diff --git a/rlp/decode.go b/rlp/decode.go index b340aa029e..9767809717 100644 --- a/rlp/decode.go +++ b/rlp/decode.go @@ -518,7 +518,7 @@ func decodeDecoder(s *Stream, val reflect.Value) error { } // Kind represents the kind of value contained in an RLP stream. -type Kind int +type Kind int8 const ( Byte Kind = iota @@ -561,22 +561,16 @@ type ByteReader interface { type Stream struct { r ByteReader - // number of bytes remaining to be read from r. - remaining uint64 - limited bool - - // auxiliary buffer for integer decoding - uintbuf []byte - - kind Kind // kind of value ahead - size uint64 // size of value ahead - byteval byte // value of single byte in type tag - kinderr error // error from last readKind - stack []listpos + remaining uint64 // number of bytes remaining to be read from r + size uint64 // size of value ahead + kinderr error // error from last readKind + stack []uint64 // list sizes + uintbuf [8]byte // auxiliary buffer for integer decoding + kind Kind // kind of value ahead + byteval byte // value of single byte in type tag + limited bool // true if input limit is in effect } -type listpos struct{ pos, size uint64 } - // NewStream creates a new decoding stream reading from r. // // If r implements the ByteReader interface, Stream will @@ -646,8 +640,8 @@ func (s *Stream) Raw() ([]byte, error) { s.kind = -1 // rearm Kind return []byte{s.byteval}, nil } - // the original header has already been read and is no longer - // available. read content and put a new header in front of it. + // The original header has already been read and is no longer + // available. Read content and put a new header in front of it. start := headsize(size) buf := make([]byte, uint64(start)+size) if err := s.readFull(buf[start:]); err != nil { @@ -730,7 +724,14 @@ func (s *Stream) List() (size uint64, err error) { if kind != List { return 0, ErrExpectedList } - s.stack = append(s.stack, listpos{0, size}) + + // Remove size of inner list from outer list before pushing the new size + // onto the stack. This ensures that the remaining outer list size will + // be correct after the matching call to ListEnd. + if inList, limit := s.listLimit(); inList { + s.stack[len(s.stack)-1] = limit - size + } + s.stack = append(s.stack, size) s.kind = -1 s.size = 0 return size, nil @@ -739,17 +740,13 @@ func (s *Stream) List() (size uint64, err error) { // ListEnd returns to the enclosing list. // The input reader must be positioned at the end of a list. func (s *Stream) ListEnd() error { - if len(s.stack) == 0 { + // Ensure that no more data is remaining in the current list. + if inList, listLimit := s.listLimit(); !inList { return errNotInList - } - tos := s.stack[len(s.stack)-1] - if tos.pos != tos.size { + } else if listLimit > 0 { return errNotAtEOL } s.stack = s.stack[:len(s.stack)-1] // pop - if len(s.stack) > 0 { - s.stack[len(s.stack)-1].pos += tos.size - } s.kind = -1 s.size = 0 return nil @@ -777,7 +774,7 @@ func (s *Stream) Decode(val interface{}) error { err = decoder(s, rval.Elem()) if decErr, ok := err.(*decodeError); ok && len(decErr.ctx) > 0 { - // add decode target type to error so context has more meaning + // Add decode target type to error so context has more meaning. decErr.ctx = append(decErr.ctx, fmt.Sprint("(", rtyp.Elem(), ")")) } return err @@ -800,6 +797,9 @@ func (s *Stream) Reset(r io.Reader, inputLimit uint64) { case *bytes.Reader: s.remaining = uint64(br.Len()) s.limited = true + case *bytes.Buffer: + s.remaining = uint64(br.Len()) + s.limited = true case *strings.Reader: s.remaining = uint64(br.Len()) s.limited = true @@ -818,10 +818,8 @@ func (s *Stream) Reset(r io.Reader, inputLimit uint64) { s.size = 0 s.kind = -1 s.kinderr = nil - if s.uintbuf == nil { - s.uintbuf = make([]byte, 8) - } s.byteval = 0 + s.uintbuf = [8]byte{} } // Kind returns the kind and size of the next value in the @@ -836,35 +834,29 @@ func (s *Stream) Reset(r io.Reader, inputLimit uint64) { // the value. Subsequent calls to Kind (until the value is decoded) // will not advance the input reader and return cached information. func (s *Stream) Kind() (kind Kind, size uint64, err error) { - var tos *listpos - if len(s.stack) > 0 { - tos = &s.stack[len(s.stack)-1] + if s.kind >= 0 { + return s.kind, s.size, s.kinderr } - if s.kind < 0 { - s.kinderr = nil - // Don't read further if we're at the end of the - // innermost list. - if tos != nil && tos.pos == tos.size { - return 0, 0, EOL - } - s.kind, s.size, s.kinderr = s.readKind() - if s.kinderr == nil { - if tos == nil { - // At toplevel, check that the value is smaller - // than the remaining input length. - if s.limited && s.size > s.remaining { - s.kinderr = ErrValueTooLarge - } - } else { - // Inside a list, check that the value doesn't overflow the list. - if s.size > tos.size-tos.pos { - s.kinderr = ErrElemTooLarge - } - } + + // Check for end of list. This needs to be done here because readKind + // checks against the list size, and would return the wrong error. + inList, listLimit := s.listLimit() + if inList && listLimit == 0 { + return 0, 0, EOL + } + // Read the actual size tag. + s.kind, s.size, s.kinderr = s.readKind() + if s.kinderr == nil { + // Check the data size of the value ahead against input limits. This + // is done here because many decoders require allocating an input + // buffer matching the value size. Checking it here protects those + // decoders from inputs declaring very large value size. + if inList && s.size > listLimit { + s.kinderr = ErrElemTooLarge + } else if s.limited && s.size > s.remaining { + s.kinderr = ErrValueTooLarge } } - // Note: this might return a sticky error generated - // by an earlier call to readKind. return s.kind, s.size, s.kinderr } @@ -891,37 +883,35 @@ func (s *Stream) readKind() (kind Kind, size uint64, err error) { s.byteval = b return Byte, 0, nil case b < 0xB8: - // Otherwise, if a string is 0-55 bytes long, - // the RLP encoding consists of a single byte with value 0x80 plus the - // length of the string followed by the string. The range of the first - // byte is thus [0x80, 0xB7]. + // Otherwise, if a string is 0-55 bytes long, the RLP encoding consists + // of a single byte with value 0x80 plus the length of the string + // followed by the string. The range of the first byte is thus [0x80, 0xB7]. return String, uint64(b - 0x80), nil case b < 0xC0: - // If a string is more than 55 bytes long, the - // RLP encoding consists of a single byte with value 0xB7 plus the length - // of the length of the string in binary form, followed by the length of - // the string, followed by the string. For example, a length-1024 string - // would be encoded as 0xB90400 followed by the string. The range of - // the first byte is thus [0xB8, 0xBF]. + // If a string is more than 55 bytes long, the RLP encoding consists of a + // single byte with value 0xB7 plus the length of the length of the + // string in binary form, followed by the length of the string, followed + // by the string. For example, a length-1024 string would be encoded as + // 0xB90400 followed by the string. The range of the first byte is thus + // [0xB8, 0xBF]. size, err = s.readUint(b - 0xB7) if err == nil && size < 56 { err = ErrCanonSize } return String, size, err case b < 0xF8: - // If the total payload of a list - // (i.e. the combined length of all its items) is 0-55 bytes long, the - // RLP encoding consists of a single byte with value 0xC0 plus the length - // of the list followed by the concatenation of the RLP encodings of the - // items. The range of the first byte is thus [0xC0, 0xF7]. + // If the total payload of a list (i.e. the combined length of all its + // items) is 0-55 bytes long, the RLP encoding consists of a single byte + // with value 0xC0 plus the length of the list followed by the + // concatenation of the RLP encodings of the items. The range of the + // first byte is thus [0xC0, 0xF7]. return List, uint64(b - 0xC0), nil default: - // If the total payload of a list is more than 55 bytes long, - // the RLP encoding consists of a single byte with value 0xF7 - // plus the length of the length of the payload in binary - // form, followed by the length of the payload, followed by - // the concatenation of the RLP encodings of the items. The - // range of the first byte is thus [0xF8, 0xFF]. + // If the total payload of a list is more than 55 bytes long, the RLP + // encoding consists of a single byte with value 0xF7 plus the length of + // the length of the payload in binary form, followed by the length of + // the payload, followed by the concatenation of the RLP encodings of + // the items. The range of the first byte is thus [0xF8, 0xFF]. size, err = s.readUint(b - 0xF7) if err == nil && size < 56 { err = ErrCanonSize @@ -940,22 +930,20 @@ func (s *Stream) readUint(size byte) (uint64, error) { return uint64(b), err default: start := int(8 - size) - for i := 0; i < start; i++ { - s.uintbuf[i] = 0 - } + s.uintbuf = [8]byte{} if err := s.readFull(s.uintbuf[start:]); err != nil { return 0, err } if s.uintbuf[start] == 0 { - // Note: readUint is also used to decode integer - // values. The error needs to be adjusted to become - // ErrCanonInt in this case. + // Note: readUint is also used to decode integer values. + // The error needs to be adjusted to become ErrCanonInt in this case. return 0, ErrCanonSize } - return binary.BigEndian.Uint64(s.uintbuf), nil + return binary.BigEndian.Uint64(s.uintbuf[:]), nil } } +// readFull reads into buf from the underlying stream. func (s *Stream) readFull(buf []byte) (err error) { if err := s.willRead(uint64(len(buf))); err != nil { return err @@ -977,6 +965,7 @@ func (s *Stream) readFull(buf []byte) (err error) { return err } +// readByte reads a single byte from the underlying stream. func (s *Stream) readByte() (byte, error) { if err := s.willRead(1); err != nil { return 0, err @@ -988,16 +977,16 @@ func (s *Stream) readByte() (byte, error) { return b, err } +// willRead is called before any read from the underlying stream. It checks +// n against size limits, and updates the limits if n doesn't overflow them. func (s *Stream) willRead(n uint64) error { s.kind = -1 // rearm Kind - if len(s.stack) > 0 { - // check list overflow - tos := s.stack[len(s.stack)-1] - if n > tos.size-tos.pos { + if inList, limit := s.listLimit(); inList { + if n > limit { return ErrElemTooLarge } - s.stack[len(s.stack)-1].pos += n + s.stack[len(s.stack)-1] = limit - n } if s.limited { if n > s.remaining { @@ -1007,3 +996,11 @@ func (s *Stream) willRead(n uint64) error { } return nil } + +// listLimit returns the amount of data remaining in the innermost list. +func (s *Stream) listLimit() (inList bool, limit uint64) { + if len(s.stack) == 0 { + return false, 0 + } + return true, s.stack[len(s.stack)-1] +}