userspace/su: add ndk compatible su from kernelnosu

Co-authored-by: nampud <nampud@users.noreply.github.com>

userspace/su/jni/su.c

@@ -1,11 +1,54 @@
+#include <string.h>
+#include <stdio.h>
 #include <unistd.h>
-#include <stdlib.h>
 #include <sys/prctl.h>
+#include <sys/ioctl.h>
+#include <sys/xattr.h>
+#include <limits.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <termios.h>
 
-// This is a simple example. If you want a full-featured "su", please use "/data/adb/ksud debug su".
+#define KERNEL_SU_OPTION 0xDEADBEEF
-int main(){
+#define CMD_GRANT_ROOT 0
-    int32_t result = 0;
+#define CMD_ENABLE_SU 15
-    prctl(0xdeadbeef, 0, 0, 0, &result);
+
-    system("/system/bin/sh");
+int main(int argc, char **argv, char **envp) {
-    return 0;
+    unsigned long result = 0;
+
+    if (argc >= 2 && strcmp(argv[1], "--disable-sucompat") == 0) {
+        prctl(KERNEL_SU_OPTION, CMD_ENABLE_SU, 0L, 0L, (unsigned long)&result);
+        return 0;
+    }
+
+    prctl(KERNEL_SU_OPTION, CMD_GRANT_ROOT, 0L, 0L, (unsigned long)&result);
+    if (result != KERNEL_SU_OPTION) {
+        const char *error = "Access Denied: sucompat not permitted\n";
+        write(STDERR_FILENO, error, strlen(error));
+        return 1;
+    }
+
+    struct termios term;
+    if (ioctl(STDIN_FILENO, TCGETS, &term) == 0) {
+        char tty_path[PATH_MAX];
+        ssize_t len = readlink("/proc/self/fd/0", tty_path, sizeof(tty_path) - 1);
+        if (len > 0) {
+            tty_path[len] = '\0';
+            const char *selinux_ctx = "u:object_r:devpts:s0";
+            setxattr(tty_path, "security.selinux", selinux_ctx, strlen(selinux_ctx) + 1, 0);
+        }
+    }
+
+    const char *default_args[] = { "/system/bin/su", NULL };
+    if (argc < 1 || !argv) {
+        argv = (char **)default_args;
+    } else {
+        argv[0] = "/system/bin/su";
+    }
+
+    execve("/data/adb/ksud", argv, envp);
+
+    const char *error = "Error: Failed to execve /data/adb/ksud\n";
+    write(STDERR_FILENO, error, strlen(error));
+    return 1;
 }