Error : Signature verification failed when using PDA ,,when transfering sol from a PDA to another address

Question

I'm trying to write a code that transfers SOL from a vault(A PDA) to another address and my code looks like this

 pub fn withdraw(ctx: Context<Withdraw>,amount:u64) -> Result<()> {
        let fundraiser_state = &mut ctx.accounts.fundraiser_state;
        if Status::from(fundraiser_state.status)? != Status::CampaignEnded {
            fundraiser_state.status = Status::CampaignEnded.to_u8();
        }
         let fund_starter = ctx.accounts.fund_starter.key();
        //    let(fund_pda,fund_bump) = Pubkey::find_program_address(
        //       &[fund_starter.as_ref()],
        //       ctx.program_id);
        let bump = ctx.bumps.get("vault").unwrap();
         let seeds = &[fund_starter.as_ref(),&[*bump]];
         let signer = [&seeds[..]];
        
        invoke_signed(
            &system_instruction::transfer(
                &ctx.accounts.vault.key(),
                &ctx.accounts.destination.key(),
                amount,
            ),
             &[
                ctx.accounts.vault.to_account_info().clone(),
                ctx.accounts.destination.to_account_info().clone(),
                ctx.accounts.system_program.to_account_info().clone(),
             ],
             &signer,
            )?;

        Ok(())

and here is what the Account structs looks like

#[derive(Accounts)]
pub struct Withdraw <'info> {
    #[account(
        mut,
        seeds = [ACCOUNT_SEED.as_ref()],
        bump ,
        has_one = fund_starter,
    )] 
    fundraiser_state : Account<'info,Fundraising>,
    /// CHECK:
    #[account(
        mut,
        seeds =[fund_starter.key().as_ref()],
        bump 
    )] 
    vault : AccountInfo<'info>,
    /// CHECK :
    fund_starter : AccountInfo<'info>,
    ///CHECK:
    #[account(mut)]
    destination : Signer<'info>,
    system_program : Program<'info,System>,
}

I also write a test for it which brings 'Error: Signature verification failed', and it looks like this,

it("withdraw money from the fundraising", async () => {
    const receivers = (await feePayer());
    const amount  = new anchor.BN(100000);
    //const destinations = anchor.web3.Keypair.generate()
    const [adminPda,_bump] = await anchor.web3.PublicKey.findProgramAddress(
      [Buffer.from(ACCOUNT_SEED)],
      program.programId
    );
    const [vaultPda,vaultBump] = await anchor.web3.PublicKey.findProgramAddress(
      [admin.publicKey.toBuffer()],
      program.programId
    );
    console.log("the vault is :",vaultPda);
    console.log("the bump is :",vaultBump);
    let tx = await program.rpc.withdraw(amount,{
      accounts : {
        fundraiserState : adminPda,
        vault : vaultPda,
        fundStarter : admin.publicKey,
        destination: receivers.publicKey,
        systemProgram : SystemProgram.programId
      },
      //signers : [receivers]
    });
    console.log("tx is : ",tx);

The program builds succesfully but when i run the anchor test commands, i get the "Error: Signature verification failed",

Any help about what im doing wrong will be appreciated.

Answer 1

You can't use system_instruction::transfer to transfer Solana from an account owned by any program other than the System Program.

As you noted, the solution when an account is owned by your program is to borrow the lamports and manually update them on the relevant accounts, while making sure that the total number of lamports in all accounts remains constant.

**ctx.accounts.vault.try_borrow_mut_lamports()? -= amount;
**ctx.accounts.destination.try_borrow_mut_lamports()? += amount;

If the vault was instead a system program account, then you could use system_instruction::transfer

Answer 2

so,after trying so hard,i found this and was able to solve this

**ctx.accounts.vault.try_borrow_mut_lamports()? -= amount;
        **ctx.accounts.destination.try_borrow_mut_lamports()? += amount;

using this instead of the former one(invoke signed) solves the error.