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Add audio encryption/decryption utilities (#573)
* Add audio encryption/decryption utilities * Fix comment typo Co-authored-by: lukasIO <[email protected]> --------- Co-authored-by: lukasIO <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,204 @@ | ||
| package lksdk | ||
|
|
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| import ( | ||
| "bytes" | ||
| "crypto/aes" | ||
| "crypto/cipher" | ||
| "crypto/rand" | ||
| "crypto/sha256" | ||
| "errors" | ||
| "io" | ||
|
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||
| "golang.org/x/crypto/hkdf" | ||
| "golang.org/x/crypto/pbkdf2" | ||
| ) | ||
|
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| const ( | ||
| LIVEKIT_SDK_SALT = "LKFrameEncryptionKey" | ||
| LIVEKIT_IV_LENGTH = 12 | ||
| LIVEKIT_PBKDF_ITERATIONS = 100000 | ||
| LIVEKIT_KEY_SIZE_BYTES = 16 | ||
| LIVEKIT_HKDF_INFO_BYTES = 128 | ||
| unencrypted_audio_bytes = 1 | ||
| ) | ||
|
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| var ErrIncorrectKeyLength = errors.New("incorrect key length for encryption/decryption") | ||
| var ErrUnableGenerateIV = errors.New("unable to generate iv for encryption") | ||
| var ErrIncorrectIVLength = errors.New("incorrect iv length") | ||
| var ErrIncorrectSecretLength = errors.New("input secret provided to derivation function cannot be empty or nil") | ||
| var ErrIncorrectSaltLength = errors.New("input salt provided to derivation function cannot be empty or nil") | ||
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| func DeriveKeyFromString(password string) ([]byte, error) { | ||
| return DeriveKeyFromStringCustomSalt(password, LIVEKIT_SDK_SALT) | ||
| } | ||
|
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| func DeriveKeyFromStringCustomSalt(password, salt string) ([]byte, error) { | ||
|
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| if password == "" { | ||
| return nil, ErrIncorrectSecretLength | ||
| } | ||
| if salt == "" { | ||
| return nil, ErrIncorrectSaltLength | ||
| } | ||
|
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| encPassword := []byte(password) | ||
| encSalt := []byte(salt) | ||
|
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| return pbkdf2.Key(encPassword, encSalt, LIVEKIT_PBKDF_ITERATIONS, LIVEKIT_KEY_SIZE_BYTES, sha256.New), nil | ||
|
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| } | ||
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| func DeriveKeyFromBytes(secret []byte) ([]byte, error) { | ||
| return DeriveKeyFromBytesCustomSalt(secret, LIVEKIT_SDK_SALT) | ||
| } | ||
|
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| func DeriveKeyFromBytesCustomSalt(secret []byte, salt string) ([]byte, error) { | ||
|
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| info := make([]byte, LIVEKIT_HKDF_INFO_BYTES) | ||
| encSalt := []byte(salt) | ||
|
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| if secret == nil { | ||
| return nil, ErrIncorrectSecretLength | ||
| } | ||
| if salt == "" { | ||
| return nil, ErrIncorrectSaltLength | ||
| } | ||
|
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| hkdfReader := hkdf.New(sha256.New, secret, encSalt, info) | ||
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| key := make([]byte, LIVEKIT_KEY_SIZE_BYTES) | ||
| _, err := io.ReadFull(hkdfReader, key) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
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| return key, nil | ||
|
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| } | ||
|
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| // Take audio sample (body of RTP) encrypted by LiveKit client SDK, extract IV and decrypt using provided key | ||
| // Encrypted sample format based on livekit client sdk | ||
| // ---------+-------------------------+---------+---- | ||
| // payload |IV...(length = IV_LENGTH)|IV_LENGTH|KID| | ||
| // ---------+-------------------------+---------+---- | ||
| // First byte of audio frame is not encrypted and only authenticated | ||
| // payload - variable bytes | ||
| // IV - variable bytes (equal to IV_LENGTH bytes) | ||
| // IV_LENGTH - 1 byte | ||
| // KID (Key ID) - 1 byte - ignored here, key is provided as parameter to function | ||
| func DecryptGCMAudioSample(sample, key, sifTrailer []byte) ([]byte, error) { | ||
|
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| if len(key) != 16 { | ||
| return nil, ErrIncorrectKeyLength | ||
| } | ||
|
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| if sifTrailer != nil && len(sample) >= len(sifTrailer) { | ||
| possibleTrailer := sample[len(sample)-len(sifTrailer):] | ||
| if bytes.Equal(possibleTrailer, sifTrailer) { | ||
| // this is unencrypted Server Injected Frame (SIF) that should be dropped | ||
| return nil, nil | ||
| } | ||
|
|
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| } | ||
|
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| // variable naming is kept close to LiveKit client SDK decrypt function | ||
| // https://github.com/livekit/client-sdk-js/blob/main/src/e2ee/worker/FrameCryptor.ts#L402 | ||
|
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| frameHeader := sample[:unencrypted_audio_bytes] // first unencrypted bytes are "frameHeader" and used for authentication later | ||
| frameTrailer := sample[len(sample)-2:] // last 2 bytes having IV_LENGTH and KID (1 byte each) | ||
| ivLength := int(frameTrailer[0]) // single byte, Endianness doesn't matter | ||
| ivStart := len(sample) - len(frameTrailer) - ivLength | ||
| if ivStart < 0 { | ||
| return nil, ErrIncorrectIVLength | ||
| } | ||
|
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| iv := make([]byte, ivLength) | ||
| copy(iv, sample[ivStart:ivStart+ivLength]) // copy IV value out of sample into iv | ||
|
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| cipherTextStart := len(frameHeader) | ||
| cipherTextLength := len(sample) - len(frameTrailer) - ivLength - len(frameHeader) | ||
| cipherText := make([]byte, cipherTextLength) | ||
| copy(cipherText, sample[cipherTextStart:cipherTextStart+cipherTextLength]) | ||
|
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| // setup AES | ||
| aesCipher, err := aes.NewCipher(key) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
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| aesGCM, err := cipher.NewGCMWithNonceSize(aesCipher, ivLength) // standard Nonce size is 12 bytes, but since it MAY be different in the sample, we use the one from the sample | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
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| // fmt.Println("**** DECRYPTION BEGIN ********") | ||
| plainText, err := aesGCM.Open(nil, iv, cipherText, frameHeader) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
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| newData := make([]byte, len(frameHeader)+len(plainText)) // allocate space for final packet | ||
|
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| _ = copy(newData[0:], frameHeader) // put unencrypted frameHeader first | ||
| _ = copy(newData[len(frameHeader):], plainText) // add decrypted remaining value | ||
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| return newData, nil | ||
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| } | ||
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| // Take audio sample (body of RTP) and encrypts it using AES-GCM 128bit with provided key | ||
| // Encrypted sample format based on livekit client sdk | ||
| // ---------+-------------------------+---------+---- | ||
| // payload |IV...(length = IV_LENGTH)|IV_LENGTH|KID| | ||
| // ---------+-------------------------+---------+---- | ||
| // First byte of audio frame is not encrypted and only authenticated | ||
| // payload - variable bytes | ||
| // IV - variable bytes (equal to IV_LENGTH bytes) - 12 random bytes | ||
| // IV_LENGTH - 1 byte - 12 bytes fixed | ||
| // KID (Key ID) - 1 byte - taken from "kid" parameter | ||
| func EncryptGCMAudioSample(sample, key []byte, kid uint8) ([]byte, error) { | ||
|
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| if len(key) != 16 { | ||
| return nil, ErrIncorrectKeyLength | ||
| } | ||
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| // variable naming is kept close to LiveKit client SDK decrypt function | ||
| // https://github.com/livekit/client-sdk-js/blob/main/src/e2ee/worker/FrameCryptor.ts#L402 | ||
|
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| frameHeader := append(make([]byte, 0), sample[:unencrypted_audio_bytes]...) // first unencrypted bytes are "frameHeader" and used for authentication later | ||
| iv := make([]byte, LIVEKIT_IV_LENGTH) | ||
| _, err := rand.Read(iv) | ||
| if err != nil { | ||
| return nil, errors.Join(ErrUnableGenerateIV, err) | ||
| } | ||
|
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| frameTrailer := []byte{LIVEKIT_IV_LENGTH, kid} // last 2 bytes having IV_LENGTH and KID (1 byte each) | ||
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| plainTextStart := len(frameHeader) | ||
| plainTextLength := len(sample) - len(frameHeader) | ||
| plainText := make([]byte, plainTextLength) | ||
| copy(plainText, sample[plainTextStart:plainTextStart+plainTextLength]) | ||
|
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| // setup AES | ||
| aesCipher, err := aes.NewCipher(key) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
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| aesGCM, err := cipher.NewGCMWithNonceSize(aesCipher, LIVEKIT_IV_LENGTH) // standard Nonce size is 12 bytes, but using one from defined constant (which matches Javascript SDK) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
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| cipherText := aesGCM.Seal(nil, iv, plainText, frameHeader) | ||
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| newData := make([]byte, len(frameHeader)+len(cipherText)+len(iv)+len(frameTrailer)) // allocate space for final packet | ||
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| _ = copy(newData[0:], frameHeader) // put unencrypted frameHeader first | ||
| _ = copy(newData[len(frameHeader):], cipherText) // add cipherText | ||
| _ = copy(newData[len(frameHeader)+len(cipherText):], iv) // add iv | ||
| _ = copy(newData[len(frameHeader)+len(cipherText)+len(iv):], frameTrailer) // add trailer | ||
|
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| return newData, nil | ||
|
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||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,80 @@ | ||
| package lksdk | ||
|
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| import ( | ||
| "testing" | ||
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| "github.com/stretchr/testify/assert" | ||
| ) | ||
|
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| var opusEncryptedFrame = []byte{120, 145, 24, 159, 76, 65, 130, 48, 144, 249, 17, 112, 134, 78, 250, 129, 171, 194, 16, 173, 73, 196, 5, 152, 69, 225, 28, 210, 196, 241, 226, 139, 231, 172, 51, 38, 139, 179, 245, 182, 170, 8, 122, 117, 98, 144, 123, 95, 73, 89, 119, 39, 205, 20, 191, 55, 121, 59, 239, 192, 85, 224, 228, 143, 10, 113, 195, 223, 118, 42, 2, 32, 22, 17, 77, 227, 109, 160, 245, 202, 189, 63, 162, 164, 5, 241, 24, 151, 45, 42, 165, 131, 171, 243, 141, 53, 35, 131, 141, 52, 253, 188, 12, 0} | ||
| var opusDecryptedFrame = []byte{120, 11, 109, 82, 113, 132, 189, 156, 220, 173, 30, 109, 87, 54, 173, 99, 26, 126, 166, 37, 127, 234, 110, 211, 230, 152, 181, 235, 197, 19, 140, 230, 179, 35, 131, 132, 29, 192, 97, 247, 108, 53, 183, 214, 77, 181, 173, 206, 175, 7, 228, 145, 93, 155, 155, 142, 14, 27, 111, 64, 96, 196, 229, 189, 142, 59, 149, 169, 99, 225, 216, 85, 186, 182} | ||
| var opusSilenceFrame = []byte{0xf8, 0xff, 0xfe, 0x00, 0x00, 0x00, 0x00, 0x00, | ||
| 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, | ||
| 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, | ||
| 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, | ||
| 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, | ||
| 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, | ||
| 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, | ||
| 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, | ||
| 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, | ||
| 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00} | ||
| var sifTrailer = []byte{50, 86, 10, 220, 108, 185, 57, 211} | ||
| var testPassphrase = "12345" | ||
|
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| func TestDeriveKeyFromString(t *testing.T) { | ||
|
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| password := "12345" | ||
|
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| key, err := DeriveKeyFromString(password) | ||
| expectedKey := []byte{15, 94, 198, 66, 93, 211, 116, 46, 55, 97, 232, 121, 189, 233, 224, 22} | ||
|
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| assert.Nil(t, err) | ||
| assert.Equal(t, key, expectedKey) | ||
| } | ||
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| func TestDeriveKeyFromBytes(t *testing.T) { | ||
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| inputSecret := []byte{34, 21, 187, 202, 134, 204, 168, 62, 5, 105, 40, 244, 88} | ||
| expectedKey := []byte{129, 224, 93, 62, 17, 203, 99, 136, 101, 35, 149, 128, 189, 152, 251, 76} | ||
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| key, err := DeriveKeyFromBytes(inputSecret) | ||
| assert.Nil(t, err) | ||
| assert.Equal(t, expectedKey, key) | ||
|
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| } | ||
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| func TestDecryptAudioSample(t *testing.T) { | ||
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| key, err := DeriveKeyFromString(testPassphrase) | ||
| assert.Nil(t, err) | ||
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| decryptedFrame, err := DecryptGCMAudioSample(opusEncryptedFrame, key, sifTrailer) | ||
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| assert.Nil(t, err) | ||
| assert.Equal(t, opusDecryptedFrame, decryptedFrame) | ||
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| var sifFrame []byte | ||
| sifFrame = append(sifFrame, opusSilenceFrame...) | ||
| sifFrame = append(sifFrame, sifTrailer...) | ||
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| decryptedFrame, err = DecryptGCMAudioSample(sifFrame, key, sifTrailer) | ||
| assert.Nil(t, err) | ||
| assert.Nil(t, decryptedFrame) | ||
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| } | ||
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| func TestEncryptAudioSample(t *testing.T) { | ||
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| key, err := DeriveKeyFromString(testPassphrase) | ||
| assert.Nil(t, err) | ||
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| encryptedFrame, err := EncryptGCMAudioSample(opusDecryptedFrame, key, 0) | ||
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| assert.Nil(t, err) | ||
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| // IV is generated randomly so to verify we decrypt and make sure that we got the expected plain text frame | ||
| decryptedFrame, err := DecryptGCMAudioSample(encryptedFrame, key, sifTrailer) | ||
| assert.Nil(t, err) | ||
| assert.Equal(t, opusDecryptedFrame, decryptedFrame) | ||
|
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||
| } |
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