Forbid direct invocations

programs/rewards/Cargo.toml

@@ -27,3 +27,4 @@ path = "tests/rewards/tests.rs"
 
 [features]
 no-entrypoint = []
+testing = []

programs/rewards/src/entrypoint.rs

@@ -1,17 +1,25 @@
 //! Program entrypoint
 use crate::{error::MplxRewardsError, instructions::process_instruction};
+use solana_program::instruction::get_stack_height;
 use solana_program::{
     account_info::AccountInfo, entrypoint, entrypoint::ProgramResult,
     program_error::PrintProgramError, pubkey::Pubkey,
 };
 
 entrypoint!(program_entrypoint);
+
+pub const TRANSACTION_LEVEL_STACK_HEIGHT: usize = 1;
+
 fn program_entrypoint<'a>(
     program_id: &Pubkey,
     accounts: &'a [AccountInfo<'a>],
     instruction_data: &[u8],
 ) -> ProgramResult {
     if let Err(error) = process_instruction(program_id, accounts, instruction_data) {
+        #[cfg(not(feature = "testing"))]
+        if get_stack_height() == TRANSACTION_LEVEL_STACK_HEIGHT {
+            return Err(MplxRewardsError::ForbiddenInvocation.into());
+        }
         // Catch the error so we can print it
         error.print::<MplxRewardsError>();
         return Err(error);

programs/rewards/src/error.rs

@@ -84,6 +84,10 @@ pub enum MplxRewardsError {
     /// 19
     #[error("Account addres derivation has failed")]
     AccountDerivationAddresFailed,
+
+    /// 20
+    #[error("This contract is supposed to be called only from the staking contract")]
+    ForbiddenInvocation,
 }
 
 impl PrintProgramError for MplxRewardsError {