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90 lines
2.3 KiB
Go
90 lines
2.3 KiB
Go
package ratchet
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import (
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"go.mau.fi/libsignal/kdf"
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"go.mau.fi/libsignal/util/bytehelper"
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)
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// KdfInfo is optional bytes to include in deriving secrets with KDF.
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const KdfInfo string = "WhisperGroup"
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// NewSenderMessageKey will return a new sender message key using the given
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// iteration and seed.
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func NewSenderMessageKey(iteration uint32, seed []byte) (*SenderMessageKey, error) {
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derivative, err := kdf.DeriveSecrets(seed, nil, []byte(KdfInfo), 48)
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if err != nil {
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return nil, err
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}
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// Split our derived secrets into 2 parts
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parts := bytehelper.Split(derivative, 16, 32)
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// Build the message key.
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senderKeyMessage := &SenderMessageKey{
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iteration: iteration,
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seed: seed,
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iv: parts[0],
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cipherKey: parts[1],
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}
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return senderKeyMessage, nil
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}
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// NewSenderMessageKeyFromStruct will return a new message key object from the
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// given serializeable structure.
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func NewSenderMessageKeyFromStruct(structure *SenderMessageKeyStructure) *SenderMessageKey {
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return &SenderMessageKey{
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iteration: structure.Iteration,
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iv: structure.IV,
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cipherKey: structure.CipherKey,
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seed: structure.Seed,
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}
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}
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// NewStructFromSenderMessageKey returns a serializeable structure of message keys.
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func NewStructFromSenderMessageKey(key *SenderMessageKey) *SenderMessageKeyStructure {
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return &SenderMessageKeyStructure{
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CipherKey: key.cipherKey,
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Iteration: key.iteration,
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IV: key.iv,
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Seed: key.seed,
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}
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}
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// SenderMessageKeyStructure is a serializeable structure of SenderMessageKeys.
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type SenderMessageKeyStructure struct {
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Iteration uint32
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IV []byte
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CipherKey []byte
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Seed []byte
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}
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// SenderMessageKey is a structure for sender message keys used in group
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// messaging.
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type SenderMessageKey struct {
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iteration uint32
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iv []byte
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cipherKey []byte
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seed []byte
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}
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// Iteration will return the sender message key's iteration.
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func (k *SenderMessageKey) Iteration() uint32 {
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return k.iteration
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}
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// Iv will return the sender message key's initialization vector.
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func (k *SenderMessageKey) Iv() []byte {
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return k.iv
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}
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// CipherKey will return the key in bytes.
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func (k *SenderMessageKey) CipherKey() []byte {
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return k.cipherKey
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}
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// Seed will return the sender message key's seed.
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func (k *SenderMessageKey) Seed() []byte {
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return k.seed
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}
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