storage implementation

nym-api/migrations/20240209120000_free_pass_nonces.sql

@@ -3,8 +3,10 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-CREATE TABLE ISSUED_FREEPASS
+CREATE TABLE issued_freepass
 (
     id            INTEGER PRIMARY KEY CHECK (id = 0),
     current_nonce INTEGER NOT NULL
-);
+);
+
+INSERT INTO issued_freepass(id, current_nonce) VALUES (0,0);

nym-api/nym-api-requests/src/coconut/models.rs

@@ -149,7 +149,7 @@ pub struct FreePassRequest {
 
     // we need to include a nonce here to prevent replay attacks
     // (and not making the nym-api store the serial numbers of all issued credential)
-    pub used_nonce: u64,
+    pub used_nonce: u32,
 
     /// Signature on the nonce
     /// to prove the possession of the cosmos key/address
@@ -163,7 +163,7 @@ impl FreePassRequest {
         self.cosmos_pubkey.into()
     }
 
-    pub fn nonce_plaintext(&self) -> [u8; 8] {
+    pub fn nonce_plaintext(&self) -> [u8; 4] {
         self.used_nonce.to_be_bytes()
     }
 

nym-api/src/coconut/error.rs

@@ -45,7 +45,7 @@ pub enum CoconutError {
     FreePassSignatureVerificationFailure,
 
     #[error("the provided signing nonce is invalid. the current value is: {current}. got {received} instead")]
-    InvalidNonce { current: u64, received: u64 },
+    InvalidNonce { current: u32, received: u32 },
 
     #[error("only secp256k1 keys are supported for free pass issuance")]
     UnsupportedNonSecp256k1Key,

nym-api/src/coconut/storage/manager.rs

@@ -4,6 +4,7 @@
 use crate::coconut::storage::models::{EpochCredentials, IssuedCredential};
 use crate::support::storage::manager::StorageManager;
 use nym_coconut_dkg_common::types::EpochId;
+use thiserror::Error;
 
 #[async_trait]
 pub trait CoconutStorageManagerExt {
@@ -120,6 +121,17 @@ pub trait CoconutStorageManagerExt {
         start_after: i64,
         limit: u32,
     ) -> Result<Vec<IssuedCredential>, sqlx::Error>;
+
+    /// Attempts to retrieve the current value of the freepass nonce.
+    async fn get_current_freepass_nonce(&self) -> Result<u32, sqlx::Error>;
+
+    /// Attempt to update the currently stored nonce to the provided value whilst ensuring
+    /// it's strictly equal the current value plus 1
+    ///
+    /// # Arguments
+    ///
+    /// * `new`: the new value of the free pass nonce
+    async fn update_and_validate_freepass_nonce(&self, new: u32) -> Result<(), sqlx::Error>;
 }
 
 #[async_trait]
@@ -378,4 +390,49 @@ impl CoconutStorageManagerExt for StorageManager {
             .fetch_all(&self.connection_pool)
             .await
     }
+
+    /// Attempts to retrieve the current value of the freepass nonce.
+    async fn get_current_freepass_nonce(&self) -> Result<u32, sqlx::Error> {
+        sqlx::query!("SELECT current_nonce as 'current_nonce: u32' FROM issued_freepass")
+            .fetch_one(&self.connection_pool)
+            .await
+            .map(|row| row.current_nonce)
+    }
+
+    /// Attempt to update the currently stored nonce to the provided value whilst ensuring
+    /// it's strictly equal the current value plus 1
+    ///
+    /// # Arguments
+    ///
+    /// * `new`: the new value of the free pass nonce
+    async fn update_and_validate_freepass_nonce(&self, new: u32) -> Result<(), sqlx::Error> {
+        let mut tx = self.connection_pool.begin().await?;
+
+        let currently_stored =
+            sqlx::query!("SELECT current_nonce as 'current_nonce: u32' FROM issued_freepass")
+                .fetch_one(&mut tx)
+                .await?
+                .current_nonce;
+
+        if currently_stored + 1 != new {
+            // this is not the best error but I really don't want to be creating a new enum
+            return Err(sqlx::Error::Decode(Box::new(UnexpectedNonce {
+                current: currently_stored,
+                got: new,
+            })));
+        }
+
+        sqlx::query!("UPDATE issued_freepass SET current_nonce = ?", new)
+            .execute(&mut tx)
+            .await?;
+
+        tx.commit().await
+    }
+}
+
+#[derive(Debug, Error)]
+#[error("tried to store an invalid nonce. the received value is {got} while current is {current}. expected {current} + 1")]
+pub struct UnexpectedNonce {
+    current: u32,
+    got: u32,
 }

nym-api/src/coconut/storage/mod.rs

@@ -64,9 +64,9 @@ pub trait CoconutStorageExt {
         pagination: Pagination<i64>,
     ) -> Result<Vec<IssuedCredential>, NymApiStorageError>;
 
-    async fn get_current_freepass_nonce(&self) -> Result<u64, NymApiStorageError>;
+    async fn get_current_freepass_nonce(&self) -> Result<u32, NymApiStorageError>;
 
-    async fn update_and_validate_freepass_nonce(&self, new: u64) -> Result<(), NymApiStorageError>;
+    async fn update_and_validate_freepass_nonce(&self, new: u32) -> Result<(), NymApiStorageError>;
 }
 
 #[async_trait]
@@ -168,11 +168,11 @@ impl CoconutStorageExt for NymApiStorage {
             .await?)
     }
 
-    async fn get_current_freepass_nonce(&self) -> Result<u64, NymApiStorageError> {
+    async fn get_current_freepass_nonce(&self) -> Result<u32, NymApiStorageError> {
         todo!()
     }
 
-    async fn update_and_validate_freepass_nonce(&self, new: u64) -> Result<(), NymApiStorageError> {
+    async fn update_and_validate_freepass_nonce(&self, new: u32) -> Result<(), NymApiStorageError> {
         todo!()
     }
 }