From ddf3638e229d2fab80ab9efa4814d1f0521d2ba4 Mon Sep 17 00:00:00 2001
From: Dominik | Supercolony <43150707+coreggon11@users.noreply.github.com>
Date: Tue, 3 Oct 2023 12:50:17 +0200
Subject: [PATCH] revert approve removal

---
 contracts/src/token/psp22/psp22.rs  |  6 ++++++
 contracts/src/traits/psp22/psp22.rs | 15 +++++++++++++++
 lang/codegen/src/implementations.rs | 10 ++++++++++
 3 files changed, 31 insertions(+)

diff --git a/contracts/src/token/psp22/psp22.rs b/contracts/src/token/psp22/psp22.rs
index 08316858c..61e8b48af 100644
--- a/contracts/src/token/psp22/psp22.rs
+++ b/contracts/src/token/psp22/psp22.rs
@@ -77,6 +77,12 @@ pub trait PSP22Impl: Storage<Data> + Internal {
         Ok(())
     }
 
+    fn approve(&mut self, spender: AccountId, value: Balance) -> Result<(), PSP22Error> {
+        let owner = Self::env().caller();
+        self._approve_from_to(owner, spender, value)?;
+        Ok(())
+    }
+
     fn increase_allowance(&mut self, spender: AccountId, delta_value: Balance) -> Result<(), PSP22Error> {
         let owner = Self::env().caller();
         self._approve_from_to(owner, spender, self._allowance(&owner, &spender) + delta_value)
diff --git a/contracts/src/traits/psp22/psp22.rs b/contracts/src/traits/psp22/psp22.rs
index 9e4275d3a..5e375cb70 100644
--- a/contracts/src/traits/psp22/psp22.rs
+++ b/contracts/src/traits/psp22/psp22.rs
@@ -78,6 +78,21 @@ pub trait PSP22 {
         data: Vec<u8>,
     ) -> Result<(), PSP22Error>;
 
+    /// Allows `spender` to withdraw from the caller's account multiple times, up to
+    /// the `value` amount.
+    ///
+    /// If this function is called again it overwrites the current allowance with `value`.
+    ///
+    /// An `Approval` event is emitted.
+    ///
+    /// # Important
+    ///
+    /// This function is vulnerable to the double spending attack. 
+    /// Based on the OpenZeppelin security review of OpenBrush, we recommend using the
+    /// `increase_allowance` and `decrease_allowance` functions.
+    #[ink(message)]
+    fn approve(&mut self, spender: AccountId, value: Balance) -> Result<(), PSP22Error>;
+
     /// Atomically increases the allowance granted to `spender` by the caller.
     ///
     /// An `Approval` event is emitted.
diff --git a/lang/codegen/src/implementations.rs b/lang/codegen/src/implementations.rs
index 193c66754..4c0b45659 100644
--- a/lang/codegen/src/implementations.rs
+++ b/lang/codegen/src/implementations.rs
@@ -170,6 +170,11 @@ pub(crate) fn impl_psp22(impl_args: &mut ImplArgs, capped: bool) {
                 PSP22Impl::transfer_from(self, from, to, value, data)
             }
 
+            #[ink(message)]
+            fn approve(&mut self, spender: AccountId, value: Balance) -> Result<(), PSP22Error> {
+                PSP22Impl::approve(self, spender, value)
+            }
+
             #[ink(message)]
             fn increase_allowance(&mut self, spender: AccountId, delta_value: Balance) -> Result<(), PSP22Error> {
                 PSP22Impl::increase_allowance(self, spender, delta_value)
@@ -891,6 +896,11 @@ pub(crate) fn impl_psp22_pallet(impl_args: &mut ImplArgs) {
                 PSP22PalletImpl::transfer_from(self, from, to, value, data)
             }
 
+            #[ink(message)]
+            fn approve(&mut self, spender: AccountId, value: Balance) -> Result<(), PSP22Error> {
+                PSP22PalletImpl::approve(self, spender, value)
+            }
+
             #[ink(message)]
             fn increase_allowance(&mut self, spender: AccountId, delta_value: Balance) -> Result<(), PSP22Error> {
                 PSP22PalletImpl::increase_allowance(self, spender, delta_value)