internal/ethapi: default to zero address for calls (ethereum#20702)

This makes eth_call and eth_estimateGas use the zero address
as sender when the "from" parameter is not supplied.

Co-authored-by: Felix Lange <fjl@twurst.com>

internal/ethapi/api.go

@@ -764,17 +764,13 @@ func DoCall(ctx context.Context, b Backend, args CallArgs, blockNrOrHash rpc.Blo
 	if state == nil || err != nil {
 		return nil, 0, false, err
 	}
-	// Set sender address or use a default if none specified
+
+	// Set sender address or use zero address if none specified.
 	var addr common.Address
-	if args.From == nil {
-		if wallets := b.AccountManager().Wallets(); len(wallets) > 0 {
-			if accounts := wallets[0].Accounts(); len(accounts) > 0 {
-				addr = accounts[0].Address
-			}
-		}
-	} else {
+	if args.From != nil {
 		addr = *args.From
 	}
+
 	// Override the fields of specified contracts before execution.
 	for addr, account := range overrides {
 		// Override account nonce.
@@ -906,17 +902,9 @@ func DoEstimateGas(ctx context.Context, b Backend, args CallArgs, blockNrOrHash
 	}
 	cap = hi
 
-	// Set sender address or use a default if none specified
-	if args.From == nil {
-		if wallets := b.AccountManager().Wallets(); len(wallets) > 0 {
-			if accounts := wallets[0].Accounts(); len(accounts) > 0 {
-				args.From = &accounts[0].Address
-			}
-		}
-	}
-	// Use zero-address if none other is available
+	// Use zero address if sender unspecified.
 	if args.From == nil {
-		args.From = &common.Address{}
+		args.From = new(common.Address)
 	}
 	// Create a helper to check if a gas allowance results in an executable transaction
 	executable := func(gas uint64) bool {