| 1 | //go:build linux |
| 2 | |
| 3 | package console |
| 4 | |
| 5 | import ( |
| 6 | "fmt" |
| 7 | "os" |
| 8 | "strconv" |
| 9 | "strings" |
| 10 | "sync" |
| 11 | "syscall" |
| 12 | ) |
| 13 | |
| 14 | var hostReportProcReadFile = os.ReadFile |
| 15 | var hostReportProcessIdentity = sync.OnceValue(readHostReportProcessIdentity) |
| 16 | |
| 17 | func hostReportProcessStart(pid int) (string, error) { |
| 18 | raw, err := hostReportProcReadFile(fmt.Sprintf("/proc/%d/stat", pid)) |
| 19 | if err != nil { |
| 20 | return "", err |
| 21 | } |
| 22 | end := strings.LastIndexByte(string(raw), ')') |
| 23 | if end < 0 { |
| 24 | return "", os.ErrInvalid |
| 25 | } |
| 26 | fields := strings.Fields(string(raw[end+1:])) |
| 27 | if len(fields) < 20 { |
| 28 | return "", os.ErrInvalid |
| 29 | } |
| 30 | start, err := strconv.ParseUint(fields[19], 10, 64) |
| 31 | if err != nil || start == 0 { |
| 32 | return "", os.ErrInvalid |
| 33 | } |
| 34 | return fields[19], nil |
| 35 | } |
| 36 | |
| 37 | var hostReportPIDNamespace = func() (string, error) { |
| 38 | info, err := os.Stat("/proc/self/ns/pid") |
| 39 | if err != nil { |
| 40 | return "", err |
| 41 | } |
| 42 | st, ok := info.Sys().(*syscall.Stat_t) |
| 43 | if !ok || st.Ino == 0 { |
| 44 | return "", os.ErrInvalid |
| 45 | } |
| 46 | return strconv.FormatUint(st.Ino, 10), nil |
| 47 | } |
| 48 | |
| 49 | func readHostReportProcessIdentity() string { |
| 50 | namespace, namespaceErr := hostReportPIDNamespace() |
| 51 | start, err := hostReportProcessStart(os.Getpid()) |
| 52 | if err != nil || namespaceErr != nil { |
| 53 | return strconv.Itoa(os.Getpid()) |
| 54 | } |
| 55 | return fmt.Sprintf("%s:%d:%s", namespace, os.Getpid(), start) |
| 56 | } |
| 57 | |
| 58 | func hostReportProcessID(boot string) string { |
| 59 | return boot + ":" + hostReportProcessIdentity() |
| 60 | } |
| 61 | |
| 62 | // Linux reserves PID_NS_INIT_INO (formerly PROC_PID_INIT_INO) for its initial |
| 63 | // PID namespace. A container's own procfs also makes /proc/1 match self, so |
| 64 | // that match alone cannot prove main's legacy boot:pid is local. |
| 65 | // See include/uapi/linux/nsfs.h in the kernel source. |
| 66 | const hostReportInitialPIDNamespace = "4026531836" // 0xEFFFFFFC |
| 67 | |
| 68 | var hostReportRootPIDNamespace = func() (string, error) { |
| 69 | info, err := os.Stat("/proc/1/ns/pid") |
| 70 | if err != nil { |
| 71 | return "", err |
| 72 | } |
| 73 | st, ok := info.Sys().(*syscall.Stat_t) |
| 74 | if !ok || st.Ino == 0 { |
| 75 | return "", os.ErrInvalid |
| 76 | } |
| 77 | return strconv.FormatUint(st.Ino, 10), nil |
| 78 | } |
| 79 | |
| 80 | func hostReportProcessGone(previous, next string) bool { |
| 81 | old, current := strings.Split(previous, ":"), strings.Split(next, ":") |
| 82 | switch { |
| 83 | case len(old) == 4 && len(current) == 4 && old[0] == current[0] && old[1] == current[1]: |
| 84 | namespace, err := hostReportPIDNamespace() |
| 85 | if err != nil || namespace != old[1] || !hostReportBootMatches(old[0]) { |
| 86 | return false |
| 87 | } |
| 88 | if start, err := strconv.ParseUint(old[3], 10, 64); err != nil || start == 0 { |
| 89 | return false |
| 90 | } |
| 91 | return hostReportPIDAbsent(old[2]) |
| 92 | case len(old) == 2 && len(current) >= 2 && old[0] == current[0]: |
| 93 | // Main's boot:pid. It carries no namespace, but main only ran in the |
| 94 | // host namespace, so accept it only from a process in that namespace |
| 95 | // on the same boot, and only with the same absence proof. |
| 96 | namespace, err := hostReportPIDNamespace() |
| 97 | if err != nil { |
| 98 | return false |
| 99 | } |
| 100 | root, err := hostReportRootPIDNamespace() |
| 101 | if err != nil || root != hostReportInitialPIDNamespace || root != namespace || !hostReportBootMatches(old[0]) { |
| 102 | return false |
| 103 | } |
| 104 | return hostReportPIDAbsent(old[1]) |
| 105 | } |
| 106 | return false |
| 107 | } |
| 108 | |
| 109 | func hostReportBootMatches(boot string) bool { |
| 110 | raw, err := hostReportProcReadFile("/proc/sys/kernel/random/boot_id") |
| 111 | return err == nil && strings.TrimSpace(string(raw)) == boot |
| 112 | } |
| 113 | |
| 114 | func hostReportPIDAbsent(text string) bool { |
| 115 | pid, err := strconv.Atoi(text) |
| 116 | if err != nil || pid <= 0 { |
| 117 | return false |
| 118 | } |
| 119 | _, err = hostReportProcessStart(pid) |
| 120 | if !os.IsNotExist(err) { |
| 121 | return false |
| 122 | } |
| 123 | // A filtered proc mount may hide a live PID. Signal 0 sends no signal; |
| 124 | // only ESRCH in the matching PID namespace proves that PID is absent. |
| 125 | return syscall.Kill(pid, 0) == syscall.ESRCH |
| 126 | } |
| 127 | |
amadan