package evaluator

import (
	"regexp"
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"

	"github.com/pomerium/pomerium/config"
)

// These certificates can be regenerated by running:
//
//	go run ./gen-test-certs.go
//
// (Copy and paste the output here.)
const (
	testCA = `
-----BEGIN CERTIFICATE-----
MIIBaDCCAQ6gAwIBAgICEAAwCgYIKoZIzj0EAwIwGjEYMBYGA1UEAxMPVHJ1c3Rl
ZCBSb290IENBMCAYDzAwMDEwMTAxMDAwMDAwWhcNMzMwODA3MTgwMzIxWjAaMRgw
FgYDVQQDEw9UcnVzdGVkIFJvb3QgQ0EwWTATBgcqhkjOPQIBBggqhkjOPQMBBwNC
AAR2/RkzmSK6paoeTKFx1Bd52ZCg29ulJlMxFdSZT8FlmmaK9mN6KWwO+NHYObiW
y3AQuoSTrZXlrlRW5ANvMI+io0IwQDAOBgNVHQ8BAf8EBAMCAQYwDwYDVR0TAQH/
BAUwAwEB/zAdBgNVHQ4EFgQUJGFVU2UOvOVgaY9YcCUiunGpiCQwCgYIKoZIzj0E
AwIDSAAwRQIhAMU5/NjpitOSbUobtjeOriPH8JRo9qy1iFyeVNAcdVvgAiAewq2A
PhgzWTw5F9PJg++9i+xGQTqHs3ZirG27cCjvhQ==
-----END CERTIFICATE-----
`
	testValidCert = `
-----BEGIN CERTIFICATE-----
MIIBYjCCAQigAwIBAgICEAEwCgYIKoZIzj0EAwIwGjEYMBYGA1UEAxMPVHJ1c3Rl
ZCBSb290IENBMCAYDzAwMDEwMTAxMDAwMDAwWhcNMzMwODA3MTgwMzIxWjAeMRww
GgYDVQQDExN0cnVzdGVkIGNsaWVudCBjZXJ0MFkwEwYHKoZIzj0CAQYIKoZIzj0D
AQcDQgAEcWa1Bz6mpsLnM1VD8gtzELjzjEp9Dopp/xWScFO9qtay5SBOeX+Ftr0O
8+/RkoKHzGgZ80gr6xQyUJL3MCwVZKM4MDYwEwYDVR0lBAwwCgYIKwYBBQUHAwIw
HwYDVR0jBBgwFoAUJGFVU2UOvOVgaY9YcCUiunGpiCQwCgYIKoZIzj0EAwIDSAAw
RQIgXM1ogmy0vcz4lYzji5X3In1n2GLOFNTgucFPkM0GtqgCIQCsXPs/0OjSFyDR
FBqAm1NqDJcxq685fS9t3VfHwapcVA==
-----END CERTIFICATE-----
`
	testUntrustedCert = `
-----BEGIN CERTIFICATE-----
MIIBZjCCAQygAwIBAgICEAEwCgYIKoZIzj0EAwIwHDEaMBgGA1UEAxMRVW50cnVz
dGVkIFJvb3QgQ0EwIBgPMDAwMTAxMDEwMDAwMDBaFw0zMzA4MDcxODAzMjFaMCAx
HjAcBgNVBAMTFXVudHJ1c3RlZCBjbGllbnQgY2VydDBZMBMGByqGSM49AgEGCCqG
SM49AwEHA0IABJxEIKqLhhMEm5XZXkT+p+hlC2TFyaW0HIZqoE9navJrAcUB8L2M
mVQ+/wLaCznJHLeSLn46uGH5p1hoGFqOrdajODA2MBMGA1UdJQQMMAoGCCsGAQUF
BwMCMB8GA1UdIwQYMBaAFIp2rlIiSnr33ea3cGyLsX4LEYwWMAoGCCqGSM49BAMC
A0gAMEUCIDtJIZJDcqIYaDXhZFs0nd0nHER8IGP9n4BBFMWewAb2AiEAlQyavOxw
iTQQxt0rXB4Ox5zWpU9q68+F9BGBkQKTsBs=
-----END CERTIFICATE-----
`
	testRevokedCert = `
-----BEGIN CERTIFICATE-----
MIIBYjCCAQigAwIBAgICEAIwCgYIKoZIzj0EAwIwGjEYMBYGA1UEAxMPVHJ1c3Rl
ZCBSb290IENBMCAYDzAwMDEwMTAxMDAwMDAwWhcNMzMwODA3MTgwMzIxWjAeMRww
GgYDVQQDExNyZXZva2VkIGNsaWVudCBjZXJ0MFkwEwYHKoZIzj0CAQYIKoZIzj0D
AQcDQgAEcnoO4EM72C7xL31RE9e6m9YJYyF6E4JloASECd8mdiXPlMXIjq8MZHB5
28mFAVQNE7erAtBftID1SbuY4IpXxqM4MDYwEwYDVR0lBAwwCgYIKwYBBQUHAwIw
HwYDVR0jBBgwFoAUJGFVU2UOvOVgaY9YcCUiunGpiCQwCgYIKoZIzj0EAwIDSAAw
RQIgUUETSO064YIu+VKnyRb0yBnNTjXLy3TvGuYgZI8VX0YCIQDd0gyNEC5YLvRN
njxfnLoimp+TzTVzvsCokUbNSNRKJA==
-----END CERTIFICATE-----
`
	testCRL = `
-----BEGIN X509 CRL-----
MIHeMIGFAgEBMAoGCCqGSM49BAMCMBoxGDAWBgNVBAMTD1RydXN0ZWQgUm9vdCBD
QRgPMDAwMTAxMDEwMDAwMDBaMBUwEwICEAIXDTIzMDgxMDE4MDMyMVqgMDAuMB8G
A1UdIwQYMBaAFCRhVVNlDrzlYGmPWHAlIrpxqYgkMAsGA1UdFAQEAgIgADAKBggq
hkjOPQQDAgNIADBFAiEAumtTtjiQt1VsbsEnyr+xbpK0KmzKvkpxIVgE1M9CND0C
IA8zx5clcaGIT5xRnBLZW7RwA37IOmB+7zjAuJQpmKKp
-----END X509 CRL-----
`
	testIntermediateCA = `
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
`
	testValidIntermediateCert = `
-----BEGIN CERTIFICATE-----
MIIBdTCCARqgAwIBAgICEAAwCgYIKoZIzj0EAwIwIjEgMB4GA1UEAxMXVHJ1c3Rl
ZCBJbnRlcm1lZGlhdGUgQ0EwIBgPMDAwMTAxMDEwMDAwMDBaFw0zMzA4MDcxODAz
MjFaMCgxJjAkBgNVBAMTHWNsaWVudCBjZXJ0IGZyb20gaW50ZXJtZWRpYXRlMFkw
EwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE5SVyYjNRuuFXGjEmCcuVtMq7e2bmndPK
bRJ7lJ5cc0kZSoNJes5wXOtGRFbx3+admRHq+w1XEBXOe+yRUB8kdKM4MDYwEwYD
VR0lBAwwCgYIKwYBBQUHAwIwHwYDVR0jBBgwFoAUKRjZnCyzN7x4jgA2Bjw0C/AI
ZMgwCgYIKoZIzj0EAwIDSQAwRgIhAMj0O2wDRLoxGIPUDOmUfYxmxglOecQhSkWO
NBtItSxmAiEAy0XCzvpL6XOZU3zxyCjTdJQa2RiC6YnypMaCaETzCaU=
-----END CERTIFICATE-----
`
	testValidCertWithDNSSANs = `
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
`
	testValidCertWithEmailSAN = `
-----BEGIN CERTIFICATE-----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=
-----END CERTIFICATE-----
`
	testValidCertWithIPSAN = `
-----BEGIN CERTIFICATE-----
MIIBbTCCAROgAwIBAgICEAYwCgYIKoZIzj0EAwIwGjEYMBYGA1UEAxMPVHJ1c3Rl
ZCBSb290IENBMCAYDzAwMDEwMTAxMDAwMDAwWhcNMzMwODA3MTgwMzIxWjAYMRYw
FAYDVQQDEw1jbGllbnQgY2VydCA1MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE
6+9BE+aomrR2Mdnx4iFY63t0hsVD6rYaHBW1b9roFQX6Cor4YeUfkEEF4LrGeAyb
wcqb6G1ExgNyjEh10Ai1M6NJMEcwEwYDVR0lBAwwCgYIKwYBBQUHAwIwHwYDVR0j
BBgwFoAUJGFVU2UOvOVgaY9YcCUiunGpiCQwDwYDVR0RBAgwBocEwKgKCjAKBggq
hkjOPQQDAgNIADBFAiEA/mq32YZZAacOH/P/wjvfD1n74DD/GkhW4kfS72Z0oGQC
IAQ+L8E78JOLaPWXiL7WFpVrb0hOHkV2m9Qw4GB41mUN
-----END CERTIFICATE-----
`
	testValidCertWithURISAN = `
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
`
)

func Test_isValidClientCertificate(t *testing.T) {
	t.Parallel()

	var noConstraints ClientCertConstraints
	t.Run("no ca", func(t *testing.T) {
		valid, err := isValidClientCertificate(
			"", "", ClientCertificateInfo{Leaf: "WHATEVER!"}, noConstraints)
		assert.NoError(t, err, "should not return an error")
		assert.True(t, valid, "should return true")
	})
	t.Run("no cert", func(t *testing.T) {
		valid, err := isValidClientCertificate(testCA, "", ClientCertificateInfo{}, noConstraints)
		assert.NoError(t, err, "should not return an error")
		assert.False(t, valid, "should return false")
	})
	t.Run("valid cert", func(t *testing.T) {
		valid, err := isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCert,
		}, noConstraints)
		assert.NoError(t, err, "should not return an error")
		assert.True(t, valid, "should return true")
	})
	t.Run("valid cert with intermediate", func(t *testing.T) {
		valid, err := isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented:     true,
			Leaf:          testValidIntermediateCert,
			Intermediates: testIntermediateCA,
		}, noConstraints)
		assert.NoError(t, err, "should not return an error")
		assert.True(t, valid, "should return true")
	})
	t.Run("valid cert missing intermediate", func(t *testing.T) {
		valid, err := isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented:     true,
			Leaf:          testValidIntermediateCert,
			Intermediates: "",
		}, noConstraints)
		assert.NoError(t, err, "should not return an error")
		assert.False(t, valid, "should return false")
	})
	t.Run("intermediate CA as root", func(t *testing.T) {
		valid, err := isValidClientCertificate(testIntermediateCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidIntermediateCert,
		}, noConstraints)
		assert.NoError(t, err, "should not return an error")
		assert.True(t, valid, "should return true")
	})
	t.Run("unsigned cert", func(t *testing.T) {
		valid, err := isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testUntrustedCert,
		}, noConstraints)
		assert.NoError(t, err, "should not return an error")
		assert.False(t, valid, "should return false")
	})
	t.Run("not a cert", func(t *testing.T) {
		valid, err := isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      "WHATEVER!",
		}, noConstraints)
		assert.Error(t, err, "should return an error")
		assert.False(t, valid, "should return false")
	})
	t.Run("revoked cert", func(t *testing.T) {
		revokedCertInfo := ClientCertificateInfo{
			Presented: true,
			Leaf:      testRevokedCert,
		}

		// The "revoked cert" should otherwise be valid (when no CRL is specified).
		valid, err := isValidClientCertificate(testCA, "", revokedCertInfo, noConstraints)
		assert.NoError(t, err, "should not return an error")
		assert.True(t, valid, "should return true")

		valid, err = isValidClientCertificate(testCA, testCRL, revokedCertInfo, noConstraints)
		assert.NoError(t, err, "should not return an error")
		assert.False(t, valid, "should return false")

		// Specifying a CRL containing the revoked cert should not affect other certs.
		valid, err = isValidClientCertificate(testCA, testCRL, ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCert,
		}, noConstraints)
		assert.NoError(t, err, "should not return an error")
		assert.True(t, valid, "should return true")
	})
	t.Run("chain too deep", func(t *testing.T) {
		valid, err := isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented:     true,
			Leaf:          testValidIntermediateCert,
			Intermediates: testIntermediateCA,
		}, ClientCertConstraints{MaxVerifyDepth: 1})
		assert.NoError(t, err, "should not return an error")
		assert.False(t, valid, "should return false")
	})
	t.Run("any SAN", func(t *testing.T) {
		matchAnySAN := ClientCertConstraints{SANMatchers: SANMatchers{
			config.SANTypeDNS:       regexp.MustCompile("^.*$"),
			config.SANTypeEmail:     regexp.MustCompile("^.*$"),
			config.SANTypeIPAddress: regexp.MustCompile("^.*$"),
			config.SANTypeURI:       regexp.MustCompile("^.*$"),
		}}

		valid, err := isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCert, // no SANs
		}, matchAnySAN)
		assert.NoError(t, err, "should not return an error")
		assert.False(t, valid, "should return false")

		valid, err = isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCertWithDNSSANs,
		}, matchAnySAN)
		assert.NoError(t, err, "should not return an error")
		assert.True(t, valid, "should return true")

		valid, err = isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCertWithEmailSAN,
		}, matchAnySAN)
		assert.NoError(t, err, "should not return an error")
		assert.True(t, valid, "should return true")

		valid, err = isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCertWithIPSAN,
		}, matchAnySAN)
		assert.NoError(t, err, "should not return an error")
		assert.True(t, valid, "should return true")

		valid, err = isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCertWithURISAN,
		}, matchAnySAN)
		assert.NoError(t, err, "should not return an error")
		assert.True(t, valid, "should return true")
	})
	t.Run("DNS SAN", func(t *testing.T) {
		valid, err := isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCertWithDNSSANs,
		}, ClientCertConstraints{SANMatchers: SANMatchers{
			config.SANTypeDNS: regexp.MustCompile(`^a\..*\.example\.com$`),
		}})
		assert.NoError(t, err, "should not return an error")
		assert.True(t, valid, "should return true")

		valid, err = isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCertWithDNSSANs,
		}, ClientCertConstraints{SANMatchers: SANMatchers{
			config.SANTypeEmail: regexp.MustCompile(`^a\..*\.example\.com$`), // mismatched type
		}})
		assert.NoError(t, err, "should not return an error")
		assert.False(t, valid, "should return false")
	})
	t.Run("email SAN", func(t *testing.T) {
		valid, err := isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCertWithEmailSAN,
		}, ClientCertConstraints{SANMatchers: SANMatchers{
			config.SANTypeEmail: regexp.MustCompile(`^.*@example\.com$`),
		}})
		assert.NoError(t, err, "should not return an error")
		assert.True(t, valid, "should return true")

		valid, err = isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCertWithEmailSAN,
		}, ClientCertConstraints{SANMatchers: SANMatchers{
			config.SANTypeIPAddress: regexp.MustCompile(`^.*@example\.com$`), // mismatched type
		}})
		assert.NoError(t, err, "should not return an error")
		assert.False(t, valid, "should return false")
	})
	t.Run("IP address SAN", func(t *testing.T) {
		valid, err := isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCertWithIPSAN,
		}, ClientCertConstraints{SANMatchers: SANMatchers{
			config.SANTypeIPAddress: regexp.MustCompile(`^192\.168\.10\..*$`),
		}})
		assert.NoError(t, err, "should not return an error")
		assert.True(t, valid, "should return true")

		valid, err = isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCertWithIPSAN,
		}, ClientCertConstraints{SANMatchers: SANMatchers{
			config.SANTypeURI: regexp.MustCompile(`^192\.168\.10\..*$`), // mismatched type
		}})
		assert.NoError(t, err, "should not return an error")
		assert.False(t, valid, "should return false")
	})
	t.Run("URI SAN", func(t *testing.T) {
		valid, err := isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCertWithURISAN,
		}, ClientCertConstraints{SANMatchers: SANMatchers{
			config.SANTypeURI: regexp.MustCompile(`^spiffe://example\.com/.*$`),
		}})
		assert.NoError(t, err, "should not return an error")
		assert.True(t, valid, "should return true")

		valid, err = isValidClientCertificate(testCA, "", ClientCertificateInfo{
			Presented: true,
			Leaf:      testValidCertWithURISAN,
		}, ClientCertConstraints{SANMatchers: SANMatchers{
			config.SANTypeDNS: regexp.MustCompile(`^spiffe://example\.com/.*$`), // mismatched type
		}})
		assert.NoError(t, err, "should not return an error")
		assert.False(t, valid, "should return false")
	})
}

func TestClientCertConstraintsFromConfig(t *testing.T) {
	t.Parallel()

	t.Run("default constraints", func(t *testing.T) {
		var s config.DownstreamMTLSSettings
		c, err := ClientCertConstraintsFromConfig(&s)
		assert.NoError(t, err)
		assert.Equal(t, &ClientCertConstraints{MaxVerifyDepth: 1}, c)
	})
	t.Run("no constraints", func(t *testing.T) {
		s := config.DownstreamMTLSSettings{
			MaxVerifyDepth: new(uint32),
		}
		c, err := ClientCertConstraintsFromConfig(&s)
		assert.NoError(t, err)
		assert.Equal(t, &ClientCertConstraints{}, c)
	})
	t.Run("larger max depth", func(t *testing.T) {
		depth := uint32(5)
		s := config.DownstreamMTLSSettings{
			MaxVerifyDepth: &depth,
		}
		c, err := ClientCertConstraintsFromConfig(&s)
		assert.NoError(t, err)
		assert.Equal(t, &ClientCertConstraints{MaxVerifyDepth: 5}, c)
	})
	t.Run("one SAN match", func(t *testing.T) {
		s := config.DownstreamMTLSSettings{
			MatchSubjectAltNames: []config.SANMatcher{
				{Type: config.SANTypeDNS, Pattern: `.*\.corp\.example\.com`},
			},
		}
		c, err := ClientCertConstraintsFromConfig(&s)
		assert.NoError(t, err)
		assert.Equal(t, &ClientCertConstraints{
			MaxVerifyDepth: 1,
			SANMatchers: SANMatchers{
				config.SANTypeDNS: regexp.MustCompile(`^(.*\.corp\.example\.com)$`),
			},
		}, c)
	})
	t.Run("multiple SAN matches", func(t *testing.T) {
		s := config.DownstreamMTLSSettings{
			MatchSubjectAltNames: []config.SANMatcher{
				{Type: config.SANTypeDNS, Pattern: `.*\.foo\.example\.com`},
				{Type: config.SANTypeDNS, Pattern: `.*\.bar\.example\.com`},
			},
		}
		c, err := ClientCertConstraintsFromConfig(&s)
		assert.NoError(t, err)
		assert.Equal(t, &ClientCertConstraints{
			MaxVerifyDepth: 1,
			SANMatchers: SANMatchers{
				config.SANTypeDNS: regexp.MustCompile(`^(.*\.foo\.example\.com)|(.*\.bar\.example\.com)$`),
			},
		}, c)
	})
	t.Run("multiple SAN matches", func(t *testing.T) {
		s := config.DownstreamMTLSSettings{
			MatchSubjectAltNames: []config.SANMatcher{
				{Type: config.SANTypeDNS, Pattern: `.*\.foo\.example\.com`},
				{Type: config.SANTypeEmail, Pattern: `.*@example\.com`},
			},
		}
		c, err := ClientCertConstraintsFromConfig(&s)
		assert.NoError(t, err)
		assert.Equal(t, &ClientCertConstraints{
			MaxVerifyDepth: 1,
			SANMatchers: SANMatchers{
				config.SANTypeDNS:   regexp.MustCompile(`^(.*\.foo\.example\.com)$`),
				config.SANTypeEmail: regexp.MustCompile(`^(.*@example\.com)$`),
			},
		}, c)
	})
	t.Run("bad SAN match expression", func(t *testing.T) {
		s := config.DownstreamMTLSSettings{
			MatchSubjectAltNames: []config.SANMatcher{
				{Type: config.SANTypeDNS, Pattern: "["},
			},
		}
		_, err := ClientCertConstraintsFromConfig(&s)
		require.Error(t, err)
	})
}