Remove invalidation of whitespace in TryGetNextExtendedAttribute

src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarHeader.Read.cs

@@ -723,12 +723,6 @@ private static bool TryGetNextExtendedAttribute(
             }
             line = line.Slice(spacePos + 1).TrimStart((byte)' ');
 
-            // If there are any more spaces, it's malformed.
-            if (line.IndexOf((byte)' ') >= 0)
-            {
-                return false;
-            }
-
             // Find the equal separator.
             int equalPos = line.IndexOf((byte)'=');
             if (equalPos < 0)

src/libraries/System.Formats.Tar/tests/TarReader/TarReader.File.GlobalExtendedAttributes.Tests.cs

@@ -82,5 +82,27 @@ public void ExtractGlobalExtendedAttributesEntry_Throws()
                 Assert.Throws<InvalidOperationException>(() => entry.ExtractToFile(Path.Join(root.Path, "file"), overwrite: true));
             }
         }
+
+        [Theory]
+        [InlineData("key", "value")]
+        [InlineData("key     ", "   value    ")]
+        [InlineData("      key     ", "   value    ")]
+        [InlineData("many sla/s\\hes", "/////////////\\\\\\///////////")]
+        public void GlobalExtendedAttribute_Roundtrips(string key, string value)
+        {
+            var stream = new MemoryStream();
+            using (var writer = new TarWriter(stream, leaveOpen: true))
+            {
+                writer.WriteEntry(new PaxGlobalExtendedAttributesTarEntry(new Dictionary<string, string>() { { key, value } }));
+            }
+
+            stream.Position = 0;
+            using (var reader = new TarReader(stream))
+            {
+                PaxGlobalExtendedAttributesTarEntry entry = Assert.IsType<PaxGlobalExtendedAttributesTarEntry>(reader.GetNextEntry());
+                Assert.Equal(1, entry.GlobalExtendedAttributes.Count);
+                Assert.Equal(KeyValuePair.Create(key.TrimStart(), value), entry.GlobalExtendedAttributes.First());
+            }
+        }
     }
 }

src/libraries/System.Formats.Tar/tests/TarReader/TarReader.File.Tests.cs

@@ -333,6 +333,28 @@ public void PaxSizeLargerThanMaxAllowedByStream()
             Assert.Throws<ArgumentOutOfRangeException>(() => reader.GetNextEntry());
         }
 
+        [Theory]
+        [InlineData("key", "value")]
+        [InlineData("key     ", "   value    ")]
+        [InlineData("      key     ", "   value    ")]
+        [InlineData("many sla/s\\hes", "/////////////\\\\\\///////////")]
+        public void PaxExtendedAttribute_Roundtrips(string key, string value)
+        {
+            var stream = new MemoryStream();
+            using (var writer = new TarWriter(stream, leaveOpen: true))
+            {
+                writer.WriteEntry(new PaxTarEntry(TarEntryType.Directory, "entryName", new Dictionary<string, string>() { { key, value } }));
+            }
+
+            stream.Position = 0;
+            using (var reader = new TarReader(stream))
+            {
+                PaxTarEntry entry = Assert.IsType<PaxTarEntry>(reader.GetNextEntry());
+                Assert.Equal(5, entry.ExtendedAttributes.Count);
+                Assert.Contains(KeyValuePair.Create(key.TrimStart(), value), entry.ExtendedAttributes);
+            }
+        }
+
         private static void VerifyDataStreamOfTarUncompressedInternal(string testFolderName, string testCaseName, bool copyData)
         {
             using MemoryStream archiveStream = GetTarMemoryStream(CompressionMethod.Uncompressed, testFolderName, testCaseName);