Tutorial
This page provides a step-by-step walkthrough tutorial demonstrating some common uses of Clef. This includes manual approvals and automated rules. Clef is presented both as a standalone general signer with requests made via RPC and also as a backend signer for Etn-sc.
Initialising Clef
First things first, Clef needs to store some data itself. Since that data might be sensitive (passwords, signing rules, accounts), Clef's entire storage is encrypted. To support encrypting data, the first step is to initialize Clef with a random master seed, itself too encrypted with a password:
For readability purposes, we'll remove the WARNING printout, user confirmation and the unlocking of the master seed in the rest of this document.
Remote interactions
This tutorial will use Clef with Etn-sc on testnet. The accounts used will be in the testnet keystore with the path ~/electroneum-sc/testnet/keystore. The tutorial assumes there are two accounts in this keystore. Instructions for creating accounts can be found on the Account managament page. Note that Clef can also interact with hardware wallets, although that is not demonstrated here.
Clef should be started before Etn-sc, otherwise Etn-sc will complain that it cannot find a Clef instance to connect to. Clef should be started with the correct chainid for testnet. Clef itself does not connect to a blockchain, but the chainID parameter is included in the data that is aggregated to form a signature. Clef also needs a path to the correct keystore passed to the --keystore command. A custom path to the config directory can also be provided. This is where the ipc file will be saved which is needed to connect Clef to Etn-sc:
The following logs will be displayed in the console:
Clef starts up in CLI (Command Line Interface) mode by default. Arbitrary remote processes may request account interactions (e.g. sign a transaction), which the user can individually confirm or deny.
The code snippet below shows a request made to Clef via its External API endpoint using NetCat. The request invokes the "account_list" endpoint which lists the accounts in the keystore. This command should be run in a new terminal.
The terminal used to send the command will now hang. This is because the process is awaiting confirmation from Clef. Switching to the Clef console reveals Clef's prompt to the user to confirm or deny the request:
Depending on whether the request is approved or denied, the NetCat process in the other terminal will receive one of the following responses:
or
Apart from listing accounts, a request can be submitted to create a new account, signing transactions and data or recovering signatures. The available methods are documented in the Clef External API Spec and the External API Changelog.
Note, the number of things that can be done from the External API is deliberately small to limit the power of remote calls as much as possible! Clef has an Internal API too for the UI (User Interface) which is much richer and can support custom interfaces on top. But that's out of scope here.
The example above used Clef completely independently of Etn-sc. However, by defining Clef as the signer when Etn-sc is started imposes Clef's request - confirm - result pattern to any interaction with the local Etn-sc node that touches accounts, including requests made using RPC or an attached Javascript console. To demonstrate this, Etn-sc can be started, with Clef as the signer:
With Etn-sc running, open a new terminal and attach a Javascript console:
A simple request to list the accounts in the keystore will cause the Javascript console to hang.
Switching to the Clef terminal reveals that this is because the request is awaiting explicit confirmation from the user. The log is identical to the one shown above, when the same request for account information was made to Clef via Netcat:
In this mode, the user is required to manually confirm every action that touches account data, including querying accounts, signing and sending transactions.
The example below shows an ether transaction between the two accounts in the keystore using eth.sendTransaction in the attached Javascript console.
This example demonstrates the power of Clef much more clearly than the account-listing example. In the Clef terminal, all the details of the transaction are presented to the user so that they can be reviewed before being confirmed. This gives the user an opportunity to review the fine details and make absolutely sure they really want to sign the transaction. eth.sendTransaction returns the following confirmation prompt in the Clef terminal:
Approving this transaction causes Clef to prompt the user to provide the password for the sender account. Providing the password enables the transaction to be signed and sent to Etn-sc for broadcasting to the network. The details of the signed transaction are displayed in the console. Account passwords can also be stored in Clef's encrypted vault so that they do not have to be manually entered - more on this below.
Automatic rules
For most users, manually confirming every transaction is the right way to use Clef because a human-in-the-loop can review every action. However, there are cases when it makes sense to set up some rules which permit Clef to sign a transaction without prompting the user. For example, well defined rules such as:
Auto-approve transactions with
Uniswap v2, with value between0.1and0.5 ETNper 24h periodAuto-approve transactions to address
0xD9C9Cd5f6779558b6e0eD4e6Acf6b1947E7fA1F3as long asgas < 44kandgasPrice < 80Gweican be encoded and interpreted by Clef's built-in ruleset engine.
Rule files
Rules are implemented as Javascript code in js files. The ruleset engine includes the same methods as the JSON_RPC defined in the UI Protocol. The following code snippet demonstrates a rule file that approves a transaction if it satisfies the following conditions:
the recipient is
0xae967917c465db8578ca9024c205720b1a3651a9the value is less than 50000000000000000 wei (0.05 ETN)
and approves account listing if:
the request has arrived via ipc
There are three possible outcomes to this ruleset that are handled in different ways:
"Approve"
Auto-approve request
"Reject"
Auto-approve request
Error
Pass decision to UI for manual approval
Unexpected value
Pass decision to UI for manual approval
Nothing
Pass decision to UI for manual approval
Attestations
Clef will not just accept and run arbitrary scripts - that would create an attack vector because a malicious party could change the rule file. Instead, the user explicitly attests to a rule file, which involves injecting the file's SHA256 hash into Clef's secure store. The following code snippet shows how to calculate a SHA256 hash for a file named rules.js and pass it to Clef. Note that Clef will prompt the user to provide the master password because the Clef store has to be decrypted in order to add the attestation to it.
Once this attestation has been added to the Clef store, it can be used to automatically approve interactions that satisfy the conditions encoded in rules.js in Clef.
Account passwords
The rules described in rules.js above require access to the accounts in the Clef keystore which are protected by user-defined passwords. The signer therefore requires access to these passwords in order to automatically unlock the keystore and sign data and transactions using the accounts.
This is done using clef setpw, passing the account address as the sole argument:
which displays the following in the terminal:
Note that Clef does not really 'unlock' an account, it just abstracts the process of providing the password away from the end-user in specific, predefined scenarios. If an account password exists in the Clef vault and the rule evaluates to "Approve" then Clef decrypts the password, uses it to decrypt the key, does the requested signing and then re-locks the account.
Implementing rules
Clef can be instructed to run an attested rule file simply by passing the path to rules.js to the --rules flag:
The following logs will be displayed in the terminal:
Any request that satisfies the ruleset will now be auto-approved by the rule file, for example the following request to sign a transaction made using the Etn-sc Javascript console (note that the password for account 0xd9c9cd5f6779558b6e0ed4e6acf6b1947e7fa1f3 has already been provided to setpw and the recipient and value comply with the rules in rules.js):
By contrast, the following transactions do not satisfy the rules in rules.js:
These latter two transactions, that do not satisfy the encoded rules in rules.js, are not automatically approved, but instead pass the decision back to the UI for manual approval by the user.
Summary of basic usage
To summarize, the steps required to run Clef with an automated ruleset that requires account access is as follows:
1) Define rules as Javascript and save as a .js file, e.g. rules.js
2) Calculate hash of rule file using sha256sum rules.js
3) Attest the rules in Clef using clef attest <hash>
4) Set account passwords in Clef using clef --setpw <address>
5) Start Clef with rule file enabled using clef --keystore <path-to-keystore> --chainid <chainID> --rules rules.js
6) Make requests directly to Clef using the external API or connect to Etn-sc by passing --signer=<path to clef.ipc> at Etn-sc startup
More rules
Since rules are defined as Javascript code, rulesets of arbitrary complexity can be created and they can impose conditions on any part of a transaction, not only the recipient and value. A simple example is implementing a "whitelist" of recipients where transactions that have those accounts in the to field are automatically signed (for example perhaps transactions between a user's own accounts might be whitelisted):
In addition to addresses and values, other properties of a request can also be incorporated into a ruleset. The example below demonstrates a ruleset for approve_signData imposing the following conditions on a transaction's sender and message data.
The sender must be
0xd9c9cd5f6779558b6e0ed4e6acf6b1947e7fa1f3The transaction message must include the text wen-merge, which is
77656E2D6D65726765in hex.
If these conditions are satisfied then the transaction is auto-approved (assuming the password for 0xd9c9cd5f6779558b6e0ed4e6acf6b1947e7fa1f3 has been provided to setpw).
This file should be saved as a .js file, hashed and attested in Clef:
which returns:
then:
which returns:
Then, Clef can be restarted with the new rules in place:
Finally, a request can be submitted to test that the rules are being applied as expected. Here, Clef is used independently of Etn-sc by making a request via RPC, but the same logic would be imposed if the request was made via a connected Etn-sc node. Some arbitrary text will be included in the message data that includes the term wen-merge. The plaintext clefdemotextthatincludeswen-merge is 636c656664656d6f7465787474686174696e636c7564657377656e2d6d65726765 when represented as a hexadecimal string. This can be passed as data to an account_signData request as follows:
This will be automatically signed, returning a result that looks like the following:
Alternatively, a request that does not include the phrase wen-merge will not automatically approve. For example, the following request passes the hexadecimal string representing the plaintext clefdemotextwithoutspecialtext:
This returns a Request denied message as follows:
Meanwhile, in the output logs in the Clef terminal:
The signer also stores all traffic over the external API in a log file. The last 4 lines shows the two requests and their responses:
More examples, including a ruleset for a rate-limited window, are available on the Clef GitHub and on the Rules page.
Under the hood
The examples on this page have provided step-by-step instructions for various operations using Clef. However, they have not provided much detail as to what is happening under the hood. This section will provide some more details about how Clef organizes itself locally.
Initializing Clef with a master password and providing an account password to clef setpw and attesting a ruleset creates the following files in the directory ~/.clef/ (this path is independent of the paths provided to --keystore and --configdir on startup):
The file masterseed.json includes a json object containing the masterseed which was used to derive the vault directory (in this case 02f90c0603f4f2f60188). The vault is encrypted using a password which is also derived from the masterseed. Inside the vault are two subdirectories:
credentials.json
config.json
Inside credentials.json are the confidential ksp data (standing for "keystore pass" - these are the account passwords used to unlock the keystore).
The config.json file contains encrypted key/value pairs for configuration data. Usually this is only the sha256 hashes of any attested rulesets.
Vault locations map uniquely to masterseeds so that multiple instances of Clef can co-exist each with their own attested rules and their own set of keystore passwords. This is useful for, for example, maintaining separate setups for Mainnet and testnets.
The contents of each of these json files can be viewed using cat and should look something like the following:
For config.json:
and for credentials.json:
Etn-sc integration
This tutorial has bounced back and forth between demonstrating Clef as a standalone tool by making 'manual` JSON RPC requests from the terminal and integrating it as a backend singer for Etn-sc. Using Clef for account management is considered best practise for Etn-sc users because of the additional security benefits it offers over and above what it offered by Etn-sc's built-in accounts module. Clef is far more flexible and composable than Etn-sc's built-in account management tool and can interface directly with hardware wallets, while Apps and wallets can request signatures directly from Clef.
Ultimately, the goal is to deprecate Etn-sc's account management tools completely and replace them with Clef. Until then, users are simply encouraged to choose to use Clef as an optional backend signer for Etn-sc. In addition to the examples on this page, the Getting started tutorial also demonstrates Clef/Etn-sc integration.
Summary
This page includes step-by-step instructions for basic and intermediate uses of Clef, including using it as a standalone app and a backend signer for Etn-sc. Further information is available on our other Clef pages, including Introduction, Setup, Rules, Communication Datatypes and Communication APIs.
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