--- /dev/null
+/*
+ * 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;
+}
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