#include "linux/capability.h" #include "linux/cred.h" #include "linux/dcache.h" #include "linux/err.h" #include "linux/init.h" #include "linux/init_task.h" #include "linux/irqflags.h" #include "linux/kallsyms.h" #include "linux/kernel.h" #include "linux/kprobes.h" #include "linux/list.h" #include "linux/lsm_hooks.h" #include "linux/mm.h" #include "linux/mm_types.h" #include "linux/nsproxy.h" #include "linux/path.h" #include "linux/printk.h" #include "linux/sched.h" #include "linux/security.h" #include "linux/stddef.h" #include "linux/types.h" #include "linux/uaccess.h" #include "linux/uidgid.h" #include "linux/version.h" #include "linux/mount.h" #include "linux/fs.h" #include "linux/namei.h" #include "linux/rcupdate.h" #include "allowlist.h" #include "arch.h" #include "core_hook.h" #include "klog.h" // IWYU pragma: keep #include "ksu.h" #include "ksud.h" #include "linux/vmalloc.h" #include "manager.h" #include "selinux/selinux.h" #include "uid_observer.h" #include "kernel_compat.h" static bool ksu_module_mounted = false; extern int handle_sepolicy(unsigned long arg3, void __user *arg4); static inline bool is_allow_su() { if (is_manager()) { // we are manager, allow! return true; } return ksu_is_allow_uid(current_uid().val); } static inline bool is_unsupported_uid(uid_t uid) { #define LAST_APPLICATION_UID 19999 uid_t appid = uid % 100000; return appid > LAST_APPLICATION_UID; } static struct group_info root_groups = { .usage = ATOMIC_INIT(2) }; static void setup_groups(struct root_profile *profile, struct cred *cred) { if (profile->groups_count > KSU_MAX_GROUPS) { pr_warn("Failed to setgroups, too large group: %d!\n", profile->uid); return; } if (profile->groups_count == 1 && profile->groups[0] == 0) { // setgroup to root and return early. if (cred->group_info) put_group_info(cred->group_info); cred->group_info = get_group_info(&root_groups); return; } u32 ngroups = profile->groups_count; struct group_info *group_info = groups_alloc(ngroups); if (!group_info) { pr_warn("Failed to setgroups, ENOMEM for: %d\n", profile->uid); return; } int i; for (i = 0; i < ngroups; i++) { gid_t gid = profile->groups[i]; kgid_t kgid = make_kgid(current_user_ns(), gid); if (!gid_valid(kgid)) { pr_warn("Failed to setgroups, invalid gid: %d\n", gid); put_group_info(group_info); return; } #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 9, 0) group_info->gid[i] = kgid; #else GROUP_AT(group_info, i) = kgid; #endif } groups_sort(group_info); set_groups(cred, group_info); } void escape_to_root(void) { struct cred *cred; cred = (struct cred *)__task_cred(current); if (cred->euid.val == 0) { pr_warn("Already root, don't escape!\n"); return; } struct root_profile *profile = ksu_get_root_profile(cred->uid.val); cred->uid.val = profile->uid; cred->suid.val = profile->uid; cred->euid.val = profile->uid; cred->fsuid.val = profile->uid; cred->gid.val = profile->gid; cred->fsgid.val = profile->gid; cred->sgid.val = profile->gid; cred->egid.val = profile->gid; BUILD_BUG_ON(sizeof(profile->capabilities.effective) != sizeof(kernel_cap_t)); // setup capabilities // we need CAP_DAC_READ_SEARCH becuase `/data/adb/ksud` is not accessible for non root process // we add it here but don't add it to cap_inhertiable, it would be dropped automaticly after exec! u64 cap_for_ksud = profile->capabilities.effective | CAP_DAC_READ_SEARCH; memcpy(&cred->cap_effective, &cap_for_ksud, sizeof(cred->cap_effective)); memcpy(&cred->cap_inheritable, &profile->capabilities.effective, sizeof(cred->cap_inheritable)); memcpy(&cred->cap_permitted, &profile->capabilities.effective, sizeof(cred->cap_permitted)); memcpy(&cred->cap_bset, &profile->capabilities.effective, sizeof(cred->cap_bset)); memcpy(&cred->cap_ambient, &profile->capabilities.effective, sizeof(cred->cap_ambient)); // disable seccomp #if defined(CONFIG_GENERIC_ENTRY) && \ LINUX_VERSION_CODE >= KERNEL_VERSION(5, 11, 0) current_thread_info()->syscall_work &= ~SYSCALL_WORK_SECCOMP; #else current_thread_info()->flags &= ~(TIF_SECCOMP | _TIF_SECCOMP); #endif #ifdef CONFIG_SECCOMP current->seccomp.mode = 0; current->seccomp.filter = NULL; #else #endif setup_groups(profile, cred); setup_selinux(profile->selinux_domain); } int ksu_handle_rename(struct dentry *old_dentry, struct dentry *new_dentry) { if (!current->mm) { // skip kernel threads return 0; } if (current_uid().val != 1000) { // skip non system uid return 0; } if (!old_dentry || !new_dentry) { return 0; } // /data/system/packages.list.tmp -> /data/system/packages.list if (strcmp(new_dentry->d_iname, "packages.list")) { return 0; } char path[128]; char *buf = dentry_path_raw(new_dentry, path, sizeof(path)); if (IS_ERR(buf)) { pr_err("dentry_path_raw failed.\n"); return 0; } if (strcmp(buf, "/system/packages.list")) { return 0; } pr_info("renameat: %s -> %s, new path: %s\n", old_dentry->d_iname, new_dentry->d_iname, buf); update_uid(); return 0; } int ksu_handle_prctl(int option, unsigned long arg2, unsigned long arg3, unsigned long arg4, unsigned long arg5) { // if success, we modify the arg5 as result! u32 *result = (u32 *)arg5; u32 reply_ok = KERNEL_SU_OPTION; if (KERNEL_SU_OPTION != option) { return 0; } bool from_root = 0 == current_uid().val; bool from_manager = is_manager(); if (!from_root && !from_manager) { // only root or manager can access this interface return 0; } #ifdef CONFIG_KSU_DEBUG pr_info("option: 0x%x, cmd: %ld\n", option, arg2); #endif if (arg2 == CMD_BECOME_MANAGER) { if (from_manager) { if (copy_to_user(result, &reply_ok, sizeof(reply_ok))) { pr_err("become_manager: prctl reply error\n"); } return 0; } return 0; } if (arg2 == CMD_GRANT_ROOT) { if (is_allow_su()) { pr_info("allow root for: %d\n", current_uid().val); escape_to_root(); if (copy_to_user(result, &reply_ok, sizeof(reply_ok))) { pr_err("grant_root: prctl reply error\n"); } } return 0; } // Both root manager and root processes should be allowed to get version if (arg2 == CMD_GET_VERSION) { u32 version = KERNEL_SU_VERSION; if (copy_to_user(arg3, &version, sizeof(version))) { pr_err("prctl reply error, cmd: %lu\n", arg2); } #ifdef MODULE u32 is_lkm = 0x1; #else u32 is_lkm = 0x0; #endif if (arg4 && copy_to_user(arg4, &is_lkm, sizeof(is_lkm))) { pr_err("prctl reply error, cmd: %lu\n", arg2); } return 0; } if (arg2 == CMD_REPORT_EVENT) { if (!from_root) { return 0; } switch (arg3) { case EVENT_POST_FS_DATA: { static bool post_fs_data_lock = false; if (!post_fs_data_lock) { post_fs_data_lock = true; pr_info("post-fs-data triggered\n"); on_post_fs_data(); } break; } case EVENT_BOOT_COMPLETED: { static bool boot_complete_lock = false; if (!boot_complete_lock) { boot_complete_lock = true; pr_info("boot_complete triggered\n"); } break; } case EVENT_MODULE_MOUNTED: { ksu_module_mounted = true; pr_info("module mounted!\n"); break; } default: break; } return 0; } if (arg2 == CMD_SET_SEPOLICY) { if (!from_root) { return 0; } if (!handle_sepolicy(arg3, arg4)) { if (copy_to_user(result, &reply_ok, sizeof(reply_ok))) { pr_err("sepolicy: prctl reply error\n"); } } return 0; } if (arg2 == CMD_CHECK_SAFEMODE) { if (ksu_is_safe_mode()) { pr_warn("safemode enabled!\n"); if (copy_to_user(result, &reply_ok, sizeof(reply_ok))) { pr_err("safemode: prctl reply error\n"); } } return 0; } if (arg2 == CMD_GET_ALLOW_LIST || arg2 == CMD_GET_DENY_LIST) { u32 array[128]; u32 array_length; bool success = ksu_get_allow_list(array, &array_length, arg2 == CMD_GET_ALLOW_LIST); if (success) { if (!copy_to_user(arg4, &array_length, sizeof(array_length)) && !copy_to_user(arg3, array, sizeof(u32) * array_length)) { if (copy_to_user(result, &reply_ok, sizeof(reply_ok))) { pr_err("prctl reply error, cmd: %lu\n", arg2); } } else { pr_err("prctl copy allowlist error\n"); } } return 0; } if (arg2 == CMD_UID_GRANTED_ROOT || arg2 == CMD_UID_SHOULD_UMOUNT) { uid_t target_uid = (uid_t)arg3; bool allow = false; if (arg2 == CMD_UID_GRANTED_ROOT) { allow = ksu_is_allow_uid(target_uid); } else if (arg2 == CMD_UID_SHOULD_UMOUNT) { allow = ksu_uid_should_umount(target_uid); } else { pr_err("unknown cmd: %lu\n", arg2); } if (!copy_to_user(arg4, &allow, sizeof(allow))) { if (copy_to_user(result, &reply_ok, sizeof(reply_ok))) { pr_err("prctl reply error, cmd: %lu\n", arg2); } } else { pr_err("prctl copy err, cmd: %lu\n", arg2); } return 0; } // all other cmds are for 'root manager' if (!from_manager) { return 0; } // we are already manager if (arg2 == CMD_GET_APP_PROFILE) { struct app_profile profile; if (copy_from_user(&profile, arg3, sizeof(profile))) { pr_err("copy profile failed\n"); return 0; } bool success = ksu_get_app_profile(&profile); if (success) { if (copy_to_user(arg3, &profile, sizeof(profile))) { pr_err("copy profile failed\n"); return 0; } if (copy_to_user(result, &reply_ok, sizeof(reply_ok))) { pr_err("prctl reply error, cmd: %lu\n", arg2); } } return 0; } if (arg2 == CMD_SET_APP_PROFILE) { struct app_profile profile; if (copy_from_user(&profile, arg3, sizeof(profile))) { pr_err("copy profile failed\n"); return 0; } // todo: validate the params if (ksu_set_app_profile(&profile, true)) { if (copy_to_user(result, &reply_ok, sizeof(reply_ok))) { pr_err("prctl reply error, cmd: %lu\n", arg2); } } return 0; } return 0; } static bool is_appuid(kuid_t uid) { #define PER_USER_RANGE 100000 #define FIRST_APPLICATION_UID 10000 #define LAST_APPLICATION_UID 19999 uid_t appid = uid.val % PER_USER_RANGE; return appid >= FIRST_APPLICATION_UID && appid <= LAST_APPLICATION_UID; } static bool should_umount(struct path *path) { if (!path) { return false; } if (current->nsproxy->mnt_ns == init_nsproxy.mnt_ns) { pr_info("ignore global mnt namespace process: %d\n", current_uid().val); return false; } if (path->mnt && path->mnt->mnt_sb && path->mnt->mnt_sb->s_type) { const char *fstype = path->mnt->mnt_sb->s_type->name; return strcmp(fstype, "overlay") == 0; } return false; } static void ksu_umount_mnt(struct path *path, int flags) { #if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 9, 0) || defined(KSU_UMOUNT) int err = path_umount(path, flags); if (err) { pr_info("umount %s failed: %d\n", path->dentry->d_iname, err); } #else // TODO: umount for non GKI kernel #endif } static void try_umount(const char *mnt, bool check_mnt, int flags) { struct path path; int err = kern_path(mnt, 0, &path); if (err) { return; } if (path.dentry != path.mnt->mnt_root) { // it is not root mountpoint, maybe umounted by others already. return; } // we are only interest in some specific mounts if (check_mnt && !should_umount(&path)) { return; } ksu_umount_mnt(&path, flags); } int ksu_handle_setuid(struct cred *new, const struct cred *old) { // this hook is used for umounting overlayfs for some uid, if there isn't any module mounted, just ignore it! if (!ksu_module_mounted) { return 0; } if (!new || !old) { return 0; } kuid_t new_uid = new->uid; kuid_t old_uid = old->uid; if (0 != old_uid.val) { // old process is not root, ignore it. return 0; } if (!is_appuid(new_uid) || is_unsupported_uid(new_uid.val)) { // pr_info("handle setuid ignore non application or isolated uid: %d\n", new_uid.val); return 0; } if (ksu_is_allow_uid(new_uid.val)) { // pr_info("handle setuid ignore allowed application: %d\n", new_uid.val); return 0; } if (!ksu_uid_should_umount(new_uid.val)) { return 0; } else { #ifdef CONFIG_KSU_DEBUG pr_info("uid: %d should not umount!\n", current_uid().val); #endif } // check old process's selinux context, if it is not zygote, ignore it! // because some su apps may setuid to untrusted_app but they are in global mount namespace // when we umount for such process, that is a disaster! bool is_zygote_child = is_zygote(old->security); if (!is_zygote_child) { pr_info("handle umount ignore non zygote child: %d\n", current->pid); return 0; } // umount the target mnt pr_info("handle umount for uid: %d, pid: %d\n", new_uid.val, current->pid); // fixme: use `collect_mounts` and `iterate_mount` to iterate all mountpoint and // filter the mountpoint whose target is `/data/adb` try_umount("/system", true, 0); try_umount("/vendor", true, 0); try_umount("/product", true, 0); try_umount("/data/adb/modules", false, MNT_DETACH); // try umount ksu temp path try_umount("/debug_ramdisk", false, MNT_DETACH); try_umount("/sbin", false, MNT_DETACH); return 0; } // Init functons static int handler_pre(struct kprobe *p, struct pt_regs *regs) { #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 16, 0) struct pt_regs *real_regs = (struct pt_regs *)PT_REGS_PARM1(regs); #else struct pt_regs *real_regs = regs; #endif int option = (int)PT_REGS_PARM1(real_regs); unsigned long arg2 = (unsigned long)PT_REGS_PARM2(real_regs); unsigned long arg3 = (unsigned long)PT_REGS_PARM3(real_regs); #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 16, 0) // PRCTL_SYMBOL is the arch-specificed one, which receive raw pt_regs from syscall unsigned long arg4 = (unsigned long)PT_REGS_SYSCALL_PARM4(real_regs); #else // PRCTL_SYMBOL is the common one, called by C convention in do_syscall_64 // https://elixir.bootlin.com/linux/v4.15.18/source/arch/x86/entry/common.c#L287 unsigned long arg4 = (unsigned long)PT_REGS_CCALL_PARM4(real_regs); #endif unsigned long arg5 = (unsigned long)PT_REGS_PARM5(real_regs); return ksu_handle_prctl(option, arg2, arg3, arg4, arg5); } static struct kprobe prctl_kp = { .symbol_name = PRCTL_SYMBOL, .pre_handler = handler_pre, }; static int renameat_handler_pre(struct kprobe *p, struct pt_regs *regs) { #if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0) // https://elixir.bootlin.com/linux/v5.12-rc1/source/include/linux/fs.h struct renamedata *rd = PT_REGS_PARM1(regs); struct dentry *old_entry = rd->old_dentry; struct dentry *new_entry = rd->new_dentry; #else struct dentry *old_entry = (struct dentry *)PT_REGS_PARM2(regs); struct dentry *new_entry = (struct dentry *)PT_REGS_CCALL_PARM4(regs); #endif return ksu_handle_rename(old_entry, new_entry); } static struct kprobe renameat_kp = { .symbol_name = "vfs_rename", .pre_handler = renameat_handler_pre, }; __maybe_unused int ksu_kprobe_init(void) { int rc = 0; rc = register_kprobe(&prctl_kp); if (rc) { pr_info("prctl kprobe failed: %d.\n", rc); return rc; } rc = register_kprobe(&renameat_kp); pr_info("renameat kp: %d\n", rc); return rc; } __maybe_unused int ksu_kprobe_exit(void) { unregister_kprobe(&prctl_kp); unregister_kprobe(&renameat_kp); return 0; } static int ksu_task_prctl(int option, unsigned long arg2, unsigned long arg3, unsigned long arg4, unsigned long arg5) { ksu_handle_prctl(option, arg2, arg3, arg4, arg5); return -ENOSYS; } // kernel 4.4 and 4.9 #if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0) static int ksu_key_permission(key_ref_t key_ref, const struct cred *cred, unsigned perm) { if (init_session_keyring != NULL) { return 0; } if (strcmp(current->comm, "init")) { // we are only interested in `init` process return 0; } init_session_keyring = cred->session_keyring; pr_info("kernel_compat: got init_session_keyring\n"); return 0; } #endif static int ksu_inode_rename(struct inode *old_inode, struct dentry *old_dentry, struct inode *new_inode, struct dentry *new_dentry) { return ksu_handle_rename(old_dentry, new_dentry); } static int ksu_task_fix_setuid(struct cred *new, const struct cred *old, int flags) { return ksu_handle_setuid(new, old); } #ifndef MODULE static struct security_hook_list ksu_hooks[] = { LSM_HOOK_INIT(task_prctl, ksu_task_prctl), LSM_HOOK_INIT(inode_rename, ksu_inode_rename), LSM_HOOK_INIT(task_fix_setuid, ksu_task_fix_setuid), #if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0) LSM_HOOK_INIT(key_permission, ksu_key_permission) #endif }; void __init ksu_lsm_hook_init(void) { #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 11, 0) security_add_hooks(ksu_hooks, ARRAY_SIZE(ksu_hooks), "ksu"); #else // https://elixir.bootlin.com/linux/v4.10.17/source/include/linux/lsm_hooks.h#L1892 security_add_hooks(ksu_hooks, ARRAY_SIZE(ksu_hooks)); #endif } #else static int override_security_head(void *head, const void *new_head, size_t len) { unsigned long base = (unsigned long)head & PAGE_MASK; unsigned long offset = offset_in_page(head); // this is impossible for our case because the page alignment // but be careful for other cases! BUG_ON(offset + len > PAGE_SIZE); struct page *page = phys_to_page(__pa(base)); if (!page) { return -EFAULT; } void *addr = vmap(&page, 1, VM_MAP, PAGE_KERNEL); if (!addr) { return -ENOMEM; } local_irq_disable(); memcpy(addr + offset, new_head, len); local_irq_enable(); vunmap(addr); return 0; } static void free_security_hook_list(struct hlist_head *head) { struct hlist_node *temp; struct security_hook_list *entry; if (!head) return; hlist_for_each_entry_safe (entry, temp, head, list) { hlist_del(&entry->list); kfree(entry); } kfree(head); } struct hlist_head *copy_security_hlist(struct hlist_head *orig) { struct hlist_head *new_head = kmalloc(sizeof(*new_head), GFP_KERNEL); if (!new_head) return NULL; INIT_HLIST_HEAD(new_head); struct security_hook_list *entry; struct security_hook_list *new_entry; hlist_for_each_entry (entry, orig, list) { new_entry = kmalloc(sizeof(*new_entry), GFP_KERNEL); if (!new_entry) { free_security_hook_list(new_head); return NULL; } *new_entry = *entry; hlist_add_tail_rcu(&new_entry->list, new_head); } return new_head; } #define LSM_SEARCH_MAX 180 // This should be enough to iterate static void *find_head_addr(void *security_ptr, int *index) { if (!security_ptr) { return NULL; } struct hlist_head *head_start = (struct hlist_head *)&security_hook_heads; for (int i = 0; i < LSM_SEARCH_MAX; i++) { struct hlist_head *head = head_start + i; struct security_hook_list *pos; hlist_for_each_entry (pos, head, list) { if (pos->hook.capget == security_ptr) { if (index) { *index = i; } return head; } } } return NULL; } #define GET_SYMBOL_ADDR(sym) \ ({ \ void *addr = kallsyms_lookup_name(#sym ".cfi_jt"); \ if (!addr) { \ addr = kallsyms_lookup_name(#sym); \ } \ addr; \ }) #define KSU_LSM_HOOK_HACK_INIT(head_ptr, name, func) \ do { \ static struct security_hook_list hook = { \ .hook = { .name = func } \ }; \ hook.head = head_ptr; \ hook.lsm = "ksu"; \ struct hlist_head *new_head = copy_security_hlist(hook.head); \ if (!new_head) { \ pr_err("Failed to copy security list: %s\n", #name); \ break; \ } \ hlist_add_tail_rcu(&hook.list, new_head); \ if (override_security_head(hook.head, new_head, \ sizeof(*new_head))) { \ free_security_hook_list(new_head); \ pr_err("Failed to hack lsm for: %s\n", #name); \ } \ } while (0) void __init ksu_lsm_hook_init(void) { void *cap_prctl = GET_SYMBOL_ADDR(cap_task_prctl); void *prctl_head = find_head_addr(cap_prctl, NULL); if (prctl_head) { if (prctl_head != &security_hook_heads.task_prctl) { pr_warn("prctl's address has shifted!\n"); } KSU_LSM_HOOK_HACK_INIT(prctl_head, task_prctl, ksu_task_prctl); } else { pr_warn("Failed to find task_prctl!\n"); } int inode_killpriv_index = -1; void *cap_killpriv = GET_SYMBOL_ADDR(cap_inode_killpriv); find_head_addr(cap_killpriv, &inode_killpriv_index); if (inode_killpriv_index < 0) { pr_warn("Failed to find inode_rename, use kprobe instead!\n"); register_kprobe(&renameat_kp); } else { int inode_rename_index = inode_killpriv_index + &security_hook_heads.inode_rename - &security_hook_heads.inode_killpriv; struct hlist_head *head_start = (struct hlist_head *)&security_hook_heads; void *inode_rename_head = head_start + inode_rename_index; if (inode_rename_head != &security_hook_heads.inode_rename) { pr_warn("inode_rename's address has shifted!\n"); } KSU_LSM_HOOK_HACK_INIT(inode_rename_head, inode_rename, ksu_inode_rename); } void *cap_setuid = GET_SYMBOL_ADDR(cap_task_fix_setuid); void *setuid_head = find_head_addr(cap_setuid, NULL); if (setuid_head) { if (setuid_head != &security_hook_heads.task_fix_setuid) { pr_warn("setuid's address has shifted!\n"); } KSU_LSM_HOOK_HACK_INIT(setuid_head, task_fix_setuid, ksu_task_fix_setuid); } else { pr_warn("Failed to find task_fix_setuid!\n"); } smp_mb(); } #endif void __init ksu_core_init(void) { ksu_lsm_hook_init(); } void ksu_core_exit(void) { pr_info("ksu_kprobe_exit\n"); }