// SPDX-License-Identifier: GPL-2.0-only
/*
* AppArmor security module
*
* This file contains AppArmor mediation of files
*
* Copyright (C) 1998-2008 Novell/SUSE
* Copyright 2009-2010 Canonical Ltd.
*/
#include <linux/tty.h>
#include <linux/fdtable.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include "include/apparmor.h"
#include "include/audit.h"
#include "include/cred.h"
#include "include/file.h"
#include "include/match.h"
#include "include/net.h"
#include "include/path.h"
#include "include/policy.h"
#include "include/label.h"
static u32 map_mask_to_chr_mask(u32 mask)
{
u32 m = mask & PERMS_CHRS_MASK;
if (mask & AA_MAY_GETATTR)
m |= MAY_READ;
if (mask & (AA_MAY_SETATTR | AA_MAY_CHMOD | AA_MAY_CHOWN))
m |= MAY_WRITE;
return m;
}
/**
* file_audit_cb - call back for file specific audit fields
* @ab: audit_buffer (NOT NULL)
* @va: audit struct to audit values of (NOT NULL)
*/
static void file_audit_cb(struct audit_buffer *ab, void *va)
{
struct common_audit_data *sa = va;
struct apparmor_audit_data *ad = aad(sa);
kuid_t fsuid = ad->subj_cred ? ad->subj_cred->fsuid : current_fsuid();
char str[10];
if (ad->request & AA_AUDIT_FILE_MASK) {
aa_perm_mask_to_str(str, sizeof(str), aa_file_perm_chrs,
map_mask_to_chr_mask(ad->request));
audit_log_format(ab, " requested_mask=\"%s\"", str);
}
if (ad->denied & AA_AUDIT_FILE_MASK) {
aa_perm_mask_to_str(str, sizeof(str), aa_file_perm_chrs,
map_mask_to_chr_mask(ad->denied));
audit_log_format(ab, " denied_mask=\"%s\"", str);
}
if (ad->request & AA_AUDIT_FILE_MASK) {
audit_log_format(ab, " fsuid=%d",
from_kuid(&init_user_ns, fsuid));
audit_log_format(ab, " ouid=%d",
from_kuid(&init_user_ns, ad->fs.ouid));
}
if (ad->peer) {
audit_log_format(ab, " target=");
aa_label_xaudit(ab, labels_ns(ad->subj_label), ad->peer,
FLAG_VIEW_SUBNS, GFP_KERNEL);
} else if (ad->fs.target) {
audit_log_format(ab, " target=");
audit_log_untrustedstring(ab, ad->fs.target);
}
}
/**
* aa_audit_file - handle the auditing of file operations
* @subj_cred: cred of the subject
* @profile: the profile being enforced (NOT NULL)
* @perms: the permissions computed for the request (NOT NULL)
* @op: operation being mediated
* @request: permissions requested
* @name: name of object being mediated (MAYBE NULL)
* @target: name of target (MAYBE NULL)
* @tlabel: target label (MAY BE NULL)
* @ouid: object uid
* @info: extra information message (MAYBE NULL)
* @error: 0 if operation allowed else failure error code
*
* Returns: %0 or error on failure
*/
int aa_audit_file(const struct cred *subj_cred,
struct aa_profile *profile, struct aa_perms *perms,
const char *op, u32 request, const char *name,
const char *target, struct aa_label *tlabel,
kuid_t ouid, const char *info, int error)
{
int type = AUDIT_APPARMOR_AUTO;
DEFINE_AUDIT_DATA(ad, LSM_AUDIT_DATA_TASK, AA_CLASS_FILE, op);
ad.subj_cred = subj_cred;
ad.request = request;
ad.name = name;
ad.fs.target = target;
ad.peer = tlabel;
ad.fs.ouid = ouid;
ad.info = info;
ad.error = error;
ad.common.u.tsk = NULL;
if (likely(!ad.error)) {
u32 mask = perms->audit;
if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
mask = 0xffff;
/* mask off perms that are not being force audited */
ad.request &= mask;
if (likely(!ad.request))
return 0;
type = AUDIT_APPARMOR_AUDIT;
} else {
/* only report permissions that were denied */
ad.request = ad.request & ~perms->allow;
AA_BUG(!ad.request);
if (ad.request & perms->kill)
type = AUDIT_APPARMOR_KILL;
/* quiet known rejects, assumes quiet and kill do not overlap */
if ((ad.request & perms->quiet) &&
AUDIT_MODE(profile) != AUDIT_NOQUIET &&
AUDIT_MODE(profile) != AUDIT_ALL)
ad.request &= ~perms->quiet;
if (!ad.request)
return ad.error;
}
ad.denied = ad.request & ~perms->allow;
return aa_audit(type, profile, &ad, file_audit_cb);
}
static int path_name(const char *op, const struct cred *subj_cred,
struct aa_label *label,
const struct path *path, int flags, char *buffer,
const char **name, struct path_cond *cond, u32 request)
{
struct aa_profile *profile;
const char *info = NULL;
int error;
error = aa_path_name(path, flags, buffer, name, &info,
labels_profile(label)->disconnected);
if (error) {
fn_for_each_confined(label, profile,
aa_audit_file(subj_cred,
profile, &nullperms, op, request, *name,
NULL, NULL, cond->uid, info, error));
return error;
}
return 0;
}
struct aa_perms default_perms = {};
/**
* aa_lookup_fperms - convert dfa compressed perms to internal perms
* @file_rules: the aa_policydb to lookup perms for (NOT NULL)
* @state: state in dfa
* @cond: conditions to consider (NOT NULL)
*
* TODO: convert from dfa + state to permission entry
*
* Returns: a pointer to a file permission set
*/
struct aa_perms *aa_lookup_fperms(struct aa_policydb *file_rules,
aa_state_t state, struct path_cond *cond)
{
unsigned int index = ACCEPT_TABLE(file_rules->dfa)[state];
if (!(file_rules->perms))
return &default_perms;
if (uid_eq(current_fsuid(), cond->uid))
return &(file_rules->perms[index]);
return &(file_rules->perms[index + 1]);
}
/**
* aa_str_perms - find permission that match @name
* @file_rules: the aa_policydb to match against (NOT NULL)
* @start: state to start matching in
* @name: string to match against dfa (NOT NULL)
* @cond: conditions to consider for permission set computation (NOT NULL)
* @perms: Returns - the permissions found when matching @name
*
* Returns: the final state in @dfa when beginning @start and walking @name
*/
aa_state_t aa_str_perms(struct aa_policydb *file_rules, aa_state_t start,
const char *name, struct path_cond *cond,
struct aa_perms *perms)
{
aa_state_t state;
state = aa_dfa_match(file_rules->dfa, start, name);
*perms = *(aa_lookup_fperms(file_rules, state, cond));
return state;
}
static int __aa_path_perm(const char *op, const struct cred *subj_cred,
struct aa_profile *profile, const char *name,
u32 request, struct path_cond *cond, int flags,
struct aa_perms *perms)
{
struct aa_ruleset *rules = list_first_entry(&profile->rules,
typeof(*rules), list);
int e = 0;
if (profile_unconfined(profile))
return 0;
aa_str_perms(rules->file, rules->file->start[AA_CLASS_FILE],
name, cond, perms);
if (request & ~perms->allow)
e = -EACCES;
return aa_audit_file(subj_cred,
profile, perms, op, request, name, NULL, NULL,
cond->uid, NULL, e);
}
static int profile_path_perm(const char *op, const struct cred *subj_cred,
struct aa_profile *profile,
const struct path *path, char *buffer, u32 request,
struct path_cond *cond, int flags,
struct aa_perms *perms)
{
const char *name;
int error;
if (profile_unconfined(profile))
return 0;
error = path_name(op, subj_cred, &profile->label, path,
flags | profile->path_flags, buffer, &name, cond,
request);
if (error)
return error;
return __aa_path_perm(op, subj_cred, profile, name, request, cond,
flags, perms);
}
/**
* aa_path_perm - do permissions check & audit for @path
* @op: operation being checked
* @subj_cred: subject cred
* @label: profile being enforced (NOT NULL)
* @path: path to check permissions of (NOT NULL)
* @flags: any additional path flags beyond what the profile specifies
* @request: requested permissions
* @cond: conditional info for this request (NOT NULL)
*
* Returns: %0 else error if access denied or other error
*/
int aa_path_perm(const char *op, const struct cred *subj_cred,
struct aa_label *label,
const struct path *path, int flags, u32 request,
struct path_cond *cond)
{
struct aa_perms perms = {};
struct aa_profile *profile;
char *buffer = NULL;
int error;
flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR :
0);
buffer = aa_get_buffer(false);
if (!buffer)
return -ENOMEM;
error = fn_for_each_confined(label, profile,
profile_path_perm(op, subj_cred, profile, path, buffer,
request, cond, flags, &perms));
aa_put_buffer(buffer);
return error;
}
/**
* xindex_is_subset - helper for aa_path_link
* @link: link permission set
* @target: target permission set
*
* test target x permissions are equal OR a subset of link x permissions
* this is done as part of the subset test, where a hardlink must have
* a subset of permissions that the target has.
*
* Returns: true if subset else false
*/
static inline bool xindex_is_subset(u32 link, u32 target)
{
if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
return false;
return true;
}
static int profile_path_link(const struct cred *subj_cred,
struct aa_profile *profile,
const struct path *link, char *buffer,
const struct path *target, char *buffer2,
struct path_cond *cond)
{
struct aa_ruleset *rules = list_first_entry(&profile->rules,
typeof(*rules), list);
const char *lname, *tname = NULL;
struct aa_perms lperms = {}, perms;
const char *info = NULL;
u32 request = AA_MAY_LINK;
aa_state_t state;
int error;
error = path_name(OP_LINK, subj_cred, &profile->label, link,
profile->path_flags,
buffer, &lname, cond, AA_MAY_LINK);
if (error)
goto audit;
/* buffer2 freed below, tname is pointer in buffer2 */
error = path_name(OP_LINK, subj_cred, &profile->label, target,
profile->path_flags,
buffer2, &tname, cond, AA_MAY_LINK);
if (error)
goto audit;
error = -EACCES;
/* aa_str_perms - handles the case of the dfa being NULL */
state = aa_str_perms(rules->file,
rules->file->start[AA_CLASS_FILE], lname,
cond, &lperms);
if (!(lperms.allow & AA_MAY_LINK))
goto audit;
/* test to see if target can be paired with link */
state = aa_dfa_null_transition(rules->file->dfa, state);
aa_str_perms(rules->file, state, tname, cond, &perms);
/* force audit/quiet masks for link are stored in the second entry
* in the link pair.
*/
lperms.audit = perms.audit;
lperms.quiet = perms.quiet;
lperms.kill = perms.kill;
if (!(perms.allow & AA_MAY_LINK)) {
info = "target restricted";
lperms = perms;
goto audit;
}
/* done if link subset test is not required */
if (!(perms.allow & AA_LINK_SUBSET))
goto done_tests;
/* Do link perm subset test requiring allowed permission on link are
* a subset of the allowed permissions on target.
*/
aa_str_perms(rules->file, rules->file->start[AA_CLASS_FILE],
tname, cond, &perms);
/* AA_MAY_LINK is not considered in the subset test */
request = lperms.allow & ~AA_MAY_LINK;
lperms.allow &= perms.allow | AA_MAY_LINK;
request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
if (request & ~lperms.allow) {
goto audit;
} else if ((lperms.allow & MAY_EXEC) &&
!xindex_is_subset(lperms.xindex, perms.xindex)) {
lperms.allow &= ~MAY_EXEC;
request |= MAY_EXEC;
info = "link not subset of target";
goto audit;
}
done_tests:
error = 0;
audit:
return aa_audit_file(subj_cred,
profile, &lperms, OP_LINK, request, lname, tname,
NULL, cond->uid, info, error);
}
/**
* aa_path_link - Handle hard link permission check
* @subj_cred: subject cred
* @label: the label being enforced (NOT NULL)
* @old_dentry: the target dentry (NOT NULL)
* @new_dir: directory the new link will be created in (NOT NULL)
* @new_dentry: the link being created (NOT NULL)
*
* Handle the permission test for a link & target pair. Permission
* is encoded as a pair where the link permission is determined
* first, and if allowed, the target is tested. The target test
* is done from the point of the link match (not start of DFA)
* making the target permission dependent on the link permission match.
*
* The subset test if required forces that permissions granted
* on link are a subset of the permission granted to target.
*
* Returns: %0 if allowed else error
*/
int aa_path_link(const struct cred *subj_cred,
struct aa_label *label, struct dentry *old_dentry,
const struct path *new_dir, struct dentry *new_dentry)
{
struct path link = { .mnt = new_dir->mnt, .dentry = new_dentry };
struct path target = { .mnt = new_dir->mnt, .dentry = old_dentry };
struct path_cond cond = {
d_backing_inode(old_dentry)->i_uid,
d_backing_inode(old_dentry)->i_mode
};
char *buffer = NULL, *buffer2 = NULL;
struct aa_profile *profile;
int error;
/* buffer freed below, lname is pointer in buffer */
buffer = aa_get_buffer(false);
buffer2 = aa_get_buffer(false);
error = -ENOMEM;
if (!buffer || !buffer2)
goto out;
error = fn_for_each_confined(label, profile,
profile_path_link(subj_cred, profile, &link, buffer,
&target, buffer2, &cond));
out:
aa_put_buffer(buffer);
aa_put_buffer(buffer2);
return error;
}
static void update_file_ctx(struct aa_file_ctx *fctx, struct aa_label *label,
u32 request)
{
struct aa_label *l, *old;
/* update caching of label on file_ctx */
spin_lock(&fctx->lock);
old = rcu_dereference_protected(fctx->label,
lockdep_is_held(&fctx->lock));
l = aa_label_merge(old, label, GFP_ATOMIC);
if (l) {
if (l != old) {
rcu_assign_pointer(fctx->label, l);
aa_put_label(old);
} else
aa_put_label(l);
fctx->allow |= request;
}
spin_unlock(&fctx->lock);
}
static int __file_path_perm(const char *op, const struct cred *subj_cred,
struct aa_label *label,
struct aa_label *flabel, struct file *file,
u32 request, u32 denied, bool in_atomic)
{
struct aa_profile *profile;
struct aa_perms perms = {};
vfsuid_t vfsuid = i_uid_into_vfsuid(file_mnt_idmap(file),
file_inode(file));
struct path_cond cond = {
.uid = vfsuid_into_kuid(vfsuid),
.mode = file_inode(file)->i_mode
};
char *buffer;
int flags, error;
/* revalidation due to label out of date. No revocation at this time */
if (!denied && aa_label_is_subset(flabel, label))
/* TODO: check for revocation on stale profiles */
return 0;
flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
buffer = aa_get_buffer(in_atomic);
if (!buffer)
return -ENOMEM;
/* check every profile in task label not in current cache */
error = fn_for_each_not_in_set(flabel, label, profile,
profile_path_perm(op, subj_cred, profile,
&file->f_path, buffer,
request, &cond, flags, &perms));
if (denied && !error) {
/*
* check every profile in file label that was not tested
* in the initial check above.
*
* TODO: cache full perms so this only happens because of
* conditionals
* TODO: don't audit here
*/
if (label == flabel)
error = fn_for_each(label, profile,
profile_path_perm(op, subj_cred,
profile, &file->f_path,
buffer, request, &cond, flags,
&perms));
else
error = fn_for_each_not_in_set(label, flabel, profile,
profile_path_perm(op, subj_cred,
profile, &file->f_path,
buffer, request, &cond, flags,
&perms));
}
if (!error)
update_file_ctx(file_ctx(file), label, request);
aa_put_buffer(buffer);
return error;
}
static int __file_sock_perm(const char *op, const struct cred *subj_cred,
struct aa_label *label,
struct aa_label *flabel, struct file *file,
u32 request, u32 denied)
{
struct socket *sock = (struct socket *) file->private_data;
int error;
AA_BUG(!sock);
/* revalidation due to label out of date. No revocation at this time */
if (!denied && aa_label_is_subset(flabel, label))
return 0;
/* TODO: improve to skip profiles cached in flabel */
error = aa_sock_file_perm(subj_cred, label, op, request, sock);
if (denied) {
/* TODO: improve to skip profiles checked above */
/* check every profile in file label to is cached */
last_error(error, aa_sock_file_perm(subj_cred, flabel, op,
request, sock));
}
if (!error)
update_file_ctx(file_ctx(file), label, request);
return error;
}
/**
* aa_file_perm - do permission revalidation check & audit for @file
* @op: operation being checked
* @subj_cred: subject cred
* @label: label being enforced (NOT NULL)
* @file: file to revalidate access permissions on (NOT NULL)
* @request: requested permissions
* @in_atomic: whether allocations need to be done in atomic context
*
* Returns: %0 if access allowed else error
*/
int aa_file_perm(const char *op, const struct cred *subj_cred,
struct aa_label *label, struct file *file,
u32 request, bool in_atomic)
{
struct aa_file_ctx *fctx;
struct aa_label *flabel;
u32 denied;
int error = 0;
AA_BUG(!label);
AA_BUG(!file);
fctx = file_ctx(file);
rcu_read_lock();
flabel = rcu_dereference(fctx->label);
AA_BUG(!flabel);
/* revalidate access, if task is unconfined, or the cached cred
* doesn't match or if the request is for more permissions than
* was granted.
*
* Note: the test for !unconfined(flabel) is to handle file
* delegation from unconfined tasks
*/
denied = request & ~fctx->allow;
if (unconfined(label) || unconfined(flabel) ||
(!denied && aa_label_is_subset(flabel, label))) {
rcu_read_unlock();
goto done;
}
flabel = aa_get_newest_label(flabel);
rcu_read_unlock();
/* TODO: label cross check */
if (file->f_path.mnt && path_mediated_fs(file->f_path.dentry))
error = __file_path_perm(op, subj_cred, label, flabel, file,
request, denied, in_atomic);
else if (S_ISSOCK(file_inode(file)->i_mode))
error = __file_sock_perm(op, subj_cred, label, flabel, file,
request, denied);
aa_put_label(flabel);
done:
return error;
}
static void revalidate_tty(const struct cred *subj_cred, struct aa_label *label)
{
struct tty_struct *tty;
int drop_tty = 0;
tty = get_current_tty();
if (!tty)
return;
spin_lock(&tty->files_lock);
if (!list_empty(&tty->tty_files)) {
struct tty_file_private *file_priv;
struct file *file;
/* TODO: Revalidate access to controlling tty. */
file_priv = list_first_entry(&tty->tty_files,
struct tty_file_private, list);
file = file_priv->file;
if (aa_file_perm(OP_INHERIT, subj_cred, label, file,
MAY_READ | MAY_WRITE, IN_ATOMIC))
drop_tty = 1;
}
spin_unlock(&tty->files_lock);
tty_kref_put(tty);
if (drop_tty)
no_tty();
}
struct cred_label {
const struct cred *cred;
struct aa_label *label;
};
static int match_file(const void *p, struct file *file, unsigned int fd)
{
struct cred_label *cl = (struct cred_label *)p;
if (aa_file_perm(OP_INHERIT, cl->cred, cl->label, file,
aa_map_file_to_perms(file), IN_ATOMIC))
return fd + 1;
return 0;
}
/* based on selinux's flush_unauthorized_files */
void aa_inherit_files(const struct cred *cred, struct files_struct *files)
{
struct aa_label *label = aa_get_newest_cred_label(cred);
struct cred_label cl = {
.cred = cred,
.label = label,
};
struct file *devnull = NULL;
unsigned int n;
revalidate_tty(cred, label);
/* Revalidate access to inherited open files. */
n = iterate_fd(files, 0, match_file, &cl);
if (!n) /* none found? */
goto out;
devnull = dentry_open(&aa_null, O_RDWR, cred);
if (IS_ERR(devnull))
devnull = NULL;
/* replace all the matching ones with this */
do {
replace_fd(n - 1, devnull, 0);
} while ((n = iterate_fd(files, n, match_file, &cl)) != 0);
if (devnull)
fput(devnull);
out:
aa_put_label(label);
}
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