p2sh – Unable to push script bytes right into a Script builder

The difficulty is with the push_slice API in latest variations of rust-bitcoin (≥ 0.30).

ScriptBuf::builder().push_slice (and Builder::push_slice) now requires T: AsRef for security—it enforces Bitcoin’s push-data limits at compile time the place doable and prevents outsized pushes. &[u8] (what redeem_script.as_bytes() returns) not satisfies that sure immediately.

Repair

Convert the redeem script bytes to PushBytesBuf (the owned model) utilizing TryFrom:

use bitcoin::script::{Builder, PushBytesBuf, ScriptBuf}; // or the total path: bitcoin::blockdata::script::*

// ... your redeem_script development (this half is already right) ...
let redeem_script = Script::builder()
    .push_opcode(OP_PUSHNUM_1)
    .push_key(&pubkey1)
    .push_opcode(OP_PUSHNUM_1)
    .push_opcode(OP_CHECKMULTISIG)
    .into_script();

// Construct the scriptSig for the P2SH spend (1-of-1 multisig redeem script)
let mut script_sig = Builder::new()
    .push_opcode(OP_0)                          // dummy 0 for CHECKMULTISIG
    .push_slice(&signature1.serialize())        // signature (already a legitimate push)
    .push_slice(
        PushBytesBuf::try_from(redeem_script.as_bytes())
            .count on("redeem script too giant to push")  // won't ever fail for regular multisig
    )
    .into_script();

tx.enter[0].script_sig = script_sig;  // or nevertheless you are attaching it

Why this works

• PushBytesBuf::try_from(&[u8]) (or &PushBytes::try_from(&[u8]) should you want a reference) validates the size and offers you a kind that implements AsRef.
• For a 1-of-1 P2MS redeem script the dimensions is tiny (~36 bytes), so the count on/unwrap is protected. In manufacturing you possibly can deal with the PushBytesError if you wish to be additional defensive.
• The ensuing script_sig will likely be a legitimate P2SH unlocking script: <0> (all pushes).

Different one-liners (should you want)

.push_slice(PushBytesBuf::from(redeem_script.as_bytes()))  // panics on >4 GiB (unimaginable)

or

.push_slice(redeem_script.as_bytes().try_into().unwrap())

(utilizing the TryInto impl that PushBytesBuf supplies).

That is the idiomatic approach in present rust-bitcoin. Your redeem script builder and general P2SH stream look right—solely the ultimate push wanted the kind adjustment.