78 lines
1.8 KiB
Go
78 lines
1.8 KiB
Go
package srtp
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import (
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"encoding/binary"
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"fmt"
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"github.com/pion/rtcp"
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)
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const maxSRTCPIndex = 0x7FFFFFFF
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func (c *Context) decryptRTCP(dst, encrypted []byte) ([]byte, error) {
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out := allocateIfMismatch(dst, encrypted)
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tailOffset := len(encrypted) - (c.cipher.authTagLen() + srtcpIndexSize)
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if tailOffset < 0 {
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return nil, fmt.Errorf("%w: %d", errTooShortRTCP, len(encrypted))
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} else if isEncrypted := encrypted[tailOffset] >> 7; isEncrypted == 0 {
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return out, nil
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}
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index := c.cipher.getRTCPIndex(encrypted)
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ssrc := binary.BigEndian.Uint32(encrypted[4:])
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s := c.getSRTCPSSRCState(ssrc)
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markAsValid, ok := s.replayDetector.Check(uint64(index))
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if !ok {
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return nil, &errorDuplicated{Proto: "srtcp", SSRC: ssrc, Index: index}
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}
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out, err := c.cipher.decryptRTCP(out, encrypted, index, ssrc)
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if err != nil {
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return nil, err
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}
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markAsValid()
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return out, nil
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}
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// DecryptRTCP decrypts a buffer that contains a RTCP packet
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func (c *Context) DecryptRTCP(dst, encrypted []byte, header *rtcp.Header) ([]byte, error) {
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if header == nil {
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header = &rtcp.Header{}
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}
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if err := header.Unmarshal(encrypted); err != nil {
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return nil, err
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}
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return c.decryptRTCP(dst, encrypted)
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}
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func (c *Context) encryptRTCP(dst, decrypted []byte) ([]byte, error) {
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ssrc := binary.BigEndian.Uint32(decrypted[4:])
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s := c.getSRTCPSSRCState(ssrc)
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// We roll over early because MSB is used for marking as encrypted
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s.srtcpIndex++
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if s.srtcpIndex > maxSRTCPIndex {
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s.srtcpIndex = 0
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}
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return c.cipher.encryptRTCP(dst, decrypted, s.srtcpIndex, ssrc)
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}
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// EncryptRTCP Encrypts a RTCP packet
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func (c *Context) EncryptRTCP(dst, decrypted []byte, header *rtcp.Header) ([]byte, error) {
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if header == nil {
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header = &rtcp.Header{}
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}
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if err := header.Unmarshal(decrypted); err != nil {
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return nil, err
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}
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return c.encryptRTCP(dst, decrypted)
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}
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