KEYS: Add a keyctl to install a process's session keyring on its parent [try #6]

[mv-sheeva.git] / security / keys / keyctl.c

diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 736d7800f97f9bd2c0f20c8599432971b0dd57d0..74c96852459281cab2b959a0b2db55666c7c9a7b 100644 (file)
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1228,6 +1228,105 @@ long keyctl_get_security(key_serial_t keyid,
        return ret;
 }
 
+/*
+ * attempt to install the calling process's session keyring on the process's
+ * parent process
+ * - the keyring must exist and must grant us LINK permission
+ * - implements keyctl(KEYCTL_SESSION_TO_PARENT)
+ */
+long keyctl_session_to_parent(void)
+{
+       struct task_struct *me, *parent;
+       const struct cred *mycred, *pcred;
+       struct cred *cred, *oldcred;
+       key_ref_t keyring_r;
+       int ret;
+
+       keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_LINK);
+       if (IS_ERR(keyring_r))
+               return PTR_ERR(keyring_r);
+
+       /* our parent is going to need a new cred struct, a new tgcred struct
+        * and new security data, so we allocate them here to prevent ENOMEM in
+        * our parent */
+       ret = -ENOMEM;
+       cred = cred_alloc_blank();
+       if (!cred)
+               goto error_keyring;
+
+       cred->tgcred->session_keyring = key_ref_to_ptr(keyring_r);
+       keyring_r = NULL;
+
+       me = current;
+       write_lock_irq(&tasklist_lock);
+
+       parent = me->real_parent;
+       ret = -EPERM;
+
+       /* the parent mustn't be init and mustn't be a kernel thread */
+       if (parent->pid <= 1 || !parent->mm)
+               goto not_permitted;
+
+       /* the parent must be single threaded */
+       if (atomic_read(&parent->signal->count) != 1)
+               goto not_permitted;
+
+       /* the parent and the child must have different session keyrings or
+        * there's no point */
+       mycred = current_cred();
+       pcred = __task_cred(parent);
+       if (mycred == pcred ||
+           mycred->tgcred->session_keyring == pcred->tgcred->session_keyring)
+               goto already_same;
+
+       /* the parent must have the same effective ownership and mustn't be
+        * SUID/SGID */
+       if (pcred-> uid != mycred->euid ||
+           pcred->euid != mycred->euid ||
+           pcred->suid != mycred->euid ||
+           pcred-> gid != mycred->egid ||
+           pcred->egid != mycred->egid ||
+           pcred->sgid != mycred->egid)
+               goto not_permitted;
+
+       /* the keyrings must have the same UID */
+       if (pcred ->tgcred->session_keyring->uid != mycred->euid ||
+           mycred->tgcred->session_keyring->uid != mycred->euid)
+               goto not_permitted;
+
+       /* the LSM must permit the replacement of the parent's keyring with the
+        * keyring from this process */
+       ret = security_key_session_to_parent(mycred, pcred,
+                                            key_ref_to_ptr(keyring_r));
+       if (ret < 0)
+               goto not_permitted;
+
+       /* if there's an already pending keyring replacement, then we replace
+        * that */
+       oldcred = parent->replacement_session_keyring;
+
+       /* the replacement session keyring is applied just prior to userspace
+        * restarting */
+       parent->replacement_session_keyring = cred;
+       cred = NULL;
+       set_ti_thread_flag(task_thread_info(parent), TIF_NOTIFY_RESUME);
+
+       write_unlock_irq(&tasklist_lock);
+       if (oldcred)
+               put_cred(oldcred);
+       return 0;
+
+already_same:
+       ret = 0;
+not_permitted:
+       put_cred(cred);
+       return ret;
+
+error_keyring:
+       key_ref_put(keyring_r);
+       return ret;
+}
+
 /*****************************************************************************/
 /*
  * the key control system call
@@ -1313,6 +1412,9 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
                                           (char __user *) arg3,
                                           (size_t) arg4);
 
+       case KEYCTL_SESSION_TO_PARENT:
+               return keyctl_session_to_parent();
+
        default:
                return -EOPNOTSUPP;
        }