mesh-host/internal/accounts/root_test.go

package accounts

import (
	"context"
	"errors"
	"fmt"
	"io/fs"
	"os/exec"
	"strings"
	"testing"

	"github.com/novox/mesh-host/internal/declaration"
)

// An account declared never to become root without a person (novox/hq ADR 0266, "how it is checked"): each
// way to root is found and said, none is healthy whether or not anybody is logged in, an unanswered question
// is unknown, and the judge only reads.

// agentMachine is a fake machine for the escalation question: the account's uid, its groups by name and
// number, what sudo lists, and the secrets' owners and modes.
type agentMachine struct {
	uid     string
	groups  string
	gids    string
	sudo    string
	sudoErr error
	files   map[string]FileMode
	failsID bool
	asked   []string
	// texts are files' contents (doas's, polkit's); dirs a directory's files by name; acls a file's ACL;
	// setuid what the walk finds, one per line, and packaged the paths a package owns.
	texts    map[string]string
	dirs     map[string][]string
	acls     map[string][]ACLEntry
	setuid   string
	findErr  error
	packaged map[string]bool
	// proc is /proc's files, aSafeProc unless a test changes them; findArgs sees the filesystems walked.
	proc     map[string]string
	findArgs func([]string)
	// pacmanCalls counts the package manager's calls: one for every path found.
	pacmanCalls int
}

func (m *agentMachine) readFile(path string) ([]byte, error) {
	if t, ok := m.texts[path]; ok {
		return []byte(t), nil
	}
	if t, ok := m.proc[path]; ok {
		return []byte(t), nil
	}
	return nil, fs.ErrNotExist
}

// aSafeProc is what a machine with nothing to say has in /proc: links protected, nothing on the runtimes'
// ports, one root filesystem.
func aSafeProc() map[string]string {
	return map[string]string{
		"/proc/sys/fs/protected_hardlinks": "1\n",
		"/proc/sys/fs/protected_symlinks":  "1\n",
		"/proc/net/tcp": "  sl  local_address rem_address   st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode\n" +
			"   0: 0100007F:1092 00000000:0000 0A 00000000:00000000 00:00000000 00000000     0        0 1 1\n",
		"/proc/mounts": "/dev/sda2 / ext4 rw,relatime 0 0\nproc /proc proc rw,nosuid 0 0\ntmpfs /tmp tmpfs rw,nosuid 0 0\n",
	}
}

func (m *agentMachine) readDir(path string) ([]fs.DirEntry, error) {
	names, ok := m.dirs[path]
	if !ok {
		return nil, fs.ErrNotExist
	}
	var out []fs.DirEntry
	for _, n := range names {
		out = append(out, fakeEntry(n))
	}
	return out, nil
}

type fakeEntry string

func (f fakeEntry) Name() string               { return string(f) }
func (f fakeEntry) IsDir() bool                { return false }
func (f fakeEntry) Type() fs.FileMode          { return 0 }
func (f fakeEntry) Info() (fs.FileInfo, error) { return nil, fs.ErrNotExist }

func (m *agentMachine) acl(path string) ([]ACLEntry, error) {
	if _, ok := m.files[path]; !ok {
		return nil, fs.ErrNotExist
	}
	return m.acls[path], nil
}

// walk is the walk for setuid programs on this machine: m.setuid found, then m.findErr.
func (m *agentMachine) walk(_ context.Context, p *SetuidProgress, _ func()) error {
	m.asked = append(m.asked, "walk "+strings.Join(p.Mounts, " "))
	if m.findArgs != nil {
		m.findArgs(p.Mounts)
	}
	for _, l := range strings.Split(m.setuid, "\n") {
		if l = strings.TrimSpace(l); l != "" {
			p.Found = append(p.Found, l)
		}
	}
	return m.findErr
}

func (m *agentMachine) run(_ context.Context, name string, args ...string) (string, error) {
	line := name + " " + strings.Join(args, " ")
	m.asked = append(m.asked, line)
	switch {
	case m.failsID && name == "id":
		return "", errors.New("id exited 1: no such user")
	case line == "id -u agent":
		return m.uid + "\n", nil
	case line == "id -nG agent":
		return m.groups + "\n", nil
	case line == "id -G agent":
		return m.gids + "\n", nil
	case line == "sudo -l -U agent":
		return m.sudo, m.sudoErr
	case name == "pacman" && len(args) >= 2 && args[0] == "-Qo":
		m.pacmanCalls++
		var out, errs []string
		for _, p := range args[1:] {
			if m.packaged[p] {
				out = append(out, p+" is owned by somepackage 1.0-1")
			} else {
				errs = append(errs, "error: No package owns "+p)
			}
		}
		said := strings.Join(out, "\n")
		if len(errs) > 0 {
			return said, errors.New("pacman exited 1: " + strings.Join(errs, "\n"))
		}
		return said, nil
	}
	return "", errors.New("not a command the judge may run: " + line)
}

func (m *agentMachine) stat(path string) (FileMode, error) {
	if f, ok := m.files[path]; ok {
		return f, nil
	}
	return FileMode{}, fs.ErrNotExist
}

const notAllowed = "User agent is not allowed to run sudo on box.\n"

var agent = Account{Module: "claude-code", ID: "claude-code.agent", Name: "agent", Root: true,
	Secrets: []string{"/var/lib/mesh/node-tools/broker"}}

func clean() *agentMachine {
	return &agentMachine{uid: "1600", groups: "agent", gids: "1600", sudo: notAllowed,
		files: map[string]FileMode{"/var/lib/mesh/node-tools/broker": {UID: 1500, GID: 1500, Perm: 0o600}},
		proc:  aSafeProc()}
}

func lookAgent(t *testing.T, m *agentMachine) Verdict {
	t.Helper()
	j := New(Exec{Run: m.run, Walk: m.walk, Stat: m.stat, ReadFile: m.readFile, ReadDir: m.readDir, ACL: m.acl})
	j.Set([]Account{agent})
	st, _ := j.Look(t.Context())
	if len(st.Accounts) != 1 {
		t.Fatalf("the statement: %+v", st)
	}
	for _, a := range m.asked {
		if !strings.HasPrefix(a, "id ") && a != "sudo -l -U agent" && !strings.HasPrefix(a, "walk /") &&
			!strings.HasPrefix(a, "pacman -Qo ") {
			t.Errorf("the judge asked something that is not a read: %q", a)
		}
	}
	return st.Accounts[0]
}

func TestAnAgentAccountWithNoWayToRootIsHealthyWithNobodyLoggedIn(t *testing.T) {
	if v := lookAgent(t, clean()); v.State != Healthy || v.Reason != "" || !v.Root {
		t.Fatalf("no way to root: %+v", v)
	}
}

func TestEachWayToRootIsSaid(t *testing.T) {
	for _, c := range []struct {
		name string
		set  func(*agentMachine)
		said string
	}{
		{"uid 0", func(m *agentMachine) { m.uid = "0" }, "its uid is 0"},
		{"docker", func(m *agentMachine) { m.groups = "agent docker" }, "in the group docker, which grants root"},
		{"wheel", func(m *agentMachine) { m.groups = "agent wheel" }, "in the group wheel, which grants root"},
		{"sudo", func(m *agentMachine) {
			m.sudo = "Matching Defaults entries for agent on box:\n    env_reset\n\nUser agent may run the following commands on box:\n    (ALL) NOPASSWD: ALL\n"
		}, "sudo grants it: (ALL) NOPASSWD: ALL"},
		{"secret by others", func(m *agentMachine) {
			m.files["/var/lib/mesh/node-tools/broker"] = FileMode{UID: 1500, GID: 1500, Perm: 0o644}
		}, "it can read the secret /var/lib/mesh/node-tools/broker"},
		{"secret by group", func(m *agentMachine) {
			m.gids = "1600 1500"
			m.files["/var/lib/mesh/node-tools/broker"] = FileMode{UID: 1500, GID: 1500, Perm: 0o640}
		}, "it can read the secret /var/lib/mesh/node-tools/broker"},
	} {
		t.Run(c.name, func(t *testing.T) {
			m := clean()
			c.set(m)
			v := lookAgent(t, m)
			if v.State != Unhealthy || !strings.HasPrefix(v.Reason, ReasonRoot+": ") || !strings.Contains(v.Reason, c.said) {
				t.Fatalf("want %q said: %+v", c.said, v)
			}
		})
	}
}

func TestEveryWayIsSaidAtOnce(t *testing.T) {
	m := clean()
	m.groups = "agent docker"
	m.sudo = "User agent may run the following commands on box:\n    (ALL) ALL\n"
	v := lookAgent(t, m)
	if !strings.Contains(v.Reason, "docker") || !strings.Contains(v.Reason, "(ALL) ALL") {
		t.Fatalf("both ways: %+v", v)
	}
}

func TestAnUnansweredQuestionIsUnknownNeverHealthy(t *testing.T) {
	m := clean()
	m.failsID = true
	if v := lookAgent(t, m); v.State != Unknown {
		t.Fatalf("an unread database: %+v", v)
	}
	m = clean()
	m.sudo = "something sudo never says\n"
	if v := lookAgent(t, m); v.State != Unknown {
		t.Fatalf("an unread sudo: %+v", v)
	}
}

func TestASecretNotThereYetIsNoWay(t *testing.T) {
	m := clean()
	delete(m.files, "/var/lib/mesh/node-tools/broker")
	if v := lookAgent(t, m); v.State != Healthy {
		t.Fatalf("no secret placed: %+v", v)
	}
}

func TestSudoRules(t *testing.T) {
	none := []struct {
		out string
		err error
	}{
		{notAllowed, nil},
		{notAllowed, errors.New("sudo exited 1: ")},
		{"", fmt.Errorf("sudo: %w", exec.ErrNotFound)},
	}
	for _, c := range none {
		if rules, err := SudoRules(c.out, c.err); err != nil || len(rules) != 0 {
			t.Errorf("%q, %v: rules %v, err %v", c.out, c.err, rules, err)
		}
	}
	rules, err := SudoRules("Matching Defaults entries for agent on box:\n    env_reset\n\nUser agent may run the following commands on box:\n    (ALL) /usr/bin/systemctl\n    (root) NOPASSWD: /usr/bin/true\n", nil)
	if err != nil || len(rules) != 2 || rules[0] != "(ALL) /usr/bin/systemctl" {
		t.Fatalf("two rules: %v, %v", rules, err)
	}
	if _, err := SudoRules("", errors.New("sudo exited 1: sudo: unable to resolve host")); err == nil {
		t.Error("a failing sudo that said neither was read as no rules")
	}
}

func TestReadable(t *testing.T) {
	m := FileMode{UID: 1500, GID: 1500, Perm: 0o600}
	if Readable(m, 1600, map[int]bool{1600: true}) || !Readable(m, 1500, nil) || !Readable(m, 0, nil) {
		t.Fatal("owner bits")
	}
}

func TestOfJudgesARootNeverAccountWithNoGroupsAndItsSecrets(t *testing.T) {
	d, err := declaration.ParseTrusted([]byte(`{"declaration":1,"resources":[
	  {"id":"claude-code.agent","type":"user","name":"agent","root":"never"},
	  {"id":"zsh.login","type":"user","name":"operator","shell":"/bin/zsh"},
	  {"id":"node-tools.need-broker","type":"file","path":"/var/lib/mesh/broker","sealed":"x","owner":"operator"},
	  {"id":"claude-code.own","type":"file","path":"/home/agent/own","sealed":"x","owner":"agent"},
	  {"id":"claude-code.plain","type":"file","path":"/etc/plain","content":"x"}
	]}`))
	if err != nil {
		t.Fatal(err)
	}
	got := Of(d, nil)
	if len(got) != 1 || got[0].ID != "claude-code.agent" || !got[0].Root ||
		len(got[0].Secrets) != 1 || got[0].Secrets[0] != "/var/lib/mesh/broker" {
		t.Fatalf("judged: %+v", got)
	}
}