status-im/status-go

package api

import (
    "bytes"
    "encoding/hex"
    "strconv"
    "strings"

    "github.com/status-im/status-go/common"
    "github.com/status-im/status-go/eth-node/crypto"
)

// RunAsync runs the specified function asynchronously.
func RunAsync(f func() error) <-chan error {
    resp := make(chan error, 1)
    go func() {
        defer common.LogOnPanic()
        err := f()
        resp <- err
        close(resp)
    }()
    return resp
}

// HashMessage calculates the hash of a message to be safely signed by the keycard
// The hash is calulcated as
//
//    keccak256("\x19Ethereum Signed Message:\n"${message length}${message}).
//
// This gives context to the signed message and prevents signing of transactions.
func HashMessage(message string) ([]byte, error) {
    buf := bytes.NewBufferString("\x19Ethereum Signed Message:\n")
    if value, ok := decodeHexStrict(message); ok {
        if _, err := buf.WriteString(strconv.Itoa(len(value))); err != nil {
            return nil, err
        }
        if _, err := buf.Write(value); err != nil {
            return nil, err
        }
    } else {
        if _, err := buf.WriteString(strconv.Itoa(len(message))); err != nil {
            return nil, err
        }
        if _, err := buf.WriteString(message); err != nil {
            return nil, err
        }
    }

    return crypto.Keccak256(buf.Bytes()), nil
}

func decodeHexStrict(s string) ([]byte, bool) {
    if !strings.HasPrefix(s, "0x") {
        return nil, false
    }

    value, err := hex.DecodeString(s[2:])
    if err != nil {
        return nil, false
    }

    return value, true
}