Include license and readme in build output

This is probably required for GPL compliance :-D

.tangled/workflows/build.yml

@@ -0,0 +1,26 @@
+when:
+  - event: ["push", "pull_request", "manual"]
+    branch: ["dev", "master", "test*"]
+    tag: ["v*"]
+
+engine: "nixery"
+
+dependencies:
+  nixpkgs:
+    - rclone
+  git+https://github.com/mitchellh/zig-overlay:
+    - master
+
+steps:
+  - name: "Build"
+    command: "zig build -Doptimize=ReleaseSmall -Dcpu=baseline"
+  - name: "Publish"
+    command: |
+      rclone sync ./zig-out \
+        --webdav-url "$RELEASE_NEXTCLOUD_HOST/remote.php/dav/files/$RELEASE_NEXTCLOUD_USER/" \
+        --webdav-user "$RELEASE_NEXTCLOUD_USER" \
+        --webdav-pass "$RELEASE_NEXTCLOUD_PASS" \
+        --webdav-vendor nextcloud \
+        :webdav:"zaprus/zaprus-$TANGLED_REF_NAME" \
+        -q
+

LICENSE.md

@@ -0,0 +1,676 @@
+# GNU GENERAL PUBLIC LICENSE
+
+Version 3, 29 June 2007
+
+Copyright (C) 2007 Free Software Foundation, Inc.
+<https://fsf.org/>
+
+Everyone is permitted to copy and distribute verbatim copies of this
+license document, but changing it is not allowed.
+
+## Preamble
+
+The GNU General Public License is a free, copyleft license for
+software and other kinds of works.
+
+The licenses for most software and other practical works are designed
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+free software for all its users. We, the Free Software Foundation, use
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+also to any other work released this way by its authors. You can apply
+it to your programs, too.
+
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+Nothing in this License shall be construed as excluding or limiting
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+
+### 12. No Surrender of Others' Freedom.
+
+If conditions are imposed on you (whether by court order, agreement or
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+
+### 13. Use with the GNU Affero General Public License.
+
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+
+### 14. Revised Versions of this License.
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+### 15. Disclaimer of Warranty.
+
+THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT
+WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND
+PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE
+DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR
+CORRECTION.
+
+### 16. Limitation of Liability.
+
+IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR
+CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
+INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES
+ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT
+NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR
+LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM
+TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER
+PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
+
+### 17. Interpretation of Sections 15 and 16.
+
+If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+END OF TERMS AND CONDITIONS
+
+## How to Apply These Terms to Your New Programs
+
+If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these
+terms.
+
+To do so, attach the following notices to the program. It is safest to
+attach them to the start of each source file to most effectively state
+the exclusion of warranty; and each file should have at least the
+"copyright" line and a pointer to where the full notice is found.
+
+        <one line to give the program's name and a brief idea of what it does.>
+        Copyright (C) <year>  <name of author>
+
+        This program is free software: you can redistribute it and/or modify
+        it under the terms of the GNU General Public License as published by
+        the Free Software Foundation, either version 3 of the License, or
+        (at your option) any later version.
+
+        This program is distributed in the hope that it will be useful,
+        but WITHOUT ANY WARRANTY; without even the implied warranty of
+        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+        GNU General Public License for more details.
+
+        You should have received a copy of the GNU General Public License
+        along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper
+mail.
+
+If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+        <program>  Copyright (C) <year>  <name of author>
+        This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+        This is free software, and you are welcome to redistribute it
+        under certain conditions; type `show c' for details.
+
+The hypothetical commands \`show w' and \`show c' should show the
+appropriate parts of the General Public License. Of course, your
+program's commands might be different; for a GUI interface, you would
+use an "about box".
+
+You should also get your employer (if you work as a programmer) or
+school, if any, to sign a "copyright disclaimer" for the program, if
+necessary. For more information on this, and how to apply and follow
+the GNU GPL, see <https://www.gnu.org/licenses/>.
+
+The GNU General Public License does not permit incorporating your
+program into proprietary programs. If your program is a subroutine
+library, you may consider it more useful to permit linking proprietary
+applications with the library. If this is what you want to do, use the
+GNU Lesser General Public License instead of this License. But first,
+please read <https://www.gnu.org/licenses/why-not-lgpl.html>.
+

README.md

@@ -0,0 +1,11 @@
+# zaprus
+
+This is an implementation of the [Saprus protocol](https://gitlab.com/c2-games/red-team/saprus) in Zig.
+It is useful for developing clients either in Zig, or in any other language using the C bindings.
+
+Binary releases can be downloaded [here](https://cloud.zambito.xyz/s/7jJPTm68Zp3mN8F).
+
+The code for this can be found here:
+
+- https://tangled.org/zambyte.robbyzambito.me/zaprus
+- https://git.robbyzambito.me/zaprus

build.zig

@@ -7,6 +7,9 @@ const std = @import("std");
 // build runner to parallelize the build automatically (and the cache system to
 // know when a step doesn't need to be re-run).
 pub fn build(b: *std.Build) void {
+    // Ensure the license is included in the output directory
+    b.installFile("LICENSE.md", "LICENSE.md");
+    b.installFile("README.md", "README.md");
     // Standard target options allow the person running `zig build` to choose
     // what target to build for. Here we do not override the defaults, which
     // means any target is allowed, and the default is native. Other options
@@ -21,6 +24,9 @@ pub fn build(b: *std.Build) void {
     // target and optimize options) will be listed when running `zig build --help`
     // in this directory.
 
+    // Get default install step (called with `zig build` or `zig build install`)
+    const install_step = b.getInstallStep();
+
     // This creates a module, which represents a collection of source files alongside
     // some compilation options, such as optimization mode and linked system libraries.
     // Zig modules are the preferred way of making Zig code available to consumers.
@@ -41,6 +47,22 @@ pub fn build(b: *std.Build) void {
         .target = target,
     });
 
+    // Only used to generate the documentation
+    const zaprus_lib = b.addLibrary(.{
+        .name = "zaprus",
+        .root_module = mod,
+    });
+
+    const docs_step = b.step("doc", "Emit documentation");
+    const docs_install = b.addInstallDirectory(.{
+        .install_dir = .prefix,
+        .install_subdir = "docs",
+        .source_dir = zaprus_lib.getEmittedDocs(),
+    });
+
+    docs_step.dependOn(&docs_install.step);
+    install_step.dependOn(docs_step);
+
     // Create static library
     const lib = b.addLibrary(.{
         .name = "zaprus",

include/zaprus.h

@@ -1,3 +1,13 @@
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with Zaprus. If not, see <https://www.gnu.org/licenses/>. 
+
 #ifndef ZAPRUS_H
 #define ZAPRUS_H
 

src/Client.zig

@@ -1,3 +1,21 @@
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
+
+//! A client is used to handle interactions with the network.
+
 const base64_enc = std.base64.standard.Encoder;
 const base64_dec = std.base64.standard.Decoder;
 
@@ -21,6 +39,8 @@ pub fn deinit(self: *Client) void {
     self.* = undefined;
 }
 
+/// Sends a fire and forget message over the network.
+/// This function asserts that `payload` fits within a single packet.
 pub fn sendRelay(self: *Client, io: Io, payload: []const u8, dest: [4]u8) !void {
     const io_source: std.Random.IoSource = .{ .io = io };
     const rand = io_source.interface();
@@ -60,7 +80,8 @@ pub fn sendRelay(self: *Client, io: Io, payload: []const u8, dest: [4]u8) !void
     try self.socket.send(full_msg);
 }
 
-pub fn connect(self: Client, io: Io, payload: []const u8) !SaprusConnection {
+/// Attempts to establish a new connection with the sentinel.
+pub fn connect(self: Client, io: Io, payload: []const u8) (error{ BpfAttachFailed, Timeout } || SaprusMessage.ParseError)!SaprusConnection {
     const io_source: std.Random.IoSource = .{ .io = io };
     const rand = io_source.interface();
 
@@ -84,7 +105,7 @@ pub fn connect(self: Client, io: Io, payload: []const u8) !SaprusConnection {
     var connection: SaprusMessage = .{
         .connection = .{
             .src = rand.intRangeAtMost(u16, 1025, std.math.maxInt(u16)),
-            .dest = rand.intRangeAtMost(u16, 1025, std.math.maxInt(u16)),
+            .dest = rand.intRangeAtMost(u16, 1025, std.math.maxInt(u16)), // Ignored, but good noise
             .seq = undefined,
             .id = undefined,
             .payload = payload,
@@ -92,7 +113,7 @@ pub fn connect(self: Client, io: Io, payload: []const u8) !SaprusConnection {
     };
 
     log.debug("Setting bpf filter to port {}", .{connection.connection.src});
-    self.socket.attachSaprusPortFilter(connection.connection.src) catch |err| {
+    self.socket.attachSaprusPortFilter(null, connection.connection.src) catch |err| {
         log.err("Failed to set port filter: {t}", .{err});
         return err;
     };
@@ -115,7 +136,17 @@ pub fn connect(self: Client, io: Io, payload: []const u8) !SaprusConnection {
 
     log.debug("Awaiting handshake response", .{});
     // Ignore response from sentinel, just accept that we got one.
-    _ = try self.socket.receive(&res_buf);
+    const full_handshake_res = try self.socket.receive(&res_buf);
+    const handshake_res = saprusParse(full_handshake_res[42..]) catch |err| {
+        log.err("Parse error: {t}", .{err});
+        return err;
+    };
+    self.socket.attachSaprusPortFilter(handshake_res.connection.src, handshake_res.connection.dest) catch |err| {
+        log.err("Failed to set port filter: {t}", .{err});
+        return err;
+    };
+    connection.connection.dest = handshake_res.connection.src;
+    connection_bytes = connection.toBytes(&connection_buf);
 
     headers.udp.dst_port = udp_dest_port;
     headers.ip.id = rand.int(u16);
@@ -131,12 +162,17 @@ pub fn connect(self: Client, io: Io, payload: []const u8) !SaprusConnection {
 
     try self.socket.send(full_msg);
 
-    return .init(self.socket, headers, connection);
+    return .{
+        .socket = self.socket,
+        .headers = headers,
+        .connection = connection,
+    };
 }
 
 const RawSocket = @import("./RawSocket.zig");
 
 const SaprusMessage = @import("message.zig").Message;
+const saprusParse = SaprusMessage.parse;
 const SaprusConnection = @import("Connection.zig");
 const EthIpUdp = @import("./EthIpUdp.zig").EthIpUdp;
 

src/Connection.zig

@@ -1,36 +1,80 @@
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
+
 socket: RawSocket,
 headers: EthIpUdp,
 connection: SaprusMessage,
 
 const Connection = @This();
 
-pub fn init(socket: RawSocket, headers: EthIpUdp, connection: SaprusMessage) Connection {
+// 'p' as base64
-    return .{
+const pong = "cA==";
-        .socket = socket,
-        .headers = headers,
-        .connection = connection,
-    };
-}
 
-pub fn next(self: Connection, io: Io, buf: []u8) ![]const u8 {
+/// Attempts to read from the network, and returns the next message, if any.
-    _ = io;
+///
+/// Asserts that `buf` is large enough to store the message that is received.
+///
+/// This will internally process management messages, and return the message
+/// payload for the next non management connection message.
+/// This function is ignorant to the message encoding.
+pub fn next(self: *Connection, io: Io, buf: []u8) ![]const u8 {
+    while (true) {
         log.debug("Awaiting connection message", .{});
         const res = try self.socket.receive(buf);
         log.debug("Received {} byte connection message", .{res.len});
-    const msg: SaprusMessage = try .parse(res[42..]);
+        const msg = SaprusMessage.parse(res[42..]) catch |err| {
-    const connection_res = msg.connection;
+            log.err("Failed to parse next message: {t}\n{x}\n{x}", .{ err, res[0..], res[42..] });
+            return err;
+        };
 
-    log.debug("Payload was {s}", .{connection_res.payload});
+        switch (msg) {
-
+            .connection => |con_res| {
-    return connection_res.payload;
+                if (try con_res.management()) |mgt| {
+                    log.debug("Received management message {t}", .{mgt});
+                    switch (mgt) {
+                        .ping => {
+                            log.debug("Sending pong", .{});
+                            try self.send(io, .{ .management = true }, pong);
+                            log.debug("Sent pong message", .{});
+                        },
+                        else => |m| log.debug("Received management message that I don't know how to handle: {t}", .{m}),
+                    }
+                } else {
+                    log.debug("Payload was {s}", .{con_res.payload});
+                    return con_res.payload;
+                }
+            },
+            else => |m| {
+                std.debug.panic("Expected connection message, instead got {x}. This means there is an error with the BPF.", .{@intFromEnum(m)});
+            },
+        }
+    }
 }
 
-pub fn send(self: *Connection, io: Io, buf: []const u8) !void {
+/// Attempts to write a message to the network.
+///
+/// Clients should pass `.{}` for options unless you know what you are doing.
+/// `buf` will be sent over the network as-is; this function is ignorant of encoding.
+pub fn send(self: *Connection, io: Io, options: SaprusMessage.Connection.Options, buf: []const u8) !void {
     const io_source: std.Random.IoSource = .{ .io = io };
     const rand = io_source.interface();
 
     log.debug("Sending connection message", .{});
 
+    self.connection.connection.options = options;
     self.connection.connection.payload = buf;
     var connection_bytes_buf: [2048]u8 = undefined;
     const connection_bytes = self.connection.toBytes(&connection_bytes_buf);

src/EthIpUdp.zig

@@ -1,3 +1,19 @@
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
+
 pub const EthIpUdp = packed struct(u336) { // 42 bytes * 8 bits = 336
     // --- UDP (Last in memory, defined first for LSB->MSB) ---
     udp: packed struct {

src/RawSocket.zig

@@ -1,3 +1,19 @@
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
+
 const RawSocket = @This();
 
 const is_debug = builtin.mode == .Debug;
@@ -16,7 +32,12 @@ const Ifconf = extern struct {
     },
 };
 
-pub fn init() !RawSocket {
+pub fn init() error{
+    SocketError,
+    NicError,
+    NoInterfaceFound,
+    BindError,
+}!RawSocket {
     const socket: i32 = std.math.cast(i32, std.os.linux.socket(std.os.linux.AF.PACKET, std.os.linux.SOCK.RAW, 0)) orelse return error.SocketError;
     if (socket < 0) return error.SocketError;
 
@@ -117,7 +138,7 @@ pub fn receive(self: RawSocket, buf: []u8) ![]u8 {
     return buf[0..len];
 }
 
-pub fn attachSaprusPortFilter(self: RawSocket, port: u16) !void {
+pub fn attachSaprusPortFilter(self: RawSocket, incoming_src_port: ?u16, incoming_dest_port: u16) !void {
     const BPF = std.os.linux.BPF;
     // BPF instruction structure for classic BPF
     const SockFilter = extern struct {
@@ -133,11 +154,26 @@ pub fn attachSaprusPortFilter(self: RawSocket, port: u16) !void {
     };
 
     // Build the filter program
-    const filter = [_]SockFilter{
+    const filter = if (incoming_src_port) |inc_src| &[_]SockFilter{
         // Load 2 bytes at offset 46 (absolute)
         .{ .code = BPF.LD | BPF.H | BPF.ABS, .jt = 0, .jf = 0, .k = 46 },
+        // Jump if equal to port (skip 1 if true, skip 0 if false)
+        .{ .code = BPF.JMP | BPF.JEQ | BPF.K, .jt = 1, .jf = 0, .k = @as(u32, inc_src) },
+        // Return 0x0 (fail)
+        .{ .code = BPF.RET | BPF.K, .jt = 0, .jf = 0, .k = 0x0 },
+        // Load 2 bytes at offset 48 (absolute)
+        .{ .code = BPF.LD | BPF.H | BPF.ABS, .jt = 0, .jf = 0, .k = 48 },
         // Jump if equal to port (skip 0 if true, skip 1 if false)
-        .{ .code = BPF.JMP | BPF.JEQ | BPF.K, .jt = 0, .jf = 1, .k = @as(u32, port) },
+        .{ .code = BPF.JMP | BPF.JEQ | BPF.K, .jt = 0, .jf = 1, .k = @as(u32, incoming_dest_port) },
+        // Return 0xffff (pass)
+        .{ .code = BPF.RET | BPF.K, .jt = 0, .jf = 0, .k = 0xffff },
+        // Return 0x0 (fail)
+        .{ .code = BPF.RET | BPF.K, .jt = 0, .jf = 0, .k = 0x0 },
+    } else &[_]SockFilter{
+        // Load 2 bytes at offset 48 (absolute)
+        .{ .code = BPF.LD | BPF.H | BPF.ABS, .jt = 0, .jf = 0, .k = 48 },
+        // Jump if equal to port (skip 0 if true, skip 1 if false)
+        .{ .code = BPF.JMP | BPF.JEQ | BPF.K, .jt = 0, .jf = 1, .k = @as(u32, incoming_dest_port) },
         // Return 0xffff (pass)
         .{ .code = BPF.RET | BPF.K, .jt = 0, .jf = 0, .k = 0xffff },
         // Return 0x0 (fail)
@@ -145,8 +181,8 @@ pub fn attachSaprusPortFilter(self: RawSocket, port: u16) !void {
     };
 
     const fprog = SockFprog{
-        .len = filter.len,
+        .len = @intCast(filter.len),
-        .filter = &filter,
+        .filter = filter.ptr,
     };
 
     // Attach filter to socket using setsockopt

src/c_api.zig

@@ -1,3 +1,19 @@
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
+
 const std = @import("std");
 const zaprus = @import("zaprus");
 
@@ -83,6 +99,6 @@ export fn zaprus_connection_send(
     const c: ?*zaprus.Connection = @ptrCast(@alignCast(connection));
     const zc = c orelse return 1;
 
-    zc.send(io, payload[0..payload_len]) catch return 1;
+    zc.send(io, .{}, payload[0..payload_len]) catch return 1;
     return 0;
 }

src/main.zig

@@ -1,3 +1,19 @@
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
+
 const is_debug = builtin.mode == .Debug;
 
 const help =
@@ -157,35 +173,89 @@ pub fn main(init: std.process.Init) !void {
                     continue;
                 };
 
-                const child = std.process.spawn(init.io, .{
+                var child = std.process.spawn(init.io, .{
                     .argv = &.{ "bash", "-c", connection_payload },
                     .stdout = .pipe,
-                    .stderr = .pipe,
+                    .stderr = .ignore,
+                    .stdin = .ignore,
+                }) catch |err| switch (err) {
+                    error.AccessDenied,
+                    error.FileBusy,
+                    error.FileNotFound,
+                    error.FileSystem,
+                    error.InvalidExe,
+                    error.IsDir,
+                    error.NotDir,
+                    error.OutOfMemory,
+                    error.PermissionDenied,
+                    error.SymLinkLoop,
+                    error.SystemResources,
+                    => blk: {
+                        log.debug("Trying to execute command directly: {s}", .{connection_payload});
+                        var argv_buf: [128][]const u8 = undefined;
+                        var argv: ArrayList([]const u8) = .initBuffer(&argv_buf);
+                        var payload_iter = std.mem.splitAny(u8, connection_payload, " \t\n");
+                        while (payload_iter.next()) |arg| argv.appendBounded(arg) catch continue;
+                        break :blk std.process.spawn(init.io, .{
+                            .argv = argv.items,
+                            .stdout = .pipe,
+                            .stderr = .ignore,
+                            .stdin = .ignore,
                         }) catch continue;
-
+                    },
-                var child_stdout: std.ArrayList(u8) = .empty;
+                    error.Canceled,
-                defer child_stdout.deinit(init.gpa);
+                    error.NoDevice,
-                var child_stderr: std.ArrayList(u8) = .empty;
+                    error.OperationUnsupported,
-                defer child_stderr.deinit(init.gpa);
+                    => |e| return e,
-
+                    else => continue,
-                child.collectOutput(init.gpa, &child_stdout, &child_stderr, std.math.maxInt(usize)) catch |err| {
-                    log.debug("Failed to collect output: {t}", .{err});
-                    continue;
                 };
 
+                var child_output_buf: [SaprusClient.max_payload_len]u8 = undefined;
+                var child_output_reader = child.stdout.?.reader(init.io, &child_output_buf);
+
+                var is_killed: std.atomic.Value(bool) = .init(false);
+
+                var kill_task = try init.io.concurrent(killProcessAfter, .{ init.io, &child, .fromSeconds(3), &is_killed });
+                defer _ = kill_task.cancel(init.io) catch {};
+
                 var cmd_output_buf: [SaprusClient.max_payload_len * 2]u8 = undefined;
                 var cmd_output: Writer = .fixed(&cmd_output_buf);
 
-                var cmd_output_window_iter = std.mem.window(u8, child_stdout.items, SaprusClient.max_payload_len, SaprusClient.max_payload_len);
+                // Maximum of 10 messages of output per command
-                while (cmd_output_window_iter.next()) |chunk| {
+                for (0..10) |_| {
                     cmd_output.end = 0;
-                    // Unreachable because the cmd_output_buf is twice the size of the chunk.
+
-                    cmd_output.print("{b64}", .{chunk}) catch unreachable;
+                    child_output_reader.interface.fill(child_output_reader.interface.buffer.len) catch |err| switch (err) {
-                    connection.send(init.io, cmd_output.buffered()) catch |err| {
+                        error.ReadFailed => continue :next_message, // TODO: check if there is a better way to handle this
+                        error.EndOfStream => {
+                            cmd_output.print("{b64}", .{child_output_reader.interface.buffered()}) catch unreachable;
+                            if (cmd_output.end > 0) {
+                                connection.send(init.io, .{}, cmd_output.buffered()) catch |e| {
+                                    log.debug("Failed to send connection chunk: {t}", .{e});
+                                    continue :next_message;
+                                };
+                            }
+                            break;
+                        },
+                    };
+                    cmd_output.print("{b64}", .{try child_output_reader.interface.takeArray(child_output_buf.len)}) catch unreachable;
+                    connection.send(init.io, .{}, cmd_output.buffered()) catch |err| {
                         log.debug("Failed to send connection chunk: {t}", .{err});
                         continue :next_message;
                     };
                     try init.io.sleep(.fromMilliseconds(40), .boot);
+                } else {
+                    kill_task.cancel(init.io) catch {};
+                    killProcessAfter(init.io, &child, .zero, &is_killed) catch |err| {
+                        log.debug("Failed to kill process??? {t}", .{err});
+                        continue :next_message;
+                    };
+                }
+
+                if (!is_killed.load(.monotonic)) {
+                    _ = child.wait(init.io) catch |err| {
+                        log.debug("Failed to wait for child: {t}", .{err});
+                    };
                 }
             }
         }
@@ -194,6 +264,15 @@ pub fn main(init: std.process.Init) !void {
     unreachable;
 }
 
+fn killProcessAfter(io: std.Io, proc: *std.process.Child, duration: std.Io.Duration, is_killed: *std.atomic.Value(bool)) !void {
+    io.sleep(duration, .boot) catch |err| switch (err) {
+        error.Canceled => return,
+        else => |e| return e,
+    };
+    is_killed.store(true, .monotonic);
+    proc.kill(io);
+}
+
 fn parseDest(in: ?[]const u8) [4]u8 {
     if (in) |dest| {
         if (dest.len <= 4) {

src/message.zig

@@ -1,34 +1,141 @@
-pub const MessageTypeError = error{
+// Copyright 2026 Robby Zambito
-    NotImplementedSaprusType,
+//
-    UnknownSaprusType,
+// This file is part of zaprus.
-};
+//
-pub const MessageParseError = MessageTypeError || error{
+// Zaprus is free software: you can redistribute it and/or modify it under the
-    InvalidMessage,
+// terms of the GNU General Public License as published by the Free Software
-};
+// Foundation, either version 3 of the License, or (at your option) any later
-
+// version.
-const message = @This();
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
 
 pub const Message = union(enum(u16)) {
     relay: Message.Relay = 0x003C,
     connection: Message.Connection = 0x00E9,
     _,
 
-    pub const Relay = message.Relay;
+    pub const Relay = struct {
-    pub const Connection = message.Connection;
+        dest: Dest,
+        checksum: [2]u8 = undefined,
+        payload: []const u8,
 
-    pub fn toBytes(self: message.Message, buf: []u8) []u8 {
+        pub const Dest = struct {
+            bytes: [relay_dest_len]u8,
+
+            /// Asserts bytes is less than or equal to 4 bytes
+            pub fn fromBytes(bytes: []const u8) Dest {
+                var buf: [4]u8 = @splat(0);
+                std.debug.assert(bytes.len <= buf.len);
+                @memcpy(buf[0..bytes.len], bytes);
+                return .{ .bytes = buf };
+            }
+        };
+
+        /// Asserts that buf is large enough to fit the relay message.
+        pub fn toBytes(self: Relay, buf: []u8) []u8 {
+            var out: Writer = .fixed(buf);
+            out.writeInt(u16, @intFromEnum(Message.relay), .big) catch unreachable;
+            out.writeInt(u16, @intCast(self.payload.len + 4), .big) catch unreachable; // Length field, but unread. Will switch to checksum
+            out.writeAll(&self.dest.bytes) catch unreachable;
+            out.writeAll(self.payload) catch unreachable;
+            return out.buffered();
+        }
+
+        // test toBytes {
+        //     var buf: [1024]u8 = undefined;
+        //     const relay: Relay = .init(
+        //         .fromBytes(&.{ 172, 18, 1, 30 }),
+        //         // zig fmt: off
+        //     &[_]u8{
+        //         0x72, 0x65, 0x6d, 0x6f, 0x76, 0x65, 0x20, 0x65, 0x76, 0x65,
+        //         0x6e, 0x74, 0x20, 0x6c, 0x6f, 0x67, 0x67, 0x65, 0x64
+        //     },
+        //     // zig fmt: on
+        //     );
+        //     // zig fmt: off
+        // var expected = [_]u8{
+        //     0x00, 0x3c, 0x00, 0x17, 0xac, 0x12, 0x01, 0x1e, 0x72,
+        //     0x65, 0x6d, 0x6f, 0x76, 0x65, 0x20, 0x65, 0x76, 0x65,
+        //     0x6e, 0x74, 0x20, 0x6c, 0x6f, 0x67, 0x67, 0x65, 0x64
+        // };
+        // // zig fmt: on
+        //     try expectEqualMessageBuffers(&expected, relay.toBytes(&buf));
+        // }
+    };
+
+    pub const Connection = struct {
+        src: u16,
+        dest: u16,
+        seq: u32,
+        id: u32,
+        reserved: u8 = undefined,
+        options: Options = .{},
+        payload: []const u8,
+
+        /// Option values.
+        /// Currently used!
+        pub const Options = packed struct(u8) {
+            opt1: bool = false,
+            opt2: bool = false,
+            opt3: bool = false,
+            opt4: bool = false,
+            opt5: bool = false,
+            opt6: bool = false,
+            opt7: bool = false,
+            management: bool = false,
+        };
+
+        /// Asserts that buf is large enough to fit the connection message.
+        pub fn toBytes(self: Connection, buf: []u8) []u8 {
+            var out: Writer = .fixed(buf);
+            out.writeInt(u16, @intFromEnum(Message.connection), .big) catch unreachable;
+            out.writeInt(u16, @intCast(self.payload.len + 14), .big) catch unreachable; // Saprus length field, unread.
+            out.writeInt(u16, self.src, .big) catch unreachable;
+            out.writeInt(u16, self.dest, .big) catch unreachable;
+            out.writeInt(u32, self.seq, .big) catch unreachable;
+            out.writeInt(u32, self.id, .big) catch unreachable;
+            out.writeByte(self.reserved) catch unreachable;
+            out.writeStruct(self.options, .big) catch unreachable;
+            out.writeAll(self.payload) catch unreachable;
+            return out.buffered();
+        }
+
+        /// If the current message is a management message, return what kind.
+        /// Else return null.
+        pub fn management(self: Connection) ParseError!?Management {
+            const b64_dec = std.base64.standard.Decoder;
+            if (self.options.management) {
+                var buf: [1]u8 = undefined;
+                _ = b64_dec.decode(&buf, self.payload) catch return error.InvalidMessage;
+
+                return switch (buf[0]) {
+                    'P' => .ping,
+                    'p' => .pong,
+                    else => error.UnknownSaprusType,
+                };
+            }
+            return null;
+        }
+
+        pub const Management = enum {
+            ping,
+            pong,
+        };
+    };
+
+    pub fn toBytes(self: Message, buf: []u8) []u8 {
         return switch (self) {
             inline .relay, .connection => |m| m.toBytes(buf),
             else => unreachable,
         };
     }
 
-    pub const parse = message.parse;
+    pub fn parse(bytes: []const u8) ParseError!Message {
-};
-
-pub const relay_dest_len = 4;
-
-pub fn parse(bytes: []const u8) MessageParseError!Message {
         var in: Reader = .fixed(bytes);
         const @"type" = in.takeEnum(std.meta.Tag(Message), .big) catch |err| switch (err) {
             error.InvalidEnumTag => return error.UnknownSaprusType,
@@ -71,9 +178,9 @@ pub fn parse(bytes: []const u8) MessageParseError!Message {
             },
             else => return error.NotImplementedSaprusType,
         }
-}
+    }
 
-test parse {
+    test parse {
         _ = try parse(&[_]u8{ 0x00, 0x3c, 0x00, 0x17, 0xac, 0x12, 0x01, 0x1e, 0x72, 0x65, 0x6d, 0x6f, 0x76, 0x65, 0x20, 0x65, 0x76, 0x65, 0x6e, 0x74, 0x20, 0x6c, 0x6f, 0x67, 0x67, 0x65, 0x64 });
 
         {
@@ -92,100 +199,9 @@ test parse {
 
             try std.testing.expectEqualDeep(expected, actual);
         }
-}
-
-const Relay = struct {
-    dest: Dest,
-    checksum: [2]u8 = undefined,
-    payload: []const u8,
-
-    pub const Dest = struct {
-        bytes: [relay_dest_len]u8,
-
-        /// Asserts bytes is less than or equal to 4 bytes
-        pub fn fromBytes(bytes: []const u8) Dest {
-            var buf: [4]u8 = @splat(0);
-            std.debug.assert(bytes.len <= buf.len);
-            @memcpy(buf[0..bytes.len], bytes);
-            return .{ .bytes = buf };
-        }
-    };
-
-    pub fn init(dest: Dest, payload: []const u8) Relay {
-        return .{ .dest = dest, .payload = payload };
     }
 
-    /// Asserts that buf is large enough to fit the relay message.
+    test "Round trip" {
-    pub fn toBytes(self: Relay, buf: []u8) []u8 {
-        var out: Writer = .fixed(buf);
-        out.writeInt(u16, @intFromEnum(Message.relay), .big) catch unreachable;
-        out.writeInt(u16, @intCast(self.payload.len + 4), .big) catch unreachable; // Length field, but unread. Will switch to checksum
-        out.writeAll(&self.dest.bytes) catch unreachable;
-        out.writeAll(self.payload) catch unreachable;
-        return out.buffered();
-    }
-
-    test toBytes {
-        var buf: [1024]u8 = undefined;
-        const relay: Relay = .init(
-            .fromBytes(&.{ 172, 18, 1, 30 }),
-            // zig fmt: off
-            &[_]u8{
-                0x72, 0x65, 0x6d, 0x6f, 0x76, 0x65, 0x20, 0x65, 0x76, 0x65,
-                0x6e, 0x74, 0x20, 0x6c, 0x6f, 0x67, 0x67, 0x65, 0x64
-            },
-            // zig fmt: on
-        );
-        // zig fmt: off
-        var expected = [_]u8{
-            0x00, 0x3c, 0x00, 0x17, 0xac, 0x12, 0x01, 0x1e, 0x72,
-            0x65, 0x6d, 0x6f, 0x76, 0x65, 0x20, 0x65, 0x76, 0x65,
-            0x6e, 0x74, 0x20, 0x6c, 0x6f, 0x67, 0x67, 0x65, 0x64
-        };
-        // zig fmt: on
-        try expectEqualMessageBuffers(&expected, relay.toBytes(&buf));
-    }
-};
-
-const Connection = struct {
-    src: u16,
-    dest: u16,
-    seq: u32,
-    id: u32,
-    reserved: u8 = undefined,
-    options: Options = undefined,
-    payload: []const u8,
-
-    /// Reserved option values.
-    /// Currently unused.
-    pub const Options = packed struct(u8) {
-        opt1: bool = false,
-        opt2: bool = false,
-        opt3: bool = false,
-        opt4: bool = false,
-        opt5: bool = false,
-        opt6: bool = false,
-        opt7: bool = false,
-        opt8: bool = false,
-    };
-
-    /// Asserts that buf is large enough to fit the connection message.
-    pub fn toBytes(self: Connection, buf: []u8) []u8 {
-        var out: Writer = .fixed(buf);
-        out.writeInt(u16, @intFromEnum(Message.connection), .big) catch unreachable;
-        out.writeInt(u16, @intCast(self.payload.len + 14), .big) catch unreachable; // Saprus length field, unread.
-        out.writeInt(u16, self.src, .big) catch unreachable;
-        out.writeInt(u16, self.dest, .big) catch unreachable;
-        out.writeInt(u32, self.seq, .big) catch unreachable;
-        out.writeInt(u32, self.id, .big) catch unreachable;
-        out.writeByte(self.reserved) catch unreachable;
-        out.writeStruct(self.options, .big) catch unreachable;
-        out.writeAll(self.payload) catch unreachable;
-        return out.buffered();
-    }
-};
-
-test "Round trip" {
         {
             const expected = [_]u8{ 0x0, 0xe9, 0x0, 0x15, 0x30, 0x80, 0xf0, 0xf0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x64, 0x36, 0x3a, 0x3a, 0x64, 0x61, 0x74, 0x61 };
             const msg = (try parse(&expected)).connection;
@@ -193,13 +209,24 @@ test "Round trip" {
             const res = msg.toBytes(&res_buf);
             try expectEqualMessageBuffers(&expected, res);
         }
-}
+    }
 
-// Skip checking the length / checksum, because that is undefined.
+    // Skip checking the length / checksum, because that is undefined.
-fn expectEqualMessageBuffers(expected: []const u8, actual: []const u8) !void {
+    fn expectEqualMessageBuffers(expected: []const u8, actual: []const u8) !void {
         try std.testing.expectEqualSlices(u8, expected[0..2], actual[0..2]);
         try std.testing.expectEqualSlices(u8, expected[4..], actual[4..]);
-}
+    }
+
+    pub const TypeError = error{
+        NotImplementedSaprusType,
+        UnknownSaprusType,
+    };
+    pub const ParseError = TypeError || error{
+        InvalidMessage,
+    };
+};
+
+const relay_dest_len = 4;
 
 const std = @import("std");
 const Allocator = std.mem.Allocator;
@@ -207,5 +234,5 @@ const Writer = std.Io.Writer;
 const Reader = std.Io.Reader;
 
 test {
-    std.testing.refAllDeclsRecursive(@This());
+    std.testing.refAllDecls(@This());
 }

src/root.zig

@@ -1,12 +1,29 @@
+// Copyright 2026 Robby Zambito
+//
+// This file is part of zaprus.
+//
+// Zaprus is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// Zaprus is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// Zaprus. If not, see <https://www.gnu.org/licenses/>.
+
+//! The Zaprus library is useful for implementing clients that interact with the [Saprus Protocol](https://gitlab.com/c2-games/red-team/saprus).
+//!
+//! The main entrypoint into this library is the `Client` type.
+//! It can be used to send fire and forget messages, and establish persistent connections.
+//! It is up to the consumer of this library to handle non-management message payloads.
+//! The library handles management messages automatically (right now, just ping).
+
 pub const Client = @import("Client.zig");
 pub const Connection = @import("Connection.zig");
-
+pub const Message = @import("message.zig").Message;
-const msg = @import("message.zig");
-
-pub const PacketType = msg.PacketType;
-pub const MessageTypeError = msg.MessageTypeError;
-pub const MessageParseError = msg.MessageParseError;
-pub const Message = msg.Message;
 
 test {
     @import("std").testing.refAllDecls(@This());