Support validation of RFC 6531 international e-mail addresses

config.cmake.in

@@ -73,6 +73,7 @@ foreach(component ${SOURCEMETA_CORE_COMPONENTS})
   elseif(component STREQUAL "email")
     include("${CMAKE_CURRENT_LIST_DIR}/sourcemeta_core_ip.cmake")
     include("${CMAKE_CURRENT_LIST_DIR}/sourcemeta_core_dns.cmake")
+    include("${CMAKE_CURRENT_LIST_DIR}/sourcemeta_core_unicode.cmake")
     include("${CMAKE_CURRENT_LIST_DIR}/sourcemeta_core_email.cmake")
   elseif(component STREQUAL "uri")
     include("${CMAKE_CURRENT_LIST_DIR}/sourcemeta_core_io.cmake")

src/core/email/CMakeLists.txt

@@ -1,5 +1,5 @@
 sourcemeta_library(NAMESPACE sourcemeta PROJECT core NAME email
-  SOURCES email.cc)
+  SOURCES email.cc helpers.h)
 
 if(SOURCEMETA_CORE_INSTALL)
   sourcemeta_library_install(NAMESPACE sourcemeta PROJECT core NAME email)
@@ -9,3 +9,5 @@ target_link_libraries(sourcemeta_core_email
   PRIVATE sourcemeta::core::dns)
 target_link_libraries(sourcemeta_core_email
   PRIVATE sourcemeta::core::ip)
+target_link_libraries(sourcemeta_core_email
+  PRIVATE sourcemeta::core::unicode)

src/core/email/email.cc

@@ -1,110 +1,15 @@
 #include <sourcemeta/core/email.h>
 
 #include <sourcemeta/core/dns.h>
-#include <sourcemeta/core/ip.h>
 
-namespace sourcemeta::core {
-
-// RFC 5321 §4.1.2: atext = ALPHA / DIGIT / "!" / "#" / "$" / "%" /
-// "&" / "'" / "*" / "+" / "-" / "/" / "=" / "?" / "^" / "_" / "`" /
-// "{" / "|" / "}" / "~"
-static constexpr auto is_atext(const char character) -> bool {
-  switch (character) {
-    case '!':
-    case '#':
-    case '$':
-    case '%':
-    case '&':
-    case '\'':
-    case '*':
-    case '+':
-    case '-':
-    case '/':
-    case '=':
-    case '?':
-    case '^':
-    case '_':
-    case '`':
-    case '{':
-    case '|':
-    case '}':
-    case '~':
-      return true;
-    default:
-      return (character >= 'A' && character <= 'Z') ||
-             (character >= 'a' && character <= 'z') ||
-             (character >= '0' && character <= '9');
-  }
-}
-
-// RFC 5321 §4.1.2: qtextSMTP = %d32-33 / %d35-91 / %d93-126
-static constexpr auto is_qtext_smtp(const unsigned char character) -> bool {
-  return (character >= 32 && character <= 33) ||
-         (character >= 35 && character <= 91) ||
-         (character >= 93 && character <= 126);
-}
-
-// RFC 5321 §4.1.2: Let-dig = ALPHA / DIGIT
-static constexpr auto is_let_dig(const char character) -> bool {
-  return (character >= 'A' && character <= 'Z') ||
-         (character >= 'a' && character <= 'z') ||
-         (character >= '0' && character <= '9');
-}
-
-// RFC 5321 §4.1.3: dcontent = %d33-90 / %d94-126
-static constexpr auto is_dcontent(const unsigned char character) -> bool {
-  return (character >= 33 && character <= 90) ||
-         (character >= 94 && character <= 126);
-}
-
-// RFC 5321 §4.1.2: Ldh-str = *( ALPHA / DIGIT / "-" ) Let-dig
-// RFC 5321 §4.1.3: Standardized-tag = Ldh-str
-static constexpr auto is_ldh_str(const std::string_view value) -> bool {
-  if (value.empty() || !is_let_dig(value.back())) {
-    return false;
-  }
-  for (std::string_view::size_type position{0}; position + 1 < value.size();
-       position += 1) {
-    const auto character{value[position]};
-    if (!is_let_dig(character) && character != '-') {
-      return false;
-    }
-  }
-  return true;
-}
-
-// RFC 5234 §2.3: ABNF literal strings are case-insensitive by default
-// RFC 5321 §4.1.3: IPv6-address-literal prefix is the literal "IPv6:"
-static constexpr auto matches_ipv6_tag(const std::string_view value) -> bool {
-  return value.size() >= 5 && (value[0] == 'I' || value[0] == 'i') &&
-         (value[1] == 'P' || value[1] == 'p') &&
-         (value[2] == 'v' || value[2] == 'V') && value[3] == '6' &&
-         value[4] == ':';
-}
+#include "helpers.h"
 
-// RFC 5321 §4.1.3: General-address-literal = Standardized-tag ":" 1*dcontent
-static constexpr auto is_general_address_literal(const std::string_view value)
-    -> bool {
-  const auto colon_position{value.find(':')};
-  if (colon_position == std::string_view::npos) {
-    return false;
-  }
-  if (!is_ldh_str(value.substr(0, colon_position))) {
-    return false;
-  }
-  const auto content{value.substr(colon_position + 1)};
-  if (content.empty()) {
-    return false;
-  }
-  for (const auto character : content) {
-    if (!is_dcontent(static_cast<unsigned char>(character))) {
-      return false;
-    }
-  }
-  return true;
-}
+namespace sourcemeta::core {
 
-auto is_email(const std::string_view value) -> bool {
+// RFC 5321 §4.1.2 Mailbox grammar. When AllowUtf8 is true, RFC 6531 §3.3
+// extends atext, qtextSMTP, and sub-domain with UTF8-non-ascii alternatives
+template <bool AllowUtf8>
+static auto is_mailbox(const std::string_view value) -> bool {
   if (value.empty()) {
     return false;
   }
@@ -126,11 +31,23 @@ auto is_email(const std::string_view value) -> bool {
           return false;
         }
         position += 1;
-      } else {
-        if (!is_qtext_smtp(static_cast<unsigned char>(value[position]))) {
+        continue;
+      }
+
+      if (is_qtext_smtp(static_cast<unsigned char>(value[position]))) {
+        position += 1;
+        continue;
+      }
+
+      if constexpr (AllowUtf8) {
+        // RFC 6531 §3.3: qtextSMTP =/ UTF8-non-ascii
+        const auto utf8_length{utf8_codepoint_length(value, position)};
+        if (utf8_length < 2) {
           return false;
         }
-        position += 1;
+        position += utf8_length;
+      } else {
+        return false;
       }
     }
     if (position >= value.size()) {
@@ -150,13 +67,29 @@ auto is_email(const std::string_view value) -> bool {
         }
         previous_was_dot = true;
         atom_started = false;
-      } else if (is_atext(character)) {
+        position += 1;
+        continue;
+      }
+
+      if (is_atext(character)) {
         previous_was_dot = false;
         atom_started = true;
+        position += 1;
+        continue;
+      }
+
+      if constexpr (AllowUtf8) {
+        // RFC 6531 §3.3: atext =/ UTF8-non-ascii
+        const auto utf8_length{utf8_codepoint_length(value, position)};
+        if (utf8_length < 2) {
+          return false;
+        }
+        previous_was_dot = false;
+        atom_started = true;
+        position += utf8_length;
       } else {
         return false;
       }
-      position += 1;
     }
     if (position == 0 || previous_was_dot) {
       return false;
@@ -177,32 +110,26 @@ auto is_email(const std::string_view value) -> bool {
 
   // RFC 5321 §4.1.3: address-literal = "[" ( IPv4 / IPv6 / General ) "]"
   if (!domain.empty() && domain.front() == '[') {
-    if (domain.back() != ']') {
-      return false;
-    }
-    // RFC 5321 §4.5.3.1.2: 255-octet cap on a domain "name or number"
-    if (domain.size() > 255) {
-      return false;
-    }
-    const auto inner{domain.substr(1, domain.size() - 2)};
-    // RFC 5321 §4.1.3: IPv6-address-literal = "IPv6:" IPv6-addr
-    if (matches_ipv6_tag(inner) && is_ipv6(inner.substr(5))) {
-      return true;
-    }
-    // RFC 5234 §3.2: ABNF alternatives are unordered. A failed IPv6 match
-    // falls through to IPv4 or General-address-literal.
-    // RFC 5321 §4.1.3: IPv4-address-literal = Snum 3("." Snum) has no ":",
-    // General-address-literal requires ":"
-    if (inner.find(':') == std::string_view::npos) {
-      return is_ipv4(inner);
-    }
-    return is_general_address_literal(inner);
+    return is_address_literal(domain);
   }
 
-  // RFC 5321 §4.1.2 Domain matches is_hostname (RFC 1123 §2.1) by
-  // grammar, by 63-octet label cap (RFC 1035 §2.3.4), and by
-  // 255-octet total cap (RFC 5321 §4.5.3.1.2)
-  return is_hostname(domain);
+  if constexpr (AllowUtf8) {
+    // RFC 6531 §3.3: sub-domain =/ U-label
+    return is_idn_domain(domain);
+  } else {
+    // RFC 5321 §4.1.2 Domain matches is_hostname (RFC 1123 §2.1) by
+    // grammar, by 63-octet label cap (RFC 1035 §2.3.4), and by
+    // 255-octet total cap (RFC 5321 §4.5.3.1.2)
+    return is_hostname(domain);
+  }
+}
+
+auto is_email(const std::string_view value) -> bool {
+  return is_mailbox<false>(value);
+}
+
+auto is_idn_email(const std::string_view value) -> bool {
+  return is_mailbox<true>(value);
 }
 
 } // namespace sourcemeta::core