add --hex-entropy flag

Signed-off-by: Ignacio Hagopian <[email protected]>

README.md

@@ -143,7 +143,7 @@ The CLI tool provides an _offline_ subcommand:
 
 You might not need `kzgcli offline download-state` you're pulling the current state out-of-band (e.g: direct download or the sequencer sent it to you). If that isn't the case, you can use it in an environment that has internet access (not necessarily your contribution environment).
 
-The `kzgcli offline contribute` command doesn't require internet access, and will probably be the only command you'll run in your constrained environment. This command also accepts the `--urlrand` flag if you want to pull entropy from an external source of randomness available in your environment.
+The `kzgcli offline contribute` command doesn't require internet access, and will probably be the only command you'll run in your constrained environment. This command also accepts the `--urlrand` and `--hex-entropy` flag if you want to pull entropy from an external source of randomness available in your environment or provided directly to the client, respectively.
 
 The `kzgcli offline send-contribution` command sends the previously generated file by `kzgcli offline contribute` to the sequencer.
 

cmd/kzgcli/main.go

@@ -56,6 +56,7 @@ func init() {
 
 	// Offline commands.
 	offlineContributeCmd.Flags().String("urlrand", "", "Pull entropy from an HTTP endpoint mixed with local CSRNG")
+	offlineContributeCmd.Flags().String("hex-entropy", "", "Hex encoded entropy to be mixed with local CSRNG")
 	offlineSendContributionCmd.Flags().String("session-id", "", "The sesion id as generated in the 'session_id' field in the authentication process")
 
 	rootCmd.AddCommand(offlineCmd)

cmd/kzgcli/offline_contribute.go

@@ -1,10 +1,12 @@
 package main
 
 import (
+	"encoding/hex"
 	"fmt"
 	"io"
 	"log"
 	"os"
+	"strings"
 
 	"github.com/jsign/go-kzg-ceremony-client/contribution"
 	"github.com/jsign/go-kzg-ceremony-client/extrand"
@@ -33,6 +35,18 @@ var offlineContributeCmd = &cobra.Command{
 			fmt.Printf("Got it! (length: %d)\n", len(urlBytes))
 			extRandomness = append(extRandomness, urlBytes)
 		}
+		hexEntropy, err := cmd.Flags().GetString("hex-entropy")
+		if err != nil {
+			log.Fatalf("get --hex-entropy flag value: %s", err)
+		}
+		if hexEntropy != "" {
+			hexEntropy := strings.TrimPrefix(hexEntropy, "0x")
+			hb, err := hex.DecodeString(hexEntropy)
+			if err != nil {
+				log.Fatalf("decoding hex entropy: %s", err)
+			}
+			extRandomness = append(extRandomness, hb)
+		}
 
 		fmt.Printf("Opening and parsing offline current state file...")
 		f, err := os.Open(args[0])