First commit

This commit is contained in:
Juhani Krekelä 2018-07-03 17:26:06 +00:00
commit 772f1ef657
4 changed files with 261 additions and 0 deletions

3
.gitignore vendored Normal file
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*.swp
*.o
lewdfingerd

23
Makefile Normal file
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DESTDIR ?=
PREFIX ?= /usr/local
EXEC_PREFIX ?= $(PREFIX)
BINDIR ?= $(DESTDIR)$(EXEC_PREFIX)/bin
CFLAGS += -std=c11 -Os -g -Wall -Wextra -pedantic
CPPFLAGS +=
LDFLAGS +=
all: lewdfingerd
install: all
install lewdfingerd $(BINDIR)
lewdfingerd: lewdfingerd.c
$(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) -o $@ $<
.PHONY: all install clean distclean
clean:
rm lewdfingerd
distclean: clean

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UNLICENSE Normal file
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This is free and unencumbered software released into the public domain.
Anyone is free to copy, modify, publish, use, compile, sell, or
distribute this software, either in source code form or as a compiled
binary, for any purpose, commercial or non-commercial, and by any
means.
In jurisdictions that recognize copyright laws, the author or authors
of this software dedicate any and all copyright interest in the
software to the public domain. We make this dedication for the benefit
of the public at large and to the detriment of our heirs and
successors. We intend this dedication to be an overt act of
relinquishment in perpetuity of all present and future rights to this
software under copyright law.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.
For more information, please refer to [http://unlicense.org]

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lewdfingerd.c Normal file
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#define _GNU_SOURCE
#include <netdb.h>
#include <poll.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
struct pollfd *listens = NULL;
size_t num_listens = 0;
void log_error(const char * restrict format, ...) {
va_list args;
va_start(args, format);
vfprintf(stderr, format, args);
va_end(args);
}
void setup_listen(void) {
struct addrinfo hints;
struct addrinfo *getaddrinfo_result;
// AF_UNSPEC: either IPv4 or IPv6
// SOCK_STREAM: TCP
// AI_PASSIVE: fill out my IP for me
// AI_ADDRCONFIG: only return addresses I have a configured interface for
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE | AI_ADDRCONFIG;
int status = getaddrinfo(NULL, "79", &hints, &getaddrinfo_result);
if(status != 0) {
log_error("getaddrinfo failed: %s\n", gai_strerror(status));
exit(1);
}
for(struct addrinfo *res = getaddrinfo_result; res != NULL; res = res->ai_next) {
int yes = 1;
// Add corresponding interface to table of sockets
// Create socket
int sock = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
if(sock == -1) {
perror("socket");
exit(1);
}
// Disable the IPv4 over IPv6, as that results in IPv4 and IPv6 sockets conflicting and one of them not being able to be set up
if(res->ai_family == AF_INET6) {
if(setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, &yes, sizeof(yes)) == -1) {
perror("setsockopt");
exit(1);
}
}
// Set reuseaddr
if(setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes)) == -1) {
perror("setsockopt");
exit(1);
}
// Bind onto given address
if(bind(sock, res->ai_addr, res->ai_addrlen) == -1) {
perror("bind");
exit(1);
}
// Listen for incoming connections
if(listen(sock, 1) == -1) {
perror("listen");
exit(1);
}
// Grow the table of sockets
size_t index = num_listens++;
if(SIZE_MAX / sizeof(struct pollfd) < num_listens){
log_error("Too many interfaces to listen on\n");
exit(1);
}
listens = realloc(listens, num_listens * sizeof(struct pollfd));
if(listens == NULL) {
perror("realloc");
exit(1);
}
// Add socket to the table
struct pollfd new_pollobj = {.fd = sock, .events = POLLIN};
listens[index] = new_pollobj;
}
freeaddrinfo(getaddrinfo_result);
}
void drop_privileges(void) {
uid_t uid = getuid();
gid_t gid = getgid();
if(setresgid(gid, gid, gid) != 0) {
perror("setresgid");
exit(1);
}
if(setresuid(uid, uid, uid) != 0) {
perror("setresuid");
exit(1);
}
}
ssize_t writeall(int fd, const char *buf, size_t amount) {
size_t written = 0;
while(written < amount) {
ssize_t r = write(fd, buf + written, amount - written);
if(r < 0) {
return r;
}
written += r;
}
return written;
}
void handle_connection(int sock) {
size_t request_size = 0;
char *request = NULL;
for(;;) {
ssize_t amount_read;
char iobuf[1024];
amount_read = read(sock, &iobuf, sizeof(iobuf));
if(amount_read == 0) {
log_error("Client hung up\n");
shutdown(sock, SHUT_RDWR);
close(sock);
return;
} else if(amount_read < 0) {
perror("read");
shutdown(sock, SHUT_RDWR);
close(sock);
return;
}
size_t index = request_size;
request_size += amount_read;
if((request = realloc(request, request_size)) == NULL) {
perror("realloc");
exit(1);
}
memmove(request + index, iobuf, amount_read);
if(request_size >= 2 && request[request_size-2] == '\r' && request[request_size-1] == '\n') {
// Request read
break;
}
}
request[request_size-2] = '\0';
if(!strcmp(request, "")) {
const char *response = "Who do you want to finger?\r\n";
if(writeall(sock, response, strlen(response)) < 0) {
perror("write");
}
} else {
const char *response = "Lewd.\r\n";
if(writeall(sock, response, strlen(response)) < 0) {
perror("write");
}
}
shutdown(sock, SHUT_RDWR);
close(sock);
}
int main(void) {
drop_privileges();
setup_listen();
for(;;) {
int amount_ready = poll(listens, num_listens, -1);
if(amount_ready < 0) {
perror("poll");
exit(1);
}
for(size_t i = 0; i < num_listens && amount_ready > 0; i++) {
if(listens[i].revents & POLLIN) {
struct sockaddr_storage client_addr;
socklen_t addr_size = sizeof(client_addr);
int sock = accept(listens[i].fd, (struct sockaddr *)&client_addr, &addr_size);
handle_connection(sock);
amount_ready--;
}
}
}
}