/*
* 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 "include/apparmor.h"
#include "include/audit.h"
#include "include/file.h"
#include "include/match.h"
#include "include/path.h"
#include "include/policy.h"
struct file_perms nullperms;
/**
* 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];
char *m = str;
if (mask & AA_EXEC_MMAP)
*m++ = 'm';
if (mask & (MAY_READ | AA_MAY_META_READ))
*m++ = 'r';
if (mask & (MAY_WRITE | AA_MAY_META_WRITE | AA_MAY_CHMOD |
AA_MAY_CHOWN))
*m++ = 'w';
else if (mask & MAY_APPEND)
*m++ = 'a';
if (mask & AA_MAY_CREATE)
*m++ = 'c';
if (mask & AA_MAY_DELETE)
*m++ = 'd';
if (mask & AA_MAY_LINK)
*m++ = 'l';
if (mask & AA_MAY_LOCK)
*m++ = 'k';
if (mask & MAY_EXEC)
*m++ = 'x';
*m = '\0';
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;
uid_t fsuid = current_fsuid();
if (sa->aad->fs.request & AA_AUDIT_FILE_MASK) {
audit_log_format(ab, " requested_mask=");
audit_file_mask(ab, sa->aad->fs.request);
}
if (sa->aad->fs.denied & AA_AUDIT_FILE_MASK) {
audit_log_format(ab, " denied_mask=");
audit_file_mask(ab, sa->aad->fs.denied);
}
if (sa->aad->fs.request & AA_AUDIT_FILE_MASK) {
audit_log_format(ab, " fsuid=%d", fsuid);
audit_log_format(ab, " ouid=%d", sa->aad->fs.ouid);
}
if (sa->aad->fs.target) {
audit_log_format(ab, " target=");
audit_log_untrustedstring(ab, sa->aad->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)
* @gfp: allocation flags
* @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,
gfp_t gfp, int op, u32 request, const char *name,
const char *target, uid_t ouid, const char *info, int error)
{
int type = AUDIT_APPARMOR_AUTO;
struct common_audit_data sa;
struct apparmor_audit_data aad = {0,};
sa.type = LSM_AUDIT_DATA_NONE;
sa.aad = &aad;
aad.op = op,
aad.fs.request = request;
aad.name = name;
aad.fs.target = target;
aad.fs.ouid = ouid;
aad.info = info;
aad.error = error;
if (likely(!sa.aad->error)) {
u32 mask = perms->audit;
if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
mask = 0xffff;
/* mask off perms that are not being force audited */
sa.aad->fs.request &= mask;
if (likely(!sa.aad->fs.request))
return 0;
type = AUDIT_APPARMOR_AUDIT;
} else {
/* only report permissions that were denied */
sa.aad->fs.request = sa.aad->fs.request & ~perms->allow;
if (sa.aad->fs.request & perms->kill)
type = AUDIT_APPARMOR_KILL;
/* quiet known rejects, assumes quiet and kill do not overlap */
if ((sa.aad->fs.request & perms->quiet) &&
AUDIT_MODE(profile) != AUDIT_NOQUIET &&
AUDIT_MODE(profile) != AUDIT_ALL)
sa.aad->fs.request &= ~perms->quiet;
if (!sa.aad->fs.request)
return COMPLAIN_MODE(profile) ? 0 : sa.aad->error;
}
sa.aad->fs.denied = sa.aad->fs.request & ~perms->allow;
return aa_audit(type, profile, gfp, &sa, file_audit_cb);
}
/**
* 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_META_READ;
if (old & MAY_WRITE)
new |= AA_MAY_META_WRITE | AA_MAY_CREATE | AA_MAY_DELETE |
AA_MAY_CHMOD | AA_MAY_CHOWN;
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 (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_META_READ;
/* 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;
}
/**
* 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;
}
/**
* aa_path_perm - do permissions check & audit for @path
* @op: operation being checked
* @profile: 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_profile *profile, struct path *path,
int flags, u32 request, struct path_cond *cond)
{
char *buffer = NULL;
struct file_perms perms = {};
const char *name, *info = NULL;
int error;
flags |= profile->path_flags | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 0);
error = aa_path_name(path, flags, &buffer, &name, &info);
if (error) {
if (error == -ENOENT && is_deleted(path->dentry)) {
/* Access to open files that are deleted are
* give a pass (implicit delegation)
*/
error = 0;
info = NULL;
perms.allow = request;
}
} else {
aa_str_perms(profile->file.dfa, profile->file.start, name, cond,
&perms);
if (request & ~perms.allow)
error = -EACCES;
}
error = aa_audit_file(profile, &perms, GFP_KERNEL, op, request, name,
NULL, cond->uid, info, error);
kfree(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;
}
/**
* aa_path_link - Handle hard link permission check
* @profile: the profile 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_profile *profile, 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, *info = NULL;
struct file_perms lperms, perms;
u32 request = AA_MAY_LINK;
unsigned int state;
int error;
lperms = nullperms;
/* buffer freed below, lname is pointer in buffer */
error = aa_path_name(&link, profile->path_flags, &buffer, &lname,
&info);
if (error)
goto audit;
/* buffer2 freed below, tname is pointer in buffer2 */
error = aa_path_name(&target, profile->path_flags, &buffer2, &tname,
&info);
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";
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:
error = aa_audit_file(profile, &lperms, GFP_KERNEL, OP_LINK, request,
lname, tname, cond.uid, info, error);
kfree(buffer);
kfree(buffer2);
return error;
}
/**
* aa_file_perm - do permission revalidation check & audit for @file
* @op: operation being checked
* @profile: profile 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_profile *profile, struct file *file,
u32 request)
{
struct path_cond cond = {
.uid = file->f_path.dentry->d_inode->i_uid,
.mode = file->f_path.dentry->d_inode->i_mode
};
return aa_path_perm(op, profile, &file->f_path, PATH_DELEGATE_DELETED,
request, &cond);
}
