- 根目录:
- security
- apparmor
- domain.c
/*
* AppArmor security module
*
* This file contains AppArmor policy attachment and domain transitions
*
* Copyright (C) 2002-2008 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/errno.h>
#include <linux/fdtable.h>
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/syscalls.h>
#include <linux/tracehook.h>
#include <linux/personality.h>
#include "include/audit.h"
#include "include/apparmorfs.h"
#include "include/context.h"
#include "include/domain.h"
#include "include/file.h"
#include "include/ipc.h"
#include "include/match.h"
#include "include/path.h"
#include "include/policy.h"
/**
* aa_free_domain_entries - free entries in a domain table
* @domain: the domain table to free (MAYBE NULL)
*/
void aa_free_domain_entries(struct aa_domain *domain)
{
int i;
if (domain) {
if (!domain->table)
return;
for (i = 0; i < domain->size; i++)
kzfree(domain->table[i]);
kzfree(domain->table);
domain->table = NULL;
}
}
/**
* may_change_ptraced_domain - check if can change profile on ptraced task
* @to_profile: profile to change to (NOT NULL)
*
* Check if current is ptraced and if so if the tracing task is allowed
* to trace the new domain
*
* Returns: %0 or error if change not allowed
*/
static int may_change_ptraced_domain(struct aa_profile *to_profile)
{
struct task_struct *tracer;
struct aa_profile *tracerp = NULL;
int error = 0;
rcu_read_lock();
tracer = ptrace_parent(current);
if (tracer)
/* released below */
tracerp = aa_get_task_profile(tracer);
/* not ptraced */
if (!tracer || unconfined(tracerp))
goto out;
error = aa_may_ptrace(tracerp, to_profile, PTRACE_MODE_ATTACH);
out:
rcu_read_unlock();
aa_put_profile(tracerp);
return error;
}
/**
* change_profile_perms - find permissions for change_profile
* @profile: the current profile (NOT NULL)
* @ns: the namespace being switched to (NOT NULL)
* @name: the name of the profile to change to (NOT NULL)
* @request: requested perms
* @start: state to start matching in
*
* Returns: permission set
*/
static struct file_perms change_profile_perms(struct aa_profile *profile,
struct aa_namespace *ns,
const char *name, u32 request,
unsigned int start)
{
struct file_perms perms;
struct path_cond cond = { };
unsigned int state;
if (unconfined(profile)) {
perms.allow = AA_MAY_CHANGE_PROFILE | AA_MAY_ONEXEC;
perms.audit = perms.quiet = perms.kill = 0;
return perms;
} else if (!profile->file.dfa) {
return nullperms;
} else if ((ns == profile->ns)) {
/* try matching against rules with out namespace prepended */
aa_str_perms(profile->file.dfa, start, name, &cond, &perms);
if (COMBINED_PERM_MASK(perms) & request)
return perms;
}
/* try matching with namespace name and then profile */
state = aa_dfa_match(profile->file.dfa, start, ns->base.name);
state = aa_dfa_match_len(profile->file.dfa, state, ":", 1);
aa_str_perms(profile->file.dfa, state, name, &cond, &perms);
return perms;
}
/**
* __attach_match_ - find an attachment match
* @name - to match against (NOT NULL)
* @head - profile list to walk (NOT NULL)
*
* Do a linear search on the profiles in the list. There is a matching
* preference where an exact match is preferred over a name which uses
* expressions to match, and matching expressions with the greatest
* xmatch_len are preferred.
*
* Requires: @head not be shared or have appropriate locks held
*
* Returns: profile or NULL if no match found
*/
static struct aa_profile *__attach_match(const char *name,
struct list_head *head)
{
int len = 0;
struct aa_profile *profile, *candidate = NULL;
list_for_each_entry_rcu(profile, head, base.list) {
if (profile->flags & PFLAG_NULL)
continue;
if (profile->xmatch && profile->xmatch_len > len) {
unsigned int state = aa_dfa_match(profile->xmatch,
DFA_START, name);
u32 perm = dfa_user_allow(profile->xmatch, state);
/* any accepting state means a valid match. */
if (perm & MAY_EXEC) {
candidate = profile;
len = profile->xmatch_len;
}
} else if (!strcmp(profile->base.name, name))
/* exact non-re match, no more searching required */
return profile;
}
return candidate;
}
/**
* find_attach - do attachment search for unconfined processes
* @ns: the current namespace (NOT NULL)
* @list: list to search (NOT NULL)
* @name: the executable name to match against (NOT NULL)
*
* Returns: profile or NULL if no match found
*/
static struct aa_profile *find_attach(struct aa_namespace *ns,
struct list_head *list, const char *name)
{
struct aa_profile *profile;
rcu_read_lock();
profile = aa_get_profile(__attach_match(name, list));
rcu_read_unlock();
return profile;
}
/**
* separate_fqname - separate the namespace and profile names
* @fqname: the fqname name to split (NOT NULL)
* @ns_name: the namespace name if it exists (NOT NULL)
*
* This is the xtable equivalent routine of aa_split_fqname. It finds the
* split in an xtable fqname which contains an embedded \0 instead of a :
* if a namespace is specified. This is done so the xtable is constant and
* isn't re-split on every lookup.
*
* Either the profile or namespace name may be optional but if the namespace
* is specified the profile name termination must be present. This results
* in the following possible encodings:
* profile_name\0
* :ns_name\0profile_name\0
* :ns_name\0\0
*
* NOTE: the xtable fqname is pre-validated at load time in unpack_trans_table
*
* Returns: profile name if it is specified else NULL
*/
static const char *separate_fqname(const char *fqname, const char **ns_name)
{
const char *name;
if (fqname[0] == ':') {
/* In this case there is guaranteed to be two \0 terminators
* in the string. They are verified at load time by
* by unpack_trans_table
*/
*ns_name = fqname + 1; /* skip : */
name = *ns_name + strlen(*ns_name) + 1;
if (!*name)
name = NULL;
} else {
*ns_name = NULL;
name = fqname;
}
return name;
}
static const char *next_name(int xtype, const char *name)
{
return NULL;
}
/**
* x_table_lookup - lookup an x transition name via transition table
* @profile: current profile (NOT NULL)
* @xindex: index into x transition table
*
* Returns: refcounted profile, or NULL on failure (MAYBE NULL)
*/
static struct aa_profile *x_table_lookup(struct aa_profile *profile, u32 xindex)
{
struct aa_profile *new_profile = NULL;
struct aa_namespace *ns = profile->ns;
u32 xtype = xindex & AA_X_TYPE_MASK;
int index = xindex & AA_X_INDEX_MASK;
const char *name;
/* index is guaranteed to be in range, validated at load time */
for (name = profile->file.trans.table[index]; !new_profile && name;
name = next_name(xtype, name)) {
struct aa_namespace *new_ns;
const char *xname = NULL;
new_ns = NULL;
if (xindex & AA_X_CHILD) {
/* release by caller */
new_profile = aa_find_child(profile, name);
continue;
} else if (*name == ':') {
/* switching namespace */
const char *ns_name;
xname = name = separate_fqname(name, &ns_name);
if (!xname)
/* no name so use profile name */
xname = profile->base.hname;
if (*ns_name == '@') {
/* TODO: variable support */
;
}
/* released below */
new_ns = aa_find_namespace(ns, ns_name);
if (!new_ns)
continue;
} else if (*name == '@') {
/* TODO: variable support */
continue;
} else {
/* basic namespace lookup */
xname = name;
}
/* released by caller */
new_profile = aa_lookup_profile(new_ns ? new_ns : ns, xname);
aa_put_namespace(new_ns);
}
/* released by caller */
return new_profile;
}
/**
* x_to_profile - get target profile for a given xindex
* @profile: current profile (NOT NULL)
* @name: name to lookup (NOT NULL)
* @xindex: index into x transition table
*
* find profile for a transition index
*
* Returns: refcounted profile or NULL if not found available
*/
static struct aa_profile *x_to_profile(struct aa_profile *profile,
const char *name, u32 xindex)
{
struct aa_profile *new_profile = NULL;
struct aa_namespace *ns = profile->ns;
u32 xtype = xindex & AA_X_TYPE_MASK;
switch (xtype) {
case AA_X_NONE:
/* fail exec unless ix || ux fallback - handled by caller */
return NULL;
case AA_X_NAME:
if (xindex & AA_X_CHILD)
/* released by caller */
new_profile = find_attach(ns, &profile->base.profiles,
name);
else
/* released by caller */
new_profile = find_attach(ns, &ns->base.profiles,
name);
break;
case AA_X_TABLE:
/* released by caller */
new_profile = x_table_lookup(profile, xindex);
break;
}
/* released by caller */
return new_profile;
}
/**
* apparmor_bprm_set_creds - set the new creds on the bprm struct
* @bprm: binprm for the exec (NOT NULL)
*
* Returns: %0 or error on failure
*/
int apparmor_bprm_set_creds(struct linux_binprm *bprm)
{
struct aa_task_cxt *cxt;
struct aa_profile *profile, *new_profile = NULL;
struct aa_namespace *ns;
char *buffer = NULL;
unsigned int state;
struct file_perms perms = {};
struct path_cond cond = {
file_inode(bprm->file)->i_uid,
file_inode(bprm->file)->i_mode
};
const char *name = NULL, *target = NULL, *info = NULL;
int error = 0;
if (bprm->cred_prepared)
return 0;
cxt = cred_cxt(bprm->cred);
BUG_ON(!cxt);
profile = aa_get_newest_profile(cxt->profile);
/*
* get the namespace from the replacement profile as replacement
* can change the namespace
*/
ns = profile->ns;
state = profile->file.start;
/* buffer freed below, name is pointer into buffer */
error = aa_path_name(&bprm->file->f_path, profile->path_flags, &buffer,
&name, &info);
if (error) {
if (unconfined(profile) ||
(profile->flags & PFLAG_IX_ON_NAME_ERROR))
error = 0;
name = bprm->filename;
goto audit;
}
/* Test for onexec first as onexec directives override other
* x transitions.
*/
if (unconfined(profile)) {
/* unconfined task */
if (cxt->onexec)
/* change_profile on exec already been granted */
new_profile = aa_get_profile(cxt->onexec);
else
new_profile = find_attach(ns, &ns->base.profiles, name);
if (!new_profile)
goto cleanup;
/*
* NOTE: Domain transitions from unconfined are allowed
* even when no_new_privs is set because this aways results
* in a further reduction of permissions.
*/
goto apply;
}
/* find exec permissions for name */
state = aa_str_perms(profile->file.dfa, state, name, &cond, &perms);
if (cxt->onexec) {
struct file_perms cp;
info = "change_profile onexec";
if (!(perms.allow & AA_MAY_ONEXEC))
goto audit;
/* test if this exec can be paired with change_profile onexec.
* onexec permission is linked to exec with a standard pairing
* exec\0change_profile
*/
state = aa_dfa_null_transition(profile->file.dfa, state);
cp = change_profile_perms(profile, cxt->onexec->ns,
cxt->onexec->base.name,
AA_MAY_ONEXEC, state);
if (!(cp.allow & AA_MAY_ONEXEC))
goto audit;
new_profile = aa_get_newest_profile(cxt->onexec);
goto apply;
}
if (perms.allow & MAY_EXEC) {
/* exec permission determine how to transition */
new_profile = x_to_profile(profile, name, perms.xindex);
if (!new_profile) {
if (perms.xindex & AA_X_INHERIT) {
/* (p|c|n)ix - don't change profile but do
* use the newest version, which was picked
* up above when getting profile
*/
info = "ix fallback";
new_profile = aa_get_profile(profile);
goto x_clear;
} else if (perms.xindex & AA_X_UNCONFINED) {
new_profile = aa_get_newest_profile(ns->unconfined);
info = "ux fallback";
} else {
error = -ENOENT;
info = "profile not found";
/* remove MAY_EXEC to audit as failure */
perms.allow &= ~MAY_EXEC;
}
}
} else if (COMPLAIN_MODE(profile)) {
/* no exec permission - are we in learning mode */
new_profile = aa_new_null_profile(profile, 0);
if (!new_profile) {
error = -ENOMEM;
info = "could not create null profile";
} else {
error = -EACCES;
target = new_profile->base.hname;
}
perms.xindex |= AA_X_UNSAFE;
} else
/* fail exec */
error = -EACCES;
/*
* Policy has specified a domain transition, if no_new_privs then
* fail the exec.
*/
if (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS) {
aa_put_profile(new_profile);
error = -EPERM;
goto cleanup;
}
if (!new_profile)
goto audit;
if (bprm->unsafe & LSM_UNSAFE_SHARE) {
/* FIXME: currently don't mediate shared state */
;
}
if (bprm->unsafe & (LSM_UNSAFE_PTRACE | LSM_UNSAFE_PTRACE_CAP)) {
error = may_change_ptraced_domain(new_profile);
if (error) {
aa_put_profile(new_profile);
goto audit;
}
}
/* Determine if secure exec is needed.
* Can be at this point for the following reasons:
* 1. unconfined switching to confined
* 2. confined switching to different confinement
* 3. confined switching to unconfined
*
* Cases 2 and 3 are marked as requiring secure exec
* (unless policy specified "unsafe exec")
*
* bprm->unsafe is used to cache the AA_X_UNSAFE permission
* to avoid having to recompute in secureexec
*/
if (!(perms.xindex & AA_X_UNSAFE)) {
AA_DEBUG("scrubbing environment variables for %s profile=%s\n",
name, new_profile->base.hname);
bprm->unsafe |= AA_SECURE_X_NEEDED;
}
apply:
target = new_profile->base.hname;
/* when transitioning profiles clear unsafe personality bits */
bprm->per_clear |= PER_CLEAR_ON_SETID;
x_clear:
aa_put_profile(cxt->profile);
/* transfer new profile reference will be released when cxt is freed */
cxt->profile = new_profile;
/* clear out all temporary/transitional state from the context */
aa_clear_task_cxt_trans(cxt);
audit:
error = aa_audit_file(profile, &perms, GFP_KERNEL, OP_EXEC, MAY_EXEC,
name, target, cond.uid, info, error);
cleanup:
aa_put_profile(profile);
kfree(buffer);
return error;
}
/**
* apparmor_bprm_secureexec - determine if secureexec is needed
* @bprm: binprm for exec (NOT NULL)
*
* Returns: %1 if secureexec is needed else %0
*/
int apparmor_bprm_secureexec(struct linux_binprm *bprm)
{
/* the decision to use secure exec is computed in set_creds
* and stored in bprm->unsafe.
*/
if (bprm->unsafe & AA_SECURE_X_NEEDED)
return 1;
return 0;
}
/**
* apparmor_bprm_committing_creds - do task cleanup on committing new creds
* @bprm: binprm for the exec (NOT NULL)
*/
void apparmor_bprm_committing_creds(struct linux_binprm *bprm)
{
struct aa_profile *profile = __aa_current_profile();
struct aa_task_cxt *new_cxt = cred_cxt(bprm->cred);
/* bail out if unconfined or not changing profile */
if ((new_cxt->profile == profile) ||
(unconfined(new_cxt->profile)))
return;
current->pdeath_signal = 0;
/* reset soft limits and set hard limits for the new profile */
__aa_transition_rlimits(profile, new_cxt->profile);
}
/**
* apparmor_bprm_commited_cred - do cleanup after new creds committed
* @bprm: binprm for the exec (NOT NULL)
*/
void apparmor_bprm_committed_creds(struct linux_binprm *bprm)
{
/* TODO: cleanup signals - ipc mediation */
return;
}
/*
* Functions for self directed profile change
*/
/**
* new_compound_name - create an hname with @n2 appended to @n1
* @n1: base of hname (NOT NULL)
* @n2: name to append (NOT NULL)
*
* Returns: new name or NULL on error
*/
static char *new_compound_name(const char *n1, const char *n2)
{
char *name = kmalloc(strlen(n1) + strlen(n2) + 3, GFP_KERNEL);
if (name)
sprintf(name, "%s//%s", n1, n2);
return name;
}
/**
* aa_change_hat - change hat to/from subprofile
* @hats: vector of hat names to try changing into (MAYBE NULL if @count == 0)
* @count: number of hat names in @hats
* @token: magic value to validate the hat change
* @permtest: true if this is just a permission test
*
* Change to the first profile specified in @hats that exists, and store
* the @hat_magic in the current task context. If the count == 0 and the
* @token matches that stored in the current task context, return to the
* top level profile.
*
* Returns %0 on success, error otherwise.
*/
int aa_change_hat(const char *hats[], int count, u64 token, bool permtest)
{
const struct cred *cred;
struct aa_task_cxt *cxt;
struct aa_profile *profile, *previous_profile, *hat = NULL;
char *name = NULL;
int i;
struct file_perms perms = {};
const char *target = NULL, *info = NULL;
int error = 0;
/*
* Fail explicitly requested domain transitions if no_new_privs.
* There is no exception for unconfined as change_hat is not
* available.
*/
if (task_no_new_privs(current))
return -EPERM;
/* released below */
cred = get_current_cred();
cxt = cred_cxt(cred);
profile = aa_cred_profile(cred);
previous_profile = cxt->previous;
if (unconfined(profile)) {
info = "unconfined";
error = -EPERM;
goto audit;
}
if (count) {
/* attempting to change into a new hat or switch to a sibling */
struct aa_profile *root;
if (PROFILE_IS_HAT(profile))
root = aa_get_profile_rcu(&profile->parent);
else
root = aa_get_profile(profile);
/* find first matching hat */
for (i = 0; i < count && !hat; i++)
/* released below */
hat = aa_find_child(root, hats[i]);
if (!hat) {
if (!COMPLAIN_MODE(root) || permtest) {
if (list_empty(&root->base.profiles))
error = -ECHILD;
else
error = -ENOENT;
aa_put_profile(root);
goto out;
}
/*
* In complain mode and failed to match any hats.
* Audit the failure is based off of the first hat
* supplied. This is done due how userspace
* interacts with change_hat.
*
* TODO: Add logging of all failed hats
*/
/* freed below */
name = new_compound_name(root->base.hname, hats[0]);
aa_put_profile(root);
target = name;
/* released below */
hat = aa_new_null_profile(profile, 1);
if (!hat) {
info = "failed null profile create";
error = -ENOMEM;
goto audit;
}
} else {
aa_put_profile(root);
target = hat->base.hname;
if (!PROFILE_IS_HAT(hat)) {
info = "target not hat";
error = -EPERM;
goto audit;
}
}
error = may_change_ptraced_domain(hat);
if (error) {
info = "ptraced";
error = -EPERM;
goto audit;
}
if (!permtest) {
error = aa_set_current_hat(hat, token);
if (error == -EACCES)
/* kill task in case of brute force attacks */
perms.kill = AA_MAY_CHANGEHAT;
else if (name && !error)
/* reset error for learning of new hats */
error = -ENOENT;
}
} else if (previous_profile) {
/* Return to saved profile. Kill task if restore fails
* to avoid brute force attacks
*/
target = previous_profile->base.hname;
error = aa_restore_previous_profile(token);
perms.kill = AA_MAY_CHANGEHAT;
} else
/* ignore restores when there is no saved profile */
goto out;
audit:
if (!permtest)
error = aa_audit_file(profile, &perms, GFP_KERNEL,
OP_CHANGE_HAT, AA_MAY_CHANGEHAT, NULL,
target, GLOBAL_ROOT_UID, info, error);
out:
aa_put_profile(hat);
kfree(name);
put_cred(cred);
return error;
}
/**
* aa_change_profile - perform a one-way profile transition
* @ns_name: name of the profile namespace to change to (MAYBE NULL)
* @hname: name of profile to change to (MAYBE NULL)
* @onexec: whether this transition is to take place immediately or at exec
* @permtest: true if this is just a permission test
*
* Change to new profile @name. Unlike with hats, there is no way
* to change back. If @name isn't specified the current profile name is
* used.
* If @onexec then the transition is delayed until
* the next exec.
*
* Returns %0 on success, error otherwise.
*/
int aa_change_profile(const char *ns_name, const char *hname, bool onexec,
bool permtest)
{
const struct cred *cred;
struct aa_profile *profile, *target = NULL;
struct aa_namespace *ns = NULL;
struct file_perms perms = {};
const char *name = NULL, *info = NULL;
int op, error = 0;
u32 request;
if (!hname && !ns_name)
return -EINVAL;
if (onexec) {
request = AA_MAY_ONEXEC;
op = OP_CHANGE_ONEXEC;
} else {
request = AA_MAY_CHANGE_PROFILE;
op = OP_CHANGE_PROFILE;
}
cred = get_current_cred();
profile = aa_cred_profile(cred);
/*
* Fail explicitly requested domain transitions if no_new_privs
* and not unconfined.
* Domain transitions from unconfined are allowed even when
* no_new_privs is set because this aways results in a reduction
* of permissions.
*/
if (task_no_new_privs(current) && !unconfined(profile)) {
put_cred(cred);
return -EPERM;
}
if (ns_name) {
/* released below */
ns = aa_find_namespace(profile->ns, ns_name);
if (!ns) {
/* we don't create new namespace in complain mode */
name = ns_name;
info = "namespace not found";
error = -ENOENT;
goto audit;
}
} else
/* released below */
ns = aa_get_namespace(profile->ns);
/* if the name was not specified, use the name of the current profile */
if (!hname) {
if (unconfined(profile))
hname = ns->unconfined->base.hname;
else
hname = profile->base.hname;
}
perms = change_profile_perms(profile, ns, hname, request,
profile->file.start);
if (!(perms.allow & request)) {
error = -EACCES;
goto audit;
}
/* released below */
target = aa_lookup_profile(ns, hname);
if (!target) {
info = "profile not found";
error = -ENOENT;
if (permtest || !COMPLAIN_MODE(profile))
goto audit;
/* released below */
target = aa_new_null_profile(profile, 0);
if (!target) {
info = "failed null profile create";
error = -ENOMEM;
goto audit;
}
}
/* check if tracing task is allowed to trace target domain */
error = may_change_ptraced_domain(target);
if (error) {
info = "ptrace prevents transition";
goto audit;
}
if (permtest)
goto audit;
if (onexec)
error = aa_set_current_onexec(target);
else
error = aa_replace_current_profile(target);
audit:
if (!permtest)
error = aa_audit_file(profile, &perms, GFP_KERNEL, op, request,
name, hname, GLOBAL_ROOT_UID, info, error);
aa_put_namespace(ns);
aa_put_profile(target);
put_cred(cred);
return error;
}