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This guide demonstrates how to integrate Session Keys into your Solana Anchor programs, using a simple counter program as an example.

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Installation

First, add the session-keys crate to your Cargo.toml: 
[dependencies]
session-keys = { version = "1.0.0", features = ["no-entrypoint"] }
Or use the cargo command: 
cargo add session-keys --features no-entrypoint

​
Usage

  1. Importing session-keys:
   use session_keys::{SessionError, SessionToken, session_auth_or, Session};
This line imports the necessary components from the session-keys crate.
  1. Deriving the Session trait:
   #[derive(Accounts, Session)]
   pub struct Increment<'info> {
     #[account(
        mut, 
        seeds = [ COUNTER_SEED, counter.authority.key().as_ref() ], 
        bump
     )]
     pub counter: Account<'info, Counter>,
     ...
   }
The Session trait is derived on the Increment struct, enabling session functionality.
  1. Defining the session token account:
   #[session(
       signer = signer,
       authority = counter.authority.key() 
   )]
   pub session_token: Option<Account<'info, SessionToken>>,
This defines an optional SessionToken account, specifying the signer and authority for the session.
  • session_token.authority: account which created the session token
  • counter.authority.key(): account which created the counter The authority condition checks if the session token is created by the same user as the counter.
  1. Using the session_auth_or macro:
   #[session_auth_or(
       ctx.accounts.counter.authority.key() == ctx.accounts.signer.key(),
       SessionError::InvalidToken
   )]
   pub fn increment(ctx: Context<Increment>) -> Result<()> {
       ...
   }
This macro is applied to the increment function. It checks for a valid session token, or if not present, verifies that the signer is the counter’s authority.

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Full Example

Here’s a complete example of a counter program using session keys. Each user gets his own counter account, so we can show how authentication is done with session keys. 
use anchor_lang::prelude::*;
use session_keys::{SessionError, SessionToken, session_auth_or, Session};

declare_id!("...");
const COUNTER_SEED: &[u8] = b"counter";

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

    pub fn initialize(ctx: Context<Initialize>) -> Result<()> {
        let counter: &mut Counter = &mut ctx.accounts.counter;
        counter.count = 0;
        counter.authority = *ctx.accounts.owner.key;
        Ok(())
    }

    #[session_auth_or(
        ctx.accounts.counter.authority.key() == ctx.accounts.signer.key(),
        SessionError::InvalidToken
    )]
    pub fn increment(ctx: Context<Increment>) -> Result<()> {
        let counter: &mut Counter = &mut ctx.accounts.counter;
        counter.count += 1;
        Ok(())
    }
}

#[derive(Accounts)]
pub struct Initialize<'info> {
    #[account(
        init, 
        payer = owner, 
        space = Counter::INIT_SPACE + 8 , 
        seeds = [ COUNTER_SEED, owner.key().as_ref() ], bump
    )]
    pub counter: Account<'info, Counter>,
    #[account(mut)]
    pub owner: Signer<'info>,
    pub system_program: Program<'info, System>,
}

#[derive(Accounts, Session)]
pub struct Increment<'info> {
    #[account(
        mut, 
        seeds = [ COUNTER_SEED, counter.authority.key().as_ref() ], 
        bump
    )]
    pub counter: Account<'info, Counter>,    
    #[session(
        signer = signer,
        authority = counter.authority.key() 
    )]
    pub session_token: Option<Account<'info, SessionToken>>,
    #[account(mut)]
    pub signer: Signer<'info>,
}

#[account]
#[derive(InitSpace)]
pub struct Counter {
    pub authority: Pubkey,
    pub count: u64,
}

​
Tests

Here’s an example of how to test the counter program with session keys: 
import * as anchor from "@project-serum/anchor";
import { Program } from "@project-serum/anchor";
import { CounterSession } from "../target/types/counter_session";
import { createSessionToken } from "@session-keys/anchor";
import { expect } from "chai";

describe("counter_session", () => {
  const provider = anchor.AnchorProvider.env();
  anchor.setProvider(provider);

  const program = anchor.workspace.CounterSession as Program<CounterSession>;

  let counterPDA: anchor.web3.PublicKey;
  let sessionToken: anchor.web3.PublicKey;

  it("Initializes the counter", async () => {
    const [pda] = await anchor.web3.PublicKey.findProgramAddress(
      [Buffer.from("counter"), provider.wallet.publicKey.toBuffer()],
      program.programId
    );
    counterPDA = pda;

    await program.methods
      .initialize()
      .accounts({
        counter: counterPDA,
        owner: provider.wallet.publicKey,
        systemProgram: anchor.web3.SystemProgram.programId,
      })
      .rpc();

    const counterAccount = await program.account.counter.fetch(counterPDA);
    expect(counterAccount.count).to.equal(0);
    expect(counterAccount.authority.toString()).to.equal(provider.wallet.publicKey.toString());
  });

  it("Increments the counter without session", async () => {
    await program.methods
      .increment()
      .accounts({
        counter: counterPDA,
        signer: provider.wallet.publicKey,
      })
      .rpc();

    const counterAccount = await program.account.counter.fetch(counterPDA);
    expect(counterAccount.count).to.equal(1);
  });

  it("Increments the counter with session token", async () => {
    await program.methods
      .increment()
      .accounts({
        counter: counterPDA,
        sessionToken: sessionToken,
        signer: provider.wallet.publicKey,
      })
      .rpc();

    const counterAccount = await program.account.counter.fetch(counterPDA);
    expect(counterAccount.count).to.equal(2);
  });

  it("fails to increment with wrong session token owner", async () => {
    const user = anchor.web3.Keypair.generate();
    await topUp(user);
  
    let counterPDA = await createCounterPDA(user.publicKey);    
    await createCounter(user);

    const secondUser = anchor.web3.Keypair.generate();
    await topUp(secondUser);
    const { sessionSigner, sessionToken } = await createSessionSigner(secondUser);    
    
    try {
      await increment_with_session(counterPDA, sessionSigner, sessionToken);
      assert(false, "Expected to fail");
    } catch (err) {}

    const counterData = await program.account.counter.fetch(counterPDA);
    assert(counterData.count.eq(new anchor.BN(0)));
  });
});
This test suite demonstrates initializing the counter, incrementing it without a session, creating a session token, and then incrementing with the session token. The last test is important, as it ensures that only the owner of the counter can increment it.

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Testing locally

To test it locally with solana-test-validator, you need to start it with the session keys program and account.
  1. Make sure your Solana CLI points to DEVNET:
solana config set --url https://api.devnet.solana.com
  1. Dump Session Keys program to local file:
solana program dump KeyspM2ssCJbqUhQ4k7sveSiY4WjnYsrXkC8oDbwde5 ./session-keys.so
  1. Start solana-test-validator with session keys program and account:
-r - reset the ledger to genesis -ud - URL for Solana’s JSON RPC or moniker (-ud = DEVNET) --clone - Copy an account from the cluster --bpf-program - add a SBF program to the genesis configuration 
solana-test-validator -ud --clone KeyspM2ssCJbqUhQ4k7sveSiY4WjnYsrXkC8oDbwde5 -r --bpf-program KeyspM2ssCJbqUhQ4k7sveSiY4WjnYsrXkC8oDbwde5 ./session-keys.so
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