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Merge "KeyUtil: use static local variable in isFsKeyringSupported()"

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Eric Biggers 2020-07-17 01:20:43 +00:00 committed by Gerrit Code Review
commit 256b23b1c5
1 changed files with 28 additions and 31 deletions
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59
KeyUtil.cpp
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@ -63,40 +63,37 @@ bool generateStorageKey(const KeyGeneration& gen, KeyBuffer* key) {
}
}
static bool isFsKeyringSupportedImpl() {
android::base::unique_fd fd(open("/data", O_RDONLY | O_DIRECTORY | O_CLOEXEC));
// FS_IOC_ADD_ENCRYPTION_KEY with a NULL argument will fail with ENOTTY if
// the ioctl isn't supported. Otherwise it will fail with another error
// code such as EFAULT.
//
// Note that there's no need to check for FS_IOC_REMOVE_ENCRYPTION_KEY,
// since it's guaranteed to be available if FS_IOC_ADD_ENCRYPTION_KEY is.
// There's also no need to check for support on external volumes separately
// from /data, since either the kernel supports the ioctls on all
// fscrypt-capable filesystems or it doesn't.
errno = 0;
(void)ioctl(fd, FS_IOC_ADD_ENCRYPTION_KEY, NULL);
if (errno == ENOTTY) {
LOG(INFO) << "Kernel doesn't support FS_IOC_ADD_ENCRYPTION_KEY. Falling back to "
"session keyring";
return false;
}
if (errno != EFAULT) {
PLOG(WARNING) << "Unexpected error from FS_IOC_ADD_ENCRYPTION_KEY";
}
LOG(DEBUG) << "Detected support for FS_IOC_ADD_ENCRYPTION_KEY";
android::base::SetProperty("ro.crypto.uses_fs_ioc_add_encryption_key", "true");
return true;
}
// Return true if the kernel supports the ioctls to add/remove fscrypt keys
// directly to/from the filesystem.
bool isFsKeyringSupported(void) {
static bool initialized = false;
static bool supported;
if (!initialized) {
android::base::unique_fd fd(open("/data", O_RDONLY | O_DIRECTORY | O_CLOEXEC));
// FS_IOC_ADD_ENCRYPTION_KEY with a NULL argument will fail with ENOTTY
// if the ioctl isn't supported. Otherwise it will fail with another
// error code such as EFAULT.
errno = 0;
(void)ioctl(fd, FS_IOC_ADD_ENCRYPTION_KEY, NULL);
if (errno == ENOTTY) {
LOG(INFO) << "Kernel doesn't support FS_IOC_ADD_ENCRYPTION_KEY. Falling back to "
"session keyring";
supported = false;
} else {
if (errno != EFAULT) {
PLOG(WARNING) << "Unexpected error from FS_IOC_ADD_ENCRYPTION_KEY";
}
LOG(DEBUG) << "Detected support for FS_IOC_ADD_ENCRYPTION_KEY";
supported = true;
android::base::SetProperty("ro.crypto.uses_fs_ioc_add_encryption_key", "true");
}
// There's no need to check for FS_IOC_REMOVE_ENCRYPTION_KEY, since it's
// guaranteed to be available if FS_IOC_ADD_ENCRYPTION_KEY is. There's
// also no need to check for support on external volumes separately from
// /data, since either the kernel supports the ioctls on all
// fscrypt-capable filesystems or it doesn't.
initialized = true;
}
static bool supported = isFsKeyringSupportedImpl();
return supported;
}