path: root/tvix/store/protos/pathinfo.proto

// SPDX-License-Identifier: MIT
// Copyright © 2022 The Tvix Authors
syntax = "proto3";

package tvix.store.v1;

import "tvix/castore/protos/castore.proto";

option go_package = "code.tvl.fyi/tvix/store-go;storev1";

// PathInfo shows information about a Nix Store Path.
// That's a single element inside /nix/store.
message PathInfo {
    // The path can be a directory, file or symlink.
    tvix.castore.v1.Node node = 1;

    // List of references (output path hashes)
    // This really is the raw *bytes*, after decoding nixbase32, and not a
    // base32-encoded string.
    repeated bytes references = 2;

    // see below.
    NARInfo narinfo = 3;
}

// Represents a path in the Nix store (a direct child of STORE_DIR).
// It is commonly formatted by a nixbase32-encoding the digest, and
// concatenating the name, separated by a `-`.
message StorePath {
    // The string after digest and `-`.
    string name = 1;

    // The digest (20 bytes).
    bytes digest = 2;
}

// Nix C++ uses NAR (Nix Archive) as a format to transfer store paths,
// and stores metadata and signatures in NARInfo files.
// Store all these attributes in a separate message.
//
// This is useful to render .narinfo files to clients, or to preserve/validate
// these signatures.
// As verifying these signatures requires the whole NAR file to be synthesized,
// moving to another signature scheme is desired.
// Even then, it still makes sense to hold this data, for old clients.
message NARInfo {
    // This represents a (parsed) signature line in a .narinfo file.
    message Signature {
        string name = 1;
        bytes data = 2;
    };

    // This size of the NAR file, in bytes.
    uint64 nar_size = 1;

    // The sha256 of the NAR file representation.
    bytes nar_sha256 = 2;

    // The signatures in a .narinfo file.
    repeated Signature signatures = 3;

    // A list of references. To validate .narinfo signatures, a fingerprint
    // needs to be constructed.
    // This fingerprint doesn't just contain the hashes of the output paths of
    // all references (like PathInfo.references), but their whole (base)names,
    // so we need to keep them somewhere.
    repeated string reference_names = 4;

    // The StorePath of the .drv file producing this output.
    // The .drv suffix is omitted in its `name` field.
    StorePath deriver = 5;

    // The CA field in the .narinfo.
    // Its textual representations seen in the wild are one of the following:
    //  - `fixed:r:sha256:1gcky5hlf5vqfzpyhihydmm54grhc94mcs8w7xr8613qsqb1v2j6`
    //    fixed-output derivations using "recursive" `outputHashMode`.
    //  - `fixed:sha256:19xqkh72crbcba7flwxyi3n293vav6d7qkzkh2v4zfyi4iia8vj8
    //    fixed-output derivations using "flat" `outputHashMode`
    //  - `text:sha256:19xqkh72crbcba7flwxyi3n293vav6d7qkzkh2v4zfyi4iia8vj8`
    //    Text hashing, used for uploaded .drv files and outputs produced by
    //    builtins.toFile.
    //
    // Semantically, they can be split into the following components:
    //  - "content address prefix". Currently, "fixed" and "text" are supported.
    //  - "hash mode". Currently, "flat" and "recursive" are supported.
    //  - "hash type". The underlying hash function used.
    //    Currently, sha1, md5, sha256, sha512.
    //  - "digest". The digest itself.
    //
    // There are some restrictions on the possible combinations.
    // For example, `text` and `fixed:recursive` always imply sha256.
    //
    // We use an enum to encode the possible combinations, and optimize
    // for the common case, `fixed:recursive`, identified as `NAR_SHA256`.
    CA ca = 6;

    message CA {
        enum Hash {
            // produced when uploading fixed-output store paths using NAR-based
            // hashing (`outputHashMode = "recursive"`).
            NAR_SHA256 = 0;
            NAR_SHA1 = 1;
            NAR_SHA512 = 2;
            NAR_MD5 = 3;

            // Produced when uploading .drv files or outputs produced by
            // builtins.toFile.
            // Produces equivalent digests as FLAT_SHA256, but is a separate
            // hashing type in Nix, affecting output path calculation.
            TEXT_SHA256 = 4;

            // Produced when using fixed-output derivations with
            // `outputHashMode = "flat"`.
            FLAT_SHA1 = 5;
            FLAT_MD5 = 6;
            FLAT_SHA256 = 7;
            FLAT_SHA512 = 8;

            // TODO: what happens in Rust if we introduce a new enum kind here?
        }

        // The hashing type used.
        Hash type = 1;

        // The digest, in raw bytes.
        bytes digest = 2;
    }
}