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Require the auth token for decryption.

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A bug meant that the auth token wasn't being used; it turns out that
in order to use it we need to do things slightly differently.

Bug: 27496553
Change-Id: I0f0ab77fed31b92a79eba4acf488cb098691b4be
This commit is contained in:
Paul Crowley 2016-03-04 14:07:05 -08:00
parent d9b9295b8c
commit 320e5e15b6
1 changed files with 55 additions and 42 deletions
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97
KeyStorage.cpp
View file

@ -35,6 +35,8 @@
#include <cutils/properties.h>
#include <hardware/hw_auth_token.h>
#include <keymaster/authorization_set.h>
extern "C" {
@ -94,32 +96,54 @@ static std::string hashSecdiscardable(const std::string &secdiscardable) {
}
static bool generateKeymasterKey(Keymaster &keymaster,
const keymaster::AuthorizationSet &extraParams,
const KeyAuthentication &auth, const std::string &appId,
std::string &key) {
auto params = keymaster::AuthorizationSetBuilder()
auto paramBuilder = keymaster::AuthorizationSetBuilder()
.AesEncryptionKey(AES_KEY_BYTES * 8)
.Authorization(keymaster::TAG_BLOCK_MODE, KM_MODE_GCM)
.Authorization(keymaster::TAG_MIN_MAC_LENGTH, GCM_MAC_BYTES * 8)
.Authorization(keymaster::TAG_PADDING, KM_PAD_NONE)
.Authorization(keymaster::TAG_NO_AUTH_REQUIRED) // FIXME integrate with gatekeeper
.build();
params.push_back(extraParams);
return keymaster.generateKey(params, key);
.Authorization(keymaster::TAG_PADDING, KM_PAD_NONE);
addStringParam(paramBuilder, keymaster::TAG_APPLICATION_ID, appId);
if (auth.token.empty()) {
LOG(DEBUG) << "Creating key that doesn't need auth token";
paramBuilder.Authorization(keymaster::TAG_NO_AUTH_REQUIRED);
} else {
LOG(DEBUG) << "Auth token required for key";
if (auth.token.size() != sizeof(hw_auth_token_t)) {
LOG(ERROR) << "Auth token should be " << sizeof(hw_auth_token_t) << " bytes, was "
<< auth.token.size() << " bytes";
return false;
}
const hw_auth_token_t *at = reinterpret_cast<const hw_auth_token_t *>(auth.token.data());
paramBuilder.Authorization(keymaster::TAG_USER_SECURE_ID, at->user_id);
paramBuilder.Authorization(keymaster::TAG_USER_AUTH_TYPE, HW_AUTH_PASSWORD);
paramBuilder.Authorization(keymaster::TAG_AUTH_TIMEOUT, 5);
}
return keymaster.generateKey(paramBuilder.build(), key);
}
static keymaster::AuthorizationSetBuilder beginParams(
const KeyAuthentication &auth, const std::string &appId) {
auto paramBuilder = keymaster::AuthorizationSetBuilder()
.Authorization(keymaster::TAG_BLOCK_MODE, KM_MODE_GCM)
.Authorization(keymaster::TAG_MAC_LENGTH, GCM_MAC_BYTES * 8)
.Authorization(keymaster::TAG_PADDING, KM_PAD_NONE);
addStringParam(paramBuilder, keymaster::TAG_APPLICATION_ID, appId);
if (!auth.token.empty()) {
LOG(DEBUG) << "Supplying auth token to Keymaster";
addStringParam(paramBuilder, keymaster::TAG_AUTH_TOKEN, auth.token);
}
return paramBuilder;
}
static bool encryptWithKeymasterKey(
Keymaster &keymaster,
const std::string &key,
const keymaster::AuthorizationSet &extraParams,
const KeyAuthentication &auth,
const std::string &appId,
const std::string &message,
std::string &ciphertext) {
// FIXME fix repetition
auto params = keymaster::AuthorizationSetBuilder()
.Authorization(keymaster::TAG_BLOCK_MODE, KM_MODE_GCM)
.Authorization(keymaster::TAG_MAC_LENGTH, GCM_MAC_BYTES * 8)
.Authorization(keymaster::TAG_PADDING, KM_PAD_NONE)
.build();
params.push_back(extraParams);
auto params = beginParams(auth, appId).build();
keymaster::AuthorizationSet outParams;
auto opHandle = keymaster.begin(KM_PURPOSE_ENCRYPT, key, params, outParams);
if (!opHandle) return false;
@ -142,20 +166,15 @@ static bool encryptWithKeymasterKey(
}
static bool decryptWithKeymasterKey(
Keymaster &keymaster, const std::string &key,
const keymaster::AuthorizationSet &extraParams,
Keymaster &keymaster,
const std::string &key,
const KeyAuthentication &auth,
const std::string &appId,
const std::string &ciphertext,
std::string &message) {
auto nonce = ciphertext.substr(0, GCM_NONCE_BYTES);
auto bodyAndMac = ciphertext.substr(GCM_NONCE_BYTES);
// FIXME fix repetition
auto params = addStringParam(keymaster::AuthorizationSetBuilder(), keymaster::TAG_NONCE, nonce)
.Authorization(keymaster::TAG_BLOCK_MODE, KM_MODE_GCM)
.Authorization(keymaster::TAG_MAC_LENGTH, GCM_MAC_BYTES * 8)
.Authorization(keymaster::TAG_PADDING, KM_PAD_NONE)
.build();
params.push_back(extraParams);
auto params = addStringParam(beginParams(auth, appId), keymaster::TAG_NONCE, nonce).build();
auto opHandle = keymaster.begin(KM_PURPOSE_DECRYPT, key, params);
if (!opHandle) return false;
if (!opHandle.updateCompletely(bodyAndMac, message)) return false;
@ -224,18 +243,12 @@ static bool stretchSecret(const std::string &stretching, const std::string &secr
return true;
}
static bool buildParams(const KeyAuthentication &auth, const std::string &stretching,
static bool generateAppId(const KeyAuthentication &auth, const std::string &stretching,
const std::string &salt, const std::string &secdiscardable,
keymaster::AuthorizationSet &result) {
std::string& result) {
std::string stretched;
if (!stretchSecret(stretching, auth.secret, salt, stretched)) return false;
auto appId = hashSecdiscardable(secdiscardable) + stretched;
keymaster::AuthorizationSetBuilder paramBuilder;
addStringParam(paramBuilder, keymaster::TAG_APPLICATION_ID, appId);
if (!auth.token.empty()) {
addStringParam(paramBuilder, keymaster::TAG_AUTH_TOKEN, auth.token);
}
result = paramBuilder.build();
result = hashSecdiscardable(secdiscardable) + stretched;
return true;
}
@ -262,15 +275,15 @@ bool storeKey(const std::string &dir, const KeyAuthentication &auth, const std::
}
if (!writeStringToFile(salt, dir + "/" + kFn_salt)) return false;
}
keymaster::AuthorizationSet extraParams;
if (!buildParams(auth, stretching, salt, secdiscardable, extraParams)) return false;
std::string appId;
if (!generateAppId(auth, stretching, salt, secdiscardable, appId)) return false;
Keymaster keymaster;
if (!keymaster) return false;
std::string kmKey;
if (!generateKeymasterKey(keymaster, extraParams, kmKey)) return false;
std::string encryptedKey;
if (!encryptWithKeymasterKey(keymaster, kmKey, extraParams, key, encryptedKey)) return false;
if (!generateKeymasterKey(keymaster, auth, appId, kmKey)) return false;
if (!writeStringToFile(kmKey, dir + "/" + kFn_keymaster_key_blob)) return false;
std::string encryptedKey;
if (!encryptWithKeymasterKey(keymaster, kmKey, auth, appId, key, encryptedKey)) return false;
if (!writeStringToFile(encryptedKey, dir + "/" + kFn_encrypted_key)) return false;
return true;
}
@ -290,15 +303,15 @@ bool retrieveKey(const std::string &dir, const KeyAuthentication &auth, std::str
if (stretchingNeedsSalt(stretching)) {
if (!readFileToString(dir + "/" + kFn_salt, salt)) return false;
}
keymaster::AuthorizationSet extraParams;
if (!buildParams(auth, stretching, salt, secdiscardable, extraParams)) return false;
std::string appId;
if (!generateAppId(auth, stretching, salt, secdiscardable, appId)) return false;
std::string kmKey;
if (!readFileToString(dir + "/" + kFn_keymaster_key_blob, kmKey)) return false;
std::string encryptedMessage;
if (!readFileToString(dir + "/" + kFn_encrypted_key, encryptedMessage)) return false;
Keymaster keymaster;
if (!keymaster) return false;
return decryptWithKeymasterKey(keymaster, kmKey, extraParams, encryptedMessage, key);
return decryptWithKeymasterKey(keymaster, kmKey, auth, appId, encryptedMessage, key);
}
static bool deleteKey(const std::string &dir) {