tiny.reticulum.destination.cipher

1const std = @import("std");2const reticulum = @import("../root.zig");34const crypto = reticulum.crypto;5const destination = reticulum.destination;6const identity = reticulum.identity;78/// 383 bytes, the most plaintext one packet to a single-identity destination9/// carries, which the reference fixes as10/// `floor((464 - 48 - 32) / 16) * 16 - 1`, so a caller sizes the payload it can11/// send to one identity, following Reticulum@1.5.0 RNS/Packet.py:106.12pub const encrypted_mdu: u16 = 383;13/// 464 bytes, the most payload a packet to a plain destination carries, so a14/// caller sizes the payload it can send to a plain destination, following15/// Reticulum@1.5.0 RNS/Packet.py:110 and Reticulum@1.5.016/// RNS/Reticulum.py:148-155.17pub const plain_mdu: u16 = reticulum.wire.mtu - reticulum.wire.header_two_bytes - 1;1819pub const SingleEncrypt = struct {20    public: *const identity.Public,21    ratchet_public: ?*const [32]u8,22    ephemeral_private: *const [32]u8,23    iv: [crypto.token.iv_length]u8,24};2526pub const GroupEncrypt = struct {27    key: *const [64]u8,28    iv: [crypto.token.iv_length]u8,29};3031pub const EncryptKeys = union(destination.Type) {32    single: SingleEncrypt,33    group: GroupEncrypt,34    plain: void,35    link: void,36};3738pub const SingleDecrypt = struct {39    private: *const identity.Private,40    ratchets: []const identity.Ratchet,41    enforce_ratchets: bool,42};4344pub const GroupDecrypt = struct {45    key: *const [64]u8,46};4748pub const DecryptKeys = union(destination.Type) {49    single: SingleDecrypt,50    group: GroupDecrypt,51    plain: void,52    link: void,53};5455pub const EncryptError = identity.cipher.EncryptError || error{Unsupported};56pub const DecryptError = identity.cipher.DecryptError || error{Unsupported};5758pub const Encrypted = struct {59    ciphertext: []u8,60    ratchet_id: ?[reticulum.hash.name_bytes]u8,61};6263pub const Decrypted = struct {64    plaintext: []u8,65    ratchet_id: ?[reticulum.hash.name_bytes]u8,66};6768fn copy(input: []const u8, out: []u8) error{OutputTooSmall}![]u8 {69    if (out.len < input.len) return error.OutputTooSmall;70    @memmove(out[0..input.len], input);71    return out[0..input.len];72}7374/// Seals a payload into `out` by the kind of destination the keys name, so a75/// caller seals for whichever kind it is sending to without writing the choice76/// out itself, and reports the rotating key it used when it used one, following77/// Reticulum@1.5.0 RNS/Destination.py:596-617. A plain destination takes a copy78/// of the payload, a single-identity destination takes the ephemeral-key79/// exchange, and a group takes a sealed token under the shared 64-byte key.80/// Sending to a link returns `error.Unsupported`, because a link seals its81/// payloads with the key the two ends already agreed on. The call returns82/// `error.OutputTooSmall` when `out` is shorter than the result, and the errors83/// the single-identity path raises.84pub fn encrypt(keys: EncryptKeys, plaintext: []const u8, out: []u8) EncryptError!Encrypted {85    return switch (keys) {86        .plain => .{ .ciphertext = try copy(plaintext, out), .ratchet_id = null },87        .single => |single| blk: {88            const ciphertext = try identity.cipher.encrypt(89                single.public,90                single.ratchet_public,91                single.ephemeral_private,92                single.iv,93                plaintext,94                out,95            );96            const ratchet_id = if (single.ratchet_public) |public|97                reticulum.hash.name(public)98            else99                null;100            break :blk .{ .ciphertext = ciphertext, .ratchet_id = ratchet_id };101        },102        .group => |group| blk: {103            const token = crypto.token.Token.init(group.key) catch unreachable;104            const ciphertext = try token.encrypt(group.iv, plaintext, out);105            break :blk .{ .ciphertext = ciphertext, .ratchet_id = null };106        },107        .link => error.Unsupported,108    };109}110111fn decryptGroup(group: GroupDecrypt, ciphertext: []const u8, out: []u8) DecryptError![]u8 {112    const token = crypto.token.Token.init(group.key) catch unreachable;113    return token.decrypt(ciphertext, out) catch |err| switch (err) {114        error.OutputTooSmall => error.OutputTooSmall,115        else => error.InvalidToken,116    };117}118119/// Opens a payload into `out` by the kind of destination the keys name, so a120/// caller opens an arriving payload by the kind it was addressed to, and121/// reports the rotating key that opened it when one did, following122/// Reticulum@1.5.0 RNS/Destination.py:622-665. A plain destination takes a copy123/// of the payload, a single-identity destination walks its retained keys and124/// then its identity key, and a group opens a sealed token under the shared125/// 64-byte key. A payload addressed to a link returns `error.Unsupported`. A126/// group payload that fails its tag check returns `error.InvalidToken`.127pub fn decrypt(keys: DecryptKeys, ciphertext: []const u8, out: []u8) DecryptError!Decrypted {128    return switch (keys) {129        .plain => .{ .plaintext = try copy(ciphertext, out), .ratchet_id = null },130        .single => |single| blk: {131            const result = try identity.cipher.decrypt(132                single.private,133                single.ratchets,134                single.enforce_ratchets,135                ciphertext,136                out,137            );138            break :blk .{139                .plaintext = result.plaintext,140                .ratchet_id = result.ratchet_id,141            };142        },143        .group => |group| .{144            .plaintext = try decryptGroup(group, ciphertext, out),145            .ratchet_id = null,146        },147        .link => error.Unsupported,148    };149}150151comptime {152    std.debug.assert(plain_mdu == 464);153}

1pub const cipher = @import("cipher.zig");