TIER 2 · CPI & PDAs · 4-initialization

REINITIALIZATION

An `init`-style instruction callable twice on the same account resets authority/data to attacker-controlled values. `init_if_needed` is the classic footgun: "needed" is decided by the caller, and a re-init overwrites the admin.

seen in the wild

Reinit bugs killed several early Solana protocols; Anchor 0.25+ made `init_if_needed` require explicit opt-in flags for a reason.

rust · anchor

use anchor_lang::prelude::*;
use borsh::{BorshDeserialize, BorshSerialize};
use std::ops::DerefMut;

declare_id!("Fg6PaFpoGXkYsidMpWTK6W2BeZ7FEfcYkg476zPFsLnS");

#[program]
pub mod initialization_insecure {
    use super::*;

    pub fn initialize(ctx: Context<Initialize>) -> ProgramResult {
        let mut user = User::try_from_slice(&ctx.accounts.user.data.borrow()).unwrap();

        user.authority = ctx.accounts.authority.key();

        let mut storage = ctx.accounts.user.try_borrow_mut_data()?;
        user.serialize(storage.deref_mut()).unwrap();
        Ok(())
    }
}

/*
- reinitialize
- create and dont initialize
- passing previously initialzed accounts from other programs
  (e.g. token program => need to check delegate and authority)
*/

#[derive(Accounts)]
pub struct Initialize<'info> {
    user: AccountInfo<'info>,
    authority: Signer<'info>,
}

#[derive(BorshSerialize, BorshDeserialize)]
pub struct User {
    authority: Pubkey,
}

[ UNLEASH THE PACK ]hunt this class ↗full program + testsgithub ↗

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