diff options
Diffstat (limited to 'security/apparmor/file.c')
| -rw-r--r-- | security/apparmor/file.c | 711 |
1 files changed, 711 insertions, 0 deletions
diff --git a/security/apparmor/file.c b/security/apparmor/file.c new file mode 100644 index 000000000..e1b7e9360 --- /dev/null +++ b/security/apparmor/file.c @@ -0,0 +1,711 @@ +// 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); +} |