From 5d4ea2faee069e94468e14232d09b774903285f1 Mon Sep 17 00:00:00 2001
From: scratko <m@scratko.xyz>
Date: Wed, 17 Jul 2024 02:33:49 +0300
Subject: Initial commit

---
 http_server.c         | 580 ++++++++++++++++++++++++++++++++++++++++++++++++++
 test_files/400.html   |   7 +
 test_files/404.html   |   7 +
 test_files/index.html |  17 ++
 4 files changed, 611 insertions(+)
 create mode 100644 http_server.c
 create mode 100644 test_files/400.html
 create mode 100644 test_files/404.html
 create mode 100644 test_files/index.html

diff --git a/http_server.c b/http_server.c
new file mode 100644
index 0000000..e769c09
--- /dev/null
+++ b/http_server.c
@@ -0,0 +1,580 @@
+#include <stdio.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <fcntl.h>
+#include <syslog.h>
+
+
+#ifndef INBUFSIZE
+#define INBUFSIZE 4096
+#endif
+
+#ifndef OUTBUFSIZE
+#define OUTBUFSIZE 4096
+#endif
+
+#ifndef LISTEN_QLEN
+#define LISTEN_QLEN 32
+#endif
+
+#ifndef INIT_SESS_ARR_SIZE
+#define INIT_SESS_ARR_SIZE 32
+#endif
+
+#ifndef FILENAME_SIZE
+#define FILENAME_SIZE 1024
+#endif
+
+enum fsm_states {
+    header_start,
+    waiting_host,
+    empty_line,
+    writing_header,
+    writing_body
+};
+
+struct session {
+    int fd;
+    unsigned long from_ip;
+    unsigned short from_port;
+    char in_buffer[INBUFSIZE];
+    char out_buffer[OUTBUFSIZE];
+    int in_buf_used;
+    int out_buf_used;
+    enum fsm_states state;
+    int rs_fd;
+    int data_transfer_status;
+    char *path;
+    int bad_request;
+    int not_found;
+};
+
+struct server {
+    int listen_socket;
+    struct session **session_array;
+    int session_size;
+    char *host;
+    char *resource_dir;
+};
+
+static void init_session(struct session *new_session, struct sockaddr_in *from,
+                         int fd)
+{
+    new_session->fd = fd;
+    new_session->from_ip = ntohl(from->sin_addr.s_addr);
+    new_session->from_port = ntohs(from->sin_port);
+    new_session->in_buf_used = 0;
+    new_session->out_buf_used = 0;
+    new_session->state = header_start;
+    new_session->rs_fd = -1;
+    new_session->data_transfer_status = 0;
+    new_session->path = NULL;
+    new_session->bad_request = 0;
+    new_session->not_found = 0;
+}
+
+static int accept_client(struct server *serv)
+{
+    int fd, i, flags;
+    struct sockaddr_in addr;
+    struct session *new_session;
+    socklen_t len = sizeof(addr);
+    fd = accept(serv->listen_socket, (struct sockaddr*) &addr, &len);
+    if(fd == -1)
+        return 0;
+    /* setting non-blocking mode for socket*/
+    flags = fcntl(fd, F_GETFL);
+    fcntl(fd, F_SETFL, flags | O_NONBLOCK);
+
+    if(fd >= serv->session_size) {
+        int newlen = serv->session_size;
+        while(fd >= newlen)
+            newlen += INIT_SESS_ARR_SIZE;
+        serv->session_array =
+            realloc(serv->session_array, newlen * sizeof(struct session*));
+        for(i = serv->session_size; i < newlen; i++)
+            serv->session_array[i] = NULL;
+        serv->session_size = newlen;
+    }
+    new_session = malloc(sizeof(struct session));
+    serv->session_array[fd] = new_session;
+    init_session(new_session, &addr, fd);
+    return 1;
+}
+
+static int host_search_condition(const char *line)
+{
+    return !(strncmp(line, "Host:", strlen("Host:")) &&
+            strncmp(line, "host:", strlen("host:")));
+}
+
+static int match_hosts(struct server *serv, const char *line, int length)
+{
+    int i, last_idx;
+
+    if(strlen("host:") > length)
+        return 0;
+    if(!host_search_condition(line))
+        return 0;
+    for(i = strlen("host:"); i < length; ++i) {
+        if(line[i] == ' ')
+            continue;
+        break;
+    }
+    if(i+strlen(serv->host) > length)
+        return 0;
+    if(strncmp(line+i, serv->host, strlen(serv->host)))
+        return 0;
+    for(last_idx = i+strlen(serv->host); last_idx < length; ++last_idx) {
+        if(line[last_idx] == ' ')
+            continue;
+        else
+            break;
+    }
+    if(line[last_idx] == '\r'|| line[last_idx] == '\n')
+        return 1;
+    return 0;
+}
+
+static int match_protocols(const char *line, int length)
+{
+    int i;
+    /* skip extract path */
+    for(i = 4; i < length && line[i] != ' '; ++i)
+    {}
+    if(i >= length)
+        return 0;
+    ++i;
+    if(i+strlen("HTTP/1.1") > length)
+        return 0;
+    if(strncmp(line+i, "HTTP/1.1", strlen("HTTP/1.1")))
+        return 0;
+    for(i += strlen("HTTP/1.1"); i < length; ++i) {
+        if(line[i] == ' ')
+            continue;
+        if(line[i] == '\r' || line[i] == '\n')
+            return 1;
+        return 0;
+    }
+    return 0;
+}
+
+static char* extract_path(const char *line, int length)
+{
+    int i;
+    char *path;
+
+    for(i = 4; i < length && line[i] != ' '; ++i)
+    {}
+    if(i >= length)
+        return NULL;
+
+    length = i-4+1 ;
+    path = malloc(length);
+    memcpy(path, line+4, length-1);
+    path[length-1] = '\0';
+    return path;
+}
+
+static int command_processing(struct server *serv, struct session *cur_session,
+                           const char *line, int length)
+{
+    switch(cur_session->state) {
+    case header_start:
+        if(length > strlen("GET") && !strncmp(line, "GET", strlen("GET"))) {
+            cur_session->path = extract_path(line, length);
+            if(cur_session->path == NULL)
+                return 0;
+            if(!match_protocols(line, length))
+                return 0;
+            cur_session->state = waiting_host;
+            return 1;
+        }
+    case waiting_host:
+        if(!match_hosts(serv, line, length))
+            return 0;
+        cur_session->state = empty_line;
+        return 1;
+    case empty_line:
+        if(line == NULL) {
+            cur_session->data_transfer_status = 1;
+            cur_session->state = writing_header;
+            return 1;
+        }
+    default:
+        return 0;
+    }
+}
+
+/*
+ * 0 - close current session
+ * 1 - continue
+ */
+static int read_in_session(struct server *serv, struct session *cur_session)
+{
+    int read_res, i, end_idx;
+    char *line = NULL;
+    end_idx = -1;
+
+    if(!cur_session->in_buf_used)
+        read_res = read(cur_session->fd, cur_session->in_buffer, INBUFSIZE);
+    if(read_res <= 0)
+        return 0;
+
+    cur_session->in_buf_used += read_res;
+
+    do {
+        for(i = 0; i < cur_session->in_buf_used; ++i) {
+            if(cur_session->in_buffer[i] == '\n') {
+                end_idx = i;
+                break;
+            }
+        }
+        if(end_idx == -1) {
+            if(cur_session->in_buf_used == INBUFSIZE)
+                return 0;
+            return 1;
+        }
+        if(cur_session->state != empty_line) {
+            line = malloc(end_idx+1);
+            memcpy(line, cur_session->in_buffer, end_idx+1);
+        }
+        cur_session->in_buf_used -= i+1;
+        memmove(cur_session->in_buffer, cur_session->in_buffer+end_idx+1,
+                cur_session->in_buf_used);
+
+        /* skip the remaining data in the header */
+        if(cur_session->state == empty_line &&
+                strncmp(cur_session->in_buffer, "\r\n", 2))
+            continue;
+        else if(cur_session->state == empty_line &&
+                !strncmp(cur_session->in_buffer, "\r\n", 2))
+            cur_session->in_buf_used = 0;
+
+        if(!command_processing(serv, cur_session, line, end_idx)) {
+            cur_session->bad_request = 1;
+            cur_session->data_transfer_status = 1;
+            cur_session->state = writing_header;
+        }
+        if(line) {
+            free(line);
+            line = NULL;
+        }
+        if(cur_session->bad_request)
+            return 1;
+    } while(cur_session->in_buf_used);
+    return 1;
+}
+
+static void print_header(struct session *cur_session, char *status)
+{
+    write(cur_session->fd, status, strlen(status));
+}
+
+static int is_index_page(char *path)
+{
+    int i;
+    for(i = strlen(path)-1; i >= 0 && path[i] != '/'; --i) {
+        if(path[i] == '.')
+            return 0;
+    }
+    return 1;
+}
+
+static void remove_slash(char *root)
+{
+    int last_idx = strlen(root);
+    --last_idx;
+    if(root[last_idx] == '/')
+        root[last_idx] = '\0';
+}
+
+static int open_file(char *root, struct session *cur_session)
+{
+    int i, j;
+    int add_index_page = 0;
+    char *given_path = cur_session->path;
+    char *str_index_page = "index.html";
+    char new_path[FILENAME_SIZE];
+
+    remove_slash(root);
+    strncpy(new_path, root, strlen(root));
+    add_index_page = is_index_page(given_path) ? 1 : 0;
+    for(i = strlen(root), j = 0; i < FILENAME_SIZE &&
+                                            j < strlen(given_path); ++i, ++j)
+        new_path[i] = given_path[j];
+    if(add_index_page) {
+        for(j = 0; i < FILENAME_SIZE && j < strlen(str_index_page); ++i, ++j)
+            new_path[i] = str_index_page[j];
+    }
+    if(i < FILENAME_SIZE)
+        new_path[i] = '\0';
+    cur_session->rs_fd = open(new_path, O_RDONLY);
+    if(cur_session->rs_fd == -1)
+        return 0;
+    else return 1;
+}
+
+static void change_out_buffer(char *out_buffer, int *out_buf_used,
+                              int writed_size)
+{
+    memmove(out_buffer, out_buffer+writed_size, (*out_buffer)-writed_size);
+    *out_buf_used -= writed_size;
+}
+
+static void write_error_page(struct session *cur_session)
+{
+    int read_result;
+
+    read_result = read(cur_session->rs_fd, cur_session->out_buffer,
+                       OUTBUFSIZE);
+    write(cur_session->fd, cur_session->out_buffer, read_result);
+}
+
+static int file_open_condition(struct session *cur_session)
+{
+    return !cur_session->bad_request  && !cur_session->not_found &&
+            cur_session->rs_fd == -1;
+}
+
+static char* get_page_error_path(struct server *serv, char *page)
+{
+    char *new_path;
+
+    new_path = malloc(strlen(serv->resource_dir) + strlen(page));
+    strcpy(new_path, serv->resource_dir);
+    strcat(new_path, page);
+    return new_path;
+}
+
+static int write_in_session(struct server *serv, struct session *cur_session)
+{
+    int read_result, write_result, open_result;
+    char *page_error_path = NULL;
+
+    if(file_open_condition(cur_session)) {
+        open_result = open_file(serv->resource_dir, cur_session);
+        if(!open_result) {
+            cur_session->state = writing_header;
+            cur_session->not_found = 1;
+        }
+    }
+    switch(cur_session->state) {
+    case writing_header:
+        if(cur_session->bad_request)
+            print_header(cur_session, "HTTP/1.1 400 Bad Request\n\n");
+        else if(cur_session->not_found)
+            print_header(cur_session, "HTTP/1.1 404 Not Found\n\n");
+        else
+            print_header(cur_session, "HTTP/1.1 200 OK\n\n");
+        cur_session->state = writing_body;
+        return 1;
+    case writing_body:
+        /* ---------- error page write ---------- */
+        if(cur_session->bad_request)
+            page_error_path = get_page_error_path(serv, "/400.html");
+        else if(cur_session->not_found)
+            page_error_path = get_page_error_path(serv, "/404.html");
+
+        if(cur_session->bad_request || cur_session->not_found) {
+            cur_session->rs_fd = open(page_error_path, O_RDONLY);
+            if(cur_session->rs_fd == -1)
+                syslog(LOG_ERR, "can't find error page");
+            free(page_error_path);
+            write_error_page(cur_session);
+            return 0;
+        }
+        /* ---------- normal page write ---------- */
+
+        /* if buffer doesn't contain any data*/
+        if(!cur_session->out_buf_used) {
+            read_result = read(cur_session->rs_fd, cur_session->out_buffer,
+                               OUTBUFSIZE);
+            /* end of file */
+            if(!read_result) {
+                close(cur_session->rs_fd);
+                cur_session->rs_fd = -1;
+                cur_session->data_transfer_status = 0;
+                cur_session->state = header_start;
+                return 0;
+            }
+            cur_session->out_buf_used += read_result;
+        }
+        write_result = write(cur_session->fd, cur_session->out_buffer,
+                             cur_session->out_buf_used);
+
+        /* writed remaining some of data */
+        if(write_result < cur_session->out_buf_used)
+            change_out_buffer(cur_session->out_buffer,
+                              &cur_session->out_buf_used,
+                              write_result);
+        /* writed all data from out_buffer */
+        else
+            cur_session->out_buf_used = 0;
+        return 1;
+    default:
+        return 0;
+    }
+}
+
+static void close_session(struct server *serv, int fd)
+{
+    close(fd);
+    serv->session_array[fd]->fd = -1;
+    if(serv->session_array[fd]->path)
+        free(serv->session_array[fd]->path);
+    if(serv->session_array[fd]->rs_fd)
+        close(serv->session_array[fd]->rs_fd);
+    serv->session_array[fd] = NULL;
+}
+
+static int reading_condition(struct session *cur_session)
+{
+    return cur_session && !cur_session->data_transfer_status;
+}
+
+static int writing_condition(struct session *cur_session)
+{
+    return cur_session && cur_session->data_transfer_status;
+}
+
+int main_loop(struct server *serv)
+{
+    int i, maxfd, select_result, accept_result, read_result, write_result;
+    fd_set readfds, writefds;
+
+    for(;;) {
+        FD_ZERO(&readfds);
+        FD_ZERO(&writefds);
+        FD_SET(serv->listen_socket, &readfds);
+        maxfd = serv->listen_socket;
+        for(i = 0; i < serv->session_size; ++i) {
+            if(reading_condition(serv->session_array[i])) {
+                FD_SET(i, &readfds);
+                if(i > maxfd)
+                    maxfd = i;
+            }
+            if(writing_condition(serv->session_array[i])) {
+                FD_SET(i, &writefds);
+                if(i > maxfd)
+                    maxfd = i;
+            }
+        }
+
+        select_result = select(maxfd + 1, &readfds, &writefds, NULL, NULL);
+        if(!select_result) {
+            syslog(LOG_ERR, "select error");
+            return 3;
+        }
+
+        if(FD_ISSET(serv->listen_socket, &readfds)) {
+            accept_result = accept_client(serv);
+            if(!accept_result) {
+                syslog(LOG_ERR, "accept error");
+                return 4;
+            }
+        }
+
+        for(i = 0; i < serv->session_size; ++i) {
+            if(serv->session_array[i] && FD_ISSET(i, &readfds)) {
+                read_result = read_in_session(serv, serv->session_array[i]);
+                /* normal connection closure (by user or full of in_buffer) */
+                if(!read_result)
+                    close_session(serv, i);
+            }
+            if(serv->session_array[i] && FD_ISSET(i, &writefds)) {
+                write_result = write_in_session(serv, serv->session_array[i]);;
+                /*
+                 * Closing the connection if all data is written or
+                 * error 400 or 404 occurs
+                 */
+                if(!write_result)
+                    close_session(serv, i);
+            }
+        }
+    }
+}
+
+/*
+ * 0 - error
+ * 1 - success
+ */
+static int init_server(struct server *serv, int port, char *host,
+                       char *resource_dir)
+{
+    int opt, i;
+    struct sockaddr_in addr;
+
+    serv->host = host;
+    serv->resource_dir = resource_dir;
+
+    serv->listen_socket = socket(AF_INET, SOCK_STREAM, 0);
+    if(serv->listen_socket == -1)
+        return 0;
+
+    opt = 1;
+    setsockopt(serv->listen_socket, SOL_SOCKET, SO_REUSEADDR, &opt,
+               sizeof(opt));
+
+    addr.sin_family = AF_INET;
+    addr.sin_addr.s_addr = htonl(INADDR_ANY);
+    addr.sin_port = htons(port);
+
+    if(bind(serv->listen_socket, (struct sockaddr*) &addr, sizeof(addr)) == -1)
+        return 0;
+
+    serv->session_array = malloc(sizeof(serv->session_array) *
+                                INIT_SESS_ARR_SIZE);
+    serv->session_size = INIT_SESS_ARR_SIZE;
+    for(i = 0; i < INIT_SESS_ARR_SIZE; i++)
+        serv->session_array[i] = NULL;
+
+    listen(serv->listen_socket, LISTEN_QLEN);
+    return 1;
+}
+
+static void demonization()
+{
+    int pid;
+
+    close(0);
+    close(1);
+    close(2);
+    open("/dev/null", O_RDONLY);
+    open("/dev/null", O_WRONLY);
+    open("/dev/null", O_WRONLY);
+    chdir("/");
+    pid = fork();
+    if(pid)
+        exit(0);
+    setsid();
+    pid = fork();
+    if(pid)
+        exit(0);
+}
+
+int main(int argc, char **argv)
+{
+    unsigned short port;
+    struct server serv;
+
+    if(argc != 4) {
+        fprintf(stderr,
+                "Usage: <port> <host> <full_path/to/host_files\n");
+        return 1;
+    }
+    demonization();
+    openlog("scratko's http server", 0, LOG_USER);
+    syslog(LOG_INFO, "daemon started");
+    port = strtol(argv[1], NULL, 10);
+
+    if(!init_server(&serv, port, argv[2], argv[3])) {
+        syslog(LOG_ERR, "server initialization error");
+        return 2;
+    }
+    return main_loop(&serv);
+    syslog(LOG_INFO, "server terminated");
+}
diff --git a/test_files/400.html b/test_files/400.html
new file mode 100644
index 0000000..edfac25
--- /dev/null
+++ b/test_files/400.html
@@ -0,0 +1,7 @@
+<html>
+<head><title>400 Bad Request</title></head>
+<body>
+<center><h1>400 Bad Request</h1></center>
+<hr><center>scratko's server 1.0</center>
+</body>
+</html>
diff --git a/test_files/404.html b/test_files/404.html
new file mode 100644
index 0000000..e8286d3
--- /dev/null
+++ b/test_files/404.html
@@ -0,0 +1,7 @@
+<html>
+<head><title>404 Not Found</title></head>
+<body>
+<center><h1>404 Not Found</h1></center>
+<hr><center>scratko's server 1.0</center>
+</body>
+</html>
diff --git a/test_files/index.html b/test_files/index.html
new file mode 100644
index 0000000..1dfbbed
--- /dev/null
+++ b/test_files/index.html
@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>Welcome to nginx!</title>
+<style>
+    body {
+        width: 35em;
+        margin: 0 auto;
+        font-family: Tahoma, Verdana, Arial, sans-serif;
+    }
+</style>
+</head>
+<body>
+<h1>Welcome to scratko's server!</h1>
+<p>Test page.</p>
+</body>
+</html>
-- 
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