357 lines
9.0 KiB
C
357 lines
9.0 KiB
C
/*
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* Copyright (C) 2007 Casey Schaufler <casey@schaufler-ca.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 2.
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*
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* Author:
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* Casey Schaufler <casey@schaufler-ca.com>
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*
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*/
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#include <linux/types.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include "smack.h"
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struct smack_known smack_known_unset = {
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.smk_next = NULL,
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.smk_known = "UNSET",
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.smk_secid = 1,
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.smk_cipso = NULL,
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};
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struct smack_known smack_known_huh = {
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.smk_next = &smack_known_unset,
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.smk_known = "?",
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.smk_secid = 2,
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.smk_cipso = NULL,
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};
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struct smack_known smack_known_hat = {
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.smk_next = &smack_known_huh,
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.smk_known = "^",
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.smk_secid = 3,
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.smk_cipso = NULL,
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};
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struct smack_known smack_known_star = {
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.smk_next = &smack_known_hat,
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.smk_known = "*",
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.smk_secid = 4,
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.smk_cipso = NULL,
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};
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struct smack_known smack_known_floor = {
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.smk_next = &smack_known_star,
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.smk_known = "_",
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.smk_secid = 5,
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.smk_cipso = NULL,
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};
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struct smack_known smack_known_invalid = {
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.smk_next = &smack_known_floor,
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.smk_known = "",
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.smk_secid = 6,
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.smk_cipso = NULL,
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};
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struct smack_known *smack_known = &smack_known_invalid;
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/*
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* The initial value needs to be bigger than any of the
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* known values above.
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*/
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static u32 smack_next_secid = 10;
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/**
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* smk_access - determine if a subject has a specific access to an object
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* @subject_label: a pointer to the subject's Smack label
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* @object_label: a pointer to the object's Smack label
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* @request: the access requested, in "MAY" format
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*
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* This function looks up the subject/object pair in the
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* access rule list and returns 0 if the access is permitted,
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* non zero otherwise.
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*
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* Even though Smack labels are usually shared on smack_list
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* labels that come in off the network can't be imported
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* and added to the list for locking reasons.
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*
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* Therefore, it is necessary to check the contents of the labels,
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* not just the pointer values. Of course, in most cases the labels
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* will be on the list, so checking the pointers may be a worthwhile
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* optimization.
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*/
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int smk_access(char *subject_label, char *object_label, int request)
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{
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u32 may = MAY_NOT;
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struct smk_list_entry *sp;
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struct smack_rule *srp;
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/*
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* Hardcoded comparisons.
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*
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* A star subject can't access any object.
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*/
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if (subject_label == smack_known_star.smk_known ||
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strcmp(subject_label, smack_known_star.smk_known) == 0)
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return -EACCES;
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/*
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* A star object can be accessed by any subject.
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*/
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if (object_label == smack_known_star.smk_known ||
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strcmp(object_label, smack_known_star.smk_known) == 0)
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return 0;
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/*
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* An object can be accessed in any way by a subject
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* with the same label.
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*/
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if (subject_label == object_label ||
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strcmp(subject_label, object_label) == 0)
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return 0;
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/*
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* A hat subject can read any object.
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* A floor object can be read by any subject.
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*/
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if ((request & MAY_ANYREAD) == request) {
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if (object_label == smack_known_floor.smk_known ||
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strcmp(object_label, smack_known_floor.smk_known) == 0)
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return 0;
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if (subject_label == smack_known_hat.smk_known ||
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strcmp(subject_label, smack_known_hat.smk_known) == 0)
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return 0;
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}
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/*
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* Beyond here an explicit relationship is required.
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* If the requested access is contained in the available
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* access (e.g. read is included in readwrite) it's
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* good.
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*/
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for (sp = smack_list; sp != NULL; sp = sp->smk_next) {
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srp = &sp->smk_rule;
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if (srp->smk_subject == subject_label ||
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strcmp(srp->smk_subject, subject_label) == 0) {
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if (srp->smk_object == object_label ||
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strcmp(srp->smk_object, object_label) == 0) {
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may = srp->smk_access;
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break;
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}
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}
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}
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/*
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* This is a bit map operation.
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*/
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if ((request & may) == request)
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return 0;
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return -EACCES;
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}
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/**
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* smk_curacc - determine if current has a specific access to an object
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* @object_label: a pointer to the object's Smack label
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* @request: the access requested, in "MAY" format
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*
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* This function checks the current subject label/object label pair
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* in the access rule list and returns 0 if the access is permitted,
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* non zero otherwise. It allows that current my have the capability
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* to override the rules.
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*/
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int smk_curacc(char *obj_label, u32 mode)
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{
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int rc;
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rc = smk_access(current->security, obj_label, mode);
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if (rc == 0)
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return 0;
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if (capable(CAP_MAC_OVERRIDE))
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return 0;
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return rc;
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}
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static DEFINE_MUTEX(smack_known_lock);
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/**
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* smk_import_entry - import a label, return the list entry
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* @string: a text string that might be a Smack label
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* @len: the maximum size, or zero if it is NULL terminated.
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*
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* Returns a pointer to the entry in the label list that
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* matches the passed string, adding it if necessary.
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*/
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struct smack_known *smk_import_entry(const char *string, int len)
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{
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struct smack_known *skp;
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char smack[SMK_LABELLEN];
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int found;
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int i;
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if (len <= 0 || len > SMK_MAXLEN)
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len = SMK_MAXLEN;
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for (i = 0, found = 0; i < SMK_LABELLEN; i++) {
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if (found)
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smack[i] = '\0';
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else if (i >= len || string[i] > '~' || string[i] <= ' ' ||
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string[i] == '/') {
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smack[i] = '\0';
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found = 1;
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} else
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smack[i] = string[i];
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}
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if (smack[0] == '\0')
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return NULL;
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mutex_lock(&smack_known_lock);
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for (skp = smack_known; skp != NULL; skp = skp->smk_next)
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if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0)
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break;
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if (skp == NULL) {
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skp = kzalloc(sizeof(struct smack_known), GFP_KERNEL);
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if (skp != NULL) {
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skp->smk_next = smack_known;
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strncpy(skp->smk_known, smack, SMK_MAXLEN);
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skp->smk_secid = smack_next_secid++;
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skp->smk_cipso = NULL;
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spin_lock_init(&skp->smk_cipsolock);
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/*
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* Make sure that the entry is actually
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* filled before putting it on the list.
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*/
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smp_mb();
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smack_known = skp;
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}
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}
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mutex_unlock(&smack_known_lock);
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return skp;
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}
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/**
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* smk_import - import a smack label
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* @string: a text string that might be a Smack label
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* @len: the maximum size, or zero if it is NULL terminated.
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*
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* Returns a pointer to the label in the label list that
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* matches the passed string, adding it if necessary.
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*/
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char *smk_import(const char *string, int len)
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{
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struct smack_known *skp;
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skp = smk_import_entry(string, len);
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if (skp == NULL)
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return NULL;
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return skp->smk_known;
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}
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/**
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* smack_from_secid - find the Smack label associated with a secid
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* @secid: an integer that might be associated with a Smack label
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*
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* Returns a pointer to the appropraite Smack label if there is one,
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* otherwise a pointer to the invalid Smack label.
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*/
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char *smack_from_secid(const u32 secid)
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{
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struct smack_known *skp;
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for (skp = smack_known; skp != NULL; skp = skp->smk_next)
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if (skp->smk_secid == secid)
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return skp->smk_known;
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/*
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* If we got this far someone asked for the translation
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* of a secid that is not on the list.
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*/
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return smack_known_invalid.smk_known;
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}
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/**
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* smack_to_secid - find the secid associated with a Smack label
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* @smack: the Smack label
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*
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* Returns the appropriate secid if there is one,
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* otherwise 0
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*/
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u32 smack_to_secid(const char *smack)
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{
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struct smack_known *skp;
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for (skp = smack_known; skp != NULL; skp = skp->smk_next)
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if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0)
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return skp->smk_secid;
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return 0;
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}
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/**
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* smack_from_cipso - find the Smack label associated with a CIPSO option
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* @level: Bell & LaPadula level from the network
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* @cp: Bell & LaPadula categories from the network
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* @result: where to put the Smack value
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*
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* This is a simple lookup in the label table.
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*
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* This is an odd duck as far as smack handling goes in that
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* it sends back a copy of the smack label rather than a pointer
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* to the master list. This is done because it is possible for
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* a foreign host to send a smack label that is new to this
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* machine and hence not on the list. That would not be an
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* issue except that adding an entry to the master list can't
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* be done at that point.
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*/
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void smack_from_cipso(u32 level, char *cp, char *result)
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{
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struct smack_known *kp;
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char *final = NULL;
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for (kp = smack_known; final == NULL && kp != NULL; kp = kp->smk_next) {
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if (kp->smk_cipso == NULL)
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continue;
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spin_lock_bh(&kp->smk_cipsolock);
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if (kp->smk_cipso->smk_level == level &&
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memcmp(kp->smk_cipso->smk_catset, cp, SMK_LABELLEN) == 0)
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final = kp->smk_known;
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spin_unlock_bh(&kp->smk_cipsolock);
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}
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if (final == NULL)
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final = smack_known_huh.smk_known;
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strncpy(result, final, SMK_MAXLEN);
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return;
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}
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/**
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* smack_to_cipso - find the CIPSO option to go with a Smack label
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* @smack: a pointer to the smack label in question
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* @cp: where to put the result
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*
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* Returns zero if a value is available, non-zero otherwise.
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*/
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int smack_to_cipso(const char *smack, struct smack_cipso *cp)
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{
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struct smack_known *kp;
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for (kp = smack_known; kp != NULL; kp = kp->smk_next)
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if (kp->smk_known == smack ||
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strcmp(kp->smk_known, smack) == 0)
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break;
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if (kp == NULL || kp->smk_cipso == NULL)
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return -ENOENT;
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memcpy(cp, kp->smk_cipso, sizeof(struct smack_cipso));
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return 0;
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}
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