Parse % string escapes

parser/declaration_parser.go

@@ -354,9 +354,13 @@ func (p *Parser) parseTableProperty() (*ast.TableProperty, error) {
 	if !p.expectPeek(token.STRING) {
 		return nil, errors.WithStack(UnexpectedToken(p.peekToken, "STRING"))
 	}
+	key, err := p.parseString()
+	if err != nil {
+		return nil, errors.WithStack(err)
+	}
 	prop := &ast.TableProperty{
 		Meta: p.curToken,
-		Key:  p.parseString(),
+		Key:  key,
 	}
 	prop.Key.Meta = clearComments(prop.Key.Meta)
 
@@ -371,7 +375,11 @@ func (p *Parser) parseTableProperty() (*ast.TableProperty, error) {
 	case token.IDENT:
 		prop.Value = p.parseIdent()
 	case token.STRING:
-		prop.Value = p.parseString()
+		var err error
+		prop.Value, err = p.parseString()
+		if err != nil {
+			return nil, errors.WithStack(err)
+		}
 	case token.ACL, token.BACKEND:
 		prop.Value = p.parseIdent()
 	case token.TRUE, token.FALSE:

parser/error.go

@@ -94,3 +94,10 @@ func EmptySwitch(m *ast.Meta) *ParseError {
 		Message: "Switch must have at least one case",
 	}
 }
+
+func InvalidEscape(m *ast.Meta, msg string) *ParseError {
+	return &ParseError{
+		Token:   m.Token,
+		Message: msg,
+	}
+}

parser/expression_parser.go

@@ -9,7 +9,7 @@ import (
 func (p *Parser) registerExpressionParsers() {
 	p.prefixParsers = map[token.TokenType]prefixParser{
 		token.IDENT:      func() (ast.Expression, error) { return p.parseIdent(), nil },
-		token.STRING:     func() (ast.Expression, error) { return p.parseString(), nil },
+		token.STRING:     func() (ast.Expression, error) { return p.parseString() },
 		token.INT:        func() (ast.Expression, error) { return p.parseInteger() },
 		token.FLOAT:      func() (ast.Expression, error) { return p.parseFloat() },
 		token.RTIME:      func() (ast.Expression, error) { return p.parseRTime() },

parser/statement_parser.go

@@ -105,7 +105,11 @@ func (p *Parser) parseIncludeStatement() (ast.Statement, error) {
 	if !p.expectPeek(token.STRING) {
 		return nil, errors.WithStack(UnexpectedToken(p.peekToken, "STRING"))
 	}
-	i.Module = p.parseString()
+	var err error
+	i.Module, err = p.parseString()
+	if err != nil {
+		return nil, errors.WithStack(err)
+	}
 	i.Meta.Trailing = p.trailing()
 
 	// Semicolons are actually not required at the end of include lines

parser/string_escape.go

@@ -0,0 +1,201 @@
+package parser
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+
+	"github.com/pkg/errors"
+)
+
+// Parse string escapes and return the resulting string with the decoded escaped
+// values.
+func decodeStringEscapes(s string) (string, error) {
+	var parsed string
+	r := bufio.NewReader(strings.NewReader(s))
+
+	for {
+		c, _, err := r.ReadRune()
+		if err == io.EOF {
+			break
+		}
+		if c == 0 {
+			break
+		}
+		if c == '%' {
+			var s string
+			if peek(r) == 'u' {
+				next(r)
+				s, err = codePointEscape(r)
+			} else {
+				s, err = utf8Escape(r)
+			}
+			// stop processing string on a null byte.
+			if err == NULLbyte {
+				break
+			} else if err != nil {
+				return "", err
+			}
+			parsed += s
+		} else {
+			parsed += string(c)
+		}
+	}
+
+	return parsed, nil
+}
+
+// isHex reports whether the rune is a hex digit.
+func isHex(c rune) bool {
+	return '0' <= c && c <= '9' || 'a' <= unicode.ToLower(c) && unicode.ToLower(c) <= 'f'
+}
+
+// Get int representation of provided hex digit.
+// Note: Assumes isHex has already been called.
+func digitVal(c rune) int {
+	if '0' <= c && c <= '9' {
+		return int(c - '0')
+	}
+	return int(unicode.ToLower(c) - 'a' + 10)
+}
+
+// Read two hex digits from the buffer and decode into an int.
+func readByte(r *bufio.Reader) (byte, error) {
+	var x byte
+
+	for i := 0; i < 2; i++ {
+		c, _, err := r.ReadRune()
+		if err != nil {
+			return 0, err
+		}
+		if !isHex(c) {
+			return 0, fmt.Errorf("invalid utf-8 escape, incomplete byte")
+		}
+		x = x*16 + byte(digitVal(c))
+	}
+
+	return x, nil
+}
+
+// Sentinel error for indicating the presence of a NULL byte or zero code point
+// in an escape.
+var NULLbyte = errors.New("NULL")
+
+// Convenience helper for checking the next rule in the buffer.
+func peek(r *bufio.Reader) rune {
+	b, err := r.Peek(1)
+	if err != nil {
+		return -1
+	}
+	return rune(b[0])
+}
+
+// Convenience helper to read a single rune from the buffer.
+// Should only be used after calling peek to ensure there is another rune in the
+// buffer.
+func next(r *bufio.Reader) rune {
+	c, _, _ := r.ReadRune() // nolint:errcheck
+	return c
+}
+
+// Decodes unicode code point escapes.
+// There are two forms of escapes.
+// * %XXXX
+// * %{...}
+func codePointEscape(r *bufio.Reader) (string, error) {
+	var min, max int
+
+	// Is the escape a fixed or variable width code point escape.
+	if peek(r) == '{' {
+		next(r)
+		min, max = 1, 6
+	} else {
+		min, max = 4, 4
+	}
+
+	// Read at least `min` hex digits up to `max`
+	var x int
+	for n := 0; n < max; n++ {
+		if !isHex(peek(r)) {
+			if n < min {
+				return "", fmt.Errorf("incomplete unicode escape. %d missing digits", min-n)
+			}
+			break
+		}
+		x = x*16 + digitVal(next(r))
+	}
+
+	if max == 6 {
+		if c := next(r); c != '}' {
+			return "", fmt.Errorf("incomplete %%{xxxx} escape")
+		}
+	}
+
+	// stop processing string on zero code point
+	if x == 0 {
+		return "", NULLbyte
+	}
+
+	if x > unicode.MaxRune {
+		return "", fmt.Errorf("invalid code point U+%x in unicode escape", x)
+	}
+
+	// Surrogate code points are not valid
+	if 0xD800 <= x && x <= 0xDFFF {
+		return "", fmt.Errorf("invalid surrogate code point U+%x in unicode escape", x)
+	}
+
+	return string(rune(x)), nil
+}
+
+// Decode sequences of %XX escapes.
+// Each byte in the sequence is a byte of a UTF-8 encoded character.
+// This escape type will include between 1 and 4 escaped bytes in the form of
+// %XX%YY
+func utf8Escape(r *bufio.Reader) (string, error) {
+	b1, err := readByte(r)
+	if err != nil {
+		return "", err
+	}
+	// Identify how many escape bytes need to be read
+	n := 0
+	switch {
+	case b1&(0x80) == 0: // 1 byte (ASCII)
+		if b1 == 0 {
+			return "", NULLbyte
+		}
+		return string(b1), nil
+	case b1&(0xe0) == 0xc0: // 2 bytes
+		n = 2
+	case b1&(0xf0) == 0xe0: // 3 bytes
+		n = 3
+	case b1&(0xf8) == 0xF0: // 4 bytes
+		n = 4
+	default:
+		return "", fmt.Errorf("utf-8 escape has invalid leading byte %x", b1)
+	}
+
+	// Read `n` additional byte escape sequences
+	bs := []byte{b1}
+	for i := 1; i < n; i++ {
+		if peek(r) != '%' {
+			return "", fmt.Errorf("incomplete utf-8 escape. %d missing bytes", n-i)
+		}
+		next(r)
+		b, err := readByte(r)
+		if err != nil {
+			return "", err
+		}
+		bs = append(bs, b)
+	}
+
+	c, _ := utf8.DecodeRune(bs)
+	if c == utf8.RuneError {
+		return "", fmt.Errorf("invalid utf-8 escape")
+	}
+
+	return string(c), nil
+}