/*
* Check a credential for privilege.
*
* A non-null credential is expected unless NULL_CRED_OKAY is set.
*
* MPSAFE
*/
int
priv_check_cred(struct ucred *cred, int priv, int flags)
{
int error;
KASSERT(PRIV_VALID(priv), ("priv_check_cred: invalid privilege"));
KASSERT(cred != NULL || flags & NULL_CRED_OKAY,
("priv_check_cred: NULL cred!"));
if (cred == NULL) {
if (flags & NULL_CRED_OKAY)
return (0);
else
return (EPERM);
}
if (cred->cr_uid != 0)
return (EPERM);
error = prison_priv_check(cred, priv);
if (error)
return (error);
/* NOTE: accounting for suser access (p_acflag/ASU) removed */
return (0);
}
/*
* Check a credential for privilege. Lots of good reasons to deny privilege;
* only a few to grant it.
*/
int
priv_check_cred(struct ucred *cred, int priv, int flags)
{
int error;
KASSERT(PRIV_VALID(priv), ("priv_check_cred: invalid privilege %d",
priv));
/*
* We first evaluate policies that may deny the granting of
* privilege unilaterally.
*/
#ifdef MAC
error = mac_priv_check(cred, priv);
if (error)
goto out;
#endif
/*
* Jail policy will restrict certain privileges that may otherwise be
* be granted.
*/
error = prison_priv_check(cred, priv);
if (error)
goto out;
if (unprivileged_mlock) {
/*
* Allow unprivileged users to call mlock(2)/munlock(2) and
* mlockall(2)/munlockall(2).
*/
switch (priv) {
case PRIV_VM_MLOCK:
case PRIV_VM_MUNLOCK:
error = 0;
goto out;
}
}
/*
* Having determined if privilege is restricted by various policies,
* now determine if privilege is granted. At this point, any policy
* may grant privilege. For now, we allow short-circuit boolean
* evaluation, so may not call all policies. Perhaps we should.
*
* Superuser policy grants privilege based on the effective (or in
* the case of specific privileges, real) uid being 0. We allow the
* superuser policy to be globally disabled, although this is
* currenty of limited utility.
*/
if (suser_enabled) {
switch (priv) {
case PRIV_MAXFILES:
case PRIV_MAXPROC:
case PRIV_PROC_LIMIT:
if (cred->cr_ruid == 0) {
error = 0;
goto out;
}
break;
default:
if (cred->cr_uid == 0) {
error = 0;
goto out;
}
break;
}
}
/*
* Writes to kernel/physical memory are a typical root-only operation,
* but non-root users are expected to be able to read it (provided they
* have permission to access /dev/[k]mem).
*/
if (priv == PRIV_KMEM_READ) {
error = 0;
goto out;
}
/*
* Now check with MAC, if enabled, to see if a policy module grants
* privilege.
*/
#ifdef MAC
if (mac_priv_grant(cred, priv) == 0) {
error = 0;
goto out;
}
#endif
/*
* The default is deny, so if no policies have granted it, reject
* with a privilege error here.
*/
error = EPERM;
out:
if (error)
SDT_PROBE1(priv, kernel, priv_check, priv__err, priv);
else
SDT_PROBE1(priv, kernel, priv_check, priv__ok, priv);
return (error);
}
