240 lines
7.9 KiB
C++
240 lines
7.9 KiB
C++
/*
|
|
* Copyright (C) 2015 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 <string>
|
|
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <errno.h>
|
|
#include <sys/types.h>
|
|
#include <sys/stat.h>
|
|
#include <fcntl.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/fiemap.h>
|
|
|
|
#define LOG_TAG "secdiscard"
|
|
#include "cutils/log.h"
|
|
|
|
// Deliberately limit ourselves to wiping small files.
|
|
#define MAX_WIPE_LENGTH 4096
|
|
#define INIT_BUFFER_SIZE 2048
|
|
|
|
static void usage(char *progname);
|
|
static void destroy_key(const std::string &path);
|
|
static int file_device_range(const std::string &path, uint64_t range[2]);
|
|
static int open_block_device_for_path(const std::string &path);
|
|
static int read_file_as_string_atomically(const std::string &path, std::string &contents);
|
|
static int find_block_device_for_path(
|
|
const std::string &mounts,
|
|
const std::string &path,
|
|
std::string &block_device);
|
|
|
|
int main(int argc, char **argv) {
|
|
if (argc != 2 || argv[1][0] != '/') {
|
|
usage(argv[0]);
|
|
return -1;
|
|
}
|
|
SLOGD("Running: %s %s", argv[0], argv[1]);
|
|
std::string target(argv[1]);
|
|
destroy_key(target);
|
|
if (unlink(argv[1]) != 0 && errno != ENOENT) {
|
|
SLOGE("Unable to delete %s: %s",
|
|
argv[1], strerror(errno));
|
|
return -1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static void usage(char *progname) {
|
|
fprintf(stderr, "Usage: %s <absolute path>\n", progname);
|
|
}
|
|
|
|
// BLKSECDISCARD all content in "path", if it's small enough.
|
|
static void destroy_key(const std::string &path) {
|
|
uint64_t range[2];
|
|
if (file_device_range(path, range) < 0) {
|
|
return;
|
|
}
|
|
int fs_fd = open_block_device_for_path(path);
|
|
if (fs_fd < 0) {
|
|
return;
|
|
}
|
|
if (ioctl(fs_fd, BLKSECDISCARD, range) != 0) {
|
|
SLOGE("Unable to BLKSECDISCARD %s: %s", path.c_str(), strerror(errno));
|
|
close(fs_fd);
|
|
return;
|
|
}
|
|
close(fs_fd);
|
|
SLOGD("Discarded %s", path.c_str());
|
|
}
|
|
|
|
// Find a short range that completely covers the file.
|
|
// If there isn't one, return -1, otherwise 0.
|
|
static int file_device_range(const std::string &path, uint64_t range[2])
|
|
{
|
|
int fd = open(path.c_str(), O_RDONLY | O_CLOEXEC);
|
|
if (fd < 0) {
|
|
if (errno == ENOENT) {
|
|
SLOGD("Unable to open %s: %s", path.c_str(), strerror(errno));
|
|
} else {
|
|
SLOGE("Unable to open %s: %s", path.c_str(), strerror(errno));
|
|
}
|
|
return -1;
|
|
}
|
|
alignas(struct fiemap) char fiemap_buffer[offsetof(struct fiemap, fm_extents[1])];
|
|
memset(fiemap_buffer, 0, sizeof(fiemap_buffer));
|
|
struct fiemap *fiemap = (struct fiemap *)fiemap_buffer;
|
|
fiemap->fm_start = 0;
|
|
fiemap->fm_length = UINT64_MAX;
|
|
fiemap->fm_flags = 0;
|
|
fiemap->fm_extent_count = 1;
|
|
fiemap->fm_mapped_extents = 0;
|
|
if (ioctl(fd, FS_IOC_FIEMAP, fiemap) != 0) {
|
|
SLOGE("Unable to FIEMAP %s: %s", path.c_str(), strerror(errno));
|
|
close(fd);
|
|
return -1;
|
|
}
|
|
close(fd);
|
|
if (fiemap->fm_mapped_extents != 1) {
|
|
SLOGE("Expecting one extent, got %d in %s", fiemap->fm_mapped_extents, path.c_str());
|
|
return -1;
|
|
}
|
|
struct fiemap_extent *extent = &fiemap->fm_extents[0];
|
|
if (!(extent->fe_flags & FIEMAP_EXTENT_LAST)) {
|
|
SLOGE("First extent was not the last in %s", path.c_str());
|
|
return -1;
|
|
}
|
|
if (extent->fe_flags &
|
|
(FIEMAP_EXTENT_UNKNOWN | FIEMAP_EXTENT_DELALLOC | FIEMAP_EXTENT_NOT_ALIGNED)) {
|
|
SLOGE("Extent has unexpected flags %ulx: %s", extent->fe_flags, path.c_str());
|
|
return -1;
|
|
}
|
|
if (extent->fe_length > MAX_WIPE_LENGTH) {
|
|
SLOGE("Extent too big, %llu bytes in %s", extent->fe_length, path.c_str());
|
|
return -1;
|
|
}
|
|
range[0] = extent->fe_physical;
|
|
range[1] = extent->fe_length;
|
|
return 0;
|
|
}
|
|
|
|
// Given a file path, look for the corresponding
|
|
// block device in /proc/mounts and open it.
|
|
static int open_block_device_for_path(const std::string &path)
|
|
{
|
|
std::string mountsfile("/proc/mounts");
|
|
std::string mounts;
|
|
if (read_file_as_string_atomically(mountsfile, mounts) < 0) {
|
|
return -1;
|
|
}
|
|
std::string block_device;
|
|
if (find_block_device_for_path(mounts, path, block_device) < 0) {
|
|
return -1;
|
|
}
|
|
SLOGD("For path %s block device is %s", path.c_str(), block_device.c_str());
|
|
int res = open(block_device.c_str(), O_RDWR | O_LARGEFILE | O_CLOEXEC);
|
|
if (res < 0) {
|
|
SLOGE("Failed to open device %s: %s", block_device.c_str(), strerror(errno));
|
|
return -1;
|
|
}
|
|
return res;
|
|
}
|
|
|
|
// Read a file into a buffer in a single gulp, for atomicity.
|
|
// Null-terminate the buffer.
|
|
// Retry until the buffer is big enough.
|
|
static int read_file_as_string_atomically(const std::string &path, std::string &contents)
|
|
{
|
|
ssize_t buffer_size = INIT_BUFFER_SIZE;
|
|
while (true) {
|
|
int fd = open(path.c_str(), O_RDONLY | O_CLOEXEC);
|
|
if (fd < 0) {
|
|
SLOGE("Failed to open %s: %s", path.c_str(), strerror(errno));
|
|
return -1;
|
|
}
|
|
contents.resize(buffer_size);
|
|
ssize_t read_size = read(fd, &contents[0], buffer_size);
|
|
if (read_size < 0) {
|
|
SLOGE("Failed to read from %s: %s", path.c_str(), strerror(errno));
|
|
close(fd);
|
|
return -1;
|
|
}
|
|
close(fd);
|
|
if (read_size < buffer_size) {
|
|
contents.resize(read_size);
|
|
return 0;
|
|
}
|
|
SLOGD("%s too big for buffer of size %zu", path.c_str(), buffer_size);
|
|
buffer_size <<= 1;
|
|
}
|
|
}
|
|
|
|
// Search a string representing result from /proc/mounts
|
|
// for the mount point of a particular file by prefix matching
|
|
// and return the corresponding block device as a
|
|
// pointer into the mounts string.
|
|
// This destroys the mounts string.
|
|
static int find_block_device_for_path(
|
|
const std::string &mounts,
|
|
const std::string &path,
|
|
std::string &block_device)
|
|
{
|
|
auto line_begin = mounts.begin();
|
|
size_t best_prefix = 0;
|
|
std::string::const_iterator line_end;
|
|
while (line_begin != mounts.end()) {
|
|
line_end = std::find(line_begin, mounts.end(), '\n');
|
|
if (line_end == mounts.end()) {
|
|
break;
|
|
}
|
|
auto device_end = std::find(line_begin, line_end, ' ');;
|
|
if (device_end == line_end) {
|
|
break;
|
|
}
|
|
auto mountpoint_begin = device_end +1;
|
|
auto mountpoint_end = std::find(mountpoint_begin, line_end, ' ');
|
|
if (mountpoint_end == line_end) {
|
|
break;
|
|
}
|
|
if (std::find(line_begin, mountpoint_end, '\\') != mountpoint_end) {
|
|
// We don't correctly handle escape sequences
|
|
// and we don't expect to encounter any
|
|
// so fail if we do.
|
|
break;
|
|
}
|
|
size_t mountpoint_len = mountpoint_end - mountpoint_begin;
|
|
if (mountpoint_len > best_prefix &&
|
|
mountpoint_len < path.length() &&
|
|
path[mountpoint_len] == '/' &&
|
|
std::equal(mountpoint_begin, mountpoint_end, path.begin())) {
|
|
block_device = std::string(line_begin, device_end);
|
|
best_prefix = mountpoint_len;
|
|
}
|
|
line_begin = line_end +1;
|
|
}
|
|
// All of the "break"s above are fatal parse errors.
|
|
if (line_begin != mounts.end()) {
|
|
SLOGE("Unable to parse line in %s: %s",
|
|
path.c_str(), std::string(line_begin, line_end).c_str());
|
|
return -1;
|
|
}
|
|
if (best_prefix == 0) {
|
|
SLOGE("No prefix found for path: %s", path.c_str());
|
|
return -1;
|
|
}
|
|
return 0;
|
|
}
|