From 1ee35cf002de9f6aaa6f33e67d882cdbbaa35cc2 Mon Sep 17 00:00:00 2001 From: Nikita Ioffe Date: Fri, 28 Feb 2020 19:50:31 +0000 Subject: [PATCH] fskeyring & userspace reboot: support CE keys During userspace reboot /data might be unmounted & remounted, meaning that CE keys stored in fs-level keyring will be lost. In order to be able to restore them, when installing new key to fs-level keyring, it's also added to session-level keyring with type "fscrypt-provisioning". Then when init_user0 is called during userspace reboot, vold will try to load CE keys from the session-level keyring back into fs-level keyring for all the users that were unlocked before the reboot. If for any user vold fails to install the key, init_user0 will fail and fallback to hard reboot will be triggered. Test: set a pin pattern Test: adb shell setprop sys.init.userdata_remount.force_umount 1 Test: adb shell svc power reboot userspace Test: atest CtsUserspaceRebootHostSideTestCases Bug: 143970043 Change-Id: I37603dc136c7ededc7b0381e4d730cb0ffd912b4 --- FsCrypt.cpp | 18 +++++++ KeyUtil.cpp | 125 ++++++++++++++++++++++++++++++++++++++++++------- KeyUtil.h | 17 +++++-- fscrypt_uapi.h | 10 +++- 4 files changed, 149 insertions(+), 21 deletions(-) diff --git a/FsCrypt.cpp b/FsCrypt.cpp index d43bc08..d8af6f4 100644 --- a/FsCrypt.cpp +++ b/FsCrypt.cpp @@ -378,6 +378,17 @@ static bool load_all_de_keys() { return true; } +// Attempt to reinstall CE keys for users that we think are unlocked. +static bool try_reload_ce_keys() { + for (const auto& it : s_ce_policies) { + if (!android::vold::reloadKeyFromSessionKeyring(DATA_MNT_POINT, it.second)) { + LOG(ERROR) << "Failed to load CE key from session keyring for user " << it.first; + return false; + } + } + return true; +} + bool fscrypt_initialize_systemwide_keys() { LOG(INFO) << "fscrypt_initialize_systemwide_keys"; @@ -444,6 +455,13 @@ bool fscrypt_init_user0() { fscrypt_unlock_user_key(0, 0, "!", "!"); } + // In some scenarios (e.g. userspace reboot) we might unmount userdata + // without doing a hard reboot. If CE keys were stored in fs keyring then + // they will be lost after unmount. Attempt to re-install them. + if (fscrypt_is_native() && android::vold::isFsKeyringSupported()) { + if (!try_reload_ce_keys()) return false; + } + return true; } diff --git a/KeyUtil.cpp b/KeyUtil.cpp index 6200c42..3359699 100644 --- a/KeyUtil.cpp +++ b/KeyUtil.cpp @@ -155,7 +155,7 @@ static bool fscryptKeyring(key_serial_t* device_keyring) { return true; } -// Add an encryption key to the legacy global session keyring. +// Add an encryption key of type "logon" to the global session keyring. static bool installKeyLegacy(const KeyBuffer& key, const std::string& raw_ref) { // Place fscrypt_key into automatically zeroing buffer. KeyBuffer fsKeyBuffer(sizeof(fscrypt_key)); @@ -178,6 +178,32 @@ static bool installKeyLegacy(const KeyBuffer& key, const std::string& raw_ref) { return true; } +// Installs fscrypt-provisioning key into session level kernel keyring. +// This allows for the given key to be installed back into filesystem keyring. +// For more context see reloadKeyFromSessionKeyring. +static bool installProvisioningKey(const KeyBuffer& key, const std::string& ref, + const fscrypt_key_specifier& key_spec) { + key_serial_t device_keyring; + if (!fscryptKeyring(&device_keyring)) return false; + + // Place fscrypt_provisioning_key_payload into automatically zeroing buffer. + KeyBuffer buf(sizeof(fscrypt_provisioning_key_payload) + key.size(), 0); + fscrypt_provisioning_key_payload& provisioning_key = + *reinterpret_cast(buf.data()); + memcpy(provisioning_key.raw, key.data(), key.size()); + provisioning_key.type = key_spec.type; + + key_serial_t key_id = add_key("fscrypt-provisioning", ref.c_str(), (void*)&provisioning_key, + buf.size(), device_keyring); + if (key_id == -1) { + PLOG(ERROR) << "Failed to insert fscrypt-provisioning key for " << ref + << " into session keyring"; + return false; + } + LOG(DEBUG) << "Added fscrypt-provisioning key for " << ref << " to session keyring"; + return true; +} + // Build a struct fscrypt_key_specifier for use in the key management ioctls. static bool buildKeySpecifier(fscrypt_key_specifier* spec, const EncryptionPolicy& policy) { switch (policy.options.version) { @@ -205,6 +231,34 @@ static bool buildKeySpecifier(fscrypt_key_specifier* spec, const EncryptionPolic } } +// Installs key into keyring of a filesystem mounted on |mountpoint|. +// +// It's callers responsibility to fill key specifier, and either arg->raw or arg->key_id. +// +// In case arg->key_spec.type equals to FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER +// arg->key_spec.u.identifier will be populated with raw key reference generated +// by kernel. +// +// For documentation on difference between arg->raw and arg->key_id see +// https://www.kernel.org/doc/html/latest/filesystems/fscrypt.html#fs-ioc-add-encryption-key +static bool installFsKeyringKey(const std::string& mountpoint, const EncryptionOptions& options, + fscrypt_add_key_arg* arg) { + if (options.use_hw_wrapped_key) arg->flags |= FSCRYPT_ADD_KEY_FLAG_WRAPPED; + + android::base::unique_fd fd(open(mountpoint.c_str(), O_RDONLY | O_DIRECTORY | O_CLOEXEC)); + if (fd == -1) { + PLOG(ERROR) << "Failed to open " << mountpoint << " to install key"; + return false; + } + + if (ioctl(fd, FS_IOC_ADD_ENCRYPTION_KEY, arg) != 0) { + PLOG(ERROR) << "Failed to install fscrypt key to " << mountpoint; + return false; + } + + return true; +} + bool installKey(const std::string& mountpoint, const EncryptionOptions& options, const KeyBuffer& key, EncryptionPolicy* policy) { policy->options = options; @@ -240,33 +294,24 @@ bool installKey(const std::string& mountpoint, const EncryptionOptions& options, return false; } - if (options.use_hw_wrapped_key) arg->flags |= FSCRYPT_ADD_KEY_FLAG_WRAPPED; - // Provide the raw key. arg->raw_size = key.size(); memcpy(arg->raw, key.data(), key.size()); - android::base::unique_fd fd(open(mountpoint.c_str(), O_RDONLY | O_DIRECTORY | O_CLOEXEC)); - if (fd == -1) { - PLOG(ERROR) << "Failed to open " << mountpoint << " to install key"; - return false; - } - - if (ioctl(fd, FS_IOC_ADD_ENCRYPTION_KEY, arg) != 0) { - PLOG(ERROR) << "Failed to install fscrypt key to " << mountpoint; - return false; - } + if (!installFsKeyringKey(mountpoint, options, arg)) return false; if (arg->key_spec.type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) { // Retrieve the key identifier that the kernel computed. policy->key_raw_ref = std::string((char*)arg->key_spec.u.identifier, FSCRYPT_KEY_IDENTIFIER_SIZE); } - LOG(DEBUG) << "Installed fscrypt key with ref " << keyrefstring(policy->key_raw_ref) << " to " - << mountpoint; + std::string ref = keyrefstring(policy->key_raw_ref); + LOG(DEBUG) << "Installed fscrypt key with ref " << ref << " to " << mountpoint; + + if (!installProvisioningKey(key, ref, arg->key_spec)) return false; return true; } -// Remove an encryption key from the legacy global session keyring. +// Remove an encryption key of type "logon" from the global session keyring. static bool evictKeyLegacy(const std::string& raw_ref) { key_serial_t device_keyring; if (!fscryptKeyring(&device_keyring)) return false; @@ -289,6 +334,26 @@ static bool evictKeyLegacy(const std::string& raw_ref) { return success; } +static bool evictProvisioningKey(const std::string& ref) { + key_serial_t device_keyring; + if (!fscryptKeyring(&device_keyring)) { + return false; + } + + auto key_serial = keyctl_search(device_keyring, "fscrypt-provisioning", ref.c_str(), 0); + if (key_serial == -1 && errno != ENOKEY) { + PLOG(ERROR) << "Error searching session keyring for fscrypt-provisioning key for " << ref; + return false; + } + + if (key_serial != -1 && keyctl_unlink(key_serial, device_keyring) != 0) { + PLOG(ERROR) << "Failed to unlink fscrypt-provisioning key for " << ref + << " from session keyring"; + return false; + } + return true; +} + bool evictKey(const std::string& mountpoint, const EncryptionPolicy& policy) { if (policy.options.version == 1 && !isFsKeyringSupported()) { return evictKeyLegacy(policy.key_raw_ref); @@ -322,6 +387,8 @@ bool evictKey(const std::string& mountpoint, const EncryptionPolicy& policy) { LOG(ERROR) << "Files still open after removing key with ref " << ref << ". These files were not locked!"; } + + if (!evictProvisioningKey(ref)) return false; return true; } @@ -343,5 +410,31 @@ bool retrieveOrGenerateKey(const std::string& key_path, const std::string& tmp_p return true; } +bool reloadKeyFromSessionKeyring(const std::string& mountpoint, const EncryptionPolicy& policy) { + key_serial_t device_keyring; + if (!fscryptKeyring(&device_keyring)) { + return false; + } + + std::string ref = keyrefstring(policy.key_raw_ref); + auto key_serial = keyctl_search(device_keyring, "fscrypt-provisioning", ref.c_str(), 0); + if (key_serial == -1) { + PLOG(ERROR) << "Failed to find fscrypt-provisioning key for " << ref + << " in session keyring"; + return false; + } + + LOG(DEBUG) << "Installing fscrypt-provisioning key for " << ref << " back into " << mountpoint + << " fs-keyring"; + + struct fscrypt_add_key_arg arg; + memset(&arg, 0, sizeof(arg)); + if (!buildKeySpecifier(&arg.key_spec, policy)) return false; + arg.key_id = key_serial; + if (!installFsKeyringKey(mountpoint, policy.options, &arg)) return false; + + return true; +} + } // namespace vold } // namespace android diff --git a/KeyUtil.h b/KeyUtil.h index dcb1dc7..23278c1 100644 --- a/KeyUtil.h +++ b/KeyUtil.h @@ -51,11 +51,16 @@ bool isFsKeyringSupported(void); // on the specified filesystem using the specified encryption policy version. // // For v1 policies, we use FS_IOC_ADD_ENCRYPTION_KEY if the kernel supports it. -// Otherwise we add the key to the legacy global session keyring. +// Otherwise we add the key to the global session keyring as a "logon" key. // // For v2 policies, we always use FS_IOC_ADD_ENCRYPTION_KEY; it's the only way // the kernel supports. // +// If kernel supports FS_IOC_ADD_ENCRYPTION_KEY, also installs key of +// fscrypt-provisioning type to the global session keyring. This makes it +// possible to unmount and then remount mountpoint without losing the file-based +// key. +// // Returns %true on success, %false on failure. On success also sets *policy // to the EncryptionPolicy used to refer to this key. bool installKey(const std::string& mountpoint, const EncryptionOptions& options, @@ -63,16 +68,20 @@ bool installKey(const std::string& mountpoint, const EncryptionOptions& options, // Evict a file-based encryption key from the kernel. // -// We use FS_IOC_REMOVE_ENCRYPTION_KEY if the kernel supports it. Otherwise we -// remove the key from the legacy global session keyring. +// This undoes the effect of installKey(). // -// In the latter case, the caller is responsible for dropping caches. +// If the kernel doesn't support the filesystem-level keyring, the caller is +// responsible for dropping caches. bool evictKey(const std::string& mountpoint, const EncryptionPolicy& policy); bool retrieveOrGenerateKey(const std::string& key_path, const std::string& tmp_path, const KeyAuthentication& key_authentication, const KeyGeneration& gen, KeyBuffer* key, bool keepOld = true); +// Re-installs a file-based encryption key of fscrypt-provisioning type from the +// global session keyring back into fs keyring of the mountpoint. +bool reloadKeyFromSessionKeyring(const std::string& mountpoint, const EncryptionPolicy& policy); + } // namespace vold } // namespace android diff --git a/fscrypt_uapi.h b/fscrypt_uapi.h index 08592e0..3cda96e 100644 --- a/fscrypt_uapi.h +++ b/fscrypt_uapi.h @@ -9,11 +9,19 @@ struct sys_fscrypt_add_key_arg { struct fscrypt_key_specifier key_spec; __u32 raw_size; - __u32 __reserved[8]; + __u32 key_id; + __u32 __reserved[7]; __u32 flags; __u8 raw[]; }; +struct sys_fscrypt_provisioning_key_payload { + __u32 type; + __u32 __reserved; + __u8 raw[]; +}; + #define fscrypt_add_key_arg sys_fscrypt_add_key_arg +#define fscrypt_provisioning_key_payload sys_fscrypt_provisioning_key_payload #endif //_UAPI_LINUX_FSCRYPT_VOLD_H