// Discharge creates a macaroon that discharges the third party caveat with the
// given id that should have been created earlier using key.Public. The
// condition implicit in the id is checked for validity using checker. If
// it is valid, a new macaroon is returned which discharges the caveat
// along with any caveats returned from the checker.
func Discharge(key *KeyPair, checker ThirdPartyChecker, id string) (*macaroon.Macaroon, []checkers.Caveat, error) {
decoder := newBoxDecoder(key)
logger.Infof("server attempting to discharge %q", id)
rootKey, condition, err := decoder.decodeCaveatId(id)
if err != nil {
return nil, nil, errgo.Notef(err, "discharger cannot decode caveat id")
}
// Note that we don't check the error - we allow the
// third party checker to see even caveats that we can't
// understand.
cond, arg, _ := checkers.ParseCaveat(condition)
var caveats []checkers.Caveat
if cond == checkers.CondNeedDeclared {
caveats, err = checkNeedDeclared(id, arg, checker)
} else {
caveats, err = checker.CheckThirdPartyCaveat(id, condition)
}
if err != nil {
return nil, nil, errgo.Mask(err, errgo.Any)
}
// Note that the discharge macaroon does not need to
// be stored persistently. Indeed, it would be a problem if
// we did, because then the macaroon could potentially be used
// for normal authorization with the third party.
m, err := macaroon.New(rootKey, id, "")
if err != nil {
return nil, nil, errgo.Mask(err)
}
return m, caveats, nil
}
// NewDischarger returns a new third party caveat discharger
// which uses the given function to check caveats.
// The cond and arg arguments to the function are as returned
// by checkers.ParseCaveat.
//
// If locator is non-nil, it will be used to find public keys
// for any third party caveats returned by the checker.
//
// Calling this function has the side-effect of setting
// InsecureSkipVerify in http.DefaultTransport.TLSClientConfig
// until all the dischargers are closed.
func NewDischarger(
locator bakery.PublicKeyLocator,
checker func(req *http.Request, cond, arg string) ([]checkers.Caveat, error),
) *Discharger {
mux := http.NewServeMux()
server := httptest.NewTLSServer(mux)
svc, err := bakery.NewService(bakery.NewServiceParams{
Location: server.URL,
Locator: locator,
})
if err != nil {
panic(err)
}
checker1 := func(req *http.Request, cavId, cav string) ([]checkers.Caveat, error) {
cond, arg, err := checkers.ParseCaveat(cav)
if err != nil {
return nil, err
}
return checker(req, cond, arg)
}
httpbakery.AddDischargeHandler(mux, "/", svc, checker1)
startSkipVerify()
return &Discharger{
Service: svc,
server: server,
}
}
func (*CheckersSuite) TestOperationsChecker(c *gc.C) {
for i, test := range operationsCheckerTests {
c.Logf("%d: %s", i, test.about)
cond, arg, err := checkers.ParseCaveat(test.caveat.Condition)
c.Assert(err, gc.IsNil)
c.Assert(test.oc.Condition(), gc.Equals, "")
err = test.oc.Check(cond, arg)
if test.expectError == "" {
c.Assert(err, gc.IsNil)
continue
}
c.Assert(err, gc.ErrorMatches, test.expectError)
}
}
func checkNeedDeclared(caveatId, arg string, checker ThirdPartyChecker) ([]checkers.Caveat, error) {
i := strings.Index(arg, " ")
if i <= 0 {
return nil, errgo.Newf("need-declared caveat requires an argument, got %q", arg)
}
needDeclared := strings.Split(arg[0:i], ",")
for _, d := range needDeclared {
if d == "" {
return nil, errgo.New("need-declared caveat with empty required attribute")
}
}
if len(needDeclared) == 0 {
return nil, fmt.Errorf("need-declared caveat with no required attributes")
}
caveats, err := checker.CheckThirdPartyCaveat(caveatId, arg[i+1:])
if err != nil {
return nil, errgo.Mask(err, errgo.Any)
}
declared := make(map[string]bool)
for _, cav := range caveats {
if cav.Location != "" {
continue
}
// Note that we ignore the error. We allow the service to
// generate caveats that we don't understand here.
cond, arg, _ := checkers.ParseCaveat(cav.Condition)
if cond != checkers.CondDeclared {
continue
}
parts := strings.SplitN(arg, " ", 2)
if len(parts) != 2 {
return nil, errgo.Newf("declared caveat has no value")
}
declared[parts[0]] = true
}
// Add empty declarations for everything mentioned in need-declared
// that was not actually declared.
for _, d := range needDeclared {
if !declared[d] {
caveats = append(caveats, checkers.DeclaredCaveat(d, ""))
}
}
return caveats, nil
}
// CheckLocalLoginCaveat parses and checks that the given caveat string is
// valid for a local login request, and returns the tag of the local user
// that the caveat asserts is logged in. checkers.ErrCaveatNotRecognized will
// be returned if the caveat is not recognised.
func CheckLocalLoginCaveat(caveat string) (names.UserTag, error) {
var tag names.UserTag
op, rest, err := checkers.ParseCaveat(caveat)
if err != nil {
return tag, errors.Annotatef(err, "cannot parse caveat %q", caveat)
}
if op != "is-authenticated-user" {
return tag, checkers.ErrCaveatNotRecognized
}
if !names.IsValidUser(rest) {
return tag, errors.NotValidf("username %q", rest)
}
tag = names.NewUserTag(rest)
if !tag.IsLocal() {
tag = names.UserTag{}
return tag, errors.NotValidf("non-local username %q", rest)
}
return tag, nil
}
func (ctxt *context) CheckThirdPartyCaveat(cavId, cav string) ([]checkers.Caveat, error) {
h := ctxt.handler
log.Printf("checking third party caveat %q", cav)
op, rest, err := checkers.ParseCaveat(cav)
if err != nil {
return nil, fmt.Errorf("cannot parse caveat %q: %v", cav, err)
}
switch op {
case "can-speak-for":
// TODO(rog) We ignore the currently logged in user here,
// but perhaps it would be better to let the user be in control
// of which user they're currently "declared" as, rather than
// getting privileges of users we currently have macaroons for.
checkErr := ctxt.canSpeakFor(rest)
if checkErr == nil {
return ctxt.firstPartyCaveats(), nil
}
return nil, h.needLogin(cavId, cav, checkErr, ctxt.req)
case "member-of-group":
// The third-party caveat is asking if the currently logged in
// user is a member of a particular group.
// We can find the currently logged in user by checking
// the username cookie (which doesn't provide any power, but
// indicates which user name to check)
if ctxt.declaredUser == "" {
return nil, h.needLogin(cavId, cav, errgo.New("not logged in"), ctxt.req)
}
if err := ctxt.canSpeakFor(ctxt.declaredUser); err != nil {
return nil, errgo.Notef(err, "cannot speak for declared user %q", ctxt.declaredUser)
}
info, ok := h.users[ctxt.declaredUser]
if !ok {
return nil, errgo.Newf("user %q not found", ctxt.declaredUser)
}
group := rest
if !info.Groups[group] {
return nil, errgo.Newf("not privileged enough")
}
return ctxt.firstPartyCaveats(), nil
default:
return nil, checkers.ErrCaveatNotRecognized
}
}
func objectID(ms macaroon.Slice) (string, error) {
var fail string
var id string
for _, m := range ms {
for _, cav := range m.Caveats() {
cond, arg, err := checkers.ParseCaveat(cav.Id)
if err != nil {
// strange, but offtopic
continue
}
if cond == "object" {
if id == "" {
id = arg
} else {
return fail, fmt.Errorf("multiple conflicting caveats")
}
}
}
}
if id == "" {
return fail, errors.New("not found")
}
return id, nil
}