| /* |
| * Copyright (C) 2015 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 "ext4_utils/ext4_crypt.h" |
| |
| #include <asm/ioctl.h> |
| #include <dirent.h> |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <string.h> |
| #include <sys/syscall.h> |
| #include <sys/stat.h> |
| #include <sys/types.h> |
| #include <unistd.h> |
| |
| #include <android-base/file.h> |
| #include <android-base/logging.h> |
| #include <cutils/properties.h> |
| |
| #define XATTR_NAME_ENCRYPTION_POLICY "encryption.policy" |
| #define EXT4_KEYREF_DELIMITER ((char)'.') |
| |
| // ext4enc:TODO Include structure from somewhere sensible |
| // MUST be in sync with ext4_crypto.c in kernel |
| #define EXT4_KEY_DESCRIPTOR_SIZE 8 |
| #define EXT4_KEY_DESCRIPTOR_SIZE_HEX 17 |
| |
| struct ext4_encryption_policy { |
| uint8_t version; |
| uint8_t contents_encryption_mode; |
| uint8_t filenames_encryption_mode; |
| uint8_t flags; |
| uint8_t master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE]; |
| } __attribute__((__packed__)); |
| |
| #define EXT4_ENCRYPTION_MODE_AES_256_XTS 1 |
| #define EXT4_ENCRYPTION_MODE_AES_256_CTS 4 |
| #define EXT4_ENCRYPTION_MODE_AES_256_HEH 126 |
| #define EXT4_ENCRYPTION_MODE_PRIVATE 127 |
| |
| #define EXT4_POLICY_FLAGS_PAD_4 0x00 |
| #define EXT4_POLICY_FLAGS_PAD_8 0x01 |
| #define EXT4_POLICY_FLAGS_PAD_16 0x02 |
| #define EXT4_POLICY_FLAGS_PAD_32 0x03 |
| #define EXT4_POLICY_FLAGS_PAD_MASK 0x03 |
| #define EXT4_POLICY_FLAGS_VALID 0x03 |
| |
| // ext4enc:TODO Get value from somewhere sensible |
| #define EXT4_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct ext4_encryption_policy) |
| #define EXT4_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct ext4_encryption_policy) |
| |
| #define HEX_LOOKUP "0123456789abcdef" |
| |
| bool e4crypt_is_native() { |
| char value[PROPERTY_VALUE_MAX]; |
| property_get("ro.crypto.type", value, "none"); |
| return !strcmp(value, "file"); |
| } |
| |
| static void policy_to_hex(const char* policy, char* hex) { |
| for (size_t i = 0, j = 0; i < EXT4_KEY_DESCRIPTOR_SIZE; i++) { |
| hex[j++] = HEX_LOOKUP[(policy[i] & 0xF0) >> 4]; |
| hex[j++] = HEX_LOOKUP[policy[i] & 0x0F]; |
| } |
| hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX - 1] = '\0'; |
| } |
| |
| static bool is_dir_empty(const char *dirname, bool *is_empty) |
| { |
| int n = 0; |
| auto dirp = std::unique_ptr<DIR, int (*)(DIR*)>(opendir(dirname), closedir); |
| if (!dirp) { |
| PLOG(ERROR) << "Unable to read directory: " << dirname; |
| return false; |
| } |
| for (;;) { |
| errno = 0; |
| auto entry = readdir(dirp.get()); |
| if (!entry) { |
| if (errno) { |
| PLOG(ERROR) << "Unable to read directory: " << dirname; |
| return false; |
| } |
| break; |
| } |
| if (strcmp(entry->d_name, "lost+found") != 0) { // Skip lost+found |
| ++n; |
| if (n > 2) { |
| *is_empty = false; |
| return true; |
| } |
| } |
| } |
| *is_empty = true; |
| return true; |
| } |
| |
| static uint8_t e4crypt_get_policy_flags(int filenames_encryption_mode) { |
| |
| // With HEH, pad filenames with zeroes to the next 16-byte boundary. This |
| // is not required, but it's more secure (helps hide the length of |
| // filenames), makes the inputs evenly divisible into blocks which is more |
| // efficient for encryption and decryption, and we had the opportunity to |
| // make a breaking change when introducing a new mode anyway. |
| if (filenames_encryption_mode == EXT4_ENCRYPTION_MODE_AES_256_HEH) { |
| return EXT4_POLICY_FLAGS_PAD_16; |
| } |
| |
| // Default flags (4-byte padding) for CTS |
| return EXT4_POLICY_FLAGS_PAD_4; |
| } |
| |
| static bool e4crypt_policy_set(const char *directory, const char *policy, |
| size_t policy_length, |
| int contents_encryption_mode, |
| int filenames_encryption_mode) { |
| if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) { |
| LOG(ERROR) << "Policy wrong length: " << policy_length; |
| return false; |
| } |
| int fd = open(directory, O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC); |
| if (fd == -1) { |
| PLOG(ERROR) << "Failed to open directory " << directory; |
| return false; |
| } |
| |
| ext4_encryption_policy eep; |
| eep.version = 0; |
| eep.contents_encryption_mode = contents_encryption_mode; |
| eep.filenames_encryption_mode = filenames_encryption_mode; |
| eep.flags = e4crypt_get_policy_flags(filenames_encryption_mode); |
| memcpy(eep.master_key_descriptor, policy, EXT4_KEY_DESCRIPTOR_SIZE); |
| if (ioctl(fd, EXT4_IOC_SET_ENCRYPTION_POLICY, &eep)) { |
| PLOG(ERROR) << "Failed to set encryption policy for " << directory; |
| close(fd); |
| return false; |
| } |
| close(fd); |
| |
| char policy_hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX]; |
| policy_to_hex(policy, policy_hex); |
| LOG(INFO) << "Policy for " << directory << " set to " << policy_hex; |
| return true; |
| } |
| |
| static bool e4crypt_policy_get(const char *directory, char *policy, |
| size_t policy_length, |
| int contents_encryption_mode, |
| int filenames_encryption_mode) { |
| if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) { |
| LOG(ERROR) << "Policy wrong length: " << policy_length; |
| return false; |
| } |
| |
| int fd = open(directory, O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC); |
| if (fd == -1) { |
| PLOG(ERROR) << "Failed to open directory " << directory; |
| return false; |
| } |
| |
| ext4_encryption_policy eep; |
| memset(&eep, 0, sizeof(ext4_encryption_policy)); |
| if (ioctl(fd, EXT4_IOC_GET_ENCRYPTION_POLICY, &eep) != 0) { |
| PLOG(ERROR) << "Failed to get encryption policy for " << directory; |
| close(fd); |
| return false; |
| } |
| close(fd); |
| |
| if ((eep.version != 0) |
| || (eep.contents_encryption_mode != contents_encryption_mode) |
| || (eep.filenames_encryption_mode != filenames_encryption_mode) |
| || (eep.flags != |
| e4crypt_get_policy_flags(filenames_encryption_mode))) { |
| LOG(ERROR) << "Failed to find matching encryption policy for " << directory; |
| return false; |
| } |
| memcpy(policy, eep.master_key_descriptor, EXT4_KEY_DESCRIPTOR_SIZE); |
| |
| return true; |
| } |
| |
| static bool e4crypt_policy_check(const char *directory, const char *policy, |
| size_t policy_length, |
| int contents_encryption_mode, |
| int filenames_encryption_mode) { |
| if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) { |
| LOG(ERROR) << "Policy wrong length: " << policy_length; |
| return false; |
| } |
| char existing_policy[EXT4_KEY_DESCRIPTOR_SIZE]; |
| if (!e4crypt_policy_get(directory, existing_policy, EXT4_KEY_DESCRIPTOR_SIZE, |
| contents_encryption_mode, |
| filenames_encryption_mode)) return false; |
| char existing_policy_hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX]; |
| |
| policy_to_hex(existing_policy, existing_policy_hex); |
| |
| if (memcmp(policy, existing_policy, EXT4_KEY_DESCRIPTOR_SIZE) != 0) { |
| char policy_hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX]; |
| policy_to_hex(policy, policy_hex); |
| LOG(ERROR) << "Found policy " << existing_policy_hex << " at " << directory |
| << " which doesn't match expected value " << policy_hex; |
| return false; |
| } |
| LOG(INFO) << "Found policy " << existing_policy_hex << " at " << directory |
| << " which matches expected value"; |
| return true; |
| } |
| |
| int e4crypt_policy_ensure(const char *directory, const char *policy, |
| size_t policy_length, |
| const char *contents_encryption_mode, |
| const char *filenames_encryption_mode) { |
| int contents_mode = 0; |
| int filenames_mode = 0; |
| |
| if (!strcmp(contents_encryption_mode, "software") || |
| !strcmp(contents_encryption_mode, "aes-256-xts")) { |
| contents_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS; |
| } else if (!strcmp(contents_encryption_mode, "ice")) { |
| contents_mode = EXT4_ENCRYPTION_MODE_PRIVATE; |
| } else { |
| LOG(ERROR) << "Invalid file contents encryption mode: " |
| << contents_encryption_mode; |
| return -1; |
| } |
| |
| if (!strcmp(filenames_encryption_mode, "aes-256-cts")) { |
| filenames_mode = EXT4_ENCRYPTION_MODE_AES_256_CTS; |
| } else if (!strcmp(filenames_encryption_mode, "aes-256-heh")) { |
| filenames_mode = EXT4_ENCRYPTION_MODE_AES_256_HEH; |
| } else { |
| LOG(ERROR) << "Invalid file names encryption mode: " |
| << filenames_encryption_mode; |
| return -1; |
| } |
| |
| bool is_empty; |
| if (!is_dir_empty(directory, &is_empty)) return -1; |
| if (is_empty) { |
| if (!e4crypt_policy_set(directory, policy, policy_length, |
| contents_mode, filenames_mode)) return -1; |
| } else { |
| if (!e4crypt_policy_check(directory, policy, policy_length, |
| contents_mode, filenames_mode)) return -1; |
| } |
| return 0; |
| } |