From b3218fbcff0aa27c6df4ecd8458a1874ba37a08f Mon Sep 17 00:00:00 2001 From: Tiago Silva Date: Thu, 1 Aug 2024 19:07:35 +0100 Subject: [PATCH] [kube] fix greedy deny rule blocking namespace list when blocking other resources (#44893) * [kube] fix greedy deny rule blocking namespace list when blocking other resources This PR fixes an edge case where the deny rule for blocking access to a resource becomes greedy and blocks access to the whole namespace. eg: ``` allow: kubernetes_labels: '*': '*' kubernetes_resources: - kind: '*' name: '*' namespace: '*' verbs: - '*' deny: kubernetes_resources: - kind: secret name: '*' namespace: '*' verbs: - '*' ``` With the example above, access to secrets must be blocked but the user is allowed to access every other resource in any namespace. The previous model was greedy and blocked access to namespace list. * add extra test * handle comments --- lib/kube/proxy/forwarder.go | 4 +- lib/services/role.go | 2 +- lib/utils/replace.go | 6 +- lib/utils/replace_test.go | 116 +++++++++++++++++++++++++++++++++++- 4 files changed, 121 insertions(+), 7 deletions(-) diff --git a/lib/kube/proxy/forwarder.go b/lib/kube/proxy/forwarder.go index 3ad776eda6234..6d0f3ed5a277b 100644 --- a/lib/kube/proxy/forwarder.go +++ b/lib/kube/proxy/forwarder.go @@ -1124,14 +1124,14 @@ func matchKubernetesResource(resource types.KubernetesResource, allowed, denied // utils.KubeResourceMatchesRegex checks if the resource.Kind is strictly equal // to each entry and validates if the Name and Namespace fields matches the // regex allowed by each entry. - result, err := utils.KubeResourceMatchesRegex(resource, denied) + result, err := utils.KubeResourceMatchesRegex(resource, denied, types.Deny) if err != nil { return false, trace.Wrap(err) } else if result { return false, nil } - result, err = utils.KubeResourceMatchesRegex(resource, allowed) + result, err = utils.KubeResourceMatchesRegex(resource, allowed, types.Allow) if err != nil { return false, trace.Wrap(err) } diff --git a/lib/services/role.go b/lib/services/role.go index 85ef239e9b85a..5d600a63ff2a2 100644 --- a/lib/services/role.go +++ b/lib/services/role.go @@ -2258,7 +2258,7 @@ func NewKubernetesResourceMatcher(resource types.KubernetesResource) *Kubernetes // Match matches a Kubernetes Resource against provided role and condition. func (m *KubernetesResourceMatcher) Match(role types.Role, condition types.RoleConditionType) (bool, error) { - result, err := utils.KubeResourceMatchesRegex(m.resource, role.GetKubeResources(condition)) + result, err := utils.KubeResourceMatchesRegex(m.resource, role.GetKubeResources(condition), condition) return result, trace.Wrap(err) } diff --git a/lib/utils/replace.go b/lib/utils/replace.go index 8c49934c4ddc5..22632ab6ca80b 100644 --- a/lib/utils/replace.go +++ b/lib/utils/replace.go @@ -145,14 +145,14 @@ const ( // input is the resource we are checking for access. // resources is a list of resources that the user has access to - collected from // their roles that match the Kubernetes cluster where the resource is defined. -func KubeResourceMatchesRegex(input types.KubernetesResource, resources []types.KubernetesResource) (bool, error) { +// cond is the deny or allow condition of the role that we are evaluating. +func KubeResourceMatchesRegex(input types.KubernetesResource, resources []types.KubernetesResource, cond types.RoleConditionType) (bool, error) { if len(input.Verbs) != 1 { return false, trace.BadParameter("only one verb is supported, input: %v", input.Verbs) } // isClusterWideResource is true if the resource is cluster-wide, e.g. a // namespace resource or a clusterrole. isClusterWideResource := slices.Contains(types.KubernetesClusterWideResourceKinds, input.Kind) - verb := input.Verbs[0] // If the user is list/read/watch a namespace, they should be able to see the // namespace they have resources defined for. @@ -187,7 +187,7 @@ func KubeResourceMatchesRegex(input types.KubernetesResource, resources []types. if ok, err := MatchString(input.Namespace, resource.Name); err != nil || ok { return ok, trace.Wrap(err) } - case targetsReadOnlyNamespace && resource.Kind != types.KindKubeNamespace && resource.Namespace != "": + case targetsReadOnlyNamespace && cond == types.Allow && resource.Kind != types.KindKubeNamespace && resource.Namespace != "": // If the user requests a read-only namespace get/list/watch, they should // be able to see the list of namespaces they have resources defined in. // This means that if the user has access to pods in the "foo" namespace, diff --git a/lib/utils/replace_test.go b/lib/utils/replace_test.go index 09a88bc1a359d..7ba15f4d47f0d 100644 --- a/lib/utils/replace_test.go +++ b/lib/utils/replace_test.go @@ -158,6 +158,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { name string input types.KubernetesResource resources []types.KubernetesResource + action types.RoleConditionType matches bool assert require.ErrorAssertionFunc }{ @@ -176,8 +177,102 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.Error, + action: types.Allow, matches: false, }, + { + name: "list namespace matches resource", + input: types.KubernetesResource{ + Kind: types.KindNamespace, + Verbs: []string{types.KubeVerbList}, + }, + resources: []types.KubernetesResource{ + { + Kind: types.KindKubeSecret, + Namespace: "*", + Name: "*", + Verbs: []string{types.Wildcard}, + }, + }, + assert: require.NoError, + action: types.Allow, + matches: true, + }, + { + name: "list namespace doesn't match denying secrets", + input: types.KubernetesResource{ + Kind: types.KindNamespace, + Verbs: []string{types.KubeVerbList}, + }, + resources: []types.KubernetesResource{ + { + Kind: types.KindKubeSecret, + Namespace: "*", + Name: "*", + Verbs: []string{types.Wildcard}, + }, + }, + assert: require.NoError, + action: types.Deny, + matches: false, + }, + { + name: "get namespace match denying everything", + input: types.KubernetesResource{ + Kind: types.KindNamespace, + Name: "default", + Verbs: []string{types.KubeVerbGet}, + }, + resources: []types.KubernetesResource{ + { + Kind: types.Wildcard, + Namespace: types.Wildcard, + Name: types.Wildcard, + Verbs: []string{types.Wildcard}, + }, + }, + assert: require.NoError, + action: types.Deny, + matches: true, + }, + { + name: "get namespace doesn't match denying secrets", + input: types.KubernetesResource{ + Kind: types.KindNamespace, + Name: "default", + Verbs: []string{types.KubeVerbGet}, + }, + resources: []types.KubernetesResource{ + { + Kind: types.KindKubeSecret, + Namespace: "*", + Name: "*", + Verbs: []string{types.Wildcard}, + }, + }, + assert: require.NoError, + action: types.Deny, + matches: false, + }, + { + name: "get secret matches denying secrets", + input: types.KubernetesResource{ + Kind: types.KindKubeSecret, + Name: "default", + Verbs: []string{types.KubeVerbGet}, + }, + resources: []types.KubernetesResource{ + { + Kind: types.KindKubeSecret, + Namespace: "*", + Name: "*", + Verbs: []string{types.Wildcard}, + }, + }, + assert: require.NoError, + action: types.Deny, + matches: true, + }, { name: "input matches single resource with wildcard verb", input: types.KubernetesResource{ @@ -195,6 +290,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: true, }, { @@ -214,6 +310,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: true, }, { @@ -233,6 +330,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: false, }, { @@ -251,6 +349,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: false, }, { @@ -282,6 +381,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: true, }, { @@ -301,6 +401,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: true, }, { @@ -320,6 +421,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: false, }, { @@ -338,6 +440,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { Verbs: []string{types.Wildcard}, }, }, + action: types.Allow, assert: require.Error, }, { @@ -355,6 +458,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { Name: "podname", }, }, + action: types.Allow, assert: require.NoError, }, { @@ -372,6 +476,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: true, }, { @@ -390,6 +495,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: true, }, { @@ -408,6 +514,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: false, }, { @@ -426,6 +533,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: true, }, @@ -445,6 +553,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: false, }, @@ -464,6 +573,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: true, }, { @@ -482,6 +592,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: false, }, @@ -501,6 +612,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: true, }, { @@ -519,6 +631,7 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: false, }, { @@ -543,12 +656,13 @@ func TestKubeResourceMatchesRegex(t *testing.T) { }, }, assert: require.NoError, + action: types.Allow, matches: false, }, } for _, tt := range tests { t.Run(tt.name, func(t *testing.T) { - got, err := KubeResourceMatchesRegex(tt.input, tt.resources) + got, err := KubeResourceMatchesRegex(tt.input, tt.resources, tt.action) tt.assert(t, err) require.Equal(t, tt.matches, got) })