http-server.c

/*
* gcc -g -o http-server http-server.c -levent
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <signal.h>
#include <fcntl.h>
#include <unistd.h>
#include <dirent.h>
#include <errno.h>

#include <event2/event.h>
#include <event2/http.h>
#include <event2/buffer.h>
#include <event2/util.h>
#include <event2/keyvalq_struct.h>

#include <netinet/in.h>
#include <arpa/inet.h>

char uri_root[512];

static const struct table_entry {
	const char *extension;
	const char *content_type;
} content_type_table[] = {
	{ "txt", "text/plain" }, 
	{ "c", "text/plain" }, 
	{ "h", "text/plain" }, 
	{ "html", "text/html" }, 
	{ "htm", "text/html" },
	{ "css", "text/css" },
	{ "gif", "image/gif" }, 
	{ "jpg", "image/jpg" }, 
	{ "jpeg", "image/jpeg" }, 
	{ "png", "image/png" }, 
	{ "pdf", "application/pdf" }, 
	{ "ps", "application/postscript" }, 
	{ NULL, NULL },
};

/* Try to guess a good content-type for 'path' */
const char* guess_content_type(const char *path)
{
	const char *last_period, *extension;
	const struct table_entry *ent;
	last_period = strrchr(path, '.');
	if (!last_period || strchr(last_period, '/'))
	{
		goto not_found;
	}

	extension = last_period + 1;
	for (ent = &content_type_table[0]; ent->extension; ++ent)
	{
		if (!evutil_ascii_strcasecmp(ent->extension, extension))
		{
			return ent->content_type;
		}
	}

not_found:
	return "application/misc";
}

/* Callbase used for the /dump URI, and for every non-get request:
** dumps all information to stdout and gives base a trivial 200 ok */
void dump_request_cb(struct evhttp_request *req, void *arg)
{
	const char *cmdtype;
	struct evkeyvalq *headers;
	struct evkeyval *header;
	struct evbuffer *buf;

	switch (evhttp_request_get_command(req))
	{
	case EVHTTP_REQ_GET:
		cmdtype = "GET";
		break;
	case EVHTTP_REQ_POST:
		cmdtype = "POST";
		break;
	case EVHTTP_REQ_HEAD:
		cmdtype = "HEAD";
		break;
	case EVHTTP_REQ_PUT:
		cmdtype = "PUT";
		break;
	case EVHTTP_REQ_DELETE:
		cmdtype = "DELETE";
		break;
	case EVHTTP_REQ_OPTIONS:
		cmdtype = "OPTIONS";
		break;
	case EVHTTP_REQ_TRACE:
		cmdtype = "TRACE";
		break;
	case EVHTTP_REQ_CONNECT:
		break;
	case EVHTTP_REQ_PATCH:
		cmdtype = "PATCH";
		break;
	default:
		cmdtype = "unknown";
		break;
	}

	printf("Received a %s request for %s\nHeader:\n", cmdtype, evhttp_request_get_uri(req));

	headers = evhttp_request_get_input_headers(req);
	for (header = headers->tqh_first; header; header = header->next.tqe_next)
	{
		printf(" %s: %s\n", header->key, header->value);
	}

	buf = evhttp_request_get_input_buffer(req);
	puts("Input data: <<<<");
	while (evbuffer_get_length(buf))
	{
		int n;
		char cbuf[128];
		n = evbuffer_remove(buf, cbuf, sizeof(cbuf));
		if (n > 0)
		{
			(void)fwrite(cbuf, 1, n, stdout);
		}
	}
	puts(">>>");

	evhttp_send_reply(req, 200, "ok", NULL);
}

/* This callback gets invoked when we get and http request than doesn't match 
* any other callback. Like any evhttp server callback, it has a simple job:
* it must eventually call evhttp_send_error() or evhttp_send_reply(). 
*/
void send_document_cb(struct evhttp_request *req, void *arg)
{
	struct evbuffer *evb = NULL;
	const char *docroot = arg;
	const char *uri = evhttp_request_get_uri(req);
	struct evhttp_uri *decoded = NULL;
	const char *path;
	char *decoded_path;
	char *whole_path = NULL;
	size_t len;
	int fd = -1;
	struct stat st;

	if (evhttp_request_get_command(req) != EVHTTP_REQ_GET)
	{
		dump_request_cb(req, arg);
		return;
	}

	printf("Got a GET request for <%s>\n", uri);

	/* Decode the URI */
	decoded = evhttp_uri_parse(uri);
	if (!decoded)
	{
		printf("It's not a good URI, Sneding BADREQUEST\n");
		evhttp_send_error(req, HTTP_BADREQUEST, 0);
		return;
	}

	/* Let's see what path the user asked for. */
	path = evhttp_uri_get_path(decoded);
	if (!path)
	{
		path = "/";
	}

	/* We need to decode it, to see what path the user really wanted */
	decoded_path = evhttp_uridecode(path, 0, NULL);
	if (decoded_path == NULL)
	{
		goto err;
	}

	/* Don't allow any ".."'s in the path, to avoid exposing stuff outside 
	* of the docroot. This test is both overzealous and underzealous:
	* it forbids aceptable paths like "/this/one..here", but it doesn't
	* do anything to prevent symlink following. */
	if (strstr(decoded_path, ".."))
	{
		goto err;
	}

	len = strlen(decoded_path) + strlen(docroot) + 2;
	if (!(whole_path = malloc(len)))
	{
		perror("malloc");
		goto err;
	}
	evutil_snprintf(whole_path, len, "%s/%s", docroot, decoded_path);

	if (stat(whole_path, &st) < 0)
	{
		goto err;
	}

	/* This holds the content we're sending */
	evb = evbuffer_new();

	if (S_ISDIR(st.st_mode))
	{
		/* If it's a directory, read the comments and make a little index page */
		DIR *d;
		struct dirent *ent;
		const char *trailing_slash = "";

		if (!strlen(path) || path[strlen(path) - 1] != '/')
		{
			trailing_slash = "/";
		}

		if (!(d = opendir(whole_path)))
		{
			goto err;
		}

		evbuffer_add_printf(evb, 
			"<!DOCTYPE html>\n"
			"<html>\n  "
			"  <head>\n"
			"    <meta charset='utf-8'>\n"
			"    <title>%s</title>\n"
			"    <base href='%s%s'>\n"
			"  </head>\n"
			"  <body>\n"
			"    <h1>%s</h1>\n"
			"    <ul>\n", 
			decoded_path, /* xxx html-escape this. */
			path, /* xxx html-escape this? */
			trailing_slash, 
			decoded_path /* xx html-escape this */
			);

		while ((ent = readdir(d)))
		{
			const char *name = ent->d_name;
			evbuffer_add_printf(evb,
				"    <li><a href=\"%s\">%s</a>\n", name, name);
		}

		evbuffer_add_printf(evb, "</ul></body></html>\n");
		closedir(d);
		evhttp_add_header(evhttp_request_get_output_headers(req),
			"Content-Type", "text/html");
	}
	else
	{
		/* Otherwise it's a file; and it to the buffer to get send via sendfile */
		const char *type = guess_content_type(decoded_path);
		if ((fd = open(whole_path, O_RDONLY)) < 0)
		{
			perror("open");
			goto err;
		}

		if (fstat(fd, &st) < 0)
		{
			/* Make sure the length still matches, now that we opened the file :/ */
			perror("fstat");
			goto err;
		}
		evhttp_add_header(evhttp_request_get_output_headers(req),
			"Content-Type", type);
		evbuffer_add_file(evb, fd, 0, st.st_size);
	}

	evhttp_send_reply(req, 200, "OK", evb);
	goto done;

err:
	evhttp_send_error(req, 404, "Document was not found");
	if (fd >= 0)
	{
		close(fd);
	}

done:
	if (decoded)
	{
		evhttp_uri_free(decoded);
	}

	if (decoded_path)
	{
		free(decoded_path);
	}

	if (whole_path)
	{
		free(whole_path);
	}

	if (evb)
	{
		evbuffer_free(evb);
	}
}

void syntax(void)
{
	fprintf(stdout, "Syntax: http-server port <docroot>\n");
}

int main(int argc, char **argv)
{
	struct event_base *base;
	struct evhttp *http;
	struct evhttp_bound_socket *handle;
	int port = 0;

	if (signal(SIGPIPE, SIG_IGN) == SIG_ERR)
	{
		printf("signal error, errno[%d], error[%s]", errno, strerror(errno));
		return -1;
	}

	if (argc < 3)
	{
		syntax();
		return -1;
	}

	port = atoi(argv[1]);

	base = event_base_new();
	if (!base)
	{
		printf("Couldn't create an event_base:exiting\n");
		return -1;
	}

	/* Create a new http oject to handle request */
	http = evhttp_new(base);
	if (!http)
	{
		printf("Couldn't create evhttp.Exiting\n");
		return -1;
	}

	/* The /dump URI will dump all requests to stdout and say 200 ok */
	evhttp_set_cb(http, "/dump", dump_request_cb, NULL);

	/* We want to accept arbitrary requests, so we need to set a "generic" cb
	* We can also add callbacks for specific paths */
	evhttp_set_gencb(http, send_document_cb, argv[2]);

	/* Now we teel the evhttp what port to listen on */
	handle = evhttp_bind_socket_with_handle(http, "0.0.0.0", port);
	if (!handle)
	{
		printf("Couldn't bind to port[%d], exiting\n", port);
		return -1;
	}

	{
		/* Extract and display the address we're listening on. */
		struct sockaddr_storage ss;
		evutil_socket_t fd;
		ev_socklen_t socklen = sizeof(ss);
		char addrbuf[128];
		void *inaddr;
		const char *addr;
		int got_port = -1;
		fd = evhttp_bound_socket_get_fd(handle);
		memset(&ss, 0, sizeof(ss));
		if (getsockname(fd, (struct sockaddr *)&ss, &socklen))
		{
			perror("getsockname() failed");
			return -1;
		}

		if (ss.ss_family == AF_INET)
		{
			got_port = ntohs(((struct sockaddr_in*)&ss)->sin_port);
			inaddr = &((struct sockaddr_in*)&ss)->sin_addr;
		}
		else if (ss.ss_family == AF_INET6)
		{
			got_port = ntohs(((struct sockaddr_in6*)&ss)->sin6_port);
			inaddr = &((struct sockaddr_in6*)&ss)->sin6_addr;
		}
		else
		{
			printf("Weird address family\n");
			return 1;
		}

		addr = evutil_inet_ntop(ss.ss_family, inaddr, addrbuf, sizeof(addrbuf));
		if (addr)
		{
			printf("Listening on %s:%d\n", addr, got_port);
			evutil_snprintf(uri_root, sizeof(uri_root), "http://%s:%d", addr, got_port);
		}
		else
		{
			printf("evutil_inet_ntop failed\n");
			return -1;
		}
	}
	event_base_dispatch(base);

	return 0;
}