token-2022: Add support for Non-Transferable Tokens (NTTs) - NonTrans…

…ferableMint extension (solana-labs#3178)

Co-authored-by: Juan Oxoby <me@jmoxo.by>

token/program-2022/src/error.rs

@@ -135,9 +135,16 @@ pub enum TokenError {
     /// mint and try again
     #[error("An account can only be closed if its withheld fee balance is zero, harvest fees to the mint and try again")]
     AccountHasWithheldTransferFees,
+
     /// No memo in previous instruction; required for recipient to receive a transfer
     #[error("No memo in previous instruction; required for recipient to receive a transfer")]
     NoMemo,
+    /// Transfer is disabled for this mint
+    #[error("Transfer is disabled for this mint")]
+    NonTransferable,
+    /// Non-transferable tokens can't be minted to an account without immutable ownership
+    #[error("Non-transferable tokens can't be minted to an account without immutable ownership")]
+    NonTransferableNeedsImmutableOwnership,
 }
 impl From<TokenError> for ProgramError {
     fn from(e: TokenError) -> Self {

token/program-2022/src/extension/mod.rs

@@ -9,6 +9,7 @@ use {
             immutable_owner::ImmutableOwner,
             memo_transfer::MemoTransfer,
             mint_close_authority::MintCloseAuthority,
+            non_transferable::NonTransferable,
             transfer_fee::{TransferFeeAmount, TransferFeeConfig},
         },
         pod::*,
@@ -36,6 +37,8 @@ pub mod immutable_owner;
 pub mod memo_transfer;
 /// Mint Close Authority extension
 pub mod mint_close_authority;
+/// Non Transferable extension
+pub mod non_transferable;
 /// Utility to reallocate token accounts
 pub mod reallocate;
 /// Transfer Fee extension
@@ -599,6 +602,8 @@ pub enum ExtensionType {
     ImmutableOwner,
     /// Require inbound transfers to have memo
     MemoTransfer,
+    /// Indicates that the tokens from this mint can't be transfered
+    NonTransferable,
     /// Padding extension used to make an account exactly Multisig::LEN, used for testing
     #[cfg(test)]
     AccountPaddingTest = u16::MAX - 1,
@@ -637,6 +642,7 @@ impl ExtensionType {
             }
             ExtensionType::DefaultAccountState => pod_get_packed_len::<DefaultAccountState>(),
             ExtensionType::MemoTransfer => pod_get_packed_len::<MemoTransfer>(),
+            ExtensionType::NonTransferable => pod_get_packed_len::<NonTransferable>(),
             #[cfg(test)]
             ExtensionType::AccountPaddingTest => pod_get_packed_len::<AccountPaddingTest>(),
             #[cfg(test)]
@@ -691,7 +697,8 @@ impl ExtensionType {
             ExtensionType::TransferFeeConfig
             | ExtensionType::MintCloseAuthority
             | ExtensionType::ConfidentialTransferMint
-            | ExtensionType::DefaultAccountState => AccountType::Mint,
+            | ExtensionType::DefaultAccountState
+            | ExtensionType::NonTransferable => AccountType::Mint,
             ExtensionType::ImmutableOwner
             | ExtensionType::TransferFeeAmount
             | ExtensionType::ConfidentialTransferAccount

token/program-2022/src/extension/non_transferable.rs

@@ -0,0 +1,13 @@
+use {
+    crate::extension::{Extension, ExtensionType},
+    bytemuck::{Pod, Zeroable},
+};
+
+/// Indicates that the tokens from this mint can't be transfered
+#[derive(Clone, Copy, Debug, Default, PartialEq, Pod, Zeroable)]
+#[repr(transparent)]
+pub struct NonTransferable;
+
+impl Extension for NonTransferable {
+    const TYPE: ExtensionType = ExtensionType::NonTransferable;
+}

token/program-2022/src/instruction.rs

@@ -571,6 +571,19 @@ pub enum TokenInstruction<'a> {
     ///   2. `[]` System program for mint account funding
     ///
     CreateNativeMint,
+    /// Initialize the non transferable extension for the given mint account
+    ///
+    /// Fails if the account has already been initialized, so must be called before
+    /// `InitializeMint`.
+    ///
+    /// Accounts expected by this instruction:
+    ///
+    ///   0. `[writable]`  The mint account to initialize.
+    ///
+    /// Data expected by this instruction:
+    ///   None
+    ///
+    InitializeNonTransferableMint,
 }
 impl<'a> TokenInstruction<'a> {
     /// Unpacks a byte buffer into a [TokenInstruction](enum.TokenInstruction.html).
@@ -699,6 +712,7 @@ impl<'a> TokenInstruction<'a> {
             }
             30 => Self::MemoTransferExtension,
             31 => Self::CreateNativeMint,
+            32 => Self::InitializeNonTransferableMint,
             _ => return Err(TokenError::InvalidInstruction.into()),
         })
     }
@@ -845,6 +859,9 @@ impl<'a> TokenInstruction<'a> {
             &Self::CreateNativeMint => {
                 buf.push(31);
             }
+            &Self::InitializeNonTransferableMint => {
+                buf.push(32);
+            }
         };
         buf
     }
@@ -1684,6 +1701,19 @@ pub fn create_native_mint(
     })
 }
 
+/// Creates an `InitializeNonTransferableMint` instruction
+pub fn initialize_non_transferable_mint(
+    token_program_id: &Pubkey,
+    mint_pubkey: &Pubkey,
+) -> Result<Instruction, ProgramError> {
+    check_program_account(token_program_id)?;
+    Ok(Instruction {
+        program_id: *token_program_id,
+        accounts: vec![AccountMeta::new(*mint_pubkey, false)],
+        data: TokenInstruction::InitializeNonTransferableMint.pack(),
+    })
+}
+
 /// Utility function that checks index is between MIN_SIGNERS and MAX_SIGNERS
 pub fn is_valid_signer_index(index: usize) -> bool {
     (MIN_SIGNERS..=MAX_SIGNERS).contains(&index)

token/program-2022/src/processor.rs

@@ -10,6 +10,7 @@ use {
             immutable_owner::ImmutableOwner,
             memo_transfer::{self, check_previous_sibling_instruction_is_memo, memo_required},
             mint_close_authority::MintCloseAuthority,
+            non_transferable::NonTransferable,
             reallocate,
             transfer_fee::{self, TransferFeeAmount, TransferFeeConfig},
             ExtensionType, StateWithExtensions, StateWithExtensionsMut,
@@ -290,6 +291,11 @@ impl Processor {
 
             let mint_data = mint_info.try_borrow_data()?;
             let mint = StateWithExtensions::<Mint>::unpack(&mint_data)?;
+
+            if mint.get_extension::<NonTransferable>().is_ok() {
+                return Err(TokenError::NonTransferable.into());
+            }
+
             if expected_decimals != mint.base.decimals {
                 return Err(TokenError::MintDecimalsMismatch.into());
             }
@@ -694,6 +700,17 @@ impl Processor {
 
         let mut mint_data = mint_info.data.borrow_mut();
         let mut mint = StateWithExtensionsMut::<Mint>::unpack(&mut mint_data)?;
+
+        // If the mint if non-transferable, only allow minting to accounts
+        // with immutable ownership.
+        if mint.get_extension::<NonTransferable>().is_ok()
+            && destination_account
+                .get_extension::<ImmutableOwner>()
+                .is_err()
+        {
+            return Err(TokenError::NonTransferableNeedsImmutableOwnership.into());
+        }
+
         if let Some(expected_decimals) = expected_decimals {
             if expected_decimals != mint.base.decimals {
                 return Err(TokenError::MintDecimalsMismatch.into());
@@ -1111,6 +1128,18 @@ impl Processor {
         )
     }
 
+    /// Processes an [InitializeNonTransferableMint](enum.TokenInstruction.html) instruction
+    pub fn process_initialize_non_transferable_mint(accounts: &[AccountInfo]) -> ProgramResult {
+        let account_info_iter = &mut accounts.iter();
+        let mint_account_info = next_account_info(account_info_iter)?;
+
+        let mut mint_data = mint_account_info.data.borrow_mut();
+        let mut mint = StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut mint_data)?;
+        mint.init_extension::<NonTransferable>()?;
+
+        Ok(())
+    }
+
     /// Processes an [Instruction](enum.Instruction.html).
     pub fn process(program_id: &Pubkey, accounts: &[AccountInfo], input: &[u8]) -> ProgramResult {
         let instruction = TokenInstruction::unpack(input)?;
@@ -1260,6 +1289,10 @@ impl Processor {
                 msg!("Instruction: CreateNativeMint");
                 Self::process_create_native_mint(accounts)
             }
+            TokenInstruction::InitializeNonTransferableMint => {
+                msg!("Instruction: InitializeNonTransferableMint");
+                Self::process_initialize_non_transferable_mint(accounts)
+            }
         }
     }
 
@@ -1414,6 +1447,12 @@ impl PrintProgramError for TokenError {
             TokenError::NoMemo => {
                 msg!("Error: No memo in previous instruction; required for recipient to receive a transfer");
             }
+            TokenError::NonTransferable => {
+                msg!("Transfer is disabled for this mint");
+            }
+            TokenError::NonTransferableNeedsImmutableOwnership => {
+                msg!("Non-transferable tokens can't be minted to an account without immutable ownership");
+            }
         }
     }
 }