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-rw-r--r--security/apparmor/file.c457
1 files changed, 457 insertions, 0 deletions
diff --git a/security/apparmor/file.c b/security/apparmor/file.c
new file mode 100644
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--- /dev/null
+++ b/security/apparmor/file.c
@@ -0,0 +1,457 @@
+/*
+ * AppArmor security module
+ *
+ * This file contains AppArmor mediation of files
+ *
+ * Copyright (C) 1998-2008 Novell/SUSE
+ * Copyright 2009-2010 Canonical Ltd.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, version 2 of the
+ * License.
+ */
+
+#include "include/apparmor.h"
+#include "include/audit.h"
+#include "include/file.h"
+#include "include/match.h"
+#include "include/path.h"
+#include "include/policy.h"
+
+struct file_perms nullperms;
+
+
+/**
+ * audit_file_mask - convert mask to permission string
+ * @buffer: buffer to write string to (NOT NULL)
+ * @mask: permission mask to convert
+ */
+static void audit_file_mask(struct audit_buffer *ab, u32 mask)
+{
+ char str[10];
+
+ char *m = str;
+
+ if (mask & AA_EXEC_MMAP)
+ *m++ = 'm';
+ if (mask & (MAY_READ | AA_MAY_META_READ))
+ *m++ = 'r';
+ if (mask & (MAY_WRITE | AA_MAY_META_WRITE | AA_MAY_CHMOD |
+ AA_MAY_CHOWN))
+ *m++ = 'w';
+ else if (mask & MAY_APPEND)
+ *m++ = 'a';
+ if (mask & AA_MAY_CREATE)
+ *m++ = 'c';
+ if (mask & AA_MAY_DELETE)
+ *m++ = 'd';
+ if (mask & AA_MAY_LINK)
+ *m++ = 'l';
+ if (mask & AA_MAY_LOCK)
+ *m++ = 'k';
+ if (mask & MAY_EXEC)
+ *m++ = 'x';
+ *m = '\0';
+
+ audit_log_string(ab, str);
+}
+
+/**
+ * file_audit_cb - call back for file specific audit fields
+ * @ab: audit_buffer (NOT NULL)
+ * @va: audit struct to audit values of (NOT NULL)
+ */
+static void file_audit_cb(struct audit_buffer *ab, void *va)
+{
+ struct common_audit_data *sa = va;
+ uid_t fsuid = current_fsuid();
+
+ if (sa->aad.fs.request & AA_AUDIT_FILE_MASK) {
+ audit_log_format(ab, " requested_mask=");
+ audit_file_mask(ab, sa->aad.fs.request);
+ }
+ if (sa->aad.fs.denied & AA_AUDIT_FILE_MASK) {
+ audit_log_format(ab, " denied_mask=");
+ audit_file_mask(ab, sa->aad.fs.denied);
+ }
+ if (sa->aad.fs.request & AA_AUDIT_FILE_MASK) {
+ audit_log_format(ab, " fsuid=%d", fsuid);
+ audit_log_format(ab, " ouid=%d", sa->aad.fs.ouid);
+ }
+
+ if (sa->aad.fs.target) {
+ audit_log_format(ab, " target=");
+ audit_log_untrustedstring(ab, sa->aad.fs.target);
+ }
+}
+
+/**
+ * aa_audit_file - handle the auditing of file operations
+ * @profile: the profile being enforced (NOT NULL)
+ * @perms: the permissions computed for the request (NOT NULL)
+ * @gfp: allocation flags
+ * @op: operation being mediated
+ * @request: permissions requested
+ * @name: name of object being mediated (MAYBE NULL)
+ * @target: name of target (MAYBE NULL)
+ * @ouid: object uid
+ * @info: extra information message (MAYBE NULL)
+ * @error: 0 if operation allowed else failure error code
+ *
+ * Returns: %0 or error on failure
+ */
+int aa_audit_file(struct aa_profile *profile, struct file_perms *perms,
+ gfp_t gfp, int op, u32 request, const char *name,
+ const char *target, uid_t ouid, const char *info, int error)
+{
+ int type = AUDIT_APPARMOR_AUTO;
+ struct common_audit_data sa;
+ COMMON_AUDIT_DATA_INIT(&sa, NONE);
+ sa.aad.op = op,
+ sa.aad.fs.request = request;
+ sa.aad.name = name;
+ sa.aad.fs.target = target;
+ sa.aad.fs.ouid = ouid;
+ sa.aad.info = info;
+ sa.aad.error = error;
+
+ if (likely(!sa.aad.error)) {
+ u32 mask = perms->audit;
+
+ if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
+ mask = 0xffff;
+
+ /* mask off perms that are not being force audited */
+ sa.aad.fs.request &= mask;
+
+ if (likely(!sa.aad.fs.request))
+ return 0;
+ type = AUDIT_APPARMOR_AUDIT;
+ } else {
+ /* only report permissions that were denied */
+ sa.aad.fs.request = sa.aad.fs.request & ~perms->allow;
+
+ if (sa.aad.fs.request & perms->kill)
+ type = AUDIT_APPARMOR_KILL;
+
+ /* quiet known rejects, assumes quiet and kill do not overlap */
+ if ((sa.aad.fs.request & perms->quiet) &&
+ AUDIT_MODE(profile) != AUDIT_NOQUIET &&
+ AUDIT_MODE(profile) != AUDIT_ALL)
+ sa.aad.fs.request &= ~perms->quiet;
+
+ if (!sa.aad.fs.request)
+ return COMPLAIN_MODE(profile) ? 0 : sa.aad.error;
+ }
+
+ sa.aad.fs.denied = sa.aad.fs.request & ~perms->allow;
+ return aa_audit(type, profile, gfp, &sa, file_audit_cb);
+}
+
+/**
+ * map_old_perms - map old file perms layout to the new layout
+ * @old: permission set in old mapping
+ *
+ * Returns: new permission mapping
+ */
+static u32 map_old_perms(u32 old)
+{
+ u32 new = old & 0xf;
+ if (old & MAY_READ)
+ new |= AA_MAY_META_READ;
+ if (old & MAY_WRITE)
+ new |= AA_MAY_META_WRITE | AA_MAY_CREATE | AA_MAY_DELETE |
+ AA_MAY_CHMOD | AA_MAY_CHOWN;
+ if (old & 0x10)
+ new |= AA_MAY_LINK;
+ /* the old mapping lock and link_subset flags where overlaid
+ * and use was determined by part of a pair that they were in
+ */
+ if (old & 0x20)
+ new |= AA_MAY_LOCK | AA_LINK_SUBSET;
+ if (old & 0x40) /* AA_EXEC_MMAP */
+ new |= AA_EXEC_MMAP;
+
+ new |= AA_MAY_META_READ;
+
+ return new;
+}
+
+/**
+ * compute_perms - convert dfa compressed perms to internal perms
+ * @dfa: dfa to compute perms for (NOT NULL)
+ * @state: state in dfa
+ * @cond: conditions to consider (NOT NULL)
+ *
+ * TODO: convert from dfa + state to permission entry, do computation conversion
+ * at load time.
+ *
+ * Returns: computed permission set
+ */
+static struct file_perms compute_perms(struct aa_dfa *dfa, unsigned int state,
+ struct path_cond *cond)
+{
+ struct file_perms perms;
+
+ /* FIXME: change over to new dfa format
+ * currently file perms are encoded in the dfa, new format
+ * splits the permissions from the dfa. This mapping can be
+ * done at profile load
+ */
+ perms.kill = 0;
+
+ if (current_fsuid() == cond->uid) {
+ perms.allow = map_old_perms(dfa_user_allow(dfa, state));
+ perms.audit = map_old_perms(dfa_user_audit(dfa, state));
+ perms.quiet = map_old_perms(dfa_user_quiet(dfa, state));
+ perms.xindex = dfa_user_xindex(dfa, state);
+ } else {
+ perms.allow = map_old_perms(dfa_other_allow(dfa, state));
+ perms.audit = map_old_perms(dfa_other_audit(dfa, state));
+ perms.quiet = map_old_perms(dfa_other_quiet(dfa, state));
+ perms.xindex = dfa_other_xindex(dfa, state);
+ }
+
+ /* change_profile wasn't determined by ownership in old mapping */
+ if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
+ perms.allow |= AA_MAY_CHANGE_PROFILE;
+
+ return perms;
+}
+
+/**
+ * aa_str_perms - find permission that match @name
+ * @dfa: to match against (MAYBE NULL)
+ * @state: state to start matching in
+ * @name: string to match against dfa (NOT NULL)
+ * @cond: conditions to consider for permission set computation (NOT NULL)
+ * @perms: Returns - the permissions found when matching @name
+ *
+ * Returns: the final state in @dfa when beginning @start and walking @name
+ */
+unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,
+ const char *name, struct path_cond *cond,
+ struct file_perms *perms)
+{
+ unsigned int state;
+ if (!dfa) {
+ *perms = nullperms;
+ return DFA_NOMATCH;
+ }
+
+ state = aa_dfa_match(dfa, start, name);
+ *perms = compute_perms(dfa, state, cond);
+
+ return state;
+}
+
+/**
+ * is_deleted - test if a file has been completely unlinked
+ * @dentry: dentry of file to test for deletion (NOT NULL)
+ *
+ * Returns: %1 if deleted else %0
+ */
+static inline bool is_deleted(struct dentry *dentry)
+{
+ if (d_unlinked(dentry) && dentry->d_inode->i_nlink == 0)
+ return 1;
+ return 0;
+}
+
+/**
+ * aa_path_perm - do permissions check & audit for @path
+ * @op: operation being checked
+ * @profile: profile being enforced (NOT NULL)
+ * @path: path to check permissions of (NOT NULL)
+ * @flags: any additional path flags beyond what the profile specifies
+ * @request: requested permissions
+ * @cond: conditional info for this request (NOT NULL)
+ *
+ * Returns: %0 else error if access denied or other error
+ */
+int aa_path_perm(int op, struct aa_profile *profile, struct path *path,
+ int flags, u32 request, struct path_cond *cond)
+{
+ char *buffer = NULL;
+ struct file_perms perms = {};
+ const char *name, *info = NULL;
+ int error;
+
+ flags |= profile->path_flags | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 0);
+ error = aa_get_name(path, flags, &buffer, &name);
+ if (error) {
+ if (error == -ENOENT && is_deleted(path->dentry)) {
+ /* Access to open files that are deleted are
+ * give a pass (implicit delegation)
+ */
+ error = 0;
+ perms.allow = request;
+ } else if (error == -ENOENT)
+ info = "Failed name lookup - deleted entry";
+ else if (error == -ESTALE)
+ info = "Failed name lookup - disconnected path";
+ else if (error == -ENAMETOOLONG)
+ info = "Failed name lookup - name too long";
+ else
+ info = "Failed name lookup";
+ } else {
+ aa_str_perms(profile->file.dfa, profile->file.start, name, cond,
+ &perms);
+ if (request & ~perms.allow)
+ error = -EACCES;
+ }
+ error = aa_audit_file(profile, &perms, GFP_KERNEL, op, request, name,
+ NULL, cond->uid, info, error);
+ kfree(buffer);
+
+ return error;
+}
+
+/**
+ * xindex_is_subset - helper for aa_path_link
+ * @link: link permission set
+ * @target: target permission set
+ *
+ * test target x permissions are equal OR a subset of link x permissions
+ * this is done as part of the subset test, where a hardlink must have
+ * a subset of permissions that the target has.
+ *
+ * Returns: %1 if subset else %0
+ */
+static inline bool xindex_is_subset(u32 link, u32 target)
+{
+ if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
+ ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
+ return 0;
+
+ return 1;
+}
+
+/**
+ * aa_path_link - Handle hard link permission check
+ * @profile: the profile being enforced (NOT NULL)
+ * @old_dentry: the target dentry (NOT NULL)
+ * @new_dir: directory the new link will be created in (NOT NULL)
+ * @new_dentry: the link being created (NOT NULL)
+ *
+ * Handle the permission test for a link & target pair. Permission
+ * is encoded as a pair where the link permission is determined
+ * first, and if allowed, the target is tested. The target test
+ * is done from the point of the link match (not start of DFA)
+ * making the target permission dependent on the link permission match.
+ *
+ * The subset test if required forces that permissions granted
+ * on link are a subset of the permission granted to target.
+ *
+ * Returns: %0 if allowed else error
+ */
+int aa_path_link(struct aa_profile *profile, struct dentry *old_dentry,
+ struct path *new_dir, struct dentry *new_dentry)
+{
+ struct path link = { new_dir->mnt, new_dentry };
+ struct path target = { new_dir->mnt, old_dentry };
+ struct path_cond cond = {
+ old_dentry->d_inode->i_uid,
+ old_dentry->d_inode->i_mode
+ };
+ char *buffer = NULL, *buffer2 = NULL;
+ const char *lname, *tname = NULL, *info = NULL;
+ struct file_perms lperms, perms;
+ u32 request = AA_MAY_LINK;
+ unsigned int state;
+ int error;
+
+ lperms = nullperms;
+
+ /* buffer freed below, lname is pointer in buffer */
+ error = aa_get_name(&link, profile->path_flags, &buffer, &lname);
+ if (error)
+ goto audit;
+
+ /* buffer2 freed below, tname is pointer in buffer2 */
+ error = aa_get_name(&target, profile->path_flags, &buffer2, &tname);
+ if (error)
+ goto audit;
+
+ error = -EACCES;
+ /* aa_str_perms - handles the case of the dfa being NULL */
+ state = aa_str_perms(profile->file.dfa, profile->file.start, lname,
+ &cond, &lperms);
+
+ if (!(lperms.allow & AA_MAY_LINK))
+ goto audit;
+
+ /* test to see if target can be paired with link */
+ state = aa_dfa_null_transition(profile->file.dfa, state);
+ aa_str_perms(profile->file.dfa, state, tname, &cond, &perms);
+
+ /* force audit/quiet masks for link are stored in the second entry
+ * in the link pair.
+ */
+ lperms.audit = perms.audit;
+ lperms.quiet = perms.quiet;
+ lperms.kill = perms.kill;
+
+ if (!(perms.allow & AA_MAY_LINK)) {
+ info = "target restricted";
+ goto audit;
+ }
+
+ /* done if link subset test is not required */
+ if (!(perms.allow & AA_LINK_SUBSET))
+ goto done_tests;
+
+ /* Do link perm subset test requiring allowed permission on link are a
+ * subset of the allowed permissions on target.
+ */
+ aa_str_perms(profile->file.dfa, profile->file.start, tname, &cond,
+ &perms);
+
+ /* AA_MAY_LINK is not considered in the subset test */
+ request = lperms.allow & ~AA_MAY_LINK;
+ lperms.allow &= perms.allow | AA_MAY_LINK;
+
+ request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
+ if (request & ~lperms.allow) {
+ goto audit;
+ } else if ((lperms.allow & MAY_EXEC) &&
+ !xindex_is_subset(lperms.xindex, perms.xindex)) {
+ lperms.allow &= ~MAY_EXEC;
+ request |= MAY_EXEC;
+ info = "link not subset of target";
+ goto audit;
+ }
+
+done_tests:
+ error = 0;
+
+audit:
+ error = aa_audit_file(profile, &lperms, GFP_KERNEL, OP_LINK, request,
+ lname, tname, cond.uid, info, error);
+ kfree(buffer);
+ kfree(buffer2);
+
+ return error;
+}
+
+/**
+ * aa_file_perm - do permission revalidation check & audit for @file
+ * @op: operation being checked
+ * @profile: profile being enforced (NOT NULL)
+ * @file: file to revalidate access permissions on (NOT NULL)
+ * @request: requested permissions
+ *
+ * Returns: %0 if access allowed else error
+ */
+int aa_file_perm(int op, struct aa_profile *profile, struct file *file,
+ u32 request)
+{
+ struct path_cond cond = {
+ .uid = file->f_path.dentry->d_inode->i_uid,
+ .mode = file->f_path.dentry->d_inode->i_mode
+ };
+
+ return aa_path_perm(op, profile, &file->f_path, PATH_DELEGATE_DELETED,
+ request, &cond);
+}
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2024-12-03 21:59:31 +0000