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remoteagent.go
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remoteagent.go
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package remoteagent
import (
"bufio"
"context"
"errors"
"fmt"
"github.com/avast/retry-go/v4"
"github.com/cirruslabs/cirrus-cli/internal/executor/endpoint"
"github.com/cirruslabs/cirrus-cli/internal/executor/instance/runconfig"
"github.com/cirruslabs/cirrus-cli/internal/logger"
"go.opentelemetry.io/otel"
"golang.org/x/crypto/ssh"
"io"
"net"
"strconv"
"strings"
"time"
)
var (
ErrFailed = errors.New("remote agent failed")
tracer = otel.Tracer("remoteagent")
)
type WaitForAgentHook func(ctx context.Context, sshClient *ssh.Client) error
type WaitForAgentHooks []WaitForAgentHook
func (hooks WaitForAgentHooks) Run(ctx context.Context, cli *ssh.Client) error {
ctx, span := tracer.Start(ctx, "run-hooks")
defer span.End()
for _, hook := range hooks {
if err := hook(ctx, cli); err != nil {
return err
}
}
return nil
}
func WaitForAgent(
ctx context.Context,
logger logger.Lightweight,
ip string,
sshUser string,
sshPassword string,
agentOS string,
agentArchitecture string,
config *runconfig.RunConfig,
synchronizeTime bool,
initializeHooks WaitForAgentHooks,
terminateHooks WaitForAgentHooks,
preCreatedWorkingDir string,
) error {
ctx, span := tracer.Start(ctx, "upload-and-wait-for-agent")
defer span.End()
addr := ip + ":22"
cli, err := connectViaSSH(ctx, logger, addr, sshUser, sshPassword)
if err != nil {
return err
}
// Work around x/crypto/ssh not being context.Context-friendly (e.g. https://github.com/golang/go/issues/20288)
monitorCtx, monitorCancel := context.WithCancel(ctx)
go func() {
<-monitorCtx.Done()
_ = cli.Close()
}()
defer monitorCancel()
logger.Debugf("running initialization hooks on %s...", addr)
if err := initializeHooks.Run(ctx, cli); err != nil {
return err
}
logger.Debugf("uploading agent to %s...", addr)
remoteAgentPath, err := uploadAgent(ctx, cli, agentOS, config.GetAgentVersion(), agentArchitecture)
if err != nil {
return fmt.Errorf("%w: failed to upload agent via SFTP: %v",
ErrFailed, err)
}
sess, err := cli.NewSession()
if err != nil {
return fmt.Errorf("%w: failed to open SSH session: %v", ErrFailed, err)
}
// Log output from the virtual machine
stdout, err := sess.StdoutPipe()
if err != nil {
return fmt.Errorf("%w: while opening stdout pipe: %v", ErrFailed, err)
}
stderr, err := sess.StderrPipe()
if err != nil {
return fmt.Errorf("%w: while opening stderr pipe: %v", ErrFailed, err)
}
go func() {
output := io.MultiReader(stdout, stderr)
scanner := bufio.NewScanner(output)
for scanner.Scan() {
logger.Debugf("VM: %s", scanner.Text())
}
}()
stdinBuf, err := sess.StdinPipe()
if err != nil {
return fmt.Errorf("%w: while opening stdin pipe: %v", ErrFailed, err)
}
// start a login shell so all the customization from ~/.zprofile will be picked up
err = sess.Shell()
if err != nil {
return fmt.Errorf("%w: failed to start a shell: %v", ErrFailed, err)
}
// Synchronize time for suspended VMs
if synchronizeTime {
_, err = stdinBuf.Write([]byte(TimeSyncCommand(time.Now().UTC())))
if err != nil {
return fmt.Errorf("%w: failed to sync time: %v", ErrFailed, err)
}
}
var apiEndpoint string
switch config.Endpoint.(type) {
case *endpoint.Local:
// Expose local RPC service to the VM via SSH port forwarding
vmListener, err := cli.Listen("tcp", "127.0.0.1:0")
if err != nil {
return fmt.Errorf("%w: failed to set-up SSH port forwarding: %v", ErrFailed, err)
}
defer vmListener.Close()
go forwardViaSSH(vmListener, logger, config.Endpoint.Direct())
apiEndpoint = "http://" + vmListener.Addr().String()
default:
apiEndpoint = config.Endpoint.Direct()
}
command := []string{
remoteAgentPath,
"-api-endpoint",
apiEndpoint,
"-server-token",
"\"" + config.ServerSecret + "\"",
"-client-token",
"\"" + config.ClientSecret + "\"",
"-task-id",
strconv.FormatInt(config.TaskID, 10),
}
if preCreatedWorkingDir != "" {
command = append(command, "-pre-created-working-dir", "\""+preCreatedWorkingDir+"\"")
}
// Start the agent and wait for it to terminate
logger.Debugf("running agent on %s with arguments: %v...", addr, command)
_, err = stdinBuf.Write([]byte(strings.Join(command, " ") + "\nexit\n"))
if err != nil {
return fmt.Errorf("%w: failed to start agent: %v", ErrFailed, err)
}
err = sess.Wait()
if err != nil {
// Work around x/crypto/ssh not being context.Context-friendly (e.g. https://github.com/golang/go/issues/20288)
if err := monitorCtx.Err(); err != nil {
return err
}
return fmt.Errorf("%w: failed to run agent: %v", ErrFailed, err)
}
logger.Debugf("running termination hooks on %s...", addr)
if err := terminateHooks.Run(ctx, cli); err != nil {
return err
}
return nil
}
func forwardViaSSH(vmListener net.Listener, logger logger.Lightweight, endpoint string) {
for {
vmConn, err := vmListener.Accept()
if err != nil {
if errors.Is(err, io.EOF) {
return
}
logger.Debugf("failed to accept connection from the VM on forwarded port: %v", err)
continue
}
// Convert endpoint address to host
host := strings.TrimPrefix(endpoint, "http://")
localConn, err := net.Dial("tcp", host)
if err != nil {
logger.Debugf("failed to connect to the RPC service on %s: %v", endpoint, err)
continue
}
go func() {
defer vmConn.Close()
defer localConn.Close()
_, _ = io.Copy(vmConn, localConn)
}()
go func() {
defer vmConn.Close()
defer localConn.Close()
_, _ = io.Copy(localConn, vmConn)
}()
}
}
func connectViaSSH(
ctx context.Context,
logger logger.Lightweight,
addr string,
sshUser string,
sshPassword string,
) (*ssh.Client, error) {
ctx, span := tracer.Start(ctx, "connect-via-ssh")
defer span.End()
// Connect to the VM and upload the agent
var sshConn ssh.Conn
var chans <-chan ssh.NewChannel
var reqs <-chan *ssh.Request
logger.Debugf("connecting via SSH to %s...", addr)
if err := retry.Do(func() error {
dialer := net.Dialer{
Timeout: time.Second,
}
netConn, err := dialer.DialContext(ctx, "tcp", addr)
if err != nil {
logger.Debugf("failed to dial %s: %v", addr, err)
return err
}
logger.Debugf("successfully dialed %s, performing SSH handshake...", addr)
sshConfig := &ssh.ClientConfig{
HostKeyCallback: func(hostname string, remote net.Addr, key ssh.PublicKey) error {
return nil
},
User: sshUser,
Auth: []ssh.AuthMethod{
ssh.Password(sshPassword),
},
Timeout: time.Second,
}
sshConn, chans, reqs, err = ssh.NewClientConn(netConn, addr, sshConfig)
if err != nil {
err := fmt.Errorf("%w: failed to connect via SSH: %v", ErrFailed, err)
logger.Debugf("failed to perform SSH handshake with %s: %v", addr, err)
return err
}
return nil
}, retry.Context(ctx),
retry.Attempts(0),
retry.DelayType(retry.FixedDelay),
retry.Delay(time.Second),
); err != nil {
return nil, fmt.Errorf("%w: failed to connect via SSH: %v", ErrFailed, err)
}
logger.Debugf("creating new SSH client...")
return ssh.NewClient(sshConn, chans, reqs), nil
}