linux/security/apparmor/file.c
John Johansen 56974a6fcf apparmor: add base infastructure for socket mediation
version 2 - Force an abi break. Network mediation will only be
            available in v8 abi complaint policy.

Provide a basic mediation of sockets. This is not a full net mediation
but just whether a spcific family of socket can be used by an
application, along with setting up some basic infrastructure for
network mediation to follow.

the user space rule hav the basic form of
  NETWORK RULE = [ QUALIFIERS ] 'network' [ DOMAIN ]
                 [ TYPE | PROTOCOL ]

  DOMAIN = ( 'inet' | 'ax25' | 'ipx' | 'appletalk' | 'netrom' |
             'bridge' | 'atmpvc' | 'x25' | 'inet6' | 'rose' |
	     'netbeui' | 'security' | 'key' | 'packet' | 'ash' |
	     'econet' | 'atmsvc' | 'sna' | 'irda' | 'pppox' |
	     'wanpipe' | 'bluetooth' | 'netlink' | 'unix' | 'rds' |
	     'llc' | 'can' | 'tipc' | 'iucv' | 'rxrpc' | 'isdn' |
	     'phonet' | 'ieee802154' | 'caif' | 'alg' | 'nfc' |
	     'vsock' | 'mpls' | 'ib' | 'kcm' ) ','

  TYPE = ( 'stream' | 'dgram' | 'seqpacket' |  'rdm' | 'raw' |
           'packet' )

  PROTOCOL = ( 'tcp' | 'udp' | 'icmp' )

eg.
  network,
  network inet,

Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>
2018-03-13 17:25:48 -07:00

707 lines
19 KiB
C

/*
* 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/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;
}
/**
* 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)->peer) {
audit_log_format(ab, " target=");
aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
FLAG_VIEW_SUBNS, GFP_ATOMIC);
} else if (aad(sa)->fs.target) {
audit_log_format(ab, " target=");
audit_log_untrustedstring(ab, aad(sa)->fs.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)
* @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(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(sa, LSM_AUDIT_DATA_TASK, op);
sa.u.tsk = NULL;
aad(&sa)->request = request;
aad(&sa)->name = name;
aad(&sa)->fs.target = target;
aad(&sa)->peer = tlabel;
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;
AA_BUG(!aad(&sa)->request);
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 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) && d_backing_inode(dentry)->i_nlink == 0)
return 1;
return 0;
}
static int path_name(const char *op, 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(profile, &nullperms, op, request, *name,
NULL, 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;
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;
}
/**
* aa_compute_fperms - 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
*/
struct aa_perms aa_compute_fperms(struct aa_dfa *dfa, unsigned int state,
struct path_cond *cond)
{
/* 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
*/
struct aa_perms perms = { };
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 aa_perms *perms)
{
unsigned int state;
state = aa_dfa_match(dfa, start, name);
*perms = aa_compute_fperms(dfa, state, cond);
return state;
}
int __aa_path_perm(const char *op, struct aa_profile *profile, const char *name,
u32 request, struct path_cond *cond, int flags,
struct aa_perms *perms)
{
int e = 0;
if (profile_unconfined(profile))
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, NULL,
cond->uid, NULL, e);
}
static int profile_path_perm(const char *op, 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, &profile->label, path,
flags | profile->path_flags, buffer, &name, cond,
request);
if (error)
return error;
return __aa_path_perm(op, profile, name, request, cond, flags,
perms);
}
/**
* 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(const char *op, 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);
get_buffers(buffer);
error = fn_for_each_confined(label, profile,
profile_path_perm(op, profile, path, buffer, 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 struct path *link, char *buffer,
const struct path *target, char *buffer2,
struct path_cond *cond)
{
const char *lname, *tname = NULL;
struct aa_perms lperms = {}, perms;
const char *info = NULL;
u32 request = AA_MAY_LINK;
unsigned int state;
int error;
error = path_name(OP_LINK, &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, &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(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";
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(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:
error = 0;
audit:
return aa_audit_file(profile, &lperms, OP_LINK, request, lname, tname,
NULL, cond->uid, info, error);
}
/**
* 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,
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 */
get_buffers(buffer, buffer2);
error = fn_for_each_confined(label, profile,
profile_path_link(profile, &link, buffer, &target,
buffer2, &cond));
put_buffers(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,
spin_is_locked(&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, struct aa_label *label,
struct aa_label *flabel, struct file *file,
u32 request, u32 denied)
{
struct aa_profile *profile;
struct aa_perms perms = {};
struct path_cond cond = {
.uid = file_inode(file)->i_uid,
.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);
get_buffers(buffer);
/* check every profile in task label not in current cache */
error = fn_for_each_not_in_set(flabel, label, profile,
profile_path_perm(op, 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, profile, &file->f_path,
buffer, request, &cond, flags,
&perms));
else
error = fn_for_each_not_in_set(label, flabel, profile,
profile_path_perm(op, profile, &file->f_path,
buffer, request, &cond, flags,
&perms));
}
if (!error)
update_file_ctx(file_ctx(file), label, request);
put_buffers(buffer);
return error;
}
static int __file_sock_perm(const char *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_ctx(file_ctx(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(const char *op, struct aa_label *label, struct file *file,
u32 request)
{
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)))
goto done;
/* TODO: label cross check */
if (file->f_path.mnt && path_mediated_fs(file->f_path.dentry))
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);
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 int 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 int 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);
}