378 lines
12 KiB
C++
378 lines
12 KiB
C++
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#include "Ext4Crypt.h"
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#include <string>
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#include <fstream>
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#include <map>
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#include <errno.h>
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#include <sys/mount.h>
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#include <cutils/properties.h>
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#include "unencrypted_properties.h"
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#include "key_control.h"
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#include "cryptfs.h"
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#define LOG_TAG "Ext4Crypt"
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#include "cutils/log.h"
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#include <cutils/klog.h>
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namespace {
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// Key length in bits
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const int key_length = 128;
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// How is device encrypted
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struct keys {
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std::string master_key;
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std::string password;
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};
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std::map<std::string, keys> s_key_store;
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// ext4enc:TODO Include structure from somewhere sensible
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// MUST be in sync with ext4_crypto.c in kernel
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const int EXT4_MAX_KEY_SIZE = 76;
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struct ext4_encryption_key {
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uint32_t mode;
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char raw[EXT4_MAX_KEY_SIZE];
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uint32_t size;
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};
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namespace tag {
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const char* magic = "magic";
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const char* major_version = "major_version";
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const char* minor_version = "minor_version";
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const char* flags = "flags";
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const char* crypt_type = "crypt_type";
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const char* failed_decrypt_count = "failed_decrypt_count";
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const char* crypto_type_name = "crypto_type_name";
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const char* master_key = "master_key";
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const char* salt = "salt";
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const char* kdf_type = "kdf_type";
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const char* N_factor = "N_factor";
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const char* r_factor = "r_factor";
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const char* p_factor = "p_factor";
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const char* keymaster_blob = "keymaster_blob";
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const char* scrypted_intermediate_key = "scrypted_intermediate_key";
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}
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}
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static int put_crypt_ftr_and_key(const crypt_mnt_ftr& crypt_ftr,
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UnencryptedProperties& props)
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{
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SLOGI("Putting crypt footer");
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bool success = props.Set<int>(tag::magic, crypt_ftr.magic)
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&& props.Set<int>(tag::major_version, crypt_ftr.major_version)
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&& props.Set<int>(tag::minor_version, crypt_ftr.minor_version)
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&& props.Set<int>(tag::flags, crypt_ftr.flags)
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&& props.Set<int>(tag::crypt_type, crypt_ftr.crypt_type)
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&& props.Set<int>(tag::failed_decrypt_count,
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crypt_ftr.failed_decrypt_count)
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&& props.Set<std::string>(tag::crypto_type_name,
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std::string(reinterpret_cast<const char*>(crypt_ftr.crypto_type_name)))
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&& props.Set<std::string>(tag::master_key,
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std::string((const char*) crypt_ftr.master_key,
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crypt_ftr.keysize))
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&& props.Set<std::string>(tag::salt,
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std::string((const char*) crypt_ftr.salt,
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SALT_LEN))
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&& props.Set<int>(tag::kdf_type, crypt_ftr.kdf_type)
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&& props.Set<int>(tag::N_factor, crypt_ftr.N_factor)
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&& props.Set<int>(tag::r_factor, crypt_ftr.r_factor)
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&& props.Set<int>(tag::p_factor, crypt_ftr.p_factor)
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&& props.Set<std::string>(tag::keymaster_blob,
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std::string((const char*) crypt_ftr.keymaster_blob,
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crypt_ftr.keymaster_blob_size))
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&& props.Set<std::string>(tag::scrypted_intermediate_key,
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std::string((const char*) crypt_ftr.scrypted_intermediate_key,
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SCRYPT_LEN));
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return success ? 0 : -1;
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}
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static int get_crypt_ftr_and_key(crypt_mnt_ftr& crypt_ftr,
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const UnencryptedProperties& props)
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{
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memset(&crypt_ftr, 0, sizeof(crypt_ftr));
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crypt_ftr.magic = props.Get<int>(tag::magic);
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crypt_ftr.major_version = props.Get<int>(tag::major_version);
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crypt_ftr.minor_version = props.Get<int>(tag::minor_version);
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crypt_ftr.flags = props.Get<int>(tag::flags);
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crypt_ftr.crypt_type = props.Get<int>(tag::crypt_type);
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crypt_ftr.failed_decrypt_count = props.Get<int>(tag::failed_decrypt_count);
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std::string crypto_type_name = props.Get<std::string>(tag::crypto_type_name);
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strlcpy(reinterpret_cast<char*>(crypt_ftr.crypto_type_name),
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crypto_type_name.c_str(),
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sizeof(crypt_ftr.crypto_type_name));
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std::string master_key = props.Get<std::string>(tag::master_key);
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crypt_ftr.keysize = master_key.size();
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if (crypt_ftr.keysize > sizeof(crypt_ftr.master_key)) {
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SLOGE("Master key size too long");
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return -1;
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}
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memcpy(crypt_ftr.master_key, &master_key[0], crypt_ftr.keysize);
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std::string salt = props.Get<std::string>(tag::salt);
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if (salt.size() != SALT_LEN) {
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SLOGE("Salt wrong length");
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return -1;
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}
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memcpy(crypt_ftr.salt, &salt[0], SALT_LEN);
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crypt_ftr.kdf_type = props.Get<int>(tag::kdf_type);
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crypt_ftr.N_factor = props.Get<int>(tag::N_factor);
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crypt_ftr.r_factor = props.Get<int>(tag::r_factor);
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crypt_ftr.p_factor = props.Get<int>(tag::p_factor);
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std::string keymaster_blob = props.Get<std::string>(tag::keymaster_blob);
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crypt_ftr.keymaster_blob_size = keymaster_blob.size();
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if (crypt_ftr.keymaster_blob_size > sizeof(crypt_ftr.keymaster_blob)) {
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SLOGE("Keymaster blob too long");
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return -1;
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}
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memcpy(crypt_ftr.keymaster_blob, &keymaster_blob[0],
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crypt_ftr.keymaster_blob_size);
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std::string scrypted_intermediate_key = props.Get<std::string>(tag::scrypted_intermediate_key);
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if (scrypted_intermediate_key.size() != SCRYPT_LEN) {
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SLOGE("scrypted intermediate key wrong length");
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return -1;
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}
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memcpy(crypt_ftr.scrypted_intermediate_key, &scrypted_intermediate_key[0],
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SCRYPT_LEN);
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return 0;
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}
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static UnencryptedProperties GetProps(const char* path)
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{
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return UnencryptedProperties(path);
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}
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static UnencryptedProperties GetAltProps(const char* path)
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{
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return UnencryptedProperties((std::string() + path + "/tmp_mnt").c_str());
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}
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static UnencryptedProperties GetPropsOrAltProps(const char* path)
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{
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UnencryptedProperties props = GetProps(path);
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if (props.OK()) {
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return props;
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}
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return GetAltProps(path);
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}
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int e4crypt_enable(const char* path)
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{
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// Already enabled?
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if (s_key_store.find(path) != s_key_store.end()) {
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return 0;
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}
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// Not an encryptable device?
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UnencryptedProperties key_props = GetProps(path).GetChild(properties::key);
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if (!key_props.OK()) {
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return 0;
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}
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if (key_props.Get<std::string>(tag::master_key).empty()) {
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crypt_mnt_ftr ftr;
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if (cryptfs_create_default_ftr(&ftr, key_length)) {
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SLOGE("Failed to create crypto footer");
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return -1;
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}
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if (put_crypt_ftr_and_key(ftr, key_props)) {
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SLOGE("Failed to write crypto footer");
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return -1;
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}
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crypt_mnt_ftr ftr2;
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if (get_crypt_ftr_and_key(ftr2, key_props)) {
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SLOGE("Failed to read crypto footer back");
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return -1;
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}
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if (memcmp(&ftr, &ftr2, sizeof(ftr)) != 0) {
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SLOGE("Crypto footer not correctly written");
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// ex4enc:TODO why is this failing?
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//return -1;
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}
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}
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if (!UnencryptedProperties(path).Remove(properties::ref)) {
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SLOGE("Failed to remove key ref");
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return -1;
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}
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return e4crypt_check_passwd(path, "");
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}
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int e4crypt_change_password(const char* path, int crypt_type,
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const char* password)
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{
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SLOGI("e4crypt_change_password");
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UnencryptedProperties key_props = GetProps(path).GetChild(properties::key);
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crypt_mnt_ftr ftr;
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if (get_crypt_ftr_and_key(ftr, key_props)) {
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SLOGE("Failed to read crypto footer back");
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return -1;
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}
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auto mki = s_key_store.find(path);
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if (mki == s_key_store.end()) {
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SLOGE("No stored master key - can't change password");
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return -1;
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}
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const unsigned char* master_key
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= reinterpret_cast<const unsigned char*>(&mki->second.master_key[0]);
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if (cryptfs_set_password(&ftr, password, master_key)) {
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SLOGE("Failed to set password");
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return -1;
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}
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ftr.crypt_type = crypt_type;
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if (put_crypt_ftr_and_key(ftr, key_props)) {
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SLOGE("Failed to write crypto footer");
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return -1;
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}
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if (!UnencryptedProperties(path).Set(properties::is_default,
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crypt_type == CRYPT_TYPE_DEFAULT)) {
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SLOGE("Failed to update default flag");
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return -1;
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}
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return 0;
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}
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int e4crypt_crypto_complete(const char* path)
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{
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SLOGI("ext4 crypto complete called on %s", path);
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UnencryptedProperties key_props
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= GetPropsOrAltProps(path).GetChild(properties::key);
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if (key_props.Get<std::string>(tag::master_key).empty()) {
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SLOGI("No master key, so not ext4enc");
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return -1;
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}
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return 0;
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}
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int e4crypt_check_passwd(const char* path, const char* password)
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{
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SLOGI("e4crypt_check_password");
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// ext4enc:TODO once we have password checking, fix this to be
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// GetKeyOrAltKey
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UnencryptedProperties props = *password ? GetAltProps(path)
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: GetProps(path);
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UnencryptedProperties key_props = props.GetChild(properties::key);
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crypt_mnt_ftr ftr;
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if (get_crypt_ftr_and_key(ftr, key_props)) {
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SLOGE("Failed to read crypto footer back");
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return -1;
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}
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unsigned char master_key[key_length / 8];
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if (cryptfs_get_master_key (&ftr, password, master_key)){
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SLOGI("Incorrect password");
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return -1;
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}
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s_key_store[path] = keys{std::string(reinterpret_cast<char*>(master_key),
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sizeof(master_key)),
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password};
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// Install password into global keyring
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ext4_encryption_key ext4_key = {0, {0}, key_length / 8};
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memcpy(ext4_key.raw, master_key, ext4_key.size);
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// ext4enc:TODO Use better reference not 1234567890
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key_serial_t device_keyring = keyctl_search(KEY_SPEC_SESSION_KEYRING,
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"keyring", "e4crypt", 0);
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SLOGI("Found device_keyring - id is %d", device_keyring);
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key_serial_t key_id = add_key("logon", "ext4-key:1234567890",
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(void*)&ext4_key, sizeof(ext4_key),
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device_keyring);
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if (key_id == -1) {
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SLOGE("Failed to insert key into keyring with error %s",
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strerror(errno));
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return -1;
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}
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SLOGI("Added key %d to keyring %d in process %d",
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key_id, device_keyring, getpid());
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// ext4enc:TODO set correct permissions
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long result = keyctl_setperm(key_id, 0x3f3f3f3f);
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if (result) {
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SLOGE("KEYCTL_SETPERM failed with error %ld", result);
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return -1;
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}
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// Save reference to key so we can set policy later
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if (!props.Set(properties::ref, "@s.ext4-key:1234567890")) {
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SLOGE("Cannot save key reference");
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return -1;
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}
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return 0;
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}
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int e4crypt_restart(const char* path)
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{
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SLOGI("e4crypt_restart");
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int rc = 0;
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SLOGI("ext4 restart called on %s", path);
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property_set("vold.decrypt", "trigger_reset_main");
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SLOGI("Just asked init to shut down class main");
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sleep(2);
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std::string tmp_path = std::string() + path + "/tmp_mnt";
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// ext4enc:TODO add retry logic
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rc = umount(tmp_path.c_str());
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if (rc) {
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SLOGE("umount %s failed with rc %d, msg %s",
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tmp_path.c_str(), rc, strerror(errno));
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return rc;
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}
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// ext4enc:TODO add retry logic
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rc = umount(path);
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if (rc) {
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SLOGE("umount %s failed with rc %d, msg %s",
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path, rc, strerror(errno));
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return rc;
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}
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return 0;
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}
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const char* e4crypt_get_password(const char* path)
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{
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SLOGI("e4crypt_get_password");
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||
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||
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// ext4enc:TODO scrub password after timeout
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auto i = s_key_store.find(path);
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||
|
|
if (i == s_key_store.end()) {
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||
|
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return 0;
|
||
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|
} else {
|
||
|
|
return i->second.password.c_str();
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
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int e4crypt_get_password_type(const char* path)
|
||
|
|
{
|
||
|
|
SLOGI("e4crypt_get_password_type");
|
||
|
|
return GetPropsOrAltProps(path).GetChild(properties::key)
|
||
|
|
.Get<int>(tag::crypt_type, CRYPT_TYPE_DEFAULT);
|
||
|
|
}
|