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;
-            while (i + 4 < this.Data.Length)
+            int offset = 0;
+            while (offset + 4 < this.Data.Length)
             {
-                if (this.Data[i++] != 28)
-                {
-                    continue;
-                }
-
-                i++;
-
-                var tag = (IptcTag)this.Data[i++];
+                bool isValidTagMarker = this.Data[offset++] == IptcTagMarkerByte;
+                byte recordType = this.Data[offset++];
+                var tag = (IptcTag)this.Data[offset++];
 
-                int count = BinaryPrimitives.ReadInt16BigEndian(this.Data.AsSpan(i, 2));
-                i += 2;
+                uint byteCount = BinaryPrimitives.ReadUInt16BigEndian(this.Data.AsSpan(offset, 2));
+                offset += 2;
 
-                var iptcData = new byte[count];
-                if ((count > 0) && (i + count <= this.Data.Length))
+                if (isValidTagMarker && byteCount > 0 && (offset + byteCount <= 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

@@ -13,60 +13,57 @@ 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,
-                IptcTag.ObjectAttribute => 68,
-                IptcTag.Name => 64,
-                IptcTag.EditStatus => 64,
-                IptcTag.EditorialUpdate => 2,
-                IptcTag.Urgency => 1,
-                IptcTag.SubjectReference => 236,
-                IptcTag.Category => 3,
-                IptcTag.SupplementalCategories => 32,
-                IptcTag.FixtureIdentifier => 32,
-                IptcTag.Keywords => 64,
-                IptcTag.LocationCode => 3,
-                IptcTag.LocationName => 64,
-                IptcTag.ReleaseDate => 8,
-                IptcTag.ReleaseTime => 11,
-                IptcTag.ExpirationDate => 8,
-                IptcTag.ExpirationTime => 11,
-                IptcTag.SpecialInstructions => 256,
-                IptcTag.ActionAdvised => 2,
-                IptcTag.ReferenceService => 10,
-                IptcTag.ReferenceDate => 8,
-                IptcTag.ReferenceNumber => 8,
-                IptcTag.CreatedDate => 8,
-                IptcTag.CreatedTime => 11,
-                IptcTag.DigitalCreationDate => 8,
-                IptcTag.DigitalCreationTime => 11,
-                IptcTag.OriginatingProgram => 32,
-                IptcTag.ProgramVersion => 10,
-                IptcTag.ObjectCycle => 1,
-                IptcTag.Byline => 32,
-                IptcTag.BylineTitle => 32,
-                IptcTag.City => 32,
-                IptcTag.SubLocation => 32,
-                IptcTag.ProvinceState => 32,
-                IptcTag.CountryCode => 3,
-                IptcTag.Country => 64,
-                IptcTag.OriginalTransmissionReference => 32,
-                IptcTag.Headline => 256,
-                IptcTag.Credit => 32,
-                IptcTag.Source => 32,
-                IptcTag.CopyrightNotice => 128,
-                IptcTag.Contact => 128,
-                IptcTag.Caption => 2000,
-                IptcTag.CaptionWriter => 32,
-                IptcTag.ImageType => 2,
-                IptcTag.ImageOrientation => 1,
-                _ => 256
-            };
-        }
+            IptcTag.RecordVersion => 2,
+            IptcTag.ObjectType => 67,
+            IptcTag.ObjectAttribute => 68,
+            IptcTag.Name => 64,
+            IptcTag.EditStatus => 64,
+            IptcTag.EditorialUpdate => 2,
+            IptcTag.Urgency => 1,
+            IptcTag.SubjectReference => 236,
+            IptcTag.Category => 3,
+            IptcTag.SupplementalCategories => 32,
+            IptcTag.FixtureIdentifier => 32,
+            IptcTag.Keywords => 64,
+            IptcTag.LocationCode => 3,
+            IptcTag.LocationName => 64,
+            IptcTag.ReleaseDate => 8,
+            IptcTag.ReleaseTime => 11,
+            IptcTag.ExpirationDate => 8,
+            IptcTag.ExpirationTime => 11,
+            IptcTag.SpecialInstructions => 256,
+            IptcTag.ActionAdvised => 2,
+            IptcTag.ReferenceService => 10,
+            IptcTag.ReferenceDate => 8,
+            IptcTag.ReferenceNumber => 8,
+            IptcTag.CreatedDate => 8,
+            IptcTag.CreatedTime => 11,
+            IptcTag.DigitalCreationDate => 8,
+            IptcTag.DigitalCreationTime => 11,
+            IptcTag.OriginatingProgram => 32,
+            IptcTag.ProgramVersion => 10,
+            IptcTag.ObjectCycle => 1,
+            IptcTag.Byline => 32,
+            IptcTag.BylineTitle => 32,
+            IptcTag.City => 32,
+            IptcTag.SubLocation => 32,
+            IptcTag.ProvinceState => 32,
+            IptcTag.CountryCode => 3,
+            IptcTag.Country => 64,
+            IptcTag.OriginalTransmissionReference => 32,
+            IptcTag.Headline => 256,
+            IptcTag.Credit => 32,
+            IptcTag.Source => 32,
+            IptcTag.CopyrightNotice => 128,
+            IptcTag.Contact => 128,
+            IptcTag.Caption => 2000,
+            IptcTag.CaptionWriter => 32,
+            IptcTag.ImageType => 2,
+            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.