README.md

@@ -1,5 +1,5 @@
 # Notice
-Widevine code has been deleted in response to a takedown request.  The Hulu API package still functions.
+Widevine is currently revoking a lot of keys.  This program won't work unless you have your own Widevine key and device information (I do not have any working keys).
 
 # Hulu Downloader
 The code in this repository allows you to download videos unencumbered with DRM from Hulu.  The code in `widevine` is in general independent of the Hulu related code and can be used for Widevine license generation/decryption.  The code in `client` is also standalone but only implements a handful of Hulu API endpoints that are basically only useful for a tool of this nature.

widevine/cdm.go

@@ -0,0 +1,276 @@
+package widevine
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rsa"
+	"crypto/sha1"
+	"crypto/x509"
+	"encoding/pem"
+	"errors"
+	"math"
+	"time"
+
+	"github.com/aead/cmac"
+	"google.golang.org/protobuf/proto"
+	"lukechampine.com/frand"
+)
+
+type CDM struct {
+	privateKey *rsa.PrivateKey
+	clientID   []byte
+	sessionID  [32]byte
+
+	widevineCencHeader      WidevineCencHeader
+	signedDeviceCertificate SignedDeviceCertificate
+	privacyMode             bool
+}
+
+type Key struct {
+	ID    []byte
+	Type  License_KeyContainer_KeyType
+	Value []byte
+}
+
+// Creates a new CDM object with the specified device information.
+func NewCDM(privateKey, clientID, initData []byte) (CDM, error) {
+	block, _ := pem.Decode(privateKey)
+	if block == nil || (block.Type != "PRIVATE KEY" && block.Type != "RSA PRIVATE KEY") {
+		return CDM{}, errors.New("failed to decode device private key")
+	}
+
+	keyParsed, err := x509.ParsePKCS1PrivateKey(block.Bytes)
+	if err != nil {
+		// if PCKS1 doesn't work, try PCKS8
+		pcks8Key, err := x509.ParsePKCS8PrivateKey(block.Bytes)
+		if err != nil {
+			return CDM{}, err
+		}
+		keyParsed = pcks8Key.(*rsa.PrivateKey)
+	}
+
+	var widevineCencHeader WidevineCencHeader
+	if len(initData) < 32 {
+		return CDM{}, errors.New("initData not long enough")
+	}
+	if err := proto.Unmarshal(initData[32:], &widevineCencHeader); err != nil {
+		return CDM{}, err
+	}
+
+	sessionID := func() (s [32]byte) {
+		c := []byte("ABCDEF0123456789")
+		for i := 0; i < 16; i++ {
+			s[i] = c[frand.Intn(len(c))]
+		}
+		s[16] = '0'
+		s[17] = '1'
+		for i := 18; i < 32; i++ {
+			s[i] = '0'
+		}
+		return s
+	}()
+
+	return CDM{
+		privateKey: keyParsed,
+		clientID:   clientID,
+
+		widevineCencHeader: widevineCencHeader,
+
+		sessionID: sessionID,
+	}, nil
+}
+
+// Creates a new CDM object using the default device configuration.
+func NewDefaultCDM(initData []byte) (CDM, error) {
+	return NewCDM(DefaultPrivateKey, DefaultClientID, initData)
+}
+
+// Sets a device certificate.  This is makes generating the license request
+// more complicated but is supported.  This is usually not necessary for most
+// Widevine applications.
+func (c *CDM) SetServiceCertificate(certData []byte) error {
+	var message SignedMessage
+	if err := proto.Unmarshal(certData, &message); err != nil {
+		return err
+	}
+	if err := proto.Unmarshal(message.Msg, &c.signedDeviceCertificate); err != nil {
+		return err
+	}
+	c.privacyMode = true
+	return nil
+}
+
+// Generates the license request data.  This is sent to the license server via
+// HTTP POST and the server in turn returns the license response.
+func (c *CDM) GetLicenseRequest() ([]byte, error) {
+	var licenseRequest SignedLicenseRequest
+	licenseRequest.Msg = new(LicenseRequest)
+	licenseRequest.Msg.ContentId = new(LicenseRequest_ContentIdentification)
+	licenseRequest.Msg.ContentId.CencId = new(LicenseRequest_ContentIdentification_CENC)
+
+	// this is probably really bad for the GC but protobuf uses pointers for optional
+	// fields so it is necessary and this is not a long running program
+	{
+		v := SignedLicenseRequest_LICENSE_REQUEST
+		licenseRequest.Type = &v
+	}
+
+	licenseRequest.Msg.ContentId.CencId.Pssh = &c.widevineCencHeader
+
+	{
+		v := LicenseType_DEFAULT
+		licenseRequest.Msg.ContentId.CencId.LicenseType = &v
+	}
+
+	licenseRequest.Msg.ContentId.CencId.RequestId = c.sessionID[:]
+
+	{
+		v := LicenseRequest_NEW
+		licenseRequest.Msg.Type = &v
+	}
+
+	{
+		v := uint32(time.Now().Unix())
+		licenseRequest.Msg.RequestTime = &v
+	}
+
+	{
+		v := ProtocolVersion_CURRENT
+		licenseRequest.Msg.ProtocolVersion = &v
+	}
+
+	{
+		v := uint32(frand.Uint64n(math.MaxUint32))
+		licenseRequest.Msg.KeyControlNonce = &v
+	}
+
+	if c.privacyMode {
+		pad := func(data []byte, blockSize int) []byte {
+			padlen := blockSize - (len(data) % blockSize)
+			if padlen == 0 {
+				padlen = blockSize
+			}
+			return append(data, bytes.Repeat([]byte{byte(padlen)}, padlen)...)
+		}
+		const blockSize = 16
+
+		var cidKey, cidIV [blockSize]byte
+		frand.Read(cidKey[:])
+		frand.Read(cidIV[:])
+
+		block, err := aes.NewCipher(cidKey[:])
+		if err != nil {
+			return nil, err
+		}
+
+		paddedClientID := pad(c.clientID, blockSize)
+		encryptedClientID := make([]byte, len(paddedClientID))
+		cipher.NewCBCEncrypter(block, cidIV[:]).CryptBlocks(encryptedClientID, paddedClientID)
+
+		servicePublicKey, err := x509.ParsePKCS1PublicKey(c.signedDeviceCertificate.XDeviceCertificate.PublicKey)
+		if err != nil {
+			return nil, err
+		}
+
+		encryptedCIDKey, err := rsa.EncryptOAEP(sha1.New(), frand.Reader, servicePublicKey, cidKey[:], nil)
+		if err != nil {
+			return nil, err
+		}
+
+		licenseRequest.Msg.EncryptedClientId = new(EncryptedClientIdentification)
+		{
+			v := string(c.signedDeviceCertificate.XDeviceCertificate.ServiceId)
+			licenseRequest.Msg.EncryptedClientId.ServiceId = &v
+		}
+		licenseRequest.Msg.EncryptedClientId.ServiceCertificateSerialNumber = c.signedDeviceCertificate.XDeviceCertificate.SerialNumber
+		licenseRequest.Msg.EncryptedClientId.EncryptedClientId = encryptedClientID
+		licenseRequest.Msg.EncryptedClientId.EncryptedClientIdIv = cidIV[:]
+		licenseRequest.Msg.EncryptedClientId.EncryptedPrivacyKey = encryptedCIDKey
+	} else {
+		licenseRequest.Msg.ClientId = new(ClientIdentification)
+		if err := proto.Unmarshal(c.clientID, licenseRequest.Msg.ClientId); err != nil {
+			return nil, err
+		}
+	}
+
+	{
+		data, err := proto.Marshal(licenseRequest.Msg)
+		if err != nil {
+			return nil, err
+		}
+		hash := sha1.Sum(data)
+		if licenseRequest.Signature, err = rsa.SignPSS(frand.Reader, c.privateKey, crypto.SHA1, hash[:], &rsa.PSSOptions{SaltLength: rsa.PSSSaltLengthEqualsHash}); err != nil {
+			return nil, err
+		}
+	}
+
+	return proto.Marshal(&licenseRequest)
+}
+
+// Retrieves the keys from the license response data.  These keys can be
+// used to decrypt the DASH-MP4.
+func (c *CDM) GetLicenseKeys(licenseRequest []byte, licenseResponse []byte) (keys []Key, err error) {
+	var license SignedLicense
+	if err = proto.Unmarshal(licenseResponse, &license); err != nil {
+		return
+	}
+
+	var licenseRequestParsed SignedLicenseRequest
+	if err = proto.Unmarshal(licenseRequest, &licenseRequestParsed); err != nil {
+		return
+	}
+	licenseRequestMsg, err := proto.Marshal(licenseRequestParsed.Msg)
+	if err != nil {
+		return
+	}
+
+	sessionKey, err := rsa.DecryptOAEP(sha1.New(), frand.Reader, c.privateKey, license.SessionKey, nil)
+	if err != nil {
+		return
+	}
+
+	sessionKeyBlock, err := aes.NewCipher(sessionKey)
+	if err != nil {
+		return
+	}
+
+	encryptionKey := []byte{1, 'E', 'N', 'C', 'R', 'Y', 'P', 'T', 'I', 'O', 'N', 0}
+	encryptionKey = append(encryptionKey, licenseRequestMsg...)
+	encryptionKey = append(encryptionKey, []byte{0, 0, 0, 0x80}...)
+	encryptionKeyCmac, err := cmac.Sum(encryptionKey, sessionKeyBlock, sessionKeyBlock.BlockSize())
+	if err != nil {
+		return
+	}
+	encryptionKeyCipher, err := aes.NewCipher(encryptionKeyCmac)
+	if err != nil {
+		return
+	}
+
+	unpad := func(b []byte) []byte {
+		if len(b) == 0 {
+			return b
+		}
+		// pks padding is designed so that the value of all the padding bytes is
+		// the number of padding bytes repeated so to figure out how many
+		// padding bytes there are we can just look at the value of the last
+		// byte
+		// i.e if there are 6 padding bytes then it will look at like
+		// <data> 0x6 0x6 0x6 0x6 0x6 0x6
+		count := int(b[len(b)-1])
+		return b[0 : len(b)-count]
+	}
+	for _, key := range license.Msg.Key {
+		decrypter := cipher.NewCBCDecrypter(encryptionKeyCipher, key.Iv)
+		decryptedKey := make([]byte, len(key.Key))
+		decrypter.CryptBlocks(decryptedKey, key.Key)
+		keys = append(keys, Key{
+			ID:    key.Id,
+			Type:  *key.Type,
+			Value: unpad(decryptedKey),
+		})
+	}
+
+	return
+}

widevine/pssh.go

@@ -0,0 +1,115 @@
+package widevine
+
+import (
+	"bytes"
+	"encoding/base64"
+	"encoding/xml"
+	"errors"
+	"io"
+	"net/http"
+)
+
+// This function retrieves the PSSH/Init Data from a given MPD file reader.
+// Example file: https://bitmovin-a.akamaihd.net/content/art-of-motion_drm/mpds/11331.mpd
+func InitDataFromMPD(r io.Reader) ([]byte, error) {
+	type mpd struct {
+		XMLName                   xml.Name `xml:"MPD"`
+		Text                      string   `xml:",chardata"`
+		ID                        string   `xml:"id,attr"`
+		Profiles                  string   `xml:"profiles,attr"`
+		Type                      string   `xml:"type,attr"`
+		AvailabilityStartTime     string   `xml:"availabilityStartTime,attr"`
+		PublishTime               string   `xml:"publishTime,attr"`
+		MediaPresentationDuration string   `xml:"mediaPresentationDuration,attr"`
+		MinBufferTime             string   `xml:"minBufferTime,attr"`
+		Version                   string   `xml:"version,attr"`
+		Ns2                       string   `xml:"ns2,attr"`
+		Xmlns                     string   `xml:"xmlns,attr"`
+		Bitmovin                  string   `xml:"bitmovin,attr"`
+		Period                    struct {
+			Text          string `xml:",chardata"`
+			AdaptationSet []struct {
+				Text            string `xml:",chardata"`
+				MimeType        string `xml:"mimeType,attr"`
+				Codecs          string `xml:"codecs,attr"`
+				Lang            string `xml:"lang,attr"`
+				Label           string `xml:"label,attr"`
+				SegmentTemplate struct {
+					Text           string `xml:",chardata"`
+					Media          string `xml:"media,attr"`
+					Initialization string `xml:"initialization,attr"`
+					Duration       string `xml:"duration,attr"`
+					StartNumber    string `xml:"startNumber,attr"`
+					Timescale      string `xml:"timescale,attr"`
+				} `xml:"SegmentTemplate"`
+				ContentProtection []struct {
+					Text        string `xml:",chardata"`
+					SchemeIdUri string `xml:"schemeIdUri,attr"`
+					Value       string `xml:"value,attr"`
+					DefaultKID  string `xml:"default_KID,attr"`
+					Pssh        string `xml:"pssh"`
+				} `xml:"ContentProtection"`
+				Representation []struct {
+					Text              string `xml:",chardata"`
+					ID                string `xml:"id,attr"`
+					Bandwidth         string `xml:"bandwidth,attr"`
+					Width             string `xml:"width,attr"`
+					Height            string `xml:"height,attr"`
+					FrameRate         string `xml:"frameRate,attr"`
+					AudioSamplingRate string `xml:"audioSamplingRate,attr"`
+					ContentProtection []struct {
+						Text        string `xml:",chardata"`
+						SchemeIdUri string `xml:"schemeIdUri,attr"`
+						Value       string `xml:"value,attr"`
+						DefaultKID  string `xml:"default_KID,attr"`
+						Cenc        string `xml:"cenc,attr"`
+						Pssh        struct {
+							Text string `xml:",chardata"`
+							Cenc string `xml:"cenc,attr"`
+						} `xml:"pssh"`
+					} `xml:"ContentProtection"`
+				} `xml:"Representation"`
+				AudioChannelConfiguration struct {
+					Text        string `xml:",chardata"`
+					SchemeIdUri string `xml:"schemeIdUri,attr"`
+					Value       string `xml:"value,attr"`
+				} `xml:"AudioChannelConfiguration"`
+			} `xml:"AdaptationSet"`
+		} `xml:"Period"`
+	}
+
+	var mpdPlaylist mpd
+	if err := xml.NewDecoder(r).Decode(&mpdPlaylist); err != nil {
+		return nil, err
+	}
+
+	const widevineSchemeIdURI = "urn:uuid:edef8ba9-79d6-4ace-a3c8-27dcd51d21ed"
+	for _, adaptionSet := range mpdPlaylist.Period.AdaptationSet {
+		for _, protection := range adaptionSet.ContentProtection {
+			if protection.SchemeIdUri == widevineSchemeIdURI && len(protection.Pssh) > 0 {
+				return base64.StdEncoding.DecodeString(protection.Pssh)
+			}
+		}
+	}
+	for _, adaptionSet := range mpdPlaylist.Period.AdaptationSet {
+		for _, representation := range adaptionSet.Representation {
+			for _, protection := range representation.ContentProtection {
+				if protection.SchemeIdUri == widevineSchemeIdURI && len(protection.Pssh.Text) > 0 {
+					return base64.StdEncoding.DecodeString(protection.Pssh.Text)
+				}
+			}
+		}
+	}
+
+	return nil, errors.New("no init data found")
+}
+
+// This function retrieves certificate data from a given license server.
+func GetCertData(client *http.Client, licenseURL string) ([]byte, error) {
+	response, err := client.Post(licenseURL, "application/x-www-form-urlencoded", bytes.NewReader([]byte{0x08, 0x04}))
+	if err != nil {
+		return nil, err
+	}
+	defer response.Body.Close()
+	return io.ReadAll(response.Body)
+}