Pass visitorData to requests

This is a nearly verbatim copy of [1], for now the code is pretty rough and
I'm not even sure that this data should be passed for all requests but it
does seem to unblock the iOS client for now.

[1] TeamNewPipe/NewPipeExtractor#1262

client.go

@@ -12,7 +12,9 @@ import (
 	"net/http"
 	"net/url"
 	"strconv"
+	"strings"
 	"sync/atomic"
+	"time"
 )
 
 const (
@@ -23,6 +25,8 @@ const (
 	playerParams = "CgIQBg=="
 )
 
+const CONTENT_PLAYBACK_NONCE_ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"
+
 var ErrNoFormat = errors.New("no video format provided")
 
 // DefaultClient type to use. No reason to change but you could if you wanted to.
@@ -157,6 +161,7 @@ type innertubeClient struct {
 	TimeZone          string `json:"timeZone"`
 	UTCOffset         int    `json:"utcOffsetMinutes"`
 	DeviceModel       string `json:"deviceModel,omitempty"`
+	VisitorData       string `json:"visitorData,omitempty"`
 }
 
 // client info for the innertube API
@@ -232,6 +237,33 @@ func (c *Client) transcriptDataByInnertube(ctx context.Context, id string, lang
 	return c.httpPostBodyBytes(ctx, "https://www.youtube.com/youtubei/v1/get_transcript?key="+c.client.key, data)
 }
 
+func randString(alphabet string, sz int) string {
+	var buf strings.Builder
+	buf.Grow(sz)
+	for i := 0; i < sz; i++ {
+		buf.WriteByte(alphabet[rand.Intn(len(alphabet))])
+	}
+	return buf.String()
+}
+
+func randomVisitorData(countryCode string) string {
+	var pbE2 ProtoBuilder
+
+	pbE2.String(2, "")
+	pbE2.Varint(4, int64(rand.Intn(255)+1))
+
+	var pbE ProtoBuilder
+	pbE.String(1, countryCode)
+	pbE.Bytes(2, pbE2.ToBytes())
+
+	var pb ProtoBuilder
+	pb.String(1, randString(CONTENT_PLAYBACK_NONCE_ALPHABET, 11))
+	pb.Varint(5, time.Now().Unix()-int64(rand.Intn(600000)))
+	pb.Bytes(6, pbE.ToBytes())
+
+	return pb.ToUrlEncodedBase64()
+}
+
 func prepareInnertubeContext(clientInfo clientInfo) inntertubeContext {
 	return inntertubeContext{
 		Client: innertubeClient{
@@ -243,6 +275,7 @@ func prepareInnertubeContext(clientInfo clientInfo) inntertubeContext {
 			ClientVersion:     clientInfo.version,
 			AndroidSDKVersion: clientInfo.androidVersion,
 			UserAgent:         clientInfo.userAgent,
+			VisitorData:       randomVisitorData("US"),
 		},
 	}
 }

protobuilder.go

@@ -0,0 +1,73 @@
+package youtube
+
+import (
+	"bytes"
+	"encoding/base64"
+	"net/url"
+)
+
+type ProtoBuilder struct {
+	byteBuffer bytes.Buffer
+}
+
+func (pb *ProtoBuilder) ToBytes() []byte {
+	return pb.byteBuffer.Bytes()
+}
+
+func (pb *ProtoBuilder) ToUrlEncodedBase64() string {
+	b64 := base64.URLEncoding.EncodeToString(pb.ToBytes())
+	return url.QueryEscape(b64)
+}
+
+func (pb *ProtoBuilder) writeVarint(val int64) error {
+	if val == 0 {
+		_, err := pb.byteBuffer.Write([]byte{0})
+		return err
+	}
+	for {
+		b := byte(val & 0x7F)
+		val >>= 7
+		if val != 0 {
+			b |= 0x80
+		}
+		_, err := pb.byteBuffer.Write([]byte{b})
+		if err != nil {
+			return err
+		}
+		if val == 0 {
+			break
+		}
+	}
+	return nil
+}
+
+func (pb *ProtoBuilder) field(field int, wireType byte) error {
+	val := int64(field<<3) | int64(wireType&0x07)
+	return pb.writeVarint(val)
+}
+
+func (pb *ProtoBuilder) Varint(field int, val int64) error {
+	err := pb.field(field, 0)
+	if err != nil {
+		return err
+	}
+	return pb.writeVarint(val)
+}
+
+func (pb *ProtoBuilder) String(field int, stringVal string) error {
+	strBts := []byte(stringVal)
+	return pb.Bytes(field, strBts)
+}
+
+func (pb *ProtoBuilder) Bytes(field int, bytesVal []byte) error {
+	if err := pb.field(field, 2); err != nil {
+		return err
+	}
+
+	if err := pb.writeVarint(int64(len(bytesVal))); err != nil {
+		return err
+	}
+
+	_, err := pb.byteBuffer.Write(bytesVal)
+	return err
+}