diff options
| author | Ophestra <cat@gensokyo.uk> | 2025-06-25 03:59:52 +0900 |
|---|---|---|
| committer | Ophestra <cat@gensokyo.uk> | 2025-06-25 04:57:41 +0900 |
| commit | 87e008d56de974947ebb99c2cc40b25d3c2cf43e (patch) | |
| tree | 31791911e5226d6ec04e3fac7d91b0bf53e63aa5 /cmd/fsu/main.go | |
| parent | 399207321265307bb15f37d867f9370cd51c82a8 (diff) | |
treewide: rename to hakurei
Fortify makes little sense for a container tool.
Signed-off-by: Ophestra <cat@gensokyo.uk>
Diffstat (limited to 'cmd/fsu/main.go')
| -rw-r--r-- | cmd/fsu/main.go | 146 |
1 files changed, 0 insertions, 146 deletions
diff --git a/cmd/fsu/main.go b/cmd/fsu/main.go deleted file mode 100644 index 33ecbf43..00000000 --- a/cmd/fsu/main.go +++ /dev/null @@ -1,146 +0,0 @@ -package main - -import ( - "bytes" - "fmt" - "log" - "os" - "path" - "slices" - "strconv" - "strings" - "syscall" -) - -const ( - fsuConfFile = "/etc/fsurc" - envShim = "FORTIFY_SHIM" - envAID = "FORTIFY_APP_ID" - envGroups = "FORTIFY_GROUPS" - - PR_SET_NO_NEW_PRIVS = 0x26 -) - -func main() { - log.SetFlags(0) - log.SetPrefix("fsu: ") - log.SetOutput(os.Stderr) - - if os.Geteuid() != 0 { - log.Fatal("this program must be owned by uid 0 and have the setuid bit set") - } - - puid := os.Getuid() - if puid == 0 { - log.Fatal("this program must not be started by root") - } - - var toolPath string - pexe := path.Join("/proc", strconv.Itoa(os.Getppid()), "exe") - if p, err := os.Readlink(pexe); err != nil { - log.Fatalf("cannot read parent executable path: %v", err) - } else if strings.HasSuffix(p, " (deleted)") { - log.Fatal("fortify executable has been deleted") - } else if p != mustCheckPath(fmain) && p != mustCheckPath(fpkg) { - log.Fatal("this program must be started by fortify") - } else { - toolPath = p - } - - // uid = 1000000 + - // fid * 10000 + - // aid - uid := 1000000 - - // refuse to run if fsurc is not protected correctly - if s, err := os.Stat(fsuConfFile); err != nil { - log.Fatal(err) - } else if s.Mode().Perm() != 0400 { - log.Fatal("bad fsurc perm") - } else if st := s.Sys().(*syscall.Stat_t); st.Uid != 0 || st.Gid != 0 { - log.Fatal("fsurc must be owned by uid 0") - } - - // authenticate before accepting user input - if f, err := os.Open(fsuConfFile); err != nil { - log.Fatal(err) - } else if fid, ok := mustParseConfig(f, puid); !ok { - log.Fatalf("uid %d is not in the fsurc file", puid) - } else { - uid += fid * 10000 - } - - // allowed aid range 0 to 9999 - if as, ok := os.LookupEnv(envAID); !ok { - log.Fatal("FORTIFY_APP_ID not set") - } else if aid, err := parseUint32Fast(as); err != nil || aid < 0 || aid > 9999 { - log.Fatal("invalid aid") - } else { - uid += aid - } - - // pass through setup fd to shim - var shimSetupFd string - if s, ok := os.LookupEnv(envShim); !ok { - // fortify requests target uid - // print resolved uid and exit - fmt.Print(uid) - os.Exit(0) - } else if len(s) != 1 || s[0] > '9' || s[0] < '3' { - log.Fatal("FORTIFY_SHIM holds an invalid value") - } else { - shimSetupFd = s - } - - // supplementary groups - var suppGroups, suppCurrent []int - - if gs, ok := os.LookupEnv(envGroups); ok { - if cur, err := os.Getgroups(); err != nil { - log.Fatalf("cannot get groups: %v", err) - } else { - suppCurrent = cur - } - - // parse space-separated list of group ids - gss := bytes.Split([]byte(gs), []byte{' '}) - suppGroups = make([]int, len(gss)+1) - for i, s := range gss { - if gid, err := strconv.Atoi(string(s)); err != nil { - log.Fatalf("cannot parse %q: %v", string(s), err) - } else if gid > 0 && gid != uid && gid != os.Getgid() && slices.Contains(suppCurrent, gid) { - suppGroups[i] = gid - } else { - log.Fatalf("invalid gid %d", gid) - } - } - suppGroups[len(suppGroups)-1] = uid - } else { - suppGroups = []int{uid} - } - - // final bounds check to catch any bugs - if uid < 1000000 || uid >= 2000000 { - panic("uid out of bounds") - } - - // careful! users in the allowlist is effectively allowed to drop groups via fsu - - if err := syscall.Setresgid(uid, uid, uid); err != nil { - log.Fatalf("cannot set gid: %v", err) - } - if err := syscall.Setgroups(suppGroups); err != nil { - log.Fatalf("cannot set supplementary groups: %v", err) - } - if err := syscall.Setresuid(uid, uid, uid); err != nil { - log.Fatalf("cannot set uid: %v", err) - } - if _, _, errno := syscall.AllThreadsSyscall(syscall.SYS_PRCTL, PR_SET_NO_NEW_PRIVS, 1, 0); errno != 0 { - log.Fatalf("cannot set no_new_privs flag: %s", errno.Error()) - } - if err := syscall.Exec(toolPath, []string{"fortify", "shim"}, []string{envShim + "=" + shimSetupFd}); err != nil { - log.Fatalf("cannot start shim: %v", err) - } - - panic("unreachable") -} |
