how can i do a CPI in a rust crate with signer from solana program?

Question

What I want to do is use a rust crate in solana program. and a function of the rust crate will do a CPI to another program. how can I sign that CPI with the signer from the main program. Can i pass the signer as argument, can I pass signature separately, or make the crate function return transaction to the solana program and sign that transaction there?

Answer 1

When you're on-chain, signer status is propagated automatically into CPI programs as long as the instruction defines the account as a signer. For example,

• program A takes in account 1 as a signer
• create an instruction into program B in which account 1 is signer
• perform the CPI, and pass in the account info for account 1
• program B gets account 1 as a signer

You can read more about permission and CPIs in the documentation at https://docs.solana.com/developing/programming-model/calling-between-programs#instructions-that-require-privileges

To do a CPI using a dependent crate, you only need a way to create an instruction, the program, and nothing else.