// SPDX-License-Identifier: GPL-2.0-only /* * AppArmor security module * * This file contains AppArmor mediation of files * * Copyright (C) 1998-2008 Novell/SUSE * Copyright 2009-2010 Canonical Ltd. */ #include <linux/tty.h> #include <linux/fdtable.h> #include <linux/file.h> #include <linux/fs.h> #include <linux/mount.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; } /** * 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(); char str[10]; if (aad(sa)->request & AA_AUDIT_FILE_MASK) { aa_perm_mask_to_str(str, sizeof(str), aa_file_perm_chrs, map_mask_to_chr_mask(aad(sa)->request)); audit_log_format(ab, " requested_mask=\"%s\"", str); } if (aad(sa)->denied & AA_AUDIT_FILE_MASK) { aa_perm_mask_to_str(str, sizeof(str), aa_file_perm_chrs, map_mask_to_chr_mask(aad(sa)->denied)); audit_log_format(ab, " denied_mask=\"%s\"", str); } 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_KERNEL); } 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: true if deleted else false */ static inline bool is_deleted(struct dentry *dentry) { if (d_unlinked(dentry) && d_backing_inode(dentry)->i_nlink == 0) return true; return false; } 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); buffer = aa_get_buffer(false); if (!buffer) return -ENOMEM; error = fn_for_each_confined(label, profile, profile_path_perm(op, profile, path, buffer, request, cond, flags, &perms)); aa_put_buffer(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: true if subset else false */ 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 false; return true; } 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 */ buffer = aa_get_buffer(false); buffer2 = aa_get_buffer(false); error = -ENOMEM; if (!buffer || !buffer2) goto out; error = fn_for_each_confined(label, profile, profile_path_link(profile, &link, buffer, &target, buffer2, &cond)); 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 = i_uid_into_mnt(file_mnt_user_ns(file), file_inode(file)), .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 = 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))) { rcu_read_unlock(); goto done; } flabel = aa_get_newest_label(flabel); rcu_read_unlock(); /* 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); aa_put_label(flabel); done: 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); }