Use isolated devpts if kernel support

kernel version >= 4.7 or CONFIG_DEVPTS_MULTIPLE_INSTANCES=y

native/jni/core/daemon.cpp

@@ -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);

native/jni/include/magisk.hpp

@@ -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 };

native/jni/magiskhide/hide_policy.cpp

@@ -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);

native/jni/su/pts.cpp

@@ -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;

native/jni/su/pts.hpp

@@ -29,6 +29,9 @@
  */
 int pts_open(char *slave_name, size_t slave_name_size);
 
+
+int get_pty_num(int fd);
+
 /**
  * set_stdin_raw
  *

native/jni/su/su.cpp

@@ -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);

native/jni/su/su_daemon.cpp

@@ -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()) {
+    // App need a PTY
-        LOGD("su: pts_slave=[%s]\n", pts_slave.data());
+    if (read_int(client)) {
-        // Check pts_slave file is owned by daemon_from_uid
+        string pts;
-        struct stat st;
+        string ptmx;
-        xstat(pts_slave.data(), &st);
+        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
+        string pts_slave = pts + "/" + to_string(pty_num);
-        if(st.st_uid != ctx.info->uid && ctx.info->uid != 0)
+        LOGD("su: pts_slave=[%s]\n", pts_slave.data());
-            LOGE("su: Wrong permission of pts_slave\n");
 
         // 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);
 }

native/jni/utils/logging.cpp

@@ -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); }