Commit incomplete ParseEmailAddress()

smtpd/utils.go

@@ -91,26 +91,35 @@ func ValidateDomainPart(domain string) bool {
 	return true
 }
 
-// ValidateLocalPart returns true if the string complies with RFC3696 recommendations
-func ValidateLocalPart(local string) bool {
-	length := len(local)
-	if 1 > length || length > 64 {
-		// Invalid length
-		return false
+// ParseEmailAddress unescapes an email address, and splits the local part from the domain part.
+// An error is returned if the local or domain parts fail validation following the guidelines
+// in RFC3696.
+func ParseEmailAddress(address string) (local string, domain string, err error) {
+	if address == "" {
+		return "", "", fmt.Errorf("Empty address")
 	}
-	if local[length-1] == '.' {
-		// Cannot end with a period
-		return false
+	if len(address) > 320 {
+		return "", "", fmt.Errorf("Address exceeds 320 characters")
+	}
+	if address[0] == '@' {
+		return "", "", fmt.Errorf("Address cannot start with @ symbol")
+	}
+	if address[0] == '.' {
+		return "", "", fmt.Errorf("Address cannot start with a period")
 	}
 
+	// Loop over address parsing out local part
+	buf := new(bytes.Buffer)
 	prev := byte('.')
 	inCharQuote := false
 	inStringQuote := false
-	for i := 0; i < length; i++ {
-		c := local[i]
+LOOP:
+	for i := 0; i < len(address); i++ {
+		c := address[i]
 		switch {
 		case ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z'):
 			// Letters are OK
+			buf.WriteByte(c)
 			inCharQuote = false
 		case '0' <= c && c <= '9':
 			// Numbers are OK
@@ -122,31 +131,57 @@ func ValidateLocalPart(local string) bool {
 			// A single period is OK
 			if prev == '.' {
 				// Sequence of periods is not permitted
-				return false
+				return "", "", fmt.Errorf("Sequence of periods is not permitted")
 			}
 		case c == '\\':
 			inCharQuote = true
 		case c == '"':
 			if inCharQuote {
 				inCharQuote = false
+			} else if inStringQuote {
+				inStringQuote = false
 			} else {
-				inStringQuote = !inStringQuote
+				if i == 0 {
+					inStringQuote = true
+				} else {
+					return "", "", fmt.Errorf("Quoted string can only begin at start of address")
+				}
+			}
+		case c == '@':
+			if inCharQuote || inStringQuote {
+				inCharQuote = false
+			} else {
+				// End of local-part
+				if i > 63 {
+					return "", "", fmt.Errorf("Local part must not exceed 64 characters")
+				}
+				if prev == '.' {
+					return "", "", fmt.Errorf("Local part cannot end with a period")
+				}
+				domain = address[i+1:]
+				break LOOP
 			}
 		case c > 127:
-			return false
+			return "", "", fmt.Errorf("Characters outside of US-ASCII range not permitted")
 		default:
 			if inCharQuote || inStringQuote {
 				inCharQuote = false
-				return true
+			} else {
+				return "", "", fmt.Errorf("Character %q must be quoted", c)
 			}
-			return false
 		}
 		prev = c
 	}
-	if inCharQuote || inStringQuote {
-		// Can't end with unused backslash quote or unterminated string quote
-		return false
+	if inCharQuote {
+		return "", "", fmt.Errorf("Cannot end address with unterminated quoted-pair")
+	}
+	if inStringQuote {
+		return "", "", fmt.Errorf("Cannot end address with unterminated string quote")
 	}
 
-	return true
+	if !ValidateDomainPart(domain) {
+		return "", "", fmt.Errorf("Domain part validation failed")
+	}
+
+	return buf.String(), domain, nil
 }