src: Support backslash escapes in quoted-string when parsing Link header

src/http2.cc

@@ -706,6 +706,28 @@ InputIt skip_to_next_field(InputIt first, InputIt last) {
 }
 } // namespace
 
+namespace {
+// Skip to the right dquote ('"'), handling backslash escapes.
+// Returns |last| if input is not terminated with '"'.
+template <typename InputIt>
+InputIt skip_to_right_dquote(InputIt first, InputIt last) {
+  for (; first != last;) {
+    switch (*first) {
+    case '"':
+      return first;
+    case '\\':
+      ++first;
+      if (first == last) {
+        return first;
+      }
+      break;
+    }
+    ++first;
+  }
+  return first;
+}
+} // namespace
+
 namespace {
 std::pair<LinkHeader, const char *>
 parse_next_link_header_once(const char *first, const char *last) {
@@ -862,7 +884,7 @@ parse_next_link_header_once(const char *first, const char *last) {
     }
     if (*first == '"') {
       // quoted-string
-      first = std::find(first + 1, last, '"');
+      first = skip_to_right_dquote(first + 1, last);
       if (first == last) {
         return {{{0, 0}}, first};
       }

src/http2_test.cc

@@ -593,6 +593,13 @@ void test_http2_parse_link_header(void) {
     auto res = http2::parse_link_header(s, sizeof(s) - 1);
     CU_ASSERT(0 == res.size());
   }
+  {
+    // backslash escaped characters in quoted-string
+    const char s[] = R"(<url>; rel=preload; title="foo\"baz\"bar")";
+    auto res = http2::parse_link_header(s, sizeof(s) - 1);
+    CU_ASSERT(1 == res.size());
+    CU_ASSERT(std::make_pair(&s[1], &s[4]) == res[0].uri);
+  }
 }
 
 void test_http2_path_join(void) {