HighNET-DB-012Data ServicesNetwork

Postfix Open Relay Controls

Postfix relay restrictions are missing or mynetworks trusts overly broad ranges.

Why It Matters: An open relay enables spam and phishing, damages domain reputation, and can expose the host to blocklisting.
How It Detects: Parses main.cf for smtpd_relay_restrictions with reject_unauth_destination and flags 0.0.0.0/0 or ::/0 in mynetworks.
How to Fix: Set smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination and narrow mynetworks.
How to Verify: Run postconf -n during approved administration and perform only an authorized relay test.
CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L
Control Category: Data Services: CIS Controls v8 3, 4, 12; NIST CSF 2.0 PR.DS, PR.PS
Fix Effort: Low
CIS Controls v8 Safeguard: 4.1
NIST CSF 2.0 Subcategory: PR.PS-01
CWE: CWE-441
OWASP Top 10: A05:2021
NIST SP 800-53 Rev. 5: AC-3, CM-6, SC-7
Benchmark Topic: Secure data service configuration (topic only, no benchmark text)
References: Postfix SMTP Relay and Access Control

Learn the theory behind this check: P3 Network Exposure and Firewalls, P8 Data Services: Databases, File Shares, DNS and Mail.

Source Code

The complete file that defines this check. Run it with openvapt scan --only NET-DB-012, or read it offline with openvapt explain NET-DB-012.

internal/checks/network/services.go · Lines 1-198View on GitHub at This Commit

1package network
2
3import (
"bufio"
"context"
"strings"
7
"github.com/openvapt/openvapt/internal/check"
"github.com/openvapt/openvapt/internal/checks/collect"
"github.com/openvapt/openvapt/internal/sys"
11)
12
13func readAny(ctx context.Context, s sys.System, paths ...string) (string, string, bool, bool) {
var found []string
var text strings.Builder
complete := true
for _, p := range paths {
r, err := s.ReadFile(ctx, p)
if err == nil {
	found = append(found, p)
	text.Write(r.Data)
	text.WriteByte('\n')
	complete = complete && r.Complete
}
}
if len(found) == 0 {
return "", "", false, false
}
return strings.Join(found, ", "), text.String(), complete, true
30}
31func simpleFileCheck(id, title string, sev check.Severity, cat check.Category, summary, rationale, detection, fix, verify, cvss string, paths []string, ref check.Ref, bad func(string) []string) {
check.Register(&check.Check{
ID: id, Title: title, Domain: check.DomainNetwork, Severity: sev, Category: cat, Effort: check.EffortLow, CVSS: cvss, Summary: summary, Rationale: rationale, Detection: detection, Fix: fix, Verify: verify, Refs: []check.Ref{ref}, Standards: dataStandards(id), Run: func(ctx context.Context, s sys.System) []check.Result {
	p, text, complete, ok := readAny(ctx, s, paths...)
	if !ok {
		return []check.Result{check.SkipR(strings.Join(paths, ", "), "Configuration was not found")}
	}
	ev := bad(text)
	if len(ev) > 0 {
		return []check.Result{check.FailR(p, summary, ev...)}
	}
	if !complete {
		return []check.Result{check.IncompleteR(p, "Configuration input was truncated")}
	}
	return []check.Result{check.PassR(p, "No unsafe setting was found")}
}})
47}
48
49func init() {
simpleFileCheck("NET-DB-008", "Unsafe NFS Export Options", check.High, check.CatData, "NFS exports are world-accessible or use no_root_squash or insecure.", "These export options can grant untrusted clients filesystem access or preserve remote root privileges.", "Reads /etc/exports and active exports.d fragments, ignoring comments, and flags *, no_root_squash, and insecure.", "Restrict every export to explicit client CIDRs, use root_squash, remove insecure, and reload exports.", "Run exportfs -v during approved administration and confirm only intended networks and safe options appear.", "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H", []string{"/etc/exports"}, check.Ref{Title: "Linux exports(5)", URL: "https://man7.org/linux/man-pages/man5/exports.5.html"}, func(t string) []string { return matchingLines(t, "*", "no_root_squash", "insecure") })
simpleFileCheck("NET-DB-009", "Unsafe Samba Guest or SMB1 Configuration", check.High, check.CatData, "Samba permits guest access, maps unknown users to guest, or allows SMB1.", "Guest shares weaken accountability, while SMB1 lacks modern protocol protections and has a long history of severe flaws.", "Reads smb.conf and flags guest ok = yes, permissive map to guest modes, or a server min protocol below SMB2.", "Set guest ok = no, map to guest = Never, and server min protocol = SMB2_02 or newer. Review each share ACL.", "Run testparm -s during approved administration and confirm the effective values.", "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H", []string{"/etc/samba/smb.conf"}, check.Ref{Title: "Samba smb.conf Manual", URL: "https://www.samba.org/samba/docs/current/man-html/smb.conf.5.html"}, func(t string) []string {
l := strings.ToLower(t)
var e []string
if strings.Contains(l, "guest ok = yes") || strings.Contains(l, "guest ok=yes") {
	e = append(e, "guest ok enabled")
}
if strings.Contains(l, "map to guest = bad") || strings.Contains(l, "map to guest=bad") {
	e = append(e, "unknown users map to guest")
}
if strings.Contains(l, "server min protocol = nt1") || strings.Contains(l, "server min protocol=nt1") {
	e = append(e, "SMB1 NT1 enabled")
}
return e
})
simpleFileCheck("NET-DB-010", "BIND Open Recursion", check.High, check.CatData, "BIND enables recursion without restricting recursive clients.", "An open recursive resolver can be abused for reflection attacks and permits outsiders to consume resolver resources.", "Reads named.conf and flags recursion yes when neither allow-recursion nor allow-query-cache restricts clients.", "Disable recursion on authoritative-only servers, or set allow-recursion and allow-query-cache to explicit trusted networks.", "Run named-checkconf and query recursion from an untrusted test network under an approved test plan.", "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H", []string{"/etc/bind/named.conf.options", "/etc/named.conf"}, check.Ref{Title: "BIND 9 Administrator Reference Manual - Access Control", URL: "https://bind9.readthedocs.io/en/latest/reference.html#access-control"}, func(t string) []string {
l := strings.ToLower(t)
if strings.Contains(l, "recursion yes") && !strings.Contains(l, "allow-recursion") && !strings.Contains(l, "allow-query-cache") {
	return []string{"recursion yes without a client ACL"}
}
return nil
})
simpleFileCheck("NET-DB-011", "BIND Zone Transfers Allowed to Any", check.High, check.CatData, "BIND permits zone transfers to any client.", "Unrestricted transfers disclose the complete DNS namespace and provide attackers with a detailed target inventory.", "Reads named.conf and flags allow-transfer clauses containing any.", "Set allow-transfer to none or explicit secondary server addresses, preferably protected with TSIG.", "Run named-checkconf and verify AXFR is refused from an unauthorized test host.", "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N", []string{"/etc/bind/named.conf.options", "/etc/named.conf"}, check.Ref{Title: "BIND 9 Administrator Reference Manual - allow-transfer", URL: "https://bind9.readthedocs.io/en/latest/reference.html#namedconf-statement-allow-transfer"}, func(t string) []string {
l := strings.ToLower(t)
if strings.Contains(l, "allow-transfer") && strings.Contains(l, "any;") {
	return []string{"allow-transfer includes any"}
}
return nil
})
registerMailChecks()
registerExposureChecks()
81}
82
83func registerMailChecks() {
simpleFileCheck("NET-DB-012", "Postfix Open Relay Controls", check.High, check.CatData, "Postfix relay restrictions are missing or mynetworks trusts overly broad ranges.", "An open relay enables spam and phishing, damages domain reputation, and can expose the host to blocklisting.", "Parses main.cf for smtpd_relay_restrictions with reject_unauth_destination and flags 0.0.0.0/0 or ::/0 in mynetworks.", "Set smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination and narrow mynetworks.", "Run postconf -n during approved administration and perform only an authorized relay test.", "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L", []string{"/etc/postfix/main.cf"}, check.Ref{Title: "Postfix SMTP Relay and Access Control", URL: "https://www.postfix.org/SMTPD_ACCESS_README.html"}, func(t string) []string {
m := collect.ParseKV(t)
relay := strings.ToLower(strings.Join(m["smtpd_relay_restrictions"], " "))
nets := strings.ToLower(strings.Join(m["mynetworks"], " "))
var e []string
if !strings.Contains(relay, "reject_unauth_destination") {
	e = append(e, "reject_unauth_destination missing")
}
if strings.Contains(nets, "0.0.0.0/0") || strings.Contains(nets, "::/0") {
	e = append(e, "mynetworks trusts all addresses")
}
return e
})
simpleFileCheck("NET-DB-013", "Mail Cleartext Authentication Allowed", check.Medium, check.CatCrypto, "Postfix or Dovecot permits plaintext authentication without requiring TLS.", "Credentials sent before transport encryption can be observed by any party able to intercept the connection.", "Reads Postfix smtpd_tls_auth_only and Dovecot disable_plaintext_auth, and flags no values.", "Set smtpd_tls_auth_only = yes and disable_plaintext_auth = yes. Use implicit TLS on ports 465, 993, and 995. STARTTLS assessment is out of scope.", "Confirm the effective mail configuration and that unauthenticated plaintext sessions do not advertise AUTH.", "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N", []string{"/etc/postfix/main.cf", "/etc/dovecot/conf.d/10-auth.conf"}, check.Ref{Title: "Dovecot Authentication Settings", URL: "https://doc.dovecot.org/main/core/config/auth/settings.html"}, func(t string) []string {
m := collect.ParseKV(t)
var e []string
for _, k := range []string{"smtpd_tls_auth_only", "disable_plaintext_auth"} {
	for _, v := range m[k] {
		if strings.EqualFold(strings.TrimSpace(v), "no") {
			e = append(e, k+" is no")
		}
	}
}
return e
})
109}
110
111// controlPorts are control planes and remote desktops: reaching one of them
112// from the network means administrative control of the host or cluster
113// (vendor documentation and the IANA registry). SNMP is not here: it is a
114// cleartext protocol and belongs to NET-SVC-001 only, so one socket never
115// yields more than one finding per check family.
116var controlPorts = map[int]string{2375: "Docker API without TLS", 6443: "Kubernetes API", 10250: "Kubelet API", 2379: "etcd client API", 5900: "VNC", 3389: "RDP"}
117
118// managementPorts are management panels, monitoring exporters and service
119// discovery APIs: sensitive telemetry and configuration, usually behind their
120// own authentication, so exposure is Medium rather than Critical.
121var managementPorts = map[int]string{2376: "Docker API (TLS)", 8500: "Consul HTTP API", 9100: "Prometheus Node Exporter", 15672: "RabbitMQ Management", 10000: "Webmin", 2083: "cPanel", 2087: "WHM"}
122
123func registerExposureChecks() {
check.Register(&check.Check{
ID:        "NET-SVC-002",
Title:     "Control Plane or Remote Desktop Ports Network-Reachable",
Domain:    check.DomainNetwork,
Severity:  check.Critical,
Category:  check.CatNetwork,
Effort:    check.EffortMedium,
CVSS:      "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
Summary:   "Docker API, Kubernetes API, kubelet, etcd, VNC or RDP listen on network-reachable addresses.",
Rationale: "These services hand out administrative control of the host or the cluster. The unauthenticated Docker API and etcd give code execution or every cluster secret to whoever connects; RDP and VNC are the most attacked remote access services.",
Detection: "Parses local TCP and UDP socket tables and matches listeners bound to a non-loopback address against the default ports of these control planes and remote desktops. Severity follows the service identity: management panels and exporters are rated separately by NET-SVC-004. The binding (all interfaces, private or public address) is recorded as evidence. No packets are sent.",
Fix:       "Bind control planes to loopback or a dedicated management address, require mutual TLS or strong authentication, and filter access to approved source networks or a VPN.",
Verify:    "Review ss -tulpn and the host firewall from a trusted administrative session.",
Refs:      []check.Ref{{Title: "Docker Protect the Daemon Socket", URL: "https://docs.docker.com/engine/security/protect-access/"}, {Title: "Kubernetes Ports and Protocols", URL: "https://kubernetes.io/docs/reference/networking/ports-and-protocols/"}, {Title: "IANA Service Name and Transport Protocol Port Number Registry", URL: "https://www.iana.org/assignments/service-names-port-numbers"}},
Standards: check.Standards{CWE: []string{"CWE-1327", "CWE-923"}, OWASP: []string{"A05:2021"}, NIST: []string{"AC-17", "CM-7", "SC-7"}},
Run:       portListRun(controlPorts, "Control plane or remote desktop ports are network-reachable", "No control plane or remote desktop port is network-reachable"),
})
check.Register(&check.Check{
ID:        "NET-SVC-004",
Title:     "Management Panel or Monitoring Ports Network-Reachable",
Domain:    check.DomainNetwork,
Severity:  check.Medium,
Category:  check.CatNetwork,
Effort:    check.EffortLow,
CVSS:      "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N",
Summary:   "Webmin, cPanel, WHM, RabbitMQ Management, Consul, the Docker API with TLS or the Prometheus node exporter listen on network-reachable addresses.",
Rationale: "Management panels and exporters publish host metrics, service configuration and often a login form. They are a reconnaissance gift and a password guessing target, but they sit behind their own authentication or TLS, so the risk is lower than an open control plane.",
Detection: "Parses local TCP and UDP socket tables and matches listeners bound to a non-loopback address against the default ports of these management panels, exporters and discovery APIs. The binding (all interfaces, private or public address) is recorded as evidence. No packets are sent.",
Fix:       "Bind the panel or exporter to 127.0.0.1 or a management address, put it behind a reverse proxy with authentication, or restrict the port to monitoring hosts in the firewall.",
Verify:    "ss -tulpn shows these ports on 127.0.0.1, ::1 or a management address only.",
Refs:      []check.Ref{{Title: "Prometheus, Security model", URL: "https://prometheus.io/docs/operating/security/"}, {Title: "IANA Service Name and Transport Protocol Port Number Registry", URL: "https://www.iana.org/assignments/service-names-port-numbers"}},
Standards: check.Standards{CWE: []string{"CWE-1188", "CWE-1327"}, OWASP: []string{"A05:2021"}, NIST: []string{"AC-17", "CM-7", "SC-7"}},
Run:       portListRun(managementPorts, "Management panel or monitoring ports are network-reachable", "No management panel or monitoring port is network-reachable"),
})
158}
159
160// portListRun builds the Run function of a check that reports every
161// network-reachable listener whose port is in ports.
162func portListRun(ports map[int]string, failMsg, passMsg string) func(context.Context, sys.System) []check.Result {
return func(_ context.Context, s sys.System) []check.Result {
ls, err := collect.Listeners(s)
if err != nil {
	return []check.Result{check.IncompleteR("/proc/net", "Socket tables were unreadable or partial")}
}
var ev []string
for _, l := range ls {
	if n, ok := ports[l.Port]; ok && l.Public() {
		ev = append(ev, l.String()+" "+n+", bound to "+exposure(l))
	}
}
if len(ev) > 0 {
	return []check.Result{check.FailR("sockets", failMsg, ev...)}
}
return []check.Result{check.PassR("sockets", passMsg)}
}
179}
180
181func matchingLines(t string, needles ...string) []string {
var out []string
s := bufio.NewScanner(strings.NewReader(t))
for s.Scan() {
line := strings.TrimSpace(s.Text())
if line == "" || strings.HasPrefix(line, "#") {
	continue
}
l := strings.ToLower(line)
for _, n := range needles {
	if strings.Contains(l, strings.ToLower(n)) {
		out = append(out, line)
		break
	}
}
}
return out
198}

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If this page helped your work, please cite it. The version and web address are filled in; the access date is today's date in your browser. Every other style, and when credit is required, is on How to Cite OpenVAPT.

APA 7

OpenVAPT. (2026). NET-DB-012 Postfix Open Relay Controls (Version 0.1.0-alpha.6). OpenVAPT Check Catalogue. Retrieved October 16, 2026, from https://openvapt.com/checks/NET-DB-012.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_net_db_012,
  author       = {{OpenVAPT}},
  title        = {{NET-DB-012 Postfix Open Relay Controls}},
  year         = {2026},
  howpublished = {\url{https://openvapt.com/checks/NET-DB-012.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 network
2
3	import (
4	"bufio"
5	"context"
6	"strings"
7
8	"github.com/openvapt/openvapt/internal/check"
9	"github.com/openvapt/openvapt/internal/checks/collect"
10	"github.com/openvapt/openvapt/internal/sys"
11	)
12
13	func readAny(ctx context.Context, s sys.System, paths ...string) (string, string, bool, bool) {
14	var found []string
15	var text strings.Builder
16	complete := true
17	for _, p := range paths {
18	r, err := s.ReadFile(ctx, p)
19	if err == nil {
20	found = append(found, p)
21	text.Write(r.Data)
22	text.WriteByte('\n')
23	complete = complete && r.Complete
24	}
25	}
26	if len(found) == 0 {
27	return "", "", false, false
28	}
29	return strings.Join(found, ", "), text.String(), complete, true
30	}
31	func simpleFileCheck(id, title string, sev check.Severity, cat check.Category, summary, rationale, detection, fix, verify, cvss string, paths []string, ref check.Ref, bad func(string) []string) {
32	check.Register(&check.Check{
33	ID: id, Title: title, Domain: check.DomainNetwork, Severity: sev, Category: cat, Effort: check.EffortLow, CVSS: cvss, Summary: summary, Rationale: rationale, Detection: detection, Fix: fix, Verify: verify, Refs: []check.Ref{ref}, Standards: dataStandards(id), Run: func(ctx context.Context, s sys.System) []check.Result {
34	p, text, complete, ok := readAny(ctx, s, paths...)
35	if !ok {
36	return []check.Result{check.SkipR(strings.Join(paths, ", "), "Configuration was not found")}
37	}
38	ev := bad(text)
39	if len(ev) > 0 {
40	return []check.Result{check.FailR(p, summary, ev...)}
41	}
42	if !complete {
43	return []check.Result{check.IncompleteR(p, "Configuration input was truncated")}
44	}
45	return []check.Result{check.PassR(p, "No unsafe setting was found")}
46	}})
47	}
48
49	func init() {
50	simpleFileCheck("NET-DB-008", "Unsafe NFS Export Options", check.High, check.CatData, "NFS exports are world-accessible or use no_root_squash or insecure.", "These export options can grant untrusted clients filesystem access or preserve remote root privileges.", "Reads /etc/exports and active exports.d fragments, ignoring comments, and flags , no_root_squash, and insecure.", "Restrict every export to explicit client CIDRs, use root_squash, remove insecure, and reload exports.", "Run exportfs -v during approved administration and confirm only intended networks and safe options appear.", "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H", []string{"/etc/exports"}, check.Ref{Title: "Linux exports(5)", URL: "https://man7.org/linux/man-pages/man5/exports.5.html"}, func(t string) []string { return matchingLines(t, "", "no_root_squash", "insecure") })
51	simpleFileCheck("NET-DB-009", "Unsafe Samba Guest or SMB1 Configuration", check.High, check.CatData, "Samba permits guest access, maps unknown users to guest, or allows SMB1.", "Guest shares weaken accountability, while SMB1 lacks modern protocol protections and has a long history of severe flaws.", "Reads smb.conf and flags guest ok = yes, permissive map to guest modes, or a server min protocol below SMB2.", "Set guest ok = no, map to guest = Never, and server min protocol = SMB2_02 or newer. Review each share ACL.", "Run testparm -s during approved administration and confirm the effective values.", "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H", []string{"/etc/samba/smb.conf"}, check.Ref{Title: "Samba smb.conf Manual", URL: "https://www.samba.org/samba/docs/current/man-html/smb.conf.5.html"}, func(t string) []string {
52	l := strings.ToLower(t)
53	var e []string
54	if strings.Contains(l, "guest ok = yes") \|\| strings.Contains(l, "guest ok=yes") {
55	e = append(e, "guest ok enabled")
56	}
57	if strings.Contains(l, "map to guest = bad") \|\| strings.Contains(l, "map to guest=bad") {
58	e = append(e, "unknown users map to guest")
59	}
60	if strings.Contains(l, "server min protocol = nt1") \|\| strings.Contains(l, "server min protocol=nt1") {
61	e = append(e, "SMB1 NT1 enabled")
62	}
63	return e
64	})
65	simpleFileCheck("NET-DB-010", "BIND Open Recursion", check.High, check.CatData, "BIND enables recursion without restricting recursive clients.", "An open recursive resolver can be abused for reflection attacks and permits outsiders to consume resolver resources.", "Reads named.conf and flags recursion yes when neither allow-recursion nor allow-query-cache restricts clients.", "Disable recursion on authoritative-only servers, or set allow-recursion and allow-query-cache to explicit trusted networks.", "Run named-checkconf and query recursion from an untrusted test network under an approved test plan.", "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H", []string{"/etc/bind/named.conf.options", "/etc/named.conf"}, check.Ref{Title: "BIND 9 Administrator Reference Manual - Access Control", URL: "https://bind9.readthedocs.io/en/latest/reference.html#access-control"}, func(t string) []string {
66	l := strings.ToLower(t)
67	if strings.Contains(l, "recursion yes") && !strings.Contains(l, "allow-recursion") && !strings.Contains(l, "allow-query-cache") {
68	return []string{"recursion yes without a client ACL"}
69	}
70	return nil
71	})
72	simpleFileCheck("NET-DB-011", "BIND Zone Transfers Allowed to Any", check.High, check.CatData, "BIND permits zone transfers to any client.", "Unrestricted transfers disclose the complete DNS namespace and provide attackers with a detailed target inventory.", "Reads named.conf and flags allow-transfer clauses containing any.", "Set allow-transfer to none or explicit secondary server addresses, preferably protected with TSIG.", "Run named-checkconf and verify AXFR is refused from an unauthorized test host.", "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N", []string{"/etc/bind/named.conf.options", "/etc/named.conf"}, check.Ref{Title: "BIND 9 Administrator Reference Manual - allow-transfer", URL: "https://bind9.readthedocs.io/en/latest/reference.html#namedconf-statement-allow-transfer"}, func(t string) []string {
73	l := strings.ToLower(t)
74	if strings.Contains(l, "allow-transfer") && strings.Contains(l, "any;") {
75	return []string{"allow-transfer includes any"}
76	}
77	return nil
78	})
79	registerMailChecks()
80	registerExposureChecks()
81	}
82
83	func registerMailChecks() {
84	simpleFileCheck("NET-DB-012", "Postfix Open Relay Controls", check.High, check.CatData, "Postfix relay restrictions are missing or mynetworks trusts overly broad ranges.", "An open relay enables spam and phishing, damages domain reputation, and can expose the host to blocklisting.", "Parses main.cf for smtpd_relay_restrictions with reject_unauth_destination and flags 0.0.0.0/0 or ::/0 in mynetworks.", "Set smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination and narrow mynetworks.", "Run postconf -n during approved administration and perform only an authorized relay test.", "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L", []string{"/etc/postfix/main.cf"}, check.Ref{Title: "Postfix SMTP Relay and Access Control", URL: "https://www.postfix.org/SMTPD_ACCESS_README.html"}, func(t string) []string {
85	m := collect.ParseKV(t)
86	relay := strings.ToLower(strings.Join(m["smtpd_relay_restrictions"], " "))
87	nets := strings.ToLower(strings.Join(m["mynetworks"], " "))
88	var e []string
89	if !strings.Contains(relay, "reject_unauth_destination") {
90	e = append(e, "reject_unauth_destination missing")
91	}
92	if strings.Contains(nets, "0.0.0.0/0") \|\| strings.Contains(nets, "::/0") {
93	e = append(e, "mynetworks trusts all addresses")
94	}
95	return e
96	})
97	simpleFileCheck("NET-DB-013", "Mail Cleartext Authentication Allowed", check.Medium, check.CatCrypto, "Postfix or Dovecot permits plaintext authentication without requiring TLS.", "Credentials sent before transport encryption can be observed by any party able to intercept the connection.", "Reads Postfix smtpd_tls_auth_only and Dovecot disable_plaintext_auth, and flags no values.", "Set smtpd_tls_auth_only = yes and disable_plaintext_auth = yes. Use implicit TLS on ports 465, 993, and 995. STARTTLS assessment is out of scope.", "Confirm the effective mail configuration and that unauthenticated plaintext sessions do not advertise AUTH.", "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N", []string{"/etc/postfix/main.cf", "/etc/dovecot/conf.d/10-auth.conf"}, check.Ref{Title: "Dovecot Authentication Settings", URL: "https://doc.dovecot.org/main/core/config/auth/settings.html"}, func(t string) []string {
98	m := collect.ParseKV(t)
99	var e []string
100	for _, k := range []string{"smtpd_tls_auth_only", "disable_plaintext_auth"} {
101	for _, v := range m[k] {
102	if strings.EqualFold(strings.TrimSpace(v), "no") {
103	e = append(e, k+" is no")
104	}
105	}
106	}
107	return e
108	})
109	}
110
111	// controlPorts are control planes and remote desktops: reaching one of them
112	// from the network means administrative control of the host or cluster
113	// (vendor documentation and the IANA registry). SNMP is not here: it is a
114	// cleartext protocol and belongs to NET-SVC-001 only, so one socket never
115	// yields more than one finding per check family.
116	var controlPorts = map[int]string{2375: "Docker API without TLS", 6443: "Kubernetes API", 10250: "Kubelet API", 2379: "etcd client API", 5900: "VNC", 3389: "RDP"}
117
118	// managementPorts are management panels, monitoring exporters and service
119	// discovery APIs: sensitive telemetry and configuration, usually behind their
120	// own authentication, so exposure is Medium rather than Critical.
121	var managementPorts = map[int]string{2376: "Docker API (TLS)", 8500: "Consul HTTP API", 9100: "Prometheus Node Exporter", 15672: "RabbitMQ Management", 10000: "Webmin", 2083: "cPanel", 2087: "WHM"}
122
123	func registerExposureChecks() {
124	check.Register(&check.Check{
125	ID: "NET-SVC-002",
126	Title: "Control Plane or Remote Desktop Ports Network-Reachable",
127	Domain: check.DomainNetwork,
128	Severity: check.Critical,
129	Category: check.CatNetwork,
130	Effort: check.EffortMedium,
131	CVSS: "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
132	Summary: "Docker API, Kubernetes API, kubelet, etcd, VNC or RDP listen on network-reachable addresses.",
133	Rationale: "These services hand out administrative control of the host or the cluster. The unauthenticated Docker API and etcd give code execution or every cluster secret to whoever connects; RDP and VNC are the most attacked remote access services.",
134	Detection: "Parses local TCP and UDP socket tables and matches listeners bound to a non-loopback address against the default ports of these control planes and remote desktops. Severity follows the service identity: management panels and exporters are rated separately by NET-SVC-004. The binding (all interfaces, private or public address) is recorded as evidence. No packets are sent.",
135	Fix: "Bind control planes to loopback or a dedicated management address, require mutual TLS or strong authentication, and filter access to approved source networks or a VPN.",
136	Verify: "Review ss -tulpn and the host firewall from a trusted administrative session.",
137	Refs: []check.Ref{{Title: "Docker Protect the Daemon Socket", URL: "https://docs.docker.com/engine/security/protect-access/"}, {Title: "Kubernetes Ports and Protocols", URL: "https://kubernetes.io/docs/reference/networking/ports-and-protocols/"}, {Title: "IANA Service Name and Transport Protocol Port Number Registry", URL: "https://www.iana.org/assignments/service-names-port-numbers"}},
138	Standards: check.Standards{CWE: []string{"CWE-1327", "CWE-923"}, OWASP: []string{"A05:2021"}, NIST: []string{"AC-17", "CM-7", "SC-7"}},
139	Run: portListRun(controlPorts, "Control plane or remote desktop ports are network-reachable", "No control plane or remote desktop port is network-reachable"),
140	})
141	check.Register(&check.Check{
142	ID: "NET-SVC-004",
143	Title: "Management Panel or Monitoring Ports Network-Reachable",
144	Domain: check.DomainNetwork,
145	Severity: check.Medium,
146	Category: check.CatNetwork,
147	Effort: check.EffortLow,
148	CVSS: "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N",
149	Summary: "Webmin, cPanel, WHM, RabbitMQ Management, Consul, the Docker API with TLS or the Prometheus node exporter listen on network-reachable addresses.",
150	Rationale: "Management panels and exporters publish host metrics, service configuration and often a login form. They are a reconnaissance gift and a password guessing target, but they sit behind their own authentication or TLS, so the risk is lower than an open control plane.",
151	Detection: "Parses local TCP and UDP socket tables and matches listeners bound to a non-loopback address against the default ports of these management panels, exporters and discovery APIs. The binding (all interfaces, private or public address) is recorded as evidence. No packets are sent.",
152	Fix: "Bind the panel or exporter to 127.0.0.1 or a management address, put it behind a reverse proxy with authentication, or restrict the port to monitoring hosts in the firewall.",
153	Verify: "ss -tulpn shows these ports on 127.0.0.1, ::1 or a management address only.",
154	Refs: []check.Ref{{Title: "Prometheus, Security model", URL: "https://prometheus.io/docs/operating/security/"}, {Title: "IANA Service Name and Transport Protocol Port Number Registry", URL: "https://www.iana.org/assignments/service-names-port-numbers"}},
155	Standards: check.Standards{CWE: []string{"CWE-1188", "CWE-1327"}, OWASP: []string{"A05:2021"}, NIST: []string{"AC-17", "CM-7", "SC-7"}},
156	Run: portListRun(managementPorts, "Management panel or monitoring ports are network-reachable", "No management panel or monitoring port is network-reachable"),
157	})
158	}
159
160	// portListRun builds the Run function of a check that reports every
161	// network-reachable listener whose port is in ports.
162	func portListRun(ports map[int]string, failMsg, passMsg string) func(context.Context, sys.System) []check.Result {
163	return func(_ context.Context, s sys.System) []check.Result {
164	ls, err := collect.Listeners(s)
165	if err != nil {
166	return []check.Result{check.IncompleteR("/proc/net", "Socket tables were unreadable or partial")}
167	}
168	var ev []string
169	for _, l := range ls {
170	if n, ok := ports[l.Port]; ok && l.Public() {
171	ev = append(ev, l.String()+" "+n+", bound to "+exposure(l))
172	}
173	}
174	if len(ev) > 0 {
175	return []check.Result{check.FailR("sockets", failMsg, ev...)}
176	}
177	return []check.Result{check.PassR("sockets", passMsg)}
178	}
179	}
180
181	func matchingLines(t string, needles ...string) []string {
182	var out []string
183	s := bufio.NewScanner(strings.NewReader(t))
184	for s.Scan() {
185	line := strings.TrimSpace(s.Text())
186	if line == "" \|\| strings.HasPrefix(line, "#") {
187	continue
188	}
189	l := strings.ToLower(line)
190	for _, n := range needles {
191	if strings.Contains(l, strings.ToLower(n)) {
192	out = append(out, line)
193	break
194	}
195	}
196	}
197	return out
198	}