// Copyright (c) 2012-2014 Konstantin Isakov <ikm@zbackup.org> and ZBackup contributors, see CONTRIBUTORS
// Part of ZBackup. Licensed under GNU GPLv2 or later + OpenSSL, see LICENSE

// Protobuffers used in zbackup

// This stores the key used for the encryption of all the blocks. The key itself
// is stored in the encrypted form. A user supplies a password - it is used
// together with salt and rounds to generate a decryption key for the actual
// key used for block encryption. This way we can change the password without
// re-encrypting all the blocks
message EncryptionKeyInfo
{
  // The decryption key is derived from the password, salt and rounds using
  // PKCS5_PBKDF2_HMAC_SHA1

  // Salt to use together with the user password
  required bytes salt = 1;
  // Rounds of hashing to apply when generating the key used to decrypt the
  // block key
  required uint32 rounds = 2;
  // Stores the block encryption key, in an encrypted form itself
  required bytes encrypted_key = 3;
  // Used to check that the key was decrypted correctly - see the next field
  required bytes key_check_input = 4;
  // HMAC of key_check_input using the decrypted key. Used to check that the
  // key was indeed decrypted correctly
  required bytes key_check_hmac = 5;
}

message StorageInfo
{
  // Maximum chunk size used when storing chunks
  optional uint32 chunk_max_size = 1 [deprecated = true];
  // Maximum number of bytes a bundle can hold. Only real chunk bytes are
  // counted, not metadata. Any bundle should be able to contain at least
  // one arbitrary single chunk, so this should not be smaller than
  // chunk_max_size
  optional uint32 bundle_max_payload_size = 2 [deprecated = true];
  // If present, used for encryption/decryption of all data
  optional EncryptionKeyInfo encryption_key = 3;
  // Default compression for new bundles
  optional string default_compression_method = 4 [default = "lzma", deprecated = true];
}

message LZMAConfigInfo
{
  // Compression level for new LZMA-compressed files
  optional uint32 compression_level = 1 [default = 6];
}

message ChunkConfigInfo
{
  // Maximum chunk size used when storing chunks
  required uint32 max_size = 1 [default = 65536];
}

message BundleConfigInfo
{
  // Maximum number of bytes a bundle can hold. Only real chunk bytes are
  // counted, not metadata. Any bundle should be able to contain at least
  // one arbitrary single chunk, so this should not be smaller than
  // chunk_max_size
  required uint32 max_payload_size = 2 [default = 0x200000];
  // Compression method for new bundles
  optional string compression_method = 3 [default = "lzma"];
}

// Storable config values should always have default values
message ConfigInfo
{
  required ChunkConfigInfo chunk = 1;
  required BundleConfigInfo bundle = 2;
  required LZMAConfigInfo lzma = 3;
}

message ExtendedStorageInfo
{
  // Config data storage
  optional ConfigInfo config = 1;
}

message BundleInfo
{
  // Info about a single chunk stored
  message ChunkRecord
  {
    // Id of the chunk
    required bytes id = 1;
    // Size of the chunk
    required uint32 size = 2;
  }

  // A sequence of chunk records
  repeated ChunkRecord chunk_record = 1;
}

message FileHeader
{
  // File format version
  required uint32 version = 1;
}

message BundleFileHeader
{
  // File format version
  required uint32 version = 1;

  // Compression method that is used for this file
  // If the program doesn't support that field, it will try LZMA. If it is
  // LZMA, that will work. If it isn't, it will have aborted before because
  // the version in FileHeader is higher than it can support.
  optional string compression_method = 2 [default = "lzma"];
}

message IndexBundleHeader
{
  // Id of the bundle following in the stream. If not present, indicates the
  // end of log file
  optional bytes id = 1;
}

// A single instruction. Backups are made of a sequence of those instructions,
// which are executed one after another
message BackupInstruction
{
  // Both fields can present simultaneously. They are evaluated in the same
  // order they are listed here

  // If present, the chunk with that id should be emitted to the data flow
  optional bytes chunk_to_emit = 1;
  // If present, the bytes contained in the field should be emitted to the
  // data flow
  optional bytes bytes_to_emit = 2;
}

message BackupInfo
{
  // The backup data. Since usually the field is quite large for real life
  /// backups, we process its serialized data with the same backup algorithm
  // iteratively until it doesn't shrink. The content of this field represents
  // the last iteration of that process. If iterations = 0, it directly
  // represents the user's backup data. If iterations = 1, it represents the
  // backed up BackupData which would represent the user's backed up data once
  // it is restored, and so on.
  // The type is 'bytes' as the result is serialized
  required bytes backup_data = 1;

  // Number of times backup_data should be restored with the 'restore' algorithm
  // before we get what we need to restore for the end user
  optional uint32 iterations = 2 [default = 0];

  // Number of bytes in the backup data
  required uint64 size = 3;

  // SHA-256 of the original data
  required bytes sha256 = 4;

  // Time spent creating the backup, in seconds
  optional int64 time = 5;
}