Fix .onion tests to only apply to EV certificates (#449)

Before this change, ZLint would reject .onion names in non-EV certs
via the `lint_san_dns_name_onion_not_ev_cert` lint, and if that
was suppressed, then complain about the missing Tor Service
Descriptor extension. As of CA/Browser Forum Ballot SC27, it's
allowed for v3 onion names to appear in DV/OV/IV certificates, and
the Tor Service Descriptor extension is neither required nor
prohibited for these.

This change corrects the Tor Service Descriptor tests to properly
account for it being mandatory for EV, while optional for DV/OV/IV.
This does not introduce new lints to ensure that the address is
itself a well-formed V2 (if EV) or V3 (all types) address, which
will come in a follow-up change.

Closes #440

v2/lints/cabf_br/lint_ext_tor_service_descriptor_hash_invalid.go

@@ -24,19 +24,21 @@ import (
 	"github.com/zmap/zlint/v2/util"
 )
 
-const onionTLD = ".onion"
-
 type torServiceDescHashInvalid struct{}
 
 func (l *torServiceDescHashInvalid) Initialize() error {
 	// There is nothing to initialize for a torServiceDescHashInvalid linter.
 	return nil
 }
 
-// CheckApplies returns true if the certificate is a subscriber certificate that
-// contains a subject name ending in `.onion`.
+// CheckApplies returns true if the TorServiceDescriptor extension is present
+// or if the certificate is an EV subscriber certificate with one or more
+// subject names ending in `.onion`.
 func (l *torServiceDescHashInvalid) CheckApplies(c *x509.Certificate) bool {
-	return util.IsSubscriberCert(c) && util.CertificateSubjInTLD(c, onionTLD)
+	ext := util.GetExtFromCert(c, util.BRTorServiceDescriptor)
+	return ext != nil || (util.IsSubscriberCert(c) &&
+		util.CertificateSubjInTLD(c, util.OnionTLD) &&
+		util.IsEV(c.PolicyIdentifiers))
 }
 
 // failResult is a small utility function for creating a failed lint result.
@@ -86,25 +88,25 @@ func lintOnionURL(onion string) *lint.LintResult {
 // Execute will lint the provided certificate. An lint.Error lint.LintResult will be
 // returned if:
 //
-//   1) There is no TorServiceDescriptor extension present.
+//   1) There is no TorServiceDescriptor extension present and it's required
 //   2) There were no TorServiceDescriptors parsed by zcrypto
 //   3) There are TorServiceDescriptorHash entries with an invalid Onion URL.
 //   4) There are TorServiceDescriptorHash entries with an unknown hash
 //      algorithm or incorrect hash bit length.
 //   5) There is a TorServiceDescriptorHash entry that doesn't correspond to
 //      an onion subject in the cert.
 //   6) There is an onion subject in the cert that doesn't correspond to
-//      a TorServiceDescriptorHash.
+//      a TorServiceDescriptorHash, if required.
 func (l *torServiceDescHashInvalid) Execute(c *x509.Certificate) *lint.LintResult {
-	// If the BRTorServiceDescriptor extension is missing return a lint error. We
-	// know the cert contains one or more `.onion` subjects because of
-	// `CheckApplies` and all such certs are expected to have this extension after
-	// util.CABV201Date.
+	// If the certificate is EV, the BRTorServiceDescriptor extension is required.
+	// We know that `CheckApplies` will only apply if the certificate has the
+	// extension or that it's required, so this will only fail when it's
+	// required.
 	if ext := util.GetExtFromCert(c, util.BRTorServiceDescriptor); ext == nil {
 		return failResult(
 			"certificate contained a %s domain but is missing a TorServiceDescriptor "+
 				"extension (oid %s)",
-			onionTLD, util.BRTorServiceDescriptor.String())
+			util.OnionTLD, util.BRTorServiceDescriptor.String())
 	}
 
 	// The certificate should have at least one TorServiceDescriptorHash in the
@@ -114,21 +116,21 @@ func (l *torServiceDescHashInvalid) Execute(c *x509.Certificate) *lint.LintResul
 		return failResult(
 			"certificate contained a %s domain but TorServiceDescriptor "+
 				"extension (oid %s) had no TorServiceDescriptorHash objects",
-			onionTLD, util.BRTorServiceDescriptor.String())
+			util.OnionTLD, util.BRTorServiceDescriptor.String())
 	}
 
 	// Build a map of all the eTLD+1 onion subjects in the cert to compare against
 	// the service descriptors.
 	onionETLDPlusOneMap := make(map[string]string)
 	for _, subj := range append(c.DNSNames, c.Subject.CommonName) {
-		if !strings.HasSuffix(subj, onionTLD) {
+		if !strings.HasSuffix(subj, util.OnionTLD) {
 			continue
 		}
 		labels := strings.Split(subj, ".")
 		if len(labels) < 2 {
 			return failResult("certificate contained a %s domain with too few "+
 				"labels: %q",
-				onionTLD, subj)
+				util.OnionTLD, subj)
 		}
 		eTLDPlusOne := strings.Join(labels[len(labels)-2:], ".")
 		onionETLDPlusOneMap[eTLDPlusOne] = subj
@@ -184,14 +186,19 @@ func (l *torServiceDescHashInvalid) Execute(c *x509.Certificate) *lint.LintResul
 		descriptorMap[hostname] = descriptor
 	}
 
-	// Check if any of the onion subjects in the certificate don't have
-	// a TorServiceDescriptorHash for the eTLD+1 in the descriptorMap.
-	for eTLDPlusOne, subjDomain := range onionETLDPlusOneMap {
-		if _, found := descriptorMap[eTLDPlusOne]; !found {
-			return failResult(
-				"%s subject domain name %q does not have a corresponding "+
-					"TorServiceDescriptorHash for its eTLD+1",
-				onionTLD, subjDomain)
+	// For EV certificates, every `.onion` name is required to have a
+	// TorServiceDescriptorHash, so check if any of the onion subjects in the
+	// certificate don't have a TorServiceDescriptorHash for the eTLD+1 in the
+	// descriptorMap.
+	// See also https://github.com/cabforum/documents/issues/190
+	if util.IsEV(c.PolicyIdentifiers) {
+		for eTLDPlusOne, subjDomain := range onionETLDPlusOneMap {
+			if _, found := descriptorMap[eTLDPlusOne]; !found {
+				return failResult(
+					"%s subject domain name %q does not have a corresponding "+
+						"TorServiceDescriptorHash for its eTLD+1",
+					util.OnionTLD, subjDomain)
+			}
 		}
 	}
 
@@ -204,8 +211,8 @@ func (l *torServiceDescHashInvalid) Execute(c *x509.Certificate) *lint.LintResul
 func init() {
 	lint.RegisterLint(&lint.Lint{
 		Name:          "e_ext_tor_service_descriptor_hash_invalid",
-		Description:   "certificates with .onion names need valid TorServiceDescriptors in extension",
-		Citation:      "BRS: Ballot 201",
+		Description:   "certificates with v2 .onion names need valid TorServiceDescriptors in extension",
+		Citation:      "BRs: Ballot 201, Ballot SC27",
 		Source:        lint.CABFBaselineRequirements,
 		EffectiveDate: util.CABV201Date,
 		Lint:          &torServiceDescHashInvalid{},

v2/lints/cabf_br/lint_ext_tor_service_descriptor_hash_invalid_test.go

@@ -16,7 +16,7 @@ func TestTorDescHashInvalid(t *testing.T) {
 	}{
 		{
 			Name:           "Onion subject, no service descriptor extension, before util.CABV201Date",
-			InputFilename:  "dnsNameOnionTLD.pem",
+			InputFilename:  "onionSANEVBefore201.pem",
 			ExpectedResult: lint.NE,
 		},
 		{

v2/lints/cabf_br/lint_san_dns_name_onion_not_ev_cert.go

@@ -24,15 +24,16 @@ import (
 
 type onionNotEV struct{}
 
-// Initialize for an onionNotEV linter is a NOP.
 func (l *onionNotEV) Initialize() error {
 	return nil
 }
 
-// CheckApplies returns true if the certificate is a subscriber certificate that
-// contains a subject name ending in `.onion`.
+// This lint only applies for certificates issued before CA/Browser Forum
+// Ballot SC27, which permitted .onion within non-EV certificates
 func (l *onionNotEV) CheckApplies(c *x509.Certificate) bool {
-	return util.IsSubscriberCert(c) && util.CertificateSubjInTLD(c, util.OnionTLD)
+	return c.NotBefore.Before(util.CABFBRs_1_6_9_Date) &&
+		util.IsSubscriberCert(c) &&
+		util.CertificateSubjInTLD(c, util.OnionTLD)
 }
 
 // Execute returns an lint.Error lint.LintResult if the certificate is not an EV

v2/lints/cabf_br/lint_san_dns_name_onion_not_ev_cert_test.go

@@ -30,6 +30,11 @@ func TestOnionNotEV(t *testing.T) {
 			InputFilename:  "onionSANEV.pem",
 			ExpectedResult: lint.Pass,
 		},
+		{
+			Name:           "Onion subject, non EV cert, after util.CABF_BRs_1_6_9_Date",
+			InputFilename:  "onionSANv3Name.pem",
+			ExpectedResult: lint.NA,
+		},
 	}
 
 	for _, tc := range testCases {

v2/testdata/onionSANEVBefore201.pem

@@ -0,0 +1,46 @@
+Certificate:
+    Data:
+        Version: 3 (0x2)
+        Serial Number: 31337 (0x7a69)
+        Signature Algorithm: sha256WithRSAEncryption
+        Issuer: CN = Zmap Onion CA
+        Validity
+            Not Before: Jun  2 15:17:12 2017 GMT
+            Not After : Mar  2 15:17:12 2018 GMT
+        Subject: CN = zmap.io
+        Subject Public Key Info:
+            Public Key Algorithm: rsaEncryption
+                RSA Public-Key: (512 bit)
+                Modulus:
+                    00:e7:b5:d2:75:b1:04:c6:24:e7:b2:1f:b1:22:2b:
+                    30:35:e9:ae:d8:b4:40:a2:34:19:01:80:a4:2e:a8:
+                    0a:de:43:49:3d:70:a2:22:0a:a8:51:bd:9b:13:fb:
+                    6e:cc:60:65:88:32:fc:33:21:06:4d:a3:27:fe:b0:
+                    75:80:cc:d4:df
+                Exponent: 65537 (0x10001)
+        X509v3 extensions:
+            X509v3 Extended Key Usage: 
+                TLS Web Server Authentication, TLS Web Client Authentication
+            X509v3 Basic Constraints: critical
+                CA:FALSE
+            X509v3 Subject Alternative Name: 
+                DNS:zmap.io, DNS:zmap.onion
+            X509v3 Certificate Policies: 
+                Policy: 1.3.6.1.4.1.36305.2
+
+    Signature Algorithm: sha256WithRSAEncryption
+         30:f7:da:b6:a8:15:e3:d9:3a:aa:56:9f:88:06:ea:ae:5e:75:
+         58:d5:7c:ea:31:b7:f2:a5:fe:e8:9c:68:f8:0a:6f:64:d1:f3:
+         10:53:48:56:55:c6:5c:20:04:bf:b1:44:6a:69:1d:d5:fb:8e:
+         57:99:2a:87:1f:b0:d7:ae:a8:20
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----

v2/testdata/onionSANMissingServDescHash.pem

@@ -25,22 +25,26 @@ Certificate:
                 CA:FALSE
             X509v3 Subject Alternative Name: 
                 DNS:zmap.io, DNS:zmap.onion, DNS:missing.onion
+            X509v3 Certificate Policies: 
+                Policy: 1.3.6.1.4.1.36305.2
+
             2.23.140.1.31: 
                 0F0D..https://zmap.onion0...`.H.e.....!..I..I..e\..?.>.{{}.G*.bx0q.9.f8\
     Signature Algorithm: sha256WithRSAEncryption
-         34:7a:85:96:cb:61:a1:04:78:17:42:e5:f9:b1:e6:0a:33:f7:
-         09:4a:d3:43:d7:56:e7:97:d7:9b:ad:78:e2:16:80:66:1b:06:
-         19:d9:bc:db:8d:f8:87:6b:98:5a:ef:6a:8c:4f:b1:64:e9:eb:
-         c3:72:f5:30:7a:79:ac:1d:2a:06
+         09:9b:05:52:98:a3:c1:38:97:46:e9:64:71:26:5d:4c:9b:8f:
+         28:64:58:c6:c6:dd:2e:c2:ba:23:dd:67:a9:1e:bc:2b:08:25:
+         cd:d8:f5:da:90:02:2a:b4:45:fd:19:02:51:99:27:2e:ad:dd:
+         f2:e4:32:b4:26:19:a2:d3:1f:76
 -----BEGIN CERTIFICATE-----
-MIIBzzCCAXmgAwIBAgICBTkwDQYJKoZIhvcNAQELBQAwGDEWMBQGA1UEAxMNWm1h
+MIIB5zCCAZGgAwIBAgICBTkwDQYJKoZIhvcNAQELBQAwGDEWMBQGA1UEAxMNWm1h
 cCBPbmlvbiBDQTAeFw0xOTAzMDIyMDU0NDBaFw0yMDAzMDIyMDU0NDBaMBIxEDAO
 BgNVBAMTB3ptYXAuaW8wXDANBgkqhkiG9w0BAQEFAANLADBIAkEAyhMFSI9h3qP7
 DR/luYGBrqeBTmTl4pvs45tjx5I9PkZjNB+Cc+qHChHgl15Rh/f2J0fn+RVx53bE
-btTumyx8awIDAQABo4GyMIGvMB0GA1UdJQQWMBQGCCsGAQUFBwMBBggrBgEFBQcD
+btTumyx8awIDAQABo4HKMIHHMB0GA1UdJQQWMBQGCCsGAQUFBwMBBggrBgEFBQcD
 AjAMBgNVHRMBAf8EAjAAMC0GA1UdEQQmMCSCB3ptYXAuaW+CCnptYXAub25pb26C
-DW1pc3Npbmcub25pb24wUQYFZ4EMAR8ESDBGMEQMEmh0dHBzOi8vem1hcC5vbmlv
-bjALBglghkgBZQMEAgEDIQDHSfWySZyPZVwZsz/5PgN7e32+RyqsYngwcbA5uGY4
-XDANBgkqhkiG9w0BAQsFAANBADR6hZbLYaEEeBdC5fmx5goz9wlK00PXVueX15ut
-eOIWgGYbBhnZvNuN+IdrmFrvaoxPsWTp68Ny9TB6eawdKgY=
+DW1pc3Npbmcub25pb24wFgYDVR0gBA8wDTALBgkrBgEEAYKbUQIwUQYFZ4EMAR8E
+SDBGMEQMEmh0dHBzOi8vem1hcC5vbmlvbjALBglghkgBZQMEAgEDIQDHSfWySZyP
+ZVwZsz/5PgN7e32+RyqsYngwcbA5uGY4XDANBgkqhkiG9w0BAQsFAANBAAmbBVKY
+o8E4l0bpZHEmXUybjyhkWMbG3S7CuiPdZ6kevCsIJc3Y9dqQAiq0Rf0ZAlGZJy6t
+3fLkMrQmGaLTH3Y=
 -----END CERTIFICATE-----

v2/testdata/onionSANv3Name.pem

@@ -0,0 +1,78 @@
+Certificate:
+    Data:
+        Version: 3 (0x2)
+        Serial Number: 2050924719016116738 (0x1c76592a6a060202)
+        Signature Algorithm: sha256WithRSAEncryption
+        Issuer: CN = zlint test 6fb5f7
+        Validity
+            Not Before: Mar 28 00:00:00 2020 GMT
+            Not After : Mar 28 00:00:00 2021 GMT
+        Subject: CN = example.test
+        Subject Public Key Info:
+            Public Key Algorithm: rsaEncryption
+                RSA Public-Key: (2048 bit)
+                Modulus:
+                    00:d3:cf:55:71:96:a8:51:60:82:3d:12:84:61:82:
+                    01:67:64:d8:38:07:b7:93:7b:d1:40:c3:67:cd:dd:
+                    b0:bc:84:67:38:65:5c:69:91:33:30:84:6c:38:ae:
+                    65:c5:5f:02:39:7a:38:f1:55:9d:79:57:b8:75:47:
+                    07:55:63:9e:ff:21:a7:56:8b:be:9c:99:88:86:f9:
+                    36:64:2b:ac:a1:d8:7c:31:ad:c5:59:1e:c1:b3:06:
+                    53:d5:77:27:39:d6:68:a3:c6:5c:65:c3:d8:90:2d:
+                    2b:bd:9d:c4:39:9c:3f:53:53:af:1b:9c:6b:0f:3e:
+                    04:96:dd:40:7a:21:29:eb:76:e8:2c:95:7b:73:da:
+                    65:d0:cc:a4:51:cc:f7:6d:4c:d7:8c:e6:d8:bf:20:
+                    d9:01:a6:a4:b3:35:60:ac:c2:04:d4:02:d7:1c:8d:
+                    71:62:76:a5:10:4c:36:bf:16:c2:be:1d:71:45:95:
+                    66:17:32:d0:06:94:67:36:90:db:20:53:36:c4:55:
+                    5c:bb:cb:9c:68:29:43:b6:76:11:da:6e:c2:6c:da:
+                    ae:1c:57:c6:13:a9:2e:c0:cb:8d:de:2f:19:24:79:
+                    d8:28:83:27:5d:29:e9:4a:f7:3b:04:5a:6c:db:c9:
+                    bb:00:e1:30:e0:8e:a1:cf:92:1c:87:77:ab:82:29:
+                    66:f1
+                Exponent: 65537 (0x10001)
+        X509v3 extensions:
+            X509v3 Key Usage: critical
+                Digital Signature, Key Encipherment
+            X509v3 Extended Key Usage: 
+                TLS Web Server Authentication, TLS Web Client Authentication
+            X509v3 Basic Constraints: critical
+                CA:FALSE
+            X509v3 Subject Alternative Name: 
+                DNS:l5satjgud6gucryazcyvyvhuxhr74u6ygigiuyixe3a6ysis67ororad.onion, DNS:example.test
+    Signature Algorithm: sha256WithRSAEncryption
+         aa:ea:24:45:7a:f2:84:6f:bd:0f:43:63:0d:d0:6f:56:cb:43:
+         1a:81:b3:38:fa:79:28:f7:16:1b:a7:6a:79:6d:05:98:46:3f:
+         27:fa:21:8a:0d:2d:8c:43:ba:6c:e9:4f:7a:60:fd:fa:9d:e7:
+         cf:f4:63:e6:ce:25:76:64:59:d8:49:29:50:d1:88:90:fb:3d:
+         06:77:de:4c:25:e5:3a:87:ff:1e:80:c6:18:11:ca:69:c5:6b:
+         eb:d4:e7:a7:76:ca:45:5c:77:ec:46:ea:c9:55:6f:4b:69:cb:
+         71:9d:90:24:c7:3f:42:13:97:54:5e:ef:aa:d6:87:89:97:1b:
+         6e:cb:c3:53:61:b0:1c:1b:5e:7c:82:5f:2f:bc:d5:4b:b5:a9:
+         5b:db:36:05:99:7a:26:2b:7d:88:12:a1:6a:29:28:84:86:62:
+         df:dd:92:eb:eb:5e:28:a1:47:8a:a2:f1:8e:a4:50:20:d4:21:
+         81:e1:93:e1:b4:7a:2c:0f:96:ac:d8:07:d8:cc:39:c9:93:11:
+         7f:95:c5:9a:91:b8:09:cb:06:7f:2d:24:6f:53:14:43:68:d8:
+         3b:4d:31:2f:68:cd:8a:34:12:6d:d5:57:02:61:e4:4b:72:31:
+         d1:2c:f1:3c:db:85:4e:6b:f6:32:8c:88:1a:22:a0:b2:11:0e:
+         25:4d:be:7e
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----

v2/util/time.go

@@ -57,6 +57,7 @@ var (
 	MozillaPolicy22Date         = time.Date(2013, time.July, 26, 0, 0, 0, 0, time.UTC)
 	MozillaPolicy24Date         = time.Date(2017, time.February, 28, 0, 0, 0, 0, time.UTC)
 	MozillaPolicy27Date         = time.Date(2020, time.January, 1, 0, 0, 0, 0, time.UTC)
+	CABFBRs_1_6_9_Date          = time.Date(2020, time.March, 27, 0, 0, 0, 0, time.UTC)
 	AppleReducedLifetimeDate    = time.Date(2020, time.September, 1, 0, 0, 0, 0, time.UTC)
 )