|
| 1 | +package voice |
| 2 | + |
| 3 | +import ( |
| 4 | + "crypto/aes" |
| 5 | + "crypto/cipher" |
| 6 | + "encoding/binary" |
| 7 | + "fmt" |
| 8 | + |
| 9 | + "golang.org/x/crypto/chacha20poly1305" |
| 10 | +) |
| 11 | + |
| 12 | +// NewEncrypter creates a new Encrypter based on the given encryption mode and secret key. |
| 13 | +// If the encryption mode is not supported, an error is returned. |
| 14 | +func NewEncrypter(encryptionMode EncryptionMode, secretKey []byte) (Encrypter, error) { |
| 15 | + switch encryptionMode { |
| 16 | + case EncryptionModeNone: |
| 17 | + return NewNoopEncrypter(), nil |
| 18 | + case EncryptionModeAEADAES256GCMRTPSize, EncryptionModeAEADXChaCha20Poly1305RTPSize: |
| 19 | + return NewAEADEncrypter(encryptionMode, secretKey) |
| 20 | + |
| 21 | + default: |
| 22 | + return nil, fmt.Errorf("unknown encryption mode: %s", encryptionMode) |
| 23 | + } |
| 24 | +} |
| 25 | + |
| 26 | +// Encrypter is used to encrypt RTP packets before sending them to Discord. |
| 27 | +// |
| 28 | +// The header is the 12 byte RTP header. |
| 29 | +// The data is the opus encoded audio data. |
| 30 | +// |
| 31 | +// The returned byte slice is the encrypted packet ready to be sent to Discord. |
| 32 | +// |
| 33 | +// [NoopEncrypter] does not encrypt the data and is used for testing purposes only. |
| 34 | +// [AEADEncrypter] is the required aead_xchacha20_poly1305_rtpsize encryption mode by Discord. |
| 35 | +// [AEADAES256GCMRTPSize] is the preferred aead_aes256_gcm_rtpsize encryption mode by Discord. |
| 36 | +// See https://discord.com/developers/docs/topics/voice-connections#transport-encryption-and-sending-voice for more information. |
| 37 | +type Encrypter interface { |
| 38 | + // Encrypt encrypts the given RTP header and opus data and returns the encrypted packet. |
| 39 | + Encrypt(header [RTPHeaderSize]byte, data []byte) []byte |
| 40 | + |
| 41 | + // Decrypt decrypts the given packet and returns the RTP header and opus data. |
| 42 | + Decrypt(rtpHeaderSize int, packet []byte) ([]byte, error) |
| 43 | +} |
| 44 | + |
| 45 | +// NewNoopEncrypter creates a new NoopEncrypter. |
| 46 | +func NewNoopEncrypter() *NoopEncrypter { |
| 47 | + return &NoopEncrypter{ |
| 48 | + buf: make([]byte, RTPHeaderSize, MaxOpusFrameSize+RTPHeaderSize), |
| 49 | + recBuf: make([]byte, 0, MaxOpusFrameSize+RTPHeaderSize), |
| 50 | + } |
| 51 | +} |
| 52 | + |
| 53 | +// NoopEncrypter is used to not encrypt RTP packets. This is only for testing purposes. |
| 54 | +// Do not use this in production as Discord requires encryption. |
| 55 | +type NoopEncrypter struct { |
| 56 | + buf []byte |
| 57 | + recBuf []byte |
| 58 | +} |
| 59 | + |
| 60 | +func (n *NoopEncrypter) Encrypt(header [RTPHeaderSize]byte, data []byte) []byte { |
| 61 | + n.buf = n.buf[:RTPHeaderSize] |
| 62 | + |
| 63 | + copy(n.buf, header[:]) |
| 64 | + n.buf = append(n.buf, data...) |
| 65 | + |
| 66 | + return n.buf |
| 67 | +} |
| 68 | + |
| 69 | +func (n *NoopEncrypter) Decrypt(rtpHeaderSize int, packet []byte) ([]byte, error) { |
| 70 | + n.recBuf = n.recBuf[:0] |
| 71 | + copy(n.recBuf, packet) |
| 72 | + |
| 73 | + return n.recBuf[rtpHeaderSize:], nil |
| 74 | +} |
| 75 | + |
| 76 | +// NewAEADEncrypter creates a new AEADEncrypter with the given encryption mode and secret key. |
| 77 | +func NewAEADEncrypter(encryptionMode EncryptionMode, secretKey []byte) (*AEADEncrypter, error) { |
| 78 | + var aead cipher.AEAD |
| 79 | + |
| 80 | + switch encryptionMode { |
| 81 | + case EncryptionModeAEADAES256GCMRTPSize: |
| 82 | + block, err := aes.NewCipher(secretKey) |
| 83 | + if err != nil { |
| 84 | + return nil, fmt.Errorf("failed to create AES cipher: %w", err) |
| 85 | + } |
| 86 | + |
| 87 | + c, err := cipher.NewGCM(block) |
| 88 | + if err != nil { |
| 89 | + return nil, fmt.Errorf("failed to create GCM cipher: %w", err) |
| 90 | + } |
| 91 | + aead = c |
| 92 | + case EncryptionModeAEADXChaCha20Poly1305RTPSize: |
| 93 | + c, err := chacha20poly1305.NewX(secretKey) |
| 94 | + if err != nil { |
| 95 | + return nil, fmt.Errorf("failed to create XChaCha20-Poly1305 cipher: %w", err) |
| 96 | + } |
| 97 | + aead = c |
| 98 | + default: |
| 99 | + return nil, fmt.Errorf("unknown encryption mode: %s", encryptionMode) |
| 100 | + } |
| 101 | + |
| 102 | + maxFrameSize := MaxOpusFrameSize + RTPHeaderSize + aead.NonceSize() + aead.Overhead() |
| 103 | + |
| 104 | + return &AEADEncrypter{ |
| 105 | + cipher: aead, |
| 106 | + buf: make([]byte, RTPHeaderSize, maxFrameSize), |
| 107 | + nonce: make([]byte, aead.NonceSize()), |
| 108 | + seq: 0, |
| 109 | + recBuf: make([]byte, 0, maxFrameSize), |
| 110 | + recNonce: make([]byte, aead.NonceSize()), |
| 111 | + }, nil |
| 112 | +} |
| 113 | + |
| 114 | +// AEADEncrypter is used to encrypt RTP packets using AEAD ciphers. |
| 115 | +type AEADEncrypter struct { |
| 116 | + cipher cipher.AEAD |
| 117 | + buf []byte |
| 118 | + nonce []byte |
| 119 | + seq uint32 |
| 120 | + |
| 121 | + recBuf []byte |
| 122 | + recNonce []byte |
| 123 | +} |
| 124 | + |
| 125 | +func (a *AEADEncrypter) Encrypt(header [RTPHeaderSize]byte, data []byte) []byte { |
| 126 | + a.buf = a.buf[:RTPHeaderSize] |
| 127 | + |
| 128 | + binary.LittleEndian.PutUint32(a.nonce, a.seq) |
| 129 | + a.seq++ |
| 130 | + |
| 131 | + copy(a.buf, header[:]) |
| 132 | + a.buf = a.cipher.Seal(a.buf, a.nonce, data, header[:]) |
| 133 | + a.buf = append(a.buf, a.nonce[:4]...) |
| 134 | + |
| 135 | + return a.buf |
| 136 | +} |
| 137 | + |
| 138 | +func (a *AEADEncrypter) Decrypt(rtpHeaderSize int, packet []byte) ([]byte, error) { |
| 139 | + a.recBuf = a.recBuf[:0] |
| 140 | + |
| 141 | + copy(a.recNonce, packet[len(packet)-4:]) |
| 142 | + |
| 143 | + var err error |
| 144 | + a.recBuf, err = a.cipher.Open(a.recBuf, a.recNonce, packet[rtpHeaderSize:len(packet)-4], packet[:rtpHeaderSize]) |
| 145 | + if err != nil { |
| 146 | + return nil, err |
| 147 | + } |
| 148 | + |
| 149 | + return a.recBuf, nil |
| 150 | +} |
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