ptrace 反调试

　

前言：

　　在动手尝试MBE系列课程第一天中的小程序时，遇到了一个ptrace反调试的问题，当然简单的做一次patch也是可以的。但是本着打破沙锅问到底的精神，到网上查看了一些资料，整理到这里。

　　分别转载自 如何调试加入了ptrace的程序 以及 玩转ptrace。 

　　以及，一下内容我并未亲自尝试。难免会有不足之处，后面会慢慢补充，有错之处请大家指出，谢谢分享。

 

ptrace 简介：

　　你想过怎么实现对系统调用的拦截吗？你尝试过通过改变系统调用的参数来愚弄你的系统kernel吗？你想过调试器是如何使运行中的进程暂停并且控制它吗？

　　你可能会开始考虑怎么使用复杂的kernel编程来达到目的，那么，你错了。实际上Linux提供了一种优雅的机制来完成这些：ptrace系统函数。 ptrace提供了一种使父进程得以监视和控制其它进程的方式，它还能够改变子进程中的寄存器和内核映像，因而可以实现断点调试和系统调用的跟踪。

　　使用ptrace，你可以在用户层拦截和修改系统调用(sys call)，修改它的参数，插入代码给正在运行的程序以及偷窥和篡改进程的寄存器和数据段。

　　具体的使用暂不深究，有兴趣的同学可以点进上方链接去学习学习；

 

　　ptrace函数原型

　　

　　request：请求执行的行为

　　pid：目标进程标识。
　　addr：执行peek和poke操作的目标地址。 
　　data：对于poke操作，存放数据的地方。对于peek操作，获取数据的地方。

　　其中request有如下选择：

#define PT_TRACE_ME 0 /* child declares it's being traced */
#define PT_READ_I 1 /* read word in child's I space */
#define PT_READ_D 2 /* read word in child's D space */
#define PT_READ_U 3 /* read word in child's user structure */
#define PT_WRITE_I 4 /* write word in child's I space */
#define PT_WRITE_D 5 /* write word in child's D space */
#define PT_WRITE_U 6 /* write word in child's user structure */
#define PT_CONTINUE 7 /* continue the child */
#define PT_KILL 8 /* kill the child process */
#define PT_STEP 9 /* single step the child */
#define PT_ATTACH 10 /* trace some running process */
#define PT_DETACH 11 /* stop tracing a process */
#define PT_SIGEXC 12 /* signals as exceptions for current_proc */
#define PT_THUPDATE 13 /* signal for thread# */
#define PT_ATTACHEXC 14 /* attach to running process with signal exception */
#define PT_FORCEQUOTA 30 /* Enforce quota for root */
#define PT_DENY_ATTACH 31
#define PT_FIRSTMACH 32 /* for machine-specific requests */

　　其中addr我理解为系统调用号，其详细内容可以查看 /usr/include/asm/unistd.h

　　此处给出unistd_32.h的内容

#ifndef _ASM_X86_UNISTD_32_H
#define _ASM_X86_UNISTD_32_H 1
#define __NR_restart_syscall 0
#define __NR_exit 1
#define __NR_fork 2
#define __NR_read 3
#define __NR_write 4
#define __NR_open 5
#define __NR_close 6
#define __NR_waitpid 7
#define __NR_creat 8
#define __NR_link 9
#define __NR_unlink 10
#define __NR_execve 11
#define __NR_chdir 12
#define __NR_time 13
#define __NR_mknod 14
#define __NR_chmod 15
#define __NR_lchown 16
#define __NR_break 17
#define __NR_oldstat 18
#define __NR_lseek 19
#define __NR_getpid 20
#define __NR_mount 21
#define __NR_umount 22
#define __NR_setuid 23
#define __NR_getuid 24
#define __NR_stime 25
#define __NR_ptrace 26
#define __NR_alarm 27
#define __NR_oldfstat 28
#define __NR_pause 29
#define __NR_utime 30
#define __NR_stty 31
#define __NR_gtty 32
#define __NR_access 33
#define __NR_nice 34
#define __NR_ftime 35
#define __NR_sync 36
#define __NR_kill 37
#define __NR_rename 38
#define __NR_mkdir 39
#define __NR_rmdir 40
#define __NR_dup 41
#define __NR_pipe 42
#define __NR_times 43
#define __NR_prof 44
#define __NR_brk 45
#define __NR_setgid 46
#define __NR_getgid 47
#define __NR_signal 48
#define __NR_geteuid 49
#define __NR_getegid 50
#define __NR_acct 51
#define __NR_umount2 52
#define __NR_lock 53
#define __NR_ioctl 54
#define __NR_fcntl 55
#define __NR_mpx 56
#define __NR_setpgid 57
#define __NR_ulimit 58
#define __NR_oldolduname 59
#define __NR_umask 60
#define __NR_chroot 61
#define __NR_ustat 62
#define __NR_dup2 63
#define __NR_getppid 64
#define __NR_getpgrp 65
#define __NR_setsid 66
#define __NR_sigaction 67
#define __NR_sgetmask 68
#define __NR_ssetmask 69
#define __NR_setreuid 70
#define __NR_setregid 71
#define __NR_sigsuspend 72
#define __NR_sigpending 73
#define __NR_sethostname 74
#define __NR_setrlimit 75
#define __NR_getrlimit 76
#define __NR_getrusage 77
#define __NR_gettimeofday 78
#define __NR_settimeofday 79
#define __NR_getgroups 80
#define __NR_setgroups 81
#define __NR_select 82
#define __NR_symlink 83
#define __NR_oldlstat 84
#define __NR_readlink 85
#define __NR_uselib 86
#define __NR_swapon 87
#define __NR_reboot 88
#define __NR_readdir 89
#define __NR_mmap 90
#define __NR_munmap 91
#define __NR_truncate 92
#define __NR_ftruncate 93
#define __NR_fchmod 94
#define __NR_fchown 95
#define __NR_getpriority 96
#define __NR_setpriority 97
#define __NR_profil 98
#define __NR_statfs 99
#define __NR_fstatfs 100
#define __NR_ioperm 101
#define __NR_socketcall 102
#define __NR_syslog 103
#define __NR_setitimer 104
#define __NR_getitimer 105
#define __NR_stat 106
#define __NR_lstat 107
#define __NR_fstat 108
#define __NR_olduname 109
#define __NR_iopl 110
#define __NR_vhangup 111
#define __NR_idle 112
#define __NR_vm86old 113
#define __NR_wait4 114
#define __NR_swapoff 115
#define __NR_sysinfo 116
#define __NR_ipc 117
#define __NR_fsync 118
#define __NR_sigreturn 119
#define __NR_clone 120
#define __NR_setdomainname 121
#define __NR_uname 122
#define __NR_modify_ldt 123
#define __NR_adjtimex 124
#define __NR_mprotect 125
#define __NR_sigprocmask 126
#define __NR_create_module 127
#define __NR_init_module 128
#define __NR_delete_module 129
#define __NR_get_kernel_syms 130
#define __NR_quotactl 131
#define __NR_getpgid 132
#define __NR_fchdir 133
#define __NR_bdflush 134
#define __NR_sysfs 135
#define __NR_personality 136
#define __NR_afs_syscall 137
#define __NR_setfsuid 138
#define __NR_setfsgid 139
#define __NR__llseek 140
#define __NR_getdents 141
#define __NR__newselect 142
#define __NR_flock 143
#define __NR_msync 144
#define __NR_readv 145
#define __NR_writev 146
#define __NR_getsid 147
#define __NR_fdatasync 148
#define __NR__sysctl 149
#define __NR_mlock 150
#define __NR_munlock 151
#define __NR_mlockall 152
#define __NR_munlockall 153
#define __NR_sched_setparam 154
#define __NR_sched_getparam 155
#define __NR_sched_setscheduler 156
#define __NR_sched_getscheduler 157
#define __NR_sched_yield 158
#define __NR_sched_get_priority_max 159
#define __NR_sched_get_priority_min 160
#define __NR_sched_rr_get_interval 161
#define __NR_nanosleep 162
#define __NR_mremap 163
#define __NR_setresuid 164
#define __NR_getresuid 165
#define __NR_vm86 166
#define __NR_query_module 167
#define __NR_poll 168
#define __NR_nfsservctl 169
#define __NR_setresgid 170
#define __NR_getresgid 171
#define __NR_prctl 172
#define __NR_rt_sigreturn 173
#define __NR_rt_sigaction 174
#define __NR_rt_sigprocmask 175
#define __NR_rt_sigpending 176
#define __NR_rt_sigtimedwait 177
#define __NR_rt_sigqueueinfo 178
#define __NR_rt_sigsuspend 179
#define __NR_pread64 180
#define __NR_pwrite64 181
#define __NR_chown 182
#define __NR_getcwd 183
#define __NR_capget 184
#define __NR_capset 185
#define __NR_sigaltstack 186
#define __NR_sendfile 187
#define __NR_getpmsg 188
#define __NR_putpmsg 189
#define __NR_vfork 190
#define __NR_ugetrlimit 191
#define __NR_mmap2 192
#define __NR_truncate64 193
#define __NR_ftruncate64 194
#define __NR_stat64 195
#define __NR_lstat64 196
#define __NR_fstat64 197
#define __NR_lchown32 198
#define __NR_getuid32 199
#define __NR_getgid32 200
#define __NR_geteuid32 201
#define __NR_getegid32 202
#define __NR_setreuid32 203
#define __NR_setregid32 204
#define __NR_getgroups32 205
#define __NR_setgroups32 206
#define __NR_fchown32 207
#define __NR_setresuid32 208
#define __NR_getresuid32 209
#define __NR_setresgid32 210
#define __NR_getresgid32 211
#define __NR_chown32 212
#define __NR_setuid32 213
#define __NR_setgid32 214
#define __NR_setfsuid32 215
#define __NR_setfsgid32 216
#define __NR_pivot_root 217
#define __NR_mincore 218
#define __NR_madvise 219
#define __NR_getdents64 220
#define __NR_fcntl64 221
#define __NR_gettid 224
#define __NR_readahead 225
#define __NR_setxattr 226
#define __NR_lsetxattr 227
#define __NR_fsetxattr 228
#define __NR_getxattr 229
#define __NR_lgetxattr 230
#define __NR_fgetxattr 231
#define __NR_listxattr 232
#define __NR_llistxattr 233
#define __NR_flistxattr 234
#define __NR_removexattr 235
#define __NR_lremovexattr 236
#define __NR_fremovexattr 237
#define __NR_tkill 238
#define __NR_sendfile64 239
#define __NR_futex 240
#define __NR_sched_setaffinity 241
#define __NR_sched_getaffinity 242
#define __NR_set_thread_area 243
#define __NR_get_thread_area 244
#define __NR_io_setup 245
#define __NR_io_destroy 246
#define __NR_io_getevents 247
#define __NR_io_submit 248
#define __NR_io_cancel 249
#define __NR_fadvise64 250
#define __NR_exit_group 252
#define __NR_lookup_dcookie 253
#define __NR_epoll_create 254
#define __NR_epoll_ctl 255
#define __NR_epoll_wait 256
#define __NR_remap_file_pages 257
#define __NR_set_tid_address 258
#define __NR_timer_create 259
#define __NR_timer_settime 260
#define __NR_timer_gettime 261
#define __NR_timer_getoverrun 262
#define __NR_timer_delete 263
#define __NR_clock_settime 264
#define __NR_clock_gettime 265
#define __NR_clock_getres 266
#define __NR_clock_nanosleep 267
#define __NR_statfs64 268
#define __NR_fstatfs64 269
#define __NR_tgkill 270
#define __NR_utimes 271
#define __NR_fadvise64_64 272
#define __NR_vserver 273
#define __NR_mbind 274
#define __NR_get_mempolicy 275
#define __NR_set_mempolicy 276
#define __NR_mq_open 277
#define __NR_mq_unlink 278
#define __NR_mq_timedsend 279
#define __NR_mq_timedreceive 280
#define __NR_mq_notify 281
#define __NR_mq_getsetattr 282
#define __NR_kexec_load 283
#define __NR_waitid 284
#define __NR_add_key 286
#define __NR_request_key 287
#define __NR_keyctl 288
#define __NR_ioprio_set 289
#define __NR_ioprio_get 290
#define __NR_inotify_init 291
#define __NR_inotify_add_watch 292
#define __NR_inotify_rm_watch 293
#define __NR_migrate_pages 294
#define __NR_openat 295
#define __NR_mkdirat 296
#define __NR_mknodat 297
#define __NR_fchownat 298
#define __NR_futimesat 299
#define __NR_fstatat64 300
#define __NR_unlinkat 301
#define __NR_renameat 302
#define __NR_linkat 303
#define __NR_symlinkat 304
#define __NR_readlinkat 305
#define __NR_fchmodat 306
#define __NR_faccessat 307
#define __NR_pselect6 308
#define __NR_ppoll 309
#define __NR_unshare 310
#define __NR_set_robust_list 311
#define __NR_get_robust_list 312
#define __NR_splice 313
#define __NR_sync_file_range 314
#define __NR_tee 315
#define __NR_vmsplice 316
#define __NR_move_pages 317
#define __NR_getcpu 318
#define __NR_epoll_pwait 319
#define __NR_utimensat 320
#define __NR_signalfd 321
#define __NR_timerfd_create 322
#define __NR_eventfd 323
#define __NR_fallocate 324
#define __NR_timerfd_settime 325
#define __NR_timerfd_gettime 326
#define __NR_signalfd4 327
#define __NR_eventfd2 328
#define __NR_epoll_create1 329
#define __NR_dup3 330
#define __NR_pipe2 331
#define __NR_inotify_init1 332
#define __NR_preadv 333
#define __NR_pwritev 334
#define __NR_rt_tgsigqueueinfo 335
#define __NR_perf_event_open 336
#define __NR_recvmmsg 337
#define __NR_fanotify_init 338
#define __NR_fanotify_mark 339
#define __NR_prlimit64 340
#define __NR_name_to_handle_at 341
#define __NR_open_by_handle_at 342
#define __NR_clock_adjtime 343
#define __NR_syncfs 344
#define __NR_sendmmsg 345
#define __NR_setns 346
#define __NR_process_vm_readv 347
#define __NR_process_vm_writev 348
#define __NR_kcmp 349
#define __NR_finit_module 350
#define __NR_sched_setattr 351
#define __NR_sched_getattr 352
#define __NR_renameat2 353
#define __NR_seccomp 354
#endif /* _ASM_X86_UNISTD_32_H */

 

 

　　反调试中一般使用方法

 

 　　ptrace(PT_DENY_ATTACH, 0, 0, 0);

　　 在反汇编下看到的是

　　

　　0x1f == 31 == PT_DENY_ATTACH   拒绝附加调试

　　想想如果把 request 这个参数修改为 PT_ATTACH 允许附加调试呢

　　就把 BF1F000000 这一行的1F修改为0A (0A== 10 == PT_ATTACH)

　　即 BF0A000000

　　

　　然后再挂上GDB就会看到

　　

　　

　　但是实际中我在MBE中lab1A的小程序中，看到的是PT_TRACEME，依然起到了反调试的作用，具体原因暂未知，以后知道了再来补充

　　

 

 　　3.7 更新：

  　　ptrace还可以监控syscall函数的使用，相关代码如下：

/* grab the syscall # */
syscall = ptrace(PTRACE_PEEKUSER, child, 4 * ORIG_EAX, NULL);
/* filter out syscall 11, exec */
if(syscall == 11)
{
printf("no exec() for youn");
return 0;
}