How to check if file type is supported? about filetypechecker HOT 12 CLOSED

Just for a bit more context, I end up writing something like this as a work-around:

    /// <summary>
    /// Just for exposing FileTypeValidator.FileTypes
    /// </summary>
    private abstract class TypeValidator : FileTypeValidator
    {
        public static new IReadOnlyCollection<IFileType> FileTypes
            => FileTypeValidator.FileTypes;
    }

    private bool IsSignatureBitsValid(IFormFile file, string extension)
    {
        if (!TypeValidator.FileTypes.Any(t => t.Extension == extension))
        {
            return true; //or false
        }

        using var stream = file.OpenReadStream();
        if (!FileTypeValidator.IsTypeRecognizable(stream))
        {
            return false;
        }

        var fileType = FileTypeValidator.GetFileType(stream);
        return fileType.Extension == extension;
    }

from filetypechecker.

@RetainPhil You are doing basically the same thing that the IsTypeRecognizable method does with the only difference that the IsTypeRecognizable method is comparing the bytes while your code compares two strings. This library is supporting a large variety of types. If the type you are looking for is not supported you can implement it easily.

The expression TypeValidator.FileTypes.Any(t => t.Extension == extension) will return the same result as FileTypeValidator.IsTypeRecognizable(stream) every time.

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EDIT: Yeh I see what you're saying. Well I guess I was thinking that maybe someone might want to handle the cases where a file claims to be of a type which has a validator, but the validation fails, and a file which doesn't even have a validator to begin with. (and might or might not be valid).

In the end I suppose you'd have to verify that the extension is something that the system supports (and has a validator) before checking the signature bits, either way there's a hard-coded list of 'supported types' you'd have to manage, whether that's the types supported out of the box by the library already or not.

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quick question guys , does filesteam.IsImage , incluse Webp images ?

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At the moment no, but I am planning to include it in the next release. If you want your code to recognize it you can implement a custom type

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@AJMitev thanks, and great work btw 😉

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@AJMitev sorry to bother you again , can you say if this code is safe enought to test for webp ?

 public class WebPFileType : FileType
    {
        private static readonly string name = "WebPacl Custom Type 1.0";
        private static readonly string extension = "webp";
        private static readonly byte[] magicBytes = new byte[] { 0x52, 0x49 };

        public WebPFileType() : base(name, extension, magicBytes) { }
    }

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It's looking good :)

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@AJMitev sorry to bother you again , can you say if this code is safe enought to test for webp ?

 public class WebPFileType : FileType
    {
        private static readonly string name = "WebPacl Custom Type 1.0";
        private static readonly string extension = "webp";
        private static readonly byte[] magicBytes = new byte[] { 0x52, 0x49 };

        public WebPFileType() : base(name, extension, magicBytes) { }
    }

@AJMitev can you help me out please ? i created my custom type , and when a test it with a wepb img ( i double checked the header for magic bytes ) but the code 'fileStream.Is<WebPFileType>()' always return false , any ideas why?

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Try this:

  using (var fileStream = File.OpenRead("myFileLocation"))
  {
      var isRecognizableType = FileTypeValidator.IsTypeRecognizable(fileStream);
  }

If isRecognizableType is false then you are not registered your type correctly. And you should read this.

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@AJMitev i did registered in the startup class
and isRecognizableType return true

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Well, this is easy to debug mate, just retrieve the type and see what you will receive.

 var fileType = FileTypeValidator.GetFileType(fileStream);

Now when I saw the bytes you are defined in your type, I bet it will return AVI instead of WebP, this is because the beginning of both types are the same and for now FindMaxScore returns the first type that scores the highest. In that case AVI.

For now I can recommend you to set more specific byte definition. In near future I will improve the behavior.

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