feat(cast): wallet sign-auth --self-broadcast

Add a new option `--self-broadcast` to indicate the signed authorization
is intended to be broadcasted by the signing account. This is used to
determine the nonce for the authorization that will be valid for the
broadcasting transaction. If the signing account itself broadcasts the
authorization, the nonce is incremented and the authorization becomes
invalid if it is signed for the `next_nonce` instead of `next_nonce + 1`.

Author: 0xferrous

crates/cast/src/cmd/wallet/mod.rs

@@ -136,6 +136,12 @@ pub enum WalletSubcommands {
         #[arg(long)]
         chain: Option<Chain>,
 
+        /// If set, indicates the authorization will be broadcast by the signing account itself.
+        /// This means the nonce used will be the current nonce + 1 (to account for the
+        /// transaction that will include this authorization).
+        #[arg(long, conflicts_with = "nonce")]
+        self_broadcast: bool,
+
         #[command(flatten)]
         wallet: WalletOpts,
     },
@@ -542,13 +548,20 @@ impl WalletSubcommands {
                     sh_println!("0x{}", hex::encode(sig.as_bytes()))?;
                 }
             }
-            Self::SignAuth { rpc, nonce, chain, wallet, address } => {
+            Self::SignAuth { rpc, nonce, chain, wallet, address, self_broadcast } => {
                 let wallet = wallet.signer().await?;
                 let provider = utils::get_provider(&rpc.load_config()?)?;
                 let nonce = if let Some(nonce) = nonce {
                     nonce
                 } else {
-                    provider.get_transaction_count(wallet.address()).await?
+                    let current_nonce = provider.get_transaction_count(wallet.address()).await?;
+                    if self_broadcast {
+                        // When self-broadcasting, the authorization nonce needs to be +1
+                        // because the transaction itself will consume the current nonce
+                        current_nonce + 1
+                    } else {
+                        current_nonce
+                    }
                 };
                 let chain_id = if let Some(chain) = chain {
                     chain.id()
@@ -998,4 +1011,17 @@ mod tests {
             _ => panic!("expected WalletSubcommands::ChangePassword"),
         }
     }
+
+    #[test]
+    fn wallet_sign_auth_nonce_and_self_broadcast_conflict() {
+        let result = WalletSubcommands::try_parse_from([
+            "foundry-cli",
+            "sign-auth",
+            "0xDeaDbeefdEAdbeefdEadbEEFdeadbeEFdEaDbeeF",
+            "--nonce",
+            "42",
+            "--self-broadcast",
+        ]);
+        assert!(result.is_err(), "expected error when both --nonce and --self-broadcast are provided");
+    }
 }

crates/cast/tests/cli/main.rs

@@ -615,6 +615,85 @@ casttest!(wallet_sign_auth, |_prj, cmd| {
 "#]]);
 });
 
+// tests that `cast wallet sign-auth --self-broadcast` uses nonce + 1
+casttest!(wallet_sign_auth_self_broadcast, async |_prj, cmd| {
+    use alloy_rlp::Decodable;
+    use alloy_signer_local::PrivateKeySigner;
+
+    let (_, handle) =
+        anvil::spawn(NodeConfig::test().with_hardfork(Some(EthereumHardfork::Prague.into()))).await;
+    let endpoint = handle.http_endpoint();
+
+    let private_key = "0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80";
+    let signer: PrivateKeySigner = private_key.parse().unwrap();
+    let signer_address = signer.address();
+    let delegate_address = address!("0x70997970C51812dc3A010C7d01b50e0d17dc79C8");
+
+    // Get the current nonce from the RPC
+    let provider = ProviderBuilder::new().connect_http(endpoint.parse().unwrap());
+    let current_nonce = provider.get_transaction_count(signer_address).await.unwrap();
+
+    // First, get the auth without --self-broadcast (should use current nonce)
+    let output_normal = cmd
+        .args([
+            "wallet",
+            "sign-auth",
+            "--private-key",
+            private_key,
+            "--rpc-url",
+            &endpoint,
+            &delegate_address.to_string(),
+        ])
+        .assert_success()
+        .get_output()
+        .stdout_lossy()
+        .trim()
+        .to_string();
+
+    // Then, get the auth with --self-broadcast (should use current nonce + 1)
+    let output_self_broadcast = cmd
+        .cast_fuse()
+        .args([
+            "wallet",
+            "sign-auth",
+            "--private-key",
+            private_key,
+            "--rpc-url",
+            &endpoint,
+            "--self-broadcast",
+            &delegate_address.to_string(),
+        ])
+        .assert_success()
+        .get_output()
+        .stdout_lossy()
+        .trim()
+        .to_string();
+
+    // The outputs should be different due to different nonces
+    assert_ne!(
+        output_normal, output_self_broadcast,
+        "self-broadcast should produce different signature due to nonce + 1"
+    );
+
+    // Decode the RLP to verify the nonces
+    let normal_bytes = hex::decode(output_normal.strip_prefix("0x").unwrap()).unwrap();
+    let self_broadcast_bytes =
+        hex::decode(output_self_broadcast.strip_prefix("0x").unwrap()).unwrap();
+
+    let normal_auth =
+        alloy_eips::eip7702::SignedAuthorization::decode(&mut normal_bytes.as_slice()).unwrap();
+    let self_broadcast_auth =
+        alloy_eips::eip7702::SignedAuthorization::decode(&mut self_broadcast_bytes.as_slice())
+            .unwrap();
+
+    assert_eq!(normal_auth.nonce(), current_nonce, "normal auth should have current nonce");
+    assert_eq!(
+        self_broadcast_auth.nonce(),
+        current_nonce + 1,
+        "self-broadcast auth should have current nonce + 1"
+    );
+});
+
 // tests that `cast wallet list` outputs the local accounts
 casttest!(wallet_list_local_accounts, |prj, cmd| {
     let keystore_path = prj.root().join("keystore");