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Hook syscalls and stable symbols #1657

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merged 7 commits into from
Apr 26, 2024
Merged

Hook syscalls and stable symbols #1657

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b3536f8
Hook syscalls and stable symbols
anotherjin Apr 23, 2024
7df8ab3
Fix Whitespace
anotherjin Apr 23, 2024
fb5cdac
Remove unused hooks
anotherjin Apr 24, 2024
6e5c8fb
Fix unregister input_event_kps
anotherjin Apr 24, 2024
f2153d6
Remove __getname use
anotherjin Apr 24, 2024
3edeaf9
Remove duplicated logic in ksud
anotherjin Apr 25, 2024
14def44
Fix x86_64 and remove unused symbols
anotherjin Apr 25, 2024
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8 changes: 8 additions & 0 deletions kernel/arch.h
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Original file line number Diff line number Diff line change
Expand Up @@ -23,11 +23,19 @@
#define SYS_READ_SYMBOL "__arm64_sys_read"
#define SYS_NEWFSTATAT_SYMBOL "__arm64_sys_newfstatat"
#define SYS_FACCESSAT_SYMBOL "__arm64_sys_faccessat"
#define SYS_EXECVE_SYMBOL "__arm64_sys_execve"
#define SYS_EXECVEAT_SYMBOL "__arm64_sys_execveat"
#define COMPAT_SYS_EXECVE_SYMBOL "__arm64_compat_sys_execve"
#define COMPAT_SYS_EXECVEAT_SYMBOL "__arm64_compat_sys_execveat"
#else
#define PRCTL_SYMBOL "sys_prctl"
#define SYS_READ_SYMBOL "sys_read"
#define SYS_NEWFSTATAT_SYMBOL "sys_newfstatat"
#define SYS_FACCESSAT_SYMBOL "sys_faccessat"
#define SYS_EXECVE_SYMBOL "sys_execve"
#define SYS_EXECVEAT_SYMBOL "sys_execveat"
#define COMPAT_SYS_EXECVE_SYMBOL "compat_sys_execve"
#define COMPAT_SYS_EXECVEAT_SYMBOL "compat_sys_execveat"
#endif

#elif defined(__x86_64__)
Expand Down
157 changes: 151 additions & 6 deletions kernel/ksud.c
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Original file line number Diff line number Diff line change
Expand Up @@ -176,7 +176,7 @@ int ksu_handle_execveat_ksud(int *fd, struct filename **filename_ptr,
return 0;
}

if (unlikely(!memcmp(filename->name, system_bin_init,
if (unlikely(!memcmp(filename->name, system_bin_init,
sizeof(system_bin_init) - 1) && argv)) {
// /system/bin/init executed
int argc = count(*argv, MAX_ARG_STRINGS);
Expand Down Expand Up @@ -263,6 +263,119 @@ int ksu_handle_execveat_ksud(int *fd, struct filename **filename_ptr,
return 0;
}

int ksu_handle_execve_ksud(int *fd, const char **filename_ptr,
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struct user_arg_ptr *argv, struct user_arg_ptr *envp, int *flags)
{
static const char app_process[] = "/system/bin/app_process";
static bool first_app_process = true;

/* This applies to versions Android 10+ */
static const char system_bin_init[] = "/system/bin/init";
/* This applies to versions between Android 6 ~ 9 */
static const char old_system_init[] = "/init";
static bool init_second_stage_executed = false;

char filename[sizeof(app_process) + 1];

#ifndef CONFIG_KPROBES
if (!ksu_execveat_hook) {
return 0;
}
#endif

if (!filename_ptr)
return 0;

memset(filename, 0, sizeof(filename));
ksu_strncpy_from_user_nofault(filename, *filename_ptr, sizeof(filename));

if (unlikely(!memcmp(filename, system_bin_init,
sizeof(system_bin_init) - 1) && argv)) {
// /system/bin/init executed
int argc = count(*argv, MAX_ARG_STRINGS);
pr_info("/system/bin/init argc: %d\n", argc);
if (argc > 1 && !init_second_stage_executed) {
const char __user *p = get_user_arg_ptr(*argv, 1);
if (p && !IS_ERR(p)) {
char first_arg[16];
ksu_strncpy_from_user_nofault(first_arg, p, sizeof(first_arg));
pr_info("/system/bin/init first arg: %s\n", first_arg);
if (!strcmp(first_arg, "second_stage")) {
pr_info("/system/bin/init second_stage executed\n");
apply_kernelsu_rules();
init_second_stage_executed = true;
ksu_android_ns_fs_check();
}
} else {
pr_err("/system/bin/init parse args err!\n");
}
}
} else if (unlikely(!memcmp(filename, old_system_init,
sizeof(old_system_init) - 1) && argv)) {
// /init executed
int argc = count(*argv, MAX_ARG_STRINGS);
pr_info("/init argc: %d\n", argc);
if (argc > 1 && !init_second_stage_executed) {
/* This applies to versions between Android 6 ~ 7 */
const char __user *p = get_user_arg_ptr(*argv, 1);
if (p && !IS_ERR(p)) {
char first_arg[16];
ksu_strncpy_from_user_nofault(first_arg, p, sizeof(first_arg));
pr_info("/init first arg: %s\n", first_arg);
if (!strcmp(first_arg, "--second-stage")) {
pr_info("/init second_stage executed\n");
apply_kernelsu_rules();
init_second_stage_executed = true;
ksu_android_ns_fs_check();
}
} else {
pr_err("/init parse args err!\n");
}
} else if (argc == 1 && !init_second_stage_executed && envp) {
/* This applies to versions between Android 8 ~ 9 */
int envc = count(*envp, MAX_ARG_STRINGS);
if (envc > 0) {
int n;
for (n = 1; n <= envc; n++) {
const char __user *p = get_user_arg_ptr(*envp, n);
if (!p || IS_ERR(p)) {
continue;
}
char env[256];
// Reading environment variable strings from user space
if (ksu_strncpy_from_user_nofault(env, p, sizeof(env)) < 0)
continue;
// Parsing environment variable names and values
char *env_name = env;
char *env_value = strchr(env, '=');
if (env_value == NULL)
continue;
// Replace equal sign with string terminator
*env_value = '\0';
env_value++;
// Check if the environment variable name and value are matching
if (!strcmp(env_name, "INIT_SECOND_STAGE") && (!strcmp(env_value, "1") || !strcmp(env_value, "true"))) {
pr_info("/init second_stage executed\n");
apply_kernelsu_rules();
init_second_stage_executed = true;
ksu_android_ns_fs_check();
}
}
}
}
}

if (unlikely(first_app_process &&
!memcmp(filename, app_process, sizeof(app_process) - 1))) {
first_app_process = false;
pr_info("exec app_process, /data prepared, second_stage: %d\n", init_second_stage_executed);
on_post_fs_data(); // we keep this for old ksud
stop_execve_hook();
}

return 0;
}

static ssize_t (*orig_read)(struct file *, char __user *, size_t, loff_t *);
static ssize_t (*orig_read_iter)(struct kiocb *, struct iov_iter *);
static struct file_operations fops_proxy;
Expand Down Expand Up @@ -472,6 +585,22 @@ static int execve_handler_pre(struct kprobe *p, struct pt_regs *regs)
return ksu_handle_execveat_ksud(fd, filename_ptr, &argv, NULL, NULL);
}

static int sys_execve_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
const char __user **filename_user = (const char **)&PT_REGS_PARM1(real_regs);
const char __user *const __user *__argv =
(const char __user *const __user *)PT_REGS_PARM2(real_regs);
struct user_arg_ptr argv = { .ptr.native = __argv };

return ksu_handle_execve_ksud(AT_FDCWD, filename_user, &argv, NULL,
NULL);
}

// remove this later!
__maybe_unused static int vfs_read_handler_pre(struct kprobe *p, struct pt_regs *regs)
{
Expand Down Expand Up @@ -506,6 +635,12 @@ static int input_handle_event_handler_pre(struct kprobe *p,
return ksu_handle_input_handle_event(type, code, value);
}

#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 10, 0)
static struct kprobe execve_kp = {
.symbol_name = SYS_EXECVE_SYMBOL,
.pre_handler = sys_execve_handler_pre,
};
#else
static struct kprobe execve_kp = {
#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 9, 0)
.symbol_name = "do_execveat_common",
Expand All @@ -516,6 +651,7 @@ static struct kprobe execve_kp = {
#endif
.pre_handler = execve_handler_pre,
};
#endif

#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 10, 0)
static struct kprobe vfs_read_kp = {
Expand All @@ -529,11 +665,20 @@ static struct kprobe vfs_read_kp = {
};
#endif

static struct kprobe input_handle_event_kp = {
.symbol_name = "input_handle_event",
static struct kprobe input_event_kp = {
.symbol_name = "input_event",
.pre_handler = input_handle_event_handler_pre,
};

static struct kprobe input_inject_event_kp = {
.symbol_name = "input_inject_event",
.pre_handler = input_handle_event_handler_pre,
};

static struct kprobe *input_event_kps[] = {
&input_event_kp, &input_inject_event_kp
};

static void do_stop_vfs_read_hook(struct work_struct *work)
{
unregister_kprobe(&vfs_read_kp);
Expand All @@ -546,7 +691,7 @@ static void do_stop_execve_hook(struct work_struct *work)

static void do_stop_input_hook(struct work_struct *work)
{
unregister_kprobe(&input_handle_event_kp);
unregister_kprobes(input_event_kps, 2);
}
#endif

Expand Down Expand Up @@ -600,7 +745,7 @@ void ksu_ksud_init()
ret = register_kprobe(&vfs_read_kp);
pr_info("ksud: vfs_read_kp: %d\n", ret);

ret = register_kprobe(&input_handle_event_kp);
ret = register_kprobes(input_event_kps, 2);
pr_info("ksud: input_handle_event_kp: %d\n", ret);

INIT_WORK(&stop_vfs_read_work, do_stop_vfs_read_hook);
Expand All @@ -614,6 +759,6 @@ void ksu_ksud_exit() {
unregister_kprobe(&execve_kp);
// this should be done before unregister vfs_read_kp
// unregister_kprobe(&vfs_read_kp);
unregister_kprobe(&input_handle_event_kp);
unregister_kprobes(input_event_kps, 2);
#endif
}
52 changes: 52 additions & 0 deletions kernel/sucompat.c
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,13 @@ static char __user *sh_user_path(void)
return userspace_stack_buffer(sh_path, sizeof(sh_path));
}

static char __user *ksud_user_path(void)
{
static const char ksud_path[] = KSUD_PATH;

return userspace_stack_buffer(ksud_path, sizeof(ksud_path));
}

int ksu_handle_faccessat(int *dfd, const char __user **filename_user, int *mode,
int * __unused_flags)
{
Expand Down Expand Up @@ -130,6 +137,32 @@ int ksu_handle_execveat_sucompat(int *fd, struct filename **filename_ptr,
return 0;
}

int ksu_handle_execve_sucompat(int *fd, const char __user **filename_user,
void *__never_use_argv, void *__never_use_envp, int *__never_use_flags)
{
const char su[] = SU_PATH;
char path[sizeof(su) + 1];

if (unlikely(!filename_user))
return 0;

memset(path, 0, sizeof(path));
ksu_strncpy_from_user_nofault(path, *filename_user, sizeof(path));

if (likely(memcmp(path, su, sizeof(su))))
return 0;

if (!ksu_is_allow_uid(current_uid().val))
return 0;

pr_info("sys_execve su found\n");
*filename_user = ksud_user_path();

escape_to_root();

return 0;
}

#ifdef CONFIG_KPROBES

__maybe_unused static int faccessat_handler_pre(struct kprobe *p, struct pt_regs *regs)
Expand Down Expand Up @@ -196,6 +229,18 @@ static int execve_handler_pre(struct kprobe *p, struct pt_regs *regs)
return ksu_handle_execveat_sucompat(fd, filename_ptr, NULL, NULL, NULL);
}

static int sys_execve_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
const char __user **filename_user = (const char **)&PT_REGS_PARM1(real_regs);

return ksu_handle_execve_sucompat(AT_FDCWD, filename_user, NULL, NULL, NULL);
}

#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 10, 0)
static struct kprobe faccessat_kp = {
.symbol_name = SYS_FACCESSAT_SYMBOL,
Expand Down Expand Up @@ -228,6 +273,12 @@ static struct kprobe newfstatat_kp = {
};
#endif

#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 10, 0)
static struct kprobe execve_kp = {
.symbol_name = SYS_EXECVE_SYMBOL,
.pre_handler = sys_execve_handler_pre,
};
#else
static struct kprobe execve_kp = {
#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 9, 0)
.symbol_name = "do_execveat_common",
Expand All @@ -238,6 +289,7 @@ static struct kprobe execve_kp = {
#endif
.pre_handler = execve_handler_pre,
};
#endif

#endif

Expand Down