cmd/gitbay-runner/main.go
580 lines · 20303 bytes
1// gitbay-runner executes CI builds queued by a gitbay server. It polls over
2// SSH — the same authenticated channel everything else uses — claims one
3// build at a time, clones the repo, runs each step with `sh -c`, streams the
4// combined output back, and reports success or failure.
5//
6// The account behind the runner's key must be an instance admin: a runner
7// executes arbitrary repo code, so handing out jobs is the operator's call.
8// v1 runs steps directly on the host under this process's user; run it as a
9// dedicated unprivileged user.
10package main
11
12import (
13 "encoding/json"
14 "flag"
15 "fmt"
16 "io"
17 "log"
18 "os"
19 "os/exec"
20 "os/signal"
21 "path/filepath"
22 "slices"
23 "strings"
24 "sync"
25 "syscall"
26 "time"
27
28 "gitbay.org/gitbay/internal/buildinfo"
29 "gitbay.org/gitbay/internal/toolpath"
30)
31
32type job struct {
33 ID int64 `json:"id"`
34 Repo string `json:"repo"`
35 Number int64 `json:"number"`
36 Job string `json:"job"`
37 SHA string `json:"sha"`
38 Ref string `json:"ref"`
39 Steps []string `json:"steps"`
40 Image string `json:"image"`
41 Secrets map[string]string `json:"secrets"`
42}
43
44type runner struct {
45 remote string // ssh destination, e.g. git@gitbay.org
46 sshOpts []string
47 cloneBase string // e.g. ssh://git@gitbay.org
48 workdir string
49 timeout time.Duration
50 // image is the container image for a job that names none, and
51 // isolation selects how steps run: "podman" or "none".
52 image string
53 isolation string
54 // memory and cpus cap one build's cgroup; empty means no cap.
55 memory string
56 cpus string
57 // cgroups is the runner's build cgroup subtree, nil where the unit
58 // is not delegated and builds run unconfined in the service cgroup.
59 cgroups *buildCgroups
60 // stepFn is step, replaceable by tests.
61 stepFn func() (bool, error)
62 // repos limits which repositories this runner claims builds for. Empty
63 // means any, which is what a runner on the server itself wants; a runner
64 // somewhere that should not execute every repository's steps names them.
65 repos []string
66 // untrusted also claims merge request heads from forks.
67 untrusted bool
68}
69
70func main() {
71 if len(os.Args) > 1 && os.Args[1] == "init" {
72 os.Exit(runInit(os.Args[2:]))
73 }
74 var (
75 configPath = flag.String("config", defaultConfigPath(), "config file; keys are these flag names, flags override it")
76 identity = flag.String("identity", "", "ssh private key to poll and clone with (default: the key gitbay-runner init generated, if present)")
77 untrusted = flag.Bool("untrusted", false, "also claim untrusted builds: merge request heads from forks (needs -isolation podman to be safe)")
78 remote = flag.String("remote", "git@gitbay.org", "ssh destination of the gitbay server")
79 sshOpts = flag.String("ssh-opts", "", "extra ssh options, space-separated (also used for git clone)")
80 cloneBase = flag.String("clone-base", "", "clone URL prefix (default ssh://<remote>)")
81 workdir = flag.String("workdir", defaultWorkdir(), "build workspace root")
82 poll = flag.Duration("poll", 5*time.Second, "idle poll interval")
83 timeout = flag.Duration("timeout", 30*time.Minute, "per-build time limit")
84 repos = flag.String("repos", "", "only claim builds for these repositories, comma-separated owner/name (default: any)")
85 once = flag.Bool("once", false, "process at most one build, then exit")
86 jobs = flag.Int("jobs", 1, "builds to run at once")
87 image = flag.String("image", "", "default container image for jobs that name none")
88 isolation = flag.String("isolation", "podman", "how steps run: podman, or none for no container")
89 memory = flag.String("memory", "", "memory limit per build, e.g. 4g (podman only, needs a delegated cgroup; default unlimited)")
90 cpus = flag.String("cpus", "", "CPU limit per build, e.g. 2 (podman only, needs a delegated cgroup; default unlimited)")
91 version = flag.Bool("version", false, "print the commit this binary was built from, then exit")
92 )
93 path := configPathFromArgs(os.Args[1:], *configPath)
94 if values, found, err := loadConfig(path); err != nil {
95 log.Fatal(err)
96 } else if found {
97 if err := applyConfig(flag.CommandLine, values); err != nil {
98 log.Fatal(err)
99 }
100 log.Printf("config: %s", path)
101 }
102 flag.Parse()
103 if *version {
104 fmt.Println(buildinfo.String())
105 return
106 }
107 // The runner links internal/store, so it goes stale on changes that never
108 // touch cmd/gitbay-runner. Say which commit is running.
109 log.Printf("gitbay-runner %s", buildinfo.String())
110 r := &runner{
111 remote: *remote,
112 cloneBase: *cloneBase,
113 workdir: *workdir,
114 timeout: *timeout,
115 image: *image,
116 isolation: *isolation,
117 memory: *memory,
118 cpus: *cpus,
119 }
120 if r.isolation == isolationPodman {
121 // Before podman runs anything: its pause process lands in the
122 // cgroup of the first invocation, and that must be the runner's
123 // leaf, not a build's.
124 cg, err := prepareBuildCgroups()
125 switch {
126 case err == nil:
127 r.cgroups = cg
128 case r.memory != "" || r.cpus != "":
129 // Limits that cannot be applied are refused, not dropped:
130 // a runner that accepted -memory and ran uncapped is what
131 // #188 was.
132 log.Fatalf("-memory/-cpus: build cgroups unavailable: %v", err)
133 default:
134 log.Printf("build cgroups unavailable (%v); builds run unconfined in the service cgroup", err)
135 }
136 }
137 if err := r.checkIsolation(); err != nil {
138 // Refusing to start is the point. A runner that quietly fell back
139 // to running repository code on the host would drop isolation
140 // with nothing to surface it, which is worse than a stopped
141 // runner: the operator sees a failed unit either way, but only
142 // one of them is honest about why (#144).
143 log.Fatalf("isolation: %v", err)
144 }
145 if *sshOpts != "" {
146 r.sshOpts = strings.Fields(*sshOpts)
147 }
148 if *identity == "" {
149 if p := filepath.Join(configDir(), "id_ed25519"); fileExists(p) {
150 *identity = p
151 }
152 }
153 // Clipped: the later appends run from concurrent workers, and spare
154 // capacity here would have them writing the same backing array.
155 r.sshOpts = slices.Clip(sshOptions(*identity, r.sshOpts))
156 r.untrusted = *untrusted
157 for _, name := range strings.Split(*repos, ",") {
158 if name = strings.TrimSpace(name); name != "" {
159 r.repos = append(r.repos, name)
160 }
161 }
162 if r.cloneBase == "" {
163 r.cloneBase = "ssh://" + *remote
164 }
165 // 0o700, not 0o755: a build's checkout and its secrets-bearing
166 // environment are this user's business alone, and the default sits
167 // beside other users' data on a shared host.
168 if err := os.MkdirAll(r.workdir, 0o700); err != nil {
169 log.Fatal(err)
170 }
171 if err := checkWorkdir(r.workdir); err != nil {
172 log.Fatal(err)
173 }
174 n := *jobs
175 if n < 1 {
176 log.Fatal("-jobs must be at least 1")
177 }
178 if *once {
179 // "at most one build" is one build, whatever -jobs says.
180 n = 1
181 }
182 // `runner next` claims inside one transaction, so several workers
183 // claiming at once is already safe; the runner just never used that.
184 // Each build works in its own build-<id> directory, so they do not
185 // meet on disk either.
186 // A stop signal drains: no build is claimed after it, and each build
187 // already in flight runs to completion and is reported. The old
188 // behaviour was to die mid-build, which left the build "running" on
189 // the server with nothing executing (#179). The unit's
190 // TimeoutStopSec bounds the drain; a second signal ends it now.
191 stop := make(chan struct{})
192 go func() {
193 sigs := make(chan os.Signal, 2)
194 signal.Notify(sigs, syscall.SIGTERM, syscall.SIGINT)
195 <-sigs
196 log.Printf("draining: finishing builds in flight, claiming no more")
197 close(stop)
198 <-sigs
199 log.Printf("second signal: exiting without draining")
200 os.Exit(1)
201 }()
202 r.serve(n, *once, *poll, stop)
203}
204
205// serve runs n workers until stop closes. A worker checks stop only
206// between builds, so closing it never interrupts one.
207func (r *runner) serve(n int, once bool, poll time.Duration, stop <-chan struct{}) {
208 if r.stepFn == nil {
209 r.stepFn = r.step
210 }
211 var wg sync.WaitGroup
212 for i := 0; i < n; i++ {
213 wg.Add(1)
214 go func(i int) {
215 defer wg.Done()
216 if n > 1 {
217 time.Sleep(time.Duration(i) * poll / time.Duration(n))
218 }
219 for {
220 select {
221 case <-stop:
222 return
223 default:
224 }
225 ran, err := r.stepFn()
226 if err != nil {
227 log.Printf("runner: %v", err)
228 }
229 if once {
230 return
231 }
232 if !ran {
233 select {
234 case <-stop:
235 return
236 case <-time.After(poll):
237 }
238 }
239 }
240 }(i)
241 }
242 wg.Wait()
243}
244
245// step claims and executes at most one build. ran reports whether there was
246// one, so the caller knows when to idle.
247func (r *runner) step() (bool, error) {
248 args := []string{"runner", "next"}
249 if r.untrusted {
250 args = append(args, "--untrusted")
251 }
252 args = append(append(args, r.repos...), "--json")
253 out, err := r.ssh(nil, args...)
254 if err != nil {
255 return false, fmt.Errorf("claiming build: %w (%s)", err, out)
256 }
257 var env struct {
258 Data job `json:"data"`
259 }
260 if err := json.Unmarshal([]byte(out), &env); err != nil {
261 return false, fmt.Errorf("parsing job: %w", err)
262 }
263 if env.Data.ID == 0 {
264 return false, nil
265 }
266 j := env.Data
267 log.Printf("build %d: %s %s @ %.10s", j.ID, j.Repo, j.Job, j.SHA)
268 status := "failure"
269 if r.run(j) {
270 status = "success"
271 }
272 if err := r.reportDone(j.ID, status); err != nil {
273 return true, err
274 }
275 log.Printf("build %d: %s", j.ID, status)
276 return true, nil
277}
278
279// logSink forwards a build's output to the server and swallows any error
280// doing so. os/exec surfaces a write failure on a step's stdout through
281// cmd.Wait(), so a sink that can fail is a sink that can fail the build it
282// was only recording — a restart or a dropped session used to turn a green
283// suite red, with the explaining line written to the same dead pipe. Losing
284// log lines is the acceptable failure here; losing the build is not.
285type logSink struct {
286 mu sync.Mutex
287 w io.Writer // nil once a write has failed
288}
289
290func (s *logSink) Write(p []byte) (int, error) {
291 s.mu.Lock()
292 defer s.mu.Unlock()
293 if s.w != nil {
294 if _, err := s.w.Write(p); err != nil {
295 s.w = nil
296 }
297 }
298 return len(p), nil
299}
300
301// broken reports whether the stream was lost, so a build can say its log is
302// incomplete rather than appear to have simply stopped.
303func (s *logSink) broken() bool {
304 s.mu.Lock()
305 defer s.mu.Unlock()
306 return s.w == nil
307}
308
309// run clones, checks out, and executes the steps, streaming output to the
310// server. Returns whether every step succeeded.
311func (r *runner) run(j job) bool {
312 dir := filepath.Join(r.workdir, fmt.Sprintf("build-%d", j.ID))
313 defer os.RemoveAll(dir)
314
315 // A build's HOME. Not the workspace, which is removed after every
316 // build: the Go module cache, the sonar scanner and every other tool
317 // cache live under HOME, so a per-build one re-downloads the world
318 // each time. Not the runner's own home either, where its SSH key and
319 // credential dotfiles are. A directory beside the workspaces is
320 // neither.
321 //
322 // One per repository: shared across repositories, a step could poison
323 // the module cache or plant a .gitconfig that another repository's
324 // build would honour, and the container mounts the home read-write
325 // (#184).
326 buildHome, err := buildHomeFor(r.workdir, j.Repo)
327 if err != nil {
328 log.Printf("build %d: build home: %v", j.ID, err)
329 return false
330 }
331
332 // One long-lived `runner log` session receives the whole stream.
333 logCmd := exec.Command(toolpath.Look("ssh"), append(r.sshOpts, r.remote, "runner", "log", fmt.Sprint(j.ID))...)
334 pipe, err := logCmd.StdinPipe()
335 if err != nil {
336 log.Printf("build %d: log pipe: %v", j.ID, err)
337 return false
338 }
339 sink := &logSink{w: pipe}
340 logCmd.Stdout, logCmd.Stderr = io.Discard, io.Discard
341 if err := logCmd.Start(); err != nil {
342 log.Printf("build %d: log stream: %v", j.ID, err)
343 return false
344 }
345 // The server ends the log session with exit 3 when the build is
346 // cancelled; any other end is a lost stream, which the sink absorbs.
347 cancelled := make(chan struct{})
348 logExited := make(chan struct{})
349 go func() {
350 defer close(logExited)
351 err := logCmd.Wait()
352 if ee, ok := err.(*exec.ExitError); ok && ee.ExitCode() == 3 {
353 close(cancelled)
354 return
355 }
356 if err != nil {
357 log.Printf("build %d: log session ended: %v", j.ID, err)
358 }
359 }()
360 // runStep starts cmd and waits for it, the cancel signal, or the
361 // deadline. Every phase goes through it, so a cancel during the clone
362 // lands as fast as one during a step.
363 runStep := func(cmd *exec.Cmd, deadline time.Time) (bool, string) {
364 select {
365 case <-cancelled:
366 return false, "cancelled"
367 default:
368 }
369 ownProcessGroup(cmd)
370 if err := cmd.Start(); err != nil {
371 return false, fmt.Sprintf("start: %v", err)
372 }
373 done := make(chan error, 1)
374 go func() { done <- cmd.Wait() }()
375 // After a kill, Wait returns once every holder of the log pipe is
376 // gone; the group kill makes that prompt, and the cap makes sure a
377 // straggler cannot hold the build open.
378 reap := func() {
379 killTree(cmd)
380 select {
381 case <-done:
382 case <-time.After(10 * time.Second):
383 }
384 }
385 select {
386 case err := <-done:
387 if err != nil {
388 return false, fmt.Sprintf("step failed: %v", err)
389 }
390 return true, ""
391 case <-cancelled:
392 reap()
393 return false, "cancelled"
394 case <-time.After(time.Until(deadline)):
395 reap()
396 return false, fmt.Sprintf("build timed out after %s", r.timeout)
397 }
398 }
399 defer func() {
400 select {
401 case <-cancelled:
402 log.Printf("build %d: cancelled", j.ID)
403 default:
404 if sink.broken() {
405 log.Printf("build %d: log stream lost; stored log is incomplete", j.ID)
406 }
407 }
408 pipe.Close()
409 <-logExited
410 }()
411
412 gitSSH := strings.TrimSpace("ssh " + strings.Join(r.sshOpts, " "))
413 cloneURL := r.cloneBase + "/" + j.Repo + ".git"
414 deadline := time.Now().Add(r.timeout)
415 fmt.Fprintf(sink, "$ git clone %s (%.10s)\n", cloneURL, j.SHA)
416 // A merge request head lives under refs/merge-requests/, which a
417 // clone does not fetch; ask for the ref before checking out.
418 steps := [][]string{{"clone", "-q", cloneURL, dir}}
419 if strings.HasPrefix(j.Ref, "refs/") {
420 steps = append(steps, []string{"-C", dir, "fetch", "-q", "origin", j.Ref})
421 }
422 steps = append(steps, []string{"-C", dir, "checkout", "-q", j.SHA})
423 for _, args := range steps {
424 cmd := exec.Command(toolpath.Look("git"), args...)
425 cmd.Env = append(os.Environ(), "GIT_SSH_COMMAND="+gitSSH, "GIT_TERMINAL_PROMPT=0")
426 cmd.Stdout, cmd.Stderr = sink, sink
427 if ok, why := runStep(cmd, deadline); !ok {
428 fmt.Fprintf(sink, "git %s: %s\n", args[0], why)
429 return false
430 }
431 }
432
433 env := stepEnv(j, buildHome, r.buildSSH())
434 return r.runSteps(j, dir, env, sink, deadline, runStep)
435}
436
437// stepEnv builds the environment a build step runs with. It is
438// constructed, not inherited: os.Environ() would hand repository content
439// the runner's entire environment, including anything an operator set on
440// the service (#144).
441//
442// HOME is the repository's build home, not the runner's own: tools read
443// credentials out of dotfiles — .netrc, .npmrc, .gitconfig — and a build
444// has no business finding the runner's. It is not the workspace either,
445// because the workspace is deleted after every build and every tool
446// cache lives under HOME.
447//
448// PATH is the one thing carried over: without it a step cannot find the
449// tools the host was provisioned with.
450// buildHomeFor is the build home for one repository: <workdir>/home/<owner>/<name>,
451// created on first use. The repository path comes from the server, but a
452// home must still never resolve outside the home root.
453func buildHomeFor(workdir, repo string) (string, error) {
454 root := filepath.Join(workdir, "home")
455 dir := filepath.Join(root, filepath.FromSlash(repo))
456 if rel, err := filepath.Rel(root, dir); err != nil || rel == "." || strings.HasPrefix(rel, "..") {
457 return "", fmt.Errorf("repository path %q escapes the build home root", repo)
458 }
459 if err := os.MkdirAll(dir, 0o700); err != nil {
460 return "", err
461 }
462 return dir, nil
463}
464
465// buildSSH is the instance's ssh destination as a build reaches it. Under
466// podman, pasta gives the container the host's own addresses, so a
467// loopback remote — the runner on the server itself — is unreachable by
468// that name; pasta exposes the host at 169.254.1.2, its
469// --map-host-loopback default. Any other remote is a real host elsewhere
470// and works as it is.
471func (r *runner) buildSSH() string {
472 if r.isolation != isolationPodman {
473 return r.remote
474 }
475 user, host, hasUser := strings.Cut(r.remote, "@")
476 if !hasUser {
477 user, host = "", user
478 }
479 if host != "127.0.0.1" && host != "localhost" && host != "::1" {
480 return r.remote
481 }
482 if hasUser {
483 return user + "@169.254.1.2"
484 }
485 return "169.254.1.2"
486}
487
488func stepEnv(j job, home, sshDest string) []string {
489 path := os.Getenv("PATH")
490 if path == "" {
491 path = "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
492 }
493 env := []string{
494 "PATH=" + path,
495 "HOME=" + home,
496 "LANG=C.UTF-8",
497 "CI=true",
498 "GITBAY_REPO=" + j.Repo,
499 "GITBAY_SHA=" + j.SHA,
500 "GITBAY_REF=" + j.Ref,
501 "GITBAY_JOB=" + j.Job,
502 "GITBAY_SSH=" + sshDest,
503 }
504 // The server sends secrets only for a trusted build — a merge request
505 // head from a fork arrives with none — so this loop is empty exactly
506 // when it should be.
507 for name, value := range j.Secrets {
508 env = append(env, name+"="+value)
509 }
510 return env
511}
512
513// ssh runs one control command against the server and returns stdout.// ssh runs one control command against the server and returns stdout.
514func (r *runner) ssh(stdin io.Reader, args ...string) (string, error) {
515 cmd := exec.Command(toolpath.Look("ssh"), append(append(r.sshOpts, r.remote), args...)...)
516 if stdin != nil {
517 cmd.Stdin = stdin
518 }
519 var out, errOut strings.Builder
520 cmd.Stdout, cmd.Stderr = &out, &errOut
521 if err := cmd.Run(); err != nil {
522 return out.String() + errOut.String(), err
523 }
524 return out.String(), nil
525}
526
527func fileExists(p string) bool { _, err := os.Stat(p); return err == nil }
528
529// defaultWorkdir picks a build workspace that another local user cannot
530// have created first.
531//
532// The default used to be <tmp>/gitbay-runner: a fixed name inside a
533// world-writable directory, created with MkdirAll, which succeeds against
534// an existing directory whoever owns it. On a shared host another user
535// could have made it — or symlinked it — before the runner started, and
536// this is the process that clones repositories and exports build secrets
537// into step environments (go:S5445, #153).
538//
539// The user's cache directory is not world-writable and is per-user by
540// construction. Falling back to tmp keeps a runner working where HOME is
541// unset, and checkWorkdir refuses the unsafe cases there.
542func defaultWorkdir() string {
543 if cache, err := os.UserCacheDir(); err == nil && cache != "" {
544 return filepath.Join(cache, "gitbay-runner")
545 }
546 return filepath.Join(os.TempDir(), "gitbay-runner")
547}
548
549// checkWorkdir makes sure the workspace is a directory this user owns
550// privately. MkdirAll is happy with one that already exists, so being
551// able to create it proves nothing about who made it.
552//
553// A directory we own that is merely too permissive is tightened rather
554// than refused: every runner before this one created its workspace 0755,
555// so refusing would take the runner down on upgrade to fix a permission
556// we are entitled to change. What cannot be repaired — a symlink, or
557// something owned by someone else — is refused, because those are what an
558// attacker leaves behind and neither is ours to correct.
559func checkWorkdir(dir string) error {
560 fi, err := os.Lstat(dir)
561 if err != nil {
562 return err
563 }
564 if fi.Mode()&os.ModeSymlink != 0 {
565 return fmt.Errorf("workdir %s is a symlink; point -workdir at a real directory", dir)
566 }
567 if !fi.IsDir() {
568 return fmt.Errorf("workdir %s is not a directory", dir)
569 }
570 if st, ok := fi.Sys().(*syscall.Stat_t); ok && int(st.Uid) != os.Getuid() {
571 return fmt.Errorf("workdir %s is owned by uid %d, not this process's %d", dir, st.Uid, os.Getuid())
572 }
573 if perm := fi.Mode().Perm(); perm&0o077 != 0 {
574 log.Printf("workdir %s was mode %04o; tightening to 0700 (builds and their secrets are this user's alone)", dir, perm)
575 if err := os.Chmod(dir, 0o700); err != nil {
576 return fmt.Errorf("tightening workdir %s: %w", dir, err)
577 }
578 }
579 return nil
580}