Merge "secdiscard.cpp: Use getmntent and my newfound C++ knowledge."
diff --git a/AutoCloseFD.h b/AutoCloseFD.h
new file mode 100644
index 0000000..f9d7c86
--- /dev/null
+++ b/AutoCloseFD.h
@@ -0,0 +1,48 @@
+/*
+ * 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 <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+// File descriptor which is automatically closed when this object is destroyed.
+// Cannot be copied, since that would cause double-closes.
+class AutoCloseFD {
+public:
+ AutoCloseFD(const char *path, int flags = O_RDONLY, int mode = 0):
+ fd{TEMP_FAILURE_RETRY(open(path, flags | O_CLOEXEC, mode))} {}
+ AutoCloseFD(const std::string &path, int flags = O_RDONLY, int mode = 0):
+ AutoCloseFD(path.c_str(), flags, mode) {}
+ ~AutoCloseFD() {
+ if (fd != -1) {
+ int preserve_errno = errno;
+ if (close(fd) == -1) {
+ SLOGE("close(2) failed: %s", strerror(errno));
+ };
+ errno = preserve_errno;
+ }
+ }
+ AutoCloseFD(const AutoCloseFD&) = delete;
+ AutoCloseFD& operator=(const AutoCloseFD&) = delete;
+ explicit operator bool() {return fd != -1;}
+ int get() const {return fd;}
+private:
+ const int fd;
+};
+
diff --git a/secdiscard.cpp b/secdiscard.cpp
index 3f4ab2e..a750043 100644
--- a/secdiscard.cpp
+++ b/secdiscard.cpp
@@ -24,69 +24,73 @@
#include <fcntl.h>
#include <linux/fs.h>
#include <linux/fiemap.h>
+#include <mntent.h>
#define LOG_TAG "secdiscard"
#include "cutils/log.h"
+#include <AutoCloseFD.h>
+
+namespace {
// Deliberately limit ourselves to wiping small files.
-#define MAX_WIPE_LENGTH 4096
-#define INIT_BUFFER_SIZE 2048
+constexpr uint64_t max_wipe_length = 4096;
-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);
+void usage(const char *progname);
+int secdiscard_path(const std::string &path);
+int path_device_range(const std::string &path, uint64_t range[2]);
+std::string block_device_for_path(const std::string &path);
+}
-int main(int argc, char **argv) {
+int main(int argc, const char * const 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);
+ secdiscard_path(argv[1]);
if (unlink(argv[1]) != 0 && errno != ENOENT) {
SLOGE("Unable to delete %s: %s",
argv[1], strerror(errno));
return -1;
}
+ SLOGD("Discarded %s", argv[1]);
return 0;
}
-static void usage(char *progname) {
+namespace {
+
+void usage(const 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) {
+int secdiscard_path(const std::string &path) {
uint64_t range[2];
- if (file_device_range(path, range) < 0) {
- return;
+ if (path_device_range(path, range) == -1) {
+ return -1;
}
- int fs_fd = open_block_device_for_path(path);
- if (fs_fd < 0) {
- return;
+ auto block_device = block_device_for_path(path);
+ if (block_device.empty()) {
+ return -1;
}
- if (ioctl(fs_fd, BLKSECDISCARD, range) != 0) {
+ AutoCloseFD fs_fd(block_device, O_RDWR | O_LARGEFILE);
+ if (!fs_fd) {
+ SLOGE("Failed to open device %s: %s", block_device.c_str(), strerror(errno));
+ return -1;
+ }
+ if (ioctl(fs_fd.get(), BLKSECDISCARD, range) == -1) {
SLOGE("Unable to BLKSECDISCARD %s: %s", path.c_str(), strerror(errno));
- close(fs_fd);
- return;
+ return -1;
}
- close(fs_fd);
- SLOGD("Discarded %s", path.c_str());
+ return 0;
}
// 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 path_device_range(const std::string &path, uint64_t range[2])
{
- int fd = open(path.c_str(), O_RDONLY | O_CLOEXEC);
- if (fd < 0) {
+ AutoCloseFD fd(path);
+ if (!fd) {
if (errno == ENOENT) {
SLOGD("Unable to open %s: %s", path.c_str(), strerror(errno));
} else {
@@ -102,12 +106,10 @@
fiemap->fm_flags = 0;
fiemap->fm_extent_count = 1;
fiemap->fm_mapped_extents = 0;
- if (ioctl(fd, FS_IOC_FIEMAP, fiemap) != 0) {
+ if (ioctl(fd.get(), 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;
@@ -122,7 +124,7 @@
SLOGE("Extent has unexpected flags %ulx: %s", extent->fe_flags, path.c_str());
return -1;
}
- if (extent->fe_length > MAX_WIPE_LENGTH) {
+ if (extent->fe_length > max_wipe_length) {
SLOGE("Extent too big, %llu bytes in %s", extent->fe_length, path.c_str());
return -1;
}
@@ -131,106 +133,33 @@
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)
+// Given a file path, look for the corresponding block device in /proc/mount
+std::string 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::unique_ptr<FILE, int(*)(FILE*)> mnts(setmntent("/proc/mounts", "re"), endmntent);
+ if (!mnts) {
+ SLOGE("Unable to open /proc/mounts: %s", strerror(errno));
+ return "";
}
- std::string block_device;
- if (find_block_device_for_path(mounts, path, block_device) < 0) {
- return -1;
+ std::string result;
+ size_t best_length = 0;
+ struct mntent *mnt; // getmntent returns a thread local, so it's safe.
+ while ((mnt = getmntent(mnts.get())) != nullptr) {
+ auto l = strlen(mnt->mnt_dir);
+ if (l > best_length &&
+ path.size() > l &&
+ path[l] == '/' &&
+ path.compare(0, l, mnt->mnt_dir) == 0) {
+ result = mnt->mnt_fsname;
+ best_length = l;
+ }
}
- 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;
+ if (result.empty()) {
+ SLOGE("Didn't find a mountpoint to match path %s", path.c_str());
+ return "";
}
- return res;
+ SLOGD("For path %s block device is %s", path.c_str(), result.c_str());
+ return result;
}
-// 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 the contents of /proc/mounts
-// for the mount point of a particular file by prefix matching
-// and return the corresponding block device.
-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()) {
- auto bad_line = std::string(line_begin, line_end);
- SLOGE("Unable to parse line in %s: %s", path.c_str(), bad_line.c_str());
- return -1;
- }
- if (best_prefix == 0) {
- SLOGE("No prefix found for path: %s", path.c_str());
- return -1;
- }
- return 0;
}