Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

fix(agent/agentssh): use deterministic host key for SSH server#16626

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to ourterms of service andprivacy statement. We’ll occasionally send you account related emails.

Already on GitHub?Sign in to your account

Merged
Show file tree
Hide file tree
Changes fromall commits
Commits
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
44 changes: 41 additions & 3 deletionsagent/agent.go
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -6,6 +6,7 @@ import (
"encoding/json"
"errors"
"fmt"
"hash/fnv"
"io"
"net/http"
"net/netip"
Expand DownExpand Up@@ -994,7 +995,6 @@ func (a *agent) createOrUpdateNetwork(manifestOK, networkOK *checkpoint) func(co
if err := manifestOK.wait(ctx); err != nil {
return xerrors.Errorf("no manifest: %w", err)
}
var err error
defer func() {
networkOK.complete(retErr)
}()
Expand All@@ -1003,9 +1003,20 @@ func (a *agent) createOrUpdateNetwork(manifestOK, networkOK *checkpoint) func(co
network := a.network
a.closeMutex.Unlock()
if network == nil {
keySeed, err := WorkspaceKeySeed(manifest.WorkspaceID, manifest.AgentName)
if err != nil {
return xerrors.Errorf("generate seed from workspace id: %w", err)
}
// use the graceful context here, because creating the tailnet is not itself tied to the
// agent API.
network, err = a.createTailnet(a.gracefulCtx, manifest.AgentID, manifest.DERPMap, manifest.DERPForceWebSockets, manifest.DisableDirectConnections)
network, err = a.createTailnet(
a.gracefulCtx,
manifest.AgentID,
manifest.DERPMap,
manifest.DERPForceWebSockets,
manifest.DisableDirectConnections,
keySeed,
)
if err != nil {
return xerrors.Errorf("create tailnet: %w", err)
}
Expand DownExpand Up@@ -1145,7 +1156,13 @@ func (a *agent) trackGoroutine(fn func()) error {
return nil
}

func (a *agent) createTailnet(ctx context.Context, agentID uuid.UUID, derpMap *tailcfg.DERPMap, derpForceWebSockets, disableDirectConnections bool) (_ *tailnet.Conn, err error) {
func (a *agent) createTailnet(
ctx context.Context,
agentID uuid.UUID,
derpMap *tailcfg.DERPMap,
derpForceWebSockets, disableDirectConnections bool,
keySeed int64,
) (_ *tailnet.Conn, err error) {
// Inject `CODER_AGENT_HEADER` into the DERP header.
var header http.Header
if client, ok := a.client.(*agentsdk.Client); ok {
Expand All@@ -1172,6 +1189,10 @@ func (a *agent) createTailnet(ctx context.Context, agentID uuid.UUID, derpMap *t
}
}()

if err := a.sshServer.UpdateHostSigner(keySeed); err != nil {
return nil, xerrors.Errorf("update host signer: %w", err)
}

sshListener, err := network.Listen("tcp", ":"+strconv.Itoa(workspacesdk.AgentSSHPort))
if err != nil {
return nil, xerrors.Errorf("listen on the ssh port: %w", err)
Expand DownExpand Up@@ -1849,3 +1870,20 @@ func PrometheusMetricsHandler(prometheusRegistry *prometheus.Registry, logger sl
}
})
}

// WorkspaceKeySeed converts a WorkspaceID UUID and agent name to an int64 hash.
// This uses the FNV-1a hash algorithm which provides decent distribution and collision
// resistance for string inputs.
func WorkspaceKeySeed(workspaceID uuid.UUID, agentName string) (int64, error) {
h := fnv.New64a()
_, err := h.Write(workspaceID[:])
if err != nil {
return 42, err
}
_, err = h.Write([]byte(agentName))
if err != nil {
return 42, err
}

return int64(h.Sum64()), nil
}
122 changes: 108 additions & 14 deletionsagent/agentssh/agentssh.go
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -3,11 +3,12 @@ package agentssh
import (
"bufio"
"context"
"crypto/rand"
"crypto/rsa"
"errors"
"fmt"
"io"
"math/big"
"math/rand"
"net"
"os"
"os/exec"
Expand DownExpand Up@@ -128,17 +129,6 @@ type Server struct {
}

func NewServer(ctx context.Context, logger slog.Logger, prometheusRegistry *prometheus.Registry, fs afero.Fs, execer agentexec.Execer, config *Config) (*Server, error) {
// Clients' should ignore the host key when connecting.
// The agent needs to authenticate with coderd to SSH,
// so SSH authentication doesn't improve security.
randomHostKey, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil {
return nil, err
}
randomSigner, err := gossh.NewSignerFromKey(randomHostKey)
if err != nil {
return nil, err
}
if config == nil {
config = &Config{}
}
Expand DownExpand Up@@ -205,8 +195,10 @@ func NewServer(ctx context.Context, logger slog.Logger, prometheusRegistry *prom
slog.F("local_addr", conn.LocalAddr()),
slog.Error(err))
},
Handler: s.sessionHandler,
HostSigners: []ssh.Signer{randomSigner},
Handler: s.sessionHandler,
// HostSigners are intentionally empty, as the host key will
// be set before we start listening.
HostSigners: []ssh.Signer{},
LocalPortForwardingCallback: func(ctx ssh.Context, destinationHost string, destinationPort uint32) bool {
// Allow local port forwarding all!
s.logger.Debug(ctx, "local port forward",
Expand DownExpand Up@@ -844,7 +836,13 @@ func (s *Server) CreateCommand(ctx context.Context, script string, env []string,
return cmd, nil
}

// Serve starts the server to handle incoming connections on the provided listener.
// It returns an error if no host keys are set or if there is an issue accepting connections.
func (s *Server) Serve(l net.Listener) (retErr error) {
if len(s.srv.HostSigners) == 0 {
return xerrors.New("no host keys set")
}

s.logger.Info(context.Background(), "started serving listener", slog.F("listen_addr", l.Addr()))
defer func() {
s.logger.Info(context.Background(), "stopped serving listener",
Expand DownExpand Up@@ -1099,3 +1097,99 @@ func userHomeDir() (string, error) {
}
return u.HomeDir, nil
}

// UpdateHostSigner updates the host signer with a new key generated from the provided seed.
// If an existing host key exists with the same algorithm, it is overwritten
func (s *Server) UpdateHostSigner(seed int64) error {
key, err := CoderSigner(seed)
if err != nil {
return err
}

s.mu.Lock()
defer s.mu.Unlock()

s.srv.AddHostKey(key)

return nil
}

// CoderSigner generates a deterministic SSH signer based on the provided seed.
// It uses RSA with a key size of 2048 bits.
func CoderSigner(seed int64) (gossh.Signer, error) {
// Clients should ignore the host key when connecting.
// The agent needs to authenticate with coderd to SSH,
// so SSH authentication doesn't improve security.

// Since the standard lib purposefully does not generate
// deterministic rsa keys, we need to do it ourselves.
coderHostKey := func() *rsa.PrivateKey {
// Create deterministic random source
// nolint: gosec
deterministicRand := rand.New(rand.NewSource(seed))

// Use fixed values for p and q based on the seed
p := big.NewInt(0)
q := big.NewInt(0)
e := big.NewInt(65537) // Standard RSA public exponent

// Generate deterministic primes using the seeded random
// Each prime should be ~1024 bits to get a 2048-bit key
for {
p.SetBit(p, 1024, 1) // Ensure it's large enough
for i := 0; i < 1024; i++ {
if deterministicRand.Int63()%2 == 1 {
p.SetBit(p, i, 1)
} else {
p.SetBit(p, i, 0)
}
}
if p.ProbablyPrime(20) {
break
}
}

for {
q.SetBit(q, 1024, 1) // Ensure it's large enough
for i := 0; i < 1024; i++ {
if deterministicRand.Int63()%2 == 1 {
q.SetBit(q, i, 1)
} else {
q.SetBit(q, i, 0)
}
}
if q.ProbablyPrime(20) && p.Cmp(q) != 0 {
break
}
}

// Calculate n = p * q
n := new(big.Int).Mul(p, q)

// Calculate phi = (p-1) * (q-1)
p1 := new(big.Int).Sub(p, big.NewInt(1))
q1 := new(big.Int).Sub(q, big.NewInt(1))
phi := new(big.Int).Mul(p1, q1)

// Calculate private exponent d
d := new(big.Int).ModInverse(e, phi)

// Create the private key
privateKey := &rsa.PrivateKey{
PublicKey: rsa.PublicKey{
N: n,
E: int(e.Int64()),
},
D: d,
Primes: []*big.Int{p, q},
}

// Compute precomputed values
privateKey.Precompute()

return privateKey
}()

coderSigner, err := gossh.NewSignerFromKey(coderHostKey)
return coderSigner, err
}
2 changes: 2 additions & 0 deletionsagent/agentssh/agentssh_internal_test.go
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -39,6 +39,8 @@ func Test_sessionStart_orphan(t *testing.T) {
s, err := NewServer(ctx, logger, prometheus.NewRegistry(), afero.NewMemMapFs(), agentexec.DefaultExecer, nil)
require.NoError(t, err)
defer s.Close()
err = s.UpdateHostSigner(42)
assert.NoError(t, err)

// Here we're going to call the handler directly with a faked SSH session
// that just uses io.Pipes instead of a network socket. There is a large
Expand Down
8 changes: 8 additions & 0 deletionsagent/agentssh/agentssh_test.go
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -41,6 +41,8 @@ func TestNewServer_ServeClient(t *testing.T) {
s, err := agentssh.NewServer(ctx, logger, prometheus.NewRegistry(), afero.NewMemMapFs(), agentexec.DefaultExecer, nil)
require.NoError(t, err)
defer s.Close()
err = s.UpdateHostSigner(42)
assert.NoError(t, err)

ln, err := net.Listen("tcp", "127.0.0.1:0")
require.NoError(t, err)
Expand DownExpand Up@@ -146,6 +148,8 @@ func TestNewServer_CloseActiveConnections(t *testing.T) {
s, err := agentssh.NewServer(ctx, logger, prometheus.NewRegistry(), afero.NewMemMapFs(), agentexec.DefaultExecer, nil)
require.NoError(t, err)
defer s.Close()
err = s.UpdateHostSigner(42)
assert.NoError(t, err)

ln, err := net.Listen("tcp", "127.0.0.1:0")
require.NoError(t, err)
Expand DownExpand Up@@ -197,6 +201,8 @@ func TestNewServer_Signal(t *testing.T) {
s, err := agentssh.NewServer(ctx, logger, prometheus.NewRegistry(), afero.NewMemMapFs(), agentexec.DefaultExecer, nil)
require.NoError(t, err)
defer s.Close()
err = s.UpdateHostSigner(42)
assert.NoError(t, err)

ln, err := net.Listen("tcp", "127.0.0.1:0")
require.NoError(t, err)
Expand DownExpand Up@@ -262,6 +268,8 @@ func TestNewServer_Signal(t *testing.T) {
s, err := agentssh.NewServer(ctx, logger, prometheus.NewRegistry(), afero.NewMemMapFs(), agentexec.DefaultExecer, nil)
require.NoError(t, err)
defer s.Close()
err = s.UpdateHostSigner(42)
assert.NoError(t, err)

ln, err := net.Listen("tcp", "127.0.0.1:0")
require.NoError(t, err)
Expand Down
2 changes: 2 additions & 0 deletionsagent/agentssh/x11_test.go
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -38,6 +38,8 @@ func TestServer_X11(t *testing.T) {
s,err:=agentssh.NewServer(ctx,logger,prometheus.NewRegistry(),fs,agentexec.DefaultExecer,&agentssh.Config{})
require.NoError(t,err)
defers.Close()
err=s.UpdateHostSigner(42)
assert.NoError(t,err)

ln,err:=net.Listen("tcp","127.0.0.1:0")
require.NoError(t,err)
Expand Down
65 changes: 65 additions & 0 deletionscli/ssh_test.go
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -453,6 +453,71 @@ func TestSSH(t *testing.T) {
<-cmdDone
})

t.Run("DeterministicHostKey", func(t *testing.T) {
t.Parallel()
client, workspace, agentToken := setupWorkspaceForAgent(t)
_, _ = tGoContext(t, func(ctx context.Context) {
// Run this async so the SSH command has to wait for
// the build and agent to connect!
_ = agenttest.New(t, client.URL, agentToken)
<-ctx.Done()
})

clientOutput, clientInput := io.Pipe()
serverOutput, serverInput := io.Pipe()
defer func() {
for _, c := range []io.Closer{clientOutput, clientInput, serverOutput, serverInput} {
_ = c.Close()
}
}()

ctx, cancel := context.WithTimeout(context.Background(), testutil.WaitLong)
defer cancel()

inv, root := clitest.New(t, "ssh", "--stdio", workspace.Name)
clitest.SetupConfig(t, client, root)
inv.Stdin = clientOutput
inv.Stdout = serverInput
inv.Stderr = io.Discard

cmdDone := tGo(t, func() {
err := inv.WithContext(ctx).Run()
assert.NoError(t, err)
})

keySeed, err := agent.WorkspaceKeySeed(workspace.ID, "dev")
assert.NoError(t, err)

signer, err := agentssh.CoderSigner(keySeed)
assert.NoError(t, err)

conn, channels, requests, err := ssh.NewClientConn(&stdioConn{
Reader: serverOutput,
Writer: clientInput,
}, "", &ssh.ClientConfig{
HostKeyCallback: ssh.FixedHostKey(signer.PublicKey()),
})
require.NoError(t, err)
defer conn.Close()

sshClient := ssh.NewClient(conn, channels, requests)
session, err := sshClient.NewSession()
require.NoError(t, err)
defer session.Close()

command := "sh -c exit"
if runtime.GOOS == "windows" {
command = "cmd.exe /c exit"
}
err = session.Run(command)
require.NoError(t, err)
err = sshClient.Close()
require.NoError(t, err)
_ = clientOutput.Close()

<-cmdDone
})

t.Run("NetworkInfo", func(t *testing.T) {
t.Parallel()
client, workspace, agentToken := setupWorkspaceForAgent(t)
Expand Down
Loading
[8]ページ先頭
©2009-2025 Movatter.jp