Ignore invalid iptc tag values #1942

src/ImageSharp/Metadata/Profiles/IPTC/IptcProfile.cs

@@ -16,6 +16,10 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
     {
         private Collection<IptcValue> values;
 
+        private const byte IptcTagMarkerByte = 0x1c;
+
+        private const uint MaxStandardDataTagSize = 0x7FFF;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="IptcProfile"/> class.
         /// </summary>
@@ -78,7 +82,7 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
         }
 
         /// <inheritdoc/>
-        public IptcProfile DeepClone() => new IptcProfile(this);
+        public IptcProfile DeepClone() => new(this);
 
         /// <summary>
         /// Returns all values with the specified tag.
@@ -207,7 +211,7 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
                 throw new ArgumentException("iptc tag is not a time or date type");
             }
 
-            var formattedDate = tag.IsDate()
+            string formattedDate = tag.IsDate()
                 ? dateTimeOffset.ToString("yyyyMMdd", System.Globalization.CultureInfo.InvariantCulture)
                 : dateTimeOffset.ToString("HHmmsszzzz", System.Globalization.CultureInfo.InvariantCulture)
                     .Replace(":", string.Empty);
@@ -231,7 +235,7 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
         /// </summary>
         public void UpdateData()
         {
-            var length = 0;
+            int length = 0;
             foreach (IptcValue value in this.Values)
             {
                 length += value.Length + 5;
@@ -242,7 +246,7 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
             int i = 0;
             foreach (IptcValue value in this.Values)
             {
-                this.Data[i++] = 28;
+                this.Data[i++] = IptcTagMarkerByte;
                 this.Data[i++] = 2;
                 this.Data[i++] = (byte)value.Tag;
                 this.Data[i++] = (byte)(value.Length >> 8);
@@ -264,34 +268,29 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
 
             this.values = new Collection<IptcValue>();
 
-            if (this.Data == null || this.Data[0] != 0x1c)
+            if (this.Data == null || this.Data[0] != IptcTagMarkerByte)
             {
                 return;
             }
 
-            int i = 0;
+            int offset = 0;
-            while (i + 4 < this.Data.Length)
+            while (offset + 4 < this.Data.Length)
-            {
-                if (this.Data[i++] != 28)
             {
-                    continue;
+                bool isValidTagMarker = this.Data[offset++] == IptcTagMarkerByte;
-                }
+                byte recordType = this.Data[offset++];
-
+                var tag = (IptcTag)this.Data[offset++];
-                i++;
-
-                var tag = (IptcTag)this.Data[i++];
 
-                int count = BinaryPrimitives.ReadInt16BigEndian(this.Data.AsSpan(i, 2));
+                uint byteCount = BinaryPrimitives.ReadUInt16BigEndian(this.Data.AsSpan(offset, 2));
-                i += 2;
+                offset += 2;
 
-                var iptcData = new byte[count];
+                if (isValidTagMarker && byteCount > 0 && (offset + byteCount <= this.Data.Length))
-                if ((count > 0) && (i + count <= this.Data.Length))
                 {
-                    Buffer.BlockCopy(this.Data, i, iptcData, 0, count);
+                    var iptcData = new byte[byteCount];
+                    Buffer.BlockCopy(this.Data, offset, iptcData, 0, (int)byteCount);
                     this.values.Add(new IptcValue(tag, iptcData, false));
                 }
 
-                i += count;
+                offset += (int)byteCount;
             }
         }
     }

src/ImageSharp/Metadata/Profiles/IPTC/IptcTagExtensions.cs

@@ -13,9 +13,7 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
         /// </summary>
         /// <param name="tag">The tag to check the max length for.</param>
         /// <returns>The maximum length.</returns>
-        public static int MaxLength(this IptcTag tag)
+        public static int MaxLength(this IptcTag tag) => tag switch
-        {
-            return tag switch
         {
             IptcTag.RecordVersion => 2,
             IptcTag.ObjectType => 67,
@@ -66,7 +64,6 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
             IptcTag.ImageOrientation => 1,
             _ => 256
         };
-        }
 
         /// <summary>
         /// Determines if the given tag can be repeated according to the specification.

src/ImageSharp/Metadata/Profiles/IPTC/IptcValue.cs

@@ -101,7 +101,7 @@ namespace SixLabors.ImageSharp.Metadata.Profiles.Iptc
                     byte[] valueBytes;
                     if (this.Strict && value.Length > maxLength)
                     {
-                        var cappedValue = value.Substring(0, maxLength);
+                        string cappedValue = value.Substring(0, maxLength);
                         valueBytes = this.encoding.GetBytes(cappedValue);
 
                         // It is still possible that the bytes of the string exceed the limit.