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Merged
merged 3 commits into from
Feb 19, 2025
Merged

refactor(agent/agentssh): move parsing of magic session and create type #16630

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43e0cd9
refactor(agent/agentssh): move parsing of magic session and create type
mafredri Feb 19, 2025
9408720
move env variable def
mafredri Feb 19, 2025
0683ece
undo log change
mafredri Feb 19, 2025
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4 changes: 2 additions & 2 deletions agent/agent_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -138,7 +138,7 @@ func TestAgent_Stats_Magic(t *testing.T) {
defer sshClient.Close()
session, err := sshClient.NewSession()
require.NoError(t, err)
session.Setenv(agentssh.MagicSessionTypeEnvironmentVariable, agentssh.MagicSessionTypeVSCode)
session.Setenv(agentssh.MagicSessionTypeEnvironmentVariable, string(agentssh.MagicSessionTypeVSCode))
defer session.Close()

command := "sh -c 'echo $" + agentssh.MagicSessionTypeEnvironmentVariable + "'"
Expand All @@ -165,7 +165,7 @@ func TestAgent_Stats_Magic(t *testing.T) {
defer sshClient.Close()
session, err := sshClient.NewSession()
require.NoError(t, err)
session.Setenv(agentssh.MagicSessionTypeEnvironmentVariable, agentssh.MagicSessionTypeVSCode)
session.Setenv(agentssh.MagicSessionTypeEnvironmentVariable, string(agentssh.MagicSessionTypeVSCode))
defer session.Close()
stdin, err := session.StdinPipe()
require.NoError(t, err)
Expand Down
134 changes: 85 additions & 49 deletions agent/agentssh/agentssh.go
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ import (
"github.com/spf13/afero"
"go.uber.org/atomic"
gossh "golang.org/x/crypto/ssh"
"golang.org/x/exp/slices"
"golang.org/x/xerrors"

"cdr.dev/slog"
Expand All @@ -42,14 +43,6 @@ const (
// unlikely to shadow other exit codes, which are typically 1, 2, 3, etc.
MagicSessionErrorCode = 229

// MagicSessionTypeEnvironmentVariable is used to track the purpose behind an SSH connection.
// This is stripped from any commands being executed, and is counted towards connection stats.
MagicSessionTypeEnvironmentVariable = "CODER_SSH_SESSION_TYPE"
// MagicSessionTypeVSCode is set in the SSH config by the VS Code extension to identify itself.
MagicSessionTypeVSCode = "vscode"
// MagicSessionTypeJetBrains is set in the SSH config by the JetBrains
// extension to identify itself.
MagicSessionTypeJetBrains = "jetbrains"
// MagicProcessCmdlineJetBrains is a string in a process's command line that
// uniquely identifies it as JetBrains software.
MagicProcessCmdlineJetBrains = "idea.vendor.name=JetBrains"
Expand All @@ -60,6 +53,29 @@ const (
BlockedFileTransferErrorMessage = "File transfer has been disabled."
)

// MagicSessionType is a type that represents the type of session that is being
// established.
type MagicSessionType string

const (
// MagicSessionTypeEnvironmentVariable is used to track the purpose behind an SSH connection.
// This is stripped from any commands being executed, and is counted towards connection stats.
MagicSessionTypeEnvironmentVariable = "CODER_SSH_SESSION_TYPE"
)

// MagicSessionType enums.
const (
// MagicSessionTypeUnknown means the session type could not be determined.
MagicSessionTypeUnknown MagicSessionType = "unknown"
// MagicSessionTypeSSH is the default session type.
MagicSessionTypeSSH MagicSessionType = "ssh"
// MagicSessionTypeVSCode is set in the SSH config by the VS Code extension to identify itself.
MagicSessionTypeVSCode MagicSessionType = "vscode"
// MagicSessionTypeJetBrains is set in the SSH config by the JetBrains
// extension to identify itself.
MagicSessionTypeJetBrains MagicSessionType = "jetbrains"
)

// BlockedFileTransferCommands contains a list of restricted file transfer commands.
var BlockedFileTransferCommands = []string{"nc", "rsync", "scp", "sftp"}

Expand Down Expand Up @@ -255,14 +271,42 @@ func (s *Server) ConnStats() ConnStats {
}
}

func extractMagicSessionType(env []string) (magicType MagicSessionType, rawType string, filteredEnv []string) {
for _, kv := range env {
if !strings.HasPrefix(kv, MagicSessionTypeEnvironmentVariable) {
continue
}

rawType = strings.TrimPrefix(kv, MagicSessionTypeEnvironmentVariable+"=")
// Keep going, we'll use the last instance of the env.
}

// Always force lowercase checking to be case-insensitive.
switch MagicSessionType(strings.ToLower(rawType)) {
case MagicSessionTypeVSCode:
magicType = MagicSessionTypeVSCode
case MagicSessionTypeJetBrains:
magicType = MagicSessionTypeJetBrains
case "", MagicSessionTypeSSH:
magicType = MagicSessionTypeSSH
default:
magicType = MagicSessionTypeUnknown
}

return magicType, rawType, slices.DeleteFunc(env, func(kv string) bool {
return strings.HasPrefix(kv, MagicSessionTypeEnvironmentVariable+"=")
})
}

Comment on lines +274 to +300
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suggestion: extractMagicSessionType(env []string) (MagicSessionType, filteredEnv, error) and return error in case of unknown magic session type?

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I kind of like the suggestion, but I don't like returning valid data from a function that returns an error. Essentially we'd still want to filter the env in the case of an error parsing the magic session type. (We only warn log currently if it's invalid.)

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Fair!

func (s *Server) sessionHandler(session ssh.Session) {
ctx := session.Context()
id := uuid.New()
logger := s.logger.With(
slog.F("remote_addr", session.RemoteAddr()),
slog.F("local_addr", session.LocalAddr()),
// Assigning a random uuid for each session is useful for tracking
// logs for the same ssh session.
slog.F("id", uuid.NewString()),
slog.F("id", id.String()),
)
logger.Info(ctx, "handling ssh session")

Expand All @@ -274,16 +318,21 @@ func (s *Server) sessionHandler(session ssh.Session) {
}
defer s.trackSession(session, false)

extraEnv := make([]string, 0)
x11, hasX11 := session.X11()
if hasX11 {
display, handled := s.x11Handler(session.Context(), x11)
if !handled {
_ = session.Exit(1)
logger.Error(ctx, "x11 handler failed")
return
}
extraEnv = append(extraEnv, fmt.Sprintf("DISPLAY=localhost:%d.%d", display, x11.ScreenNumber))
env := session.Environ()
magicType, magicTypeRaw, env := extractMagicSessionType(env)

switch magicType {
case MagicSessionTypeVSCode:
s.connCountVSCode.Add(1)
defer s.connCountVSCode.Add(-1)
case MagicSessionTypeJetBrains:
// Do nothing here because JetBrains launches hundreds of ssh sessions.
// We instead track JetBrains in the single persistent tcp forwarding channel.
case MagicSessionTypeSSH:
s.connCountSSHSession.Add(1)
defer s.connCountSSHSession.Add(-1)
case MagicSessionTypeUnknown:
logger.Warn(ctx, "invalid magic ssh session type specified", slog.F("raw_type", magicTypeRaw))
}

if s.fileTransferBlocked(session) {
Expand All @@ -309,7 +358,18 @@ func (s *Server) sessionHandler(session ssh.Session) {
return
}

err := s.sessionStart(logger, session, extraEnv)
x11, hasX11 := session.X11()
if hasX11 {
display, handled := s.x11Handler(session.Context(), x11)
if !handled {
_ = session.Exit(1)
logger.Error(ctx, "x11 handler failed")
return
}
env = append(env, fmt.Sprintf("DISPLAY=localhost:%d.%d", display, x11.ScreenNumber))
}

err := s.sessionStart(logger, session, env, magicType)
var exitError *exec.ExitError
if xerrors.As(err, &exitError) {
code := exitError.ExitCode()
Expand Down Expand Up @@ -379,32 +439,8 @@ func (s *Server) fileTransferBlocked(session ssh.Session) bool {
return false
}

func (s *Server) sessionStart(logger slog.Logger, session ssh.Session, extraEnv []string) (retErr error) {
func (s *Server) sessionStart(logger slog.Logger, session ssh.Session, env []string, magicType MagicSessionType) (retErr error) {
ctx := session.Context()
env := append(session.Environ(), extraEnv...)
var magicType string
for index, kv := range env {
if !strings.HasPrefix(kv, MagicSessionTypeEnvironmentVariable) {
continue
}
magicType = strings.ToLower(strings.TrimPrefix(kv, MagicSessionTypeEnvironmentVariable+"="))
env = append(env[:index], env[index+1:]...)
}

// Always force lowercase checking to be case-insensitive.
switch magicType {
case MagicSessionTypeVSCode:
s.connCountVSCode.Add(1)
defer s.connCountVSCode.Add(-1)
case MagicSessionTypeJetBrains:
// Do nothing here because JetBrains launches hundreds of ssh sessions.
// We instead track JetBrains in the single persistent tcp forwarding channel.
case "":
s.connCountSSHSession.Add(1)
defer s.connCountSSHSession.Add(-1)
default:
logger.Warn(ctx, "invalid magic ssh session type specified", slog.F("type", magicType))
}

magicTypeLabel := magicTypeMetricLabel(magicType)
sshPty, windowSize, isPty := session.Pty()
Expand Down Expand Up @@ -473,7 +509,7 @@ func (s *Server) startNonPTYSession(logger slog.Logger, session ssh.Session, mag
}()
go func() {
for sig := range sigs {
s.handleSignal(logger, sig, cmd.Process, magicTypeLabel)
handleSignal(logger, sig, cmd.Process, s.metrics, magicTypeLabel)
}
}()
return cmd.Wait()
Expand Down Expand Up @@ -558,7 +594,7 @@ func (s *Server) startPTYSession(logger slog.Logger, session ptySession, magicTy
sigs = nil
continue
}
s.handleSignal(logger, sig, process, magicTypeLabel)
handleSignal(logger, sig, process, s.metrics, magicTypeLabel)
case win, ok := <-windowSize:
if !ok {
windowSize = nil
Expand Down Expand Up @@ -612,15 +648,15 @@ func (s *Server) startPTYSession(logger slog.Logger, session ptySession, magicTy
return nil
}

func (s *Server) handleSignal(logger slog.Logger, ssig ssh.Signal, signaler interface{ Signal(os.Signal) error }, magicTypeLabel string) {
func handleSignal(logger slog.Logger, ssig ssh.Signal, signaler interface{ Signal(os.Signal) error }, metrics *sshServerMetrics, magicTypeLabel string) {
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👍

ctx := context.Background()
sig := osSignalFrom(ssig)
logger = logger.With(slog.F("ssh_signal", ssig), slog.F("signal", sig.String()))
logger.Info(ctx, "received signal from client")
err := signaler.Signal(sig)
if err != nil {
logger.Warn(ctx, "signaling the process failed", slog.Error(err))
s.metrics.sessionErrors.WithLabelValues(magicTypeLabel, "yes", "signal").Add(1)
metrics.sessionErrors.WithLabelValues(magicTypeLabel, "yes", "signal").Add(1)
}
}

Expand Down
10 changes: 5 additions & 5 deletions agent/agentssh/metrics.go
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Original file line number Diff line number Diff line change
Expand Up @@ -71,15 +71,15 @@ func newSSHServerMetrics(registerer prometheus.Registerer) *sshServerMetrics {
}
}

func magicTypeMetricLabel(magicType string) string {
func magicTypeMetricLabel(magicType MagicSessionType) string {
switch magicType {
case MagicSessionTypeVSCode:
case MagicSessionTypeJetBrains:
case "":
magicType = "ssh"
Comment on lines -78 to -79
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This smells like some cutover compatibility logic here.

case MagicSessionTypeSSH:
case MagicSessionTypeUnknown:
default:
magicType = "unknown"
magicType = MagicSessionTypeUnknown
}
// Always be case insensitive
return strings.ToLower(magicType)
return strings.ToLower(string(magicType))
}
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