includes a reference conf file:

In ~/.btcd/btcd.conf, edit the following values:

  • txindex - set this to 1.
  • rpcuser - use a long, random, secure string for this value. Set this as the value of btc_rpc.user in the teller conf.
  • rpcpass - use a long, random, secure string for this value. Set this as the value of btc_rpc.pass in the teller conf.

If you are not running btcd on the same machine as teller, you need to change the rpclisten value too. It will need to listen on a public interface. Refer to the sample config link above for instructions on how to configure this value.

Now, run btcd again:


Once the RPC interface is enabled (by setting rpcuser and rpcpass), btcd will generate ~/.btcd/rpc.cert and ~/.btcd/rpc.key.

Obtain btcd RPC certificate

Use the path of the ~/.btcd/rpc.cert file as the value of btc_rpc.cert in teller's config. If teller is running on a different machine, you will need to move it there first. Do not copy ~/.btcd/rpc.key, this is a secret key and is not needed by teller.

Using a reverse proxy to expose teller

SSH reverse proxy method:

# open reverse proxy. -f runs it in the background as daemon, if you don't want this, remove it
ssh -fnNT -R '*:7071:localhost:7071' user@server
# forward port 80 traffic to localhost:7071, since can't bind reverse proxy to port 80 directly
# Change enp2s0 to your interface name. Use ifconfig to see your interfaces.
sudo iptables -t nat -A PREROUTING -i enp2s0 -p tcp --dport 80 -j REDIRECT --to-port 7071

The iptables rule needs to be set permanently. One method for doing this:

sudo apt-get install iptables-persistent
# it will ask if you want to save the current rules, don't save if you have ufw running, it will conflict
# edit /etc/iptables/rules.v4 and /etc/iptables/rules.v6, add the port redirect line
sudo echo "iptables -t nat -A PREROUTING -i enp2s0 -p tcp --dport 80 -j REDIRECT --to-port 7071" >> /etc/iptables/rules.v4
sudo echo "iptables -t nat -A PREROUTING -i enp2s0 -p tcp --dport 80 -j REDIRECT --to-port 7071" >> /etc/iptables/rules.v6

These rules need to be duplicated for another port (e.g. 7072) for the HTTPS listener, when exposing HTTPS.

Setup geth

Follow the instructions from the geth wiki to install geth:

Building geth requires both a Go (version 1.7 or later) and a C compiler.
You can install them using your favourite package manager.
Once the dependencies are installed, run
cd go-ethereum
make geth
copy geth to you system PATH, such as: cp build/bin/geth /usr/bin

Configure geth

specified the following values:

  • --datadir - set this to directory that store ethereum block chain data.
  • --rpc - Enable the HTTP-RPC server
  • --rpcaddr- HTTP-RPC server listening interface (default: "localhost") Set this as the value ofeth_rpc.server` in the teller conf.
  • --rpcport- HTTP-RPC server listening port (default: 8545) Set this as the value of eth_rpc.port in the teller conf.
Please note, offering an API over the HTTP (rpc) or WebSocket (ws) interfaces will give
everyone access to the APIs who can access this interface (DApps, browser tabs, etc). Be
careful which APIs you enable. By default Geth enables all APIs over the IPC (ipc) interface
and only the db, eth, net and web3 APIs over the HTTP and WebSocket interfaces.

Ethereum Api See

you can using a reverse proxy to expose geth rpc port such as Using a reverse proxy to expose teller

Now, run geth:

geth --datadir=xxx

as a daemon
nohup geth --datadir=xxxx > geth.log 2>&1 &


The HTTP API service is provided by the proxy and serve on port 7071 by default.

The API returns JSON for all 200 OK responses.

If the API returns a non-200 response, the response body is the error message, in plain text (not JSON).


Method: POST
Accept: application/json
Content-Type: application/json
URI: /api/bind
Request Body: {
    "mdladdr": "...",
    "coin_type": "BTC"

Binds an MDL address to a BTC/ETH address. An MDL address can be bound to multiple BTC/ETH addresses. The default maximum number of bound addresses is 5.

Coin type specifies which coin deposit address type to generate. Options are: BTC/ETH [TODO: support more coin types].

"buy_method" in the response, indicates the purchasing mode. "direct" buy method is a fixed-price purchase directly from the wallet. "passthrough" but method is a variable-price purchase through an exchange.

Returns 403 Forbidden if teller.bind_enabled is false.


curl -H  -X POST "Content-Type: application/json" -d '{"mdladdr":"...","coin_type":"BTC"}' http://localhost:7071/api/bind


    "deposit_address": "1Bmp9Kv9vcbjNKfdxCrmL1Ve5n7gvkDoNp",
    "coin_type": "BTC",
    "buy_method": "direct"

ETH example:

curl -H  -X POST "Content-Type: application/json" -d '{"mdladdr":"...","coin_type":"ETH"}' http://localhost:7071/api/bind


    "deposit_address": "0x392cded14b8f12cb6cbb1c7922810f4fbd80c3f6",
    "coin_type": "ETH",


Method: GET
Content-Type: application/json
URI: /api/status
Query Args: mdladdr

Returns statuses of an MDL address.

Since a single MDL address can be bound to multiple BTC/ETH addresses the result is in an array. The default maximum number of BTC/ETH addresses per MDL address is 5.

We cannot return the BTC/ETH address for security reasons so they are numbered and timestamped instead.

Possible statuses are:

  • waiting_deposit - MDL address is bound, no deposit seen on BTC/ETH address yet
  • waiting_send - BTC/ETH deposit detected, waiting to send MDL out
  • waiting_confirm - MDL sent out, waiting to confirm the MDL transaction
  • done - MDL transaction confirmed


curl http://localhost:7071/api/status?mdladdr=t5apgjk4LvV9PQareTPzWkE88o1G5A55FW


    "statuses": [
            "seq": 1,
            "updated_at": 1501137828,
            "status": "done"
            "seq": 2,
            "updated_at": 1501128062,
            "status": "waiting_deposit"
            "seq": 3,
            "updated_at": 1501128063,
            "status": "waiting_deposit"


Method: GET
Content-Type: application/json
URI: /api/config

Returns teller configuration.

If "enabled" is false, /api/bind will return 403 Forbidden. /api/status will still work.


curl http://localhost:7071/api/config


    "enabled": true,
    "btc_confirmations_required": 1,
    "eth_confirmations_required": 5,
    "max_bound_addrs": 5,
    "max_decimals": 0,
    "sky_btc_exchange_rate": "123.000000"
    "sky_eth_exchange_rate": "30.000000"

Exchange Status

Method: GET
Content-Type: application/json
URI: /api/exchange-status

Return the exchanger's status. The exchanger's status is the last error seen while trying to send MDL, or nil if no last error was seen. Use this to detect if the OTC is temporarily offline or sold out.

The balance of the OTC wallet is included in the response. The wallet may still be considered "sold out" even if there is a balance remaining. The wallet is considered "sold out" when there are not enough coins in the wallet to satisfy the current purchase, so it is unlikely for the wallet to ever reach exactly 0. For example, if there are 100 coins in the wallet and someone attempts to purchase 200 coins, it will be considered "sold out". In this case, the "error" field will be set to some message string, and the balance will say "100.000000".


curl http://localhost:7071/api/exchange-status


    "error": "",
    "balance": {
        "coins": "100.000000",
        "hours": "100",
    "error": "no unspents to spend",
    "balance": {
        "coins": "0.000000",
        "hours": "0",

Possible statuses are: TODO


A dummy scanner and sender API is available over dummy.http_addr if dummy.scanner or dummy.sender are enabled.


Method: GET, POST
URI: /dummy/scanner/deposit

Adds a deposit to the scanner.


curl http://localhost:4121/dummy/scanner/deposit?addr=1PZ63K3G4gZP6A6E2TTbBwxT5bFQGL2TLB&value=100000000&height=494713&tx=edb29a9b561a8d6a6118eb1f724c87f853bf471d7e4f0e9ccb9e1d340235687b&n=0


Method: GET
URI: /dummy/sender/broadcasts

Lists broadcasted MDL transactions. Note: the dummy sender keeps its records in memory, if teller is restarted, the list of broadcasted transactions is reset.


curl http://localhost:4121/dummy/sender/broadcasts


        "txid": "4fc9743b04c2e3f5e467cde38c0872e3e3ad9ec05d59081ad1a8bd88045635de",
        "outputs": [
                "address": "vpfRRmfPU11HSZjKroskGVnHg4CJ5zJ4ax",
                "coins": "500.000000"
        "confirmed": false
Method: GET, POST
URI: /dummy/sender/confirm

Confirms a broadcasted transaction.


curl http://localhost:4121/dummy/sender/confirm?txid=4fc9743b04c2e3f5e467cde38c0872e3e3ad9ec05d59081ad1a8bd88045635de

Code linting

make install-linters
make lint

Run tests

make test

Database structure

Bucket: used_btc_address
File: addrs/store.go

Maps: `btcaddr -> ""`
Note: Marks a btc address as used
Bucket: used_eth_address
File: addrs/store.go

Maps: `ethaddr -> ""`
Note: Marks a eth address as used
Bucket: exchange_meta
File: exchange/store.go

Note: unused
Bucket: deposit_info
File: exchange/store.go

Maps: btcTx[%tx:%n]/ethTx[%tx:%n] -> exchange.DepositInfo
Note: Maps a btc/eth txid:seq to exchange.DepositInfo struct
Bucket: bind_address_BTC
File: exchange/store.go

Maps: btcaddr -> mdladdr
Note: Maps a btc addr to a sky addr
Bucket: bind_address_ETH
File: exchange/store.go

Maps: ethaddr -> mdladdr
Note: Maps a eth addr to a sky addr
Bucket: sky_deposit_seqs_index
File: exchange/store.go

Maps: mdladdr -> [btcaddrs/ethaddrs]
Note: Maps a sky addr to multiple btc/eth addrs
Bucket: btc_txs
File: exchange/store.go

Maps: btcaddr -> [txs]
Note: Maps a btcaddr to multiple btc txns
Bucket: scan_meta_btc
File: scanner/store.go

Maps: "deposit_addresses" -> [btcaddrs]
Note: Saves list of btc addresss being scanned
Bucket: scan_meta_eth
File: scanner/store.go

Maps: "deposit_addresses" -> [ethaddrs]
Note: Saves list of eth addresss being scanned

Maps: "dv_index_list" -> [ethTx[%tx:%n]][json]
Note: Saves list of eth txid:seq (as JSON)
Bucket: deposit_value
File: scanner/store.go

Maps: btcTx/ethTx[%tx:%n] -> scanner.Deposit
Note: Maps a btc/eth txid:seq to scanner.Deposit struct

Frontend development

See frontend development README

Integration testing

See integration testing checklist