mongoose.c

// Copyright (c) 2004-2013 Sergey Lyubka <valenok@gmail.com>
// Copyright (c) 2013 Cesanta Software Limited
// All rights reserved
//
// This library is dual-licensed: you can redistribute it and/or modify
// it under the terms of the GNU General Public License version 2 as
// published by the Free Software Foundation. For the terms of this
// license, see <http://www.gnu.org/licenses/>.
//
// You are free to use this library under the terms of the GNU General
// Public License, but WITHOUT ANY WARRANTY; without even the implied
// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU General Public License for more details.
//
// Alternatively, you can license this library under a commercial
// license, as set out in <http://cesanta.com/products.html>.

#undef UNICODE                  // Use ANSI WinAPI functions
#undef _UNICODE                 // Use multibyte encoding on Windows
#define _MBCS                   // Use multibyte encoding on Windows
#define _INTEGRAL_MAX_BITS 64   // Enable _stati64() on Windows
#define _CRT_SECURE_NO_WARNINGS // Disable deprecation warning in VS2005+
#undef WIN32_LEAN_AND_MEAN      // Let windows.h always include winsock2.h
#define _XOPEN_SOURCE 600       // For flockfile() on Linux
#define __STDC_FORMAT_MACROS    // <inttypes.h> wants this for C++
#define __STDC_LIMIT_MACROS     // C++ wants that for INT64_MAX
#define _LARGEFILE_SOURCE       // Enable fseeko() and ftello() functions
#define _FILE_OFFSET_BITS 64    // Enable 64-bit file offsets

#ifdef _MSC_VER
#pragma warning (disable : 4127)  // FD_SET() emits warning, disable it
#pragma warning (disable : 4204)  // missing c99 support
#endif

#include <sys/types.h>
#include <sys/stat.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <assert.h>
#include <errno.h>
#include <time.h>
#include <ctype.h>
#include <stdarg.h>

#ifdef _WIN32
#include <windows.h>
#include <process.h>    // For _beginthread
#include <io.h>         // For _lseeki64
#include <direct.h>     // For _mkdir
typedef int socklen_t;
typedef HANDLE pid_t;
typedef SOCKET sock_t;
typedef unsigned char uint8_t;
typedef unsigned int uint32_t;
typedef unsigned short uint16_t;
typedef unsigned __int64 uint64_t;
typedef __int64   int64_t;
typedef CRITICAL_SECTION mutex_t;
typedef struct _stati64 file_stat_t;
#pragma comment(lib, "ws2_32.lib")
#define snprintf _snprintf
#define vsnprintf _vsnprintf
#define INT64_FMT  "I64d"
#define mutex_init(x) InitializeCriticalSection(x)
#define mutex_destroy(x) DeleteCriticalSection(x)
#define mutex_lock(x) EnterCriticalSection(x)
#define mutex_unlock(x) LeaveCriticalSection(x)
#define get_thread_id() ((unsigned long) GetCurrentThreadId())
#define S_ISDIR(x) ((x) & _S_IFDIR)
#define sleep(x) Sleep((x) * 1000)
#define stat(x, y) mg_stat((x), (y))
#define fopen(x, y) mg_fopen((x), (y))
#define open(x, y) mg_open((x), (y))
#define lseek(x, y, z) _lseeki64((x), (y), (z))
#define mkdir(x, y) _mkdir(x)
#define to64(x) _atoi64(x)
#define flockfile(x)
#define funlockfile(x)
#ifndef va_copy
#define va_copy(x,y) x = y
#endif // MINGW #defines va_copy
#ifndef __func__
#define STRX(x) #x
#define STR(x) STRX(x)
#define __func__ __FILE__ ":" STR(__LINE__)
#endif
#else
#include <dirent.h>
#include <inttypes.h>
#include <pthread.h>
#include <pwd.h>
#include <signal.h>
#include <unistd.h>
#include <netdb.h>
#include <arpa/inet.h>  // For inet_pton() when USE_IPV6 is defined
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/select.h>
#define closesocket(x) close(x)
typedef int sock_t;
typedef pthread_mutex_t mutex_t;
typedef struct stat file_stat_t;
#define mutex_init(x) pthread_mutex_init(x, NULL)
#define mutex_destroy(x) pthread_mutex_destroy(x)
#define mutex_lock(x) pthread_mutex_lock(x)
#define mutex_unlock(x) pthread_mutex_unlock(x)
#define get_thread_id() ((unsigned long) pthread_self())
#define INVALID_SOCKET ((sock_t) -1)
#define INT64_FMT PRId64
#define to64(x) strtoll(x, NULL, 10)
#define __cdecl
#define O_BINARY 0
#endif

#ifdef USE_SSL
// Following define gets rid of openssl deprecation messages
#define MAC_OS_X_VERSION_MIN_REQUIRED MAC_OS_X_VERSION_10_6

#ifdef USE_CYASSL
#include <openssl/ssl.h>
#else
typedef struct ssl_ctx_st SSL_CTX;
typedef struct ssl_st SSL;
typedef struct ssl_method_st SSL_METHOD;

extern void __cdecl SSL_free(SSL *);
extern int __cdecl SSL_accept(SSL *);
extern int __cdecl SSL_connect(SSL *);
extern int __cdecl SSL_read(SSL *, void *, int);
extern int __cdecl SSL_write(SSL *, const void *, int);
extern int __cdecl SSL_set_fd(SSL *, int);
extern SSL * __cdecl SSL_new(SSL_CTX *);
extern SSL_CTX * __cdecl SSL_CTX_new(SSL_METHOD *);
extern SSL_METHOD * __cdecl SSLv23_server_method(void);
extern int __cdecl SSL_library_init(void);
extern int __cdecl SSL_CTX_use_PrivateKey_file(SSL_CTX *, const char *, int);
extern int __cdecl SSL_CTX_use_certificate_file(SSL_CTX *, const char *, int);
extern int __cdecl SSL_CTX_use_certificate_chain_file(SSL_CTX *, const char *);
extern void __cdecl SSL_CTX_free(SSL_CTX *);
#endif
#endif

#include "mongoose.h"

struct ll { struct ll *prev, *next; };
#define LINKED_LIST_INIT(N)  ((N)->next = (N)->prev = (N))
#define LINKED_LIST_DECLARE_AND_INIT(H)  struct ll H = { &H, &H }
#define LINKED_LIST_ENTRY(P,T,N)  ((T *)((char *)(P) - offsetof(T, N)))
#define LINKED_LIST_IS_EMPTY(N)  ((N)->next == (N))
#define LINKED_LIST_FOREACH(H,N,T) \
  for (N = (H)->next, T = (N)->next; N != (H); N = (T), T = (N)->next)
#define LINKED_LIST_ADD_TO_FRONT(H,N) do { ((H)->next)->prev = (N); \
  (N)->next = ((H)->next);  (N)->prev = (H); (H)->next = (N); } while (0)
#define LINKED_LIST_ADD_TO_TAIL(H,N) do { ((H)->prev)->next = (N); \
  (N)->prev = ((H)->prev); (N)->next = (H); (H)->prev = (N); } while (0)
#define LINKED_LIST_REMOVE(N) do { ((N)->next)->prev = ((N)->prev); \
  ((N)->prev)->next = ((N)->next); LINKED_LIST_INIT(N); } while (0)

#define ARRAY_SIZE(array) (sizeof(array) / sizeof(array[0]))
#define MAX_REQUEST_SIZE 16384
#define IOBUF_SIZE 8192
#define MAX_PATH_SIZE 8192
#define LUA_SCRIPT_PATTERN "**.lp$"
#define CGI_ENVIRONMENT_SIZE 4096
#define MAX_CGI_ENVIR_VARS 64
#define ENV_EXPORT_TO_CGI "MONGOOSE_CGI"
#define PASSWORDS_FILE_NAME ".htpasswd"

#ifndef USE_WEBSOCKET_PING_INTERVAL
#define USE_WEBSOCKET_PING_INTERVAL 5
#endif

// Extra HTTP headers to send in every static file reply
#if !defined(USE_EXTRA_HTTP_HEADERS)
#define USE_EXTRA_HTTP_HEADERS ""
#endif

#ifndef USE_POST_SIZE_LIMIT
#define USE_POST_SIZE_LIMIT 0
#endif

#ifdef ENABLE_DBG
#define DBG(x) do { printf("%-20s ", __func__); printf x; putchar('\n'); \
  fflush(stdout); } while(0)
#else
#define DBG(x)
#endif

#ifdef NO_FILESYSTEM
#define NO_AUTH
#define NO_CGI
#define NO_DAV
#define NO_DIRECTORY_LISTING
#define NO_LOGGING
#endif

union socket_address {
  struct sockaddr sa;
  struct sockaddr_in sin;
#ifdef USE_IPV6
  struct sockaddr_in6 sin6;
#endif
};

struct vec {
  const char *ptr;
  int len;
};

struct uri_handler {
  struct ll link;
  char *uri;
  mg_handler_t handler;
};

// For directory listing and WevDAV support
struct dir_entry {
  struct connection *conn;
  char *file_name;
  file_stat_t st;
};

// NOTE(lsm): this enum shoulds be in sync with the config_options.
enum {
  ACCESS_CONTROL_LIST,
#ifndef NO_FILESYSTEM
  ACCESS_LOG_FILE, AUTH_DOMAIN, CGI_INTERPRETER,
  CGI_PATTERN, DAV_AUTH_FILE, DOCUMENT_ROOT, ENABLE_DIRECTORY_LISTING,
#endif
  EXTRA_MIME_TYPES,
#ifndef NO_FILESYSTEM
  GLOBAL_AUTH_FILE,
#endif
  HIDE_FILES_PATTERN,
  IDLE_TIMEOUT_MS,
#ifndef NO_FILESYSTEM
  INDEX_FILES,
#endif
  LISTENING_PORT,
#ifndef _WIN32
  RUN_AS_USER,
#endif
#ifdef USE_SSL
  SSL_CERTIFICATE,
#endif
  URL_REWRITES, NUM_OPTIONS
};

static const char *static_config_options[] = {
  "access_control_list", NULL,
#ifndef NO_FILESYSTEM
  "access_log_file", NULL,
  "auth_domain", "mydomain.com",
  "cgi_interpreter", NULL,
  "cgi_pattern", "**.cgi$|**.pl$|**.php$",
  "dav_auth_file", NULL,
  "document_root",  NULL,
  "enable_directory_listing", "yes",
#endif
  "extra_mime_types", NULL,
#ifndef NO_FILESYSTEM
  "global_auth_file", NULL,
#endif
  "hide_files_patterns", NULL,
  "idle_timeout_ms", "30000",
#ifndef NO_FILESYSTEM
  "index_files","index.html,index.htm,index.cgi,index.php,index.lp",
#endif
  "listening_port", NULL,
#ifndef _WIN32
  "run_as_user", NULL,
#endif
#ifdef USE_SSL
  "ssl_certificate", NULL,
#endif
  "url_rewrites", NULL,
  NULL
};

struct mg_server {
  sock_t listening_sock;
  union socket_address lsa;   // Listening socket address
  struct ll active_connections;
  struct ll uri_handlers;
  mg_handler_t error_handler;
  char *config_options[NUM_OPTIONS];
  void *server_data;
  void *ssl_ctx;    // SSL context
  sock_t ctl[2];    // Control socketpair. Used to wake up from select() call
};

// Expandable IO buffer
struct iobuf {
  char *buf;    // Buffer that holds the data
  int size;     // Buffer size
  int len;      // Number of bytes currently in a buffer
};

// Local endpoint representation
union endpoint {
  int fd;                   // Opened regular local file
  sock_t cgi_sock;          // CGI socket
  void *ssl;                // SSL descriptor
  struct uri_handler *uh;   // URI handler user function
};

enum endpoint_type { EP_NONE, EP_FILE, EP_CGI, EP_USER, EP_PUT };
enum connection_flags {
  CONN_CLOSE = 1, CONN_SPOOL_DONE = 2, CONN_SSL_HANDS_SHAKEN = 4,
  CONN_HEADERS_SENT = 8, CONN_BUFFER = 16
};

struct connection {
  struct mg_connection mg_conn;   // XXX: Must be first
  struct ll link;                 // Linkage to server->active_connections
  struct mg_server *server;
  sock_t client_sock;             // Connected client
  struct iobuf local_iobuf;
  struct iobuf remote_iobuf;
  union endpoint endpoint;
  enum endpoint_type endpoint_type;
  time_t birth_time;
  time_t last_activity_time;
  char *path_info;
  char *request;
  int64_t num_bytes_sent; // Total number of bytes sent
  int64_t cl;             // Reply content length, for Range support
  int request_len;  // Request length, including last \r\n after last header
  int flags;        // CONN_* flags: CONN_CLOSE, CONN_SPOOL_DONE, etc
  void *ssl;        // SSL descriptor
};

static void close_local_endpoint(struct connection *conn);

static const struct {
  const char *extension;
  size_t ext_len;
  const char *mime_type;
} static_builtin_mime_types[] = {
  {".html", 5, "text/html"},
  {".htm", 4, "text/html"},
  {".shtm", 5, "text/html"},
  {".shtml", 6, "text/html"},
  {".css", 4, "text/css"},
  {".js",  3, "application/x-javascript"},
  {".ico", 4, "image/x-icon"},
  {".gif", 4, "image/gif"},
  {".jpg", 4, "image/jpeg"},
  {".jpeg", 5, "image/jpeg"},
  {".png", 4, "image/png"},
  {".svg", 4, "image/svg+xml"},
  {".txt", 4, "text/plain"},
  {".torrent", 8, "application/x-bittorrent"},
  {".wav", 4, "audio/x-wav"},
  {".mp3", 4, "audio/x-mp3"},
  {".mid", 4, "audio/mid"},
  {".m3u", 4, "audio/x-mpegurl"},
  {".ogg", 4, "application/ogg"},
  {".ram", 4, "audio/x-pn-realaudio"},
  {".xml", 4, "text/xml"},
  {".json",  5, "text/json"},
  {".xslt", 5, "application/xml"},
  {".xsl", 4, "application/xml"},
  {".ra",  3, "audio/x-pn-realaudio"},
  {".doc", 4, "application/msword"},
  {".exe", 4, "application/octet-stream"},
  {".zip", 4, "application/x-zip-compressed"},
  {".xls", 4, "application/excel"},
  {".tgz", 4, "application/x-tar-gz"},
  {".tar", 4, "application/x-tar"},
  {".gz",  3, "application/x-gunzip"},
  {".arj", 4, "application/x-arj-compressed"},
  {".rar", 4, "application/x-arj-compressed"},
  {".rtf", 4, "application/rtf"},
  {".pdf", 4, "application/pdf"},
  {".swf", 4, "application/x-shockwave-flash"},
  {".mpg", 4, "video/mpeg"},
  {".webm", 5, "video/webm"},
  {".mpeg", 5, "video/mpeg"},
  {".mov", 4, "video/quicktime"},
  {".mp4", 4, "video/mp4"},
  {".m4v", 4, "video/x-m4v"},
  {".asf", 4, "video/x-ms-asf"},
  {".avi", 4, "video/x-msvideo"},
  {".bmp", 4, "image/bmp"},
  {".ttf", 4, "application/x-font-ttf"},
  {NULL,  0, NULL}
};

#ifndef NO_THREADS
void *mg_start_thread(void *(*f)(void *), void *p) {
#ifdef _WIN32
  return (void *) _beginthread((void (__cdecl *)(void *)) f, 0, p);
#else
  pthread_t thread_id = (pthread_t) 0;
  pthread_attr_t attr;

  (void) pthread_attr_init(&attr);
  (void) pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);

#if USE_STACK_SIZE > 1
  // Compile-time option to control stack size, e.g. -DUSE_STACK_SIZE=16384
  (void) pthread_attr_setstacksize(&attr, USE_STACK_SIZE);
#endif

  pthread_create(&thread_id, &attr, f, p);
  pthread_attr_destroy(&attr);

  return (void *) thread_id;
#endif
}
#endif  // NO_THREADS

#ifdef _WIN32
// Encode 'path' which is assumed UTF-8 string, into UNICODE string.
// wbuf and wbuf_len is a target buffer and its length.
static void to_wchar(const char *path, wchar_t *wbuf, size_t wbuf_len) {
  char buf[MAX_PATH_SIZE * 2], buf2[MAX_PATH_SIZE * 2], *p;

  strncpy(buf, path, sizeof(buf));
  buf[sizeof(buf) - 1] = '\0';

  // Trim trailing slashes
  p = buf + strlen(buf) - 1;
  while (p > buf && p[0] == '\\' || p[0] == '/') *p-- = '\0';
  //change_slashes_to_backslashes(buf);

  // Convert to Unicode and back. If doubly-converted string does not
  // match the original, something is fishy, reject.
  memset(wbuf, 0, wbuf_len * sizeof(wchar_t));
  MultiByteToWideChar(CP_UTF8, 0, buf, -1, wbuf, (int) wbuf_len);
  WideCharToMultiByte(CP_UTF8, 0, wbuf, (int) wbuf_len, buf2, sizeof(buf2),
                      NULL, NULL);
  if (strcmp(buf, buf2) != 0) {
    wbuf[0] = L'\0';
  }
}

static int mg_stat(const char *path, file_stat_t *st) {
  wchar_t wpath[MAX_PATH_SIZE];
  to_wchar(path, wpath, ARRAY_SIZE(wpath));
  DBG(("[%ls] -> %d", wpath, _wstati64(wpath, st)));
  return _wstati64(wpath, st);
}

static FILE *mg_fopen(const char *path, const char *mode) {
  wchar_t wpath[MAX_PATH_SIZE], wmode[10];
  to_wchar(path, wpath, ARRAY_SIZE(wpath));
  to_wchar(mode, wmode, ARRAY_SIZE(wmode));
  return _wfopen(wpath, wmode);
}

static int mg_open(const char *path, int flag) {
  wchar_t wpath[MAX_PATH_SIZE];
  to_wchar(path, wpath, ARRAY_SIZE(wpath));
  return _wopen(wpath, flag);
}
#endif

static void set_close_on_exec(int fd) {
#ifdef _WIN32
  (void) SetHandleInformation((HANDLE) fd, HANDLE_FLAG_INHERIT, 0);
#else
  fcntl(fd, F_SETFD, FD_CLOEXEC);
#endif
}

static void set_non_blocking_mode(sock_t sock) {
#ifdef _WIN32
  unsigned long on = 1;
  ioctlsocket(sock, FIONBIO, &on);
#else
  int flags = fcntl(sock, F_GETFL, 0);
  fcntl(sock, F_SETFL, flags | O_NONBLOCK);
#endif
}

// A helper function for traversing a comma separated list of values.
// It returns a list pointer shifted to the next value, or NULL if the end
// of the list found.
// Value is stored in val vector. If value has form "x=y", then eq_val
// vector is initialized to point to the "y" part, and val vector length
// is adjusted to point only to "x".
static const char *next_option(const char *list, struct vec *val,
                               struct vec *eq_val) {
  if (list == NULL || *list == '\0') {
    // End of the list
    list = NULL;
  } else {
    val->ptr = list;
    if ((list = strchr(val->ptr, ',')) != NULL) {
      // Comma found. Store length and shift the list ptr
      val->len = list - val->ptr;
      list++;
    } else {
      // This value is the last one
      list = val->ptr + strlen(val->ptr);
      val->len = list - val->ptr;
    }

    if (eq_val != NULL) {
      // Value has form "x=y", adjust pointers and lengths
      // so that val points to "x", and eq_val points to "y".
      eq_val->len = 0;
      eq_val->ptr = (const char *) memchr(val->ptr, '=', val->len);
      if (eq_val->ptr != NULL) {
        eq_val->ptr++;  // Skip over '=' character
        eq_val->len = val->ptr + val->len - eq_val->ptr;
        val->len = (eq_val->ptr - val->ptr) - 1;
      }
    }
  }

  return list;
}

static int spool(struct iobuf *io, const void *buf, int len) {
  static const double mult = 1.2;
  char *p = NULL;
  int new_len = 0;

  assert(io->len >= 0);
  assert(io->len <= io->size);

  //DBG(("1. %d %d %d", len, io->len, io->size));
  if (len <= 0) {
  } else if ((new_len = io->len + len) < io->size) {
    memcpy(io->buf + io->len, buf, len);
    io->len = new_len;
  } else if ((p = (char *) realloc(io->buf, (int) (new_len * mult))) != NULL) {
    io->buf = p;
    memcpy(io->buf + io->len, buf, len);
    io->len = new_len;
    io->size = (int) (new_len * mult);
  } else {
    len = 0;
  }
  //DBG(("%d %d %d", len, io->len, io->size));

  return len;
}

// Like snprintf(), but never returns negative value, or a value
// that is larger than a supplied buffer.
static int mg_vsnprintf(char *buf, size_t buflen, const char *fmt, va_list ap) {
  int n;
  if (buflen < 1) return 0;
  n = vsnprintf(buf, buflen, fmt, ap);
  if (n < 0) {
    n = 0;
  } else if (n >= (int) buflen) {
    n = (int) buflen - 1;
  }
  buf[n] = '\0';
  return n;
}

static int mg_snprintf(char *buf, size_t buflen, const char *fmt, ...) {
  va_list ap;
  int n;
  va_start(ap, fmt);
  n = mg_vsnprintf(buf, buflen, fmt, ap);
  va_end(ap);
  return n;
}

// Check whether full request is buffered. Return:
//   -1  if request is malformed
//    0  if request is not yet fully buffered
//   >0  actual request length, including last \r\n\r\n
static int get_request_len(const char *s, int buf_len) {
  const unsigned char *buf = (unsigned char *) s;
  int i;

  for (i = 0; i < buf_len; i++) {
    // Control characters are not allowed but >=128 are.
    // Abort scan as soon as one malformed character is found.
    if (!isprint(buf[i]) && buf[i] != '\r' && buf[i] != '\n' && buf[i] < 128) {
      return -1;
    } else if (buf[i] == '\n' && i + 1 < buf_len && buf[i + 1] == '\n') {
      return i + 2;
    } else if (buf[i] == '\n' && i + 2 < buf_len && buf[i + 1] == '\r' &&
               buf[i + 2] == '\n') {
      return i + 3;
    }
  }

  return 0;
}

// Skip the characters until one of the delimiters characters found.
// 0-terminate resulting word. Skip the rest of the delimiters if any.
// Advance pointer to buffer to the next word. Return found 0-terminated word.
static char *skip(char **buf, const char *delimiters) {
  char *p, *begin_word, *end_word, *end_delimiters;

  begin_word = *buf;
  end_word = begin_word + strcspn(begin_word, delimiters);
  end_delimiters = end_word + strspn(end_word, delimiters);

  for (p = end_word; p < end_delimiters; p++) {
    *p = '\0';
  }

  *buf = end_delimiters;

  return begin_word;
}

// Parse HTTP headers from the given buffer, advance buffer to the point
// where parsing stopped.
static void parse_http_headers(char **buf, struct mg_connection *ri) {
  size_t i;

  for (i = 0; i < ARRAY_SIZE(ri->http_headers); i++) {
    ri->http_headers[i].name = skip(buf, ": ");
    ri->http_headers[i].value = skip(buf, "\r\n");
    if (ri->http_headers[i].name[0] == '\0')
      break;
    ri->num_headers = i + 1;
  }
}

static const char *status_code_to_str(int status_code) {
  switch (status_code) {
    case 200: return "OK";
    case 201: return "Created";
    case 204: return "No Content";
    case 301: return "Moved Permanently";
    case 302: return "Found";
    case 304: return "Not Modified";
    case 400: return "Bad Request";
    case 403: return "Forbidden";
    case 404: return "Not Found";
    case 405: return "Method Not Allowed";
    case 409: return "Conflict";
    case 411: return "Length Required";
    case 413: return "Request Entity Too Large";
    case 415: return "Unsupported Media Type";
    case 423: return "Locked";
    case 500: return "Server Error";
    case 501: return "Not Implemented";
    default:  return "Server Error";
  }
}

static void send_http_error(struct connection *conn, int code,
                            const char *fmt, ...) {
  const char *message = status_code_to_str(code);
  const char *rewrites = conn->server->config_options[URL_REWRITES];
  char headers[200], body[200];
  struct vec a, b;
  va_list ap;
  int body_len, headers_len, match_code;

  conn->mg_conn.status_code = code;

  // Invoke error handler if it is set
  if (conn->server->error_handler != NULL &&
      conn->server->error_handler(&conn->mg_conn)) {
    close_local_endpoint(conn);
    return;
  }

  // Handle error code rewrites
  while ((rewrites = next_option(rewrites, &a, &b)) != NULL) {
    if ((match_code = atoi(a.ptr)) > 0 && match_code == code) {
      conn->mg_conn.status_code = 302;
      mg_printf(&conn->mg_conn, "HTTP/1.1 %d Moved\r\n"
                "Location: %.*s?code=%d&orig_uri=%s\r\n\r\n",
                conn->mg_conn.status_code, b.len, b.ptr, code,
                conn->mg_conn.uri);
      close_local_endpoint(conn);
      return;
    }
  }

  body_len = mg_snprintf(body, sizeof(body), "%d %s\n", code, message);
  if (fmt != NULL) {
    body[body_len++] = '\n';
    va_start(ap, fmt);
    body_len += mg_snprintf(body + body_len, sizeof(body) - body_len, fmt, ap);
    va_end(ap);
  }
  if (code >= 300 && code <= 399) {
    // 3xx errors do not have body
    body_len = 0;
  }
  headers_len = mg_snprintf(headers, sizeof(headers),
                            "HTTP/1.1 %d %s\r\nContent-Length: %d\r\n"
                            "Content-Type: text/plain\r\n\r\n",
                            code, message, body_len);
  spool(&conn->remote_iobuf, headers, headers_len);
  spool(&conn->remote_iobuf, body, body_len);
  close_local_endpoint(conn);  // This will write to the log file
}

// Print message to buffer. If buffer is large enough to hold the message,
// return buffer. If buffer is to small, allocate large enough buffer on heap,
// and return allocated buffer.
static int alloc_vprintf(char **buf, size_t size, const char *fmt, va_list ap) {
  va_list ap_copy;
  int len;

  // Windows is not standard-compliant, and vsnprintf() returns -1 if
  // buffer is too small. Also, older versions of msvcrt.dll do not have
  // _vscprintf().  However, if size is 0, vsnprintf() behaves correctly.
  // Therefore, we make two passes: on first pass, get required message length.
  // On second pass, actually print the message.
  va_copy(ap_copy, ap);
  len = vsnprintf(NULL, 0, fmt, ap_copy);

  if (len > (int) size &&
      (size = len + 1) > 0 &&
      (*buf = (char *) malloc(size)) == NULL) {
    len = -1;  // Allocation failed, mark failure
  } else {
    va_copy(ap_copy, ap);
    vsnprintf(*buf, size, fmt, ap_copy);
  }

  return len;
}

static void write_chunk(struct connection *conn, const char *buf, int len) {
  char chunk_size[50];
  int n = mg_snprintf(chunk_size, sizeof(chunk_size), "%X\r\n", len);
  spool(&conn->remote_iobuf, chunk_size, n);
  spool(&conn->remote_iobuf, buf, len);
  spool(&conn->remote_iobuf, "\r\n", 2);
}

int mg_vprintf(struct mg_connection *conn, const char *fmt, va_list ap,
               int chunked) {
  char mem[IOBUF_SIZE], *buf = mem;
  int len;

  if ((len = alloc_vprintf(&buf, sizeof(mem), fmt, ap)) > 0) {
    if (chunked) {
      write_chunk((struct connection *) conn, buf, len);
    } else {
      len = mg_write(conn, buf, (size_t) len);
    }
  }
  if (buf != mem && buf != NULL) {
    free(buf);
  }

  return len;
}

int mg_printf(struct mg_connection *conn, const char *fmt, ...) {
  int len;
  va_list ap;
  va_start(ap, fmt);
  len = mg_vprintf(conn, fmt, ap, 0);
  va_end(ap);
  return len;
}

static int mg_socketpair(sock_t sp[2]) {
  struct sockaddr_in sa;
  sock_t sock, ret = -1;
  socklen_t len = sizeof(sa);

  sp[0] = sp[1] = INVALID_SOCKET;

  (void) memset(&sa, 0, sizeof(sa));
  sa.sin_family = AF_INET;
  sa.sin_port = htons(0);
  sa.sin_addr.s_addr = htonl(0x7f000001);

  if ((sock = socket(AF_INET, SOCK_STREAM, 0)) != INVALID_SOCKET &&
      !bind(sock, (struct sockaddr *) &sa, len) &&
      !listen(sock, 1) &&
      !getsockname(sock, (struct sockaddr *) &sa, &len) &&
      (sp[0] = socket(AF_INET, SOCK_STREAM, 6)) != -1 &&
      !connect(sp[0], (struct sockaddr *) &sa, len) &&
      (sp[1] = accept(sock,(struct sockaddr *) &sa, &len)) != INVALID_SOCKET) {
    set_close_on_exec(sp[0]);
    set_close_on_exec(sp[1]);
    ret = 0;
  } else {
    if (sp[0] != INVALID_SOCKET) closesocket(sp[0]);
    if (sp[1] != INVALID_SOCKET) closesocket(sp[1]);
    sp[0] = sp[1] = INVALID_SOCKET;
  }
  closesocket(sock);

  return ret;
}

static int is_error(int n) {
  return n == 0 || (n < 0 && errno != EINTR && errno != EAGAIN);
}

#ifndef NO_CGI
#ifdef _WIN32
struct threadparam {
  sock_t s;
  HANDLE hPipe;
};

static int wait_until_ready(sock_t sock, int for_read) {
  fd_set set;
  FD_ZERO(&set);
  FD_SET(sock, &set);
  select(sock + 1, for_read ? &set : 0, for_read ? 0 : &set, 0, 0);
  return 1;
}

static void *push_to_stdin(void *arg) {
  struct threadparam *tp = arg;
  int n, sent, stop = 0;
  DWORD k;
  char buf[IOBUF_SIZE];

  while (!stop && wait_until_ready(tp->s, 1) &&
         (n = recv(tp->s, buf, sizeof(buf), 0)) > 0) {
    if (n == -1 && GetLastError() == WSAEWOULDBLOCK) continue;
    for (sent = 0; !stop && sent < n; sent += k) {
      if (!WriteFile(tp->hPipe, buf + sent, n - sent, &k, 0)) stop = 1;
    }
  }
  DBG(("%s", "FORWARED EVERYTHING TO CGI"));
  CloseHandle(tp->hPipe);
  free(tp);
  _endthread();
  return NULL;
}

static void *pull_from_stdout(void *arg) {
  struct threadparam *tp = arg;
  int k, stop = 0;
  DWORD n, sent;
  char buf[IOBUF_SIZE];

  while (!stop && ReadFile(tp->hPipe, buf, sizeof(buf), &n, NULL)) {
    for (sent = 0; !stop && sent < n; sent += k) {
      if (wait_until_ready(tp->s, 0) &&
          (k = send(tp->s, buf + sent, n - sent, 0)) <= 0) stop = 1;
    }
  }
  DBG(("%s", "EOF FROM CGI"));
  CloseHandle(tp->hPipe);
  shutdown(tp->s, 2);  // Without this, IO thread may get truncated data
  closesocket(tp->s);
  free(tp);
  _endthread();
  return NULL;
}

static void spawn_stdio_thread(sock_t sock, HANDLE hPipe,
                               void *(*func)(void *)) {
  struct threadparam *tp = malloc(sizeof(*tp));
  if (tp != NULL) {
    tp->s = sock;
    tp->hPipe = hPipe;
    mg_start_thread(func, tp);
  }
}

static void abs_path(const char *utf8_path, char *abs_path, size_t len) {
  wchar_t buf[MAX_PATH_SIZE], buf2[MAX_PATH_SIZE];
  to_wchar(utf8_path, buf, ARRAY_SIZE(buf));
  GetFullPathNameW(buf, ARRAY_SIZE(buf2), buf2, NULL);
  WideCharToMultiByte(CP_UTF8, 0, buf2, wcslen(buf2) + 1, abs_path, len, 0, 0);
}

static pid_t start_process(char *interp, const char *cmd, const char *env,
                           const char *envp[], const char *dir, sock_t sock) {
  STARTUPINFOW si = {0};
  PROCESS_INFORMATION pi = {0};
  HANDLE a[2], b[2], me = GetCurrentProcess();
  wchar_t wcmd[MAX_PATH_SIZE], full_dir[MAX_PATH_SIZE];
  char buf[MAX_PATH_SIZE], buf4[MAX_PATH_SIZE], buf5[MAX_PATH_SIZE],
       cmdline[MAX_PATH_SIZE], *p;
  DWORD flags = DUPLICATE_CLOSE_SOURCE | DUPLICATE_SAME_ACCESS;
  FILE *fp;

  si.cb = sizeof(si);
  si.dwFlags = STARTF_USESTDHANDLES | STARTF_USESHOWWINDOW;
  si.wShowWindow = SW_HIDE;
  si.hStdError = GetStdHandle(STD_ERROR_HANDLE);

  CreatePipe(&a[0], &a[1], NULL, 0);
  CreatePipe(&b[0], &b[1], NULL, 0);
  DuplicateHandle(me, a[0], me, &si.hStdInput, 0, TRUE, flags);
  DuplicateHandle(me, b[1], me, &si.hStdOutput, 0, TRUE, flags);

  if (interp == NULL && (fp = fopen(cmd, "r")) != NULL) {
    buf[0] = buf[1] = '\0';
    fgets(buf, sizeof(buf), fp);
    buf[sizeof(buf) - 1] = '\0';
    if (buf[0] == '#' && buf[1] == '!') {
      interp = buf + 2;
      for (p = interp + strlen(interp);
           isspace(* (uint8_t *) p) && p > interp; p--) *p = '\0';
    }
    fclose(fp);
  }

  if (interp != NULL) {
    abs_path(interp, buf4, ARRAY_SIZE(buf4));
    interp = buf4;
  }
  abs_path(dir, buf5, ARRAY_SIZE(buf5));
  to_wchar(dir, full_dir, ARRAY_SIZE(full_dir));
  mg_snprintf(cmdline, sizeof(cmdline), "%s%s\"%s\"",
              interp ? interp : "", interp ? " " : "", cmd);
  to_wchar(cmdline, wcmd, ARRAY_SIZE(wcmd));

  if (CreateProcessW(NULL, wcmd, NULL, NULL, TRUE, CREATE_NEW_PROCESS_GROUP,
                     (void *) env, full_dir, &si, &pi) != 0) {
    spawn_stdio_thread(sock, a[1], push_to_stdin);
    spawn_stdio_thread(sock, b[0], pull_from_stdout);
  } else {
    CloseHandle(a[1]);
    CloseHandle(b[0]);
    closesocket(sock);
  }
  DBG(("CGI command: [%ls] -> %p", wcmd, pi.hProcess));

  CloseHandle(si.hStdOutput);
  CloseHandle(si.hStdInput);
  CloseHandle(a[0]);
  CloseHandle(b[1]);
  CloseHandle(pi.hThread);
  CloseHandle(pi.hProcess);

  return pi.hProcess;
}
#else
static pid_t start_process(const char *interp, const char *cmd, const char *env,
                           const char *envp[], const char *dir, sock_t sock) {
  char buf[500];
  pid_t pid = fork();
  (void) env;

  if (pid == 0) {
    chdir(dir);
    dup2(sock, 0);
    dup2(sock, 1);
    closesocket(sock);

    // After exec, all signal handlers are restored to their default values,
    // with one exception of SIGCHLD. According to POSIX.1-2001 and Linux's
    // implementation, SIGCHLD's handler will leave unchanged after exec
    // if it was set to be ignored. Restore it to default action.
    signal(SIGCHLD, SIG_DFL);

    if (interp == NULL) {
      execle(cmd, cmd, NULL, envp);
    } else {
      execle(interp, interp, cmd, NULL, envp);
    }
    snprintf(buf, sizeof(buf), "Status: 500\r\n\r\n"
             "500 Server Error: %s%s%s: %s", interp == NULL ? "" : interp,
             interp == NULL ? "" : " ", cmd, strerror(errno));
    send(1, buf, strlen(buf), 0);
    exit(EXIT_FAILURE);  // exec call failed
  }

  return pid;
}
#endif  // _WIN32

// This structure helps to create an environment for the spawned CGI program.
// Environment is an array of "VARIABLE=VALUE\0" ASCIIZ strings,
// last element must be NULL.
// However, on Windows there is a requirement that all these VARIABLE=VALUE\0
// strings must reside in a contiguous buffer. The end of the buffer is
// marked by two '\0' characters.
// We satisfy both worlds: we create an envp array (which is vars), all
// entries are actually pointers inside buf.
struct cgi_env_block {
  struct mg_connection *conn;
  char buf[CGI_ENVIRONMENT_SIZE];       // Environment buffer
  const char *vars[MAX_CGI_ENVIR_VARS]; // char *envp[]
  int len;                              // Space taken
  int nvars;                            // Number of variables in envp[]
};

// Append VARIABLE=VALUE\0 string to the buffer, and add a respective
// pointer into the vars array.
static char *addenv(struct cgi_env_block *block, const char *fmt, ...) {
  int n, space;
  char *added;
  va_list ap;

  // Calculate how much space is left in the buffer
  space = sizeof(block->buf) - block->len - 2;
  assert(space >= 0);

  // Make a pointer to the free space int the buffer
  added = block->buf + block->len;