feat: only provider can subscribe to a private subscription plan

Author: ironman0x7b2

x/subscription/keeper/msg_handler.go

@@ -255,17 +255,26 @@ func (k *Keeper) HandleMsgStartSubscription(ctx sdk.Context, msg *v3.MsgStartSub
 		return nil, types.NewErrorInvalidPlanStatus(plan.ID, plan.Status)
 	}
 
-	price, found := plan.Price(msg.Denom)
-	if !found {
-		return nil, types.NewErrorPriceNotFound(msg.Denom)
+	accAddr, err := sdk.AccAddressFromBech32(msg.From)
+	if err != nil {
+		return nil, err
 	}
 
-	price, err := price.UpdateQuoteValue(ctx, k.QuotePriceFunc)
+	provAddr, err := base.ProvAddressFromBech32(plan.ProvAddress)
 	if err != nil {
 		return nil, err
 	}
 
-	accAddr, err := sdk.AccAddressFromBech32(msg.From)
+	if plan.IsPrivate() && !accAddr.Equals(provAddr) {
+		return nil, types.NewErrorUnauthorized(msg.From)
+	}
+
+	price, found := plan.Price(msg.Denom)
+	if !found {
+		return nil, types.NewErrorPriceNotFound(msg.Denom)
+	}
+
+	price, err = price.UpdateQuoteValue(ctx, k.QuotePriceFunc)
 	if err != nil {
 		return nil, err
 	}
@@ -291,11 +300,6 @@ func (k *Keeper) HandleMsgStartSubscription(ctx sdk.Context, msg *v3.MsgStartSub
 		return nil, err
 	}
 
-	provAddr, err := base.ProvAddressFromBech32(plan.ProvAddress)
-	if err != nil {
-		return nil, err
-	}
-
 	payment := totalPayment.Sub(reward)
 	if err := k.SendCoin(ctx, accAddr, provAddr.Bytes(), payment); err != nil {
 		return nil, err