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Don't use a secdiscardable file for keys encrypted by SP

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Storage keys that are encrypted by the user's synthetic password don't
need to be securely deletable by vold, since secure deletion is already
implemented at a higher level: the synthetic password protectors managed
by LockSettingsService.  Therefore, remove the use of the secdiscardable
file by vold in this case to improve performance.

Bug: 232452368
Bug: 251131631
Bug: 251147505
Change-Id: I847d6cd3b289dbeb1ca2760d6e261a78c179cad0
This commit is contained in:
Eric Biggers 2022-10-07 05:19:50 +00:00
parent 03ad91c3c2
commit 08f4bdfe98
2 changed files with 17 additions and 8 deletions
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23
KeyStorage.cpp
View file

@ -191,9 +191,13 @@ bool createSecdiscardable(const std::string& filename, std::string* hash) {
}
bool readSecdiscardable(const std::string& filename, std::string* hash) {
std::string secdiscardable;
if (!readFileToString(filename, &secdiscardable)) return false;
hashWithPrefix(kHashPrefix_secdiscardable, secdiscardable, hash);
if (pathExists(filename)) {
std::string secdiscardable;
if (!readFileToString(filename, &secdiscardable)) return false;
hashWithPrefix(kHashPrefix_secdiscardable, secdiscardable, hash);
} else {
*hash = "";
}
return true;
}
@ -563,9 +567,12 @@ static bool decryptWithoutKeystore(const std::string& preKey, const std::string&
// Creates a directory at the given path |dir| and stores |key| in it, in such a
// way that it can only be retrieved via Keystore (if no secret is given in
// |auth|) or with the given secret (if a secret is given in |auth|), and can be
// securely deleted. If a storage binding seed has been set, then the storage
// binding seed will be required to retrieve the key as well.
// |auth|) or with the given secret (if a secret is given in |auth|). In the
// former case, an attempt is made to make the key securely deletable. In the
// latter case, secure deletion is expected to be handled at a higher level.
//
// If a storage binding seed has been set, then the storage binding seed will be
// required to retrieve the key as well.
static bool storeKey(const std::string& dir, const KeyAuthentication& auth, const KeyBuffer& key) {
if (TEMP_FAILURE_RETRY(mkdir(dir.c_str(), 0700)) == -1) {
PLOG(ERROR) << "key mkdir " << dir;
@ -573,7 +580,9 @@ static bool storeKey(const std::string& dir, const KeyAuthentication& auth, cons
}
if (!writeStringToFile(kCurrentVersion, dir + "/" + kFn_version)) return false;
std::string secdiscardable_hash;
if (!createSecdiscardable(dir + "/" + kFn_secdiscardable, &secdiscardable_hash)) return false;
if (auth.usesKeystore() &&
!createSecdiscardable(dir + "/" + kFn_secdiscardable, &secdiscardable_hash))
return false;
std::string stretching = getStretching(auth);
if (!writeStringToFile(stretching, dir + "/" + kFn_stretching)) return false;
std::string appId;

2
secdiscard.cpp
View file

@ -97,7 +97,7 @@ int main(int argc, const char* const argv[]) {
TEMP_FAILURE_RETRY(open(target.c_str(), O_WRONLY | O_CLOEXEC, 0)));
if (fd == -1) {
LOG(ERROR) << "Secure discard open failed for: " << target;
return 0;
continue;
}
__u32 set = 1;
ioctl(fd, F2FS_IOC_SET_PIN_FILE, &set);