--lightkdf Reduce key-derivation RAM & CPU usage at some expense of KDF strength
--nousb Disables monitoring for and managing USB hardware wallets
--rpcaddr value HTTP-RPC server listening interface (default: "localhost")
--rpcport value HTTP-RPC server listening port (default: 8550)
--signersecret value A file containing the password used to encrypt signer credentials, e.g. keystore credentials and ruleset hash
--4bytedb value File containing 4byte-identifiers (default: "./4byte.json")
--4bytedb-custom value File used for writing new 4byte-identifiers submitted via API (default: "./4byte-custom.json")
--auditlog value File used to emit audit logs. Set to "" to disable (default: "audit.log")
--rules value Enable rule-engine (default: "rules.json")
--stdio-ui Use STDIN/STDOUT as a channel for an external UI. This means that an STDIN/STDOUT is used for RPC-communication with a e.g. a graphical user interface, and can be used when the signer is started by an external process.
--stdio-ui-test Mechanism to test interface between signer and UI. Requires 'stdio-ui'.
--help, -h show help
--version, -v print the version
```
Example:
```
signer -keystore /my/keystore -chainid 4
```
## Security model
The security model of the signer is as follows:
* One critical component (the signer binary / daemon) is responsible for handling cryptographic operations: signing, private keys, encryption/decryption of keystore files.
* The signer binary has a well-defined 'external' API.
* The 'external' API is considered UNTRUSTED.
* The signer binary also communicates with whatever process that invoked the binary, via stdin/stdout.
* This channel is considered 'trusted'. Over this channel, approvals and passwords are communicated.
The general flow for signing a transaction using e.g. geth is as follows:
In this case, `geth` would be started with `--externalsigner=http://localhost:8550` and would relay requests to `eth.sendTransaction`.
## TODOs
Some snags and todos
* [ ] The signer should take a startup param "--no-change", for UIs that do not contain the capability
to perform changes to things, only approve/deny. Such a UI should be able to start the signer in
a more secure mode by telling it that it only wants approve/deny capabilities.
* [x] It would be nice if the signer could collect new 4byte-id:s/method selectors, and have a
secondary database for those (`4byte_custom.json`). Users could then (optionally) submit their collections for
inclusion upstream.
* It should be possible to configure the signer to check if an account is indeed known to it, before
passing on to the UI. The reason it currently does not, is that it would make it possible to enumerate
accounts if it immediately returned "unknown account".
* [x] It should be possible to configure the signer to auto-allow listing (certain) accounts, instead of asking every time.
* [x] Done Upon startup, the signer should spit out some info to the caller (particularly important when executed in `stdio-ui`-mode),
The External API is **untrusted** : it does not accept credentials over this api, nor does it expect
that requests have any authority.
### UI API
The signer has one native console-based UI, for operation without any standalone tools.
However, there is also an API to communicate with an external UI. To enable that UI,
the signer needs to be executed with the `--stdio-ui` option, which allocates the
`stdin`/`stdout` for the UI-api.
An example (insecure) proof-of-concept of has been implemented in `pythonsigner.py`.
The model is as follows:
* The user starts the UI app (`pythonsigner.py`).
* The UI app starts the `signer` with `--stdio-ui`, and listens to the
process output for confirmation-requests.
* The `signer` opens the external http api.
* When the `signer` receives requests, it sends a `jsonrpc` request via `stdout`.
* The UI app prompts the user accordingly, and responds to the `signer`
* The `signer` signs (or not), and responds to the original request.
## External API
See the [external api changelog](extapi_changelog.md) for information about changes to this API.
### Encoding
- number: positive integers that are hex encoded
- data: hex encoded data
- string: ASCII string
All hex encoded values must be prefixed with `0x`.
## Methods
### account_new
#### Create new password protected account
The signer will generate a new private key, encrypts it according to [web3 keystore spec](https://github.com/ethereum/wiki/wiki/Web3-Secret-Storage-Definition) and stores it in the keystore directory.
The client is responsible for creating a backup of the keystore. If the keystore is lost there is no method of retrieving lost accounts.
#### Arguments
None
#### Result
- address [string]: account address that is derived from the generated key
Signs a transactions and responds with the signed transaction in RLP encoded form.
#### Arguments
2. transaction object:
-`from` [address]: account to send the transaction from
-`to` [address]: receiver account. If omitted or `0x`, will cause contract creation.
-`gas` [number]: maximum amount of gas to burn
-`gasPrice` [number]: gas price
-`value` [number:optional]: amount of Wei to send with the transaction
-`data` [data:optional]: input data
-`nonce` [number]: account nonce
3. method signature [string:optional]
- The method signature, if present, is to aid decoding the calldata. Should consist of `methodname(paramtype,...)`, e.g. `transfer(uint256,address)`. The signer may use this data to parse the supplied calldata, and show the user. The data, however, is considered totally untrusted, and reliability is not expected.
"message": "Transaction data did not match ABI-interface: WARNING: Supplied data is stuffed with extra data. \nWant 0000000000000002000000000000000000000000000000000000000000000012\nHave 0000000000000000000000000000000000000000000000000000000000000012\nfor method safeSend(address)"
}
],
"meta": {
"remote": "127.0.0.1:48492",
"local": "localhost:8550",
"scheme": "HTTP/1.1"
}
}
]
}
```
One which has missing `to`, but with no `data`:
```json
{
"jsonrpc": "2.0",
"id": 3,
"method": "ApproveTx",
"params": [
{
"transaction": {
"from": "",
"to": null,
"gas": "0x0",
"gasPrice": "0x0",
"value": "0x0",
"nonce": "0x0",
"data": null,
"input": null
},
"call_info": [
{
"type": "CRITICAL",
"message": "Tx will create contract with empty code!"
}
],
"meta": {
"remote": "signer binary",
"local": "main",
"scheme": "in-proc"
}
}
]
}
```
### ApproveExport
Invoked when a request to export an account has been made.
The UI should show the info to the user. Does not expect response.
#### Sample call
```json
{
"jsonrpc": "2.0",
"id": 9,
"method": "ShowInfo",
"params": [
{
"text": "Tests completed"
}
]
}
```
### ShowError
The UI should show the info to the user. Does not expect response.
```json
{
"jsonrpc": "2.0",
"id": 2,
"method": "ShowError",
"params": [
{
"text": "Testing 'ShowError'"
}
]
}
```
### OnApproved
`OnApprovedTx` is called when a transaction has been approved and signed. The call contains the return value that will be sent to the external caller. The return value from this method is ignored - the reason for having this callback is to allow the ruleset to keep track of approved transactions.
When implementing rate-limited rules, this callback should be used.
TLDR; Use this method to keep track of signed transactions, instead of using the data in `ApproveTx`.
### OnSignerStartup
This method provide the UI with information about what API version the signer uses (both internal and external) aswell as build-info and external api,
in k/v-form.
Example call:
```json
{
"jsonrpc": "2.0",
"id": 1,
"method": "OnSignerStartup",
"params": [
{
"info": {
"extapi_http": "http://localhost:8550",
"extapi_ipc": null,
"extapi_version": "2.0.0",
"intapi_version": "1.2.0"
}
}
]
}
```
### Rules for UI apis
A UI should conform to the following rules.
* A UI MUST NOT load any external resources that were not embedded/part of the UI package.
* For example, not load icons, stylesheets from the internet
* Not load files from the filesystem, unless they reside in the same local directory (e.g. config files)
* A Graphical UI MUST show the blocky-identicon for ethereum addresses.
* A UI MUST warn display approproate warning if the destination-account is formatted with invalid checksum.
* A UI MUST NOT open any ports or services
* The signer opens the public port
* A UI SHOULD verify the permissions on the signer binary, and refuse to execute or warn if permissions allow non-user write.
* A UI SHOULD inform the user about the `SHA256` or `MD5` hash of the binary being executed
* A UI SHOULD NOT maintain a secondary storage of data, e.g. list of accounts
