47 lines
1.6 KiB
Go
47 lines
1.6 KiB
Go
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package srtp
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import "github.com/pion/rtp"
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// cipher represents a implementation of one
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// of the SRTP Specific ciphers
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type srtpCipher interface {
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// authTagLen returns auth key length of the cipher.
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// See the note below.
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authTagLen() int
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// aeadAuthTagLen returns AEAD auth key length of the cipher.
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// See the note below.
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aeadAuthTagLen() int
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getRTCPIndex([]byte) uint32
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encryptRTP([]byte, *rtp.Header, []byte, uint32) ([]byte, error)
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encryptRTCP([]byte, []byte, uint32, uint32) ([]byte, error)
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decryptRTP([]byte, []byte, *rtp.Header, int, uint32) ([]byte, error)
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decryptRTCP([]byte, []byte, uint32, uint32) ([]byte, error)
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}
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/*
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NOTE: Auth tag and AEAD auth tag are placed at the different position in SRTCP
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In non-AEAD cipher, the authentication tag is placed *after* the ESRTCP word
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(Encrypted-flag and SRTCP index).
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> AES_128_CM_HMAC_SHA1_80
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> | RTCP Header | Encrypted payload |E| SRTCP Index | Auth tag |
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> ^ |----------|
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> | ^
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> | authTagLen=10
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> aeadAuthTagLen=0
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In AEAD cipher, the AEAD authentication tag is embedded in the ciphertext.
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It is *before* the ESRTCP word (Encrypted-flag and SRTCP index).
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> AEAD_AES_128_GCM
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> | RTCP Header | Encrypted payload | AEAD auth tag |E| SRTCP Index |
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> |---------------| ^
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> ^ authTagLen=0
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> aeadAuthTagLen=16
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See https://tools.ietf.org/html/rfc7714 for the full specifications.
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*/
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