HighHOST-FS-005Access ControlServer

Cron Files Writable by Non-Root Users

Checks that system cron files and directories are owned by root and not writable by others.

Why It Matters: Cron runs these jobs as root. Anyone who can edit them can run any command as root at the next scheduled minute.
How It Detects: Stats /etc/crontab, /etc/cron.d and its files, and the cron.hourly/daily/weekly/monthly directories, flagging non-root owners or group/other write bits.
How to Fix: chown root:root <path> && chmod go-w <path> for each listed path (600 for /etc/crontab is a common hardening choice).
How to Verify: stat -c '%a %U %n' /etc/crontab /etc/cron.*
CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Control Category: Access Control: CIS Controls v8 3, 6; NIST CSF 2.0 PR.AA, PR.DS
Fix Effort: Low
CIS Controls v8 Safeguard: 3.3
NIST CSF 2.0 Subcategory: PR.AA-05, PR.DS-01
CWE: CWE-732
NIST SP 800-53 Rev. 5: AC-3, CM-6
Benchmark Topic: Job schedulers: cron permissions (topic only, no benchmark text)
References: crontab(5), Linux man-pages
MITRE ATT&CK T1053.003, Cron

Learn the theory behind this check: P1 Linux Server Hardening.

Source Code

The complete file that defines this check. Run it with openvapt scan --only HOST-FS-005, or read it offline with openvapt explain HOST-FS-005.

internal/checks/host/files.go · Lines 1-244View on GitHub at This Commit

1package host
2
3import (
"context"
"fmt"
"io/fs"
"sort"
8
"github.com/openvapt/openvapt/internal/check"
"github.com/openvapt/openvapt/internal/sys"
11)
12
13func perm(m fs.FileMode) string { return fmt.Sprintf("%04o", uint32(m.Perm())|specialBits(m)) }
14
15func specialBits(m fs.FileMode) uint32 {
var b uint32
if m&fs.ModeSetuid != 0 {
b |= 0o4000
}
if m&fs.ModeSetgid != 0 {
b |= 0o2000
}
if m&fs.ModeSticky != 0 {
b |= 0o1000
}
return b
27}
28
29func init() {
check.Register(&check.Check{
ID:        "HOST-FS-001",
Title:     "Sensitive Account Files Have Unsafe Permissions",
Domain:    check.DomainHost,
Severity:  check.High,
CVSS:      "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N",
Summary:   "Checks that /etc/shadow and /etc/gshadow are not readable by others, and /etc/passwd and /etc/group are not writable by others.",
Rationale: "Readable shadow files let any local user (or a compromised web app) copy password hashes and crack them offline. Writable passwd/group files let them create a root account.",
Detection: "Stats each file without reading its contents and inspects the permission bits for 'other' and 'group' access.",
Fix:       "chown root:root /etc/passwd /etc/group && chmod 644 /etc/passwd /etc/group ; chown root:shadow /etc/shadow /etc/gshadow && chmod 640 /etc/shadow /etc/gshadow  (use root:root and 000 on RHEL-family systems).",
Verify:    "stat -c '%a %U:%G %n' /etc/passwd /etc/group /etc/shadow /etc/gshadow",
Refs:      []check.Ref{{Title: "shadow(5), Linux man-pages", URL: "https://man7.org/linux/man-pages/man5/shadow.5.html"}, refNIST800123},
Standards: check.Standards{CWE: []string{"CWE-732"}, NIST: []string{"AC-3", "AC-6"}, CISTopic: "File permissions: account database files"},
Run: func(_ context.Context, s sys.System) []check.Result {
	var out []check.Result
	for _, f := range []struct {
		path string
		bad  fs.FileMode
		why  string
	}{
		{"/etc/shadow", 0o004 | 0o002, "readable or writable by others"},
		{"/etc/gshadow", 0o004 | 0o002, "readable or writable by others"},
		{"/etc/passwd", 0o022, "writable by group or others"},
		{"/etc/group", 0o022, "writable by group or others"},
	} {
		st, err := s.Stat(f.path)
		if err != nil {
			continue
		}
		if st.Mode.Perm()&f.bad != 0 {
			out = append(out, check.FailR(f.path, f.path+" is "+f.why, "mode "+perm(st.Mode)))
		} else {
			out = append(out, check.PassR(f.path, f.path+" permissions are safe", "mode "+perm(st.Mode)))
		}
	}
	if len(out) == 0 {
		return []check.Result{check.SkipR("/etc", "Account files not found")}
	}
	return out
},
})
71
check.Register(&check.Check{
ID:        "HOST-FS-002",
Title:     "Temporary Directory Missing the Sticky Bit",
Domain:    check.DomainHost,
Severity:  check.High,
CVSS:      "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
Summary:   "Checks that world-writable temp directories have the sticky bit set.",
Rationale: "Without the sticky bit any user can delete or replace other users' files in /tmp, enabling symlink attacks against root-run scripts.",
Detection: "Stats /tmp and /var/tmp; world-writable without the sticky bit (mode 1777 expected) fails.",
Fix:       "chmod 1777 /tmp /var/tmp",
Verify:    "stat -c '%a %n' /tmp /var/tmp  should print 1777 for both.",
Refs:      []check.Ref{{Title: "chmod(1), Linux man-pages (restricted deletion flag)", URL: "https://man7.org/linux/man-pages/man1/chmod.1.html"}},
Standards: check.Standards{CWE: []string{"CWE-377", "CWE-732"}, NIST: []string{"AC-3"}, CISTopic: "Filesystem: sticky bit on world-writable directories"},
Run: func(_ context.Context, s sys.System) []check.Result {
	var out []check.Result
	for _, d := range []string{"/tmp", "/var/tmp"} {
		st, err := s.Stat(d)
		if err != nil {
			continue
		}
		if st.Mode.Perm()&0o002 != 0 && st.Mode&fs.ModeSticky == 0 {
			out = append(out, check.FailR(d, d+" is world-writable without the sticky bit", "mode "+perm(st.Mode)))
		} else {
			out = append(out, check.PassR(d, d+" is protected", "mode "+perm(st.Mode)))
		}
	}
	return out
},
})
101
check.Register(&check.Check{
ID:        "HOST-FS-003",
Title:     "World-Writable Files in System Configuration",
Domain:    check.DomainHost,
Severity:  check.High,
CVSS:      "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
Summary:   "Looks for files under /etc and in cron directories that any user can modify.",
Rationale: "A world-writable config or cron file lets any local user change how a root-owned service behaves, often leading straight to root.",
Detection: "Walks /etc (metadata only, up to 20000 files, symlinks not followed) and lists regular files with the 'other write' bit set, plus directories up to three levels deep that are world-writable without the sticky bit (anyone could replace files inside them).",
Fix:       "For each listed file or directory: chmod o-w <path>. Then find out how it became writable (a deployment script or a careless chmod 777).",
Verify:    "find /etc -xdev \\( -type f -perm -0002 \\) -o \\( -type d -perm -0002 ! -perm -1000 \\)  should print nothing.",
Refs:      []check.Ref{refNIST800123},
Standards: check.Standards{CWE: []string{"CWE-732"}, NIST: []string{"AC-3", "CM-6"}, CISTopic: "File permissions: no world-writable files"},
Run: func(ctx context.Context, s sys.System) []check.Result {
	walk, err := s.Walk(ctx, "/etc", 20000)
	files := walk.Files
	if err != nil && len(files) == 0 {
		return []check.Result{check.ErrR("/etc", err)}
	}
	var bad []string
	for _, f := range files {
		if f.Mode.Perm()&0o002 != 0 {
			bad = append(bad, perm(f.Mode)+" "+f.Path)
		}
	}
	bad = append(bad, worldWritableDirs(s, "/etc", 3, 5000)...)
	if len(bad) > 0 {
		if len(bad) > 25 {
			bad = append(bad[:25], fmt.Sprintf("... and %d more", len(bad)-25))
		}
		return []check.Result{check.FailR("/etc", "World-writable files found", bad...)}
	}
	if !walk.Complete {
		return []check.Result{check.IncompleteR("/etc", fmt.Sprintf("Filesystem walk was partial after %d files", len(files)))}
	}
	return []check.Result{check.PassR("/etc", fmt.Sprintf("No world-writable files among %d checked", len(files)))}
},
})
140
check.Register(&check.Check{
ID:        "HOST-FS-004",
Title:     "Unexpected SUID or SGID Programs",
Domain:    check.DomainHost,
Severity:  check.High,
CVSS:      "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
Summary:   "Looks for set-user-ID or set-group-ID programs in places where packages do not normally install them.",
Rationale: "A SUID program runs with its owner's rights (usually root). One placed in /tmp, /home, /var/www or /opt is a common persistence and privilege-escalation trick.",
Detection: "Walks /tmp, /var/tmp, /dev/shm, /home, /var/www, /srv, /opt and /usr/local (metadata only) and lists files with the SUID or SGID bit.",
Fix:       "Confirm whether each program is needed. Remove the bit with chmod u-s,g-s <file>, or delete the file if you did not put it there and investigate how it arrived.",
Verify:    "find /tmp /home /var/www /opt /usr/local -xdev -perm /6000 -type f  should print nothing unexpected.",
Refs:      []check.Ref{{Title: "MITRE ATT&CK T1548.001, Setuid and Setgid", URL: "https://attack.mitre.org/techniques/T1548/001/"}},
Standards: check.Standards{CWE: []string{"CWE-250"}, NIST: []string{"CM-7", "AC-6"}, CISTopic: "Filesystem: audit SUID and SGID executables"},
Run: func(ctx context.Context, s sys.System) []check.Result {
	var bad []string
	complete := true
	for _, root := range []string{"/tmp", "/var/tmp", "/dev/shm", "/home", "/var/www", "/srv", "/opt", "/usr/local"} {
		walk, err := s.Walk(ctx, root, 20000)
		if err != nil || !walk.Complete {
			complete = false
		}
		for _, f := range walk.Files {
			if f.Mode&(fs.ModeSetuid|fs.ModeSetgid) != 0 {
				bad = append(bad, perm(f.Mode)+" "+f.Path)
			}
		}
	}
	if len(bad) > 0 {
		return []check.Result{check.FailR("filesystem", "SUID/SGID programs outside standard system paths", bad...)}
	}
	if !complete {
		return []check.Result{check.IncompleteR("filesystem", "One or more filesystem walks were partial or unreadable")}
	}
	return []check.Result{check.PassR("filesystem", "No SUID/SGID programs in unusual locations")}
},
})
177
check.Register(&check.Check{
ID:        "HOST-FS-005",
Title:     "Cron Files Writable by Non-Root Users",
Domain:    check.DomainHost,
Severity:  check.High,
CVSS:      "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
Summary:   "Checks that system cron files and directories are owned by root and not writable by others.",
Rationale: "Cron runs these jobs as root. Anyone who can edit them can run any command as root at the next scheduled minute.",
Detection: "Stats /etc/crontab, /etc/cron.d and its files, and the cron.hourly/daily/weekly/monthly directories, flagging non-root owners or group/other write bits.",
Fix:       "chown root:root <path> && chmod go-w <path>  for each listed path (600 for /etc/crontab is a common hardening choice).",
Verify:    "stat -c '%a %U %n' /etc/crontab /etc/cron.*",
Refs:      []check.Ref{{Title: "crontab(5), Linux man-pages", URL: "https://man7.org/linux/man-pages/man5/crontab.5.html"}, {Title: "MITRE ATT&CK T1053.003, Cron", URL: "https://attack.mitre.org/techniques/T1053/003/"}},
Standards: check.Standards{CWE: []string{"CWE-732"}, NIST: []string{"AC-3", "CM-6"}, CISTopic: "Job schedulers: cron permissions"},
Run: func(_ context.Context, s sys.System) []check.Result {
	paths := []string{"/etc/crontab", "/etc/cron.d", "/etc/cron.hourly", "/etc/cron.daily", "/etc/cron.weekly", "/etc/cron.monthly"}
	more, _ := s.Glob("/etc/cron.d/*")
	paths = append(paths, more...)
	var bad []string
	seen := 0
	for _, p := range paths {
		st, err := s.Stat(p)
		if err != nil {
			continue
		}
		seen++
		if (st.UID > 0) || st.Mode.Perm()&0o022 != 0 {
			bad = append(bad, fmt.Sprintf("%s uid=%d %s", perm(st.Mode), st.UID, p))
		}
	}
	if seen == 0 {
		return []check.Result{check.SkipR("cron", "No system cron files found")}
	}
	if len(bad) > 0 {
		return []check.Result{check.FailR("cron", "Cron paths can be modified by non-root users", bad...)}
	}
	return []check.Result{check.PassR("cron", "Cron files are root-owned and not group/other writable")}
},
})
216}
217
218// worldWritableDirs lists directories under root, up to depth levels, that
219// are writable by others and lack the sticky bit. Stat does not follow
220// symlinks, so a symlink is never reported as a directory.
221func worldWritableDirs(s sys.System, root string, depth, limit int) []string {
var bad []string
pat := root
seen := 0
for d := 0; d < depth; d++ {
pat += "/*"
paths, _ := s.Glob(pat)
sort.Strings(paths)
for _, p := range paths {
	if seen >= limit {
		return bad
	}
	st, err := s.Stat(p)
	if err != nil || !st.IsDir {
		continue
	}
	seen++
	if st.Mode.Perm()&0o002 != 0 && st.Mode&fs.ModeSticky == 0 {
		bad = append(bad, perm(st.Mode)+" "+p+"/ (directory, no sticky bit)")
	}
}
}
return bad
244}

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APA 7

OpenVAPT. (2026). HOST-FS-005 Cron Files Writable by Non-Root Users (Version 0.1.0-alpha.6). OpenVAPT Check Catalogue. Retrieved October 16, 2026, from https://openvapt.com/checks/HOST-FS-005.html

In text: (OpenVAPT, 2026). Accessed: the date shown is today's date from your own browser (the site's build date without JavaScript); change it to the day you read the page.

BibTeX

@misc{openvapt_host_fs_005,
  author       = {{OpenVAPT}},
  title        = {{HOST-FS-005 Cron Files Writable by Non-Root Users}},
  year         = {2026},
  howpublished = {\url{https://openvapt.com/checks/HOST-FS-005.html}},
  note         = {OpenVAPT Check Catalogue, version 0.1.0-alpha.6. Accessed 16 October 2026}
}

Accessed: the date shown is today's date from your own browser (the site's build date without JavaScript); change it to the day you read the page.

Citing OpenVAPT does not mean OpenVAPT endorses, approves or has reviewed your work.

Cite This Work: OpenVAPT. (2026). OpenVAPT: An open academic vulnerability assessment tool (Version 0.1.0-alpha.6) [Computer software]. https://github.com/OpenVAPT/openvapt

1	package host
2
3	import (
4	"context"
5	"fmt"
6	"io/fs"
7	"sort"
8
9	"github.com/openvapt/openvapt/internal/check"
10	"github.com/openvapt/openvapt/internal/sys"
11	)
12
13	func perm(m fs.FileMode) string { return fmt.Sprintf("%04o", uint32(m.Perm())\|specialBits(m)) }
14
15	func specialBits(m fs.FileMode) uint32 {
16	var b uint32
17	if m&fs.ModeSetuid != 0 {
18	b \|= 0o4000
19	}
20	if m&fs.ModeSetgid != 0 {
21	b \|= 0o2000
22	}
23	if m&fs.ModeSticky != 0 {
24	b \|= 0o1000
25	}
26	return b
27	}
28
29	func init() {
30	check.Register(&check.Check{
31	ID: "HOST-FS-001",
32	Title: "Sensitive Account Files Have Unsafe Permissions",
33	Domain: check.DomainHost,
34	Severity: check.High,
35	CVSS: "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N",
36	Summary: "Checks that /etc/shadow and /etc/gshadow are not readable by others, and /etc/passwd and /etc/group are not writable by others.",
37	Rationale: "Readable shadow files let any local user (or a compromised web app) copy password hashes and crack them offline. Writable passwd/group files let them create a root account.",
38	Detection: "Stats each file without reading its contents and inspects the permission bits for 'other' and 'group' access.",
39	Fix: "chown root:root /etc/passwd /etc/group && chmod 644 /etc/passwd /etc/group ; chown root:shadow /etc/shadow /etc/gshadow && chmod 640 /etc/shadow /etc/gshadow (use root:root and 000 on RHEL-family systems).",
40	Verify: "stat -c '%a %U:%G %n' /etc/passwd /etc/group /etc/shadow /etc/gshadow",
41	Refs: []check.Ref{{Title: "shadow(5), Linux man-pages", URL: "https://man7.org/linux/man-pages/man5/shadow.5.html"}, refNIST800123},
42	Standards: check.Standards{CWE: []string{"CWE-732"}, NIST: []string{"AC-3", "AC-6"}, CISTopic: "File permissions: account database files"},
43	Run: func(_ context.Context, s sys.System) []check.Result {
44	var out []check.Result
45	for _, f := range []struct {
46	path string
47	bad fs.FileMode
48	why string
49	}{
50	{"/etc/shadow", 0o004 \| 0o002, "readable or writable by others"},
51	{"/etc/gshadow", 0o004 \| 0o002, "readable or writable by others"},
52	{"/etc/passwd", 0o022, "writable by group or others"},
53	{"/etc/group", 0o022, "writable by group or others"},
54	} {
55	st, err := s.Stat(f.path)
56	if err != nil {
57	continue
58	}
59	if st.Mode.Perm()&f.bad != 0 {
60	out = append(out, check.FailR(f.path, f.path+" is "+f.why, "mode "+perm(st.Mode)))
61	} else {
62	out = append(out, check.PassR(f.path, f.path+" permissions are safe", "mode "+perm(st.Mode)))
63	}
64	}
65	if len(out) == 0 {
66	return []check.Result{check.SkipR("/etc", "Account files not found")}
67	}
68	return out
69	},
70	})
71
72	check.Register(&check.Check{
73	ID: "HOST-FS-002",
74	Title: "Temporary Directory Missing the Sticky Bit",
75	Domain: check.DomainHost,
76	Severity: check.High,
77	CVSS: "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
78	Summary: "Checks that world-writable temp directories have the sticky bit set.",
79	Rationale: "Without the sticky bit any user can delete or replace other users' files in /tmp, enabling symlink attacks against root-run scripts.",
80	Detection: "Stats /tmp and /var/tmp; world-writable without the sticky bit (mode 1777 expected) fails.",
81	Fix: "chmod 1777 /tmp /var/tmp",
82	Verify: "stat -c '%a %n' /tmp /var/tmp should print 1777 for both.",
83	Refs: []check.Ref{{Title: "chmod(1), Linux man-pages (restricted deletion flag)", URL: "https://man7.org/linux/man-pages/man1/chmod.1.html"}},
84	Standards: check.Standards{CWE: []string{"CWE-377", "CWE-732"}, NIST: []string{"AC-3"}, CISTopic: "Filesystem: sticky bit on world-writable directories"},
85	Run: func(_ context.Context, s sys.System) []check.Result {
86	var out []check.Result
87	for _, d := range []string{"/tmp", "/var/tmp"} {
88	st, err := s.Stat(d)
89	if err != nil {
90	continue
91	}
92	if st.Mode.Perm()&0o002 != 0 && st.Mode&fs.ModeSticky == 0 {
93	out = append(out, check.FailR(d, d+" is world-writable without the sticky bit", "mode "+perm(st.Mode)))
94	} else {
95	out = append(out, check.PassR(d, d+" is protected", "mode "+perm(st.Mode)))
96	}
97	}
98	return out
99	},
100	})
101
102	check.Register(&check.Check{
103	ID: "HOST-FS-003",
104	Title: "World-Writable Files in System Configuration",
105	Domain: check.DomainHost,
106	Severity: check.High,
107	CVSS: "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
108	Summary: "Looks for files under /etc and in cron directories that any user can modify.",
109	Rationale: "A world-writable config or cron file lets any local user change how a root-owned service behaves, often leading straight to root.",
110	Detection: "Walks /etc (metadata only, up to 20000 files, symlinks not followed) and lists regular files with the 'other write' bit set, plus directories up to three levels deep that are world-writable without the sticky bit (anyone could replace files inside them).",
111	Fix: "For each listed file or directory: chmod o-w <path>. Then find out how it became writable (a deployment script or a careless chmod 777).",
112	Verify: "find /etc -xdev \\( -type f -perm -0002 \\) -o \\( -type d -perm -0002 ! -perm -1000 \\) should print nothing.",
113	Refs: []check.Ref{refNIST800123},
114	Standards: check.Standards{CWE: []string{"CWE-732"}, NIST: []string{"AC-3", "CM-6"}, CISTopic: "File permissions: no world-writable files"},
115	Run: func(ctx context.Context, s sys.System) []check.Result {
116	walk, err := s.Walk(ctx, "/etc", 20000)
117	files := walk.Files
118	if err != nil && len(files) == 0 {
119	return []check.Result{check.ErrR("/etc", err)}
120	}
121	var bad []string
122	for _, f := range files {
123	if f.Mode.Perm()&0o002 != 0 {
124	bad = append(bad, perm(f.Mode)+" "+f.Path)
125	}
126	}
127	bad = append(bad, worldWritableDirs(s, "/etc", 3, 5000)...)
128	if len(bad) > 0 {
129	if len(bad) > 25 {
130	bad = append(bad[:25], fmt.Sprintf("... and %d more", len(bad)-25))
131	}
132	return []check.Result{check.FailR("/etc", "World-writable files found", bad...)}
133	}
134	if !walk.Complete {
135	return []check.Result{check.IncompleteR("/etc", fmt.Sprintf("Filesystem walk was partial after %d files", len(files)))}
136	}
137	return []check.Result{check.PassR("/etc", fmt.Sprintf("No world-writable files among %d checked", len(files)))}
138	},
139	})
140
141	check.Register(&check.Check{
142	ID: "HOST-FS-004",
143	Title: "Unexpected SUID or SGID Programs",
144	Domain: check.DomainHost,
145	Severity: check.High,
146	CVSS: "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
147	Summary: "Looks for set-user-ID or set-group-ID programs in places where packages do not normally install them.",
148	Rationale: "A SUID program runs with its owner's rights (usually root). One placed in /tmp, /home, /var/www or /opt is a common persistence and privilege-escalation trick.",
149	Detection: "Walks /tmp, /var/tmp, /dev/shm, /home, /var/www, /srv, /opt and /usr/local (metadata only) and lists files with the SUID or SGID bit.",
150	Fix: "Confirm whether each program is needed. Remove the bit with chmod u-s,g-s <file>, or delete the file if you did not put it there and investigate how it arrived.",
151	Verify: "find /tmp /home /var/www /opt /usr/local -xdev -perm /6000 -type f should print nothing unexpected.",
152	Refs: []check.Ref{{Title: "MITRE ATT&CK T1548.001, Setuid and Setgid", URL: "https://attack.mitre.org/techniques/T1548/001/"}},
153	Standards: check.Standards{CWE: []string{"CWE-250"}, NIST: []string{"CM-7", "AC-6"}, CISTopic: "Filesystem: audit SUID and SGID executables"},
154	Run: func(ctx context.Context, s sys.System) []check.Result {
155	var bad []string
156	complete := true
157	for _, root := range []string{"/tmp", "/var/tmp", "/dev/shm", "/home", "/var/www", "/srv", "/opt", "/usr/local"} {
158	walk, err := s.Walk(ctx, root, 20000)
159	if err != nil \|\| !walk.Complete {
160	complete = false
161	}
162	for _, f := range walk.Files {
163	if f.Mode&(fs.ModeSetuid\|fs.ModeSetgid) != 0 {
164	bad = append(bad, perm(f.Mode)+" "+f.Path)
165	}
166	}
167	}
168	if len(bad) > 0 {
169	return []check.Result{check.FailR("filesystem", "SUID/SGID programs outside standard system paths", bad...)}
170	}
171	if !complete {
172	return []check.Result{check.IncompleteR("filesystem", "One or more filesystem walks were partial or unreadable")}
173	}
174	return []check.Result{check.PassR("filesystem", "No SUID/SGID programs in unusual locations")}
175	},
176	})
177
178	check.Register(&check.Check{
179	ID: "HOST-FS-005",
180	Title: "Cron Files Writable by Non-Root Users",
181	Domain: check.DomainHost,
182	Severity: check.High,
183	CVSS: "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
184	Summary: "Checks that system cron files and directories are owned by root and not writable by others.",
185	Rationale: "Cron runs these jobs as root. Anyone who can edit them can run any command as root at the next scheduled minute.",
186	Detection: "Stats /etc/crontab, /etc/cron.d and its files, and the cron.hourly/daily/weekly/monthly directories, flagging non-root owners or group/other write bits.",
187	Fix: "chown root:root <path> && chmod go-w <path> for each listed path (600 for /etc/crontab is a common hardening choice).",
188	Verify: "stat -c '%a %U %n' /etc/crontab /etc/cron.*",
189	Refs: []check.Ref{{Title: "crontab(5), Linux man-pages", URL: "https://man7.org/linux/man-pages/man5/crontab.5.html"}, {Title: "MITRE ATT&CK T1053.003, Cron", URL: "https://attack.mitre.org/techniques/T1053/003/"}},
190	Standards: check.Standards{CWE: []string{"CWE-732"}, NIST: []string{"AC-3", "CM-6"}, CISTopic: "Job schedulers: cron permissions"},
191	Run: func(_ context.Context, s sys.System) []check.Result {
192	paths := []string{"/etc/crontab", "/etc/cron.d", "/etc/cron.hourly", "/etc/cron.daily", "/etc/cron.weekly", "/etc/cron.monthly"}
193	more, _ := s.Glob("/etc/cron.d/*")
194	paths = append(paths, more...)
195	var bad []string
196	seen := 0
197	for _, p := range paths {
198	st, err := s.Stat(p)
199	if err != nil {
200	continue
201	}
202	seen++
203	if (st.UID > 0) \|\| st.Mode.Perm()&0o022 != 0 {
204	bad = append(bad, fmt.Sprintf("%s uid=%d %s", perm(st.Mode), st.UID, p))
205	}
206	}
207	if seen == 0 {
208	return []check.Result{check.SkipR("cron", "No system cron files found")}
209	}
210	if len(bad) > 0 {
211	return []check.Result{check.FailR("cron", "Cron paths can be modified by non-root users", bad...)}
212	}
213	return []check.Result{check.PassR("cron", "Cron files are root-owned and not group/other writable")}
214	},
215	})
216	}
217
218	// worldWritableDirs lists directories under root, up to depth levels, that
219	// are writable by others and lack the sticky bit. Stat does not follow
220	// symlinks, so a symlink is never reported as a directory.
221	func worldWritableDirs(s sys.System, root string, depth, limit int) []string {
222	var bad []string
223	pat := root
224	seen := 0
225	for d := 0; d < depth; d++ {
226	pat += "/*"
227	paths, _ := s.Glob(pat)
228	sort.Strings(paths)
229	for _, p := range paths {
230	if seen >= limit {
231	return bad
232	}
233	st, err := s.Stat(p)
234	if err != nil \|\| !st.IsDir {
235	continue
236	}
237	seen++
238	if st.Mode.Perm()&0o002 != 0 && st.Mode&fs.ModeSticky == 0 {
239	bad = append(bad, perm(st.Mode)+" "+p+"/ (directory, no sticky bit)")
240	}
241	}
242	}
243	return bad
244	}