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|
package dtls
import (
"context"
"crypto/rand"
"github.com/pion/dtls/v2/pkg/crypto/elliptic"
"github.com/pion/dtls/v2/pkg/protocol"
"github.com/pion/dtls/v2/pkg/protocol/alert"
"github.com/pion/dtls/v2/pkg/protocol/extension"
"github.com/pion/dtls/v2/pkg/protocol/handshake"
)
func flight0Parse(ctx context.Context, c flightConn, state *State, cache *handshakeCache, cfg *handshakeConfig) (flightVal, *alert.Alert, error) {
seq, msgs, ok := cache.fullPullMap(0,
handshakeCachePullRule{handshake.TypeClientHello, cfg.initialEpoch, true, false},
)
if !ok {
// No valid message received. Keep reading
return 0, nil, nil
}
state.handshakeRecvSequence = seq
var clientHello *handshake.MessageClientHello
// Validate type
if clientHello, ok = msgs[handshake.TypeClientHello].(*handshake.MessageClientHello); !ok {
return 0, &alert.Alert{Level: alert.Fatal, Description: alert.InternalError}, nil
}
if !clientHello.Version.Equal(protocol.Version1_2) {
return 0, &alert.Alert{Level: alert.Fatal, Description: alert.ProtocolVersion}, errUnsupportedProtocolVersion
}
state.remoteRandom = clientHello.Random
cipherSuites := []CipherSuite{}
for _, id := range clientHello.CipherSuiteIDs {
if c := cipherSuiteForID(CipherSuiteID(id), cfg.customCipherSuites); c != nil {
cipherSuites = append(cipherSuites, c)
}
}
if state.cipherSuite, ok = findMatchingCipherSuite(cipherSuites, cfg.localCipherSuites); !ok {
return 0, &alert.Alert{Level: alert.Fatal, Description: alert.InsufficientSecurity}, errCipherSuiteNoIntersection
}
for _, val := range clientHello.Extensions {
switch e := val.(type) {
case *extension.SupportedEllipticCurves:
if len(e.EllipticCurves) == 0 {
return 0, &alert.Alert{Level: alert.Fatal, Description: alert.InsufficientSecurity}, errNoSupportedEllipticCurves
}
state.namedCurve = e.EllipticCurves[0]
case *extension.UseSRTP:
profile, ok := findMatchingSRTPProfile(e.ProtectionProfiles, cfg.localSRTPProtectionProfiles)
if !ok {
return 0, &alert.Alert{Level: alert.Fatal, Description: alert.InsufficientSecurity}, errServerNoMatchingSRTPProfile
}
state.srtpProtectionProfile = profile
case *extension.UseExtendedMasterSecret:
if cfg.extendedMasterSecret != DisableExtendedMasterSecret {
state.extendedMasterSecret = true
}
case *extension.ServerName:
state.serverName = e.ServerName // remote server name
}
}
if cfg.extendedMasterSecret == RequireExtendedMasterSecret && !state.extendedMasterSecret {
return 0, &alert.Alert{Level: alert.Fatal, Description: alert.InsufficientSecurity}, errServerRequiredButNoClientEMS
}
if state.localKeypair == nil {
var err error
state.localKeypair, err = elliptic.GenerateKeypair(state.namedCurve)
if err != nil {
return 0, &alert.Alert{Level: alert.Fatal, Description: alert.IllegalParameter}, err
}
}
return flight2, nil, nil
}
func flight0Generate(c flightConn, state *State, cache *handshakeCache, cfg *handshakeConfig) ([]*packet, *alert.Alert, error) {
// Initialize
state.cookie = make([]byte, cookieLength)
if _, err := rand.Read(state.cookie); err != nil {
return nil, nil, err
}
var zeroEpoch uint16
state.localEpoch.Store(zeroEpoch)
state.remoteEpoch.Store(zeroEpoch)
state.namedCurve = defaultNamedCurve
if err := state.localRandom.Populate(); err != nil {
return nil, nil, err
}
return nil, nil, nil
}
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