Initial commit

paul-rodriguez · paul-rodriguez · commit d9b87fc8d562 · 2023-08-18T11:07:53.000+02:00
This commit adds a simple version of tinycat with the bare
minimum functionality.

Tinycat is a lightweight (&lt;100K) netcat alternative which is statically
linked (against musl).
Tinycat exclusively deals with TCP, and can only handle IP and UNIX
domain sockets.

The netcat options -k, -l and -U are implemented and they have the same
meaning (refer to the help message for details).
diff --git a/.gitignore b/.gitignore
@@ -0,0 +1,5 @@
+# Build directory
+/build
+
+# Build dependencies
+/deps
diff --git a/.gitmodules b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "lib/argparse"]
+	path = lib/argparse
+	url = git@github.com:cofyc/argparse.git
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -0,0 +1,44 @@
+cmake_minimum_required(VERSION 3.22)
+
+set(CMAKE_C_COMPILER "${CMAKE_CURRENT_LIST_DIR}/deps/bin/musl-gcc")
+
+project(tinycat C)
+
+add_executable(tinycat)
+
+add_subdirectory(lib)
+add_subdirectory(src)
+
+target_link_libraries(
+    tinycat
+    PRIVATE
+    argparse
+)
+
+target_link_options(
+    tinycat
+    PRIVATE
+    -static
+    -static-libgcc
+)
+
+target_include_directories(
+    tinycat
+    PRIVATE
+    include
+)
+
+target_compile_options(
+    tinycat
+    PRIVATE
+    -Wall
+    -Wextra
+    -std=c17
+    $<$<CONFIG:Release,RelWithDebInfo>:-Os>
+)
+
+target_compile_definitions(
+    tinycat
+    PRIVATE
+    _POSIX_C_SOURCE=200809L
+)
diff --git a/LICENSE b/LICENSE
diff --git a/build.sh b/build.sh
@@ -0,0 +1,15 @@
+#! /usr/bin/env bash
+
+set -e
+
+CURRENT_DIR="$(dirname $0)"
+BUILD_DIR="${CURRENT_DIR}/build"
+
+mkdir -p ${BUILD_DIR}
+pushd ${BUILD_DIR} > /dev/null
+    cmake -G "Ninja Multi-Config" ..
+    ninja -f build-Debug.ninja
+    ninja -f build-Release.ninja
+    ninja -f build-RelWithDebInfo.ninja
+popd > /dev/null
+
diff --git a/clean.sh b/clean.sh
@@ -0,0 +1,6 @@
+#! /usr/bin/env bash
+
+set -e
+
+BUILD_DIR="$(dirname $0)/build"
+rm -rf ${BUILD_DIR:?}
diff --git a/include/cleanup.h b/include/cleanup.h
@@ -0,0 +1,9 @@
+#pragma once
+
+void setupCleanup();
+
+void registerCreatedUnixSocket(char const * const path);
+void registerOpenedSocket(int const socket);
+void closeSocket(int const socket);
+
+void handleInterrupt();
diff --git a/include/cli.h b/include/cli.h
@@ -0,0 +1,24 @@
+#pragma once
+
+#include <stdbool.h>
+
+typedef enum
+{
+    TcpSocket,
+    UnixSocket,
+} SocketType;
+
+typedef struct
+{
+    bool loop;
+    bool listen;
+    char const * unixSocket;
+    char const * address;
+    char const * port;
+} Args;
+
+Args parse(int argc, char const * * argv);
+
+int toString(char * buf, int size, Args const * args);
+
+SocketType getSocketType(Args const * args);
diff --git a/include/client.h b/include/client.h
@@ -0,0 +1,6 @@
+#pragma once
+
+#include "cli.h"
+
+void client(Args const * args);
+
diff --git a/include/config.h b/include/config.h
@@ -0,0 +1,3 @@
+#pragma once
+
+#define MAX_CONNECTIONS (1)
diff --git a/include/fdio.h b/include/fdio.h
@@ -0,0 +1,12 @@
+#pragma once
+
+typedef struct {
+    int originFd;
+    int size;
+    char const * data;
+} Buffer;
+
+void fdio_send(int const destFd, Buffer const buf);
+
+Buffer fdio_receive(int const socketFd, int const pipeFd);
+
diff --git a/include/ip.h b/include/ip.h
@@ -0,0 +1,5 @@
+#pragma once
+
+int ip_client(char const * const address, char const * const port);
+int ip_listenSocket(char const * const port);
+
diff --git a/include/loop.h b/include/loop.h
@@ -0,0 +1,4 @@
+#pragma once
+
+void loop(int const socketFd);
+
diff --git a/include/network.h b/include/network.h
@@ -0,0 +1,3 @@
+#pragma once
+
+int network_acceptSocket(int const listenSocket);
diff --git a/include/server.h b/include/server.h
@@ -0,0 +1,6 @@
+#pragma once
+
+#include "cli.h"
+
+void server(Args const * args);
+
diff --git a/include/unix.h b/include/unix.h
@@ -0,0 +1,7 @@
+#pragma once
+
+/** Portable limit for the length of a unix socket path. */
+#define MAX_SOCKET_PATH_LEN (108)
+
+int unix_client(char const * const path);
+int unix_listenSocket(char const * const path);
diff --git a/installBuildDependencies.sh b/installBuildDependencies.sh
@@ -0,0 +1,31 @@
+#! /usr/bin/env bash
+
+set -e
+
+CURRENT_DIR="$(dirname $(pwd)/$0)"
+
+function install_musl()
+{
+    DEPS_DIR="${CURRENT_DIR}/deps"
+    mkdir -p "${DEPS_DIR}"
+    pushd "${DEPS_DIR}" > /dev/null
+        rm -rf ./musl
+        git clone --depth=1 git://git.musl-libc.org/musl
+        pushd musl > /dev/null
+            ./configure \
+                --prefix="${DEPS_DIR}/install" \
+                --exec-prefix="${DEPS_DIR}" \
+                --disable-shared
+            make
+            make install
+        popd > /dev/null
+    popd > /dev/null
+}
+
+sudo apt-get update
+sudo apt-get install -y \
+    cmake \
+    ninja-build
+
+install_musl
+
diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
@@ -0,0 +1,16 @@
+
+add_library(argparse)
+
+target_sources(
+    argparse
+    PRIVATE
+    argparse/argparse.c
+)
+
+target_include_directories(
+    argparse
+    PUBLIC
+    argparse
+)
+
+
diff --git a/lib/argparse b/lib/argparse
@@ -0,0 +1 @@
+Subproject commit c612dc03958cdbd538ca306d61853b643a435933
diff --git a/readme.md b/readme.md
@@ -0,0 +1,13 @@
+
+# tinycat
+
+This program is a small footprint replacement for netcat.
+
+Tinycat only handles IP and UNIX sockets and only supports the -k and -l
+options of netcat.
+In other words, it can only be a simple client or a simple server.
+
+Tinycat is completely self-contained.
+It is statically linked with all the libraries it depends on.
+Tinycat is meant to be used in restricted environments where the supporting
+libraries of netcat aren't present.
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
@@ -0,0 +1,15 @@
+target_sources(
+    tinycat
+    PRIVATE
+    cleanup.c
+    cli.c
+    client.c
+    fdio.c
+    ip.c
+    loop.c
+    main.c
+    network.c
+    server.c
+    unix.c
+)
+
diff --git a/src/cleanup.c b/src/cleanup.c
@@ -0,0 +1,91 @@
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include "cleanup.h"
+#include "config.h"
+#include "ip.h"
+#include "unix.h"
+
+#define MAX_SOCKETS (MAX_CONNECTIONS + 1)
+#define NO_SOCKET (-1)
+
+static int openSockets_s[MAX_SOCKETS] = {};
+static int nbSockets_s = 0;
+static char unixSocketPath_s[MAX_SOCKET_PATH_LEN] = {};
+
+void setupCleanup()
+{
+    signal(SIGINT, handleInterrupt);
+}
+
+void registerCreatedUnixSocket(char const * const path)
+{
+    strncpy(unixSocketPath_s, path, MAX_SOCKET_PATH_LEN);
+}
+
+void registerOpenedSocket(int const socket)
+{
+    if (nbSockets_s == MAX_SOCKETS)
+    {
+        fprintf(stderr,
+                "Failed to register socket %d for cleanup: too many (%d) "
+                "sockets already opened",
+                socket,
+                nbSockets_s);
+    }
+    openSockets_s[nbSockets_s] = socket;
+    nbSockets_s++;
+}
+
+void closeSocket(int const socket)
+{
+    close(socket);
+    for (int i = 0; i < nbSockets_s; i++)
+    {
+        int * const socketPtr = openSockets_s + i;
+        if (*socketPtr == socket)
+        {
+            memmove(socketPtr, socketPtr + 1, nbSockets_s - 1 - i);
+            openSockets_s[nbSockets_s-1] = NO_SOCKET;
+            nbSockets_s--;
+            return;
+        }
+    }
+    fprintf(stderr,
+            "Tried to unregister socket %d which wasn't in the cleanup list",
+            socket);
+    exit(EXIT_FAILURE);
+}
+
+void handleInterrupt()
+{
+    fprintf(stderr, "Received INT signal, closing sockets\n");
+    for (int i = 0; i < nbSockets_s; i++)
+    {
+        int const shutdownErr = shutdown(openSockets_s[i], SHUT_RDWR);
+        if (shutdownErr != 0)
+        {
+            perror("shutdown failed");
+        }
+        int const closeErr = close(openSockets_s[i]);
+        if (closeErr != 0)
+        {
+            perror("close failed");
+        }
+        fprintf(stderr, "Closed socket %d\n", openSockets_s[i]);
+    }
+
+    if (unixSocketPath_s[0] != '\0')
+    {
+        int const unlinkErr = unlink(unixSocketPath_s);
+        if (unlinkErr != 0)
+        {
+            perror("unlink failed");
+        }
+    }
+    exit(0);
+}
diff --git a/src/cli.c b/src/cli.c
diff --git a/src/client.c b/src/client.c
diff --git a/src/fdio.c b/src/fdio.c
diff --git a/src/ip.c b/src/ip.c
diff --git a/src/loop.c b/src/loop.c
diff --git a/src/main.c b/src/main.c
diff --git a/src/network.c b/src/network.c
diff --git a/src/server.c b/src/server.c
diff --git a/src/unix.c b/src/unix.c

-Original file line number
+Diff line change
@@ @@ -0,0 +1,5 @@ @@
 +# Build directory
 +/build
++
 +# Build dependencies
 +/deps
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+[submodule "lib/argparse"]`
	`2`	`+ path = lib/argparse`
	`3`	`+ url = git@github.com:cofyc/argparse.git`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+#pragma once`
	`2`	`+`
	`3`	`+#define MAX_CONNECTIONS (1)`