1 files changed, 349 insertions, 0 deletions

diff --git a/crypto/ext4crypt/KeyStorage.cpp b/crypto/ext4crypt/KeyStorage.cpp
new file mode 100644
index 000000000..199520e9d
--- /dev/null
+++ b/crypto/ext4crypt/KeyStorage.cpp
@@ -0,0 +1,349 @@
+/*
+ * Copyright (C) 2016 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 "KeyStorage.h"
+
+#include "Keymaster.h"
+#include "ScryptParameters.h"
+#include "Utils.h"
+
+#include <vector>
+
+#include <errno.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <iostream>
+
+#include <openssl/sha.h>
+
+#include <android-base/file.h>
+//#include <android-base/logging.h>
+
+#include <cutils/properties.h>
+
+#include <hardware/hw_auth_token.h>
+
+#include <keymaster/authorization_set.h>
+
+extern "C" {
+
+#include "crypto_scrypt.h"
+}
+
+#define ERROR 1
+#define LOG(x) std::cout
+#define PLOG(x) std::cout
+
+namespace android {
+namespace vold {
+
+const KeyAuthentication kEmptyAuthentication{"", ""};
+
+static constexpr size_t AES_KEY_BYTES = 32;
+static constexpr size_t GCM_NONCE_BYTES = 12;
+static constexpr size_t GCM_MAC_BYTES = 16;
+static constexpr size_t SALT_BYTES = 1 << 4;
+static constexpr size_t SECDISCARDABLE_BYTES = 1 << 14;
+static constexpr size_t STRETCHED_BYTES = 1 << 6;
+
+static constexpr uint32_t AUTH_TIMEOUT = 30; // Seconds
+
+static const char* kCurrentVersion = "1";
+static const char* kRmPath = "/system/bin/rm";
+static const char* kSecdiscardPath = "/system/bin/secdiscard";
+static const char* kStretch_none = "none";
+static const char* kStretch_nopassword = "nopassword";
+static const std::string kStretchPrefix_scrypt = "scrypt ";
+static const char* kFn_encrypted_key = "encrypted_key";
+static const char* kFn_keymaster_key_blob = "keymaster_key_blob";
+static const char* kFn_salt = "salt";
+static const char* kFn_secdiscardable = "secdiscardable";
+static const char* kFn_stretching = "stretching";
+static const char* kFn_version = "version";
+
+static bool checkSize(const std::string& kind, size_t actual, size_t expected) {
+    if (actual != expected) {
+        LOG(ERROR) << "Wrong number of bytes in " << kind << ", expected " << expected << " got "
+                   << actual;
+        return false;
+    }
+    return true;
+}
+
+static std::string hashSecdiscardable(const std::string& secdiscardable) {
+    SHA512_CTX c;
+
+    SHA512_Init(&c);
+    // Personalise the hashing by introducing a fixed prefix.
+    // Hashing applications should use personalization except when there is a
+    // specific reason not to; see section 4.11 of https://www.schneier.com/skein1.3.pdf
+    std::string secdiscardableHashingPrefix = "Android secdiscardable SHA512";
+    secdiscardableHashingPrefix.resize(SHA512_CBLOCK);
+    SHA512_Update(&c, secdiscardableHashingPrefix.data(), secdiscardableHashingPrefix.size());
+    SHA512_Update(&c, secdiscardable.data(), secdiscardable.size());
+    std::string res(SHA512_DIGEST_LENGTH, '\0');
+    SHA512_Final(reinterpret_cast<uint8_t*>(&res[0]), &c);
+    return res;
+}
+
+/*static bool generateKeymasterKey(Keymaster& keymaster, const KeyAuthentication& auth,
+                                 const std::string& appId, std::string* key) {
+    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);
+    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, AUTH_TIMEOUT);
+    }
+    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 KeyAuthentication& auth, const std::string& appId,
+                                    const std::string& message, std::string* ciphertext) {
+    auto params = beginParams(auth, appId).build();
+    keymaster::AuthorizationSet outParams;
+    auto opHandle = keymaster.begin(KM_PURPOSE_ENCRYPT, key, params, &outParams);
+    if (!opHandle) return false;
+    keymaster_blob_t nonceBlob;
+    if (!outParams.GetTagValue(keymaster::TAG_NONCE, &nonceBlob)) {
+        LOG(ERROR) << "GCM encryption but no nonce generated";
+        return false;
+    }
+    // nonceBlob here is just a pointer into existing data, must not be freed
+    std::string nonce(reinterpret_cast<const char*>(nonceBlob.data), nonceBlob.data_length);
+    if (!checkSize("nonce", nonce.size(), GCM_NONCE_BYTES)) return false;
+    std::string body;
+    if (!opHandle.updateCompletely(message, &body)) return false;
+
+    std::string mac;
+    if (!opHandle.finishWithOutput(&mac)) return false;
+    if (!checkSize("mac", mac.size(), GCM_MAC_BYTES)) return false;
+    *ciphertext = nonce + body + mac;
+    return true;
+}*/
+
+static bool decryptWithKeymasterKey(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);
+    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;
+    if (!opHandle.finish()) return false;
+    return true;
+}
+
+static bool readFileToString(const std::string& filename, std::string* result) {
+    if (!android::base::ReadFileToString(filename, result)) {
+        PLOG(ERROR) << "Failed to read from " << filename;
+        return false;
+    }
+    return true;
+}
+
+/*static bool writeStringToFile(const std::string& payload, const std::string& filename) {
+    if (!android::base::WriteStringToFile(payload, filename)) {
+        PLOG(ERROR) << "Failed to write to " << filename;
+        return false;
+    }
+    return true;
+}*/
+
+static std::string getStretching() {
+    char paramstr[PROPERTY_VALUE_MAX];
+
+    property_get(SCRYPT_PROP, paramstr, SCRYPT_DEFAULTS);
+    return std::string() + kStretchPrefix_scrypt + paramstr;
+}
+
+static bool stretchingNeedsSalt(const std::string& stretching) {
+    return stretching != kStretch_nopassword && stretching != kStretch_none;
+}
+
+static bool stretchSecret(const std::string& stretching, const std::string& secret,
+                          const std::string& salt, std::string* stretched) {
+    if (stretching == kStretch_nopassword) {
+        if (!secret.empty()) {
+            LOG(WARNING) << "Password present but stretching is nopassword";
+            // Continue anyway
+        }
+        stretched->clear();
+    } else if (stretching == kStretch_none) {
+        *stretched = secret;
+    } else if (std::equal(kStretchPrefix_scrypt.begin(), kStretchPrefix_scrypt.end(),
+                          stretching.begin())) {
+        int Nf, rf, pf;
+        if (!parse_scrypt_parameters(stretching.substr(kStretchPrefix_scrypt.size()).c_str(), &Nf,
+                                     &rf, &pf)) {
+            LOG(ERROR) << "Unable to parse scrypt params in stretching: " << stretching;
+            return false;
+        }
+        stretched->assign(STRETCHED_BYTES, '\0');
+        if (crypto_scrypt(reinterpret_cast<const uint8_t*>(secret.data()), secret.size(),
+                          reinterpret_cast<const uint8_t*>(salt.data()), salt.size(),
+                          1 << Nf, 1 << rf, 1 << pf,
+                          reinterpret_cast<uint8_t*>(&(*stretched)[0]), stretched->size()) != 0) {
+            LOG(ERROR) << "scrypt failed with params: " << stretching;
+            return false;
+        }
+    } else {
+        LOG(ERROR) << "Unknown stretching type: " << stretching;
+        return false;
+    }
+    return true;
+}
+
+static bool generateAppId(const KeyAuthentication& auth, const std::string& stretching,
+                          const std::string& salt, const std::string& secdiscardable,
+                          std::string* appId) {
+    std::string stretched;
+    if (!stretchSecret(stretching, auth.secret, salt, &stretched)) return false;
+    *appId = hashSecdiscardable(secdiscardable) + stretched;
+    return true;
+}
+
+/*bool storeKey(const std::string& dir, const KeyAuthentication& auth, const std::string& key) {
+    if (TEMP_FAILURE_RETRY(mkdir(dir.c_str(), 0700)) == -1) {
+        PLOG(ERROR) << "key mkdir " << dir;
+        return false;
+    }
+    if (!writeStringToFile(kCurrentVersion, dir + "/" + kFn_version)) return false;
+    std::string secdiscardable;
+    if (ReadRandomBytes(SECDISCARDABLE_BYTES, secdiscardable) != OK) {
+        // TODO status_t plays badly with PLOG, fix it.
+        LOG(ERROR) << "Random read failed";
+        return false;
+    }
+    if (!writeStringToFile(secdiscardable, dir + "/" + kFn_secdiscardable)) return false;
+    std::string stretching = auth.secret.empty() ? kStretch_nopassword : getStretching();
+    if (!writeStringToFile(stretching, dir + "/" + kFn_stretching)) return false;
+    std::string salt;
+    if (stretchingNeedsSalt(stretching)) {
+        if (ReadRandomBytes(SALT_BYTES, salt) != OK) {
+            LOG(ERROR) << "Random read failed";
+            return false;
+        }
+        if (!writeStringToFile(salt, dir + "/" + kFn_salt)) 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, 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;
+}*/
+
+bool retrieveKey(const std::string& dir, const KeyAuthentication& auth, std::string* key) {
+    std::string version;
+    if (!readFileToString(dir + "/" + kFn_version, &version)) return false;
+    if (version != kCurrentVersion) {
+        LOG(ERROR) << "Version mismatch, expected " << kCurrentVersion << " got " << version;
+        return false;
+    }
+    std::string secdiscardable;
+    if (!readFileToString(dir + "/" + kFn_secdiscardable, &secdiscardable)) return false;
+    std::string stretching;
+    if (!readFileToString(dir + "/" + kFn_stretching, &stretching)) return false;
+    std::string salt;
+    if (stretchingNeedsSalt(stretching)) {
+        if (!readFileToString(dir + "/" + kFn_salt, &salt)) 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, auth, appId, encryptedMessage, key);
+}
+
+static bool deleteKey(const std::string& dir) {
+    std::string kmKey;
+    if (!readFileToString(dir + "/" + kFn_keymaster_key_blob, &kmKey)) return false;
+    Keymaster keymaster;
+    if (!keymaster) return false;
+    if (!keymaster.deleteKey(kmKey)) return false;
+    return true;
+}
+
+static bool secdiscardSecdiscardable(const std::string& dir) {
+    if (ForkExecvp(
+            std::vector<std::string>{kSecdiscardPath, "--", dir + "/" + kFn_secdiscardable}) != 0) {
+        LOG(ERROR) << "secdiscard failed";
+        return false;
+    }
+    return true;
+}
+
+static bool recursiveDeleteKey(const std::string& dir) {
+    if (ForkExecvp(std::vector<std::string>{kRmPath, "-rf", dir}) != 0) {
+        LOG(ERROR) << "recursive delete failed";
+        return false;
+    }
+    return true;
+}
+
+bool destroyKey(const std::string& dir) {
+    bool success = true;
+    // Try each thing, even if previous things failed.
+    success &= deleteKey(dir);
+    success &= secdiscardSecdiscardable(dir);
+    success &= recursiveDeleteKey(dir);
+    return success;
+}
+
+}  // namespace vold
+}  // namespace android