From 9d7b0311d5948fca09b19dbe27e5f506e2e303e0 Mon Sep 17 00:00:00 2001 From: Russell King Date: Fri, 16 Apr 2021 14:01:05 +0100 Subject: event-httpd: add event httpd support Add event httpd, which is a small and basic http server designed to provide server sent events to clients. The server accepts updates through a simple "UPDATE" method which are then broadcast to clients listening using the "GET" method. Signed-off-by: Russell King --- .gitignore | 5 + COPYING | 339 +++++++++++++++++++++++++++++++++++++++++++++++++ Makefile | 19 +++ README | 21 +++ event-httpd.c | 302 +++++++++++++++++++++++++++++++++++++++++++ event-httpd.h | 28 ++++ event-httpd.service.in | 13 ++ resource.c | 105 +++++++++++++++ resource.h | 17 +++ 9 files changed, 849 insertions(+) create mode 100644 .gitignore create mode 100644 COPYING create mode 100644 Makefile create mode 100644 README create mode 100644 event-httpd.c create mode 100644 event-httpd.h create mode 100644 event-httpd.service.in create mode 100644 resource.c create mode 100644 resource.h diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..0b729c9 --- /dev/null +++ b/.gitignore @@ -0,0 +1,5 @@ +*.o +*.service +*.swp +event-httpd +event-httpd.service diff --git a/COPYING b/COPYING new file mode 100644 index 0000000..d159169 --- /dev/null +++ b/COPYING @@ -0,0 +1,339 @@ + GNU GENERAL PUBLIC LICENSE + Version 2, June 1991 + + Copyright (C) 1989, 1991 Free Software Foundation, Inc., + 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + Preamble + + The licenses for most software are designed to take away your +freedom to share and change it. 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If this is what you want to do, use the GNU Lesser General +Public License instead of this License. diff --git a/Makefile b/Makefile new file mode 100644 index 0000000..b062b10 --- /dev/null +++ b/Makefile @@ -0,0 +1,19 @@ +CFLAGS :=-O2 -Wall -g +CPPFLAGS :=$(shell pkg-config --cflags gio-2.0) +LDLIBS :=$(shell pkg-config --libs gio-2.0) +INSTALL :=install + +prefix :=/usr/local +sbindir :=$(prefix)/sbin +systemdsystemunitdir :=/etc/systemd/system + +all: event-httpd event-httpd.service + +install: + $(INSTALL) -s -m 755 event-httpd $(sbindir) + $(INSTALL) -m 644 event-httpd.service $(systemdsystemunitdir) + +event-httpd: event-httpd.o resource.o + +event-httpd.service: event-httpd.service.in + sed "s|@sbindir@|$(sbindir)|" $< > $@ diff --git a/README b/README new file mode 100644 index 0000000..57d9ac6 --- /dev/null +++ b/README @@ -0,0 +1,21 @@ +This is a very basic HTTP server, designed for real-time server sent +event streams. BEWARE: the server offers little to no security +features. + +The server supports: +- the standard HTTP "GET" method for retrieval of events. +- a custom "UPDATE" method to send events. +- HTTP 1.0 and 1.1 connections. HTTP 1.1 uses chunked mode. + +The server is hard-coded to listen on TCP *:1180. + +Design +------ +The design concept is: + +public ------ apache reverse ----- event ------ data gathering +internet proxy httpd server application + +The reverse proxy is responsible for controlling public access to the +event streams served by the mini-httpd event server; the event server +itself should not be publically accessible. diff --git a/event-httpd.c b/event-httpd.c new file mode 100644 index 0000000..3ec2790 --- /dev/null +++ b/event-httpd.c @@ -0,0 +1,302 @@ +// mini-httpd: this is a single threaded, event driven very basic http +// server designed for event streams. +// +// Copyright (C) 2021 Russell King. +// Licensed under GPL version 2. See COPYING. +// +// This is designed *not* to be a publically accessible HTTP server, +// but is designed to be used behind e.g. an Apache reverse proxy that +// sends X-Forwarded-* headers. The presence of these headers prevents +// the served data being updated maliciously - updates must be done +// directly to this server. + +#include +#include +#include + +#include "event-httpd.h" +#include "resource.h" + +static GHashTable *resource_hash; + +void close_client(struct client *c) +{ + if (c->request) + g_free(c->request); + g_object_unref(c->data); + g_object_unref(c->conn); + g_free(c); +} + +void respond_header(struct client *c, int error_code, const char *reason, + const char *headers) +{ + g_output_stream_printf(c->out, NULL, NULL, NULL, + "HTTP/1.1 %d %s\r\n%s\r\n", + error_code, reason, headers); +} + +void respond_chunk(struct client *c, GString *s) +{ + if (c->can_chunk) + g_output_stream_printf(c->out, NULL, NULL, NULL, + "%x\r\n%s\r\n", s->len, s->str); + else + g_output_stream_write(c->out, s->str, s->len, NULL, NULL); +} + +static void respond_error(struct client *c, int error_code, const char *reason) +{ + GString *headers, *body = NULL; + + headers = g_string_new("Cache-Control: no-cache\r\n" + "Connection: close\r\n"); + + if (error_code != 204) { + g_string_append(headers, + "Content-type: text/html; charset=UTF-8\r\n"); + if (c->can_chunk) + g_string_append(headers, + "Transfer-Encoding: chunked\r\n"); + + body = g_string_sized_new(1024); + g_string_printf(body, + "%d %s" + "%s", + error_code, reason, reason); + } + + respond_header(c, error_code, reason, headers->str); + if (body) + respond_chunk(c, body); + g_string_free(body, TRUE); + g_string_free(headers, TRUE); + + close_client(c); +} + +static void finish(GObject *source, GAsyncResult *res, gpointer user_data) +{ + struct client *c = user_data; + GError *error = NULL; + gsize len; + + g_data_input_stream_read_line_finish(c->data, res, &len, &error); + + if (c->resource->close) { + c->resource->close(c, c->resource); + c->resource = NULL; + } + + close_client(c); +} + +static void update(GObject *source, GAsyncResult *res, gpointer user_data) +{ + struct client *c = user_data; + GError *error = NULL; + char *line; + gsize len; + + line = g_data_input_stream_read_line_finish(c->data, res, &len, &error); + if (error || !line) { + if (error) + g_free(error); + close_client(c); + return; + } + + c->resource->update(c, c->resource, line); + g_data_input_stream_read_line_async(c->data, 0, NULL, update, c); +} + +enum method { + GET, + UPDATE, +}; + +static void receive(GObject *source, GAsyncResult *res, gpointer user_data) +{ + struct client *c = user_data; + struct resource *resource; + enum method method; + GError *error = NULL; + gsize len; + char *line, *uri, *query, *unescaped, *version; + + line = g_data_input_stream_read_line_finish(c->data, res, &len, &error); + if (error || !line) { + if (error) + g_free(error); + close_client(c); + return; + } + + // In the interest of robustness, servers SHOULD ignore any empty + // line(s) received where a Request-Line is expected. + if (!c->request) { + if (line[0]) + c->request = g_strdup(line); + + g_data_input_stream_read_line_async(c->data, 0, NULL, + receive, c); + return; + } + + // Continue reading the request headers (we discard them) + if (line[0]) { + // Detect any X-Forwarded-* header + // FIXME: should this be case-insensitive? + if (g_str_has_prefix(line, "X-Forwarded-")) + c->forwarded = TRUE; + + g_data_input_stream_read_line_async(c->data, 0, NULL, + receive, c); + return; + } + + // End of request. Parse it. + // Find the URI + uri = strchr(c->request, ' '); + if (!uri) { + respond_error(c, 400, "Invalid request"); + return; + } + + *uri++ = '\0'; + + // Find the version + version = strchr(uri, ' '); + if (!version) { + respond_error(c, 400, "Invalid request"); + return; + } + + *version++ = '\0'; + + // Check that the version is HTTP/1.x. We probably ought to + // parse the major version better, as leading zeros should be + // accepted. + if (!g_str_has_prefix(version, "HTTP/1.")) { + respond_error(c, 505, "HTTP Version Not Supported"); + return; + } + + // Split the query string + query = strchr(uri, '?'); + if (query) + *query++ = '\0'; + + c->uri = uri; + c->query = query; + c->version = version; + + // HTTP/1.1 and later can use chunked mode. Note that http 1.1 + // allows leading zeros. + c->can_chunk = atoi(version + 7) != '0'; + + // Check the method + if (!strcmp(c->request, "GET")) { + method = GET; + } else if (!strcmp(c->request, "UPDATE") && !c->forwarded) { + // Update is only permitted if not forwarded through a + // proxy. NOTE: this is the only way we control access. + method = UPDATE; + } else { + respond_error(c, 501, "Not Implemented"); + return; + } + + // Unescape the URI + unescaped = g_uri_unescape_string(uri, NULL); + + // Lookup the resource handler + resource = g_hash_table_lookup(resource_hash, unescaped); + if (!resource) { + respond_error(c, 404, "Not Found"); + return; + } + + c->resource = resource; + + // We have a valid resource, start the response + switch (method) { + case GET: + if (!resource->get) { + respond_error(c, 204, "No Content"); + close_client(c); + return; + } + + if (resource->get(c, resource)) { + g_data_input_stream_read_line_async(c->data, 0, NULL, + finish, c); + } else { + close_client(c); + } + break; + + case UPDATE: + if (!resource->update) { + respond_error(c, 204, "No Content"); + close_client(c); + return; + } + + g_data_input_stream_read_line_async(c->data, 0, NULL, + update, c); + break; + } +} + +static gboolean incoming(GSocketService *service, GSocketConnection *connection, + GObject *source_object, gpointer user_data) +{ + struct client *c; + + c = g_new0(struct client, 1); + c->conn = g_object_ref(connection); + c->out = g_io_stream_get_output_stream(G_IO_STREAM(connection)); + c->in = g_io_stream_get_input_stream(G_IO_STREAM(connection)); + c->data = g_data_input_stream_new(c->in); + + g_tcp_connection_set_graceful_disconnect(G_TCP_CONNECTION(connection), + TRUE); + + /* Be tolerant of input */ + g_data_input_stream_set_newline_type(c->data, + G_DATA_STREAM_NEWLINE_TYPE_ANY); + + g_data_input_stream_read_line_async(c->data, 0, NULL, receive, c); + + return TRUE; +} + +int mini_httpd_init(int port, const char *progname) +{ + GSocketService *service; + GError *error = NULL; + + service = g_socket_service_new(); + if (!g_socket_listener_add_inet_port(G_SOCKET_LISTENER(service), port, + NULL, &error)) { + g_printerr("%s: %s\n", progname, error->message); + return 0; + } + + g_signal_connect(service, "incoming", G_CALLBACK(incoming), NULL); + + return 1; +} + +int main(int argc, char *argv[]) +{ + resource_hash = g_hash_table_new(g_str_hash, g_str_equal); + resource_init(resource_hash); + + if (!mini_httpd_init(1180, argv[0])) + return 1; + + g_main_loop_run(g_main_loop_new(NULL, FALSE)); + g_assert_not_reached(); +} diff --git a/event-httpd.h b/event-httpd.h new file mode 100644 index 0000000..7818bd5 --- /dev/null +++ b/event-httpd.h @@ -0,0 +1,28 @@ +// Copyright (C) 2021 Russell King. +// Licensed under GPL version 2. See COPYING. +#ifndef MINI_HTTPD_H +#define MINI_HTTPD_H + +struct client { + GSocketConnection *conn; + GDataInputStream *data; + GOutputStream *out; + GInputStream *in; + + gboolean forwarded; + gboolean can_chunk; + char *request; + char *uri; + char *query; + char *version; + + struct resource *resource; + void *resource_data; +}; + +void close_client(struct client *c); +void respond_header(struct client *c, int error_code, const char *reason, + const char *headers); +void respond_chunk(struct client *c, GString *s); + +#endif diff --git a/event-httpd.service.in b/event-httpd.service.in new file mode 100644 index 0000000..85983b9 --- /dev/null +++ b/event-httpd.service.in @@ -0,0 +1,13 @@ +[Unit] +Description=event stream service +After=network.target + +[Service] +Type=simple +ExecStart=@sbindir@/event-httpd +Restart=on-failure +NoNewPrivileges=yes +DynamicUser=yes + +[Install] +WantedBy=multi-user.target diff --git a/resource.c b/resource.c new file mode 100644 index 0000000..c1473e7 --- /dev/null +++ b/resource.c @@ -0,0 +1,105 @@ +// Copyright (C) 2021 Russell King. +// Licensed under GPL version 2. See COPYING. +#include +#include "event-httpd.h" +#include "resource.h" + +struct resource_object { + GList *client_list; + char *str; +}; + +static struct resource_object position_object; +static struct resource_object signal_object; + +static void object_v1_send(struct client *c, struct resource_object *obj) +{ + const char *str = obj->str; + GString *s; + + if (!str) + return; + + // Format the text/event-stream response + // The double newline terminates this event + // See https://www.html5rocks.com/en/tutorials/eventsource/basics/ + s = g_string_sized_new(1024); + g_string_printf(s, "data:%s\n", str); + g_string_append_c(s, '\n'); + + respond_chunk(c, s); + g_string_free(s, TRUE); +} + +static int object_v1_get(struct client *c, struct resource *r) +{ + struct resource_object *obj = r->data; + + respond_header(c, 200, "OK", + "Cache-Control: no-cache\r\n" + "Connection: keep-alive\r\n" + "Content-Type: text/event-stream; charset=UTF-8\r\n" + "Transfer-Encoding: chunked\r\n"); + + object_v1_send(c, obj); + + // Add this client to the object list so it receives updates + obj->client_list = g_list_append(obj->client_list, c); + + return 1; +} + +// Update this client with the new resource object data +static void object_v1_client_update(gpointer data, gpointer user_data) +{ + struct resource_object *obj = user_data; + struct client *c = data; + + object_v1_send(c, obj); +} + +// Update all attached clients with the new resource object data +static int object_v1_update(struct client *c, struct resource *r, const char *m) +{ + struct resource_object *obj = r->data; + char *n, *o; + + n = g_strdup(m); + g_strchomp(n); + o = obj->str; + obj->str = n; + if (o) + g_free(o); + + g_list_foreach(obj->client_list, object_v1_client_update, obj); + + return 0; +} + +static void object_v1_close(struct client *c, struct resource *r) +{ + struct resource_object *obj = r->data; + + // Remove this client from the object list + obj->client_list = g_list_remove(obj->client_list, c); +} + +static struct resource resource_position1 = { + .get = object_v1_get, + .update = object_v1_update, + .close = object_v1_close, + .data = &position_object, +}; + +static struct resource resource_signal1 = { + .get = object_v1_get, + .update = object_v1_update, + .close = object_v1_close, + .data = &signal_object, +}; + +void resource_init(GHashTable *hash) +{ + g_hash_table_insert(hash, "/api/1/position", &resource_position1); + g_hash_table_insert(hash, "/api/1/signal", &resource_signal1); +} diff --git a/resource.h b/resource.h new file mode 100644 index 0000000..44d0d74 --- /dev/null +++ b/resource.h @@ -0,0 +1,17 @@ +// Copyright (C) 2021 Russell King. +// Licensed under GPL version 2. See COPYING. +#ifndef RESOURCE_H +#define RESOURCE_h + +struct client; + +struct resource { + int (*get)(struct client *c, struct resource *r); + int (*update)(struct client *c, struct resource *r, const char *m); + void (*close)(struct client *c, struct resource *r); + void *data; +}; + +void resource_init(GHashTable *hash); + +#endif -- cgit