Add CRL Lints for the ReasonCode extension from the baseline requirem…

…ents and RFC 5280.

v3/lints/cabf_br/lint_cabf_crl_reason_code_not_critical.go

@@ -0,0 +1,66 @@
+package cabf_br
+
+/*
+ * ZLint Copyright 2023 Regents of the University of Michigan
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy
+ * of the License at http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+import (
+	"github.com/zmap/zcrypto/x509"
+	"github.com/zmap/zlint/v3/lint"
+	"github.com/zmap/zlint/v3/util"
+)
+
+type crlReasonCodeNotCritical struct{}
+
+func init() {
+	lint.RegisterRevocationListLint(&lint.RevocationListLint{
+		LintMetadata: lint.LintMetadata{
+			Name:          "e_cab_crl_reason_code_not_critical",
+			Description:   "If present, CRL Reason Code extension MUST NOT be marked critical.",
+			Citation:      "BRs: 7.2.2",
+			Source:        lint.CABFBaselineRequirements,
+			EffectiveDate: util.CABEffectiveDate,
+		},
+		Lint: NewCrlReasonCodeNotCritical,
+	})
+}
+
+func NewCrlReasonCodeNotCritical() lint.RevocationListLintInterface {
+	return &crlReasonCodeNotCritical{}
+}
+
+func (l *crlReasonCodeNotCritical) CheckApplies(c *x509.RevocationList) bool {
+	for _, c := range c.RevokedCertificates {
+		if c.ReasonCode == nil {
+			continue
+		}
+		return true
+	}
+	return false
+}
+
+func (l *crlReasonCodeNotCritical) Execute(c *x509.RevocationList) *lint.LintResult {
+	for _, c := range c.RevokedCertificates {
+		if c.ReasonCode == nil {
+			continue
+		}
+		for _, ext := range c.Extensions {
+			if ext.Id.Equal(util.ReasonCodeOID) {
+				if ext.Critical {
+					return &lint.LintResult{Status: lint.Error, Details: "CRL Reason Code extension MUST NOT be marked as critical."}
+				}
+			}
+		}
+	}
+	return &lint.LintResult{Status: lint.Pass}
+}

v3/lints/cabf_br/lint_cabf_crl_reason_code_not_critical_test.go

@@ -0,0 +1,59 @@
+package cabf_br
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/zmap/zlint/v3/lint"
+	"github.com/zmap/zlint/v3/test"
+)
+
+/*
+ * ZLint Copyright 2021 Regents of the University of Michigan
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy
+ * of the License at http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+func TestCrlReasonCodeNotCrit(t *testing.T) {
+	t.Parallel()
+	testCases := []struct {
+		name       string
+		path       string
+		want       lint.LintStatus
+		wantSubStr string
+	}{
+		{
+			name:       "CRL reason code critical",
+			path:       "crlReasonCodeCrit.pem",
+			want:       lint.Error,
+			wantSubStr: "MUST NOT be marked as critical",
+		},
+		{
+			name: "CRL with reason code 5",
+			path: "crlWithReasonCode5.pem",
+			want: lint.Pass,
+		},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			gotStatus := test.TestRevocationListLint(t, "e_cab_crl_reason_code_not_critical", tc.path)
+			if tc.want != gotStatus.Status {
+				t.Errorf("%s: expected %s, got %s", tc.path, tc.want, gotStatus.Status)
+			}
+			if !strings.Contains(gotStatus.Details, tc.wantSubStr) {
+				t.Errorf("%s: expected %s, got %s", tc.path, tc.wantSubStr, gotStatus.Details)
+			}
+		})
+	}
+
+}

v3/lints/cabf_br/lint_cabf_crl_valid_reason_codes.go

@@ -0,0 +1,74 @@
+package cabf_br
+
+/*
+ * ZLint Copyright 2023 Regents of the University of Michigan
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy
+ * of the License at http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+import (
+	"github.com/zmap/zcrypto/x509"
+	"github.com/zmap/zlint/v3/lint"
+	"github.com/zmap/zlint/v3/util"
+)
+
+type crlHasValidReasonCode struct{}
+
+func init() {
+	lint.RegisterRevocationListLint(&lint.RevocationListLint{
+		LintMetadata: lint.LintMetadata{
+			Name:          "e_cab_crl_has_valid_reason_code",
+			Description:   "CRL Reason codes 1, 3, 4, 5, 9.",
+			Citation:      "BRs: 7.2.2",
+			Source:        lint.CABFBaselineRequirements,
+			EffectiveDate: util.CABFBRs_SC61_CRL_Date,
+		},
+		Lint: NewCrlHasValidReasonCode,
+	})
+}
+
+func NewCrlHasValidReasonCode() lint.RevocationListLintInterface {
+	return &crlHasValidReasonCode{}
+}
+
+func (l *crlHasValidReasonCode) CheckApplies(c *x509.RevocationList) bool {
+	for _, c := range c.RevokedCertificates {
+		if c.ReasonCode == nil {
+			continue
+		}
+		return true
+	}
+	return false
+}
+
+var validReasons = map[int]bool{
+	1: true,
+	3: true,
+	4: true,
+	5: true,
+	9: true,
+}
+
+func (l *crlHasValidReasonCode) Execute(c *x509.RevocationList) *lint.LintResult {
+	for _, c := range c.RevokedCertificates {
+		if c.ReasonCode == nil {
+			continue
+		}
+		code := *c.ReasonCode
+		if code == 0 {
+			return &lint.LintResult{Status: lint.Error, Details: "The reason code CRL entry extension SHOULD be absent instead of using the unspecified (0) reasonCode value."}
+		}
+		if _, ok := validReasons[code]; !ok {
+			return &lint.LintResult{Status: lint.Error, Details: "Reason code not included in BR: 7.2.2"}
+		}
+	}
+	return &lint.LintResult{Status: lint.Pass}
+}

v3/lints/cabf_br/lint_cabf_crl_valid_reason_codes_test.go

@@ -0,0 +1,76 @@
+package cabf_br
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/zmap/zlint/v3/lint"
+	"github.com/zmap/zlint/v3/test"
+)
+
+/*
+ * ZLint Copyright 2021 Regents of the University of Michigan
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy
+ * of the License at http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+func TestCrlValidReasonCodes(t *testing.T) {
+	t.Parallel()
+	testCases := []struct {
+		name       string
+		path       string
+		want       lint.LintStatus
+		wantSubStr string
+	}{
+		{
+			name:       "CRL with reason code 0",
+			path:       "crlWithReasonCode0.pem",
+			want:       lint.Error,
+			wantSubStr: "The reason code CRL entry extension SHOULD be absent instead of using the unspecified",
+		},
+		{
+			// This test case is significant since reason code 2 is not allowed by CABF
+			name:       "CRL with reason code 2",
+			path:       "crlWithReasonCode2.pem",
+			want:       lint.Error,
+			wantSubStr: "Reason code not included in BR: 7.2.2",
+		},
+		{
+			name: "CRL with reason code 5",
+			path: "crlWithReasonCode5.pem",
+			want: lint.Pass,
+		},
+		{
+			name:       "CRL with reason code 7",
+			path:       "crlWithReasonCode7.pem",
+			want:       lint.Error,
+			wantSubStr: "Reason code not included in BR: 7.2.2",
+		},
+		{
+			name: "CRL thisUpdate before enforcement",
+			path: "crlThisUpdate20230505.pem",
+			want: lint.NE,
+		},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			gotStatus := test.TestRevocationListLint(t, "e_cab_crl_has_valid_reason_code", tc.path)
+			if tc.want != gotStatus.Status {
+				t.Errorf("%s: expected %s, got %s", tc.path, tc.want, gotStatus.Status)
+			}
+			if !strings.Contains(gotStatus.Details, tc.wantSubStr) {
+				t.Errorf("%s: expected %s, got %s", tc.path, tc.wantSubStr, gotStatus.Details)
+			}
+		})
+	}
+}

v3/lints/rfc/lint_crl_valid_reason_codes.go

@@ -0,0 +1,77 @@
+package rfc
+
+/*
+ * ZLint Copyright 2023 Regents of the University of Michigan
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy
+ * of the License at http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+import (
+	"github.com/zmap/zcrypto/x509"
+	"github.com/zmap/zlint/v3/lint"
+	"github.com/zmap/zlint/v3/util"
+)
+
+type crlHasValidReasonCode struct{}
+
+/*
+***********************************************
+RFC 5280: 5.3.1
+
+	CRL issuers are strongly
+	  encouraged to include meaningful reason codes in CRL entries;
+	  however, the reason code CRL entry extension SHOULD be absent instead
+	  of using the unspecified (0) reasonCode value.
+
+***********************************************
+*/
+func init() {
+	lint.RegisterRevocationListLint(&lint.RevocationListLint{
+		LintMetadata: lint.LintMetadata{
+			Name:          "e_crl_has_valid_reason_code",
+			Description:   "If CRL has a reason code, it must be in 5.3.1 and not be 0.",
+			Citation:      "RFC 5280: 5.3.1",
+			Source:        lint.RFC5280,
+			EffectiveDate: util.RFC5280Date,
+		},
+		Lint: NewCrlHasValidReasonCode,
+	})
+}
+
+func NewCrlHasValidReasonCode() lint.RevocationListLintInterface {
+	return &crlHasValidReasonCode{}
+}
+
+func (l *crlHasValidReasonCode) CheckApplies(c *x509.RevocationList) bool {
+	for _, c := range c.RevokedCertificates {
+		if c.ReasonCode == nil {
+			continue
+		}
+		return true
+	}
+	return false
+}
+
+func (l *crlHasValidReasonCode) Execute(c *x509.RevocationList) *lint.LintResult {
+	for _, c := range c.RevokedCertificates {
+		if c.ReasonCode == nil {
+			continue
+		}
+		code := *c.ReasonCode
+		if code == 0 {
+			return &lint.LintResult{Status: lint.Error, Details: "The reason code CRL entry extension SHOULD be absent instead of using the unspecified (0) reasonCode value."}
+		}
+		if code == 7 || code > 10 {
+			return &lint.LintResult{Status: lint.Error, Details: "Reason code not included in RFC 5280: 5.3.1"}
+		}
+	}
+	return &lint.LintResult{Status: lint.Pass}
+}