package ncm import ( "bytes" "encoding/base64" "encoding/binary" "encoding/json" "errors" "github.com/unlock-music/cli/algo/common" "github.com/unlock-music/cli/internal/logging" "github.com/unlock-music/cli/internal/utils" "go.uber.org/zap" "io/ioutil" "net/http" "strings" ) var ( magicHeader = []byte{ 0x43, 0x54, 0x45, 0x4E, 0x46, 0x44, 0x41, 0x4D} keyCore = []byte{ 0x68, 0x7a, 0x48, 0x52, 0x41, 0x6d, 0x73, 0x6f, 0x35, 0x6b, 0x49, 0x6e, 0x62, 0x61, 0x78, 0x57} keyMeta = []byte{ 0x23, 0x31, 0x34, 0x6C, 0x6A, 0x6B, 0x5F, 0x21, 0x5C, 0x5D, 0x26, 0x30, 0x55, 0x3C, 0x27, 0x28} ) func NewDecoder(data []byte) common.Decoder { return &Decoder{ file: data, fileLen: uint32(len(data)), } } type Decoder struct { file []byte fileLen uint32 key []byte box []byte metaRaw []byte metaType string meta RawMeta cover []byte audio []byte offsetKey uint32 offsetMeta uint32 offsetCover uint32 offsetAudio uint32 } func (d *Decoder) Validate() error { if !bytes.Equal(magicHeader, d.file[:len(magicHeader)]) { return errors.New("ncm magic header not match") } d.offsetKey = 8 + 2 return nil } //todo: 读取前进行检查长度,防止越界 func (d *Decoder) readKeyData() error { if d.offsetKey == 0 || d.offsetKey+4 > d.fileLen { return errors.New("invalid cover file offset") } bKeyLen := d.file[d.offsetKey : d.offsetKey+4] iKeyLen := binary.LittleEndian.Uint32(bKeyLen) d.offsetMeta = d.offsetKey + 4 + iKeyLen bKeyRaw := make([]byte, iKeyLen) for i := uint32(0); i < iKeyLen; i++ { bKeyRaw[i] = d.file[i+4+d.offsetKey] ^ 0x64 } d.key = utils.PKCS7UnPadding(utils.DecryptAes128Ecb(bKeyRaw, keyCore))[17:] return nil } func (d *Decoder) readMetaData() error { if d.offsetMeta == 0 || d.offsetMeta+4 > d.fileLen { return errors.New("invalid meta file offset") } bMetaLen := d.file[d.offsetMeta : d.offsetMeta+4] iMetaLen := binary.LittleEndian.Uint32(bMetaLen) d.offsetCover = d.offsetMeta + 4 + iMetaLen if iMetaLen == 0 { return errors.New("no any meta file found") } // Why sub 22: Remove "163 key(Don't modify):" bKeyRaw := make([]byte, iMetaLen-22) for i := uint32(0); i < iMetaLen-22; i++ { bKeyRaw[i] = d.file[d.offsetMeta+4+22+i] ^ 0x63 } cipherText, err := base64.StdEncoding.DecodeString(string(bKeyRaw)) if err != nil { return errors.New("decode ncm meta failed: " + err.Error()) } metaRaw := utils.PKCS7UnPadding(utils.DecryptAes128Ecb(cipherText, keyMeta)) sepIdx := bytes.IndexRune(metaRaw, ':') if sepIdx == -1 { return errors.New("invalid ncm meta file") } d.metaType = string(metaRaw[:sepIdx]) d.metaRaw = metaRaw[sepIdx+1:] return nil } func (d *Decoder) buildKeyBox() { box := make([]byte, 256) for i := 0; i < 256; i++ { box[i] = byte(i) } keyLen := len(d.key) var j byte for i := 0; i < 256; i++ { j = box[i] + j + d.key[i%keyLen] box[i], box[j] = box[j], box[i] } d.box = make([]byte, 256) var _i byte for i := 0; i < 256; i++ { _i = byte(i + 1) si := box[_i] sj := box[_i+si] d.box[i] = box[si+sj] } } func (d *Decoder) parseMeta() error { switch d.metaType { case "music": d.meta = new(RawMetaMusic) return json.Unmarshal(d.metaRaw, d.meta) case "dj": d.meta = new(RawMetaDJ) return json.Unmarshal(d.metaRaw, d.meta) default: return errors.New("unknown ncm meta type: " + d.metaType) } } func (d *Decoder) readCoverData() error { if d.offsetCover == 0 || d.offsetCover+13 > d.fileLen { return errors.New("invalid cover file offset") } coverLenStart := d.offsetCover + 5 + 4 bCoverLen := d.file[coverLenStart : coverLenStart+4] iCoverLen := binary.LittleEndian.Uint32(bCoverLen) d.offsetAudio = coverLenStart + 4 + iCoverLen if iCoverLen == 0 { return errors.New("no any cover file found") } d.cover = d.file[coverLenStart+4 : 4+coverLenStart+iCoverLen] return nil } func (d *Decoder) readAudioData() error { if d.offsetAudio == 0 || d.offsetAudio > d.fileLen { return errors.New("invalid audio offset") } audioRaw := d.file[d.offsetAudio:] audioLen := len(audioRaw) d.audio = make([]byte, audioLen) for i := uint32(0); i < uint32(audioLen); i++ { d.audio[i] = d.box[i&0xff] ^ audioRaw[i] } return nil } func (d *Decoder) Decode() error { if err := d.readKeyData(); err != nil { return err } d.buildKeyBox() err := d.readMetaData() if err == nil { err = d.parseMeta() } if err != nil { logging.Log().Warn("parse ncm meta file failed", zap.Error(err)) } err = d.readCoverData() if err != nil { logging.Log().Warn("parse ncm cover file failed", zap.Error(err)) } return d.readAudioData() } func (d Decoder) GetAudioExt() string { if d.meta != nil { if format := d.meta.GetFormat(); format != "" { return "." + d.meta.GetFormat() } } return "" } func (d Decoder) GetAudioData() []byte { return d.audio } func (d Decoder) GetCoverImage() []byte { if d.cover != nil { return d.cover } { imgURL := d.meta.GetAlbumImageURL() if d.meta != nil && !strings.HasPrefix(imgURL, "http") { return nil } resp, err := http.Get(imgURL) if err != nil { logging.Log().Warn("download image failed", zap.Error(err), zap.String("url", imgURL)) return nil } defer resp.Body.Close() if resp.StatusCode != http.StatusOK { logging.Log().Warn("download image failed", zap.String("http", resp.Status), zap.String("url", imgURL)) return nil } data, err := ioutil.ReadAll(resp.Body) if err != nil { logging.Log().Warn("download image failed", zap.Error(err), zap.String("url", imgURL)) return nil } return data } } func (d Decoder) GetMeta() common.Meta { return d.meta } func init() { // Netease Mp3/Flac common.RegisterDecoder("ncm", NewDecoder) }