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Use isolated devpts if kernel support

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kernel version >= 4.7 or CONFIG_DEVPTS_MULTIPLE_INSTANCES=y
This commit is contained in:
vvb2060 2021-07-22 23:35:14 +08:00 committed by John Wu
parent 0dad06cdfe
commit f324252681
8 changed files with 63 additions and 33 deletions
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13
native/jni/core/daemon.cpp
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@ -249,6 +249,19 @@ static int switch_cgroup(const char *cgroup, int pid) {
return true;
});
// Use isolated devpts if kernel support
if (access("/dev/pts/ptmx", F_OK) == 0) {
auto pts = MAGISKTMP + "/" SHELLPTS;
xmkdirs(pts.data(), 0755);
xmount("devpts", pts.data(), "devpts",
MS_NOSUID | MS_NOEXEC, "newinstance");
auto ptmx = pts + "/ptmx";
if (access(ptmx.data(), F_OK)) {
xumount(pts.data());
rmdir(pts.data());
}
}
sockaddr_un sun;
socklen_t len = setup_sockaddr(&sun, MAIN_SOCKET);
fd = xsocket(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0);

1
native/jni/include/magisk.hpp
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@ -22,6 +22,7 @@ extern std::string MAGISKTMP;
#define MODULEMNT INTLROOT "/modules"
#define BBPATH INTLROOT "/busybox"
#define ROOTOVL INTLROOT "/rootdir"
#define SHELLPTS INTLROOT "/pts"
#define ROOTMNT ROOTOVL "/.mount_list"
constexpr const char *applet_names[] = { "su", "resetprop", "magiskhide", nullptr };

4
native/jni/magiskhide/hide_policy.cpp
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@ -35,6 +35,10 @@ void hide_unmount(int pid) {
// Unmount dummy skeletons and MAGISKTMP
targets.push_back(MAGISKTMP);
auto magiskpts = MAGISKTMP + "/" SHELLPTS;
if (access(magiskpts.data(), F_OK) == 0) {
targets.push_back(magiskpts);
}
parse_mnt("/proc/self/mounts", [&](mntent *mentry) {
if (TMPFS_MNT(system) || TMPFS_MNT(vendor) || TMPFS_MNT(product) || TMPFS_MNT(system_ext))
targets.emplace_back(mentry->mnt_dir);

8
native/jni/su/pts.cpp
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@ -105,6 +105,14 @@ error:
return -1;
}
int get_pty_num(int fd) {
int pty_num = -1;
if (ioctl(fd, TIOCGPTN, &pty_num) != 0) {
return -1;
}
return pty_num;
}
// Stores the previous termios of stdin
static struct termios old_stdin;
static int stdin_is_raw = 0;

9
native/jni/su/pts.hpp
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@ -29,10 +29,13 @@
*/
int pts_open(char *slave_name, size_t slave_name_size);
int get_pty_num(int fd);
/**
* set_stdin_raw
*
* Changes stdin to raw unbuffered mode, disables echo,
* Changes stdin to raw unbuffered mode, disables echo,
* auto carriage return, etc.
*
* Return Value
@ -60,7 +63,7 @@ int restore_stdin(void);
* watch_sigwinch_async
*
* After calling this function, if the application receives
* SIGWINCH, the terminal window size will be read from
* SIGWINCH, the terminal window size will be read from
* "input" and set on "output".
*
* NOTE: This function blocks SIGWINCH and spawns a thread.
@ -72,7 +75,7 @@ int restore_stdin(void);
*
* Return Value
* on failure, -1 and errno will be set. In this case, no
* thread has been spawned and SIGWINCH will not be
* thread has been spawned and SIGWINCH will not be
* blocked.
* on success, 0
*/

19
native/jni/su/su.cpp
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@ -156,7 +156,6 @@ int su_client_main(int argc, char *argv[]) {
optind++;
}
char pts_slave[PATH_MAX];
int ptmx, fd;
// Connect to client
@ -183,16 +182,6 @@ int su_client_main(int argc, char *argv[]) {
if (isatty(STDOUT_FILENO)) atty |= ATTY_OUT;
if (isatty(STDERR_FILENO)) atty |= ATTY_ERR;
if (atty) {
// We need a PTY. Get one.
ptmx = pts_open(pts_slave, sizeof(pts_slave));
} else {
pts_slave[0] = '\0';
}
// Send pts_slave
write_string(fd, pts_slave);
// Send stdin
send_fd(fd, (atty & ATTY_IN) ? -1 : STDIN_FILENO);
// Send stdout
@ -200,6 +189,14 @@ int su_client_main(int argc, char *argv[]) {
// Send stderr
send_fd(fd, (atty & ATTY_ERR) ? -1 : STDERR_FILENO);
if (atty) {
// We need a PTY. Get one.
write_int(fd, 1);
ptmx = recv_fd(fd);
} else {
write_int(fd, 0);
}
if (atty) {
setup_sighandlers(sighandler);
watch_sigwinch_async(STDOUT_FILENO, ptmx);

40
native/jni/su/su_daemon.cpp
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@ -6,6 +6,7 @@
#include <sys/mount.h>
#include <daemon.hpp>
#include <magisk.hpp>
#include <utils.hpp>
#include <selinux.hpp>
#include <db.hpp>
@ -222,23 +223,32 @@ void su_daemon_handler(int client, struct ucred *credential) {
// Become session leader
xsetsid();
// Get pts_slave
string pts_slave = read_string(client);
// The FDs for each of the streams
int infd = recv_fd(client);
int infd = recv_fd(client);
int outfd = recv_fd(client);
int errfd = recv_fd(client);
if (!pts_slave.empty()) {
LOGD("su: pts_slave=[%s]\n", pts_slave.data());
// Check pts_slave file is owned by daemon_from_uid
struct stat st;
xstat(pts_slave.data(), &st);
// App need a PTY
if (read_int(client)) {
string pts;
string ptmx;
auto magiskpts = MAGISKTMP + "/" SHELLPTS;
if (access(magiskpts.data(), F_OK)) {
pts = "/dev/pts";
ptmx = "/dev/ptmx";
} else {
pts = magiskpts;
ptmx = magiskpts + "/ptmx";
}
int ptmx_fd = xopen(ptmx.data(), O_RDWR);
int unlock = 0;
ioctl(ptmx_fd, TIOCSPTLCK, &unlock);
send_fd(client, ptmx_fd);
int pty_num = get_pty_num(ptmx_fd);
close(ptmx_fd);
// If caller is not root, ensure the owner of pts_slave is the caller
if(st.st_uid != ctx.info->uid && ctx.info->uid != 0)
LOGE("su: Wrong permission of pts_slave\n");
string pts_slave = pts + "/" + to_string(pty_num);
LOGD("su: pts_slave=[%s]\n", pts_slave.data());
// Opening the TTY has to occur after the
// fork() and setsid() so that it becomes
@ -258,11 +268,6 @@ void su_daemon_handler(int client, struct ucred *credential) {
xdup2(outfd, STDOUT_FILENO);
xdup2(errfd, STDERR_FILENO);
// Unleash all streams from SELinux hell
setfilecon("/proc/self/fd/0", "u:object_r:" SEPOL_FILE_TYPE ":s0");
setfilecon("/proc/self/fd/1", "u:object_r:" SEPOL_FILE_TYPE ":s0");
setfilecon("/proc/self/fd/2", "u:object_r:" SEPOL_FILE_TYPE ":s0");
close(infd);
close(outfd);
close(errfd);
@ -331,5 +336,4 @@ void su_daemon_handler(int client, struct ucred *credential) {
execvp(ctx.req.shell.data(), (char **) argv);
fprintf(stderr, "Cannot execute %s: %s\n", ctx.req.shell.data(), strerror(errno));
PLOGE("exec");
exit(EXIT_FAILURE);
}

2
native/jni/utils/logging.cpp
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@ -54,4 +54,4 @@ void LOGD(const char *fmt, ...) {}
#endif
void LOGI(const char *fmt, ...) { LOG_BODY(i) }
void LOGW(const char *fmt, ...) { LOG_BODY(w) }
void LOGE(const char *fmt, ...) { LOG_BODY(e); log_cb.ex(1); }
void LOGE(const char *fmt, ...) { LOG_BODY(e); log_cb.ex(EXIT_FAILURE); }