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// Copyright 2023 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package kernel
import (
"gvisor.dev/gvisor/pkg/errors/linuxerr"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
)
// SessionKeyring returns this Task's session keyring.
// Session keyrings are inherited from the parent when a task is started.
// If the session keyring is unset, it is implicitly initialized.
// As such, this function should never return ENOKEY.
func (t *Task) SessionKeyring() (*auth.Key, error) {
t.mu.Lock()
defer t.mu.Unlock()
if t.sessionKeyring != nil {
// Verify that we still have access to this keyring.
creds := t.Credentials()
if !creds.HasKeyPermission(t.sessionKeyring, creds.PossessedKeys(t.sessionKeyring, nil, nil), auth.KeySearch) {
return nil, linuxerr.EACCES
}
return t.sessionKeyring, nil
}
// If we don't have a session keyring, implicitly create one.
return t.joinNewSessionKeyringLocked(auth.DefaultSessionKeyringName, auth.DefaultUnnamedSessionKeyringPermissions)
}
// joinNewSessionKeyringLocked creates a new session keyring with the given
// description, and joins it immediately.
// Preconditions: t.mu is held.
//
// +checklocks:t.mu
func (t *Task) joinNewSessionKeyringLocked(newKeyDesc string, newKeyPerms auth.KeyPermissions) (*auth.Key, error) {
var sessionKeyring *auth.Key
err := t.UserNamespace().Keys.Do(func(keySet *auth.LockedKeySet) error {
creds := t.Credentials()
var err error
sessionKeyring, err = keySet.Add(newKeyDesc, creds, newKeyPerms)
return err
})
if err != nil {
return nil, err
}
t.Debugf("Joining newly-created session keyring with ID %d, permissions %v", sessionKeyring.ID, newKeyPerms)
t.sessionKeyring = sessionKeyring
return sessionKeyring, nil
}
// JoinSessionKeyring causes the task to join a keyring with the given
// key description (not ID).
// If `keyDesc` is nil, then the task joins a newly-instantiated session
// keyring instead.
func (t *Task) JoinSessionKeyring(keyDesc *string) (*auth.Key, error) {
t.mu.Lock()
defer t.mu.Unlock()
creds := t.Credentials()
possessed := creds.PossessedKeys(t.sessionKeyring, nil, nil)
var sessionKeyring *auth.Key
newKeyPerms := auth.DefaultUnnamedSessionKeyringPermissions
newKeyDesc := auth.DefaultSessionKeyringName
if keyDesc != nil {
creds.UserNamespace.Keys.ForEach(func(k *auth.Key) bool {
if k.Description == *keyDesc && creds.HasKeyPermission(k, possessed, auth.KeySearch) {
sessionKeyring = k
return true
}
return false
})
if sessionKeyring != nil {
t.Debugf("Joining existing session keyring with ID %d", sessionKeyring.ID)
t.sessionKeyring = sessionKeyring
return sessionKeyring, nil
}
newKeyDesc = *keyDesc
newKeyPerms = auth.DefaultNamedSessionKeyringPermissions
}
return t.joinNewSessionKeyringLocked(newKeyDesc, newKeyPerms)
}
// LookupKey looks up a key by ID using this task's credentials.
func (t *Task) LookupKey(keyID auth.KeySerial) (*auth.Key, error) {
t.mu.Lock()
defer t.mu.Unlock()
creds := t.Credentials()
key, err := creds.UserNamespace.Keys.Lookup(keyID)
if err != nil {
return nil, err
}
if !creds.HasKeyPermission(key, creds.PossessedKeys(t.sessionKeyring, nil, nil), auth.KeySearch) {
return nil, linuxerr.EACCES
}
return key, nil
}
// SetPermsOnKey sets the permission bits on the given key using the task's
// credentials.
func (t *Task) SetPermsOnKey(key *auth.Key, perms auth.KeyPermissions) error {
t.mu.Lock()
defer t.mu.Unlock()
creds := t.Credentials()
possessed := creds.PossessedKeys(t.sessionKeyring, nil, nil)
return creds.UserNamespace.Keys.Do(func(keySet *auth.LockedKeySet) error {
if !creds.HasKeyPermission(key, possessed, auth.KeySetAttr) {
return linuxerr.EACCES
}
keySet.SetPerms(key, perms)
return nil
})
}
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