chore(rln-relay): confirm that the provided credential is correct using onchain query (#1980)

tests/waku_rln_relay/test_rln_group_manager_onchain.nim

@@ -244,7 +244,7 @@ suite "Onchain group manager":
         require:
           registrations.len == 1
           registrations[0].idCommitment == credentials.idCommitment
-          registrations[0].index == 1
+          registrations[0].index == 0
         fut.complete()
       return callback
 
@@ -283,7 +283,7 @@ suite "Onchain group manager":
       proc callback(registrations: seq[Membership]): Future[void] {.async.} =
         if registrations.len == 1 and
             registrations[0].idCommitment == credentials[futureIndex].idCommitment and
-            registrations[0].index == MembershipIndex(futureIndex + 1):
+            registrations[0].index == MembershipIndex(futureIndex):
           futs[futureIndex].complete()
           futureIndex += 1
       return callback
@@ -373,7 +373,7 @@ suite "Onchain group manager":
     proc callback(registrations: seq[Membership]): Future[void] {.async.} =
       if registrations.len == 1 and
          registrations[0].idCommitment == credentials.idCommitment and
-         registrations[0].index == 1:
+         registrations[0].index == 0:
         manager.idCredentials = some(credentials)
         manager.membershipIndex = some(registrations[0].index)
         fut.complete()
@@ -443,7 +443,7 @@ suite "Onchain group manager":
     proc callback(registrations: seq[Membership]): Future[void] {.async.} =
       if registrations.len == 1 and
          registrations[0].idCommitment == credentials.idCommitment and
-         registrations[0].index == 1:
+         registrations[0].index == 0:
         manager.idCredentials = some(credentials)
         manager.membershipIndex = some(registrations[0].index)
         fut.complete()
@@ -527,7 +527,7 @@ suite "Onchain group manager":
       proc callback(registrations: seq[Membership]): Future[void] {.async.} =
         if registrations.len == 1 and
             registrations[0].idCommitment == credentials[futureIndex].idCommitment and
-            registrations[0].index == MembershipIndex(futureIndex + 1):
+            registrations[0].index == MembershipIndex(futureIndex):
           futs[futureIndex].complete()
           futureIndex += 1
       return callback

waku/waku_rln_relay/group_manager/on_chain/group_manager.nim

@@ -28,17 +28,26 @@ logScope:
   topics = "waku rln_relay onchain_group_manager"
 
 contract(WakuRlnRegistry):
+  # this describes the storage slot to use
   proc usingStorageIndex(): Uint16 {.pure.}
+  # this map contains the address of a given storage slot
   proc storages(index: Uint16): Address {.pure.}
+  # this serves as an entrypoint into the rln storage contract
   proc register(storageIndex: Uint16, idCommitment: Uint256)
+  # this creates a new storage on the rln registry
   proc newStorage()
 
 # membership contract interface
 contract(RlnStorage):
+  # this event is raised when a new member is registered
   proc MemberRegistered(idCommitment: Uint256, index: Uint256) {.event.}
+  # this constant contains the membership deposit of the contract
   proc MEMBERSHIP_DEPOSIT(): Uint256 {.pure.}
-  proc members(idCommitment: Uint256): Uint256 {.view.}
+  # this map denotes existence of a given user
+  proc memberExists(idCommitment: Uint256): Uint256 {.view.}
+  # this constant describes the next index of a new member
   proc idCommitmentIndex(): Uint256 {.view.}
+  # this constant describes the block number this contract was deployed on
   proc deployedBlockNumber(): Uint256 {.view.}
 
 type
@@ -448,6 +457,17 @@ method init*(g: OnchainGroupManager): Future[void] {.async.} =
     if keystoreCredRes.isErr():
       raise newException(ValueError, "could not parse the keystore: " & $keystoreCredRes.error)
     let keystoreCred = keystoreCredRes.get()
+    # now we check on the contract if the commitment actually has a membership
+    try:
+      let membershipExists = await rlnContract.memberExists(keystoreCred
+                                                            .identityCredential
+                                                            .idCommitment.toUInt256()).call()
+      if membershipExists == 0:
+        raise newException(CatchableError, "the provided commitment does not have a membership")
+    except CatchableError:
+      raise newException(CatchableError, "could not check if the commitment exists on the contract: " &
+                                         getCurrentExceptionMsg())
+
     g.idCredentials = some(keystoreCred.identityCredential)
 
   let metadataGetRes = g.rlnInstance.getMetadata()