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authorOphestra <cat@gensokyo.uk>2025-06-25 03:59:52 +0900
committerOphestra <cat@gensokyo.uk>2025-06-25 04:57:41 +0900
commit87e008d56de974947ebb99c2cc40b25d3c2cf43e (patch)
tree31791911e5226d6ec04e3fac7d91b0bf53e63aa5 /cmd/fsu/main.go
parent399207321265307bb15f37d867f9370cd51c82a8 (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.go146
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")
-}