717 lines
20 KiB
C
717 lines
20 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* AppArmor security module
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*
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* This file contains AppArmor mediation of files
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*
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* Copyright (C) 1998-2008 Novell/SUSE
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* Copyright 2009-2010 Canonical Ltd.
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*/
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#include <linux/tty.h>
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#include <linux/fdtable.h>
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#include <linux/file.h>
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#include "include/apparmor.h"
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#include "include/audit.h"
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#include "include/cred.h"
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#include "include/file.h"
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#include "include/match.h"
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#include "include/net.h"
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#include "include/path.h"
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#include "include/policy.h"
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#include "include/label.h"
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static u32 map_mask_to_chr_mask(u32 mask)
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{
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u32 m = mask & PERMS_CHRS_MASK;
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if (mask & AA_MAY_GETATTR)
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m |= MAY_READ;
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if (mask & (AA_MAY_SETATTR | AA_MAY_CHMOD | AA_MAY_CHOWN))
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m |= MAY_WRITE;
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return m;
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}
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/**
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* audit_file_mask - convert mask to permission string
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* @buffer: buffer to write string to (NOT NULL)
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* @mask: permission mask to convert
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*/
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static void audit_file_mask(struct audit_buffer *ab, u32 mask)
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{
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char str[10];
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aa_perm_mask_to_str(str, sizeof(str), aa_file_perm_chrs,
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map_mask_to_chr_mask(mask));
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audit_log_string(ab, str);
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}
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/**
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* file_audit_cb - call back for file specific audit fields
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* @ab: audit_buffer (NOT NULL)
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* @va: audit struct to audit values of (NOT NULL)
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*/
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static void file_audit_cb(struct audit_buffer *ab, void *va)
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{
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struct common_audit_data *sa = va;
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kuid_t fsuid = current_fsuid();
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if (aad(sa)->request & AA_AUDIT_FILE_MASK) {
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audit_log_format(ab, " requested_mask=");
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audit_file_mask(ab, aad(sa)->request);
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}
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if (aad(sa)->denied & AA_AUDIT_FILE_MASK) {
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audit_log_format(ab, " denied_mask=");
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audit_file_mask(ab, aad(sa)->denied);
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}
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if (aad(sa)->request & AA_AUDIT_FILE_MASK) {
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audit_log_format(ab, " fsuid=%d",
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from_kuid(&init_user_ns, fsuid));
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audit_log_format(ab, " ouid=%d",
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from_kuid(&init_user_ns, aad(sa)->fs.ouid));
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}
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if (aad(sa)->peer) {
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audit_log_format(ab, " target=");
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aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
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FLAG_VIEW_SUBNS, GFP_KERNEL);
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} else if (aad(sa)->fs.target) {
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audit_log_format(ab, " target=");
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audit_log_untrustedstring(ab, aad(sa)->fs.target);
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}
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}
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/**
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* aa_audit_file - handle the auditing of file operations
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* @profile: the profile being enforced (NOT NULL)
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* @perms: the permissions computed for the request (NOT NULL)
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* @op: operation being mediated
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* @request: permissions requested
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* @name: name of object being mediated (MAYBE NULL)
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* @target: name of target (MAYBE NULL)
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* @tlabel: target label (MAY BE NULL)
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* @ouid: object uid
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* @info: extra information message (MAYBE NULL)
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* @error: 0 if operation allowed else failure error code
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*
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* Returns: %0 or error on failure
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*/
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int aa_audit_file(struct aa_profile *profile, struct aa_perms *perms,
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const char *op, u32 request, const char *name,
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const char *target, struct aa_label *tlabel,
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kuid_t ouid, const char *info, int error)
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{
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int type = AUDIT_APPARMOR_AUTO;
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DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_TASK, op);
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sa.u.tsk = NULL;
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aad(&sa)->request = request;
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aad(&sa)->name = name;
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aad(&sa)->fs.target = target;
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aad(&sa)->peer = tlabel;
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aad(&sa)->fs.ouid = ouid;
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aad(&sa)->info = info;
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aad(&sa)->error = error;
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sa.u.tsk = NULL;
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if (likely(!aad(&sa)->error)) {
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u32 mask = perms->audit;
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if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
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mask = 0xffff;
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/* mask off perms that are not being force audited */
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aad(&sa)->request &= mask;
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if (likely(!aad(&sa)->request))
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return 0;
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type = AUDIT_APPARMOR_AUDIT;
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} else {
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/* only report permissions that were denied */
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aad(&sa)->request = aad(&sa)->request & ~perms->allow;
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AA_BUG(!aad(&sa)->request);
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if (aad(&sa)->request & perms->kill)
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type = AUDIT_APPARMOR_KILL;
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/* quiet known rejects, assumes quiet and kill do not overlap */
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if ((aad(&sa)->request & perms->quiet) &&
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AUDIT_MODE(profile) != AUDIT_NOQUIET &&
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AUDIT_MODE(profile) != AUDIT_ALL)
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aad(&sa)->request &= ~perms->quiet;
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if (!aad(&sa)->request)
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return aad(&sa)->error;
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}
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aad(&sa)->denied = aad(&sa)->request & ~perms->allow;
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return aa_audit(type, profile, &sa, file_audit_cb);
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}
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/**
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* is_deleted - test if a file has been completely unlinked
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* @dentry: dentry of file to test for deletion (NOT NULL)
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*
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* Returns: %1 if deleted else %0
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*/
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static inline bool is_deleted(struct dentry *dentry)
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{
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if (d_unlinked(dentry) && d_backing_inode(dentry)->i_nlink == 0)
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return 1;
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return 0;
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}
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static int path_name(const char *op, struct aa_label *label,
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const struct path *path, int flags, char *buffer,
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const char **name, struct path_cond *cond, u32 request)
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{
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struct aa_profile *profile;
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const char *info = NULL;
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int error;
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error = aa_path_name(path, flags, buffer, name, &info,
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labels_profile(label)->disconnected);
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if (error) {
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fn_for_each_confined(label, profile,
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aa_audit_file(profile, &nullperms, op, request, *name,
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NULL, NULL, cond->uid, info, error));
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return error;
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}
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return 0;
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}
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/**
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* map_old_perms - map old file perms layout to the new layout
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* @old: permission set in old mapping
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*
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* Returns: new permission mapping
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*/
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static u32 map_old_perms(u32 old)
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{
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u32 new = old & 0xf;
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if (old & MAY_READ)
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new |= AA_MAY_GETATTR | AA_MAY_OPEN;
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if (old & MAY_WRITE)
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new |= AA_MAY_SETATTR | AA_MAY_CREATE | AA_MAY_DELETE |
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AA_MAY_CHMOD | AA_MAY_CHOWN | AA_MAY_OPEN;
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if (old & 0x10)
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new |= AA_MAY_LINK;
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/* the old mapping lock and link_subset flags where overlaid
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* and use was determined by part of a pair that they were in
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*/
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if (old & 0x20)
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new |= AA_MAY_LOCK | AA_LINK_SUBSET;
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if (old & 0x40) /* AA_EXEC_MMAP */
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new |= AA_EXEC_MMAP;
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return new;
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}
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/**
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* aa_compute_fperms - convert dfa compressed perms to internal perms
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* @dfa: dfa to compute perms for (NOT NULL)
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* @state: state in dfa
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* @cond: conditions to consider (NOT NULL)
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*
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* TODO: convert from dfa + state to permission entry, do computation conversion
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* at load time.
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*
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* Returns: computed permission set
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*/
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struct aa_perms aa_compute_fperms(struct aa_dfa *dfa, unsigned int state,
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struct path_cond *cond)
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{
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/* FIXME: change over to new dfa format
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* currently file perms are encoded in the dfa, new format
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* splits the permissions from the dfa. This mapping can be
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* done at profile load
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*/
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struct aa_perms perms = { };
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if (uid_eq(current_fsuid(), cond->uid)) {
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perms.allow = map_old_perms(dfa_user_allow(dfa, state));
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perms.audit = map_old_perms(dfa_user_audit(dfa, state));
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perms.quiet = map_old_perms(dfa_user_quiet(dfa, state));
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perms.xindex = dfa_user_xindex(dfa, state);
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} else {
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perms.allow = map_old_perms(dfa_other_allow(dfa, state));
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perms.audit = map_old_perms(dfa_other_audit(dfa, state));
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perms.quiet = map_old_perms(dfa_other_quiet(dfa, state));
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perms.xindex = dfa_other_xindex(dfa, state);
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}
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perms.allow |= AA_MAY_GETATTR;
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/* change_profile wasn't determined by ownership in old mapping */
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if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
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perms.allow |= AA_MAY_CHANGE_PROFILE;
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if (ACCEPT_TABLE(dfa)[state] & 0x40000000)
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perms.allow |= AA_MAY_ONEXEC;
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return perms;
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}
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/**
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* aa_str_perms - find permission that match @name
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* @dfa: to match against (MAYBE NULL)
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* @state: state to start matching in
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* @name: string to match against dfa (NOT NULL)
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* @cond: conditions to consider for permission set computation (NOT NULL)
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* @perms: Returns - the permissions found when matching @name
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*
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* Returns: the final state in @dfa when beginning @start and walking @name
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*/
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unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,
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const char *name, struct path_cond *cond,
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struct aa_perms *perms)
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{
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unsigned int state;
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state = aa_dfa_match(dfa, start, name);
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*perms = aa_compute_fperms(dfa, state, cond);
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return state;
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}
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int __aa_path_perm(const char *op, struct aa_profile *profile, const char *name,
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u32 request, struct path_cond *cond, int flags,
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struct aa_perms *perms)
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{
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int e = 0;
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if (profile_unconfined(profile))
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return 0;
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aa_str_perms(profile->file.dfa, profile->file.start, name, cond, perms);
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if (request & ~perms->allow)
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e = -EACCES;
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return aa_audit_file(profile, perms, op, request, name, NULL, NULL,
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cond->uid, NULL, e);
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}
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static int profile_path_perm(const char *op, struct aa_profile *profile,
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const struct path *path, char *buffer, u32 request,
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struct path_cond *cond, int flags,
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struct aa_perms *perms)
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{
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const char *name;
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int error;
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if (profile_unconfined(profile))
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return 0;
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error = path_name(op, &profile->label, path,
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flags | profile->path_flags, buffer, &name, cond,
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request);
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if (error)
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return error;
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return __aa_path_perm(op, profile, name, request, cond, flags,
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perms);
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}
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/**
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* aa_path_perm - do permissions check & audit for @path
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* @op: operation being checked
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* @label: profile being enforced (NOT NULL)
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* @path: path to check permissions of (NOT NULL)
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* @flags: any additional path flags beyond what the profile specifies
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* @request: requested permissions
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* @cond: conditional info for this request (NOT NULL)
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*
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* Returns: %0 else error if access denied or other error
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*/
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int aa_path_perm(const char *op, struct aa_label *label,
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const struct path *path, int flags, u32 request,
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struct path_cond *cond)
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{
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struct aa_perms perms = {};
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struct aa_profile *profile;
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char *buffer = NULL;
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int error;
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flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR :
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0);
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buffer = aa_get_buffer(false);
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if (!buffer)
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return -ENOMEM;
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error = fn_for_each_confined(label, profile,
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profile_path_perm(op, profile, path, buffer, request,
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cond, flags, &perms));
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aa_put_buffer(buffer);
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return error;
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}
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/**
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* xindex_is_subset - helper for aa_path_link
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* @link: link permission set
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* @target: target permission set
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*
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* test target x permissions are equal OR a subset of link x permissions
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* this is done as part of the subset test, where a hardlink must have
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* a subset of permissions that the target has.
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*
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* Returns: %1 if subset else %0
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*/
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static inline bool xindex_is_subset(u32 link, u32 target)
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{
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if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
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((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
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return 0;
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return 1;
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}
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static int profile_path_link(struct aa_profile *profile,
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const struct path *link, char *buffer,
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const struct path *target, char *buffer2,
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struct path_cond *cond)
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{
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const char *lname, *tname = NULL;
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struct aa_perms lperms = {}, perms;
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const char *info = NULL;
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u32 request = AA_MAY_LINK;
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unsigned int state;
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int error;
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error = path_name(OP_LINK, &profile->label, link, profile->path_flags,
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buffer, &lname, cond, AA_MAY_LINK);
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if (error)
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goto audit;
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/* buffer2 freed below, tname is pointer in buffer2 */
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error = path_name(OP_LINK, &profile->label, target, profile->path_flags,
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buffer2, &tname, cond, AA_MAY_LINK);
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if (error)
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goto audit;
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error = -EACCES;
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/* aa_str_perms - handles the case of the dfa being NULL */
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state = aa_str_perms(profile->file.dfa, profile->file.start, lname,
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cond, &lperms);
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if (!(lperms.allow & AA_MAY_LINK))
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goto audit;
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/* test to see if target can be paired with link */
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state = aa_dfa_null_transition(profile->file.dfa, state);
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aa_str_perms(profile->file.dfa, state, tname, cond, &perms);
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/* force audit/quiet masks for link are stored in the second entry
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* in the link pair.
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*/
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lperms.audit = perms.audit;
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lperms.quiet = perms.quiet;
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lperms.kill = perms.kill;
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if (!(perms.allow & AA_MAY_LINK)) {
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info = "target restricted";
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lperms = perms;
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goto audit;
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}
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/* done if link subset test is not required */
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if (!(perms.allow & AA_LINK_SUBSET))
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goto done_tests;
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/* Do link perm subset test requiring allowed permission on link are
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* a subset of the allowed permissions on target.
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*/
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aa_str_perms(profile->file.dfa, profile->file.start, tname, cond,
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&perms);
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/* AA_MAY_LINK is not considered in the subset test */
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request = lperms.allow & ~AA_MAY_LINK;
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lperms.allow &= perms.allow | AA_MAY_LINK;
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request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
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if (request & ~lperms.allow) {
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goto audit;
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} else if ((lperms.allow & MAY_EXEC) &&
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!xindex_is_subset(lperms.xindex, perms.xindex)) {
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lperms.allow &= ~MAY_EXEC;
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request |= MAY_EXEC;
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info = "link not subset of target";
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goto audit;
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}
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done_tests:
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error = 0;
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audit:
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return aa_audit_file(profile, &lperms, OP_LINK, request, lname, tname,
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NULL, cond->uid, info, error);
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}
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/**
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* aa_path_link - Handle hard link permission check
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* @label: the label being enforced (NOT NULL)
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* @old_dentry: the target dentry (NOT NULL)
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* @new_dir: directory the new link will be created in (NOT NULL)
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* @new_dentry: the link being created (NOT NULL)
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*
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* Handle the permission test for a link & target pair. Permission
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* is encoded as a pair where the link permission is determined
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* first, and if allowed, the target is tested. The target test
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* is done from the point of the link match (not start of DFA)
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* making the target permission dependent on the link permission match.
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*
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* The subset test if required forces that permissions granted
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* on link are a subset of the permission granted to target.
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*
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* Returns: %0 if allowed else error
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*/
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int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
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const struct path *new_dir, struct dentry *new_dentry)
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{
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struct path link = { .mnt = new_dir->mnt, .dentry = new_dentry };
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struct path target = { .mnt = new_dir->mnt, .dentry = old_dentry };
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struct path_cond cond = {
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d_backing_inode(old_dentry)->i_uid,
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d_backing_inode(old_dentry)->i_mode
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};
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char *buffer = NULL, *buffer2 = NULL;
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struct aa_profile *profile;
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int error;
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/* buffer freed below, lname is pointer in buffer */
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buffer = aa_get_buffer(false);
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buffer2 = aa_get_buffer(false);
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error = -ENOMEM;
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if (!buffer || !buffer2)
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goto out;
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error = fn_for_each_confined(label, profile,
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profile_path_link(profile, &link, buffer, &target,
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buffer2, &cond));
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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, 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 = {};
|
|
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);
|
|
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, 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);
|
|
|
|
aa_put_buffer(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
|
|
* @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, 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 = aa_get_newest_label(rcu_dereference(fctx->label));
|
|
rcu_read_unlock();
|
|
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, in_atomic);
|
|
|
|
else if (S_ISSOCK(file_inode(file)->i_mode))
|
|
error = __file_sock_perm(op, label, flabel, file, request,
|
|
denied);
|
|
done:
|
|
aa_put_label(flabel);
|
|
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,
|
|
IN_ATOMIC))
|
|
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),
|
|
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 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);
|
|
}
|