How can I write to a file in wwwroot with Asp.Net core 2.0 Webapi

Question

I need a very simple API to allow for the Posting of certain keys. This keys should be written on a file, but I am having trouble after deploying the app, as I can read the file on a GET Request but the posting does not work.

The message it gives me is

"detail": "Access to the path '....\Keys\Keys.json' is denied.",

Code I am using to write to file:

        var path = "wwwroot/Keys/Keys.json";

        var result = new List <FireBaseKeysModel> ( );

        if (System.IO.File.Exists (path)) {
            var initialJson = System.IO.File.ReadAllText (path);
            var convertedJson =
                JsonConvert.DeserializeObject <List <FireBaseKeysModel>> (initialJson);
            try {
                result.AddRange (convertedJson);
            }
            catch  {
                //
            }

        }

        result.Add(new FireBaseKeysModel() {
            AccountId = accountId,
            AditionalInfo = addicionalInfo,
            DeviceInfo = deviceInfo,
            RegistrationKey = registrationKey,
            ClientId = clientId
        });

        var json = JsonConvert.SerializeObject (result.ToArray ( ));

        System.IO.File.WriteAllText (path, json);

Anyway I can fix this without needint to change permissions on the server itself?

Answer 1

I have similar task that I need to take logged-in users' upload files and store them on the server. I chose to store them under the folder structure wwwroot/uploads/{ environment }/{ username }/{ YYYY }/{ MM }/{ DD }/.

I am not giving you the exact answer to your problem but these are the steps you might want to try.

1. Enable static file usage

   public void Configure(IApplicationBuilder app, IHostingEnvironment env)
   {
       ...
   
       // With the usage of static file extensions, you shouldn't need to
       // set permissions to folders, if you decide to go with wwwroot.
       app.UseStaticFiles();
   
       ...
   }
   

2. Storage service

   public interface IStorageService
   {
       Task<string> UploadAsync(string path, IFormFile content, string 
           nameWithoutExtension = null);
   }
   
   public class LocalFileStorageService : IStorageService
   {
       private readonly IHostingEnvironment _env;
   
       public LocalFileStorageService(IHostingEnvironment env)
       {
           _env = env;
       }
   
       public async Task<string> UploadAsync(string path, IFormFile content, 
           string nameWithoutExtension = null)
       {
           if (content != null && content.Length > 0)
           {
               string extension = Path.GetExtension(content.FileName);
   
               // Never trust user's provided file name
               string fileName = $"{ nameWithoutExtension ?? Guid.NewGuid().ToString() }{ extension }";
   
               // Combine the path with web root and my folder of choice, 
               // "uploads" 
               path = Path.Combine(_env.WebRootPath, "uploads", path).ToLower();
   
               // If the path doesn't exist, create it.
               // In your case, you might not need it if you're going 
               // to make sure your `keys.json` file is always there.
               if (!Directory.Exists(path))
               {
                   Directory.CreateDirectory(path);
               }
   
               // Combine the path with the file name
               string fullFileLocation = Path.Combine(path, fileName).ToLower();
   
               // If your case, you might just need to open your 
               // `keys.json` and append text on it.
               // Note that there is FileMode.Append too you might want to
               // take a look.
               using (var fileStream = new FileStream(fullFileLocation, FileMode.Create))
               {
                  await Content.CopyToAsync(fileStream);
               }
   
               // I only want to get its relative path
               return fullFileLocation.Replace(_env.WebRootPath, 
                   String.Empty, StringComparison.OrdinalIgnoreCase);
           }
   
           return String.Empty;
       }
   }