feat(oidc): disable minimum parameter entropy (#5495)

This allows disabling the minimum parameter entropy checks.

Signed-off-by: James Elliott <james-d-elliott@users.noreply.github.com>

docs/content/en/configuration/identity-providers/openid-connect/provider.md

@@ -305,6 +305,8 @@ make certain scenarios less secure. It is highly encouraged that if your OpenID
 these parameters or sends parameters with a lower length than the default that they implement a change rather than
 changing this value.
 
+This restriction can also be disabled entirely when set to `-1`.
+
 ### enforce_pkce
 
 {{< confkey type="string" default="public_clients_only" required="no" >}}

internal/configuration/validator/const.go

@@ -147,8 +147,10 @@ const (
 	errFmtOIDCProviderNoPrivateKey            = "identity_providers: oidc: option `issuer_private_keys` or 'issuer_private_key' is required"
 	errFmtOIDCProviderEnforcePKCEInvalidValue = "identity_providers: oidc: option 'enforce_pkce' must be 'never', " +
 		"'public_clients_only' or 'always', but it's configured as '%s'"
-	errFmtOIDCProviderInsecureParameterEntropy = "openid connect provider: SECURITY ISSUE - minimum parameter entropy is " +
+	errFmtOIDCProviderInsecureParameterEntropy = "identity_providers: oidc: option 'minimum_parameter_entropy' is " +
-		"configured to an unsafe value, it should be above 8 but it's configured to %d"
+		"configured to an unsafe and insecure value, it should at least be %d but it's configured to %d"
+	errFmtOIDCProviderInsecureDisabledParameterEntropy = "identity_providers: oidc: option 'minimum_parameter_entropy' is " +
+		"disabled which is considered unsafe and insecure"
 	errFmtOIDCProviderPrivateKeysInvalid                 = "identity_providers: oidc: issuer_private_keys: key #%d: option 'key' must be a valid private key but the provided data is malformed as it's missing the public key bits"
 	errFmtOIDCProviderPrivateKeysCalcThumbprint          = "identity_providers: oidc: issuer_private_keys: key #%d: option 'key' failed to calculate thumbprint to configure key id value: %w"
 	errFmtOIDCProviderPrivateKeysKeyIDLength             = "identity_providers: oidc: issuer_private_keys: key #%d with key id '%s': option `key_id` must be 100 characters or less"

internal/configuration/validator/identity_providers.go

@@ -10,6 +10,8 @@ import (
 	"strings"
 	"time"
 
+	"github.com/ory/fosite"
+
 	"github.com/authelia/authelia/v4/internal/configuration/schema"
 	"github.com/authelia/authelia/v4/internal/oidc"
 	"github.com/authelia/authelia/v4/internal/utils"
@@ -31,8 +33,13 @@ func validateOIDC(config *schema.OpenIDConnect, val *schema.StructValidator) {
 
 	sort.Sort(oidc.SortedSigningAlgs(config.Discovery.ResponseObjectSigningAlgs))
 
-	if config.MinimumParameterEntropy != 0 && config.MinimumParameterEntropy < 8 {
+	switch {
-		val.PushWarning(fmt.Errorf(errFmtOIDCProviderInsecureParameterEntropy, config.MinimumParameterEntropy))
+	case config.MinimumParameterEntropy == -1:
+		val.PushWarning(fmt.Errorf(errFmtOIDCProviderInsecureDisabledParameterEntropy))
+	case config.MinimumParameterEntropy <= 0:
+		config.MinimumParameterEntropy = fosite.MinParameterEntropy
+	case config.MinimumParameterEntropy < fosite.MinParameterEntropy:
+		val.PushWarning(fmt.Errorf(errFmtOIDCProviderInsecureParameterEntropy, fosite.MinParameterEntropy, config.MinimumParameterEntropy))
 	}
 
 	switch config.EnforcePKCE {

internal/configuration/validator/identity_providers_test.go

@@ -504,13 +504,59 @@ func TestShouldRaiseErrorOnCertificateNotValid(t *testing.T) {
 	assert.EqualError(t, validator.Errors()[0], "identity_providers: oidc: issuer_private_keys: key #1 with key id 'bf1e10': option 'certificate_chain' does not appear to contain the public key for the private key provided by option 'key'")
 }
 
-func TestValidateIdentityProvidersShouldRaiseWarningOnSecurityIssue(t *testing.T) {
+func TestValidateIdentityProvidersOpenIDConnectMinimumParameterEntropy(t *testing.T) {
+	testCases := []struct {
+		name     string
+		have     int
+		expected int
+		warnings []string
+		errors   []string
+	}{
+		{
+			"ShouldNotOverrideCustomValue",
+			20,
+			20,
+			nil,
+			nil,
+		},
+		{
+			"ShouldSetDefault",
+			0,
+			8,
+			nil,
+			nil,
+		},
+		{
+			"ShouldSetDefaultNegative",
+			-2,
+			8,
+			nil,
+			nil,
+		},
+		{
+			"ShouldAllowDisabledAndWarn",
+			-1,
+			-1,
+			[]string{"identity_providers: oidc: option 'minimum_parameter_entropy' is disabled which is considered unsafe and insecure"},
+			nil,
+		},
+		{
+			"ShouldWarnOnTooLow",
+			2,
+			2,
+			[]string{"identity_providers: oidc: option 'minimum_parameter_entropy' is configured to an unsafe and insecure value, it should at least be 8 but it's configured to 2"},
+			nil,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
 			validator := schema.NewStructValidator()
 			config := &schema.IdentityProviders{
 				OIDC: &schema.OpenIDConnect{
 					HMACSecret:              "abc",
 					IssuerPrivateKey:        keyRSA2048,
-			MinimumParameterEntropy: 1,
+					MinimumParameterEntropy: tc.have,
 					Clients: []schema.OpenIDConnectClient{
 						{
 							ID:     "good_id",
@@ -526,10 +572,29 @@ func TestValidateIdentityProvidersShouldRaiseWarningOnSecurityIssue(t *testing.T
 
 			ValidateIdentityProviders(config, validator)
 
-	assert.Len(t, validator.Errors(), 0)
+			assert.Equal(t, tc.expected, config.OIDC.MinimumParameterEntropy)
-	require.Len(t, validator.Warnings(), 1)
 
-	assert.EqualError(t, validator.Warnings()[0], "openid connect provider: SECURITY ISSUE - minimum parameter entropy is configured to an unsafe value, it should be above 8 but it's configured to 1")
+			if n := len(tc.warnings); n == 0 {
+				assert.Len(t, validator.Warnings(), 0)
+			} else {
+				require.Len(t, validator.Warnings(), n)
+
+				for i := 0; i < n; i++ {
+					assert.EqualError(t, validator.Warnings()[i], tc.warnings[i])
+				}
+			}
+
+			if n := len(tc.errors); n == 0 {
+				assert.Len(t, validator.Errors(), 0)
+			} else {
+				require.Len(t, validator.Errors(), n)
+
+				for i := 0; i < n; i++ {
+					assert.EqualError(t, validator.Errors()[i], tc.errors[i])
+				}
+			}
+		})
+	}
 }
 
 func TestValidateIdentityProvidersShouldRaiseErrorsOnInvalidClientTypes(t *testing.T) {