blob: 86235bb2ddfff31f8b8504de557a9c52e308e078 [file] [log] [blame]
/*
* AppArmor security module
*
* This file contains AppArmor mediation of files
*
* Copyright (C) 1998-2008 Novell/SUSE
* Copyright 2009-2010 Canonical Ltd.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, version 2 of the
* License.
*/
#include <linux/tty.h>
#include <linux/fdtable.h>
#include <linux/file.h>
#include "include/af_unix.h"
#include "include/apparmor.h"
#include "include/audit.h"
#include "include/context.h"
#include "include/file.h"
#include "include/match.h"
#include "include/path.h"
#include "include/policy.h"
struct file_perms nullperms;
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;
}
/**
* audit_file_mask - convert mask to permission string
* @buffer: buffer to write string to (NOT NULL)
* @mask: permission mask to convert
*/
static void audit_file_mask(struct audit_buffer *ab, u32 mask)
{
char str[10];
aa_perm_mask_to_str(str, aa_file_perm_chrs, map_mask_to_chr_mask(mask));
audit_log_string(ab, str);
}
/**
* 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;
kuid_t fsuid = current_fsuid();
if (aad(sa)->request & AA_AUDIT_FILE_MASK) {
audit_log_format(ab, " requested_mask=");
audit_file_mask(ab, aad(sa)->request);
}
if (aad(sa)->denied & AA_AUDIT_FILE_MASK) {
audit_log_format(ab, " denied_mask=");
audit_file_mask(ab, aad(sa)->denied);
}
if (aad(sa)->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, aad(sa)->fs.ouid));
}
if (aad(sa)->target) {
audit_log_format(ab, " target=");
audit_log_untrustedstring(ab, aad(sa)->target);
}
}
/**
* aa_audit_file - handle the auditing of file operations
* @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)
* @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(struct aa_profile *profile, struct file_perms *perms,
int op, u32 request, const char *name, const char *target,
kuid_t ouid, const char *info, int error)
{
int type = AUDIT_APPARMOR_AUTO;
DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_NONE, op);
aad(&sa)->request = request;
aad(&sa)->name = name;
aad(&sa)->target = target;
aad(&sa)->fs.ouid = ouid;
aad(&sa)->info = info;
aad(&sa)->error = error;
sa.u.tsk = NULL;
if (likely(!aad(&sa)->error)) {
u32 mask = perms->audit;
if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
mask = 0xffff;
/* mask off perms that are not being force audited */
aad(&sa)->request &= mask;
if (likely(!aad(&sa)->request))
return 0;
type = AUDIT_APPARMOR_AUDIT;
} else {
/* only report permissions that were denied */
aad(&sa)->request = aad(&sa)->request & ~perms->allow;
if (aad(&sa)->request & perms->kill)
type = AUDIT_APPARMOR_KILL;
/* quiet known rejects, assumes quiet and kill do not overlap */
if ((aad(&sa)->request & perms->quiet) &&
AUDIT_MODE(profile) != AUDIT_NOQUIET &&
AUDIT_MODE(profile) != AUDIT_ALL)
aad(&sa)->request &= ~perms->quiet;
if (!aad(&sa)->request)
return COMPLAIN_MODE(profile) ? 0 : aad(&sa)->error;
}
aad(&sa)->denied = aad(&sa)->request & ~perms->allow;
return aa_audit(type, profile, &sa, file_audit_cb);
}
/**
* is_deleted - test if a file has been completely unlinked
* @dentry: dentry of file to test for deletion (NOT NULL)
*
* Returns: %1 if deleted else %0
*/
static inline bool is_deleted(struct dentry *dentry)
{
if (d_unlinked(dentry) && dentry->d_inode->i_nlink == 0)
return 1;
return 0;
}
static int path_name(int op, struct aa_label *label, struct path *path,
int flags, char *buffer, const char**name,
struct path_cond *cond, u32 request, bool delegate_deleted)
{
struct aa_profile *profile;
const char *info = NULL;
int error = aa_path_name(path, flags, buffer, name, &info,
labels_profile(label)->disconnected);
if (error) {
if (error == -ENOENT && is_deleted(path->dentry) &&
delegate_deleted)
return 0;
fn_for_each_confined(label, profile,
aa_audit_file(profile, &nullperms, op, request, *name,
NULL, cond->uid, info, error));
return error;
}
return 0;
}
/**
* map_old_perms - map old file perms layout to the new layout
* @old: permission set in old mapping
*
* Returns: new permission mapping
*/
static u32 map_old_perms(u32 old)
{
u32 new = old & 0xf;
if (old & MAY_READ)
new |= AA_MAY_GETATTR | AA_MAY_OPEN;
if (old & MAY_WRITE)
new |= AA_MAY_SETATTR | AA_MAY_CREATE | AA_MAY_DELETE |
AA_MAY_CHMOD | AA_MAY_CHOWN | AA_MAY_OPEN |
AA_MAY_DELETE;
if (old & 0x10)
new |= AA_MAY_LINK;
/* the old mapping lock and link_subset flags where overlaid
* and use was determined by part of a pair that they were in
*/
if (old & 0x20)
new |= AA_MAY_LOCK | AA_LINK_SUBSET;
if (old & 0x40) /* AA_EXEC_MMAP */
new |= AA_EXEC_MMAP;
return new;
}
/**
* compute_perms - convert dfa compressed perms to internal perms
* @dfa: dfa to compute perms for (NOT NULL)
* @state: state in dfa
* @cond: conditions to consider (NOT NULL)
*
* TODO: convert from dfa + state to permission entry, do computation conversion
* at load time.
*
* Returns: computed permission set
*/
static struct file_perms compute_perms(struct aa_dfa *dfa, unsigned int state,
struct path_cond *cond)
{
struct file_perms perms;
/* FIXME: change over to new dfa format
* currently file perms are encoded in the dfa, new format
* splits the permissions from the dfa. This mapping can be
* done at profile load
*/
perms.kill = 0;
if (uid_eq(current_fsuid(), cond->uid)) {
perms.allow = map_old_perms(dfa_user_allow(dfa, state));
perms.audit = map_old_perms(dfa_user_audit(dfa, state));
perms.quiet = map_old_perms(dfa_user_quiet(dfa, state));
perms.xindex = dfa_user_xindex(dfa, state);
} else {
perms.allow = map_old_perms(dfa_other_allow(dfa, state));
perms.audit = map_old_perms(dfa_other_audit(dfa, state));
perms.quiet = map_old_perms(dfa_other_quiet(dfa, state));
perms.xindex = dfa_other_xindex(dfa, state);
}
perms.allow |= AA_MAY_GETATTR;
/* change_profile wasn't determined by ownership in old mapping */
if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
perms.allow |= AA_MAY_CHANGE_PROFILE;
if (ACCEPT_TABLE(dfa)[state] & 0x40000000)
perms.allow |= AA_MAY_ONEXEC;
return perms;
}
/**
* aa_str_perms - find permission that match @name
* @dfa: to match against (MAYBE NULL)
* @state: 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
*/
unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,
const char *name, struct path_cond *cond,
struct file_perms *perms)
{
unsigned int state;
if (!dfa) {
*perms = nullperms;
return DFA_NOMATCH;
}
state = aa_dfa_match(dfa, start, name);
*perms = compute_perms(dfa, state, cond);
return state;
}
int __aa_path_perm(int op, struct aa_profile *profile, const char *name,
u32 request, struct path_cond *cond, int flags,
struct file_perms *perms)
{
int e = 0;
if (profile_unconfined(profile) ||
((flags & PATH_SOCK_COND) && !PROFILE_MEDIATES_AF(profile, AF_UNIX)))
return 0;
aa_str_perms(profile->file.dfa, profile->file.start, name, cond, perms);
if (request & ~perms->allow)
e = -EACCES;
return aa_audit_file(profile, perms, op, request, name, NULL,
cond->uid, NULL, e);
}
/**
* aa_path_perm - do permissions check & audit for @path
* @op: operation being checked
* @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(int op, struct aa_label *label, struct path *path,
int flags, u32 request, struct path_cond *cond)
{
struct file_perms perms = {};
char *buffer = NULL;
const char *name;
struct aa_profile *profile;
int error;
/* TODO: fix path lookup flags */
flags |= labels_profile(label)->path_flags |
(S_ISDIR(cond->mode) ? PATH_IS_DIR : 0);
get_buffers(buffer);
error = path_name(op, label, path, flags, buffer, &name, cond,
request, true);
if (!error)
error = fn_for_each_confined(label, profile,
__aa_path_perm(op, profile, name, request, cond,
flags, &perms));
put_buffers(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: %1 if subset else %0
*/
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 0;
return 1;
}
static int profile_path_link(struct aa_profile *profile, const char *lname,
const char *tname, struct path_cond *cond)
{
struct file_perms lperms, perms;
const char *info = NULL;
u32 request = AA_MAY_LINK;
unsigned int state;
int e = -EACCES;
/* aa_str_perms - handles the case of the dfa being NULL */
state = aa_str_perms(profile->file.dfa, profile->file.start, 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(profile->file.dfa, state);
aa_str_perms(profile->file.dfa, 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";
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(profile->file.dfa, profile->file.start, 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:
e = 0;
audit:
return aa_audit_file(profile, &lperms, OP_LINK, request, lname, tname,
cond->uid, info, e);
}
/**
* aa_path_link - Handle hard link permission check
* @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(struct aa_label *label, struct dentry *old_dentry,
struct path *new_dir, struct dentry *new_dentry)
{
struct path link = { new_dir->mnt, new_dentry };
struct path target = { new_dir->mnt, old_dentry };
struct path_cond cond = {
old_dentry->d_inode->i_uid,
old_dentry->d_inode->i_mode
};
char *buffer = NULL, *buffer2 = NULL;
const char *lname, *tname = NULL;
struct aa_profile *profile;
int error;
/* TODO: fix path lookup flags, auditing of failed path for profile */
profile = labels_profile(label);
/* buffer freed below, lname is pointer in buffer */
get_buffers(buffer, buffer2);
error = path_name(OP_LINK, label, &link,
labels_profile(label)->path_flags, buffer,
&lname, &cond, AA_MAY_LINK, false);
if (error)
goto out;
/* buffer2 freed below, tname is pointer in buffer2 */
error = path_name(OP_LINK, label, &target,
labels_profile(label)->path_flags, buffer2, &tname,
&cond, AA_MAY_LINK, false);
if (error)
goto out;
error = fn_for_each_confined(label, profile,
profile_path_link(profile, lname, tname, &cond));
out:
put_buffers(buffer, buffer2);
return error;
}
static void update_file_cxt(struct aa_file_cxt *fcxt, struct aa_label *label,
u32 request)
{
struct aa_label *l, *old;
/* update caching of label on file_cxt */
spin_lock(&fcxt->lock);
old = rcu_dereference_protected(fcxt->label,
spin_is_locked(&fcxt->lock));
l = aa_label_merge(old, label, GFP_ATOMIC);
if (l) {
if (l != old) {
rcu_assign_pointer(fcxt->label, l);
aa_put_label(old);
} else
aa_put_label(l);
fcxt->allow |= request;
}
spin_unlock(&fcxt->lock);
}
static int __file_path_perm(int op, struct aa_label *label,
struct aa_label *flabel, struct file *file,
u32 request, u32 denied)
{
struct aa_profile *profile;
struct file_perms perms = {};
struct path_cond cond = {
.uid = file_inode(file)->i_uid,
.mode = file_inode(file)->i_mode
};
const char *name;
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;
/* TODO: fix path lookup flags */
flags = PATH_DELEGATE_DELETED | labels_profile(label)->path_flags |
(S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
get_buffers(buffer);
error = path_name(op, label, &file->f_path, flags, buffer, &name, &cond,
request, true);
if (error) {
if (error == 1)
/* Access to open files that are deleted are
* given a pass (implicit delegation)
*/
/* TODO not needed when full perms cached */
error = 0;
goto out;
}
/* check every profile in task label not in current cache */
error = fn_for_each_not_in_set(flabel, label, profile,
__aa_path_perm(op, profile, name, request, &cond, 0,
&perms));
if (denied) {
/* 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 */
last_error(error,
fn_for_each_not_in_set(label, flabel, profile,
__aa_path_perm(op, profile, name, request,
&cond, 0, &perms)));
}
if (!error)
update_file_cxt(file_cxt(file), label, request);
out:
put_buffers(buffer);
return error;
}
#include <uapi/linux/magic.h>
static int __file_sock_perm(int op, 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(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(flabel, op, request, sock));
}
if (!error)
update_file_cxt(file_cxt(file), label, request);
return error;
}
/**
* aa_file_perm - do permission revalidation check & audit for @file
* @op: operation being checked
* @label: label being enforced (NOT NULL)
* @file: file to revalidate access permissions on (NOT NULL)
* @request: requested permissions
*
* Returns: %0 if access allowed else error
*/
int aa_file_perm(int op, struct aa_label *label, struct file *file,
u32 request)
{
struct aa_file_cxt *fcxt;
struct aa_label *flabel;
u32 denied;
int error = 0;
AA_BUG(!label);
AA_BUG(!file);
fcxt = file_cxt(file);
rcu_read_lock();
flabel = rcu_dereference(fcxt->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 & ~fcxt->allow;
if (unconfined(label) || unconfined(flabel) ||
(!denied && aa_label_is_subset(flabel, label)))
goto done;
/* TODO: label cross check */
if (file->f_path.mnt && path_mediated_fs(file_inode(file))) {
error = __file_path_perm(op, label, flabel, file, request,
denied);
} else if (S_ISSOCK(file_inode(file)->i_mode)) {
error = __file_sock_perm(op, label, flabel, file, request,
denied);
} else {
char *s = aa_imode_name(file_inode(file)->i_mode);
if (file_inode(file)->i_sb->s_magic != PIPEFS_MAGIC && file_inode(file)->i_sb->s_magic != ANON_INODE_FS_MAGIC)
;
/*
printk("apparmor: revalidation of non-mediated file. denied 0x%x mnt? %p (%s) label: (%p) magic 0x%x\n", denied, file->f_path.mnt, s, label, file_inode(file)->i_sb->s_magic);
*/
}
done:
rcu_read_unlock();
return error;
}
static void revalidate_tty(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, label, file, MAY_READ | MAY_WRITE))
drop_tty = 1;
}
spin_unlock(&tty_files_lock);
tty_kref_put(tty);
if (drop_tty)
no_tty();
}
static int match_file(const void *p, struct file *file, unsigned fd)
{
struct aa_label *label = (struct aa_label *)p;
if (aa_file_perm(OP_INHERIT, label, file, aa_map_file_to_perms(file)))
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 file *devnull = NULL;
unsigned n;
revalidate_tty(label);
/* Revalidate access to inherited open files. */
n = iterate_fd(files, 0, match_file, label);
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, label)) != 0);
if (devnull)
fput(devnull);
out:
aa_put_label(label);
}