Matthias Andreas Benkard | 832a54e | 2019-01-29 09:27:38 +0100 | [diff] [blame] | 1 | /* |
| 2 | Copyright 2016 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 filters |
| 18 | |
| 19 | import ( |
| 20 | "errors" |
| 21 | "fmt" |
| 22 | "net/http" |
| 23 | "net/url" |
| 24 | "strings" |
| 25 | |
| 26 | "github.com/golang/glog" |
| 27 | |
| 28 | authenticationv1 "k8s.io/api/authentication/v1" |
| 29 | "k8s.io/api/core/v1" |
| 30 | "k8s.io/apimachinery/pkg/runtime" |
| 31 | "k8s.io/apiserver/pkg/audit" |
| 32 | "k8s.io/apiserver/pkg/authentication/serviceaccount" |
| 33 | "k8s.io/apiserver/pkg/authentication/user" |
| 34 | "k8s.io/apiserver/pkg/authorization/authorizer" |
| 35 | "k8s.io/apiserver/pkg/endpoints/handlers/responsewriters" |
| 36 | "k8s.io/apiserver/pkg/endpoints/request" |
| 37 | "k8s.io/apiserver/pkg/server/httplog" |
| 38 | ) |
| 39 | |
| 40 | // WithImpersonation is a filter that will inspect and check requests that attempt to change the user.Info for their requests |
| 41 | func WithImpersonation(handler http.Handler, a authorizer.Authorizer, s runtime.NegotiatedSerializer) http.Handler { |
| 42 | return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) { |
| 43 | impersonationRequests, err := buildImpersonationRequests(req.Header) |
| 44 | if err != nil { |
| 45 | glog.V(4).Infof("%v", err) |
| 46 | responsewriters.InternalError(w, req, err) |
| 47 | return |
| 48 | } |
| 49 | if len(impersonationRequests) == 0 { |
| 50 | handler.ServeHTTP(w, req) |
| 51 | return |
| 52 | } |
| 53 | |
| 54 | ctx := req.Context() |
| 55 | requestor, exists := request.UserFrom(ctx) |
| 56 | if !exists { |
| 57 | responsewriters.InternalError(w, req, errors.New("no user found for request")) |
| 58 | return |
| 59 | } |
| 60 | |
| 61 | // if groups are not specified, then we need to look them up differently depending on the type of user |
| 62 | // if they are specified, then they are the authority (including the inclusion of system:authenticated/system:unauthenticated groups) |
| 63 | groupsSpecified := len(req.Header[authenticationv1.ImpersonateGroupHeader]) > 0 |
| 64 | |
| 65 | // make sure we're allowed to impersonate each thing we're requesting. While we're iterating through, start building username |
| 66 | // and group information |
| 67 | username := "" |
| 68 | groups := []string{} |
| 69 | userExtra := map[string][]string{} |
| 70 | for _, impersonationRequest := range impersonationRequests { |
| 71 | actingAsAttributes := &authorizer.AttributesRecord{ |
| 72 | User: requestor, |
| 73 | Verb: "impersonate", |
| 74 | APIGroup: impersonationRequest.GetObjectKind().GroupVersionKind().Group, |
| 75 | Namespace: impersonationRequest.Namespace, |
| 76 | Name: impersonationRequest.Name, |
| 77 | ResourceRequest: true, |
| 78 | } |
| 79 | |
| 80 | switch impersonationRequest.GetObjectKind().GroupVersionKind().GroupKind() { |
| 81 | case v1.SchemeGroupVersion.WithKind("ServiceAccount").GroupKind(): |
| 82 | actingAsAttributes.Resource = "serviceaccounts" |
| 83 | username = serviceaccount.MakeUsername(impersonationRequest.Namespace, impersonationRequest.Name) |
| 84 | if !groupsSpecified { |
| 85 | // if groups aren't specified for a service account, we know the groups because its a fixed mapping. Add them |
| 86 | groups = serviceaccount.MakeGroupNames(impersonationRequest.Namespace) |
| 87 | } |
| 88 | |
| 89 | case v1.SchemeGroupVersion.WithKind("User").GroupKind(): |
| 90 | actingAsAttributes.Resource = "users" |
| 91 | username = impersonationRequest.Name |
| 92 | |
| 93 | case v1.SchemeGroupVersion.WithKind("Group").GroupKind(): |
| 94 | actingAsAttributes.Resource = "groups" |
| 95 | groups = append(groups, impersonationRequest.Name) |
| 96 | |
| 97 | case authenticationv1.SchemeGroupVersion.WithKind("UserExtra").GroupKind(): |
| 98 | extraKey := impersonationRequest.FieldPath |
| 99 | extraValue := impersonationRequest.Name |
| 100 | actingAsAttributes.Resource = "userextras" |
| 101 | actingAsAttributes.Subresource = extraKey |
| 102 | userExtra[extraKey] = append(userExtra[extraKey], extraValue) |
| 103 | |
| 104 | default: |
| 105 | glog.V(4).Infof("unknown impersonation request type: %v", impersonationRequest) |
| 106 | responsewriters.Forbidden(ctx, actingAsAttributes, w, req, fmt.Sprintf("unknown impersonation request type: %v", impersonationRequest), s) |
| 107 | return |
| 108 | } |
| 109 | |
| 110 | decision, reason, err := a.Authorize(actingAsAttributes) |
| 111 | if err != nil || decision != authorizer.DecisionAllow { |
| 112 | glog.V(4).Infof("Forbidden: %#v, Reason: %s, Error: %v", req.RequestURI, reason, err) |
| 113 | responsewriters.Forbidden(ctx, actingAsAttributes, w, req, reason, s) |
| 114 | return |
| 115 | } |
| 116 | } |
| 117 | |
| 118 | if !groupsSpecified && username != user.Anonymous { |
| 119 | // When impersonating a non-anonymous user, if no groups were specified |
| 120 | // include the system:authenticated group in the impersonated user info |
| 121 | groups = append(groups, user.AllAuthenticated) |
| 122 | } |
| 123 | |
| 124 | newUser := &user.DefaultInfo{ |
| 125 | Name: username, |
| 126 | Groups: groups, |
| 127 | Extra: userExtra, |
| 128 | } |
| 129 | req = req.WithContext(request.WithUser(ctx, newUser)) |
| 130 | |
| 131 | oldUser, _ := request.UserFrom(ctx) |
| 132 | httplog.LogOf(req, w).Addf("%v is acting as %v", oldUser, newUser) |
| 133 | |
| 134 | ae := request.AuditEventFrom(ctx) |
| 135 | audit.LogImpersonatedUser(ae, newUser) |
| 136 | |
| 137 | // clear all the impersonation headers from the request |
| 138 | req.Header.Del(authenticationv1.ImpersonateUserHeader) |
| 139 | req.Header.Del(authenticationv1.ImpersonateGroupHeader) |
| 140 | for headerName := range req.Header { |
| 141 | if strings.HasPrefix(headerName, authenticationv1.ImpersonateUserExtraHeaderPrefix) { |
| 142 | req.Header.Del(headerName) |
| 143 | } |
| 144 | } |
| 145 | |
| 146 | handler.ServeHTTP(w, req) |
| 147 | }) |
| 148 | } |
| 149 | |
| 150 | func unescapeExtraKey(encodedKey string) string { |
| 151 | key, err := url.PathUnescape(encodedKey) // Decode %-encoded bytes. |
| 152 | if err != nil { |
| 153 | return encodedKey // Always record extra strings, even if malformed/unencoded. |
| 154 | } |
| 155 | return key |
| 156 | } |
| 157 | |
| 158 | // buildImpersonationRequests returns a list of objectreferences that represent the different things we're requesting to impersonate. |
| 159 | // Also includes a map[string][]string representing user.Info.Extra |
| 160 | // Each request must be authorized against the current user before switching contexts. |
| 161 | func buildImpersonationRequests(headers http.Header) ([]v1.ObjectReference, error) { |
| 162 | impersonationRequests := []v1.ObjectReference{} |
| 163 | |
| 164 | requestedUser := headers.Get(authenticationv1.ImpersonateUserHeader) |
| 165 | hasUser := len(requestedUser) > 0 |
| 166 | if hasUser { |
| 167 | if namespace, name, err := serviceaccount.SplitUsername(requestedUser); err == nil { |
| 168 | impersonationRequests = append(impersonationRequests, v1.ObjectReference{Kind: "ServiceAccount", Namespace: namespace, Name: name}) |
| 169 | } else { |
| 170 | impersonationRequests = append(impersonationRequests, v1.ObjectReference{Kind: "User", Name: requestedUser}) |
| 171 | } |
| 172 | } |
| 173 | |
| 174 | hasGroups := false |
| 175 | for _, group := range headers[authenticationv1.ImpersonateGroupHeader] { |
| 176 | hasGroups = true |
| 177 | impersonationRequests = append(impersonationRequests, v1.ObjectReference{Kind: "Group", Name: group}) |
| 178 | } |
| 179 | |
| 180 | hasUserExtra := false |
| 181 | for headerName, values := range headers { |
| 182 | if !strings.HasPrefix(headerName, authenticationv1.ImpersonateUserExtraHeaderPrefix) { |
| 183 | continue |
| 184 | } |
| 185 | |
| 186 | hasUserExtra = true |
| 187 | extraKey := unescapeExtraKey(strings.ToLower(headerName[len(authenticationv1.ImpersonateUserExtraHeaderPrefix):])) |
| 188 | |
| 189 | // make a separate request for each extra value they're trying to set |
| 190 | for _, value := range values { |
| 191 | impersonationRequests = append(impersonationRequests, |
| 192 | v1.ObjectReference{ |
| 193 | Kind: "UserExtra", |
| 194 | // we only parse out a group above, but the parsing will fail if there isn't SOME version |
| 195 | // using the internal version will help us fail if anyone starts using it |
| 196 | APIVersion: authenticationv1.SchemeGroupVersion.String(), |
| 197 | Name: value, |
| 198 | // ObjectReference doesn't have a subresource field. FieldPath is close and available, so we'll use that |
| 199 | // TODO fight the good fight for ObjectReference to refer to resources and subresources |
| 200 | FieldPath: extraKey, |
| 201 | }) |
| 202 | } |
| 203 | } |
| 204 | |
| 205 | if (hasGroups || hasUserExtra) && !hasUser { |
| 206 | return nil, fmt.Errorf("requested %v without impersonating a user", impersonationRequests) |
| 207 | } |
| 208 | |
| 209 | return impersonationRequests, nil |
| 210 | } |