protocol: add AEAD encryption negotiation to v2 wire control channel (#5304)

README.md

@@ -13,6 +13,14 @@ frp is an open source project with its ongoing development made possible entirel
 
 <h3 align="center">Gold Sponsors</h3>
 <!--gold sponsors start-->
+<p align="center">
+  <a href="https://jb.gg/frp" target="_blank">
+    <img width="420px" src="https://raw.githubusercontent.com/fatedier/frp/dev/doc/pic/sponsor_jetbrains.jpg">
+	<br>
+	<b>The complete IDE crafted for professional Go developers</b>
+  </a>
+</p>
+
 <p align="center">
   <a href="https://github.com/beclab/Olares" target="_blank">
     <img width="420px" src="https://raw.githubusercontent.com/fatedier/frp/dev/doc/pic/sponsor_olares.jpeg">
@@ -32,24 +40,6 @@ If you're looking for a meeting recording API, consider checking out [Recall.ai]
 an API that records Zoom, Google Meet, Microsoft Teams, in-person meetings, and more.
 
 </div>
-
-<p align="center">
-  <a href="https://requestly.com/?utm_source=github&utm_medium=partnered&utm_campaign=frp" target="_blank">
-    <img width="480px" src="https://github.com/user-attachments/assets/24670320-997d-4d62-9bca-955c59fe883d">
-    <br>
-    <b>Requestly - Free & Open-Source alternative to Postman</b>
-    <br>
-    <sub>All-in-one platform to Test, Mock and Intercept APIs.</sub>
-  </a>
-</p>
-
-<p align="center">
-  <a href="https://jb.gg/frp" target="_blank">
-    <img width="420px" src="https://raw.githubusercontent.com/fatedier/frp/dev/doc/pic/sponsor_jetbrains.jpg">
-	<br>
-	<b>The complete IDE crafted for professional Go developers</b>
-  </a>
-</p>
 <!--gold sponsors end-->
 
 ## What is frp?

README_zh.md

@@ -15,6 +15,14 @@ frp 是一个完全开源的项目，我们的开发工作完全依靠赞助者
 
 <h3 align="center">Gold Sponsors</h3>
 <!--gold sponsors start-->
+<p align="center">
+  <a href="https://jb.gg/frp" target="_blank">
+    <img width="420px" src="https://raw.githubusercontent.com/fatedier/frp/dev/doc/pic/sponsor_jetbrains.jpg">
+	<br>
+	<b>The complete IDE crafted for professional Go developers</b>
+  </a>
+</p>
+
 <p align="center">
   <a href="https://github.com/beclab/Olares" target="_blank">
     <img width="420px" src="https://raw.githubusercontent.com/fatedier/frp/dev/doc/pic/sponsor_olares.jpeg">
@@ -34,24 +42,6 @@ If you're looking for a meeting recording API, consider checking out [Recall.ai]
 an API that records Zoom, Google Meet, Microsoft Teams, in-person meetings, and more.
 
 </div>
-
-<p align="center">
-  <a href="https://requestly.com/?utm_source=github&utm_medium=partnered&utm_campaign=frp" target="_blank">
-    <img width="480px" src="https://github.com/user-attachments/assets/24670320-997d-4d62-9bca-955c59fe883d">
-    <br>
-    <b>Requestly - Free & Open-Source alternative to Postman</b>
-    <br>
-    <sub>All-in-one platform to Test, Mock and Intercept APIs.</sub>
-  </a>
-</p>
-
-<p align="center">
-  <a href="https://jb.gg/frp" target="_blank">
-    <img width="420px" src="https://raw.githubusercontent.com/fatedier/frp/dev/doc/pic/sponsor_jetbrains.jpg">
-	<br>
-	<b>The complete IDE crafted for professional Go developers</b>
-  </a>
-</p>
 <!--gold sponsors end-->
 
 ## 为什么使用 frp ？

Release.md

@@ -10,9 +10,12 @@ This release introduces wire protocol v2 as a transition path for future frpc/fr
 
 **The default value of `transport.wireProtocol` remains `v1` in this release.** Users can keep the default for now. To test v2 early, upgrade both frpc and frps to versions that support it, then set `transport.wireProtocol = "v2"` in frpc. A v2-enabled frpc cannot connect to an older frps.
 
+When `transport.wireProtocol = "v2"` is enabled, the control channel uses negotiated AEAD encryption after the login handshake. Both frpc and frps must be upgraded to this release to use v2.
+
 v1 will be deprecated when v2 becomes the default in a future release. It will continue to be supported until v0.78.0 is released, and may be removed in v0.78.0 or later.
 
 ## Features
 
 * Added `transport.wireProtocol` for frpc to select the internal message protocol used between frpc and frps. Supported values are `v1` and `v2`.
 * Added client protocol visibility in the frps dashboard and `/api/clients` API. Online clients now report their negotiated protocol as `v1` or `v2`.
+* Wire protocol v2 now negotiates AEAD control-channel encryption. Supported algorithms are `xchacha20-poly1305` and `aes-256-gcm`; frpc advertises its preferred order based on local AES-GCM hardware support, and frps selects the first supported algorithm from that list.

client/control_session.go

@@ -74,17 +74,18 @@ func (d *controlSessionDialer) Dial(previousRunID string) (*SessionContext, erro
 		return nil, err
 	}
 
-	loginRespMsg, err := d.exchangeLogin(conn, loginMsg)
+	loginResult, err := d.exchangeLogin(conn, loginMsg)
 	if err != nil {
 		return nil, err
 	}
+	loginRespMsg := loginResult.resp
 	if loginRespMsg.Error != "" {
 		return nil, errors.New(loginRespMsg.Error)
 	}
 
 	var controlRW io.ReadWriter = conn
 	if d.clientSpec == nil || d.clientSpec.Type != "ssh-tunnel" {
-		controlRW, err = netpkg.NewCryptoReadWriter(conn, d.auth.EncryptionKey())
+		controlRW, err = d.newControlReadWriter(conn, loginResult.crypto)
 		if err != nil {
 			return nil, fmt.Errorf("create control crypto read writer: %w", err)
 		}
@@ -125,9 +126,16 @@ func (d *controlSessionDialer) buildLoginMsg(previousRunID string) (*msg.Login,
 	return loginMsg, nil
 }
 
-func (d *controlSessionDialer) exchangeLogin(conn net.Conn, loginMsg *msg.Login) (*msg.LoginResp, error) {
+type loginExchangeResult struct {
+	resp   *msg.LoginResp
+	crypto *wire.CryptoContext
+}
+
+func (d *controlSessionDialer) exchangeLogin(conn net.Conn, loginMsg *msg.Login) (*loginExchangeResult, error) {
 	rw := msg.NewV1ReadWriter(conn)
 	var wireConn *wire.Conn
+	var clientHello wire.ClientHello
+	var clientHelloPayload []byte
 
 	if d.common.Transport.WireProtocol == wire.ProtocolV2 {
 		if err := wire.WriteMagic(conn); err != nil {
@@ -136,14 +144,23 @@ func (d *controlSessionDialer) exchangeLogin(conn net.Conn, loginMsg *msg.Login)
 
 		wireConn = wire.NewConn(conn)
 		rw = msg.NewV2ReadWriterWithConn(wireConn)
-		hello := wire.DefaultClientHello(wire.BootstrapInfo{
+		var err error
+		clientHello, err = wire.NewClientHello(wire.BootstrapInfo{
 			Transport: d.common.Transport.Protocol,
 			TLS:       lo.FromPtr(d.common.Transport.TLS.Enable) || d.common.Transport.Protocol == "wss" || d.common.Transport.Protocol == "quic",
 			TCPMux:    lo.FromPtr(d.common.Transport.TCPMux),
 		})
-		if err := wireConn.WriteJSONFrame(wire.FrameTypeClientHello, hello); err != nil {
+		if err != nil {
 			return nil, err
 		}
+		clientHelloFrame, err := wire.NewJSONFrame(wire.FrameTypeClientHello, clientHello)
+		if err != nil {
+			return nil, err
+		}
+		if err := wireConn.WriteFrame(clientHelloFrame); err != nil {
+			return nil, err
+		}
+		clientHelloPayload = clientHelloFrame.Payload
 	}
 	if err := rw.WriteMsg(loginMsg); err != nil {
 		return nil, err
@@ -154,19 +171,50 @@ func (d *controlSessionDialer) exchangeLogin(conn net.Conn, loginMsg *msg.Login)
 		_ = conn.SetReadDeadline(time.Time{})
 	}()
 
+	var cryptoContext *wire.CryptoContext
 	if wireConn != nil {
+		serverHelloFrame, err := wireConn.ReadFrame()
+		if err != nil {
+			return nil, err
+		}
+		if serverHelloFrame.Type != wire.FrameTypeServerHello {
+			return nil, fmt.Errorf("unexpected frame type %d, want %d", serverHelloFrame.Type, wire.FrameTypeServerHello)
+		}
 		var serverHello wire.ServerHello
-		if err := wireConn.ReadJSONFrame(wire.FrameTypeServerHello, &serverHello); err != nil {
+		if err := wireConn.UnmarshalFrame(serverHelloFrame, &serverHello); err != nil {
 			return nil, err
 		}
 		if serverHello.Error != "" {
 			return nil, errors.New(serverHello.Error)
 		}
+		cryptoContext, err = wire.NewClientCryptoContext(clientHelloPayload, serverHelloFrame.Payload)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	var loginRespMsg msg.LoginResp
 	if err := rw.ReadMsgInto(&loginRespMsg); err != nil {
 		return nil, err
 	}
-	return &loginRespMsg, nil
+	return &loginExchangeResult{
+		resp:   &loginRespMsg,
+		crypto: cryptoContext,
+	}, nil
+}
+
+func (d *controlSessionDialer) newControlReadWriter(conn net.Conn, cryptoContext *wire.CryptoContext) (io.ReadWriter, error) {
+	if d.common.Transport.WireProtocol == wire.ProtocolV2 {
+		if cryptoContext == nil {
+			return nil, errors.New("missing v2 crypto negotiation")
+		}
+		return netpkg.NewAEADCryptoReadWriter(
+			conn,
+			d.auth.EncryptionKey(),
+			netpkg.AEADCryptoRoleClient,
+			cryptoContext.Algorithm,
+			cryptoContext.TranscriptHash,
+		)
+	}
+	return netpkg.NewCryptoReadWriter(conn, d.auth.EncryptionKey())
 }

client/control_session_test.go

@@ -29,6 +29,7 @@ import (
 	v1 "github.com/fatedier/frp/pkg/config/v1"
 	"github.com/fatedier/frp/pkg/msg"
 	"github.com/fatedier/frp/pkg/proto/wire"
+	netpkg "github.com/fatedier/frp/pkg/util/net"
 )
 
 type testConnector struct {
@@ -140,8 +141,17 @@ func TestControlSessionDialerDialV2(t *testing.T) {
 		}
 
 		wireConn := wire.NewConn(serverRaw)
+		clientHelloFrame, err := wireConn.ReadFrame()
+		if err != nil {
+			serverErrCh <- err
+			return
+		}
+		if clientHelloFrame.Type != wire.FrameTypeClientHello {
+			serverErrCh <- fmt.Errorf("unexpected frame type %d, want %d", clientHelloFrame.Type, wire.FrameTypeClientHello)
+			return
+		}
 		var hello wire.ClientHello
-		if err := wireConn.ReadJSONFrame(wire.FrameTypeClientHello, &hello); err != nil {
+		if err := wireConn.UnmarshalFrame(clientHelloFrame, &hello); err != nil {
 			serverErrCh <- err
 			return
 		}
@@ -160,11 +170,52 @@ func TestControlSessionDialerDialV2(t *testing.T) {
 			serverErrCh <- fmt.Errorf("unexpected user: %s", loginMsg.User)
 			return
 		}
-		if err := wireConn.WriteJSONFrame(wire.FrameTypeServerHello, wire.DefaultServerHello()); err != nil {
+		serverHello, err := wire.NewServerHello(hello)
+		if err != nil {
 			serverErrCh <- err
 			return
 		}
-		serverErrCh <- rw.WriteMsg(&msg.LoginResp{RunID: "run-v2"})
+		serverHelloFrame, err := wire.NewJSONFrame(wire.FrameTypeServerHello, serverHello)
+		if err != nil {
+			serverErrCh <- err
+			return
+		}
+		cryptoContext := wire.NewCryptoContext(
+			serverHello.Selected.Crypto.Algorithm,
+			clientHelloFrame.Payload,
+			serverHelloFrame.Payload,
+		)
+		if err := wireConn.WriteFrame(serverHelloFrame); err != nil {
+			serverErrCh <- err
+			return
+		}
+		if err := rw.WriteMsg(&msg.LoginResp{RunID: "run-v2"}); err != nil {
+			serverErrCh <- err
+			return
+		}
+
+		controlRW, err := netpkg.NewAEADCryptoReadWriter(
+			serverRaw,
+			[]byte("token"),
+			netpkg.AEADCryptoRoleServer,
+			cryptoContext.Algorithm,
+			cryptoContext.TranscriptHash,
+		)
+		if err != nil {
+			serverErrCh <- err
+			return
+		}
+		controlMsgRW := msg.NewReadWriter(controlRW, wire.ProtocolV2)
+		var ping msg.Ping
+		if err := controlMsgRW.ReadMsgInto(&ping); err != nil {
+			serverErrCh <- err
+			return
+		}
+		if ping.PrivilegeKey != "v2-ping" || ping.Timestamp != 12345 {
+			serverErrCh <- fmt.Errorf("unexpected ping: %+v", ping)
+			return
+		}
+		serverErrCh <- nil
 	}()
 
 	dialer := newTestControlSessionDialer(t, wire.ProtocolV2, connector, nil)
@@ -177,6 +228,7 @@ func TestControlSessionDialerDialV2(t *testing.T) {
 	require.NotNil(t, sessionCtx.Conn)
 	require.NotNil(t, sessionCtx.Connector)
 	require.False(t, connector.closed.Load())
+	require.NoError(t, sessionCtx.Conn.WriteMsg(&msg.Ping{PrivilegeKey: "v2-ping", Timestamp: 12345}))
 	require.NoError(t, <-serverErrCh)
 }
 

doc/agents/release.md

@@ -33,7 +33,51 @@ git commit -m "bump version to vX.Y.Z"
 git push origin dev
 ```
 
-## 3. Merge dev → master
+## 3. Pre-release Validation
+
+Run the standard e2e suite locally:
+
+```bash
+make e2e
+```
+
+For releases that touch compatibility-sensitive areas such as login, control
+connections, work connections, visitors, transport, or wire protocol handling,
+also run the manual compatibility e2e suite:
+
+```bash
+make e2e-compatibility
+make e2e-compatibility-floor
+```
+
+`make e2e-compatibility` builds the current `frps` and `frpc`, resolves the
+recent stable release baselines from GitHub, downloads or reuses their binaries,
+and tests current binaries against those historical releases. The default number
+of recent baselines is controlled by `FRP_COMPAT_BASELINE_COUNT` in the
+`Makefile`.
+
+Downloaded release binaries are cached under:
+
+```text
+.cache/e2e-compat/<version>/<os>_<arch>/
+```
+
+For a release validation run that must be exactly reproducible, pass an explicit
+baseline matrix instead of using the floating recent-release list:
+
+```bash
+FRP_COMPAT_BASELINE_VERSIONS="0.X.0 0.Y.0" make e2e-compatibility
+```
+
+Use `make e2e-compatibility-smoke` for a quick single-baseline check while
+iterating locally. If GitHub release metadata requests are rate-limited, set
+`GITHUB_TOKEN` or use `FRP_COMPAT_BASELINE_VERSIONS`.
+
+The compatibility floor is a support-policy decision, not a value that should
+change every release. Update `FRP_COMPAT_FLOOR_VERSION` only when the declared
+compatibility window changes.
+
+## 4. Merge dev → master
 
 Create a PR from `dev` to `master`:
 
@@ -43,7 +87,7 @@ gh pr create --base master --head dev --title "bump version"
 
 Wait for CI to pass, then merge using **merge commit** (not squash).
 
-## 4. Tag the Release
+## 5. Tag the Release
 
 ```bash
 git checkout master
@@ -52,7 +96,7 @@ git tag -a vX.Y.Z -m "bump version"
 git push origin vX.Y.Z
 ```
 
-## 5. Trigger GoReleaser
+## 6. Trigger GoReleaser
 
 Manually trigger the `goreleaser` workflow in GitHub Actions:
 

go.mod

@@ -5,7 +5,7 @@ go 1.25.0
 require (
 	github.com/armon/go-socks5 v0.0.0-20160902184237-e75332964ef5
 	github.com/coreos/go-oidc/v3 v3.14.1
-	github.com/fatedier/golib v0.6.0
+	github.com/fatedier/golib v0.7.0
 	github.com/google/uuid v1.6.0
 	github.com/gorilla/mux v1.8.1
 	github.com/gorilla/websocket v1.5.0
@@ -30,6 +30,7 @@ require (
 	golang.org/x/net v0.52.0
 	golang.org/x/oauth2 v0.28.0
 	golang.org/x/sync v0.20.0
+	golang.org/x/sys v0.42.0
 	golang.org/x/time v0.10.0
 	golang.zx2c4.com/wireguard v0.0.0-20231211153847-12269c276173
 	gopkg.in/ini.v1 v1.67.0
@@ -68,7 +69,6 @@ require (
 	github.com/wlynxg/anet v0.0.5 // indirect
 	go.uber.org/automaxprocs v1.6.0 // indirect
 	golang.org/x/mod v0.33.0 // indirect
-	golang.org/x/sys v0.42.0 // indirect
 	golang.org/x/text v0.35.0 // indirect
 	golang.org/x/tools v0.42.0 // indirect
 	golang.zx2c4.com/wintun v0.0.0-20230126152724-0fa3db229ce2 // indirect

go.sum

@@ -20,8 +20,8 @@ github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSs
 github.com/envoyproxy/go-control-plane v0.9.0/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.4/go.mod h1:6rpuAdCZL397s3pYoYcLgu1mIlRU8Am5FuJP05cCM98=
 github.com/envoyproxy/protoc-gen-validate v0.1.0/go.mod h1:iSmxcyjqTsJpI2R4NaDN7+kN2VEUnK/pcBlmesArF7c=
-github.com/fatedier/golib v0.6.0 h1:/mgBZZbkbMhIEZoXf7nV8knpUDzas/b+2ruYKxx1lww=
+github.com/fatedier/golib v0.7.0 h1:tMDF9ObcwVt59VUHroJOzHQjVFPLymZVMpGm9WAVwhY=
-github.com/fatedier/golib v0.6.0/go.mod h1:ArUGvPg2cOw/py2RAuBt46nNZH2VQ5Z70p109MAZpJw=
+github.com/fatedier/golib v0.7.0/go.mod h1:ArUGvPg2cOw/py2RAuBt46nNZH2VQ5Z70p109MAZpJw=
 github.com/fatedier/yamux v0.0.0-20250825093530-d0154be01cd6 h1:u92UUy6FURPmNsMBUuongRWC0rBqN6gd01Dzu+D21NE=
 github.com/fatedier/yamux v0.0.0-20250825093530-d0154be01cd6/go.mod h1:c5/tk6G0dSpXGzJN7Wk1OEie8grdSJAmeawId9Zvd34=
 github.com/go-jose/go-jose/v4 v4.0.5 h1:M6T8+mKZl/+fNNuFHvGIzDz7BTLQPIounk/b9dw3AaE=

pkg/proto/wire/crypto.go

@@ -0,0 +1,197 @@
+// Copyright 2026 The frp Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package wire
+
+import (
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/binary"
+	"encoding/json"
+	"fmt"
+	"hash"
+	"runtime"
+
+	"golang.org/x/sys/cpu"
+)
+
+const (
+	AEADAlgorithmAES256GCM         = "aes-256-gcm"
+	AEADAlgorithmXChaCha20Poly1305 = "xchacha20-poly1305"
+
+	CryptoRandomSize = 32
+
+	cryptoTranscriptLabel = "frp wire v2 crypto transcript"
+)
+
+var supportedAEADAlgorithms = []string{
+	AEADAlgorithmAES256GCM,
+	AEADAlgorithmXChaCha20Poly1305,
+}
+
+type CryptoContext struct {
+	Algorithm      string
+	TranscriptHash []byte
+}
+
+func NewClientHello(bootstrap BootstrapInfo) (ClientHello, error) {
+	clientRandom, err := newCryptoRandom()
+	if err != nil {
+		return ClientHello{}, err
+	}
+	return clientHelloWithCryptoRandom(bootstrap, clientRandom), nil
+}
+
+func NewServerHello(clientHello ClientHello) (ServerHello, error) {
+	if err := ValidateClientHello(clientHello); err != nil {
+		return ServerHello{}, err
+	}
+	algorithm, ok := SelectAEADAlgorithm(clientHello.Capabilities.Crypto.Algorithms)
+	if !ok {
+		return ServerHello{}, fmt.Errorf("no supported crypto algorithm")
+	}
+	serverRandom, err := newCryptoRandom()
+	if err != nil {
+		return ServerHello{}, err
+	}
+	return ServerHello{
+		Selected: ServerSelection{
+			Message: MessageSelection{
+				Codec: MessageCodecJSON,
+			},
+			Crypto: CryptoSelection{
+				Algorithm:    algorithm,
+				ServerRandom: serverRandom,
+			},
+		},
+	}, nil
+}
+
+func ValidateCryptoCapabilities(c CryptoCapabilities) error {
+	if len(c.ClientRandom) != CryptoRandomSize {
+		return fmt.Errorf("invalid crypto client random length %d, want %d", len(c.ClientRandom), CryptoRandomSize)
+	}
+	if _, ok := SelectAEADAlgorithm(c.Algorithms); !ok {
+		return fmt.Errorf("no supported crypto algorithm")
+	}
+	return nil
+}
+
+func ValidateServerHelloForClient(clientHello ClientHello, serverHello ServerHello) error {
+	if serverHello.Selected.Message.Codec != MessageCodecJSON {
+		return fmt.Errorf("unsupported selected message codec: %s", serverHello.Selected.Message.Codec)
+	}
+	cryptoSelection := serverHello.Selected.Crypto
+	if !IsSupportedAEADAlgorithm(cryptoSelection.Algorithm) {
+		return fmt.Errorf("unknown selected crypto algorithm: %s", cryptoSelection.Algorithm)
+	}
+	if !Supports(clientHello.Capabilities.Crypto.Algorithms, cryptoSelection.Algorithm) {
+		return fmt.Errorf("selected crypto algorithm was not advertised by client: %s", cryptoSelection.Algorithm)
+	}
+	if len(cryptoSelection.ServerRandom) != CryptoRandomSize {
+		return fmt.Errorf("invalid crypto server random length %d, want %d", len(cryptoSelection.ServerRandom), CryptoRandomSize)
+	}
+	return nil
+}
+
+func NewCryptoContext(algorithm string, clientHelloPayload, serverHelloPayload []byte) *CryptoContext {
+	return &CryptoContext{
+		Algorithm:      algorithm,
+		TranscriptHash: HashCryptoTranscript(clientHelloPayload, serverHelloPayload),
+	}
+}
+
+func NewClientCryptoContext(clientHelloPayload, serverHelloPayload []byte) (*CryptoContext, error) {
+	var clientHello ClientHello
+	if err := json.Unmarshal(clientHelloPayload, &clientHello); err != nil {
+		return nil, fmt.Errorf("decode ClientHello transcript: %w", err)
+	}
+	var serverHello ServerHello
+	if err := json.Unmarshal(serverHelloPayload, &serverHello); err != nil {
+		return nil, fmt.Errorf("decode ServerHello transcript: %w", err)
+	}
+	if err := ValidateServerHelloForClient(clientHello, serverHello); err != nil {
+		return nil, err
+	}
+
+	return NewCryptoContext(serverHello.Selected.Crypto.Algorithm, clientHelloPayload, serverHelloPayload), nil
+}
+
+func HashCryptoTranscript(clientHelloPayload, serverHelloPayload []byte) []byte {
+	h := sha256.New()
+	_, _ = h.Write([]byte(cryptoTranscriptLabel))
+	writeCryptoTranscriptPart(h, "client hello", clientHelloPayload)
+	writeCryptoTranscriptPart(h, "server hello", serverHelloPayload)
+	return h.Sum(nil)
+}
+
+func writeCryptoTranscriptPart(h hash.Hash, label string, payload []byte) {
+	var length [8]byte
+	binary.BigEndian.PutUint64(length[:], uint64(len(payload)))
+	_, _ = h.Write([]byte{0})
+	_, _ = h.Write([]byte(label))
+	_, _ = h.Write([]byte{0})
+	_, _ = h.Write(length[:])
+	_, _ = h.Write(payload)
+}
+
+func PreferredAEADAlgorithms() []string {
+	if hasFastAESGCM() {
+		return []string{AEADAlgorithmAES256GCM, AEADAlgorithmXChaCha20Poly1305}
+	}
+	return []string{AEADAlgorithmXChaCha20Poly1305, AEADAlgorithmAES256GCM}
+}
+
+func SelectAEADAlgorithm(clientAlgorithms []string) (string, bool) {
+	for _, algorithm := range clientAlgorithms {
+		if IsSupportedAEADAlgorithm(algorithm) {
+			return algorithm, true
+		}
+	}
+	return "", false
+}
+
+func IsSupportedAEADAlgorithm(algorithm string) bool {
+	return Supports(supportedAEADAlgorithms, algorithm)
+}
+
+func newCryptoRandom() ([]byte, error) {
+	b := make([]byte, CryptoRandomSize)
+	if _, err := rand.Read(b); err != nil {
+		return nil, fmt.Errorf("generate crypto random: %w", err)
+	}
+	return b, nil
+}
+
+func hasFastAESGCM() bool {
+	switch runtime.GOARCH {
+	case "amd64":
+		return cpu.X86.HasAES &&
+			cpu.X86.HasPCLMULQDQ &&
+			cpu.X86.HasSSE41 &&
+			cpu.X86.HasSSSE3
+	case "arm64":
+		return cpu.ARM64.HasAES && cpu.ARM64.HasPMULL
+	case "s390x":
+		return cpu.S390X.HasAES &&
+			cpu.S390X.HasAESCTR &&
+			cpu.S390X.HasGHASH
+	case "ppc64", "ppc64le":
+		// Go's ppc64/ppc64le port targets POWER8+, which has AES instructions;
+		// x/sys/cpu does not expose a PPC64 AES feature flag.
+		return true
+	default:
+		return false
+	}
+}

pkg/proto/wire/wire.go

@@ -120,15 +120,23 @@ func (c *Conn) UnmarshalFrame(f *Frame, out any) error {
 	return json.Unmarshal(f.Payload, out)
 }
 
-func (c *Conn) WriteJSONFrame(frameType uint16, in any) error {
+func NewJSONFrame(frameType uint16, in any) (*Frame, error) {
 	payload, err := json.Marshal(in)
+	if err != nil {
+		return nil, err
+	}
+	return &Frame{
+		Type:    frameType,
+		Payload: payload,
+	}, nil
+}
+
+func (c *Conn) WriteJSONFrame(frameType uint16, in any) error {
+	f, err := NewJSONFrame(frameType, in)
 	if err != nil {
 		return err
 	}
-	return c.WriteFrame(&Frame{
+	return c.WriteFrame(f)
-		Type:    frameType,
-		Payload: payload,
-	})
 }
 
 func WriteMagic(w io.Writer) error {
@@ -170,12 +178,18 @@ type ClientHello struct {
 
 type ClientCapabilities struct {
 	Message MessageCapabilities `json:"message,omitempty"`
+	Crypto  CryptoCapabilities  `json:"crypto,omitempty"`
 }
 
 type MessageCapabilities struct {
 	Codecs []string `json:"codecs,omitempty"`
 }
 
+type CryptoCapabilities struct {
+	Algorithms   []string `json:"algorithms,omitempty"`
+	ClientRandom []byte   `json:"clientRandom,omitempty"`
+}
+
 type ServerHello struct {
 	Selected ServerSelection `json:"selected,omitempty"`
 	Error    string          `json:"error,omitempty"`
@@ -183,19 +197,29 @@ type ServerHello struct {
 
 type ServerSelection struct {
 	Message MessageSelection `json:"message,omitempty"`
+	Crypto  CryptoSelection  `json:"crypto,omitempty"`
 }
 
 type MessageSelection struct {
 	Codec string `json:"codec,omitempty"`
 }
 
-func DefaultClientHello(bootstrap BootstrapInfo) ClientHello {
+type CryptoSelection struct {
+	Algorithm    string `json:"algorithm,omitempty"`
+	ServerRandom []byte `json:"serverRandom,omitempty"`
+}
+
+func clientHelloWithCryptoRandom(bootstrap BootstrapInfo, clientRandom []byte) ClientHello {
 	return ClientHello{
 		Bootstrap: bootstrap,
 		Capabilities: ClientCapabilities{
 			Message: MessageCapabilities{
 				Codecs: []string{MessageCodecJSON},
 			},
+			Crypto: CryptoCapabilities{
+				Algorithms:   PreferredAEADAlgorithms(),
+				ClientRandom: clientRandom,
+			},
 		},
 	}
 }
@@ -218,5 +242,5 @@ func ValidateClientHello(h ClientHello) error {
 	if !Supports(h.Capabilities.Message.Codecs, MessageCodecJSON) {
 		return fmt.Errorf("unsupported message codec")
 	}
-	return nil
+	return ValidateCryptoCapabilities(h.Capabilities.Crypto)
 }

pkg/proto/wire/wire_test.go

@@ -28,7 +28,7 @@ func TestFrameRoundTrip(t *testing.T) {
 	var buf bytes.Buffer
 	conn := NewConn(&buf)
 
-	in := DefaultClientHello(BootstrapInfo{
+	in := mustClientHello(t, BootstrapInfo{
 		Transport: "tcp",
 		TLS:       true,
 		TCPMux:    true,
@@ -112,9 +112,122 @@ func TestCheckMagicV1PreservesReadBytes(t *testing.T) {
 }
 
 func TestValidateClientHello(t *testing.T) {
-	require.NoError(t, ValidateClientHello(DefaultClientHello(BootstrapInfo{})))
+	hello := mustClientHello(t, BootstrapInfo{})
+	require.NoError(t, ValidateClientHello(hello))
+	require.Len(t, hello.Capabilities.Crypto.ClientRandom, CryptoRandomSize)
+	require.ElementsMatch(t, []string{
+		AEADAlgorithmAES256GCM,
+		AEADAlgorithmXChaCha20Poly1305,
+	}, hello.Capabilities.Crypto.Algorithms)
 
-	hello := DefaultClientHello(BootstrapInfo{})
 	hello.Capabilities.Message.Codecs = []string{"unknown"}
 	require.ErrorContains(t, ValidateClientHello(hello), "unsupported message codec")
 }
+
+func TestValidateClientHelloRejectsInvalidCrypto(t *testing.T) {
+	hello := mustClientHello(t, BootstrapInfo{})
+	hello.Capabilities.Crypto.ClientRandom = hello.Capabilities.Crypto.ClientRandom[:CryptoRandomSize-1]
+	require.ErrorContains(t, ValidateClientHello(hello), "invalid crypto client random length")
+
+	hello = mustClientHello(t, BootstrapInfo{})
+	hello.Capabilities.Crypto.Algorithms = []string{"unknown"}
+	require.ErrorContains(t, ValidateClientHello(hello), "no supported crypto algorithm")
+}
+
+func TestPreferredAEADAlgorithms(t *testing.T) {
+	require.ElementsMatch(t, []string{
+		AEADAlgorithmAES256GCM,
+		AEADAlgorithmXChaCha20Poly1305,
+	}, PreferredAEADAlgorithms())
+}
+
+func TestNewServerHelloSelectsFirstSupportedAEADAlgorithm(t *testing.T) {
+	hello := mustClientHello(t, BootstrapInfo{})
+	hello.Capabilities.Crypto.Algorithms = []string{"future-aead", AEADAlgorithmXChaCha20Poly1305, AEADAlgorithmAES256GCM}
+
+	serverHello, err := NewServerHello(hello)
+	require.NoError(t, err)
+	require.Equal(t, MessageCodecJSON, serverHello.Selected.Message.Codec)
+	require.Equal(t, AEADAlgorithmXChaCha20Poly1305, serverHello.Selected.Crypto.Algorithm)
+	require.Len(t, serverHello.Selected.Crypto.ServerRandom, CryptoRandomSize)
+}
+
+func TestNewClientCryptoContextValidatesServerHello(t *testing.T) {
+	hello := mustClientHello(t, BootstrapInfo{})
+	serverHello, err := NewServerHello(hello)
+	require.NoError(t, err)
+	clientHelloPayload, serverHelloPayload := mustCryptoTranscriptPayloads(t, hello, serverHello)
+
+	ctx, err := NewClientCryptoContext(clientHelloPayload, serverHelloPayload)
+	require.NoError(t, err)
+	require.Equal(t, serverHello.Selected.Crypto.Algorithm, ctx.Algorithm)
+	require.Len(t, ctx.TranscriptHash, 32)
+
+	tampered := serverHello
+	tampered.Selected.Crypto.ServerRandom = append([]byte(nil), serverHello.Selected.Crypto.ServerRandom...)
+	tampered.Selected.Crypto.ServerRandom[0] ^= 0xff
+	_, tamperedServerHelloPayload := mustCryptoTranscriptPayloads(t, hello, tampered)
+	tamperedCtx, err := NewClientCryptoContext(clientHelloPayload, tamperedServerHelloPayload)
+	require.NoError(t, err)
+	require.NotEqual(t, ctx.TranscriptHash, tamperedCtx.TranscriptHash)
+}
+
+func TestNewCryptoContextBindsFullClientHelloPayload(t *testing.T) {
+	hello := mustClientHello(t, BootstrapInfo{
+		Transport: "tcp",
+		TLS:       true,
+		TCPMux:    true,
+	})
+	serverHello, err := NewServerHello(hello)
+	require.NoError(t, err)
+	clientHelloPayload, serverHelloPayload := mustCryptoTranscriptPayloads(t, hello, serverHello)
+
+	ctx := NewCryptoContext(serverHello.Selected.Crypto.Algorithm, clientHelloPayload, serverHelloPayload)
+
+	tamperedHello := hello
+	tamperedHello.Bootstrap.TLS = false
+	tamperedClientHelloPayload, _ := mustCryptoTranscriptPayloads(t, tamperedHello, serverHello)
+	tamperedCtx := NewCryptoContext(serverHello.Selected.Crypto.Algorithm, tamperedClientHelloPayload, serverHelloPayload)
+	require.NotEqual(t, ctx.TranscriptHash, tamperedCtx.TranscriptHash)
+}
+
+func TestNewClientCryptoContextRejectsUnknownServerSelection(t *testing.T) {
+	hello := mustClientHello(t, BootstrapInfo{})
+	serverHello, err := NewServerHello(hello)
+	require.NoError(t, err)
+
+	serverHello.Selected.Crypto.Algorithm = "unknown"
+	clientHelloPayload, serverHelloPayload := mustCryptoTranscriptPayloads(t, hello, serverHello)
+	_, err = NewClientCryptoContext(clientHelloPayload, serverHelloPayload)
+	require.ErrorContains(t, err, "unknown selected crypto algorithm")
+}
+
+func TestNewClientCryptoContextRejectsUnadvertisedServerSelection(t *testing.T) {
+	hello := mustClientHello(t, BootstrapInfo{})
+	hello.Capabilities.Crypto.Algorithms = []string{AEADAlgorithmAES256GCM}
+	serverHello, err := NewServerHello(hello)
+	require.NoError(t, err)
+
+	serverHello.Selected.Crypto.Algorithm = AEADAlgorithmXChaCha20Poly1305
+	clientHelloPayload, serverHelloPayload := mustCryptoTranscriptPayloads(t, hello, serverHello)
+	_, err = NewClientCryptoContext(clientHelloPayload, serverHelloPayload)
+	require.ErrorContains(t, err, "selected crypto algorithm was not advertised by client")
+}
+
+func mustClientHello(t *testing.T, bootstrap BootstrapInfo) ClientHello {
+	t.Helper()
+
+	hello, err := NewClientHello(bootstrap)
+	require.NoError(t, err)
+	return hello
+}
+
+func mustCryptoTranscriptPayloads(t *testing.T, hello ClientHello, serverHello ServerHello) ([]byte, []byte) {
+	t.Helper()
+
+	clientHelloFrame, err := NewJSONFrame(FrameTypeClientHello, hello)
+	require.NoError(t, err)
+	serverHelloFrame, err := NewJSONFrame(FrameTypeServerHello, serverHello)
+	require.NoError(t, err)
+	return clientHelloFrame.Payload, serverHelloFrame.Payload
+}

pkg/util/net/conn.go

@@ -16,14 +16,16 @@ package net
 
 import (
 	"context"
+	"crypto/sha256"
 	"errors"
 	"io"
 	"net"
 	"sync/atomic"
 	"time"
 
-	"github.com/fatedier/golib/crypto"
+	libcrypto "github.com/fatedier/golib/crypto"
 	quic "github.com/quic-go/quic-go"
+	"golang.org/x/crypto/hkdf"
 
 	"github.com/fatedier/frp/pkg/util/xlog"
 )
@@ -241,8 +243,8 @@ func (conn *wrapQuicStream) Close() error {
 }
 
 func NewCryptoReadWriter(rw io.ReadWriter, key []byte) (io.ReadWriter, error) {
-	encReader := crypto.NewReader(rw, key)
+	encReader := libcrypto.NewReader(rw, key)
-	encWriter, err := crypto.NewWriter(rw, key)
+	encWriter, err := libcrypto.NewWriter(rw, key)
 	if err != nil {
 		return nil, err
 	}
@@ -254,3 +256,90 @@ func NewCryptoReadWriter(rw io.ReadWriter, key []byte) (io.ReadWriter, error) {
 		Writer: encWriter,
 	}, nil
 }
+
+type AEADCryptoRole int
+
+const (
+	AEADCryptoRoleClient AEADCryptoRole = iota + 1
+	AEADCryptoRoleServer
+)
+
+const (
+	aeadControlHKDFInfoPrefix   = "frp wire v2 control aead"
+	aeadDirectionClientToServer = "client-to-server"
+	aeadDirectionServerToClient = "server-to-client"
+)
+
+// NewAEADCryptoReadWriter wraps rw with framed AEAD encryption for the v2
+// control channel. Frames and their order are authenticated, but end-of-stream
+// is not: a clean EOF at a frame boundary is returned as normal EOF by the
+// underlying AEAD stream. Protocols that need truncation detection for finite
+// objects must add their own authenticated final message.
+func NewAEADCryptoReadWriter(
+	rw io.ReadWriter,
+	key []byte,
+	role AEADCryptoRole,
+	algorithm string,
+	transcriptHash []byte,
+) (io.ReadWriter, error) {
+	clientToServerKey, serverToClientKey, err := deriveAEADControlKeys(key, algorithm, transcriptHash)
+	if err != nil {
+		return nil, err
+	}
+
+	var readKey, writeKey []byte
+	switch role {
+	case AEADCryptoRoleClient:
+		readKey = serverToClientKey
+		writeKey = clientToServerKey
+	case AEADCryptoRoleServer:
+		readKey = clientToServerKey
+		writeKey = serverToClientKey
+	default:
+		return nil, errors.New("invalid aead crypto role")
+	}
+
+	encReader, err := libcrypto.NewAEADStreamReader(rw, libcrypto.AEADStreamOptions{
+		Algorithm: libcrypto.AEADAlgorithm(algorithm),
+		Key:       readKey,
+	})
+	if err != nil {
+		return nil, err
+	}
+	encWriter, err := libcrypto.NewAEADStreamWriter(rw, libcrypto.AEADStreamOptions{
+		Algorithm: libcrypto.AEADAlgorithm(algorithm),
+		Key:       writeKey,
+	})
+	if err != nil {
+		return nil, err
+	}
+	return struct {
+		io.Reader
+		io.Writer
+	}{
+		Reader: encReader,
+		Writer: encWriter,
+	}, nil
+}
+
+func deriveAEADControlKeys(key []byte, algorithm string, transcriptHash []byte) (clientToServerKey, serverToClientKey []byte, err error) {
+	clientToServerKey, err = deriveAEADControlKey(key, algorithm, transcriptHash, aeadDirectionClientToServer)
+	if err != nil {
+		return nil, nil, err
+	}
+	serverToClientKey, err = deriveAEADControlKey(key, algorithm, transcriptHash, aeadDirectionServerToClient)
+	if err != nil {
+		return nil, nil, err
+	}
+	return clientToServerKey, serverToClientKey, nil
+}
+
+func deriveAEADControlKey(key []byte, algorithm string, transcriptHash []byte, direction string) ([]byte, error) {
+	info := []byte(aeadControlHKDFInfoPrefix + " " + algorithm + " " + direction)
+	reader := hkdf.New(sha256.New, key, transcriptHash, info)
+	out := make([]byte, libcrypto.AEADKeySize)
+	if _, err := io.ReadFull(reader, out); err != nil {
+		return nil, err
+	}
+	return out, nil
+}

pkg/util/net/conn_test.go

@@ -0,0 +1,118 @@
+// Copyright 2026 The frp Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package net
+
+import (
+	"bytes"
+	"io"
+	stdnet "net"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/fatedier/frp/pkg/proto/wire"
+)
+
+func TestNewAEADCryptoReadWriterRoundTrip(t *testing.T) {
+	clientConn, serverConn := stdnet.Pipe()
+	defer clientConn.Close()
+	defer serverConn.Close()
+
+	key := []byte("token")
+	transcriptHash := bytes.Repeat([]byte{0x11}, 32)
+	clientRW, err := NewAEADCryptoReadWriter(
+		clientConn,
+		key,
+		AEADCryptoRoleClient,
+		wire.AEADAlgorithmXChaCha20Poly1305,
+		transcriptHash,
+	)
+	require.NoError(t, err)
+	serverRW, err := NewAEADCryptoReadWriter(
+		serverConn,
+		key,
+		AEADCryptoRoleServer,
+		wire.AEADAlgorithmXChaCha20Poly1305,
+		transcriptHash,
+	)
+	require.NoError(t, err)
+
+	clientErrCh := make(chan error, 1)
+	go func() {
+		if _, err := clientRW.Write([]byte("ping")); err != nil {
+			clientErrCh <- err
+			return
+		}
+		buf := make([]byte, len("pong"))
+		_, err := io.ReadFull(clientRW, buf)
+		clientErrCh <- err
+	}()
+
+	buf := make([]byte, len("ping"))
+	_, err = io.ReadFull(serverRW, buf)
+	require.NoError(t, err)
+	require.Equal(t, "ping", string(buf))
+	_, err = serverRW.Write([]byte("pong"))
+	require.NoError(t, err)
+	require.NoError(t, <-clientErrCh)
+}
+
+func TestNewAEADCryptoReadWriterRejectsDifferentTranscript(t *testing.T) {
+	clientConn, serverConn := stdnet.Pipe()
+	defer clientConn.Close()
+	defer serverConn.Close()
+	require.NoError(t, clientConn.SetDeadline(time.Now().Add(time.Second)))
+	require.NoError(t, serverConn.SetDeadline(time.Now().Add(time.Second)))
+
+	key := []byte("token")
+	clientRW, err := NewAEADCryptoReadWriter(
+		clientConn,
+		key,
+		AEADCryptoRoleClient,
+		wire.AEADAlgorithmAES256GCM,
+		bytes.Repeat([]byte{0x22}, 32),
+	)
+	require.NoError(t, err)
+	serverRW, err := NewAEADCryptoReadWriter(
+		serverConn,
+		key,
+		AEADCryptoRoleServer,
+		wire.AEADAlgorithmAES256GCM,
+		bytes.Repeat([]byte{0x33}, 32),
+	)
+	require.NoError(t, err)
+
+	writeErrCh := make(chan error, 1)
+	go func() {
+		_, err := clientRW.Write([]byte("ping"))
+		writeErrCh <- err
+	}()
+
+	buf := make([]byte, len("ping"))
+	_, err = io.ReadFull(serverRW, buf)
+	require.Error(t, err)
+	require.NoError(t, <-writeErrCh)
+}
+
+func TestDeriveAEADControlKeysUsesDistinctDirections(t *testing.T) {
+	clientToServerKey, serverToClientKey, err := deriveAEADControlKeys(
+		[]byte("token"),
+		wire.AEADAlgorithmXChaCha20Poly1305,
+		bytes.Repeat([]byte{0x44}, 32),
+	)
+	require.NoError(t, err)
+	require.NotEqual(t, clientToServerKey, serverToClientKey)
+}

server/service.go

@@ -60,6 +60,7 @@ import (
 
 const (
 	connReadTimeout       time.Duration = 10 * time.Second
+	connWriteTimeout      time.Duration = 5 * time.Second
 	vhostReadWriteTimeout time.Duration = 30 * time.Second
 )
 
@@ -456,7 +457,7 @@ func (svr *Service) handleConnection(ctx context.Context, conn net.Conn, interna
 			controlConn := acceptedConn.conn
 			if !internal {
 				var controlRW io.ReadWriter
-				controlRW, err = netpkg.NewCryptoReadWriter(conn, svr.auth.EncryptionKey())
+				controlRW, err = acceptedConn.newControlReadWriter(conn, svr.auth.EncryptionKey())
 				if err == nil {
 					controlConn = acceptedConn.messageConnFor(controlRW)
 				}
@@ -468,17 +469,23 @@ func (svr *Service) handleConnection(ctx context.Context, conn net.Conn, interna
 
 		if err != nil {
 			xl.Warnf("register control error: %v", err)
-			_ = acceptedConn.conn.WriteMsg(&msg.LoginResp{
+			if writeErr := writeWithDeadline(conn, connWriteTimeout, func() error {
-				Version: version.Full(),
+				return acceptedConn.conn.WriteMsg(&msg.LoginResp{
-				Error:   util.GenerateResponseErrorString("register control error", err, lo.FromPtr(svr.cfg.DetailedErrorsToClient)),
+					Version: version.Full(),
-			})
+					Error:   util.GenerateResponseErrorString("register control error", err, lo.FromPtr(svr.cfg.DetailedErrorsToClient)),
+				})
+			}); writeErr != nil {
+				xl.Warnf("write login error response error: %v", writeErr)
+			}
 			conn.Close()
 			return
 		}
-		if err = acceptedConn.conn.WriteMsg(&msg.LoginResp{
+		if err = writeWithDeadline(conn, connWriteTimeout, func() error {
-			Version: version.Full(),
+			return acceptedConn.conn.WriteMsg(&msg.LoginResp{
-			RunID:   ctl.runID,
+				Version: version.Full(),
-			Error:   "",
+				RunID:   ctl.runID,
+				Error:   "",
+			})
 		}); err != nil {
 			xl.Warnf("write login response error: %v", err)
 			svr.ctlManager.Del(m.RunID, ctl)
@@ -521,9 +528,10 @@ func (svr *Service) handleConnection(ctx context.Context, conn net.Conn, interna
 }
 
 type acceptedConnection struct {
-	conn         *msg.Conn
+	conn          *msg.Conn
-	wireProtocol string
+	wireProtocol  string
-	firstMsg     msg.Message
+	cryptoContext *wire.CryptoContext
+	firstMsg      msg.Message
 }
 
 func (svr *Service) acceptConnection(ctx context.Context, conn net.Conn) (*acceptedConnection, error) {
@@ -544,7 +552,7 @@ func (svr *Service) acceptConnection(ctx context.Context, conn net.Conn) (*accep
 		wireConn := wire.NewConn(conn)
 		rw := msg.NewV2ReadWriterWithConn(wireConn)
 		acceptedConn.conn = msg.NewConn(conn, rw)
-		acceptedConn.firstMsg, err = acceptedConn.readFirstV2Msg(wireConn)
+		acceptedConn.firstMsg, err = acceptedConn.readFirstV2Msg(conn, wireConn)
 	} else {
 		rw := msg.NewV1ReadWriter(conn)
 		acceptedConn.conn = msg.NewConn(conn, rw)
@@ -557,17 +565,41 @@ func (svr *Service) acceptConnection(ctx context.Context, conn net.Conn) (*accep
 	return acceptedConn, nil
 }
 
+func writeWithDeadline(conn net.Conn, timeout time.Duration, writeFn func() error) error {
+	_ = conn.SetWriteDeadline(time.Now().Add(timeout))
+	defer func() {
+		_ = conn.SetWriteDeadline(time.Time{})
+	}()
+	return writeFn()
+}
+
 func (ac *acceptedConnection) messageConnFor(rw io.ReadWriter) *msg.Conn {
 	return msg.NewConn(ac.conn, msg.NewReadWriter(rw, ac.wireProtocol))
 }
 
-func (ac *acceptedConnection) readFirstV2Msg(wireConn *wire.Conn) (msg.Message, error) {
+func (ac *acceptedConnection) newControlReadWriter(rw io.ReadWriter, key []byte) (io.ReadWriter, error) {
+	if ac.wireProtocol == wire.ProtocolV2 {
+		if ac.cryptoContext == nil {
+			return nil, fmt.Errorf("missing v2 crypto negotiation")
+		}
+		return netpkg.NewAEADCryptoReadWriter(
+			rw,
+			key,
+			netpkg.AEADCryptoRoleServer,
+			ac.cryptoContext.Algorithm,
+			ac.cryptoContext.TranscriptHash,
+		)
+	}
+	return netpkg.NewCryptoReadWriter(rw, key)
+}
+
+func (ac *acceptedConnection) readFirstV2Msg(conn net.Conn, wireConn *wire.Conn) (msg.Message, error) {
 	frame, err := wireConn.ReadFrame()
 	if err != nil {
 		return nil, fmt.Errorf("read v2 frame: %w", err)
 	}
 	if frame.Type == wire.FrameTypeClientHello {
-		if err := ac.handleClientHello(wireConn, frame); err != nil {
+		if err := ac.handleClientHello(conn, wireConn, frame); err != nil {
 			return nil, err
 		}
 		frame, err = wireConn.ReadFrame()
@@ -583,21 +615,38 @@ func (ac *acceptedConnection) readFirstV2Msg(wireConn *wire.Conn) (msg.Message,
 	return m, nil
 }
 
-func (ac *acceptedConnection) handleClientHello(wireConn *wire.Conn, frame *wire.Frame) error {
+func (ac *acceptedConnection) handleClientHello(conn net.Conn, wireConn *wire.Conn, frame *wire.Frame) error {
 	var hello wire.ClientHello
 	if err := wireConn.UnmarshalFrame(frame, &hello); err != nil {
 		return fmt.Errorf("decode ClientHello: %w", err)
 	}
 
-	serverHello := wire.DefaultServerHello()
+	serverHello, err := wire.NewServerHello(hello)
-	if err := wire.ValidateClientHello(hello); err != nil {
+	if err != nil {
+		serverHello = wire.DefaultServerHello()
 		serverHello.Error = err.Error()
-		_ = wireConn.WriteJSONFrame(wire.FrameTypeServerHello, serverHello)
+		if writeErr := writeWithDeadline(conn, connWriteTimeout, func() error {
+			return wireConn.WriteJSONFrame(wire.FrameTypeServerHello, serverHello)
+		}); writeErr != nil {
+			return fmt.Errorf("%w; write ServerHello error: %v", err, writeErr)
+		}
 		return err
 	}
-	if err := wireConn.WriteJSONFrame(wire.FrameTypeServerHello, serverHello); err != nil {
+	serverHelloFrame, err := wire.NewJSONFrame(wire.FrameTypeServerHello, serverHello)
+	if err != nil {
+		return fmt.Errorf("encode ServerHello: %w", err)
+	}
+	cryptoContext := wire.NewCryptoContext(
+		serverHello.Selected.Crypto.Algorithm,
+		frame.Payload,
+		serverHelloFrame.Payload,
+	)
+	if err := writeWithDeadline(conn, connWriteTimeout, func() error {
+		return wireConn.WriteFrame(serverHelloFrame)
+	}); err != nil {
 		return fmt.Errorf("write ServerHello: %w", err)
 	}
+	ac.cryptoContext = cryptoContext
 	return nil
 }
 

server/service_test.go

@@ -0,0 +1,63 @@
+// Copyright 2026 The frp Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package server
+
+import (
+	"errors"
+	"net"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestWriteWithDeadlineTimesOutAndClearsDeadline(t *testing.T) {
+	serverConn, clientConn := net.Pipe()
+	defer serverConn.Close()
+	defer clientConn.Close()
+
+	err := writeWithDeadline(serverConn, 50*time.Millisecond, func() error {
+		_, writeErr := serverConn.Write([]byte("x"))
+		return writeErr
+	})
+	require.Error(t, err)
+
+	var netErr net.Error
+	require.True(t, errors.As(err, &netErr))
+	require.True(t, netErr.Timeout())
+
+	readCh := make(chan byte, 1)
+	errCh := make(chan error, 1)
+	go func() {
+		buf := make([]byte, 1)
+		if _, readErr := clientConn.Read(buf); readErr != nil {
+			errCh <- readErr
+			return
+		}
+		readCh <- buf[0]
+	}()
+
+	_, err = serverConn.Write([]byte("y"))
+	require.NoError(t, err)
+
+	select {
+	case b := <-readCh:
+		require.Equal(t, byte('y'), b)
+	case err := <-errCh:
+		require.NoError(t, err)
+	case <-time.After(time.Second):
+		t.Fatal("timed out waiting for write after deadline reset")
+	}
+}