74 lines
3.2 KiB
C#
74 lines
3.2 KiB
C#
using System.Text.RegularExpressions;
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using PluralKit.Core;
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using SixLabors.ImageSharp;
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namespace PluralKit.Bot;
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public static class AvatarUtils
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{
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public static async Task VerifyAvatarOrThrow(HttpClient client, string url, bool isFullSizeImage = false)
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{
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if (url.Length > Limits.MaxUriLength)
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throw Errors.UrlTooLong(url);
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// List of MIME types we consider acceptable
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var acceptableMimeTypes = new[]
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{
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"image/jpeg", "image/gif", "image/png"
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// TODO: add image/webp once ImageSharp supports this
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};
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if (!PluralKit.Core.MiscUtils.TryMatchUri(url, out var uri))
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throw Errors.InvalidUrl;
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if (uri.Host.Contains("toyhou.se"))
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throw new PKError("Due to server issues, PluralKit is unable to read images hosted on toyhou.se.");
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url = TryRewriteCdnUrl(url);
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var response = await client.GetAsync(url);
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if (!response.IsSuccessStatusCode) // Check status code
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throw Errors.AvatarServerError(response.StatusCode);
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if (response.Content.Headers.ContentLength == null) // Check presence of content length
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throw Errors.AvatarNotAnImage(null);
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try
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{
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if (!acceptableMimeTypes.Contains(response.Content.Headers.ContentType.MediaType)) // Check MIME type
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throw Errors.AvatarNotAnImage(response.Content.Headers.ContentType.MediaType);
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}
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catch (NullReferenceException)
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{
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throw new PKError("Could not verify avatar is an image. This can happen when the server sends a malformed response."
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+ "\nPlease join the support server for help: <https://discord.gg/PczBt78>");
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}
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if (isFullSizeImage)
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// no need to do size checking on banners
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return;
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if (response.Content.Headers.ContentLength > Limits.AvatarFileSizeLimit) // Check content length
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throw Errors.AvatarFileSizeLimit(response.Content.Headers.ContentLength.Value);
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// Parse the image header in a worker
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var stream = await response.Content.ReadAsStreamAsync();
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var image = await Task.Run(() => Image.Identify(stream));
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if (image == null) throw Errors.AvatarInvalid;
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if (image.Width > Limits.AvatarDimensionLimit ||
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image.Height > Limits.AvatarDimensionLimit) // Check image size
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throw Errors.AvatarDimensionsTooLarge(image.Width, image.Height);
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}
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// Rewrite cdn.discordapp.com URLs to media.discordapp.net for jpg/png files
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// This lets us add resizing parameters to "borrow" their media proxy server to downsize the image
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// which in turn makes it more likely to be underneath the size limit!
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private static readonly Regex DiscordCdnUrl =
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new(@"^https?://(?:cdn\.discordapp\.com|media\.discordapp\.net)/attachments/(\d{17,19})/(\d{17,19})/([^/\\&\?]+)\.(png|jpg|jpeg|webp)(\?.*)?$");
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private static readonly string DiscordMediaUrlReplacement =
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"https://media.discordapp.net/attachments/$1/$2/$3.$4?width=256&height=256";
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public static string? TryRewriteCdnUrl(string? url) =>
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url == null ? null : DiscordCdnUrl.Replace(url, DiscordMediaUrlReplacement);
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} |