Add sanitation and make tests parametric.

Author: JimBobSquarePants

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -514,6 +514,11 @@ private void ProcessApplicationHeaderMarker(BufferedReadStream stream, int remai
             // TODO: thumbnail
             if (remaining > 0)
             {
+                if (stream.Position + remaining >= stream.Length)
+                {
+                    JpegThrowHelper.ThrowInvalidImageContentException("Bad App0 Marker length.");
+                }
+
                 stream.Skip(remaining);
             }
         }
@@ -533,6 +538,11 @@ private void ProcessApp1Marker(BufferedReadStream stream, int remaining)
                 return;
             }
 
+            if (stream.Position + remaining >= stream.Length)
+            {
+                JpegThrowHelper.ThrowInvalidImageContentException("Bad App1 Marker length.");
+            }
+
             var profile = new byte[remaining];
             stream.Read(profile, 0, remaining);
 
@@ -550,6 +560,7 @@ private void ProcessApp1Marker(BufferedReadStream stream, int remaining)
                     this.ExtendProfile(ref this.exifData, profile.AsSpan(Exif00).ToArray());
                 }
             }
+
         }
 
         /// <summary>

src/ImageSharp/IO/BufferedReadStream.cs

@@ -50,8 +50,8 @@ public BufferedReadStream(Configuration configuration, Stream stream)
             }
 
             this.BaseStream = stream;
-            this.Position = (int)stream.Position;
             this.Length = stream.Length;
+            this.Position = (int)stream.Position;
             this.BufferSize = configuration.StreamProcessingBufferSize;
             this.maxBufferIndex = this.BufferSize - 1;
             this.readBuffer = ArrayPool<byte>.Shared.Rent(this.BufferSize);
@@ -86,6 +86,9 @@ public override long Position
             [MethodImpl(MethodImplOptions.NoInlining)]
             set
             {
+                Guard.MustBeGreaterThanOrEqualTo(value, 0, nameof(this.Position));
+                Guard.MustBeLessThan(value, this.Length, nameof(this.Position));
+
                 // Only reset readBufferIndex if we are out of bounds of our working buffer
                 // otherwise we should simply move the value by the diff.
                 if (this.IsInReadBuffer(value, out long index))