v0.1.3 bound parse memory and errors, conform better to toml spec for escpae and control chars

README.md

@@ -61,11 +61,18 @@ elements error, because TOML has no null value. Nil maps and slices encode as
 empty containers. Duplicate struct tag names error.
 
 Basic-string escapes emitted by the encoder (`\b`, `\f`, `\n`, `\r`, `\t`,
-quotes, backslashes, Unicode escapes) decode symmetrically. Invalid UTF-8 and
-unescaped control characters in strings are rejected. Encoding and typed decoding
+quotes, backslashes, Unicode escapes) decode symmetrically; the TOML 1.1 `\e`
+and `\xHH` decode too. Invalid UTF-8 and unescaped control characters in
+strings are rejected, as are control characters other than tab in comments and
+a carriage return outside CRLF. Encoding and typed decoding
 have recursion bounds (1000 levels), so cyclic traversals fail instead of
 overflowing the stack. Parsing bounds individual value nesting and dotted paths;
-combining paths can still produce trees that exceed the encoder's bound.
+combining paths can still produce trees that exceed the encoder's bound. A
+document may create at most `DefaultMaxTables` (65536) tables, counting every
+dotted-key segment and header part; set `Parser.MaxTables` before `Parse` to
+change it. Errors quote keys and cut long literals, and never repeat a string
+value. `Marshal` writes a table inline once its header path would pass 256
+bytes, so output stays linear in depth.
 
 Comments and original formatting are not preserved by `Parse`/`Marshal`. A
 configuration editor can scan the original bytes with `NewLexer` and retain
@@ -82,9 +89,10 @@ comment tokens. Stop scanning on `TokenEOF` or `TokenError`.
   unsupported.
 - Decimal integer keys (including quoted keys, optional signs and values beyond
   int64) are forbidden. This restriction also applies to the encoder.
-- Unknown string escapes are preserved verbatim as a documented relaxation.
-- Explicit table headers may reopen existing tables. Inline tables cannot be
-  extended later.
+- String escapes invalid in every TOML version are preserved verbatim as a
+  documented relaxation.
+- Explicit table headers may reopen existing tables, and dotted keys may extend
+  a table a header defined. Inline tables cannot be extended later.
 - Inline tables allow newlines and trailing commas. Arrays require commas,
   including between lines. Top-level statements require newline separation.
 - Signed radix integers and uppercase radix prefixes are accepted extensions.

audit_fix_test.go

@@ -1,6 +1,8 @@
 package toml
 
 import (
+	"errors"
+	"fmt"
 	"math"
 	"reflect"
 	"strconv"
@@ -200,3 +202,126 @@ func TestParser_ValueDepthLimit(t *testing.T) {
 		t.Error("expected nesting depth error")
 	}
 }
+
+// Each dotted-key segment and header part is a map; the document's budget of
+// them bounds memory, which input size alone does not (x167 for dotted keys).
+func TestParser_TableBudget(t *testing.T) {
+	doc := []byte("a" + strings.Repeat(".a", 101) + " = 1\n") // 101 maps
+	p := NewParser(doc)
+	p.MaxTables = 100
+	if _, err := p.Parse(); err == nil || !strings.Contains(err.Error(), "exceeds 100 tables") {
+		t.Fatalf("101 tables under a budget of 100: %v", err)
+	}
+	p = NewParser(doc)
+	p.MaxTables = 101
+	if _, err := p.Parse(); err != nil {
+		t.Fatalf("within budget: %v", err)
+	}
+	var b strings.Builder
+	for i := range DefaultMaxTables {
+		fmt.Fprintf(&b, "[t%d]\n", i)
+	}
+	if _, err := NewParser([]byte(b.String() + "[last]\n")).Parse(); err == nil {
+		t.Fatal("the default budget does not hold")
+	}
+}
+
+// TOML 1.1 escapes decode as TOML 1.1 readers decode them
+func TestLexer_TOML11Escapes(t *testing.T) {
+	m, err := NewParser([]byte(`s = "\x61\e\xe9"`)).Parse()
+	if err != nil || m["s"] != "a\x1bé" {
+		t.Fatalf("got %q, %v", m["s"], err)
+	}
+	if _, err := NewParser([]byte(`s = "\x6"`)).Parse(); err == nil {
+		t.Fatal(`\x with one hex digit accepted`)
+	}
+}
+
+// Outside strings a control character can only hide text from a reader: it
+// is refused in comments, and a CR is accepted only as part of CRLF.
+func TestLexer_ControlCharactersOutsideStrings(t *testing.T) {
+	for _, doc := range []string{
+		"a = 1 # see \x1b[8m\nb = 2",
+		"a = 1 # hidden\rb = 2\n",
+		"a = 1\rb = 2\n",
+		"a =\r1\n",
+		"a = 1 # del \x7f\n",
+	} {
+		if _, err := NewParser([]byte(doc)).Parse(); err == nil {
+			t.Errorf("%q accepted", doc)
+		}
+	}
+	m, err := NewParser([]byte("a = 1 # c\t\r\n[t] # d\r\nb = 2\r\n")).Parse()
+	if err != nil || m["a"] != int64(1) {
+		t.Fatalf("CRLF document: %v %v", m, err)
+	}
+}
+
+// The doubled brackets of an array-of-tables header are one delimiter
+func TestParser_ArrayTableDelimitersAdjacent(t *testing.T) {
+	for _, doc := range []string{"[ [a] ]\n", "[[a] ]\n", "[ [a]]\n"} {
+		if _, err := NewParser([]byte(doc)).Parse(); err == nil {
+			t.Errorf("%q accepted as a header", doc)
+		}
+	}
+	for _, doc := range []string{"[[a]]\n", "[ a ]\n", "[[ a ]]\n"} {
+		if _, err := NewParser([]byte(doc)).Parse(); err != nil {
+			t.Errorf("%q: %v", doc, err)
+		}
+	}
+}
+
+// Errors stay small and never carry a string's content, which may be a
+// secret (a verifier in a credentials file)
+func TestErrorsBoundedWithoutStringContent(t *testing.T) {
+	for _, doc := range []string{`stored_key "SECRETVALUE"`, `password = SECRETVALUE`} {
+		_, err := NewParser([]byte(doc + "\n")).Parse()
+		if err == nil || strings.Contains(err.Error(), "SECRET") {
+			t.Fatalf("value content in error: %v", err)
+		}
+	}
+	_, err := NewParser([]byte("n = 1" + strings.Repeat("0", 1<<20) + "\n")).Parse()
+	if err == nil || len(err.Error()) > 200 {
+		t.Fatalf("error of %d bytes", len(err.Error()))
+	}
+}
+
+// A decode error holds its path once, not a copy of the message per level
+func TestDecodeErrorPathIsLinear(t *testing.T) {
+	type deep map[string]deep
+	var data any = "not a table"
+	for range 500 {
+		data = map[string]any{"key": data}
+	}
+	err := Decode(data, new(deep))
+	var total int
+	for e := err; e != nil; e = errors.Unwrap(e) {
+		total += len(e.Error())
+	}
+	if err == nil || total > 3*len(err.Error()) {
+		t.Fatalf("messages along the chain: %d bytes for a %d-byte error", total, len(err.Error()))
+	}
+}
+
+// Header paths are bounded: deep nesting is written inline past the bound,
+// so output stays linear and still round-trips
+func TestMarshal_HeaderLengthBounded(t *testing.T) {
+	root := map[string]any{}
+	cur := root
+	for range 300 {
+		next := map[string]any{"v": int64(1)}
+		cur["long_key_0123"] = next
+		cur = next
+	}
+	out, err := Marshal(root)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(out) > 64*1024 {
+		t.Fatalf("%d bytes for 300 levels", len(out))
+	}
+	back, err := NewParser(out).Parse()
+	if err != nil || !reflect.DeepEqual(normalize(back), normalize(root)) {
+		t.Fatalf("round trip: %v", err)
+	}
+}

decode.go

@@ -40,6 +40,33 @@ func decodeValue(data any, val reflect.Value) error {
 	return decodeAt(data, val, 0)
 }
 
+// pathError names where decoding failed. Each level adds its segment instead
+// of wrapping the message, which would copy the message once per level.
+type pathError struct {
+	path []string // innermost first
+	err  error
+}
+
+func (e *pathError) Error() string {
+	var b strings.Builder
+	for i := len(e.path) - 1; i >= 0; i-- {
+		b.WriteString(e.path[i])
+		b.WriteString(": ")
+	}
+	b.WriteString(e.err.Error())
+	return b.String()
+}
+
+func (e *pathError) Unwrap() error { return e.err }
+
+func atPath(segment string, err error) error {
+	if pe, ok := err.(*pathError); ok {
+		pe.path = append(pe.path, segment)
+		return pe
+	}
+	return &pathError{path: []string{segment}, err: err}
+}
+
 func decodeAt(data any, val reflect.Value, depth int) error {
 	if depth > maxValueDepth {
 		return fmt.Errorf("decode nesting exceeds %d", maxValueDepth)
@@ -91,7 +118,7 @@ func decodeAt(data any, val reflect.Value, depth int) error {
 		}
 		for i := 0; i < len(dataSlice); i++ {
 			if err := decodeAt(dataSlice[i], newSlice.Index(i), depth+1); err != nil {
-				return fmt.Errorf("index %d: %w", i, err)
+				return atPath(fmt.Sprintf("index %d", i), err)
 			}
 		}
 		val.Set(newSlice)
@@ -109,7 +136,7 @@ func decodeAt(data any, val reflect.Value, depth int) error {
 		for k, vData := range dataMap {
 			newVal := reflect.New(elemType).Elem()
 			if err := decodeAt(vData, newVal, depth+1); err != nil {
-				return fmt.Errorf("map key %s: %w", k, err)
+				return atPath("map key "+brief(k), err)
 			}
 			newMap.SetMapIndex(reflect.ValueOf(k).Convert(val.Type().Key()), newVal)
 		}
@@ -206,7 +233,7 @@ func decodeStruct(data map[string]any, val reflect.Value, depth int) error {
 		// Look up in data map (case sensitive)
 		if vData, ok := data[key]; ok {
 			if err := decodeAt(vData, field, depth+1); err != nil {
-				return fmt.Errorf("%s.%s: %w", typ.Name(), fieldType.Name, err)
+				return atPath(typ.Name()+"."+fieldType.Name, err)
 			}
 		}
 	}

encode.go

@@ -109,6 +109,10 @@ func entries(v reflect.Value) ([]entry, error) {
 	return result, nil
 }
 
+// Every header repeats its table's full path, so deep nesting under headers
+// alone grows quadratically; past this length a table is written inline.
+const maxHeaderBytes = 256
+
 func (e *encoder) table(v reflect.Value, prefix string, depth int) error {
 	if depth > maxValueDepth {
 		return fmt.Errorf("encode nesting exceeds %d (possible cycle)", maxValueDepth)
@@ -119,11 +123,11 @@ func (e *encoder) table(v reflect.Value, prefix string, depth int) error {
 	}
 	var tables []entry
 	for _, x := range fields {
-		if isTable(x.value) || isTableArray(x.value) {
+		key, _ := keyText(x.key)
+		if (isTable(x.value) || isTableArray(x.value)) && len(prefix)+len(key) < maxHeaderBytes {
 			tables = append(tables, x)
 			continue
 		}
-		key, _ := keyText(x.key)
 		e.buf.WriteString(key + " = ")
 		if err := e.value(x.value, depth+1); err != nil {
 			return fmt.Errorf("key %q: %w", x.key, err)

fuzz_test.go

@@ -15,6 +15,9 @@ func FuzzParse(f *testing.F) {
 		"t = { a = 1, b = { c = [1, 2] } }",
 		`s = "esc \u00E9 \t"`,
 		"n = -0x10\nb = 0b101\no = 0o17",
+		"e = \"\\e\\x41\"\r\n# c\r\n[[a]]\r\n",
+		"a = 1 # \x1b[8m\nb = 2",
+		"[ [a] ]\nk =\r1",
 	} {
 		f.Add([]byte(s))
 	}

lexer.go

@@ -91,7 +91,7 @@ func (l *Lexer) NextToken() Token {
 	}
 
 	l.advance()
-	return l.newToken(TokenError, fmt.Sprintf("unexpected character: %c", ch))
+	return l.newToken(TokenError, fmt.Sprintf("unexpected character: %q", ch))
 }
 
 func (l *Lexer) readNumber() Token {
@@ -302,10 +302,12 @@ func (l *Lexer) peekAt(n int) rune {
 	return r
 }
 
+// skipWhitespace takes a CR only as part of CRLF: a lone one would let a
+// terminal hide what precedes it on the line, so it lexes as an error.
 func (l *Lexer) skipWhitespace() {
 	for l.pos < len(l.input) {
 		ch := l.peek()
-		if ch == ' ' || ch == '\t' || ch == '\r' {
+		if ch == ' ' || ch == '\t' || ch == '\r' && l.peekAt(1) == '\n' {
 			l.advance()
 		} else {
 			break
@@ -313,10 +315,19 @@ func (l *Lexer) skipWhitespace() {
 	}
 }
 
+// readComment refuses control characters but tab, as TOML does: an ESC or a
+// lone CR in a comment can hide the key after it from a reader.
 func (l *Lexer) readComment() Token {
 	l.advance() // '#'
 	start := l.pos
-	for l.pos < len(l.input) && l.peek() != '\n' {
+	for l.pos < len(l.input) {
+		ch := l.peek()
+		if ch == '\n' || ch == '\r' && l.peekAt(1) == '\n' {
+			break
+		}
+		if ch < 0x20 && ch != '\t' || ch == 0x7f {
+			return l.newToken(TokenError, fmt.Sprintf("control character %q in comment", ch))
+		}
 		l.advance()
 	}
 	return l.newToken(TokenComment, string(l.input[start:l.pos]))
@@ -357,12 +368,17 @@ func (l *Lexer) readString() Token {
 				result = append(result, '\b')
 			case 'f':
 				result = append(result, '\f')
-			case 'u', 'U':
-				n := 4
-				if ch == 'U' {
+			case 'e':
+				result = append(result, 0x1b)
+			case 'x', 'u', 'U':
+				n := 2
+				switch ch {
+				case 'u':
+					n = 4
+				case 'U':
 					n = 8
 				}
-				l.advance() // consume 'u'/'U'
+				l.advance() // consume 'x'/'u'/'U'
 				var code rune
 				for j := 0; j < n; j++ {
 					d, ok := hexDigitVal(l.peek())
@@ -383,7 +399,7 @@ func (l *Lexer) readString() Token {
 				escaped = false
 				continue // hex digits already consumed; skip trailing l.advance()
 			default:
-				// Unknown escape: preserve backslash and full rune
+				// Unknown escape, invalid in every TOML version: preserve backslash and full rune
 				result = append(result, '\\')
 				var buf [utf8.UTFMax]byte
 				n := utf8.EncodeRune(buf[:], ch)

parser.go

@@ -1,6 +1,8 @@
 package toml
 
 import (
+	"cmp"
+	"errors"
 	"fmt"
 	"reflect"
 	"strconv"
@@ -18,11 +20,19 @@ type Parser struct {
 	peekToken Token
 	// Value nesting depth (arrays / inline tables)
 	depth int
+	// Tables (maps) a document may create; 0 means DefaultMaxTables
+	MaxTables int
+	tables    int
 }
 
 // Recursion bound for parseValue -> parseArray/parseInlineTable
 const maxValueDepth = 1000
 
+// DefaultMaxTables bounds the maps one document creates. Every dotted-key
+// segment and header part is a map of about 350 bytes, so without a bound a
+// 10 MiB file of dotted keys holds near 2 GB.
+const DefaultMaxTables = 1 << 16
+
 func NewParser(input []byte) *Parser {
 	l := NewLexer(input)
 	p := &Parser{
@@ -36,6 +46,15 @@ func NewParser(input []byte) *Parser {
 	return p
 }
 
+// newTable makes a map, counted against the document's table budget
+func (p *Parser) newTable() (map[string]any, error) {
+	p.tables++
+	if limit := cmp.Or(p.MaxTables, DefaultMaxTables); p.tables > limit {
+		return nil, fmt.Errorf("document exceeds %d tables at line %d", limit, p.curToken.Line)
+	}
+	return make(map[string]any), nil
+}
+
 func (p *Parser) nextToken() {
 	p.curToken = p.peekToken
 	p.peekToken = p.lexer.NextToken()
@@ -81,10 +100,11 @@ func (p *Parser) parseStatement() error {
 	}
 }
 
-// parseTableDeclaration handles [key] and [[key]]
+// parseTableDeclaration handles [key] and [[key]]; the doubled brackets of
+// an array of tables are one delimiter, so "[ [a] ]" is no header
 func (p *Parser) parseTableDeclaration() error {
 	isArray := false
-	if p.peekToken.Type == TokenLBracket {
+	if p.peekToken.Type == TokenLBracket && adjacent(p.curToken, p.peekToken) {
 		// It is [[ ...
 		p.nextToken() // consume first [
 		isArray = true
@@ -98,8 +118,8 @@ func (p *Parser) parseTableDeclaration() error {
 	}
 
 	if isArray {
-		if p.curToken.Type != TokenRBracket {
-			return fmt.Errorf("expected closing bracket for array table at line %d", p.curToken.Line)
+		if p.curToken.Type != TokenRBracket || p.peekToken.Type != TokenRBracket || !adjacent(p.curToken, p.peekToken) {
+			return fmt.Errorf("expected ]] closing array table at line %d", p.curToken.Line)
 		}
 		p.nextToken() // consume first ]
 	}
@@ -122,7 +142,7 @@ func (p *Parser) setTableScope(keys []string, isArrayOfTables bool) error {
 		isLast := i == len(keys)-1
 		currentMap, ok := ptr.(map[string]any)
 		if !ok {
-			return fmt.Errorf("key path conflict: %s is not a map", key)
+			return fmt.Errorf("key path conflict: %q is not a map", key)
 		}
 
 		if isLast {
@@ -133,13 +153,16 @@ func (p *Parser) setTableScope(keys []string, isArrayOfTables bool) error {
 					if s, ok := val.([]map[string]any); ok {
 						slice = s
 					} else {
-						return fmt.Errorf("key conflict: %s is not an array of tables", key)
+						return fmt.Errorf("key conflict: %q is not an array of tables", key)
 					}
 				} else {
 					slice = make([]map[string]any, 0)
 				}
 
-				newMap := make(map[string]any)
+				newMap, err := p.newTable()
+				if err != nil {
+					return err
+				}
 				slice = append(slice, newMap)
 				currentMap[key] = slice
 				p.current = newMap
@@ -154,10 +177,13 @@ func (p *Parser) setTableScope(keys []string, isArrayOfTables bool) error {
 						}
 						targetMap = m
 					} else {
-						return fmt.Errorf("key conflict: %s is not a table", key)
+						return fmt.Errorf("key conflict: %q is not a table", key)
 					}
 				} else {
-					targetMap = make(map[string]any)
+					var err error
+					if targetMap, err = p.newTable(); err != nil {
+						return err
+					}
 					currentMap[key] = targetMap
 				}
 				p.current = targetMap
@@ -174,14 +200,17 @@ func (p *Parser) setTableScope(keys []string, isArrayOfTables bool) error {
 					ptr = m
 				} else if slice, ok := val.([]map[string]any); ok {
 					if len(slice) == 0 {
-						return fmt.Errorf("cannot traverse empty array table %s", key)
+						return fmt.Errorf("cannot traverse empty array table %q", key)
 					}
 					ptr = slice[len(slice)-1]
 				} else {
-					return fmt.Errorf("intermediate key %s is not a map", key)
+					return fmt.Errorf("intermediate key %q is not a map", key)
 				}
 			} else {
-				newMap := make(map[string]any)
+				newMap, err := p.newTable()
+				if err != nil {
+					return err
+				}
 				currentMap[key] = newMap
 				ptr = newMap
 			}
@@ -224,7 +253,7 @@ func (p *Parser) assignValue(scope any, keys []string, val any) error {
 		if i == len(keys)-1 {
 			// Final key, assign value
 			if _, exists := currentMap[key]; exists {
-				return fmt.Errorf("duplicate key %s at line %d", key, p.curToken.Line)
+				return fmt.Errorf("duplicate key %q at line %d", key, p.curToken.Line)
 			}
 			currentMap[key] = val
 		} else {
@@ -236,10 +265,13 @@ func (p *Parser) assignValue(scope any, keys []string, val any) error {
 					}
 					currentMap = m
 				} else {
-					return fmt.Errorf("intermediate key %s is not a map", key)
+					return fmt.Errorf("intermediate key %q is not a map", key)
 				}
 			} else {
-				newMap := make(map[string]any)
+				newMap, err := p.newTable()
+				if err != nil {
+					return err
+				}
 				currentMap[key] = newMap
 				currentMap = newMap
 			}
@@ -253,13 +285,13 @@ func (p *Parser) parseKeyParts() ([]string, error) {
 	for {
 		// Rule: Tokens identified as Numbers are forbidden as keys
 		if p.curToken.Type == TokenInteger || p.curToken.Type == TokenFloat {
-			return nil, fmt.Errorf("numeric keys are forbidden: %q", p.curToken.Literal)
+			return nil, fmt.Errorf("numeric keys are forbidden: %s", brief(p.curToken.Literal))
 		}
 
 		if p.curToken.Type == TokenString {
 			// Rule: Even quoted strings shouldn't be pure numbers per instruction
 			if numericKey(p.curToken.Literal) {
-				return nil, fmt.Errorf("numeric string keys are forbidden: %q", p.curToken.Literal)
+				return nil, fmt.Errorf("numeric string keys are forbidden: %s", brief(p.curToken.Literal))
 			}
 		}
 
@@ -298,14 +330,14 @@ func (p *Parser) parseValue() (any, error) {
 	case TokenInteger:
 		val, err := p.parseInteger(p.curToken.Literal)
 		if err != nil {
-			return nil, fmt.Errorf("invalid integer %q at line %d: %w", p.curToken.Literal, p.curToken.Line, err)
+			return nil, fmt.Errorf("invalid integer %s at line %d: %w", brief(p.curToken.Literal), p.curToken.Line, numCause(err))
 		}
 		p.nextToken()
 		return val, nil
 	case TokenFloat:
 		val, err := strconv.ParseFloat(p.curToken.Literal, 64)
 		if err != nil {
-			return nil, fmt.Errorf("invalid float %q at line %d: %w", p.curToken.Literal, p.curToken.Line, err)
+			return nil, fmt.Errorf("invalid float %s at line %d: %w", brief(p.curToken.Literal), p.curToken.Line, numCause(err))
 		}
 		p.nextToken()
 		return val, nil
@@ -318,6 +350,10 @@ func (p *Parser) parseValue() (any, error) {
 	case TokenLBrace:
 		return p.parseInlineTable()
 	}
+	if p.curToken.Type == TokenIdent {
+		// An unquoted value may be a secret: say what it is, not what it says
+		return nil, fmt.Errorf("unquoted value at line %d: strings need quotes", p.curToken.Line)
+	}
 	return nil, fmt.Errorf("unexpected value token %s at line %d", p.curToken.String(), p.curToken.Line)
 }
 
@@ -386,7 +422,10 @@ func (p *Parser) parseArray() ([]any, error) {
 
 func (p *Parser) parseInlineTable() (map[string]any, error) {
 	p.nextToken() // consume {
-	m := make(map[string]any)
+	m, err := p.newTable()
+	if err != nil {
+		return nil, err
+	}
 
 	for p.curToken.Type != TokenRBrace {
 		if p.curToken.Type == TokenNewline {
@@ -434,6 +473,25 @@ func (p *Parser) parseInlineTable() (map[string]any, error) {
 	return m, nil
 }
 
+// adjacent reports b starting right after the one-byte token a
+func adjacent(a, b Token) bool { return a.Line == b.Line && b.Col == a.Col+1 }
+
+// brief quotes s for an error, cut to 32 bytes: a literal can be megabytes
+func brief(s string) string {
+	if len(s) > 32 {
+		return fmt.Sprintf("%q... (%d bytes)", s[:32], len(s))
+	}
+	return fmt.Sprintf("%q", s)
+}
+
+// numCause drops strconv's copy of the literal, which brief already shows
+func numCause(err error) error {
+	if ne, ok := errors.AsType[*strconv.NumError](err); ok {
+		return ne.Err
+	}
+	return err
+}
+
 func signPrefix(negative bool) string {
 	if negative {
 		return "-"

token.go

@@ -46,6 +46,8 @@ func (t Token) String() string {
 		return fmt.Sprintf("Error(%s)", t.Literal)
 	case TokenNewline:
 		return "Newline"
+	case TokenString:
+		return "string" // its content may be a secret, as in a credentials file
 	}
 	if len(t.Literal) > 20 {
 		return fmt.Sprintf("%q...", t.Literal[:20])