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zot/pkg/api/authz.go

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package api
import (
"context"
"encoding/base64"
"net/http"
"strings"
"time"
"github.com/gorilla/mux"
"zotregistry.io/zot/pkg/api/config"
"zotregistry.io/zot/pkg/log"
)
type contextKey int
const (
// actions.
CREATE = "create"
READ = "read"
UPDATE = "update"
DELETE = "delete"
// request-local context key.
authzCtxKey contextKey = 0
)
// AccessController authorizes users to act on resources.
type AccessController struct {
Config *config.AccessControlConfig
Log log.Logger
}
// AccessControlContext context passed down to http.Handlers.
type AccessControlContext struct {
userAllowedRepos []string
isAdmin bool
}
func NewAccessController(config *config.Config) *AccessController {
return &AccessController{
Config: config.AccessControl,
Log: log.NewLogger(config.Log.Level, config.Log.Output),
}
}
// getReadRepos get repositories from config file that the user has READ perms.
func (ac *AccessController) getReadRepos(username string) []string {
var repos []string
for r, pg := range ac.Config.Repositories {
for _, p := range pg.Policies {
if (contains(p.Users, username) && contains(p.Actions, READ)) ||
contains(pg.DefaultPolicy, READ) {
repos = append(repos, r)
}
}
}
return repos
}
// can verifies if a user can do action on repository.
func (ac *AccessController) can(username, action, repository string) bool {
can := false
// check repo based policy
pg, ok := ac.Config.Repositories[repository]
if ok {
can = isPermitted(username, action, pg)
}
//check admins based policy
if !can {
if ac.isAdmin(username) && contains(ac.Config.AdminPolicy.Actions, action) {
can = true
}
}
return can
}
// isAdmin .
func (ac *AccessController) isAdmin(username string) bool {
return contains(ac.Config.AdminPolicy.Users, username)
}
// getContext builds ac context(allowed to read repos and if user is admin) and returns it.
func (ac *AccessController) getContext(username string, r *http.Request) context.Context {
userAllowedRepos := ac.getReadRepos(username)
acCtx := AccessControlContext{userAllowedRepos: userAllowedRepos}
if ac.isAdmin(username) {
acCtx.isAdmin = true
} else {
acCtx.isAdmin = false
}
ctx := context.WithValue(r.Context(), authzCtxKey, acCtx)
return ctx
}
// isPermitted returns true if username can do action on a repository policy.
func isPermitted(username, action string, pg config.PolicyGroup) bool {
var result bool
// check repo/system based policies
for _, p := range pg.Policies {
if contains(p.Users, username) && contains(p.Actions, action) {
result = true
break
}
}
// check defaultPolicy
if !result {
if contains(pg.DefaultPolicy, action) {
result = true
}
}
return result
}
func contains(slice []string, item string) bool {
for _, v := range slice {
if item == v {
return true
}
}
return false
}
func containsRepo(slice []string, item string) bool {
for _, v := range slice {
if strings.HasPrefix(item, v) {
return true
}
}
return false
}
func AuthzHandler(c *Controller) mux.MiddlewareFunc {
return func(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
vars := mux.Vars(r)
resource := vars["name"]
reference, ok := vars["reference"]
ac := NewAccessController(c.Config)
username := getUsername(r)
ctx := ac.getContext(username, r)
if r.RequestURI == "/v2/_catalog" || r.RequestURI == "/v2/" {
next.ServeHTTP(w, r.WithContext(ctx))
return
}
var action string
if r.Method == http.MethodGet || r.Method == http.MethodHead {
action = READ
}
if r.Method == http.MethodPut || r.Method == http.MethodPatch || r.Method == http.MethodPost {
// assume user wants to create
action = CREATE
// if we get a reference (tag)
if ok {
is := c.StoreController.GetImageStore(resource)
tags, err := is.GetImageTags(resource)
// if repo exists and request's tag doesn't exist yet then action is UPDATE
if err == nil && contains(tags, reference) && reference != "latest" {
action = UPDATE
}
}
}
if r.Method == http.MethodDelete {
action = DELETE
}
can := ac.can(username, action, resource)
if !can {
authzFail(w, c.Config.HTTP.Realm, c.Config.HTTP.Auth.FailDelay)
} else {
next.ServeHTTP(w, r.WithContext(ctx))
}
})
}
}
func getUsername(r *http.Request) string {
// this should work because it worked in auth middleware
basicAuth := r.Header.Get("Authorization")
s := strings.SplitN(basicAuth, " ", 2)
b, _ := base64.StdEncoding.DecodeString(s[1])
pair := strings.SplitN(string(b), ":", 2)
return pair[0]
}
func authzFail(w http.ResponseWriter, realm string, delay int) {
time.Sleep(time.Duration(delay) * time.Second)
w.Header().Set("WWW-Authenticate", realm)
w.Header().Set("Content-Type", "application/json")
WriteJSON(w, http.StatusForbidden, NewErrorList(NewError(DENIED)))
}