Allow "*" as the leading character in structured header tokens.

This affects the parsing and serialization of tokens in structured
headers draft 15 and above. When operating in Draft 9 mode for backwards
compatibility, a character sequence beginning with an asterisk will be
parsed as a byte sequence instead.

Bug: 1048756
Change-Id: I5b1e2a57501a2e2dedb1183f495f71d75146c46b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2084711Reviewed-by: Asanka Herath <asanka@chromium.org>
Commit-Queue: Ian Clelland <iclelland@chromium.org>
Cr-Commit-Position: refs/heads/master@{#746380}

net/http/structured_headers.cc

@@ -305,7 +305,8 @@ class StructuredHeaderParser {
 
   // Parses a Token ([SH09] 4.2.10, [SH15] 4.2.6).
   base::Optional<Item> ReadToken() {
-    if (input_.empty() || !base::IsAsciiAlpha(input_.front())) {
+    if (input_.empty() ||
+        !(base::IsAsciiAlpha(input_.front()) || input_.front() == '*')) {
       LogParseError("ReadToken", "ALPHA");
       return base::nullopt;
     }
@@ -538,7 +539,8 @@ class StructuredHeaderSerializer {
     if (value.is_token()) {
       // Serializes a Token ([SH15] 4.1.7).
       if (!value.GetString().size() ||
-          !base::IsAsciiAlpha(value.GetString().front()))
+          !(base::IsAsciiAlpha(value.GetString().front()) ||
+            value.GetString().front() == '*'))
         return false;
       if (value.GetString().find_first_not_of(kTokenChars15) !=
           std::string::npos)

net/http/structured_headers_unittest.cc

@@ -61,6 +61,7 @@ const struct ItemTestCase {
     {"bad token - item", "abc$@%!", base::nullopt},
     {"leading whitespace", " foo", Token("foo"), "foo"},
     {"trailing whitespace", "foo ", Token("foo"), "foo"},
+    {"leading asterisk", "*foo", Token("*foo")},
     // Number
     {"basic integer", "42", Integer(42L)},
     {"zero integer", "0", Integer(0L)},
@@ -427,6 +428,7 @@ const ItemTestCase sh09_item_test_cases[] = {
      "*iQ==*"},
     {"non-ASCII binary", "*/+Ah*", Item("\xFF\xE0!", Item::kByteSequenceType)},
     {"base64url binary", "*_-Ah*", base::nullopt},
+    {"token with leading asterisk", "*foo", base::nullopt},
 };
 
 // For Structured Headers Draft 15
@@ -763,7 +765,6 @@ TEST(StructuredHeaderTest, UnserializableTokens) {
       {"begins with colon", ":token"},
       {"begins with percent", "%token"},
       {"begins with period", ".token"},
-      {"begins with asterisk", "*token"},
       {"begins with slash", "/token"},
   };
   for (const auto& bad_token : bad_tokens) {