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/*
* Copyright (C) 2016 The Android Open Source Project
*
* 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
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "aslr_test.h"
unsigned int get_mmap_rnd_bits(bool compat) {
std::string path;
if (compat)
path = PROCFS_COMPAT_PATH;
else
path = PROCFS_PATH;
std::ifstream bi_file(path);
if (!bi_file)
return false;
std::string str_rec;
bi_file >> str_rec;
return stoi(str_rec);
}
bool set_mmap_rnd_bits(unsigned int new_val, bool compat) {
std::string path;
if (compat)
path = "/proc/sys/vm/mmap_rnd_compat_bits";
else
path = "/proc/sys/vm/mmap_rnd_bits";
std::ofstream bo_file(path, std::ios::out);
if (!bo_file)
return false;
std::string str_val = std::to_string(new_val);
bo_file << str_val << std::flush;
bo_file.close();
// check to make sure it was recorded
std::ifstream bi_file(path);
if (!bi_file)
return false;
std::string str_rec;
bi_file >> str_rec;
bi_file.close();
if (str_val.compare(str_rec) != 0)
return false;
return true;
}
std::string scrape_addr(const char *exec_name, const char *lib_match) {
pid_t pid;
int fd[2];
char buff[MAX_ADDR_LEN];
int len, status;
if(pipe(fd)) {
std::cerr << "Error creating pipe:" << strerror(errno) << "\n";
return std::string();
}
if ((pid = fork()) < 0) {
std::cerr << "Error creating new process: " << strerror(errno) << "\n";
close(fd[0]);
close(fd[1]);
return std::string();
} else if (pid > 0) {
// parent
close(fd[1]);
wait(&status);
if (status == -1) {
std::cerr << "Unable to find starting address of mmapp'd libc. Aborting.\n";
close(fd[0]);
return std::string();
}
len = read(fd[0], buff, MAX_ADDR_LEN - 1);
if (len < 0) {
std::cerr << "Error reading pipe from child: " << strerror(errno) << "\n";
close(fd[0]);
return std::string();
}
buff[len] = '\0';
close(fd[0]);
} else {
// child, dup 'n' exec
close(fd[0]);
if(dup2(fd[1], STDOUT_FILENO) != STDOUT_FILENO) {
std::cerr << "Error dup'n pipe to STDOUT of child: " << strerror(errno) << "\n";
close(fd[1]);
return std::string();
}
if(execlp(exec_name, exec_name, lib_match, (char *) NULL)) {
std::cerr << "Error exec'ing mmap_scraper: " << strerror(errno) << "\n";
close(fd[1]);
return std::string();
}
}
return std::string(buff, strlen(buff));
}
unsigned int calc_mmap_entropy(const char *exec_name, const char *lib_match, size_t samp_sz) {
uint64_t min_addr = 0, max_addr = 0;
std::unordered_set<uint64_t> addrs = { };
// get our first value
uint64_t addr = min_addr = max_addr = std::stoll(scrape_addr(exec_name, lib_match), 0, 16);
addrs.insert(addr);
for (unsigned int i = 0; i < samp_sz - 1; ++i) {
std::string addr_str = scrape_addr(exec_name, lib_match);
if (addr_str.empty())
return 0;
addr = std::stoll(addr_str, 0, 16);
if (addr < min_addr)
min_addr = addr;
if (addr >= max_addr)
max_addr = addr;
addrs.insert(addr);
}
if (addrs.size() < (samp_sz >> 1)) {
std::cerr << "> 50% collisions in mmap addresses, entropy appears to be rigged!";
return 0;
}
unsigned int e_bits = (int) (std::ceil(std::log2(max_addr - min_addr)) - std::log2(getpagesize()));
return e_bits;
}
const char *AslrMmapTest::path;
const char *AslrMmapTest::lib;
unsigned int AslrMmapTest::def, AslrMmapTest::min, AslrMmapTest::max;
bool AslrMmapTest::compat = false, AslrMmapTest::user32 = false;
unsigned int AslrMmapTest::def_cmpt, AslrMmapTest::min_cmpt, AslrMmapTest::max_cmpt;
void AslrMmapTest::SetUpTestCase() {
/* set up per-arch values */
#if defined(__x86_64__)
def = 32;
min = 28;
max = 32;
path = SCRAPE_PATH_64;
lib = SCRAPE_LIB_64;
compat = true;
def_cmpt = 16;
min_cmpt = 8;
max_cmpt = 16;
#elif defined(__i386__)
def = 16;
min = 8;
max = 16;
path = SCRAPE_PATH_32;
lib = SCRAPE_LIB_32;
if (!access(PROCFS_COMPAT_PATH, F_OK)) {
// running 32 bit userspace over 64-bit kernel
user32 = true;
def_cmpt = 16;
min_cmpt = 8;
max_cmpt = 16;
}
#elif defined(__aarch64__)
unsigned int pgbits = std::log2(getpagesize());
def = 24;
min = 18 - (pgbits - 12);
max = 24;
path = SCRAPE_PATH_64;
lib = SCRAPE_LIB_64;
compat = true;
def_cmpt = 16;
min_cmpt = 11 - (pgbits - 12);
max_cmpt = 16;
#elif defined(__arm__)
unsigned int pgbits = std::log2(getpagesize());
def = 16;
min = 8;
max = 16;
path = SCRAPE_PATH_32;
lib = SCRAPE_LIB_32;
if (!access(PROCFS_COMPAT_PATH, F_OK)) {
// running 32 bit userspace over 64-bit kernel
user32 = true;
def_cmpt = 16;
min_cmpt = 11 - (pgbits - 12);;
max_cmpt = 16;
}
#endif
}
void AslrMmapTest::TearDown() {
if (!user32)
set_mmap_rnd_bits(def, false);
if (user32 || compat)
set_mmap_rnd_bits(def_cmpt, true);
}
/* run tests only if on supported arch */
#if defined(__x86_64__) || defined(__i386__) || defined(__aarch64__) || defined(__arm__)
TEST_F(AslrMmapTest, entropy_min_def) {
if (user32) {
// running 32-bit userspace on 64-bit kernel, only compat used.
return;
} else {
EXPECT_GE(def, calc_mmap_entropy(path, lib, 16));
}
}
TEST_F(AslrMmapTest, entropy_min_cmpt_def) {
if (compat || user32) {
EXPECT_GE(def_cmpt, calc_mmap_entropy(SCRAPE_PATH_32, SCRAPE_LIB_32, 16));
}
}
#endif /* supported arch */
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