Initial commit

.gitlab-ci.yml

@@ -0,0 +1,13 @@
+debian:
+    image: debian:stable-slim
+    before_script:
+        - apt-get -qq install make clang
+    script:
+        - make
+
+alpine:
+    image: alpine:latest
+    before_script:
+        - apk add make clang
+    script:
+        - make

Makefile

@@ -0,0 +1,39 @@
+CPPFLAGS = -D_FORTIFY_SOURCE=2 -D_DEFAULT_SOURCE
+CFLAGS   = $(CPPFLAGS) -std=c99 -pedantic -Wall -Wextra -Werror -Os -march=native -mtune=native -fPIE
+LDFLAGS  = -Wl,-z,now,-z,relro,-s,-pie
+
+CC = clang
+
+OBJS = obj/main.o
+BIN  = bin/stc
+
+PREFIX = /usr
+
+default: obj bin $(BIN)
+
+obj:
+	@mkdir obj
+
+bin:
+	@mkdir bin
+
+$(BIN): $(OBJS)
+	$(CC)    -o $@ $^ $(LDFLAGS)
+
+obj/%.o: src/%.c
+	$(CC) -c -o $@ $^ $(CFLAGS)
+
+clean:
+	@[ -d obj ] && rm -rf obj
+	@[ -d bin ] && rm -rf bin
+
+format:
+	@clang-format -i -style="{BasedOnStyle: mozilla, IndentWidth: 4}" src/*.c
+
+install: default
+	install -Dm755 $(BIN) $(PREFIX)/bin/stc
+
+uninstall:
+	rm -f $(PREFIX)/bin/stc
+
+.PHONY: default clean format install uninstall

README.md

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+# stc
+
+Simple Telnet Client
+
+## Build
+
+```
+git clone https://framagit.org/franck.stauffer/stc
+cd stc
+make
+```
+
+## Install
+
+```
+sudo make install
+```
+
+## Uninstall
+
+```
+sudo make uninstall
+```
+
+## Usage
+
+```
+stc address|hostname [port]
+```

src/main.c

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+#include <arpa/inet.h>
+#include <fcntl.h>
+#include <netdb.h>
+#include <signal.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/epoll.h>
+#include <sys/socket.h>
+#include <termios.h>
+#include <unistd.h>
+
+#define SE 0xF0
+#define SB 0xFA
+#define WILL 0xFB
+#define WONT 0xFC
+#define DO 0xFD
+#define DONT 0xFE
+#define IAC 0xFF
+#define CMD_WINDOW_SIZE 0x1F
+
+int epoll_fd;
+int sock;
+struct termios tin;
+
+void
+cleanup(void)
+{
+    if (tcsetattr(STDIN_FILENO, TCSANOW, &tin))
+        perror("ERROR: tcsetattr");
+
+    if (close(epoll_fd) || close(sock))
+        perror("ERROR: close");
+}
+
+uint_fast8_t
+negotiate(unsigned char* buf)
+{
+    if (buf[1] == DO && buf[2] == CMD_WINDOW_SIZE) {
+        uint8_t msg0[3] = { IAC, WILL, CMD_WINDOW_SIZE };
+        if (send(sock, msg0, 3, 0) != 3) {
+            perror("ERROR: send");
+            return 0;
+        }
+
+        uint8_t msg1[9] = { IAC, SB, CMD_WINDOW_SIZE, 0, 80, 0, 24, IAC, SE };
+        if (send(sock, msg1, 9, 0) != 9) {
+            perror("ERROR: send");
+            return 0;
+        }
+
+        return 1;
+    }
+
+    for (uint_fast8_t i = 0; i < 3; ++i) {
+        if (buf[i] == DO)
+            buf[i] = WONT;
+        else if (buf[i] == WILL)
+            buf[i] = DO;
+    }
+
+    if (send(sock, buf, 3, 0) != 3) {
+        perror("ERROR: send");
+        return 0;
+    }
+
+    return 1;
+}
+
+uint_fast8_t
+net_init(const char* host, const char* port)
+{
+    sock = socket(AF_INET, SOCK_STREAM, 0);
+    if (sock == -1) {
+        perror("ERROR: socket");
+        return 0;
+    }
+
+    struct addrinfo hints;
+    memset(&hints, 0, sizeof(struct addrinfo));
+    hints.ai_family = AF_INET;
+    hints.ai_socktype = SOCK_STREAM;
+
+    struct addrinfo* res;
+    int_fast8_t err = getaddrinfo(host, port, &hints, &res);
+    if (err) {
+        if (err == EAI_SYSTEM)
+            perror("ERROR: getaddrinfo");
+        else
+            fprintf(stderr, "ERROR: getaddrinfo: %s\n", gai_strerror(err));
+        return 0;
+    }
+
+    if (connect(sock, res->ai_addr, res->ai_addrlen)) {
+        perror("ERROR: connect");
+        if (close(sock))
+            perror("ERROR: close");
+        return 0;
+    }
+
+    freeaddrinfo(res);
+
+    return 1;
+}
+
+void
+sighandler(int sig)
+{
+    fprintf(stderr, "Received %s", (sig == SIGTERM) ? "SIGTERM" : "SIGINT");
+    exit(sig);
+}
+
+uint_fast8_t
+terminal_set(void)
+{
+    if (tcgetattr(STDIN_FILENO, &tin)) {
+        perror("ERROR: tcgetattr");
+        return 0;
+    }
+
+    static struct termios tlocal;
+    memcpy(&tlocal, &tin, sizeof(struct termios));
+    cfmakeraw(&tlocal);
+
+    if (tcsetattr(STDIN_FILENO, TCSANOW, &tlocal)) {
+        perror("ERROR: tcsetattr");
+        return 0;
+    }
+
+    return 1;
+}
+
+int
+main(int argc, char** argv)
+{
+    if (argc < 2 || argc > 3) {
+        printf("USAGE: %s, address [port]\n", argv[0]);
+        return 1;
+    }
+
+    if (!net_init(argv[1], (argc == 3) ? argv[2] : "23"))
+        return 2;
+
+    if (!terminal_set())
+        return 3;
+
+    epoll_fd = epoll_create1(0);
+    if (epoll_fd == -1) {
+        perror("epoll_create1");
+        return 4;
+    }
+
+    atexit(cleanup);
+    if (signal(SIGINT, sighandler) == SIG_ERR) {
+        perror("signal");
+        return 5;
+    }
+
+    if (signal(SIGTERM, sighandler) == SIG_ERR) {
+        perror("signal");
+        return 5;
+    }
+
+    struct epoll_event ev[2];
+    memset(&ev, 0, 2 * sizeof(struct epoll_event));
+
+    ev[0].events = EPOLLIN;
+    ev[0].data.fd = 0;
+    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, 0, &ev[0])) {
+        perror("epoll_ctl");
+        return 6;
+    }
+
+    ev[1].events = EPOLLIN;
+    ev[1].data.fd = sock;
+    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, sock, &ev[1])) {
+        perror("epoll_ctl");
+        return 7;
+    }
+
+    uint_fast8_t run = 1;
+
+    do {
+        struct epoll_event events[2];
+        int_fast8_t count = epoll_wait(epoll_fd, events, 2, -1);
+        if (count == -1) {
+            perror("epoll_wait");
+            return 8;
+        }
+
+        for (int_fast8_t i = 0; i < count; ++i) {
+            if (events[i].data.fd == sock) {
+                uint8_t buf[3];
+                memset(buf, 0, 3);
+                int_fast8_t ret = recv(sock, buf, 1, 0);
+                if (ret == -1) {
+                    perror("recv");
+                    return 9;
+                }
+
+                if (!ret)
+                    return 0;
+
+                if (buf[0] == IAC) {
+                    ret = recv(sock, buf + 1, 2, 0);
+                    if (ret < 0) {
+                        perror("recv");
+                        return 10;
+                    }
+
+                    if (!ret)
+                        return 0;
+
+                    negotiate(buf);
+                } else {
+                    putchar(buf[0]);
+                    fflush(stdin);
+                }
+            } else if (events[i].data.fd == 0) {
+                const uint8_t chr = getchar();
+                if (chr == 3) {
+                    fputs("\n\rLeaving...\n\r", stdout);
+                    return 0;
+                }
+
+                if (send(sock, &chr, 1, 0) != 1) {
+                    perror("send");
+                    return 11;
+                }
+
+                if (chr == '\n')
+                    putchar('\r');
+            }
+        }
+    } while (run);
+}