Add invalid pattern exception when there is a dot between ] and hostname.

Add equivalent component test.

Bug: 823706
Change-Id: I4f4b549bde567ea70e25afae86704b45820b9acb
Reviewed-on: https://chromium-review.googlesource.com/c/1475189Reviewed-by: Martin Šrámek <msramek@chromium.org>
Reviewed-by: Kamila Hasanbega <hkamila@google.com>
Reviewed-by: Balazs Engedy <engedy@chromium.org>
Commit-Queue: Pauline Anthonysamy <anthonysp@google.com>
Cr-Commit-Position: refs/heads/master@{#634763}

components/content_settings/core/common/content_settings_pattern_parser.cc

@@ -20,6 +20,10 @@ const char kPortWildcard[] = "*";
 const char kSchemeWildcard[] = "*";
 const char kUrlPathSeparator[] = "/";
 const char kUrlPortSeparator[] = ":";
+// A domain wildcard pattern involves exactly one separating dot,
+// inside the square brackets. This is a common misunderstanding of that
+// pattern that we want to check for. See: https://crbug.com/823706.
+const char kDomainWildcardWithSuperfluousDot[] = "[*.].";
 
 }  // namespace
 
@@ -130,6 +134,12 @@ void PatternParser::Parse(base::StringPiece pattern_spec,
         return;
       }
 
+      if (base::StartsWith(host_piece, kDomainWildcardWithSuperfluousDot,
+                           base::CompareCase::SENSITIVE)) {
+        builder->Invalid();
+        return;
+      }
+
       host_piece.remove_prefix(kDomainWildcardLength);
       builder->WithDomainWildcard();
       builder->WithHost(host_piece.as_string());

components/content_settings/core/common/content_settings_pattern_parser_unittest.cc

@@ -150,6 +150,16 @@ TEST(ContentSettingsPatternParserTest, ParsePatterns) {
       ::testing::Return(&builder));
   content_settings::PatternParser::Parse("www.youtube.com*", &builder);
   ::testing::Mock::VerifyAndClear(&builder);
+
+  // Test for kDomainWildcardWithSuperfluousDot
+  EXPECT_CALL(builder, WithSchemeWildcard())
+      .Times(1)
+      .WillOnce(::testing::Return(&builder));
+  EXPECT_CALL(builder, Invalid())
+      .Times(1)
+      .WillOnce(::testing::Return(&builder));
+  content_settings::PatternParser::Parse("[*.].youtube.com", &builder);
+  ::testing::Mock::VerifyAndClear(&builder);
 }
 
 TEST(ContentSettingsPatternParserTest, ParseFilePatterns) {