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@ -39,8 +39,6 @@
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#include <private/android_filesystem_config.h>
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#include <fs_mgr.h>
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#include "cryptfs.h"
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#include "ext4_crypt.h"
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#include "key_control.h"
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@ -61,9 +59,6 @@ using android::vold::kEmptyAuthentication;
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static constexpr int FLAG_STORAGE_DE = 1 << 0;
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static constexpr int FLAG_STORAGE_CE = 1 << 1;
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// Vile hack to get fstab entries for file encryption type
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extern struct fstab *fstab;
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namespace {
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const std::string device_key_dir = std::string() + DATA_MNT_POINT + e4crypt_unencrypted_folder;
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const std::string device_key_path = device_key_dir + "/key";
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@ -99,218 +94,6 @@ struct ext4_encryption_key {
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};
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}
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#define XATTR_NAME_ENCRYPTION_POLICY "encryption.policy"
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#define EXT4_KEYREF_DELIMITER ((char)'.')
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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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#define EXT4_KEY_DESCRIPTOR_SIZE 8
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#define EXT4_KEY_DESCRIPTOR_SIZE_HEX 17
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struct ext4_encryption_policy {
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char version;
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char contents_encryption_mode;
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char filenames_encryption_mode;
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char flags;
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char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
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} __attribute__((__packed__));
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#define EXT4_ENCRYPTION_MODE_AES_256_XTS 1
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#define EXT4_ENCRYPTION_MODE_AES_256_CTS 4
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#define EXT4_ENCRYPTION_MODE_PRIVATE 127
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// ext4enc:TODO Get value from somewhere sensible
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#define EXT4_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct ext4_encryption_policy)
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#define EXT4_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct ext4_encryption_policy)
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#define HEX_LOOKUP "0123456789abcdef"
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static void policy_to_hex(const char* policy, char* hex) {
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for (size_t i = 0, j = 0; i < EXT4_KEY_DESCRIPTOR_SIZE; i++) {
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hex[j++] = HEX_LOOKUP[(policy[i] & 0xF0) >> 4];
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hex[j++] = HEX_LOOKUP[policy[i] & 0x0F];
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}
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hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX - 1] = '\0';
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}
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static bool is_dir_empty(const char *dirname, bool *is_empty)
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{
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int n = 0;
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auto dirp = std::unique_ptr<DIR, int (*)(DIR*)>(opendir(dirname), closedir);
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if (!dirp) {
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PLOG(ERROR) << "Unable to read directory: " << dirname;
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return false;
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}
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for (;;) {
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errno = 0;
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auto entry = readdir(dirp.get());
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if (!entry) {
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if (errno) {
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PLOG(ERROR) << "Unable to read directory: " << dirname;
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return false;
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}
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break;
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}
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if (strcmp(entry->d_name, "lost+found") != 0) { // Skip lost+found
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++n;
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if (n > 2) {
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*is_empty = false;
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return true;
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}
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}
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}
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*is_empty = true;
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return true;
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}
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static bool e4crypt_policy_set(const char *directory, const char *policy,
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size_t policy_length, int contents_encryption_type) {
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if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) {
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LOG(ERROR) << "Policy wrong length: " << policy_length;
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return false;
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}
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int fd = open(directory, O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
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if (fd == -1) {
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PLOG(ERROR) << "Failed to open directory " << directory;
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return false;
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}
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ext4_encryption_policy eep;
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eep.version = 0;
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eep.contents_encryption_mode = contents_encryption_type;
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eep.filenames_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_CTS;
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eep.flags = 0;
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memcpy(eep.master_key_descriptor, policy, EXT4_KEY_DESCRIPTOR_SIZE);
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if (ioctl(fd, EXT4_IOC_SET_ENCRYPTION_POLICY, &eep)) {
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PLOG(ERROR) << "Failed to set encryption policy for " << directory;
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close(fd);
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return false;
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}
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close(fd);
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char policy_hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX];
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policy_to_hex(policy, policy_hex);
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LOG(INFO) << "Policy for " << directory << " set to " << policy_hex;
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return true;
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}
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static bool e4crypt_policy_get(const char *directory, char *policy,
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size_t policy_length, int contents_encryption_type) {
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if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) {
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LOG(ERROR) << "Policy wrong length: " << policy_length;
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return false;
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}
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int fd = open(directory, O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
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if (fd == -1) {
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PLOG(ERROR) << "Failed to open directory " << directory;
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return false;
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}
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ext4_encryption_policy eep;
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memset(&eep, 0, sizeof(ext4_encryption_policy));
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if (ioctl(fd, EXT4_IOC_GET_ENCRYPTION_POLICY, &eep) != 0) {
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PLOG(ERROR) << "Failed to get encryption policy for " << directory;
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close(fd);
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return -1;
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}
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close(fd);
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if ((eep.version != 0)
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|| (eep.contents_encryption_mode != contents_encryption_type)
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|| (eep.filenames_encryption_mode != EXT4_ENCRYPTION_MODE_AES_256_CTS)
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|| (eep.flags != 0)) {
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LOG(ERROR) << "Failed to find matching encryption policy for " << directory;
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return false;
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}
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memcpy(policy, eep.master_key_descriptor, EXT4_KEY_DESCRIPTOR_SIZE);
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return true;
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}
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static bool e4crypt_policy_check(const char *directory, const char *policy,
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size_t policy_length, int contents_encryption_type) {
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if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) {
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LOG(ERROR) << "Policy wrong length: " << policy_length;
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return false;
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}
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char existing_policy[EXT4_KEY_DESCRIPTOR_SIZE];
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if (!e4crypt_policy_get(directory, existing_policy, EXT4_KEY_DESCRIPTOR_SIZE,
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contents_encryption_type)) {
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return false;
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}
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char existing_policy_hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX];
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policy_to_hex(existing_policy, existing_policy_hex);
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if (memcmp(policy, existing_policy, EXT4_KEY_DESCRIPTOR_SIZE) != 0) {
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char policy_hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX];
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policy_to_hex(policy, policy_hex);
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LOG(ERROR) << "Found policy " << existing_policy_hex << " at " << directory
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<< " which doesn't match expected value " << policy_hex;
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return false;
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}
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LOG(INFO) << "Found policy " << existing_policy_hex << " at " << directory
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<< " which matches expected value";
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return true;
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}
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int e4crypt_policy_ensure(const char* directory, const char* policy, int policy_length)
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{
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static int contents_encryption_type = 0;
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if (contents_encryption_type == 0) {
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// Get file_encryption_type from fstab
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struct fstab_rec *rec = fs_mgr_get_entry_for_mount_point(fstab, "/data");
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if (rec == 0) {
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return -1;
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}
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// Translate file_encryption_type to ext4 contents encryption type
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switch (rec->file_encryption_type)
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{
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case ET_SOFTWARE:
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contents_encryption_type = EXT4_ENCRYPTION_MODE_AES_256_XTS;
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break;
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case ET_ICE:
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contents_encryption_type = EXT4_ENCRYPTION_MODE_PRIVATE;
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break;
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default:
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return -1;
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}
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}
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bool is_empty;
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if (!is_dir_empty(directory, &is_empty)) return -1;
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if (is_empty) {
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if (!e4crypt_policy_set(directory, policy, policy_length,
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contents_encryption_type)) {
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return -1;
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}
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} else {
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if (!e4crypt_policy_check(directory, policy, policy_length,
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contents_encryption_type)) {
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return -1;
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}
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}
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return 0;
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}
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bool e4crypt_hex_policy_ensure(const char* dir, const char* hex_policy)
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{
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std::string hex = hex_policy;
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if (hex.substr(0, 2) != "0x") {
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return false;
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}
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std::string policy;
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if (android::vold::HexToStr(hex.substr(2), policy)) {
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return false;
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}
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return e4crypt_policy_ensure(dir, policy.c_str(), policy.length()) == 0;
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}
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static bool e4crypt_is_emulated() {
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return property_get_bool("persist.sys.emulate_fbe", false);
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}
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