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>.

#if defined(_WIN32)
#undef _UNICODE
#define _MBCS
#if !defined(_CRT_SECURE_NO_WARNINGS)
#define _CRT_SECURE_NO_WARNINGS // Disable deprecation warning in VS2005
#endif
#else
#ifdef __linux__
#define _XOPEN_SOURCE 600     // For flockfile() on Linux
#endif
#if !defined(_LARGEFILE_SOURCE)
#define _LARGEFILE_SOURCE     // Enable 64-bit file offsets
#endif
#define __STDC_FORMAT_MACROS  // <inttypes.h> wants this for C++
#define __STDC_LIMIT_MACROS   // C++ wants that for INT64_MAX
#endif

#if defined (_MSC_VER)
// conditional expression is constant: introduced by FD_SET(..)
#pragma warning (disable : 4127)
// non-constant aggregate initializer: issued due to missing C99 support
#pragma warning (disable : 4204)
#endif

// Disable WIN32_LEAN_AND_MEAN.
// This makes windows.h always include winsock2.h
#ifdef WIN32_LEAN_AND_MEAN
#undef WIN32_LEAN_AND_MEAN
#endif

#if defined(__SYMBIAN32__)
#define NO_SSL // SSL is not supported
#define NO_CGI // CGI is not supported
#define PATH_MAX FILENAME_MAX
#endif // __SYMBIAN32__

#ifndef _WIN32_WCE // Some ANSI #includes are not available on Windows CE
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <signal.h>
#include <fcntl.h>
#endif // !_WIN32_WCE

#include <time.h>
#include <stdlib.h>
#include <stdarg.h>
#include <assert.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>
#include <stddef.h>
#include <stdio.h>

#if defined(_WIN32) && !defined(__SYMBIAN32__) // Windows specific
#undef _WIN32_WINNT
#define _WIN32_WINNT 0x0400 // To make it link in VS2005
#include <windows.h>

#ifndef PATH_MAX
#define PATH_MAX MAX_PATH
#endif

#ifndef _WIN32_WCE
#include <process.h>
#include <direct.h>
#include <io.h>
#else // _WIN32_WCE
#define NO_CGI // WinCE has no pipes

typedef long off_t;

#define errno   GetLastError()
#define strerror(x)  _ultoa(x, (char *) _alloca(sizeof(x) *3 ), 10)
#endif // _WIN32_WCE

#define MAKEUQUAD(lo, hi) ((uint64_t)(((uint32_t)(lo)) | \
      ((uint64_t)((uint32_t)(hi))) << 32))
#define RATE_DIFF 10000000 // 100 nsecs
#define EPOCH_DIFF MAKEUQUAD(0xd53e8000, 0x019db1de)
#define SYS2UNIX_TIME(lo, hi) \
  (time_t) ((MAKEUQUAD((lo), (hi)) - EPOCH_DIFF) / RATE_DIFF)

// Visual Studio 6 does not know __func__ or __FUNCTION__
// The rest of MS compilers use __FUNCTION__, not C99 __func__
// Also use _strtoui64 on modern M$ compilers
#if defined(_MSC_VER) && _MSC_VER < 1300
#define STRX(x) #x
#define STR(x) STRX(x)
#define __func__ __FILE__ ":" STR(__LINE__)
#define strtoull(x, y, z) (unsigned __int64) _atoi64(x)
#define strtoll(x, y, z) _atoi64(x)
#else
#define __func__  __FUNCTION__
#define strtoull(x, y, z) _strtoui64(x, y, z)
#define strtoll(x, y, z) _strtoi64(x, y, z)
#endif // _MSC_VER

#define ERRNO   GetLastError()
#define NO_SOCKLEN_T
#define SSL_LIB   "ssleay32.dll"
#define CRYPTO_LIB  "libeay32.dll"
#define O_NONBLOCK  0
#if !defined(EWOULDBLOCK)
#define EWOULDBLOCK  WSAEWOULDBLOCK
#endif // !EWOULDBLOCK
#define _POSIX_
#define INT64_FMT  "I64d"

#define WINCDECL __cdecl
#define SHUT_WR 1
#define snprintf _snprintf
#define vsnprintf _vsnprintf
#define mg_sleep(x) Sleep(x)

#define pipe(x) _pipe(x, MG_BUF_LEN, _O_BINARY)
#ifndef popen
#define popen(x, y) _popen(x, y)
#endif
#ifndef pclose
#define pclose(x) _pclose(x)
#endif
#define close(x) _close(x)
#define dlsym(x,y) GetProcAddress((HINSTANCE) (x), (y))
#define RTLD_LAZY  0
#define fseeko(x, y, z) _lseeki64(_fileno(x), (y), (z))
#define fdopen(x, y) _fdopen((x), (y))
#define write(x, y, z) _write((x), (y), (unsigned) z)
#define read(x, y, z) _read((x), (y), (unsigned) z)
#define flockfile(x)
#define funlockfile(x)
#define sleep(x) Sleep((x) * 1000)
#define rmdir(x) _rmdir(x)

#if !defined(va_copy)
#define va_copy(x, y) x = y
#endif // !va_copy MINGW #defines va_copy

#if !defined(fileno)
#define fileno(x) _fileno(x)
#endif // !fileno MINGW #defines fileno

typedef HANDLE pthread_mutex_t;
typedef struct {HANDLE signal, broadcast;} pthread_cond_t;
typedef DWORD pthread_t;
#define pid_t HANDLE // MINGW typedefs pid_t to int. Using #define here.

static int pthread_mutex_lock(pthread_mutex_t *);
static int pthread_mutex_unlock(pthread_mutex_t *);
static void to_unicode(const char *path, wchar_t *wbuf, size_t wbuf_len);

#if defined(HAVE_STDINT)
#include <stdint.h>
#else
typedef unsigned int  uint32_t;
typedef unsigned short  uint16_t;
typedef unsigned __int64 uint64_t;
typedef __int64   int64_t;
#define INT64_MAX  9223372036854775807
#endif // HAVE_STDINT

// POSIX dirent interface
struct dirent {
  char d_name[PATH_MAX];
};

typedef struct DIR {
  HANDLE   handle;
  WIN32_FIND_DATAW info;
  struct dirent  result;
} DIR;

#ifndef HAVE_POLL
struct pollfd {
  SOCKET fd;
  short events;
  short revents;
};
#define POLLIN 1
#endif


// Mark required libraries
#ifdef _MSC_VER
#pragma comment(lib, "Ws2_32.lib")
#endif

#else    // UNIX  specific
#include <sys/wait.h>
#include <sys/socket.h>
#include <sys/poll.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/time.h>
#include <stdint.h>
#include <inttypes.h>
#include <netdb.h>

#include <pwd.h>
#include <unistd.h>
#include <dirent.h>
#if !defined(NO_SSL_DL) && !defined(NO_SSL)
#include <dlfcn.h>
#endif
#include <pthread.h>
#if defined(__MACH__)
#define SSL_LIB   "libssl.dylib"
#define CRYPTO_LIB  "libcrypto.dylib"
#else
#if !defined(SSL_LIB)
#define SSL_LIB   "libssl.so"
#endif
#if !defined(CRYPTO_LIB)
#define CRYPTO_LIB  "libcrypto.so"
#endif
#endif
#ifndef O_BINARY
#define O_BINARY  0
#endif // O_BINARY
#define closesocket(a) close(a)
#define mg_mkdir(x, y) mkdir(x, y)
#define mg_remove(x) remove(x)
#define mg_sleep(x) usleep((x) * 1000)
#define ERRNO errno
#define INVALID_SOCKET (-1)
#define INT64_FMT PRId64
typedef int SOCKET;
#define WINCDECL

#endif // End of Windows and UNIX specific includes

#include "mongoose.h"

#define MONGOOSE_VERSION "4.2"
#define PASSWORDS_FILE_NAME ".htpasswd"
#define CGI_ENVIRONMENT_SIZE 4096
#define MAX_CGI_ENVIR_VARS 64
#define MG_BUF_LEN 8192
#define MAX_REQUEST_SIZE 16384
#define ARRAY_SIZE(array) (sizeof(array) / sizeof(array[0]))

#ifdef DEBUG_TRACE
#undef DEBUG_TRACE
#define DEBUG_TRACE(x)
#else
#if defined(DEBUG)
#define DEBUG_TRACE(x) do { \
  flockfile(stdout); \
  printf("*** %lu.%p.%s.%d: ", \
         (unsigned long) time(NULL), (void *) pthread_self(), \
         __func__, __LINE__); \
  printf x; \
  putchar('\n'); \
  fflush(stdout); \
  funlockfile(stdout); \
} while (0)
#else
#define DEBUG_TRACE(x)
#endif // DEBUG
#endif // DEBUG_TRACE

// Darwin prior to 7.0 and Win32 do not have socklen_t
#ifdef NO_SOCKLEN_T
typedef int socklen_t;
#endif // NO_SOCKLEN_T
#define _DARWIN_UNLIMITED_SELECT

#define IP_ADDR_STR_LEN 50  // IPv6 hex string is 46 chars

#if !defined(MSG_NOSIGNAL)
#define MSG_NOSIGNAL 0
#endif

#if !defined(SOMAXCONN)
#define SOMAXCONN 100
#endif

#if !defined(PATH_MAX)
#define PATH_MAX 4096
#endif

// Size of the accepted socket queue
#if !defined(MGSQLEN)
#define MGSQLEN 20
#endif

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

static const char *http_500_error = "Internal Server Error";

#if defined(NO_SSL_DL)
#include <openssl/ssl.h>
#include <openssl/err.h>
#else
// SSL loaded dynamically from DLL.
// I put the prototypes here to be independent from OpenSSL source installation.
typedef struct ssl_st SSL;
typedef struct ssl_method_st SSL_METHOD;
typedef struct ssl_ctx_st SSL_CTX;

struct ssl_func {
  const char *name;   // SSL function name
  void  (*ptr)(void); // Function pointer
};

static struct ssl_func ssl_sw[];

#define SSL_free (* (void (*)(SSL *)) ssl_sw[0].ptr)
#define SSL_accept (* (int (*)(SSL *)) ssl_sw[1].ptr)
#define SSL_connect (* (int (*)(SSL *)) ssl_sw[2].ptr)
#define SSL_read (* (int (*)(SSL *, void *, int)) ssl_sw[3].ptr)
#define SSL_write (* (int (*)(SSL *, const void *,int)) ssl_sw[4].ptr)
#define SSL_get_error (* (int (*)(SSL *, int)) ssl_sw[5].ptr)
#define SSL_set_fd (* (int (*)(SSL *, SOCKET)) ssl_sw[6].ptr)
#define SSL_new (* (SSL * (*)(SSL_CTX *)) ssl_sw[7].ptr)
#define SSL_CTX_new (* (SSL_CTX * (*)(SSL_METHOD *)) ssl_sw[8].ptr)
#define SSLv23_server_method (* (SSL_METHOD * (*)(void)) ssl_sw[9].ptr)
#define SSL_library_init (* (int (*)(void)) ssl_sw[10].ptr)
#define SSL_CTX_use_PrivateKey_file (* (int (*)(SSL_CTX *, \
        const char *, int)) ssl_sw[11].ptr)
#define SSL_CTX_use_certificate_file (* (int (*)(SSL_CTX *, \
        const char *, int)) ssl_sw[12].ptr)
#define SSL_CTX_set_default_passwd_cb \
  (* (void (*)(SSL_CTX *, mg_event_handler_t)) ssl_sw[13].ptr)
#define SSL_CTX_free (* (void (*)(SSL_CTX *)) ssl_sw[14].ptr)
#define SSL_load_error_strings (* (void (*)(void)) ssl_sw[15].ptr)
#define SSL_CTX_use_certificate_chain_file \
  (* (int (*)(SSL_CTX *, const char *)) ssl_sw[16].ptr)
#define SSLv23_client_method (* (SSL_METHOD * (*)(void)) ssl_sw[17].ptr)
#define SSL_pending (* (int (*)(SSL *)) ssl_sw[18].ptr)
#define SSL_CTX_set_verify (* (void (*)(SSL_CTX *, int, int)) ssl_sw[19].ptr)
#define SSL_shutdown (* (int (*)(SSL *)) ssl_sw[20].ptr)

#define CRYPTO_num_locks (* (int (*)(void)) crypto_sw[0].ptr)
#define CRYPTO_set_locking_callback \
  (* (void (*)(void (*)(int, int, const char *, int))) crypto_sw[1].ptr)
#define CRYPTO_set_id_callback \
  (* (void (*)(unsigned long (*)(void))) crypto_sw[2].ptr)
#define ERR_get_error (* (unsigned long (*)(void)) crypto_sw[3].ptr)
#define ERR_error_string (* (char * (*)(unsigned long,char *)) crypto_sw[4].ptr)
#endif // NO_SSL_DL

// Unified socket address. For IPv6 support, add IPv6 address structure
// in the union u.
union usa {
  struct sockaddr sa;
  struct sockaddr_in sin;
#if defined(USE_IPV6)
  struct sockaddr_in6 sin6;
#endif
};

// Describes a string (chunk of memory).
struct vec {
  const char *ptr;
  size_t len;
};

struct file {
  int is_directory;
  time_t modification_time;
  int64_t size;
  // set to 1 if the content is gzipped
  // in which case we need a content-encoding: gzip header
  int gzipped;
};
#define STRUCT_FILE_INITIALIZER { 0, 0, 0, 0 }

// Describes listening socket, or socket which was accept()-ed by the master
// thread and queued for future handling by the worker thread.
struct socket {
  SOCKET sock;          // Listening socket
  union usa lsa;        // Local socket address
  union usa rsa;        // Remote socket address
  unsigned is_ssl:1;    // Is port SSL-ed
  unsigned ssl_redir:1; // Is port supposed to redirect everything to SSL port
};

// NOTE(lsm): this enum shoulds be in sync with the config_options.
enum {
  CGI_EXTENSIONS, CGI_ENVIRONMENT, PUT_DELETE_PASSWORDS_FILE, CGI_INTERPRETER,
  PROTECT_URI, AUTHENTICATION_DOMAIN, SSI_EXTENSIONS, THROTTLE,
  ACCESS_LOG_FILE, ENABLE_DIRECTORY_LISTING, ERROR_LOG_FILE,
  GLOBAL_PASSWORDS_FILE, INDEX_FILES, ENABLE_KEEP_ALIVE, ACCESS_CONTROL_LIST,
  EXTRA_MIME_TYPES, LISTENING_PORTS, DOCUMENT_ROOT, SSL_CERTIFICATE,
  NUM_THREADS, RUN_AS_USER, REWRITE, HIDE_FILES, REQUEST_TIMEOUT,
  NUM_OPTIONS
};

struct mg_context {
  volatile int stop_flag;         // Should we stop event loop
  SSL_CTX *ssl_ctx;               // SSL context
  char *config[NUM_OPTIONS];      // Mongoose configuration parameters
  mg_event_handler_t event_handler;  // User-defined callback function
  void *user_data;                // User-defined data

  struct socket *listening_sockets;
  int num_listening_sockets;

  volatile int num_threads;  // Number of threads
  pthread_mutex_t mutex;     // Protects (max|num)_threads
  pthread_cond_t  cond;      // Condvar for tracking workers terminations

  struct socket queue[MGSQLEN];   // Accepted sockets
  volatile int sq_head;      // Head of the socket queue
  volatile int sq_tail;      // Tail of the socket queue
  pthread_cond_t sq_full;    // Signaled when socket is produced
  pthread_cond_t sq_empty;   // Signaled when socket is consumed
};

struct mg_connection {
  struct mg_request_info request_info;
  struct mg_event event;
  struct mg_context *ctx;
  SSL *ssl;                   // SSL descriptor
  SSL_CTX *client_ssl_ctx;    // SSL context for client connections
  struct socket client;       // Connected client
  time_t birth_time;          // Time when request was received
  int64_t num_bytes_sent;     // Total bytes sent to client
  int64_t content_len;        // Content-Length header value
  int64_t num_bytes_read;     // Bytes read from a remote socket
  char *buf;                  // Buffer for received data
  char *path_info;            // PATH_INFO part of the URL
  int must_close;             // 1 if connection must be closed
  int buf_size;               // Buffer size
  int request_len;            // Size of the request + headers in a buffer
  int data_len;               // Total size of data in a buffer
  int status_code;            // HTTP reply status code, e.g. 200
  int throttle;               // Throttling, bytes/sec. <= 0 means no throttle
  time_t last_throttle_time;  // Last time throttled data was sent
  int64_t last_throttle_bytes;// Bytes sent this second
};

// Directory entry
struct de {
  struct mg_connection *conn;
  char *file_name;
  struct file file;
};


static void mg_strlcpy(register char *dst, register const char *src, size_t n) {
  for (; *src != '\0' && n > 1; n--) {
    *dst++ = *src++;
  }
  *dst = '\0';
}

static int lowercase(const char *s) {
  return tolower(* (const unsigned char *) s);
}

static int mg_strncasecmp(const char *s1, const char *s2, size_t len) {
  int diff = 0;

  if (len > 0)
    do {
      diff = lowercase(s1++) - lowercase(s2++);
    } while (diff == 0 && s1[-1] != '\0' && --len > 0);

  return diff;
}

static int mg_strcasecmp(const char *s1, const char *s2) {
  int diff;

  do {
    diff = lowercase(s1++) - lowercase(s2++);
  } while (diff == 0 && s1[-1] != '\0');

  return diff;
}

static char * mg_strndup(const char *ptr, size_t len) {
  char *p;

  if ((p = (char *) malloc(len + 1)) != NULL) {
    mg_strlcpy(p, ptr, len + 1);
  }

  return p;
}

static char * mg_strdup(const char *str) {
  return mg_strndup(str, strlen(str));
}

static const char *mg_strcasestr(const char *big_str, const char *small_str) {
  int i, big_len = strlen(big_str), small_len = strlen(small_str);

  for (i = 0; i <= big_len - small_len; i++) {
    if (mg_strncasecmp(big_str + i, small_str, small_len) == 0) {
      return big_str + i;
    }
  }

  return NULL;
}

// Like snprintf(), but never returns negative value, or a value
// that is larger than a supplied buffer.
// Thanks to Adam Zeldis to pointing snprintf()-caused vulnerability
// in his audit report.
static int mg_vsnprintf(char *buf, size_t buflen, const char *fmt, va_list ap) {
  int n;

  if (buflen == 0) {
    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,
    PRINTF_FORMAT_STRING(const char *fmt), ...) PRINTF_ARGS(3, 4);

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;
}

// Skip the characters until one of the delimiters characters found.
// 0-terminate resulting word. Skip the delimiter and following whitespaces.
// Advance pointer to buffer to the next word. Return found 0-terminated word.
// Delimiters can be quoted with quotechar.
static char *skip_quoted(char **buf, const char *delimiters,
                         const char *whitespace, char quotechar) {
  char *p, *begin_word, *end_word, *end_whitespace;

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

  // Check for quotechar
  if (end_word > begin_word) {
    p = end_word - 1;
    while (*p == quotechar) {
      // If there is anything beyond end_word, copy it
      if (*end_word == '\0') {
        *p = '\0';
        break;
      } else {
        size_t end_off = strcspn(end_word + 1, delimiters);
        memmove (p, end_word, end_off + 1);
        p += end_off; // p must correspond to end_word - 1
        end_word += end_off + 1;
      }
    }
    for (p++; p < end_word; p++) {
      *p = '\0';
    }
  }

  if (*end_word == '\0') {
    *buf = end_word;
  } else {
    end_whitespace = end_word + 1 + strspn(end_word + 1, whitespace);

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

    *buf = end_whitespace;
  }

  return begin_word;
}

// Simplified version of skip_quoted without quote char
// and whitespace == delimiters
static char *skip(char **buf, const char *delimiters) {
  return skip_quoted(buf, delimiters, delimiters, 0);
}


// Return HTTP header value, or NULL if not found.
static const char *get_header(const struct mg_request_info *ri,
                              const char *name) {
  int i;

  for (i = 0; i < ri->num_headers; i++)
    if (!mg_strcasecmp(name, ri->http_headers[i].name))
      return ri->http_headers[i].value;

  return NULL;
}

const char *mg_get_header(const struct mg_connection *conn, const char *name) {
  return get_header(&conn->request_info, name);
}

// 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;
}

// Perform case-insensitive match of string against pattern
static int match_prefix(const char *pattern, int pattern_len, const char *str) {
  const char *or_str;
  int i, j, len, res;

  if ((or_str = (const char *) memchr(pattern, '|', pattern_len)) != NULL) {
    res = match_prefix(pattern, or_str - pattern, str);
    return res > 0 ? res :
        match_prefix(or_str + 1, (pattern + pattern_len) - (or_str + 1), str);
  }

  i = j = 0;
  res = -1;
  for (; i < pattern_len; i++, j++) {
    if (pattern[i] == '?' && str[j] != '\0') {
      continue;
    } else if (pattern[i] == '$') {
      return str[j] == '\0' ? j : -1;
    } else if (pattern[i] == '*') {
      i++;
      if (pattern[i] == '*') {
        i++;
        len = (int) strlen(str + j);
      } else {
        len = (int) strcspn(str + j, "/");
      }
      if (i == pattern_len) {
        return j + len;
      }
      do {
        res = match_prefix(pattern + i, pattern_len - i, str + j + len);
      } while (res == -1 && len-- > 0);
      return res == -1 ? -1 : j + res + len;
    } else if (lowercase(&pattern[i]) != lowercase(&str[j])) {
      return -1;
    }
  }
  return j;
}


static const char *month_names[] = {
  "Jan", "Feb", "Mar", "Apr", "May", "Jun",
  "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
};

static const char *config_options[] = {
  "cgi_pattern", "**.cgi$|**.pl$|**.php$",
  "cgi_environment", NULL,
  "put_delete_auth_file", NULL,
  "cgi_interpreter", NULL,
  "protect_uri", NULL,
  "authentication_domain", "mydomain.com",
  "ssi_pattern", "**.shtml$|**.shtm$",
  "throttle", NULL,
  "access_log_file", NULL,
  "enable_directory_listing", "yes",
  "error_log_file", NULL,
  "global_auth_file", NULL,
  "index_files",
    "index.html,index.htm,index.cgi,index.shtml,index.php,index.lp",
  "enable_keep_alive", "no",
  "access_control_list", NULL,
  "extra_mime_types", NULL,
  "listening_ports", "8080",
  "document_root",  NULL,
  "ssl_certificate", NULL,
  "num_threads", "50",
  "run_as_user", NULL,
  "url_rewrite_patterns", NULL,
  "hide_files_patterns", NULL,
  "request_timeout_ms", "30000",
  NULL
};

// Return number of bytes left to read for this connection
static int64_t left_to_read(const struct mg_connection *conn) {
  return conn->content_len + conn->request_len - conn->num_bytes_read;
}

const char **mg_get_valid_option_names(void) {
  return config_options;
}

static int call_user(int type, struct mg_connection *conn, void *p) {
  if (conn != NULL && conn->ctx != NULL) {
    conn->event.user_data = conn->ctx->user_data;
    conn->event.type = type;
    conn->event.event_param = p;
    conn->event.request_info = &conn->request_info;
    conn->event.conn = conn;
  }
  return conn == NULL || conn->ctx == NULL || conn->ctx->event_handler == NULL ?
    0 : conn->ctx->event_handler(&conn->event);
}

static FILE *mg_fopen(const char *path, const char *mode) {
#ifdef _WIN32
  wchar_t wbuf[PATH_MAX], wmode[20];
  to_unicode(path, wbuf, ARRAY_SIZE(wbuf));
  MultiByteToWideChar(CP_UTF8, 0, mode, -1, wmode, ARRAY_SIZE(wmode));
  return _wfopen(wbuf, wmode);
#else
  return fopen(path, mode);
#endif
}

static int get_option_index(const char *name) {
  int i;

  for (i = 0; config_options[i * 2] != NULL; i++) {
    if (strcmp(config_options[i * 2], name) == 0) {
      return i;
    }
  }
  return -1;
}

const char *mg_get_option(const struct mg_context *ctx, const char *name) {
  int i;
  if ((i = get_option_index(name)) == -1) {
    return NULL;
  } else if (ctx->config[i] == NULL) {
    return "";
  } else {
    return ctx->config[i];
  }
}

static void sockaddr_to_string(char *buf, size_t len,
                                     const union usa *usa) {
  buf[0] = '\0';
#if defined(USE_IPV6)
  inet_ntop(usa->sa.sa_family, usa->sa.sa_family == AF_INET ?
            (void *) &usa->sin.sin_addr :
            (void *) &usa->sin6.sin6_addr, buf, len);
#elif defined(_WIN32)
  // Only Windoze Vista (and newer) have inet_ntop()
  strncpy(buf, inet_ntoa(usa->sin.sin_addr), len);
#else
  inet_ntop(usa->sa.sa_family, (void *) &usa->sin.sin_addr, buf, len);
#endif
}

static void cry(struct mg_connection *conn,
                PRINTF_FORMAT_STRING(const char *fmt), ...) PRINTF_ARGS(2, 3);

// Print error message to the opened error log stream.
static void cry(struct mg_connection *conn, const char *fmt, ...) {
  char buf[MG_BUF_LEN], src_addr[IP_ADDR_STR_LEN];
  va_list ap;
  FILE *fp;
  time_t timestamp;

  va_start(ap, fmt);
  (void) vsnprintf(buf, sizeof(buf), fmt, ap);
  va_end(ap);

  // Do not lock when getting the callback value, here and below.
  // I suppose this is fine, since function cannot disappear in the
  // same way string option can.
  if (call_user(MG_EVENT_LOG, conn, buf) == 0) {
    fp = conn->ctx == NULL || conn->ctx->config[ERROR_LOG_FILE] == NULL ? NULL :
      fopen(conn->ctx->config[ERROR_LOG_FILE], "a+");

    if (fp != NULL) {
      flockfile(fp);
      timestamp = time(NULL);

      sockaddr_to_string(src_addr, sizeof(src_addr), &conn->client.rsa);
      fprintf(fp, "[%010lu] [error] [client %s] ", (unsigned long) timestamp,
              src_addr);

      if (conn->request_info.request_method != NULL) {
        fprintf(fp, "%s %s: ", conn->request_info.request_method,
                conn->request_info.uri);
      }

      fprintf(fp, "%s", buf);
      fputc('\n', fp);
      funlockfile(fp);
      fclose(fp);
    }
  }
}

// Return fake connection structure. Used for logging, if connection
// is not applicable at the moment of logging.
static struct mg_connection *fc(struct mg_context *ctx) {
  static struct mg_connection fake_connection;
  fake_connection.ctx = ctx;
  // See https://github.com/cesanta/mongoose/issues/236
  fake_connection.event.user_data = ctx->user_data;
  return &fake_connection;
}

const char *mg_version(void) {
  return MONGOOSE_VERSION;
}

// HTTP 1.1 assumes keep alive if "Connection:" header is not set
// This function must tolerate situations when connection info is not
// set up, for example if request parsing failed.
static int should_keep_alive(const struct mg_connection *conn) {
  const char *http_version = conn->request_info.http_version;
  const char *header = mg_get_header(conn, "Connection");
  if (conn->must_close ||
      conn->status_code == 401 ||
      mg_strcasecmp(conn->ctx->config[ENABLE_KEEP_ALIVE], "yes") != 0 ||
      (header != NULL && mg_strcasecmp(header, "keep-alive") != 0) ||
      (header == NULL && http_version && strcmp(http_version, "1.1"))) {
    return 0;
  }
  return 1;
}

static const char *suggest_connection_header(const struct mg_connection *conn) {
  return should_keep_alive(conn) ? "keep-alive" : "close";
}

static void send_http_error(struct mg_connection *, int, const char *,
                            PRINTF_FORMAT_STRING(const char *fmt), ...)
  PRINTF_ARGS(4, 5);


static void send_http_error(struct mg_connection *conn, int status,
                            const char *reason, const char *fmt, ...) {
  char buf[MG_BUF_LEN];
  va_list ap;
  int len = 0;

  conn->status_code = status;
  buf[0] = '\0';

  // Errors 1xx, 204 and 304 MUST NOT send a body
  if (status > 199 && status != 204 && status != 304) {
    len = mg_snprintf(buf, sizeof(buf), "Error %d: %s", status, reason);
    buf[len++] = '\n';

    va_start(ap, fmt);
    len += mg_vsnprintf(buf + len, sizeof(buf) - len, fmt, ap);
    va_end(ap);
  }
  DEBUG_TRACE(("[%s]", buf));

  mg_printf(conn, "HTTP/1.1 %d %s\r\n"
            "Content-Length: %d\r\n"
            "Connection: %s\r\n\r\n", status, reason, len,
            suggest_connection_header(conn));
  conn->num_bytes_sent += mg_printf(conn, "%s", buf);
}

#if defined(_WIN32) && !defined(__SYMBIAN32__)
static pthread_t pthread_self(void) {
  return GetCurrentThreadId();
}

static int pthread_mutex_init(pthread_mutex_t *mutex, void *unused) {
  (void) unused;
  *mutex = CreateMutex(NULL, FALSE, NULL);
  return *mutex == NULL ? -1 : 0;
}

static int pthread_mutex_destroy(pthread_mutex_t *mutex) {
  return CloseHandle(*mutex) == 0 ? -1 : 0;
}

static int pthread_mutex_lock(pthread_mutex_t *mutex) {
  return WaitForSingleObject(*mutex, INFINITE) == WAIT_OBJECT_0? 0 : -1;
}

static int pthread_mutex_unlock(pthread_mutex_t *mutex) {
  return ReleaseMutex(*mutex) == 0 ? -1 : 0;
}

static int pthread_cond_init(pthread_cond_t *cv, const void *unused) {
  (void) unused;
  cv->signal = CreateEvent(NULL, FALSE, FALSE, NULL);
  cv->broadcast = CreateEvent(NULL, TRUE, FALSE, NULL);
  return cv->signal != NULL && cv->broadcast != NULL ? 0 : -1;
}

static int pthread_cond_wait(pthread_cond_t *cv, pthread_mutex_t *mutex) {
  HANDLE handles[] = {cv->signal, cv->broadcast};
  ReleaseMutex(*mutex);
  WaitForMultipleObjects(2, handles, FALSE, INFINITE);
  return WaitForSingleObject(*mutex, INFINITE) == WAIT_OBJECT_0? 0 : -1;
}

static int pthread_cond_signal(pthread_cond_t *cv) {
  return SetEvent(cv->signal) == 0 ? -1 : 0;
}

static int pthread_cond_broadcast(pthread_cond_t *cv) {
  // Implementation with PulseEvent() has race condition, see
  // http://www.cs.wustl.edu/~schmidt/win32-cv-1.html
  return PulseEvent(cv->broadcast) == 0 ? -1 : 0;
}

static int pthread_cond_destroy(pthread_cond_t *cv) {
  return CloseHandle(cv->signal) && CloseHandle(cv->broadcast) ? 0 : -1;
}

// For Windows, change all slashes to backslashes in path names.
static void change_slashes_to_backslashes(char *path) {
  int i;

  for (i = 0; path[i] != '\0'; i++) {
    if (path[i] == '/')
      path[i] = '\\';
    // i > 0 check is to preserve UNC paths, like \\server\file.txt
    if (path[i] == '\\' && i > 0)
      while (path[i + 1] == '\\' || path[i + 1] == '/')
        (void) memmove(path + i + 1,
            path + i + 2, strlen(path + i + 1));
  }
}

// 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_unicode(const char *path, wchar_t *wbuf, size_t wbuf_len) {
  char buf[PATH_MAX * 2], buf2[PATH_MAX * 2];

  mg_strlcpy(buf, path, sizeof(buf));
  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';
  }
}