/*
american fuzzy lop - extract tokens passed to strcmp / memcmp
-------------------------------------------------------------
Written and maintained by Michal Zalewski <[email protected]>
Copyright 2016 Google Inc. 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 automatically extract tokens.
See README.tokencap for more info.
*/
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include "../types.h"
#include "../config.h"
#ifndef __linux__
# error "Sorry, this library is Linux-specific for now!"
#endif /* !__linux__ */
/* Mapping data and such */
#define MAX_MAPPINGS 1024
static struct mapping {
void *st, *en;
} __tokencap_ro[MAX_MAPPINGS];
static u32 __tokencap_ro_cnt;
static u8 __tokencap_ro_loaded;
static FILE* __tokencap_out_file;
/* Identify read-only regions in memory. Only parameters that fall into these
ranges are worth dumping when passed to strcmp() and so on. Read-write
regions are far more likely to contain user input instead. */
static void __tokencap_load_mappings(void) {
u8 buf[MAX_LINE];
FILE* f = fopen("/proc/self/maps", "r");
__tokencap_ro_loaded = 1;
if (!f) return;
while (fgets(buf, MAX_LINE, f)) {
u8 rf, wf;
void* st, *en;
if (sscanf(buf, "%p-%p %c%c", &st, &en, &rf, &wf) != 4) continue;
if (wf == 'w' || rf != 'r') continue;
__tokencap_ro[__tokencap_ro_cnt].st = (void*)st;
__tokencap_ro[__tokencap_ro_cnt].en = (void*)en;
if (++__tokencap_ro_cnt == MAX_MAPPINGS) break;
}
fclose(f);
}
/* Check an address against the list of read-only mappings. */
static u8 __tokencap_is_ro(const void* ptr) {
u32 i;
if (!__tokencap_ro_loaded) __tokencap_load_mappings();
for (i = 0; i < __tokencap_ro_cnt; i++)
if (ptr >= __tokencap_ro[i].st && ptr <= __tokencap_ro[i].en) return 1;
return 0;
}
/* Dump an interesting token to output file, quoting and escaping it
properly. */
static void __tokencap_dump(const u8* ptr, size_t len, u8 is_text) {
u8 buf[MAX_AUTO_EXTRA * 4 + 1];
u32 i;
u32 pos = 0;
if (len < MIN_AUTO_EXTRA || len > MAX_AUTO_EXTRA || !__tokencap_out_file)
return;
for (i = 0; i < len; i++) {
if (is_text && !ptr[i]) break;
switch (ptr[i]) {
case 0 ... 31:
case 127 ... 255:
case '\"':
case '\\':
sprintf(buf + pos, "\\x%02x", ptr[i]);
pos += 4;
break;
default:
buf[pos++] = ptr[i];
}
}
buf[pos] = 0;
fprintf(__tokencap_out_file, "\"%s\"\n", buf);
}
/* 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) {
if (__tokencap_is_ro(str1)) __tokencap_dump(str1, strlen(str1), 1);
if (__tokencap_is_ro(str2)) __tokencap_dump(str2, strlen(str2), 1);
while (1) {
unsigned char c1 = *str1, c2 = *str2;
if (c1 != c2) return (c1 > c2) ? 1 : -1;
if (!c1) return 0;
str1++; str2++;
}
}
#undef strncmp
int strncmp(const char* str1, const char* str2, size_t len) {
if (__tokencap_is_ro(str1)) __tokencap_dump(str1, len, 1);
if (__tokencap_is_ro(str2)) __tokencap_dump(str2, len, 1);
while (len--) {
unsigned char c1 = *str1, c2 = *str2;
if (!c1) return 0;
if (c1 != c2) return (c1 > c2) ? 1 : -1;
str1++; str2++;
}
return 0;
}
#undef strcasecmp
int strcasecmp(const char* str1, const char* str2) {
if (__tokencap_is_ro(str1)) __tokencap_dump(str1, strlen(str1), 1);
if (__tokencap_is_ro(str2)) __tokencap_dump(str2, strlen(str2), 1);
while (1) {
unsigned char c1 = tolower(*str1), c2 = tolower(*str2);
if (c1 != c2) return (c1 > c2) ? 1 : -1;
if (!c1) return 0;
str1++; str2++;
}
}
#undef strncasecmp
int strncasecmp(const char* str1, const char* str2, size_t len) {
if (__tokencap_is_ro(str1)) __tokencap_dump(str1, len, 1);
if (__tokencap_is_ro(str2)) __tokencap_dump(str2, len, 1);
while (len--) {
unsigned char c1 = tolower(*str1), c2 = tolower(*str2);
if (!c1) return 0;
if (c1 != c2) return (c1 > c2) ? 1 : -1;
str1++; str2++;
}
return 0;
}
#undef memcmp
int memcmp(const void* mem1, const void* mem2, size_t len) {
if (__tokencap_is_ro(mem1)) __tokencap_dump(mem1, len, 0);
if (__tokencap_is_ro(mem2)) __tokencap_dump(mem2, len, 0);
while (len--) {
unsigned char c1 = *(const char*)mem1, c2 = *(const char*)mem2;
if (c1 != c2) return (c1 > c2) ? 1 : -1;
mem1++; mem2++;
}
return 0;
}
#undef strstr
char* strstr(const char* haystack, const char* needle) {
if (__tokencap_is_ro(haystack))
__tokencap_dump(haystack, strlen(haystack), 1);
if (__tokencap_is_ro(needle))
__tokencap_dump(needle, strlen(needle), 1);
do {
const char* n = needle;
const char* h = haystack;
while(*n && *h && *n == *h) n++, h++;
if(!*n) return (char*)haystack;
} while (*(haystack++));
return 0;
}
#undef strcasestr
char* strcasestr(const char* haystack, const char* needle) {
if (__tokencap_is_ro(haystack))
__tokencap_dump(haystack, strlen(haystack), 1);
if (__tokencap_is_ro(needle))
__tokencap_dump(needle, strlen(needle), 1);
do {
const char* n = needle;
const char* h = haystack;
while(*n && *h && tolower(*n) == tolower(*h)) n++, h++;
if(!*n) return (char*)haystack;
} while(*(haystack++));
return 0;
}
/* Init code to open the output file (or default to stderr). */
__attribute__((constructor)) void __tokencap_init(void) {
u8* fn = getenv("AFL_TOKEN_FILE");
if (fn) __tokencap_out_file = fopen(fn, "a");
if (!__tokencap_out_file) __tokencap_out_file = stderr;
}
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