userspace/su: implement basic features (#62)

userspace/su/jni/Android.mk

@@ -3,5 +3,9 @@ LOCAL_PATH := $(call my-dir)
 include $(CLEAR_VARS)
 LOCAL_MODULE := su
 LOCAL_SRC_FILES := su.c
-
+include $(BUILD_EXECUTABLE)
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := simple_su
+LOCAL_SRC_FILES := simple_su.c
 include $(BUILD_EXECUTABLE)

userspace/su/jni/simple_su.c

@@ -0,0 +1,10 @@
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/prctl.h>
+
+int main(){
+    int32_t result = 0;
+    prctl(0xdeadbeef, 0, 0, 0, &result);
+    system("/system/bin/sh");
+    return 0;
+}

userspace/su/jni/su.c

@@ -1,10 +1,110 @@
+#include <stdio.h>
+#include <string.h>
 #include <unistd.h>
 #include <stdlib.h>
+#include <stdbool.h>
 #include <sys/prctl.h>
 
-int main(){
+#define CMD_GRANT_ROOT 0
+#define CMD_GET_VERSION 2
+
+static void help(int status) {
+
+    printf("KernelSU\n"
+        "Usage: su [options] [argument...]\n\n"
+        "Options: \n"
+        "-c Pass command to invoked shell\n"
+        "-v Print version code and exit\n"
+        "-h Display this message and exit\n"
+    );
+    exit(status);
+
+}
+
+static bool ksuctl(int cmd, void * arg1, void * arg2) {
+
     int32_t result = 0;
-    prctl(0xdeadbeef, 0, 0, 0, &result);
+    prctl(0xDEADBEEF, cmd, arg1, arg2, & result);
-    system("/system/bin/sh");
+    return result == 0xDEADBEEF;
+
+}
+
+void elevate() {
+
+    // Talk to Daemon in Kernel Space
+    bool status = ksuctl(CMD_GRANT_ROOT, 0, NULL);
+
+    if (!status) {
+        fprintf(stderr, "Permission denied\n");
+        exit(EXIT_FAILURE);
+    }
+
+}
+
+int getver() {
+
+    elevate();
+
+    int32_t version = -1;
+    ksuctl(CMD_GET_VERSION, & version, NULL);
+    
+    return version;
+}
+
+void su_shell(char * envp[]) {
+
+    char * shell = getenv("SHELL");
+    int status;
+
+    elevate();
+
+    if (shell) {
+        status = execve(shell, NULL, envp);
+    } else {
+        status = execve("/system/bin/sh", NULL, envp);
+    }
+
+    exit(status);
+}
+
+void su_command(char * command[], int len) {
+
+    elevate();
+    int status;
+
+    if (len == 1) {
+        status = system(command[0]);
+    } else {
+        status = execvp(command[0], command);
+    }
+    exit(status);
+}
+
+int main(int argc, char * argv[], char * envp[]) {
+
+    if (argc == 1) {
+        su_shell(envp);
+    }
+
+    int opt;
+
+    while ((opt = getopt(argc, argv, "vch")) != -1) {
+        switch (opt) {
+        case 'v': {
+            int version = getver();
+            printf("%d:KernelSU\n", version);
+            exit(EXIT_SUCCESS);
+        }
+        case 'c':
+            if (argc < 3) {
+                fprintf(stderr, "ERROR: -c requires an argument\n\n");
+                help(EXIT_FAILURE);
+            }
+            su_command(argv + 2, argc - 2);
+        case 'h':
+        default:
+            help(EXIT_SUCCESS);
+        }
+    }
     return 0;
 }