slumlord

Simple zero-fee SOL flash loan program for paying accounts rent.

Usage

• Borrow transfers slumlord_balance - 1 lamports from slumlord account to specified dst account.
  • Can be called from CPI
• CheckRepaid instruction must be a top-level instruction of the transaction and follow the Borrow instruction
  • User must make sure to return at least the same amount of slumlord_balance - 1 to slumlord account before calling CheckRepaid
  • Idempotent, can be called from CPI. If no flash loan is active, this will just be a successful no-op
• Repay instruction transfers the outstanding loan balance from the specified SystemAccount to slumlord
  • Allows users to easily repay the flash loan without having to read the loan amount from the slumlord account.

If you're composing with slumlord via CPI in your own program, consider making use of CheckRepaid's idempotency and calling it in your program to end the loan where appropriate. This allows your program to be composed with subsequent Borrows while still only requiring a single top-level CheckRepaid instruction at the end.

Setup

Match solana + rust toolchain versions of ellipsislabs/solana:1.16.20 to ensure build close to reproducible build as possible.

sh -c "$(curl -sSfL https://release.solana.com/v1.16.20/install)"
cargo-build-sbf --version && rustc --version

solana-cargo-build-sbf 1.16.20
platform-tools v1.37
rustc 1.68.0 (2c8cc3432 2023-03-06)

Interface Generation

idl.json is a handwritten shank style IDL from which the slumlord_interface crate is generated.

To regenerate the slumlord_interface crate, run in workspace root:

solores \
    -z Slumlord \
    --solana-program-vers "workspace=true" \
    --borsh-vers "workspace=true" \
    --thiserror-vers "workspace=true" \
    --num-derive-vers "workspace=true" \
    --num-traits-vers "workspace=true" \
    --serde-vers "workspace=true" \
    --bytemuck-vers "workspace=true" \
    idl.json

Crate generated with solores 0.5.0

Verifiable build

Using ellipsislabs/solana:1.16.20

Build

In workspace root:

solana-verify build

Verify

In workspace root after build:

solana-verify get-executable-hash target/deploy/slumlord.so

Against mainnet deploy:

solana-verify get-program-hash s1umBj7CEUA6djs6V1c6o2Nym3QrqF4ryKDr1Nm1FKt

Hash

17d20483ee24bb0c1d0fead460f8eee7ccfc9bfcd9c811d295d3a56cc8e96065