Underpruning can produce anti-DOS error from elementsd #391

    Error: Broadcast failed with HTTP 400 for http://127.0.0.1:42415/tx: sendrawtransaction RPC error -26: non-mandatory-script-verify-flag (Anti-DOS check failed)

diff --git a/crates/sdk/src/program/core.rs b/crates/sdk/src/program/core.rs
index d683f35..1cad6c4 100644
--- a/crates/sdk/src/program/core.rs
+++ b/crates/sdk/src/program/core.rs
@@ -162,7 +162,23 @@ impl ProgramTrait for Program {
 
         let env = self.get_env(pst, input_index, network)?;
 
-        let pruned = satisfied.redeem().prune_with_tracker(&env, &mut tracker)?;
+        let mut pruned = satisfied.redeem().prune_with_tracker(&env, &mut tracker)?;
+
+        // EXPERIMENTAL: opt-in re-pruning to test whether a single `prune()`
+        // call is leaving the submitted bytecode incompletely pruned (see
+        // the chess.simf Anti-DOS investigation). `prune()`'s own doc
+        // comment warns that pruning an already-pruned program "is not
+        // sound" in general, so this is gated behind an env var rather than
+        // being unconditional -- it's here to let us test the real effect
+        // against a real node, not as a blessed fix.
+        if std::env::var("SMPLX_DOUBLE_PRUNE").is_ok() {
+            // Self-verifying: prints unconditionally when this branch fires,
+            // so it's visible whether the env var actually reached this
+            // process at all -- see SETUP_v10.md's propagation-chain caveat.
+            // No need to trust that it did; this line settles it.
+            eprintln!("[SMPLX_DOUBLE_PRUNE active] re-pruning before serialization");
+            pruned = pruned.prune(&env)?;
+        }
 
         if GlobalConfig::is_max_verbose() {
             ProgramLogger::buffer_cost_log(&pruned);

//! Run once WITHOUT `SMPLX_DOUBLE_PRUNE` set: expect this to fail with
//! "Anti-DOS check failed".
//! Run again WITH `SMPLX_DOUBLE_PRUNE=1`: expect it to pass.

use simplex::simplicityhl::elements::Script;
use simplex::simplicityhl::{Arguments, WitnessValues};
use simplex::program::{ArgumentsTrait, Program, WitnessTrait};
use simplex::transaction::{FinalTransaction, PartialInput, ProgramInput, RequiredSignature};

/// A witness with no declared values at all -- for `minimal_repro_anti_dos_synthetic`
/// below.
#[derive(Clone)]
struct NoWitness;

impl WitnessTrait for NoWitness {
    fn build_witness(&self) -> WitnessValues {
        WitnessValues::default()
    }
}

#[derive(Clone)]
struct NoArguments;

impl ArgumentsTrait for NoArguments {
    fn build_arguments(&self) -> Arguments {
        Arguments::default()
    }
}

/// Even smaller than the prior repro: built directly from the four
/// necessary ingredients isolated by bisection (a 2-level nested match,
/// the *same* function called twice, output-feeds-input chaining,
/// the threaded value `Option`-wrapped for early exit).
const SYNTHETIC_SOURCE: &str = r#"
fn nested(a: bool, b: bool) -> bool {
    match a {
        false => match b {
            false => false,
            true => true,
        },
        true => false,
    }
}

fn step(cur: Option<bool>) -> (bool, Option<bool>) {
    match cur {
        None => (false, None),
        Some(x: bool) => match nested(x, true) {
            false => (false, Some(true)),
            true => (true, None),
        },
    }
}

fn main() {
    let (f0, n0): (bool, Option<bool>) = step(Some(false));
    let (f1, _n1): (bool, Option<bool>) = step(n0);
    let hit: bool = match f0 {
        true => f0,
        false => f1,
    };
    assert!(hit);
}
"#;

fn get_synthetic_program(context: &simplex::TestContext) -> (Program, Script) {
    let signer = context.get_default_signer();
    let program =
        Program::new(SYNTHETIC_SOURCE, Box::new(NoArguments)).with_taproot_pubkey(signer.get_schnorr_public_key());
    let script = program.get_script_pubkey(context.get_network());
    (program, script)
}

#[simplex::test]
fn most_minimal_repro_anti_dos(context: simplex::TestContext) -> anyhow::Result<()> {
    let signer = context.get_default_signer();
    let provider = context.get_default_provider();

    let (program, script) = get_synthetic_program(&context);

    let tx_receipt = signer.send(script.clone(), 50_000)?;
    tx_receipt.wait()?;

    let utxos = provider.fetch_scripthash_utxos(&script)?;

    let mut ft = FinalTransaction::new();
    ft.add_program_input(
        PartialInput::new(utxos[0].clone()),
        ProgramInput::new(Box::new(program.clone()), Box::new(NoWitness)),
        RequiredSignature::None,
    );

    signer.broadcast(&ft)?;
    Ok(())
}

    Error: Broadcast failed with HTTP 400 for http://127.0.0.1:35821/tx: sendrawtransaction RPC error -26: non-mandatory-script-verify-flag (Anti-DOS check failed)

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