diff options
| -rw-r--r-- | security/safesetid/lsm.c | 125 |
1 files changed, 35 insertions, 90 deletions
diff --git a/security/safesetid/lsm.c b/security/safesetid/lsm.c index ac55bf193213..0770447d51f0 100644 --- a/security/safesetid/lsm.c +++ b/security/safesetid/lsm.c @@ -99,20 +99,30 @@ static int safesetid_security_capable(const struct cred *cred, return 0; } -static int check_uid_transition(kuid_t parent, kuid_t child) +/* + * Check whether a caller with old credentials @old is allowed to switch to + * credentials that contain @new_uid. + */ +static bool uid_permitted_for_cred(const struct cred *old, kuid_t new_uid) { - if (check_setuid_policy_hashtable_key_value(parent, child)) - return 0; - pr_warn("UID transition (%d -> %d) blocked\n", - __kuid_val(parent), - __kuid_val(child)); + bool permitted; + + /* If our old creds already had this UID in it, it's fine. */ + if (uid_eq(new_uid, old->uid) || uid_eq(new_uid, old->euid) || + uid_eq(new_uid, old->suid)) + return true; + /* - * Kill this process to avoid potential security vulnerabilities - * that could arise from a missing whitelist entry preventing a - * privileged process from dropping to a lesser-privileged one. + * Transitions to new UIDs require a check against the policy of the old + * RUID. */ - force_sig(SIGKILL); - return -EACCES; + permitted = check_setuid_policy_hashtable_key_value(old->uid, new_uid); + if (!permitted) { + pr_warn("UID transition ((%d,%d,%d) -> %d) blocked\n", + __kuid_val(old->uid), __kuid_val(old->euid), + __kuid_val(old->suid), __kuid_val(new_uid)); + } + return permitted; } /* @@ -125,88 +135,23 @@ static int safesetid_task_fix_setuid(struct cred *new, int flags) { - /* Do nothing if there are no setuid restrictions for this UID. */ + /* Do nothing if there are no setuid restrictions for our old RUID. */ if (!check_setuid_policy_hashtable_key(old->uid)) return 0; - switch (flags) { - case LSM_SETID_RE: - /* - * Users for which setuid restrictions exist can only set the - * real UID to the real UID or the effective UID, unless an - * explicit whitelist policy allows the transition. - */ - if (!uid_eq(old->uid, new->uid) && - !uid_eq(old->euid, new->uid)) { - return check_uid_transition(old->uid, new->uid); - } - /* - * Users for which setuid restrictions exist can only set the - * effective UID to the real UID, the effective UID, or the - * saved set-UID, unless an explicit whitelist policy allows - * the transition. - */ - if (!uid_eq(old->uid, new->euid) && - !uid_eq(old->euid, new->euid) && - !uid_eq(old->suid, new->euid)) { - return check_uid_transition(old->euid, new->euid); - } - break; - case LSM_SETID_ID: - /* - * Users for which setuid restrictions exist cannot change the - * real UID or saved set-UID unless an explicit whitelist - * policy allows the transition. - */ - if (!uid_eq(old->uid, new->uid)) - return check_uid_transition(old->uid, new->uid); - if (!uid_eq(old->suid, new->suid)) - return check_uid_transition(old->suid, new->suid); - break; - case LSM_SETID_RES: - /* - * Users for which setuid restrictions exist cannot change the - * real UID, effective UID, or saved set-UID to anything but - * one of: the current real UID, the current effective UID or - * the current saved set-user-ID unless an explicit whitelist - * policy allows the transition. - */ - if (!uid_eq(new->uid, old->uid) && - !uid_eq(new->uid, old->euid) && - !uid_eq(new->uid, old->suid)) { - return check_uid_transition(old->uid, new->uid); - } - if (!uid_eq(new->euid, old->uid) && - !uid_eq(new->euid, old->euid) && - !uid_eq(new->euid, old->suid)) { - return check_uid_transition(old->euid, new->euid); - } - if (!uid_eq(new->suid, old->uid) && - !uid_eq(new->suid, old->euid) && - !uid_eq(new->suid, old->suid)) { - return check_uid_transition(old->suid, new->suid); - } - break; - case LSM_SETID_FS: - /* - * Users for which setuid restrictions exist cannot change the - * filesystem UID to anything but one of: the current real UID, - * the current effective UID or the current saved set-UID - * unless an explicit whitelist policy allows the transition. - */ - if (!uid_eq(new->fsuid, old->uid) && - !uid_eq(new->fsuid, old->euid) && - !uid_eq(new->fsuid, old->suid) && - !uid_eq(new->fsuid, old->fsuid)) { - return check_uid_transition(old->fsuid, new->fsuid); - } - break; - default: - pr_warn("Unknown setid state %d\n", flags); - force_sig(SIGKILL); - return -EINVAL; - } - return 0; + if (uid_permitted_for_cred(old, new->uid) && + uid_permitted_for_cred(old, new->euid) && + uid_permitted_for_cred(old, new->suid) && + uid_permitted_for_cred(old, new->fsuid)) + return 0; + + /* + * Kill this process to avoid potential security vulnerabilities + * that could arise from a missing whitelist entry preventing a + * privileged process from dropping to a lesser-privileged one. + */ + force_sig(SIGKILL); + return -EACCES; } int add_safesetid_whitelist_entry(kuid_t parent, kuid_t child) |