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// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
// SPDX-License-Identifier: MIT
package ciphersuite
import (
"crypto/sha256"
"fmt"
"hash"
"sync/atomic"
"github.com/pion/dtls/v3/pkg/crypto/ciphersuite"
"github.com/pion/dtls/v3/pkg/crypto/clientcertificate"
"github.com/pion/dtls/v3/pkg/crypto/prf"
"github.com/pion/dtls/v3/pkg/protocol/recordlayer"
)
// AesCcm is a base class used by multiple AES-CCM Ciphers.
type AesCcm struct {
ccm atomic.Value // *cryptoCCM
clientCertificateType clientcertificate.Type
id ID
psk bool
keyExchangeAlgorithm KeyExchangeAlgorithm
cryptoCCMTagLen ciphersuite.CCMTagLen
ecc bool
}
// CertificateType returns what type of certificate this CipherSuite exchanges.
func (c *AesCcm) CertificateType() clientcertificate.Type {
return c.clientCertificateType
}
// ID returns the ID of the CipherSuite.
func (c *AesCcm) ID() ID {
return c.id
}
func (c *AesCcm) String() string {
return c.id.String()
}
// ECC uses Elliptic Curve Cryptography.
func (c *AesCcm) ECC() bool {
return c.ecc
}
// KeyExchangeAlgorithm controls what key exchange algorithm is using during the handshake.
func (c *AesCcm) KeyExchangeAlgorithm() KeyExchangeAlgorithm {
return c.keyExchangeAlgorithm
}
// HashFunc returns the hashing func for this CipherSuite.
func (c *AesCcm) HashFunc() func() hash.Hash {
return sha256.New
}
// AuthenticationType controls what authentication method is using during the handshake.
func (c *AesCcm) AuthenticationType() AuthenticationType {
if c.psk {
return AuthenticationTypePreSharedKey
}
return AuthenticationTypeCertificate
}
// IsInitialized returns if the CipherSuite has keying material and can
// encrypt/decrypt packets.
func (c *AesCcm) IsInitialized() bool {
return c.ccm.Load() != nil
}
// Init initializes the internal Cipher with keying material.
func (c *AesCcm) Init(masterSecret, clientRandom, serverRandom []byte, isClient bool, prfKeyLen int) error {
const (
prfMacLen = 0
prfIvLen = 4
)
keys, err := prf.GenerateEncryptionKeys(
masterSecret, clientRandom, serverRandom, prfMacLen, prfKeyLen, prfIvLen, c.HashFunc(),
)
if err != nil {
return err
}
var ccm *ciphersuite.CCM
if isClient {
ccm, err = ciphersuite.NewCCM(
c.cryptoCCMTagLen, keys.ClientWriteKey, keys.ClientWriteIV, keys.ServerWriteKey, keys.ServerWriteIV,
)
} else {
ccm, err = ciphersuite.NewCCM(
c.cryptoCCMTagLen, keys.ServerWriteKey, keys.ServerWriteIV, keys.ClientWriteKey, keys.ClientWriteIV,
)
}
c.ccm.Store(ccm)
return err
}
// Encrypt encrypts a single TLS RecordLayer.
func (c *AesCcm) Encrypt(pkt *recordlayer.RecordLayer, raw []byte) ([]byte, error) {
cipherSuite, ok := c.ccm.Load().(*ciphersuite.CCM)
if !ok {
return nil, fmt.Errorf("%w, unable to encrypt", errCipherSuiteNotInit)
}
return cipherSuite.Encrypt(pkt, raw)
}
// Decrypt decrypts a single TLS RecordLayer.
func (c *AesCcm) Decrypt(h recordlayer.Header, raw []byte) ([]byte, error) {
cipherSuite, ok := c.ccm.Load().(*ciphersuite.CCM)
if !ok {
return nil, fmt.Errorf("%w, unable to decrypt", errCipherSuiteNotInit)
}
return cipherSuite.Decrypt(h, raw)
}
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