Matthias Andreas Benkard | 832a54e | 2019-01-29 09:27:38 +0100 | [diff] [blame] | 1 | /* |
| 2 | Copyright 2017 The Kubernetes Authors. |
| 3 | |
| 4 | Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | you may not use this file except in compliance with the License. |
| 6 | You may obtain a copy of the License at |
| 7 | |
| 8 | http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | |
| 10 | Unless required by applicable law or agreed to in writing, software |
| 11 | distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | See the License for the specific language governing permissions and |
| 14 | limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package policy |
| 18 | |
| 19 | import ( |
| 20 | "strings" |
| 21 | |
| 22 | "k8s.io/apiserver/pkg/apis/audit" |
| 23 | "k8s.io/apiserver/pkg/authorization/authorizer" |
| 24 | ) |
| 25 | |
| 26 | const ( |
| 27 | // DefaultAuditLevel is the default level to audit at, if no policy rules are matched. |
| 28 | DefaultAuditLevel = audit.LevelNone |
| 29 | ) |
| 30 | |
| 31 | // Checker exposes methods for checking the policy rules. |
| 32 | type Checker interface { |
| 33 | // Check the audit level for a request with the given authorizer attributes. |
| 34 | LevelAndStages(authorizer.Attributes) (audit.Level, []audit.Stage) |
| 35 | } |
| 36 | |
| 37 | // NewChecker creates a new policy checker. |
| 38 | func NewChecker(policy *audit.Policy) Checker { |
| 39 | for i, rule := range policy.Rules { |
| 40 | policy.Rules[i].OmitStages = unionStages(policy.OmitStages, rule.OmitStages) |
| 41 | } |
| 42 | return &policyChecker{*policy} |
| 43 | } |
| 44 | |
| 45 | func unionStages(stageLists ...[]audit.Stage) []audit.Stage { |
| 46 | m := make(map[audit.Stage]bool) |
| 47 | for _, sl := range stageLists { |
| 48 | for _, s := range sl { |
| 49 | m[s] = true |
| 50 | } |
| 51 | } |
| 52 | result := make([]audit.Stage, 0, len(m)) |
| 53 | for key := range m { |
| 54 | result = append(result, key) |
| 55 | } |
| 56 | return result |
| 57 | } |
| 58 | |
| 59 | // FakeChecker creates a checker that returns a constant level for all requests (for testing). |
| 60 | func FakeChecker(level audit.Level, stage []audit.Stage) Checker { |
| 61 | return &fakeChecker{level, stage} |
| 62 | } |
| 63 | |
| 64 | type policyChecker struct { |
| 65 | audit.Policy |
| 66 | } |
| 67 | |
| 68 | func (p *policyChecker) LevelAndStages(attrs authorizer.Attributes) (audit.Level, []audit.Stage) { |
| 69 | for _, rule := range p.Rules { |
| 70 | if ruleMatches(&rule, attrs) { |
| 71 | return rule.Level, rule.OmitStages |
| 72 | } |
| 73 | } |
| 74 | return DefaultAuditLevel, p.OmitStages |
| 75 | } |
| 76 | |
| 77 | // Check whether the rule matches the request attrs. |
| 78 | func ruleMatches(r *audit.PolicyRule, attrs authorizer.Attributes) bool { |
| 79 | user := attrs.GetUser() |
| 80 | if len(r.Users) > 0 { |
| 81 | if user == nil || !hasString(r.Users, user.GetName()) { |
| 82 | return false |
| 83 | } |
| 84 | } |
| 85 | if len(r.UserGroups) > 0 { |
| 86 | if user == nil { |
| 87 | return false |
| 88 | } |
| 89 | matched := false |
| 90 | for _, group := range user.GetGroups() { |
| 91 | if hasString(r.UserGroups, group) { |
| 92 | matched = true |
| 93 | break |
| 94 | } |
| 95 | } |
| 96 | if !matched { |
| 97 | return false |
| 98 | } |
| 99 | } |
| 100 | if len(r.Verbs) > 0 { |
| 101 | if !hasString(r.Verbs, attrs.GetVerb()) { |
| 102 | return false |
| 103 | } |
| 104 | } |
| 105 | |
| 106 | if len(r.Namespaces) > 0 || len(r.Resources) > 0 { |
| 107 | return ruleMatchesResource(r, attrs) |
| 108 | } |
| 109 | |
| 110 | if len(r.NonResourceURLs) > 0 { |
| 111 | return ruleMatchesNonResource(r, attrs) |
| 112 | } |
| 113 | |
| 114 | return true |
| 115 | } |
| 116 | |
| 117 | // Check whether the rule's non-resource URLs match the request attrs. |
| 118 | func ruleMatchesNonResource(r *audit.PolicyRule, attrs authorizer.Attributes) bool { |
| 119 | if attrs.IsResourceRequest() { |
| 120 | return false |
| 121 | } |
| 122 | |
| 123 | path := attrs.GetPath() |
| 124 | for _, spec := range r.NonResourceURLs { |
| 125 | if pathMatches(path, spec) { |
| 126 | return true |
| 127 | } |
| 128 | } |
| 129 | |
| 130 | return false |
| 131 | } |
| 132 | |
| 133 | // Check whether the path matches the path specification. |
| 134 | func pathMatches(path, spec string) bool { |
| 135 | // Allow wildcard match |
| 136 | if spec == "*" { |
| 137 | return true |
| 138 | } |
| 139 | // Allow exact match |
| 140 | if spec == path { |
| 141 | return true |
| 142 | } |
| 143 | // Allow a trailing * subpath match |
| 144 | if strings.HasSuffix(spec, "*") && strings.HasPrefix(path, strings.TrimRight(spec, "*")) { |
| 145 | return true |
| 146 | } |
| 147 | return false |
| 148 | } |
| 149 | |
| 150 | // Check whether the rule's resource fields match the request attrs. |
| 151 | func ruleMatchesResource(r *audit.PolicyRule, attrs authorizer.Attributes) bool { |
| 152 | if !attrs.IsResourceRequest() { |
| 153 | return false |
| 154 | } |
| 155 | |
| 156 | if len(r.Namespaces) > 0 { |
| 157 | if !hasString(r.Namespaces, attrs.GetNamespace()) { // Non-namespaced resources use the empty string. |
| 158 | return false |
| 159 | } |
| 160 | } |
| 161 | if len(r.Resources) == 0 { |
| 162 | return true |
| 163 | } |
| 164 | |
| 165 | apiGroup := attrs.GetAPIGroup() |
| 166 | resource := attrs.GetResource() |
| 167 | subresource := attrs.GetSubresource() |
| 168 | combinedResource := resource |
| 169 | // If subresource, the resource in the policy must match "(resource)/(subresource)" |
| 170 | if subresource != "" { |
| 171 | combinedResource = resource + "/" + subresource |
| 172 | } |
| 173 | |
| 174 | name := attrs.GetName() |
| 175 | |
| 176 | for _, gr := range r.Resources { |
| 177 | if gr.Group == apiGroup { |
| 178 | if len(gr.Resources) == 0 { |
| 179 | return true |
| 180 | } |
| 181 | for _, res := range gr.Resources { |
| 182 | if len(gr.ResourceNames) == 0 || hasString(gr.ResourceNames, name) { |
| 183 | // match "*" |
| 184 | if res == combinedResource || res == "*" { |
| 185 | return true |
| 186 | } |
| 187 | // match "*/subresource" |
| 188 | if len(subresource) > 0 && strings.HasPrefix(res, "*/") && subresource == strings.TrimLeft(res, "*/") { |
| 189 | return true |
| 190 | } |
| 191 | // match "resource/*" |
| 192 | if strings.HasSuffix(res, "/*") && resource == strings.TrimRight(res, "/*") { |
| 193 | return true |
| 194 | } |
| 195 | } |
| 196 | } |
| 197 | } |
| 198 | } |
| 199 | return false |
| 200 | } |
| 201 | |
| 202 | // Utility function to check whether a string slice contains a string. |
| 203 | func hasString(slice []string, value string) bool { |
| 204 | for _, s := range slice { |
| 205 | if s == value { |
| 206 | return true |
| 207 | } |
| 208 | } |
| 209 | return false |
| 210 | } |
| 211 | |
| 212 | type fakeChecker struct { |
| 213 | level audit.Level |
| 214 | stage []audit.Stage |
| 215 | } |
| 216 | |
| 217 | func (f *fakeChecker) LevelAndStages(_ authorizer.Attributes) (audit.Level, []audit.Stage) { |
| 218 | return f.level, f.stage |
| 219 | } |