我正在编写一个程序来替换另一个进程的内存中的字符串.它需要用C语言编写,因为我的目标平台不支持任何更高级别的语言.
最初,我不是直接跳转到内存修改,而只是尝试将内存读入缓冲区,这样我就可以识别字节串所在的偏移量,这样我就可以开始修改它了.
我已经阅读了我可以找到的每个堆栈溢出问题和代码示例,以及手册页和一些一般的试错.我的C有点生疏,所以这证明是相当具有挑战性的.我读过的例子似乎采取了两种不同的方法:
> ptrace_attatch到目标进程,使用多次调用ptrace_peekdata从offset中读取(int)大小的内存块.
要么
> ptrace_attatch,open / proc / pid / mem,并使用/ proc / pid / maps中列出的偏移量来lseek和read()输出给定的字节数.
这是我的代码.
附加到的程序:
#include <stdio.h>
int main(int argc, char *argv[]){
printf("Spinning up....\n");
char changeme[6] = "AAAAA";
printf("ready for change....\n");
getchar();
printf("changeme is %s\n", changeme);
return 0;
}
转储内存的程序:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/user.h>
#include <sys/syscall.h>
#include <unistd.h>
#include <limits.h>
#include <stdint.h>
#include <fcntl.h>
#include <wait.h>
#include <errno.h>
int main(int argc, char *argv[]){
char mempath[PATH_MAX];
uintptr_t const address = strtoul(argv[2], NULL, 0);
int waitval = 0;
pid_t target_process = atoi(argv[1]);
struct user_regs_struct regs;
int readbytes = 0;
if (ptrace(PTRACE_ATTACH,target_process,NULL,NULL))
perror("attach");
printf("attatched!\n");
waitpid(target_process, NULL, 0);
sprintf(mempath, "/proc/%s/mem", argv[1]);
printf("ready! opening %s\n", mempath);
int memfd = open(mempath, O_RDONLY);
printf("memfd = %d\n", memfd);
char *outbuf = malloc(_SC_PAGE_SIZE);
printf("trying to read %d bytes from offset %lu\n",_SC_PAGE_SIZE,address);
if (outbuf){
lseek(memfd, address, SEEK_SET);
readbytes = read(memfd, outbuf, _SC_PAGE_SIZE);
if (_SC_PAGE_SIZE == readbytes)
printf("read success! - %s\n", outbuf);
else
printf("readfailed! read %d bytes: %s\n", readbytes, outbuf);
printf("oh noes! %s\n", strerror(errno));
free(outbuf);
}
return 0;
}
终端输出:
1号航站楼:
[10:59] tel0s@Relentless:~/research$./changeme
Spinning up....
ready for change....
终端2:
[11:35] tel0s@Relentless:~/research$ps aux | grep changeme tel0s 7763 0.0 0.0 4076 352 pts/2 S+ 10:59 0:00 ./changeme tel0s 8297 0.0 0.0 8948 928 pts/1 S+ 11:35 0:00 grep --colour=auto changeme [11:35] tel0s@Relentless:~/research$cat /proc/7763/maps 00400000-00401000 r-xp 00000000 fd:00 2260791 /home/tel0s/research/changeme 0
#include <stdio.h> int main(int argc, char *argv[]){ printf("Spinning up....\n"); char changeme[6] = "AAAAA"; printf("ready for change....\n"); getchar(); printf("changeme is %s\n", changeme); return 0; }
00-00601000 r--p 00000000 fd:00 2260791 /home/tel0s/research/changeme
00601000-00602000 rw-p 00001000 fd:00 2260791 /home/tel0s/research/changeme
7fb2cfc56000-7fb2cfdf7000 r-xp 00000000 fd:00 4890420 /lib64/libc-2.17.so
7fb2cfdf7000-7fb2cfff6000 ---p 001a1000 fd:00 4890420 /lib64/libc-2.17.so
7fb2cfff6000-7fb2cfffa000 r--p 001a0000 fd:00 4890420 /lib64/libc-2.17.so
7fb2cfffa000-7fb2cfffc000 rw-p 001a4000 fd:00 4890420 /lib64/libc-2.17.so
7fb2cfffc000-7fb2d0000000 rw-p 00000000 00:00 0
7fb2d0000000-7fb2d0022000 r-xp 00000000 fd:00 4888842 /lib64/ld-2.17.so
7fb2d01f2000-7fb2d01f5000 rw-p 00000000 00:00 0
7fb2d021e000-7fb2d0221000 rw-p 00000000 00:00 0
7fb2d0221000-7fb2d0222000 r--p 00021000 fd:00 4888842 /lib64/ld-2.17.so
7fb2d0222000-7fb2d0223000 rw-p 00022000 fd:00 4888842 /lib64/ld-2.17.so
7fb2d0223000-7fb2d0224000 rw-p 00000000 00:00 0
7fff03290000-7fff032b1000 rw-p 00000000 00:00 0 [stack]
7fff03394000-7fff03395000 r-xp 00000000 00:00 0 [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]
[11:36] tel0s@Relentless:~/research$sudo ./writeprocmem 7763 400000
attatched!
ready! opening /proc/7763/mem
memfd = 3
trying to read 30 bytes from offset 400000
readfailed! read -1 bytes:
oh noes! Input/output error
我可能的原因是:
>我完全沉溺了我的逻辑,我没有正确使用Ptrace.
>我的changeme程序因为gets()而处于一种奇怪的状态,这就是我无法读取的原因(我尝试使用bash实例,然而我有相同的输出)
>我没有为我的偏移量使用正确的类型,这就是读取失败的原因任何帮助都会非常好,我宁愿回答一下我所犯的错误,而不是直接给我工作代码,因为我想从根本上理解这一点,而不仅仅是让我的代码正常运行.
最佳答案 您应该检查系统调用的返回状态.如果它们失败,将设置errno以指示出错的地方,并且您可以使用perror()显示相关文本.
例如.就像是:
if (lseek(memfd, address, SEEK_SET) < 0) { perror("lseek"); } readbytes = read(memfd, outbuf, _SC_PAGE_SIZE); if (readbytes < 0) { perror("read"); }
罗伊山