Two bugs of iCal parsing was fixed (#424)

Author: Naglfario

nanoFramework.Json.Test/DateTimeExtensionsTests.cs

@@ -0,0 +1,59 @@
+//
+// Copyright (c) .NET Foundation and Contributors
+// See LICENSE file in the project root for full license information.
+//
+
+using nanoFramework.TestFramework;
+using System;
+
+namespace nanoFramework.Json.Test
+{
+    [TestClass]
+    public class DateTimeExtensionsTests
+    {
+        [TestMethod]
+        [DataRow("19990101T000000")]
+        [DataRow("20001120T221530")]
+        [DataRow("20250706T005433")]
+        [DataRow("16010101T000000")]
+        [DataRow("30001231T235958")]
+        public void FromiCalendar_LocalTime_ShouldNotBeMaxValue(string iCal)
+        {
+            var act = DateTimeExtensions.FromiCalendar(iCal);
+
+            Assert.AreNotEqual(DateTime.MaxValue, act);
+        }
+
+        [TestMethod]
+        [DataRow("19990101T000000Z")]
+        [DataRow("20001120T221530Z")]
+        [DataRow("20250706T005433Z")]
+        [DataRow("16010101T000000Z")]
+        [DataRow("30001231T235958Z")]
+        public void FromiCalendar_UtcTime_ShouldNotBeMaxValue(string iCal)
+        {
+            var act = DateTimeExtensions.FromiCalendar(iCal);
+
+            Assert.AreNotEqual(DateTime.MaxValue, act);
+        }
+
+        [TestMethod]
+        [DataRow("12345678901234567890")]
+        [DataRow("3333333333333333")]
+        [DataRow("444444444444444")]
+        [DataRow("12345678T901234")]
+        [DataRow("000000000000000")]
+        [DataRow("test")]
+        [DataRow("test19990101T000000Z")]
+        [DataRow("test0101T000000Z")]
+        [DataRow("test19990101T000000")]
+        [DataRow("test0101T000000")]
+        [DataRow("_!123@1903$#*((")]
+        public void FromiCalendar_NotATime_ShuldReturnMaxValue(string iCal)
+        {
+            var act = DateTimeExtensions.FromiCalendar(iCal);
+
+            Assert.AreEqual(DateTime.MaxValue, act);
+        }
+    }
+}

nanoFramework.Json.Test/nanoFramework.Json.Test.nfproj

@@ -49,6 +49,7 @@
     <Compile Include="Converters\FloatConverterTests.cs" />
     <Compile Include="Converters\DoubleConverterTests.cs" />
     <Compile Include="Configuration\JsonCustomTypeTests.cs" />
+    <Compile Include="DateTimeExtensionsTests.cs" />
     <Compile Include="JsonDeserializationArraysTests.cs" />
     <Compile Include="JsonSettingsTests.cs" />
     <Compile Include="JsonThreadSafeTests.cs" />

nanoFramework.Json/TimeExtensions.cs

@@ -55,6 +55,11 @@ public static DateTime FromiCalendar(string iCalendar)
                 time = result;  // localtime
             }
 
+            if (time.Length < 15)
+            {
+                return DateTime.MaxValue;
+            }
+
             // We now have the time string to parse, and we'll adjust
             // to UTC or timezone after parsing
             string year = time.Substring(0, 4);
@@ -65,43 +70,56 @@ public static DateTime FromiCalendar(string iCalendar)
             string second = time.Substring(13, 2);
 
             // Check if any of the date time parts is non-numeric
-            if (!IsNumeric(year))
+            if (!int.TryParse(year, out int intYear) ||
+                intYear < DateTime.MinValue.Year ||
+                intYear > DateTime.MaxValue.Year)
             {
                 return DateTime.MaxValue;
             }
-            else if (!IsNumeric(month))
+            if (!int.TryParse(month, out int intMonth) ||
+                intMonth < DateTime.MinValue.Month ||
+                intMonth > DateTime.MaxValue.Month)
             {
                 return DateTime.MaxValue;
             }
-            else if (!IsNumeric(day))
+            if (!int.TryParse(day, out int intDay) ||
+                intDay < DateTime.MinValue.Day ||
+                intDay > DateTime.MaxValue.Day ||
+                intDay > DateTime.DaysInMonth(intYear, intMonth))
             {
                 return DateTime.MaxValue;
             }
-            else if (!IsNumeric(hour))
+            if (!int.TryParse(hour, out int intHour) ||
+                intHour < DateTime.MinValue.Hour ||
+                intHour > DateTime.MaxValue.Hour)
             {
                 return DateTime.MaxValue;
             }
-            else if (!IsNumeric(minute))
+            if (!int.TryParse(minute, out int intMinute) ||
+                intMinute < DateTime.MinValue.Minute ||
+                intMinute > DateTime.MaxValue.Minute)
             {
                 return DateTime.MaxValue;
             }
-            else if (!IsNumeric(second))
+            if (!int.TryParse(second, out int intSecond) ||
+                intSecond < DateTime.MinValue.Second ||
+                intSecond > DateTime.MaxValue.Second)
             {
                 return DateTime.MaxValue;
             }
 
             DateTime dt = new(
-                Convert.ToInt32(year),
-                Convert.ToInt32(month),
-                Convert.ToInt32(day),
-                Convert.ToInt32(hour),
-                Convert.ToInt32(minute),
-                Convert.ToInt32(second));
+                intYear,
+                intMonth,
+                intDay,
+                intHour,
+                intMinute,
+                intSecond);
 
             if (utc)
             {
                 // Convert the Kind to DateTimeKind.Utc
-                dt = new DateTime(0, DateTimeKind.Utc).AddTicks(dt.Ticks);
+                dt = new DateTime(dt.Ticks, DateTimeKind.Utc);
             }
             else if (tzid)
             {