clef

README

Clef

Clef can be used to sign transactions and data and is meant as a replacement for geth's account management. This allows DApps not to depend on geth's account management. When a DApp wants to sign data it can send the data to the signer, the signer will then provide the user with context and asks the user for permission to sign the data. If the users grants the signing request the signer will send the signature back to the DApp.

This setup allows a DApp to connect to a remote Ethereum node and send transactions that are locally signed. This can help in situations when a DApp is connected to a remote node because a local Ethereum node is not available, not synchronised with the chain or a particular Ethereum node that has no built-in (or limited) account management.

Clef can run as a daemon on the same machine, or off a usb-stick like usb armory, or a separate VM in a QubesOS type os setup.

Check out

• the tutorial for some concrete examples on how the signer works.
• the setup docs for some information on how to configure it to work on QubesOS or USBArmory.

Command line flags

Clef accepts the following command line options:

COMMANDS:
   init    Initialize the signer, generate secret storage
   attest  Attest that a js-file is to be used
   addpw   Store a credential for a keystore file
   help    Shows a list of commands or help for one command

GLOBAL OPTIONS:
   --loglevel value        log level to emit to the screen (default: 4)
   --keystore value        Directory for the keystore (default: "$HOME/.ethereum/keystore")
   --configdir value       Directory for clef configuration (default: "$HOME/.clef")
   --networkid value       Network identifier (integer, 1=Frontier, 2=Morden (disused), 3=Ropsten, 4=Rinkeby) (default: 1)
   --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.

• 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".

• It should be possible to configure the signer to auto-allow listing (certain) accounts, instead of asking every time.

• Done Upon startup, the signer should spit out some info to the caller (particularly important when executed in stdio-ui-mode), invoking methods with the following info:

  • Version info about the signer
  • Address of API (http/ipc)
  • List of known accounts

• Have a default timeout on signing operations, so that if the user has not answered within e.g. 60 seconds, the request is rejected.

• account_signRawTransaction

• account_bulkSignTransactions([] transactions) should

  • only exist if enabled via config/flag
  • only allow non-data-sending transactions
  • all txs must use the same from-account
  • let the user confirm, showing
    • the total amount
    • the number of unique recipients

• Geth todos

  • The signer should pass the Origin header as call-info to the UI. As of right now, the way that info about the request is put together is a bit of a hack into the http server. This could probably be greatly improved
  • Relay: Geth should be started in geth --external_signer localhost:8550.
  • Currently, the Geth APIs use common.Address in the arguments to transaction submission (e.g to field). This type is 20 bytes, and is incapable of carrying checksum information. The signer uses common.MixedcaseAddress, which retains the original input.
  • The Geth api should switch to use the same type, and relay to-account verbatim to the external api.

• Storage

  • An encrypted key-value storage should be implemented
  • See rules.md for more info about this.

• Another potential thing to introduce is pairing.

  • To prevent spurious requests which users just accept, implement a way to "pair" the caller with the signer (external API).
  • Thus geth/mist/cpp would cryptographically handshake and afterwards the caller would be allowed to make signing requests.
  • This feature would make the addition of rules less dangerous.

• Wallets / accounts. Add API methods for wallets.

Communication

External API

The signer listens to HTTP requests on rpcaddr:rpcport, with the same JSONRPC standard as Geth. The messages are expected to be JSON jsonrpc 2.0 standard.

Some of these call can require user interaction. Clients must be aware that responses may be delayed significantly or may never be received if a users decides to ignore the confirmation request.

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 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 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
• url [string]: location of the keyfile

Sample call

{
  "id": 0,
  "jsonrpc": "2.0",
  "method": "account_new",
  "params": []
}

{
  "id": 0,
  "jsonrpc": "2.0",
  "result": {
    "address": "0xbea9183f8f4f03d427f6bcea17388bdff1cab133",
    "url": "keystore:///my/keystore/UTC--2017-08-24T08-40-15.419655028Z--bea9183f8f4f03d427f6bcea17388bdff1cab133"
  }
}

account_list

List available accounts

List all accounts that this signer currently manages

Arguments

None

Result

• array with account records:
  • account.address [string]: account address that is derived from the generated key
  • account.type [string]: type of the
  • account.url [string]: location of the account

Sample call

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "account_list"
}

{
  "id": 1,
  "jsonrpc": "2.0",
  "result": [
    {
      "address": "0xafb2f771f58513609765698f65d3f2f0224a956f",
      "type": "account",
      "url": "keystore:///tmp/keystore/UTC--2017-08-24T07-26-47.162109726Z--afb2f771f58513609765698f65d3f2f0224a956f"
    },
    {
      "address": "0xbea9183f8f4f03d427f6bcea17388bdff1cab133",
      "type": "account",
      "url": "keystore:///tmp/keystore/UTC--2017-08-24T08-40-15.419655028Z--bea9183f8f4f03d427f6bcea17388bdff1cab133"
    }
  ]
}

account_signTransaction

Sign transactions

Signs a transactions and responds with the signed transaction in RLP encoded form.

Arguments

1. 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
2. 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.

Result

• signed transaction in RLP encoded form [data]

Sample call

{
  "id": 2,
  "jsonrpc": "2.0",
  "method": "account_signTransaction",
  "params": [
    {
      "from": "0x1923f626bb8dc025849e00f99c25fe2b2f7fb0db",
      "gas": "0x55555",
      "gasPrice": "0x1234",
      "input": "0xabcd",
      "nonce": "0x0",
      "to": "0x07a565b7ed7d7a678680a4c162885bedbb695fe0",
      "value": "0x1234"
    }
  ]
}

Response

{
  "jsonrpc": "2.0",
  "id": 67,
  "error": {
    "code": -32000,
    "message": "Request denied"
  }
}

Sample call with ABI-data

{
  "jsonrpc": "2.0",
  "method": "account_signTransaction",
  "params": [
    {
      "from": "0x694267f14675d7e1b9494fd8d72fefe1755710fa",
      "gas": "0x333",
      "gasPrice": "0x1",
      "nonce": "0x0",
      "to": "0x07a565b7ed7d7a678680a4c162885bedbb695fe0",
      "value": "0x0",
      "data": "0x4401a6e40000000000000000000000000000000000000000000000000000000000000012"
    },
    "safeSend(address)"
  ],
  "id": 67
}

Response

{
  "jsonrpc": "2.0",
  "id": 67,
  "result": {
    "raw": "0xf88380018203339407a565b7ed7d7a678680a4c162885bedbb695fe080a44401a6e4000000000000000000000000000000000000000000000000000000000000001226a0223a7c9bcf5531c99be5ea7082183816eb20cfe0bbc322e97cc5c7f71ab8b20ea02aadee6b34b45bb15bc42d9c09de4a6754e7000908da72d48cc7704971491663",
    "tx": {
      "nonce": "0x0",
      "gasPrice": "0x1",
      "gas": "0x333",
      "to": "0x07a565b7ed7d7a678680a4c162885bedbb695fe0",
      "value": "0x0",
      "input": "0x4401a6e40000000000000000000000000000000000000000000000000000000000000012",
      "v": "0x26",
      "r": "0x223a7c9bcf5531c99be5ea7082183816eb20cfe0bbc322e97cc5c7f71ab8b20e",
      "s": "0x2aadee6b34b45bb15bc42d9c09de4a6754e7000908da72d48cc7704971491663",
      "hash": "0xeba2df809e7a612a0a0d444ccfa5c839624bdc00dd29e3340d46df3870f8a30e"
    }
  }
}

Bash example:

#curl -H "Content-Type: application/json" -X POST --data '{"jsonrpc":"2.0","method":"account_signTransaction","params":[{"from":"0x694267f14675d7e1b9494fd8d72fefe1755710fa","gas":"0x333","gasPrice":"0x1","nonce":"0x0","to":"0x07a565b7ed7d7a678680a4c162885bedbb695fe0", "value":"0x0", "data":"0x4401a6e40000000000000000000000000000000000000000000000000000000000000012"},"safeSend(address)"],"id":67}' http://localhost:8550/

{"jsonrpc":"2.0","id":67,"result":{"raw":"0xf88380018203339407a565b7ed7d7a678680a4c162885bedbb695fe080a44401a6e4000000000000000000000000000000000000000000000000000000000000001226a0223a7c9bcf5531c99be5ea7082183816eb20cfe0bbc322e97cc5c7f71ab8b20ea02aadee6b34b45bb15bc42d9c09de4a6754e7000908da72d48cc7704971491663","tx":{"nonce":"0x0","gasPrice":"0x1","gas":"0x333","to":"0x07a565b7ed7d7a678680a4c162885bedbb695fe0","value":"0x0","input":"0x4401a6e40000000000000000000000000000000000000000000000000000000000000012","v":"0x26","r":"0x223a7c9bcf5531c99be5ea7082183816eb20cfe0bbc322e97cc5c7f71ab8b20e","s":"0x2aadee6b34b45bb15bc42d9c09de4a6754e7000908da72d48cc7704971491663","hash":"0xeba2df809e7a612a0a0d444ccfa5c839624bdc00dd29e3340d46df3870f8a30e"}}}

account_sign

Sign data

Signs a chunk of data and returns the calculated signature.

Arguments

• account [address]: account to sign with
• data [data]: data to sign

Result

• calculated signature [data]

Sample call

{
  "id": 3,
  "jsonrpc": "2.0",
  "method": "account_sign",
  "params": [
    "0x1923f626bb8dc025849e00f99c25fe2b2f7fb0db",
    "0xaabbccdd"
  ]
}

Response

{
  "id": 3,
  "jsonrpc": "2.0",
  "result": "0x5b6693f153b48ec1c706ba4169960386dbaa6903e249cc79a8e6ddc434451d417e1e57327872c7f538beeb323c300afa9999a3d4a5de6caf3be0d5ef832b67ef1c"
}

account_ecRecover

Recover address

Derive the address from the account that was used to sign data from the data and signature.

Arguments

• data [data]: data that was signed
• signature [data]: the signature to verify

Result

• derived account [address]

Sample call

{
  "id": 4,
  "jsonrpc": "2.0",
  "method": "account_ecRecover",
  "params": [
    "0xaabbccdd",
    "0x5b6693f153b48ec1c706ba4169960386dbaa6903e249cc79a8e6ddc434451d417e1e57327872c7f538beeb323c300afa9999a3d4a5de6caf3be0d5ef832b67ef1c"
  ]
}

Response

{
  "id": 4,
  "jsonrpc": "2.0",
  "result": "0x1923f626bb8dc025849e00f99c25fe2b2f7fb0db"
}

account_import

Import account

Import a private key into the keystore. The imported key is expected to be encrypted according to the web3 keystore format.

Arguments

• account [object]: key in web3 keystore format (retrieved with account_export)

Result

• imported key [object]:
  • key.address [address]: address of the imported key
  • key.type [string]: type of the account
  • key.url [string]: key URL

Sample call

{
  "id": 6,
  "jsonrpc": "2.0",
  "method": "account_import",
  "params": [
    {
      "address": "c7412fc59930fd90099c917a50e5f11d0934b2f5",
      "crypto": {
        "cipher": "aes-128-ctr",
        "cipherparams": {
          "iv": "401c39a7c7af0388491c3d3ecb39f532"
        },
        "ciphertext": "eb045260b18dd35cd0e6d99ead52f8fa1e63a6b0af2d52a8de198e59ad783204",
        "kdf": "scrypt",
        "kdfparams": {
          "dklen": 32,
          "n": 262144,
          "p": 1,
          "r": 8,
          "salt": "9a657e3618527c9b5580ded60c12092e5038922667b7b76b906496f021bb841a"
        },
        "mac": "880dc10bc06e9cec78eb9830aeb1e7a4a26b4c2c19615c94acb632992b952806"
      },
      "id": "09bccb61-b8d3-4e93-bf4f-205a8194f0b9",
      "version": 3
    },
  ]
}

Response

{
  "id": 6,
  "jsonrpc": "2.0",
  "result": {
    "address": "0xc7412fc59930fd90099c917a50e5f11d0934b2f5",
    "type": "account",
    "url": "keystore:///tmp/keystore/UTC--2017-08-24T11-00-42.032024108Z--c7412fc59930fd90099c917a50e5f11d0934b2f5"
  }
}

account_export

Export account from keystore

Export a private key from the keystore. The exported private key is encrypted with the original passphrase. When the key is imported later this passphrase is required.

Arguments

• account [address]: export private key that is associated with this account

Result

• exported key, see web3 keystore format for more information

Sample call

{
  "id": 5,
  "jsonrpc": "2.0",
  "method": "account_export",
  "params": [
    "0xc7412fc59930fd90099c917a50e5f11d0934b2f5"
  ]
}

Response

{
  "id": 5,
  "jsonrpc": "2.0",
  "result": {
    "address": "c7412fc59930fd90099c917a50e5f11d0934b2f5",
    "crypto": {
      "cipher": "aes-128-ctr",
      "cipherparams": {
        "iv": "401c39a7c7af0388491c3d3ecb39f532"
      },
      "ciphertext": "eb045260b18dd35cd0e6d99ead52f8fa1e63a6b0af2d52a8de198e59ad783204",
      "kdf": "scrypt",
      "kdfparams": {
        "dklen": 32,
        "n": 262144,
        "p": 1,
        "r": 8,
        "salt": "9a657e3618527c9b5580ded60c12092e5038922667b7b76b906496f021bb841a"
      },
      "mac": "880dc10bc06e9cec78eb9830aeb1e7a4a26b4c2c19615c94acb632992b952806"
    },
    "id": "09bccb61-b8d3-4e93-bf4f-205a8194f0b9",
    "version": 3
  }
}

UI API

These methods needs to be implemented by a UI listener.

By starting the signer with the switch --stdio-ui-test, the signer will invoke all known methods, and expect the UI to respond with denials. This can be used during development to ensure that the API is (at least somewhat) correctly implemented. See pythonsigner, which can be invoked via python3 pythonsigner.py test to perform the 'denial-handshake-test'.

All methods in this API uses object-based parameters, so that there can be no mixups of parameters: each piece of data is accessed by key.

See the ui api changelog for information about changes to this API.

OBS! A slight deviation from json standard is in place: every request and response should be confined to a single line. Whereas the json specification allows for linebreaks, linebreaks should not be used in this communication channel, to make things simpler for both parties.

ApproveTx

Invoked when there's a transaction for approval.

Sample call

Here's a method invocation:

curl -i -H "Content-Type: application/json" -X POST --data '{"jsonrpc":"2.0","method":"account_signTransaction","params":[{"from":"0x694267f14675d7e1b9494fd8d72fefe1755710fa","gas":"0x333","gasPrice":"0x1","nonce":"0x0","to":"0x07a565b7ed7d7a678680a4c162885bedbb695fe0", "value":"0x0", "data":"0x4401a6e40000000000000000000000000000000000000000000000000000000000000012"},"safeSend(address)"],"id":67}' http://localhost:8550/

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "ApproveTx",
  "params": [
    {
      "transaction": {
        "from": "0x0x694267f14675d7e1b9494fd8d72fefe1755710fa",
        "to": "0x0x07a565b7ed7d7a678680a4c162885bedbb695fe0",
        "gas": "0x333",
        "gasPrice": "0x1",
        "value": "0x0",
        "nonce": "0x0",
        "data": "0x4401a6e40000000000000000000000000000000000000000000000000000000000000012",
        "input": null
      },
      "call_info": [
          {
            "type": "WARNING",
            "message": "Invalid checksum on to-address"
          },
          {
            "type": "Info",
            "message": "safeSend(address: 0x0000000000000000000000000000000000000012)"
          }
        ],
      "meta": {
        "remote": "127.0.0.1:48486",
        "local": "localhost:8550",
        "scheme": "HTTP/1.1"
      }
    }
  ]
}

The same method invocation, but with invalid data:

curl -i -H "Content-Type: application/json" -X POST --data '{"jsonrpc":"2.0","method":"account_signTransaction","params":[{"from":"0x694267f14675d7e1b9494fd8d72fefe1755710fa","gas":"0x333","gasPrice":"0x1","nonce":"0x0","to":"0x07a565b7ed7d7a678680a4c162885bedbb695fe0", "value":"0x0", "data":"0x4401a6e40000000000000002000000000000000000000000000000000000000000000012"},"safeSend(address)"],"id":67}' http://localhost:8550/

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "ApproveTx",
  "params": [
    {
      "transaction": {
        "from": "0x0x694267f14675d7e1b9494fd8d72fefe1755710fa",
        "to": "0x0x07a565b7ed7d7a678680a4c162885bedbb695fe0",
        "gas": "0x333",
        "gasPrice": "0x1",
        "value": "0x0",
        "nonce": "0x0",
        "data": "0x4401a6e40000000000000002000000000000000000000000000000000000000000000012",
        "input": null
      },
      "call_info": [
          {
            "type": "WARNING",
            "message": "Invalid checksum on to-address"
          },
          {
            "type": "WARNING",
            "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:

{
  "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.

Sample call

{
  "jsonrpc": "2.0",
  "id": 7,
  "method": "ApproveExport",
  "params": [
    {
      "address": "0x0000000000000000000000000000000000000000",
      "meta": {
        "remote": "signer binary",
        "local": "main",
        "scheme": "in-proc"
      }
    }
  ]
}

ApproveListing

Invoked when a request for account listing has been made.

Sample call

{
  "jsonrpc": "2.0",
  "id": 5,
  "method": "ApproveListing",
  "params": [
    {
      "accounts": [
        {
          "type": "Account",
          "url": "keystore:///home/bazonk/.ethereum/keystore/UTC--2017-11-20T14-44-54.089682944Z--123409812340981234098123409812deadbeef42",
          "address": "0x123409812340981234098123409812deadbeef42"
        },
        {
          "type": "Account",
          "url": "keystore:///home/bazonk/.ethereum/keystore/UTC--2017-11-23T21-59-03.199240693Z--cafebabedeadbeef34098123409812deadbeef42",
          "address": "0xcafebabedeadbeef34098123409812deadbeef42"
        }
      ],
      "meta": {
        "remote": "signer binary",
        "local": "main",
        "scheme": "in-proc"
      }
    }
  ]
}

ApproveSignData

Sample call

{
  "jsonrpc": "2.0",
  "id": 4,
  "method": "ApproveSignData",
  "params": [
    {
      "address": "0x123409812340981234098123409812deadbeef42",
      "raw_data": "0x01020304",
      "message": "\u0019Ethereum Signed Message:\n4\u0001\u0002\u0003\u0004",
      "hash": "0x7e3a4e7a9d1744bc5c675c25e1234ca8ed9162bd17f78b9085e48047c15ac310",
      "meta": {
        "remote": "signer binary",
        "local": "main",
        "scheme": "in-proc"
      }
    }
  ]
}

ShowInfo

The UI should show the info to the user. Does not expect response.

Sample call

{
  "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.

{
  "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:

{
  "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
  • The signer provides accounts
• A UI SHOULD, to the best extent possible, use static linking / bundling, so that required libraries are bundled along with the UI.

UI Implementations

There are a couple of implementation for a UI. We'll try to keep this list up to date.

Name	Repo	UI type	No external resources	Blocky support	Verifies permissions	Hash information	No secondary storage	Statically linked	Can modify parameters
QtSigner	https://github.com/holiman/qtsigner/	Python3/QT-based	👍	👍	👍	👍	👍	❌	👍 (partially)
GtkSigner	https://github.com/holiman/gtksigner	Python3/GTK-based	👍	❌	❌	👍	👍	❌	❌
Frame	https://github.com/floating/frame/commits/go-signer	Electron-based	❌	❌	❌	❌	?	❌	❌
Clef UI	https://github.com/kyokan/clef-ui	Golang/QT-based	👍	👍	❌	👍	👍	❌	👍 (approve tx only)

Documentation

Overview

signer is a utility that can be used so sign transactions and arbitrary data.