the0takuc0mrade.dev🦀

I have been mentoring and unblocking developers on Solana for over two years and, deriving/enforcing secure Program Derived Addresses (PDA) is usually by far the most difficult concept for new Solana devs to understand. So let's break it down: What are PDAs? These are deterministically derived addresses that lies off the Ed25519 elliptic curve and is derived from a set of seeds, a program ID, a bump seed and SHA-256. They do not have a corresponding private key like regular keypair accounts. PDAs by nature of their design have a secure derivation mechanism, however, several security vectors lies in the way a program derive, validates, initializes and authorize access to a PDA. PDAs are very useful for program-controlled authority in vaults, escrow accounts, state account and token authorities as well. So if PDAs are very secure, what could possibly go wrong? Well..here is the thing, there are a lot of things that can go wrong but not at the underlying PDA cryptographic layer. For example, say a program derives a user vault, it is very important to use the canonical bump when deriving a PDA to avoid having multiple valid off-curve addresses for the seeds. Failure to use the canonical bump means your program can accept an arbitrary bump supplied by the user and gives an attacker window to create or substitute an alternative vault address. There's also the possibility of seed collision and account substitution attacks but most of these comes from irresponsible validations. Can someone steal funds from a PDA? Actually no- at least not by simply knowing its address as a PDA does not have a private key. The only way this can happen is if the program controlling the PDA has a vulnerability. So if you are building Solana programs, I'd advise you consistently enforce the following practices: 1. Always validate PDAs against canonical bumps. 2. Use domain-separated seeds 3. ALWAYS validate account ownership independent of PDA derivation. This is a very important check, because PDA derivation authority and account ownership are not the same thing. 4. Validate all your signers (explicitly). 5. Validate all CPI target accounts. 6. As much as possible, keep PDA signing privileges minimal. 7. Protect upgrade authority at all cost! Last thing you need is an upgradeable program changing the logic controlling its PDAs. PDAs are an interesting design that is unique to Solana and builds on its account-centric architecture and enables user-defined state easier to manage while providing a program level authority to users, unlocking many useful applications and features.