/* american fuzzy lop++ - strcmp() / memcmp() CompareCoverage library ------------------------------------------------------------------ Written and maintained by Andrea Fioraldi Copyright 2019-2020 AFLplusplus Project. All rights reserved. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at: http://www.apache.org/licenses/LICENSE-2.0 This Linux-only companion library allows you to instrument strcmp(), memcmp(), and related functions to get compare coverage. See README.md for more info. */ #ifndef _GNU_SOURCE #define _GNU_SOURCE #endif #include #include #include #include #include #include #include #include "types.h" #include "config.h" #include "pmparser.h" #ifndef __linux__ #error "Sorry, this library is Linux-specific for now!" #endif /* !__linux__ */ /* Change this value to tune the compare coverage */ #define MAX_CMP_LENGTH 32 static void *__compcov_code_start, *__compcov_code_end; static u8* __compcov_afl_map; static u32 __compcov_level; static int (*__libc_strcmp)(const char*, const char*); static int (*__libc_strncmp)(const char*, const char*, size_t); static int (*__libc_strcasecmp)(const char*, const char*); static int (*__libc_strncasecmp)(const char*, const char*, size_t); static int (*__libc_memcmp)(const void*, const void*, size_t); static int debug_fd = -1; #define MAX_MAPPINGS 1024 static struct mapping { void *st, *en; } __compcov_ro[MAX_MAPPINGS]; static u32 __compcov_ro_cnt; /* Check an address against the list of read-only mappings. */ static u8 __compcov_is_ro(const void* ptr) { u32 i; for (i = 0; i < __compcov_ro_cnt; i++) if (ptr >= __compcov_ro[i].st && ptr <= __compcov_ro[i].en) return 1; return 0; } static size_t __strlen2(const char* s1, const char* s2, size_t max_length) { // from https://github.com/googleprojectzero/CompareCoverage size_t len = 0; for (; len < max_length && s1[len] != '\0' && s2[len] != '\0'; len++) {} return len; } /* Identify the binary boundaries in the memory mapping */ static void __compcov_load(void) { __libc_strcmp = dlsym(RTLD_NEXT, "strcmp"); __libc_strncmp = dlsym(RTLD_NEXT, "strncmp"); __libc_strcasecmp = dlsym(RTLD_NEXT, "strcasecmp"); __libc_strncasecmp = dlsym(RTLD_NEXT, "strncasecmp"); __libc_memcmp = dlsym(RTLD_NEXT, "memcmp"); if (getenv("AFL_QEMU_COMPCOV")) { __compcov_level = 1; } if (getenv("AFL_COMPCOV_LEVEL")) { __compcov_level = atoi(getenv("AFL_COMPCOV_LEVEL")); } char* id_str = getenv(SHM_ENV_VAR); int shm_id; if (id_str) { shm_id = atoi(id_str); __compcov_afl_map = shmat(shm_id, NULL, 0); if (__compcov_afl_map == (void*)-1) exit(1); } else { __compcov_afl_map = calloc(1, MAP_SIZE); } if (getenv("AFL_INST_LIBS")) { __compcov_code_start = (void*)0; __compcov_code_end = (void*)-1; return; } char* bin_name = getenv("AFL_COMPCOV_BINNAME"); procmaps_iterator* maps = pmparser_parse(-1); procmaps_struct* maps_tmp = NULL; while ((maps_tmp = pmparser_next(maps)) != NULL) { /* If AFL_COMPCOV_BINNAME is not set pick the first executable segment */ if (!bin_name || strstr(maps_tmp->pathname, bin_name) != NULL) { if (maps_tmp->is_x) { if (!__compcov_code_start) __compcov_code_start = maps_tmp->addr_start; if (!__compcov_code_end) __compcov_code_end = maps_tmp->addr_end; } } if ((maps_tmp->is_w && !maps_tmp->is_r) || __compcov_ro_cnt == MAX_MAPPINGS) continue; __compcov_ro[__compcov_ro_cnt].st = maps_tmp->addr_start; __compcov_ro[__compcov_ro_cnt].en = maps_tmp->addr_end; ++__compcov_ro_cnt; } pmparser_free(maps); } static void __compcov_trace(u64 cur_loc, const u8* v0, const u8* v1, size_t n) { size_t i; if (debug_fd != 1) { char debugbuf[4096]; snprintf(debugbuf, sizeof(debugbuf), "0x%llx %s %s %lu\n", cur_loc, v0 == NULL ? "(null)" : (char*)v0, v1 == NULL ? "(null)" : (char*)v1, n); write(debug_fd, debugbuf, strlen(debugbuf)); } for (i = 0; i < n && v0[i] == v1[i]; ++i) { __compcov_afl_map[cur_loc + i]++; } } /* Check an address against the list of read-only mappings. */ static u8 __compcov_is_in_bound(const void* ptr) { return ptr >= __compcov_code_start && ptr < __compcov_code_end; } /* Replacements for strcmp(), memcmp(), and so on. Note that these will be used only if the target is compiled with -fno-builtins and linked dynamically. */ #undef strcmp int strcmp(const char* str1, const char* str2) { void* retaddr = __builtin_return_address(0); if (__compcov_is_in_bound(retaddr) && !(__compcov_level < 2 && !__compcov_is_ro(str1) && !__compcov_is_ro(str2))) { size_t n = __strlen2(str1, str2, MAX_CMP_LENGTH + 1); if (n <= MAX_CMP_LENGTH) { u64 cur_loc = (u64)retaddr; cur_loc = (cur_loc >> 4) ^ (cur_loc << 8); cur_loc &= MAP_SIZE - 1; __compcov_trace(cur_loc, str1, str2, n); } } return __libc_strcmp(str1, str2); } #undef strncmp int strncmp(const char* str1, const char* str2, size_t len) { void* retaddr = __builtin_return_address(0); if (__compcov_is_in_bound(retaddr) && !(__compcov_level < 2 && !__compcov_is_ro(str1) && !__compcov_is_ro(str2))) { size_t n = __strlen2(str1, str2, MAX_CMP_LENGTH + 1); n = MIN(n, len); if (n <= MAX_CMP_LENGTH) { u64 cur_loc = (u64)retaddr; cur_loc = (cur_loc >> 4) ^ (cur_loc << 8); cur_loc &= MAP_SIZE - 1; __compcov_trace(cur_loc, str1, str2, n); } } return __libc_strncmp(str1, str2, len); } #undef strcasecmp int strcasecmp(const char* str1, const char* str2) { void* retaddr = __builtin_return_address(0); if (__compcov_is_in_bound(retaddr) && !(__compcov_level < 2 && !__compcov_is_ro(str1) && !__compcov_is_ro(str2))) { /* Fallback to strcmp, maybe improve in future */ size_t n = __strlen2(str1, str2, MAX_CMP_LENGTH + 1); if (n <= MAX_CMP_LENGTH) { u64 cur_loc = (u64)retaddr; cur_loc = (cur_loc >> 4) ^ (cur_loc << 8); cur_loc &= MAP_SIZE - 1; __compcov_trace(cur_loc, str1, str2, n); } } return __libc_strcasecmp(str1, str2); } #undef strncasecmp int strncasecmp(const char* str1, const char* str2, size_t len) { void* retaddr = __builtin_return_address(0); if (__compcov_is_in_bound(retaddr) && !(__compcov_level < 2 && !__compcov_is_ro(str1) && !__compcov_is_ro(str2))) { /* Fallback to strncmp, maybe improve in future */ size_t n = __strlen2(str1, str2, MAX_CMP_LENGTH + 1); n = MIN(n, len); if (n <= MAX_CMP_LENGTH) { u64 cur_loc = (u64)retaddr; cur_loc = (cur_loc >> 4) ^ (cur_loc << 8); cur_loc &= MAP_SIZE - 1; __compcov_trace(cur_loc, str1, str2, n); } } return __libc_strncasecmp(str1, str2, len); } #undef memcmp int memcmp(const void* mem1, const void* mem2, size_t len) { void* retaddr = __builtin_return_address(0); if (__compcov_is_in_bound(retaddr) && !(__compcov_level < 2 && !__compcov_is_ro(mem1) && !__compcov_is_ro(mem2))) { size_t n = len; if (n <= MAX_CMP_LENGTH) { u64 cur_loc = (u64)retaddr; cur_loc = (cur_loc >> 4) ^ (cur_loc << 8); cur_loc &= MAP_SIZE - 1; __compcov_trace(cur_loc, mem1, mem2, n); } } return __libc_memcmp(mem1, mem2, len); } // TODO bcmp /* Common libraries wrappers (from honggfuzz) */ /* * Apache's httpd wrappers */ int ap_cstr_casecmp(const char* s1, const char* s2) { return strcasecmp(s1, s2); } int ap_cstr_casecmpn(const char* s1, const char* s2, size_t n) { return strncasecmp(s1, s2, n); } int apr_cstr_casecmp(const char* s1, const char* s2) { return strcasecmp(s1, s2); } int apr_cstr_casecmpn(const char* s1, const char* s2, size_t n) { return strncasecmp(s1, s2, n); } /* * *SSL wrappers */ int CRYPTO_memcmp(const void* m1, const void* m2, size_t len) { return memcmp(m1, m2, len); } int OPENSSL_memcmp(const void* m1, const void* m2, size_t len) { return memcmp(m1, m2, len); } int OPENSSL_strcasecmp(const char* s1, const char* s2) { return strcasecmp(s1, s2); } int OPENSSL_strncasecmp(const char* s1, const char* s2, size_t len) { return strncasecmp(s1, s2, len); } int32_t memcmpct(const void* s1, const void* s2, size_t len) { return memcmp(s1, s2, len); } /* * libXML wrappers */ int xmlStrncmp(const char* s1, const char* s2, int len) { if (len <= 0) { return 0; } if (s1 == s2) { return 0; } if (s1 == NULL) { return -1; } if (s2 == NULL) { return 1; } return strncmp(s1, s2, (size_t)len); } int xmlStrcmp(const char* s1, const char* s2) { if (s1 == s2) { return 0; } if (s1 == NULL) { return -1; } if (s2 == NULL) { return 1; } return strcmp(s1, s2); } int xmlStrEqual(const char* s1, const char* s2) { if (s1 == s2) { return 1; } if (s1 == NULL) { return 0; } if (s2 == NULL) { return 0; } if (strcmp(s1, s2) == 0) { return 1; } return 0; } int xmlStrcasecmp(const char* s1, const char* s2) { if (s1 == s2) { return 0; } if (s1 == NULL) { return -1; } if (s2 == NULL) { return 1; } return strcasecmp(s1, s2); } int xmlStrncasecmp(const char* s1, const char* s2, int len) { if (len <= 0) { return 0; } if (s1 == s2) { return 0; } if (s1 == NULL) { return -1; } if (s2 == NULL) { return 1; } return strncasecmp(s1, s2, (size_t)len); } const char* xmlStrcasestr(const char* haystack, const char* needle) { if (haystack == NULL) { return NULL; } if (needle == NULL) { return NULL; } return strcasestr(haystack, needle); } /* * Samba wrappers */ int memcmp_const_time(const void* s1, const void* s2, size_t n) { return memcmp(s1, s2, n); } bool strcsequal(const void* s1, const void* s2) { if (s1 == s2) { return true; } if (!s1 || !s2) { return false; } return (strcmp(s1, s2) == 0); } /* Init code to open init the library. */ __attribute__((constructor)) void __compcov_init(void) { if (getenv("AFL_QEMU_COMPCOV_DEBUG") != NULL) debug_fd = open("compcov.debug", O_WRONLY | O_CREAT | O_TRUNC | O_SYNC, 0644); __compcov_load(); }