mongoose.c

                  "Content-Length: %" INT64_FMT "\r\n"
                  "Connection: %s\r\n"
                  "Accept-Ranges: bytes\r\n"
                  "%s%s\r\n",
                  conn->mg_conn.status_code, msg, date, lm, etag,
                  (int) mime_vec.len, mime_vec.ptr, conn->cl,
                  suggest_connection_header(&conn->mg_conn),
                  range, MONGOOSE_USE_EXTRA_HTTP_HEADERS);
  ns_send(conn->ns_conn, headers, n);

  if (!strcmp(conn->mg_conn.request_method, "HEAD")) {
    conn->ns_conn->flags |= NSF_FINISHED_SENDING_DATA;
    close(conn->endpoint.fd);
    conn->endpoint_type = EP_NONE;
  }
}
#endif  // MONGOOSE_NO_FILESYSTEM

static void call_request_handler_if_data_is_buffered(struct connection *conn) {
  struct iobuf *loc = &conn->ns_conn->recv_iobuf;
  struct mg_connection *c = &conn->mg_conn;

#ifndef MONGOOSE_NO_WEBSOCKET
  if (conn->mg_conn.is_websocket) {
    do { } while (deliver_websocket_frame(conn));
  } else
#endif
  if ((size_t) loc->len >= c->content_len &&
      call_request_handler(conn) == MG_FALSE) {
    open_local_endpoint(conn, 1);
  }
}

#if !defined(MONGOOSE_NO_DIRECTORY_LISTING) || !defined(MONGOOSE_NO_DAV)

#ifdef _WIN32
struct dirent {
  char d_name[MAX_PATH_SIZE];
};

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

// Implementation of POSIX opendir/closedir/readdir for Windows.
static DIR *opendir(const char *name) {
  DIR *dir = NULL;
  wchar_t wpath[MAX_PATH_SIZE];
  DWORD attrs;

  if (name == NULL) {
    SetLastError(ERROR_BAD_ARGUMENTS);
  } else if ((dir = (DIR *) malloc(sizeof(*dir))) == NULL) {
    SetLastError(ERROR_NOT_ENOUGH_MEMORY);
  } else {
    to_wchar(name, wpath, ARRAY_SIZE(wpath));
    attrs = GetFileAttributesW(wpath);
    if (attrs != 0xFFFFFFFF &&
        ((attrs & FILE_ATTRIBUTE_DIRECTORY) == FILE_ATTRIBUTE_DIRECTORY)) {
      (void) wcscat(wpath, L"\\*");
      dir->handle = FindFirstFileW(wpath, &dir->info);
      dir->result.d_name[0] = '\0';
    } else {
      free(dir);
      dir = NULL;
    }
  }

  return dir;
}

static int closedir(DIR *dir) {
  int result = 0;

  if (dir != NULL) {
    if (dir->handle != INVALID_HANDLE_VALUE)
      result = FindClose(dir->handle) ? 0 : -1;

    free(dir);
  } else {
    result = -1;
    SetLastError(ERROR_BAD_ARGUMENTS);
  }

  return result;
}

static struct dirent *readdir(DIR *dir) {
  struct dirent *result = 0;

  if (dir) {
    if (dir->handle != INVALID_HANDLE_VALUE) {
      result = &dir->result;
      (void) WideCharToMultiByte(CP_UTF8, 0,
          dir->info.cFileName, -1, result->d_name,
          sizeof(result->d_name), NULL, NULL);

      if (!FindNextFileW(dir->handle, &dir->info)) {
        (void) FindClose(dir->handle);
        dir->handle = INVALID_HANDLE_VALUE;
      }

    } else {
      SetLastError(ERROR_FILE_NOT_FOUND);
    }
  } else {
    SetLastError(ERROR_BAD_ARGUMENTS);
  }

  return result;
}
#endif // _WIN32  POSIX opendir/closedir/readdir implementation

static int scan_directory(struct connection *conn, const char *dir,
                          struct dir_entry **arr) {
  char path[MAX_PATH_SIZE];
  struct dir_entry *p;
  struct dirent *dp;
  int arr_size = 0, arr_ind = 0, inc = 100;
  DIR *dirp;

  *arr = NULL;
  if ((dirp = (opendir(dir))) == NULL) return 0;

  while ((dp = readdir(dirp)) != NULL) {
    // Do not show current dir and hidden files
    if (!strcmp(dp->d_name, ".") ||
        !strcmp(dp->d_name, "..") ||
        must_hide_file(conn, dp->d_name)) {
      continue;
    }
    mg_snprintf(path, sizeof(path), "%s%c%s", dir, '/', dp->d_name);

    // Resize the array if nesessary
    if (arr_ind >= arr_size) {
      if ((p = (struct dir_entry *)
           realloc(*arr, (inc + arr_size) * sizeof(**arr))) != NULL) {
        // Memset new chunk to zero, otherwize st_mtime will have garbage which
        // can make strftime() segfault, see
        // http://code.google.com/p/mongoose/issues/detail?id=79
        memset(p + arr_size, 0, sizeof(**arr) * inc);

        *arr = p;
        arr_size += inc;
      }
    }

    if (arr_ind < arr_size) {
      (*arr)[arr_ind].conn = conn;
      (*arr)[arr_ind].file_name = strdup(dp->d_name);
      stat(path, &(*arr)[arr_ind].st);
      arr_ind++;
    }
  }
  closedir(dirp);

  return arr_ind;
}

int mg_url_encode(const char *src, size_t s_len, char *dst, size_t dst_len) {
  static const char *dont_escape = "._-$,;~()";
  static const char *hex = "0123456789abcdef";
  size_t i = 0, j = 0;

  for (i = j = 0; dst_len > 0 && i < s_len && j < dst_len - 1; i++, j++) {
    if (isalnum(* (const unsigned char *) (src + i)) ||
        strchr(dont_escape, * (const unsigned char *) (src + i)) != NULL) {
      dst[j] = src[i];
    } else if (j + 3 < dst_len) {
      dst[j] = '%';
      dst[j + 1] = hex[(* (const unsigned char *) (src + i)) >> 4];
      dst[j + 2] = hex[(* (const unsigned char *) (src + i)) & 0xf];
      j += 2;
    }
  }

  dst[j] = '\0';
  return j;
}
#endif  // !NO_DIRECTORY_LISTING || !MONGOOSE_NO_DAV

#ifndef MONGOOSE_NO_DIRECTORY_LISTING

static void print_dir_entry(const struct dir_entry *de) {
  char size[64], mod[64], href[MAX_PATH_SIZE * 3];
  int64_t fsize = de->st.st_size;
  int is_dir = S_ISDIR(de->st.st_mode);
  const char *slash = is_dir ? "/" : "";

  if (is_dir) {
    mg_snprintf(size, sizeof(size), "%s", "[DIRECTORY]");
  } else {
     // We use (signed) cast below because MSVC 6 compiler cannot
     // convert unsigned __int64 to double.
    if (fsize < 1024) {
      mg_snprintf(size, sizeof(size), "%d", (int) fsize);
    } else if (fsize < 0x100000) {
      mg_snprintf(size, sizeof(size), "%.1fk", (double) fsize / 1024.0);
    } else if (fsize < 0x40000000) {
      mg_snprintf(size, sizeof(size), "%.1fM", (double) fsize / 1048576);
    } else {
      mg_snprintf(size, sizeof(size), "%.1fG", (double) fsize / 1073741824);
    }
  }
  strftime(mod, sizeof(mod), "%d-%b-%Y %H:%M", localtime(&de->st.st_mtime));
  mg_url_encode(de->file_name, strlen(de->file_name), href, sizeof(href));
  mg_printf_data(&de->conn->mg_conn,
                  "<tr><td><a href=\"%s%s\">%s%s</a></td>"
                  "<td>&nbsp;%s</td><td>&nbsp;&nbsp;%s</td></tr>\n",
                  href, slash, de->file_name, slash, mod, size);
}

// Sort directory entries by size, or name, or modification time.
// On windows, __cdecl specification is needed in case if project is built
// with __stdcall convention. qsort always requires __cdels callback.
static int __cdecl compare_dir_entries(const void *p1, const void *p2) {
  const struct dir_entry *a = (const struct dir_entry *) p1,
        *b = (const struct dir_entry *) p2;
  const char *qs = a->conn->mg_conn.query_string ?
    a->conn->mg_conn.query_string : "na";
  int cmp_result = 0;

  if (S_ISDIR(a->st.st_mode) && !S_ISDIR(b->st.st_mode)) {
    return -1;  // Always put directories on top
  } else if (!S_ISDIR(a->st.st_mode) && S_ISDIR(b->st.st_mode)) {
    return 1;   // Always put directories on top
  } else if (*qs == 'n') {
    cmp_result = strcmp(a->file_name, b->file_name);
  } else if (*qs == 's') {
    cmp_result = a->st.st_size == b->st.st_size ? 0 :
      a->st.st_size > b->st.st_size ? 1 : -1;
  } else if (*qs == 'd') {
    cmp_result = a->st.st_mtime == b->st.st_mtime ? 0 :
      a->st.st_mtime > b->st.st_mtime ? 1 : -1;
  }

  return qs[1] == 'd' ? -cmp_result : cmp_result;
}

static void send_directory_listing(struct connection *conn, const char *dir) {
  struct dir_entry *arr = NULL;
  int i, num_entries, sort_direction = conn->mg_conn.query_string != NULL &&
    conn->mg_conn.query_string[1] == 'd' ? 'a' : 'd';

  mg_send_header(&conn->mg_conn, "Transfer-Encoding", "chunked");
  mg_send_header(&conn->mg_conn, "Content-Type", "text/html; charset=utf-8");

  mg_printf_data(&conn->mg_conn,
              "<html><head><title>Index of %s</title>"
              "<style>th {text-align: left;}</style></head>"
              "<body><h1>Index of %s</h1><pre><table cellpadding=\"0\">"
              "<tr><th><a href=\"?n%c\">Name</a></th>"
              "<th><a href=\"?d%c\">Modified</a></th>"
              "<th><a href=\"?s%c\">Size</a></th></tr>"
              "<tr><td colspan=\"3\"><hr></td></tr>",
              conn->mg_conn.uri, conn->mg_conn.uri,
              sort_direction, sort_direction, sort_direction);

  num_entries = scan_directory(conn, dir, &arr);
  qsort(arr, num_entries, sizeof(arr[0]), compare_dir_entries);
  for (i = 0; i < num_entries; i++) {
    print_dir_entry(&arr[i]);
    free(arr[i].file_name);
  }
  free(arr);

  write_terminating_chunk(conn);
  close_local_endpoint(conn);
}
#endif  // MONGOOSE_NO_DIRECTORY_LISTING

#ifndef MONGOOSE_NO_DAV
static void print_props(struct connection *conn, const char *uri,
                        file_stat_t *stp) {
  char mtime[64];

  gmt_time_string(mtime, sizeof(mtime), &stp->st_mtime);
  mg_printf(&conn->mg_conn,
      "<d:response>"
       "<d:href>%s</d:href>"
       "<d:propstat>"
        "<d:prop>"
         "<d:resourcetype>%s</d:resourcetype>"
         "<d:getcontentlength>%" INT64_FMT "</d:getcontentlength>"
         "<d:getlastmodified>%s</d:getlastmodified>"
        "</d:prop>"
        "<d:status>HTTP/1.1 200 OK</d:status>"
       "</d:propstat>"
      "</d:response>\n",
      uri, S_ISDIR(stp->st_mode) ? "<d:collection/>" : "",
      (int64_t) stp->st_size, mtime);
}

static void handle_propfind(struct connection *conn, const char *path,
                            file_stat_t *stp, int exists) {
  static const char header[] = "HTTP/1.1 207 Multi-Status\r\n"
    "Connection: close\r\n"
    "Content-Type: text/xml; charset=utf-8\r\n\r\n"
    "<?xml version=\"1.0\" encoding=\"utf-8\"?>"
    "<d:multistatus xmlns:d='DAV:'>\n";
  static const char footer[] = "</d:multistatus>";
  const char *depth = mg_get_header(&conn->mg_conn, "Depth"),
        *list_dir = conn->server->config_options[ENABLE_DIRECTORY_LISTING];

  conn->mg_conn.status_code = 207;

  // Print properties for the requested resource itself
  if (!exists) {
    conn->mg_conn.status_code = 404;
    mg_printf(&conn->mg_conn, "%s", "HTTP/1.1 404 Not Found\r\n\r\n");
  } else if (S_ISDIR(stp->st_mode) && mg_strcasecmp(list_dir, "yes") != 0) {
    conn->mg_conn.status_code = 403;
    mg_printf(&conn->mg_conn, "%s",
              "HTTP/1.1 403 Directory Listing Denied\r\n\r\n");
  } else {
    ns_send(conn->ns_conn, header, sizeof(header) - 1);
    print_props(conn, conn->mg_conn.uri, stp);

    if (S_ISDIR(stp->st_mode) &&
             (depth == NULL || strcmp(depth, "0") != 0)) {
      struct dir_entry *arr = NULL;
      int i, num_entries = scan_directory(conn, path, &arr);

      for (i = 0; i < num_entries; i++) {
        char buf[MAX_PATH_SIZE * 3];
        struct dir_entry *de = &arr[i];
        mg_url_encode(de->file_name, strlen(de->file_name), buf, sizeof(buf));
        print_props(conn, buf, &de->st);
      }
    }
    ns_send(conn->ns_conn, footer, sizeof(footer) - 1);
  }

  close_local_endpoint(conn);
}

static void handle_mkcol(struct connection *conn, const char *path) {
  int status_code = 500;

  if (conn->mg_conn.content_len > 0) {
    status_code = 415;
  } else if (!mkdir(path, 0755)) {
    status_code = 201;
  } else if (errno == EEXIST) {
    status_code = 405;
  } else if (errno == EACCES) {
    status_code = 403;
  } else if (errno == ENOENT) {
    status_code = 409;
  }
  send_http_error(conn, status_code, NULL);
}

static int remove_directory(const char *dir) {
  char path[MAX_PATH_SIZE];
  struct dirent *dp;
  file_stat_t st;
  DIR *dirp;

  if ((dirp = opendir(dir)) == NULL) return 0;

  while ((dp = readdir(dirp)) != NULL) {
    if (!strcmp(dp->d_name, ".") || !strcmp(dp->d_name, "..")) continue;
    mg_snprintf(path, sizeof(path), "%s%c%s", dir, '/', dp->d_name);
    stat(path, &st);
    if (S_ISDIR(st.st_mode)) {
      remove_directory(path);
    } else {
      remove(path);
    }
  }
  closedir(dirp);
  rmdir(dir);

  return 1;
}

static void handle_delete(struct connection *conn, const char *path) {
  file_stat_t st;

  if (stat(path, &st) != 0) {
    send_http_error(conn, 404, NULL);
  } else if (S_ISDIR(st.st_mode)) {
    remove_directory(path);
    send_http_error(conn, 204, NULL);
  } else if (remove(path) == 0) {
    send_http_error(conn, 204, NULL);
  } else {
    send_http_error(conn, 423, NULL);
  }
}

// For a given PUT path, create all intermediate subdirectories
// for given path. Return 0 if the path itself is a directory,
// or -1 on error, 1 if OK.
static int put_dir(const char *path) {
  char buf[MAX_PATH_SIZE];
  const char *s, *p;
  file_stat_t st;

  // Create intermediate directories if they do not exist
  for (s = p = path + 1; (p = strchr(s, '/')) != NULL; s = ++p) {
    if (p - path >= (int) sizeof(buf)) return -1; // Buffer overflow
    memcpy(buf, path, p - path);
    buf[p - path] = '\0';
    if (stat(buf, &st) != 0 && mkdir(buf, 0755) != 0) return -1;
    if (p[1] == '\0') return 0;  // Path is a directory itself
  }

  return 1;
}

static void handle_put(struct connection *conn, const char *path) {
  file_stat_t st;
  const char *range, *cl_hdr = mg_get_header(&conn->mg_conn, "Content-Length");
  int64_t r1, r2;
  int rc;

  conn->mg_conn.status_code = !stat(path, &st) ? 200 : 201;
  if ((rc = put_dir(path)) == 0) {
    mg_printf(&conn->mg_conn, "HTTP/1.1 %d OK\r\n\r\n",
              conn->mg_conn.status_code);
    close_local_endpoint(conn);
  } else if (rc == -1) {
    send_http_error(conn, 500, "put_dir: %s", strerror(errno));
  } else if (cl_hdr == NULL) {
    send_http_error(conn, 411, NULL);
#ifdef _WIN32
    //On Windows, open() is a macro with 2 params
  } else if ((conn->endpoint.fd =
              open(path, O_RDWR | O_CREAT | O_TRUNC)) < 0) {
#else
  } else if ((conn->endpoint.fd =
              open(path, O_RDWR | O_CREAT | O_TRUNC, 0644)) < 0) {
#endif
    send_http_error(conn, 500, "open(%s): %s", path, strerror(errno));
  } else {
    DBG(("PUT [%s] %zu", path, conn->ns_conn->recv_iobuf.len));
    conn->endpoint_type = EP_PUT;
    ns_set_close_on_exec(conn->endpoint.fd);
    range = mg_get_header(&conn->mg_conn, "Content-Range");
    conn->cl = to64(cl_hdr);
    r1 = r2 = 0;
    if (range != NULL && parse_range_header(range, &r1, &r2) > 0) {
      conn->mg_conn.status_code = 206;
      lseek(conn->endpoint.fd, r1, SEEK_SET);
      conn->cl = r2 > r1 ? r2 - r1 + 1: conn->cl - r1;
    }
    mg_printf(&conn->mg_conn, "HTTP/1.1 %d OK\r\nContent-Length: 0\r\n\r\n",
              conn->mg_conn.status_code);
  }
}

static void forward_put_data(struct connection *conn) {
  struct iobuf *io = &conn->ns_conn->recv_iobuf;
  size_t k = conn->cl < (int64_t) io->len ? conn->cl : io->len;   // To write
  int n = write(conn->endpoint.fd, io->buf, k);   // Write them!
  if (n > 0) {
    iobuf_remove(io, n);
    conn->cl -= n;
  }
  if (conn->cl <= 0) {
    close_local_endpoint(conn);
  }
}
#endif //  MONGOOSE_NO_DAV

static void send_options(struct connection *conn) {
  conn->mg_conn.status_code = 200;
  mg_printf(&conn->mg_conn, "%s",
            "HTTP/1.1 200 OK\r\nAllow: GET, POST, HEAD, CONNECT, PUT, "
            "DELETE, OPTIONS, PROPFIND, MKCOL\r\nDAV: 1\r\n\r\n");
  close_local_endpoint(conn);
}

#ifndef MONGOOSE_NO_AUTH
void mg_send_digest_auth_request(struct mg_connection *c) {
  struct connection *conn = MG_CONN_2_CONN(c);
  c->status_code = 401;
  mg_printf(c,
            "HTTP/1.1 401 Unauthorized\r\n"
            "WWW-Authenticate: Digest qop=\"auth\", "
            "realm=\"%s\", nonce=\"%lu\"\r\n\r\n",
            conn->server->config_options[AUTH_DOMAIN],
            (unsigned long) time(NULL));
  close_local_endpoint(conn);
}

// Use the global passwords file, if specified by auth_gpass option,
// or search for .htpasswd in the requested directory.
static FILE *open_auth_file(struct connection *conn, const char *path) {
  char name[MAX_PATH_SIZE];
  const char *p, *gpass = conn->server->config_options[GLOBAL_AUTH_FILE];
  file_stat_t st;
  FILE *fp = NULL;

  if (gpass != NULL) {
    // Use global passwords file
    fp = fopen(gpass, "r");
  } else if (!stat(path, &st) && S_ISDIR(st.st_mode)) {
    mg_snprintf(name, sizeof(name), "%s%c%s", path, '/', PASSWORDS_FILE_NAME);
    fp = fopen(name, "r");
  } else {
    // Try to find .htpasswd in requested directory.
    if ((p = strrchr(path, '/')) == NULL) p = path;
    mg_snprintf(name, sizeof(name), "%.*s%c%s",
                (int) (p - path), path, '/', PASSWORDS_FILE_NAME);
    fp = fopen(name, "r");
  }

  return fp;
}

#if !defined(HAVE_MD5) && !defined(MONGOOSE_NO_AUTH)
typedef struct MD5Context {
  uint32_t buf[4];
  uint32_t bits[2];
  unsigned char in[64];
} MD5_CTX;

static void byteReverse(unsigned char *buf, unsigned longs) {
  uint32_t t;

  // Forrest: MD5 expect LITTLE_ENDIAN, swap if BIG_ENDIAN
  if (is_big_endian()) {
    do {
      t = (uint32_t) ((unsigned) buf[3] << 8 | buf[2]) << 16 |
        ((unsigned) buf[1] << 8 | buf[0]);
      * (uint32_t *) buf = t;
      buf += 4;
    } while (--longs);
  }
}

#define F1(x, y, z) (z ^ (x & (y ^ z)))
#define F2(x, y, z) F1(z, x, y)
#define F3(x, y, z) (x ^ y ^ z)
#define F4(x, y, z) (y ^ (x | ~z))

#define MD5STEP(f, w, x, y, z, data, s) \
  ( w += f(x, y, z) + data,  w = w<<s | w>>(32-s),  w += x )

// Start MD5 accumulation.  Set bit count to 0 and buffer to mysterious
// initialization constants.
static void MD5Init(MD5_CTX *ctx) {
  ctx->buf[0] = 0x67452301;
  ctx->buf[1] = 0xefcdab89;
  ctx->buf[2] = 0x98badcfe;
  ctx->buf[3] = 0x10325476;

  ctx->bits[0] = 0;
  ctx->bits[1] = 0;
}

static void MD5Transform(uint32_t buf[4], uint32_t const in[16]) {
  register uint32_t a, b, c, d;

  a = buf[0];
  b = buf[1];
  c = buf[2];
  d = buf[3];

  MD5STEP(F1, a, b, c, d, in[0] + 0xd76aa478, 7);
  MD5STEP(F1, d, a, b, c, in[1] + 0xe8c7b756, 12);
  MD5STEP(F1, c, d, a, b, in[2] + 0x242070db, 17);
  MD5STEP(F1, b, c, d, a, in[3] + 0xc1bdceee, 22);
  MD5STEP(F1, a, b, c, d, in[4] + 0xf57c0faf, 7);
  MD5STEP(F1, d, a, b, c, in[5] + 0x4787c62a, 12);
  MD5STEP(F1, c, d, a, b, in[6] + 0xa8304613, 17);
  MD5STEP(F1, b, c, d, a, in[7] + 0xfd469501, 22);
  MD5STEP(F1, a, b, c, d, in[8] + 0x698098d8, 7);
  MD5STEP(F1, d, a, b, c, in[9] + 0x8b44f7af, 12);
  MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
  MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7be, 22);
  MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122, 7);
  MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193, 12);
  MD5STEP(F1, c, d, a, b, in[14] + 0xa679438e, 17);
  MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821, 22);

  MD5STEP(F2, a, b, c, d, in[1] + 0xf61e2562, 5);
  MD5STEP(F2, d, a, b, c, in[6] + 0xc040b340, 9);
  MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51, 14);
  MD5STEP(F2, b, c, d, a, in[0] + 0xe9b6c7aa, 20);
  MD5STEP(F2, a, b, c, d, in[5] + 0xd62f105d, 5);
  MD5STEP(F2, d, a, b, c, in[10] + 0x02441453, 9);
  MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
  MD5STEP(F2, b, c, d, a, in[4] + 0xe7d3fbc8, 20);
  MD5STEP(F2, a, b, c, d, in[9] + 0x21e1cde6, 5);
  MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6, 9);
  MD5STEP(F2, c, d, a, b, in[3] + 0xf4d50d87, 14);
  MD5STEP(F2, b, c, d, a, in[8] + 0x455a14ed, 20);
  MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905, 5);
  MD5STEP(F2, d, a, b, c, in[2] + 0xfcefa3f8, 9);
  MD5STEP(F2, c, d, a, b, in[7] + 0x676f02d9, 14);
  MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);

  MD5STEP(F3, a, b, c, d, in[5] + 0xfffa3942, 4);
  MD5STEP(F3, d, a, b, c, in[8] + 0x8771f681, 11);
  MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
  MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380c, 23);
  MD5STEP(F3, a, b, c, d, in[1] + 0xa4beea44, 4);
  MD5STEP(F3, d, a, b, c, in[4] + 0x4bdecfa9, 11);
  MD5STEP(F3, c, d, a, b, in[7] + 0xf6bb4b60, 16);
  MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
  MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6, 4);
  MD5STEP(F3, d, a, b, c, in[0] + 0xeaa127fa, 11);
  MD5STEP(F3, c, d, a, b, in[3] + 0xd4ef3085, 16);
  MD5STEP(F3, b, c, d, a, in[6] + 0x04881d05, 23);
  MD5STEP(F3, a, b, c, d, in[9] + 0xd9d4d039, 4);
  MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
  MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
  MD5STEP(F3, b, c, d, a, in[2] + 0xc4ac5665, 23);

  MD5STEP(F4, a, b, c, d, in[0] + 0xf4292244, 6);
  MD5STEP(F4, d, a, b, c, in[7] + 0x432aff97, 10);
  MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7, 15);
  MD5STEP(F4, b, c, d, a, in[5] + 0xfc93a039, 21);
  MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3, 6);
  MD5STEP(F4, d, a, b, c, in[3] + 0x8f0ccc92, 10);
  MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47d, 15);
  MD5STEP(F4, b, c, d, a, in[1] + 0x85845dd1, 21);
  MD5STEP(F4, a, b, c, d, in[8] + 0x6fa87e4f, 6);
  MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
  MD5STEP(F4, c, d, a, b, in[6] + 0xa3014314, 15);
  MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
  MD5STEP(F4, a, b, c, d, in[4] + 0xf7537e82, 6);
  MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235, 10);
  MD5STEP(F4, c, d, a, b, in[2] + 0x2ad7d2bb, 15);
  MD5STEP(F4, b, c, d, a, in[9] + 0xeb86d391, 21);

  buf[0] += a;
  buf[1] += b;
  buf[2] += c;
  buf[3] += d;
}

static void MD5Update(MD5_CTX *ctx, unsigned char const *buf, unsigned len) {
  uint32_t t;

  t = ctx->bits[0];
  if ((ctx->bits[0] = t + ((uint32_t) len << 3)) < t)
    ctx->bits[1]++;
  ctx->bits[1] += len >> 29;

  t = (t >> 3) & 0x3f;

  if (t) {
    unsigned char *p = (unsigned char *) ctx->in + t;

    t = 64 - t;
    if (len < t) {
      memcpy(p, buf, len);
      return;
    }
    memcpy(p, buf, t);
    byteReverse(ctx->in, 16);
    MD5Transform(ctx->buf, (uint32_t *) ctx->in);
    buf += t;
    len -= t;
  }

  while (len >= 64) {
    memcpy(ctx->in, buf, 64);
    byteReverse(ctx->in, 16);
    MD5Transform(ctx->buf, (uint32_t *) ctx->in);
    buf += 64;
    len -= 64;
  }

  memcpy(ctx->in, buf, len);
}

static void MD5Final(unsigned char digest[16], MD5_CTX *ctx) {
  unsigned count;
  unsigned char *p;
  uint32_t *a;

  count = (ctx->bits[0] >> 3) & 0x3F;

  p = ctx->in + count;
  *p++ = 0x80;
  count = 64 - 1 - count;
  if (count < 8) {
    memset(p, 0, count);
    byteReverse(ctx->in, 16);
    MD5Transform(ctx->buf, (uint32_t *) ctx->in);
    memset(ctx->in, 0, 56);
  } else {
    memset(p, 0, count - 8);
  }
  byteReverse(ctx->in, 14);

  a = (uint32_t *)ctx->in;
  a[14] = ctx->bits[0];
  a[15] = ctx->bits[1];

  MD5Transform(ctx->buf, (uint32_t *) ctx->in);
  byteReverse((unsigned char *) ctx->buf, 4);
  memcpy(digest, ctx->buf, 16);
  memset((char *) ctx, 0, sizeof(*ctx));
}
#endif // !HAVE_MD5



// Stringify binary data. Output buffer must be twice as big as input,
// because each byte takes 2 bytes in string representation
static void bin2str(char *to, const unsigned char *p, size_t len) {
  static const char *hex = "0123456789abcdef";

  for (; len--; p++) {
    *to++ = hex[p[0] >> 4];
    *to++ = hex[p[0] & 0x0f];
  }
  *to = '\0';
}

// Return stringified MD5 hash for list of strings. Buffer must be 33 bytes.
char *mg_md5(char buf[33], ...) {
  unsigned char hash[16];
  const char *p;
  va_list ap;
  MD5_CTX ctx;

  MD5Init(&ctx);

  va_start(ap, buf);
  while ((p = va_arg(ap, const char *)) != NULL) {
    MD5Update(&ctx, (const unsigned char *) p, (unsigned) strlen(p));
  }
  va_end(ap);

  MD5Final(hash, &ctx);
  bin2str(buf, hash, sizeof(hash));
  return buf;
}

// Check the user's password, return 1 if OK
static int check_password(const char *method, const char *ha1, const char *uri,
                          const char *nonce, const char *nc, const char *cnonce,
                          const char *qop, const char *response) {
  char ha2[32 + 1], expected_response[32 + 1];

#if 0
  // Check for authentication timeout
  if ((unsigned long) time(NULL) - (unsigned long) to64(nonce) > 3600 * 2) {
    return 0;
  }
#endif

  mg_md5(ha2, method, ":", uri, NULL);
  mg_md5(expected_response, ha1, ":", nonce, ":", nc,
      ":", cnonce, ":", qop, ":", ha2, NULL);

  return mg_strcasecmp(response, expected_response) == 0 ? MG_TRUE : MG_FALSE;
}


// Authorize against the opened passwords file. Return 1 if authorized.
int mg_authorize_digest(struct mg_connection *c, FILE *fp) {
  struct connection *conn = MG_CONN_2_CONN(c);
  const char *hdr;
  char line[256], f_user[256], ha1[256], f_domain[256], user[100], nonce[100],
       uri[MAX_REQUEST_SIZE], cnonce[100], resp[100], qop[100], nc[100];

  if (c == NULL || fp == NULL) return 0;
  if ((hdr = mg_get_header(c, "Authorization")) == NULL ||
      mg_strncasecmp(hdr, "Digest ", 7) != 0) return 0;
  if (!mg_parse_header(hdr, "username", user, sizeof(user))) return 0;
  if (!mg_parse_header(hdr, "cnonce", cnonce, sizeof(cnonce))) return 0;
  if (!mg_parse_header(hdr, "response", resp, sizeof(resp))) return 0;
  if (!mg_parse_header(hdr, "uri", uri, sizeof(uri))) return 0;
  if (!mg_parse_header(hdr, "qop", qop, sizeof(qop))) return 0;
  if (!mg_parse_header(hdr, "nc", nc, sizeof(nc))) return 0;
  if (!mg_parse_header(hdr, "nonce", nonce, sizeof(nonce))) return 0;

  while (fgets(line, sizeof(line), fp) != NULL) {
    if (sscanf(line, "%[^:]:%[^:]:%s", f_user, f_domain, ha1) == 3 &&
        !strcmp(user, f_user) &&
        // NOTE(lsm): due to a bug in MSIE, we do not compare URIs
        !strcmp(conn->server->config_options[AUTH_DOMAIN], f_domain))
      return check_password(c->request_method, ha1, uri,
                            nonce, nc, cnonce, qop, resp);
  }
  return MG_FALSE;
}


// Return 1 if request is authorised, 0 otherwise.
static int is_authorized(struct connection *conn, const char *path) {
  FILE *fp;
  int authorized = MG_TRUE;

  if ((fp = open_auth_file(conn, path)) != NULL) {
    authorized = mg_authorize_digest(&conn->mg_conn, fp);
    fclose(fp);
  }

  return authorized;
}

static int is_authorized_for_dav(struct connection *conn) {
  const char *auth_file = conn->server->config_options[DAV_AUTH_FILE];
  const char *method = conn->mg_conn.request_method;
  FILE *fp;
  int authorized = MG_FALSE;

  // If dav_auth_file is not set, allow non-authorized PROPFIND
  if (method != NULL && !strcmp(method, "PROPFIND") && auth_file == NULL) {
    authorized = MG_TRUE;
  } else if (auth_file != NULL && (fp = fopen(auth_file, "r")) != NULL) {
    authorized = mg_authorize_digest(&conn->mg_conn, fp);
    fclose(fp);
  }

  return authorized;
}

static int is_dav_request(const struct connection *conn) {
  const char *s = conn->mg_conn.request_method;
  return !strcmp(s, "PUT") || !strcmp(s, "DELETE") ||
    !strcmp(s, "MKCOL") || !strcmp(s, "PROPFIND");
}
#endif // MONGOOSE_NO_AUTH

static int parse_header(const char *str, int str_len, const char *var_name,
                        char *buf, size_t buf_size) {
  int ch = ' ', len = 0, n = strlen(var_name);
  const char *p, *end = str + str_len, *s = NULL;

  if (buf != NULL && buf_size > 0) buf[0] = '\0';

  // Find where variable starts
  for (s = str; s != NULL && s + n < end; s++) {
    if ((s == str || s[-1] == ' ' || s[-1] == ',') && s[n] == '=' &&
        !memcmp(s, var_name, n)) break;
  }

  if (s != NULL && &s[n + 1] < end) {
    s += n + 1;
    if (*s == '"' || *s == '\'') ch = *s++;
    p = s;
    while (p < end && p[0] != ch && p[0] != ',' && len < (int) buf_size) {
      if (p[0] == '\\' && p[1] == ch) p++;
      buf[len++] = *p++;
    }
    if (len >= (int) buf_size || (ch != ' ' && *p != ch)) {
      len = 0;
    } else {
      if (len > 0 && s[len - 1] == ',') len--;
      if (len > 0 && s[len - 1] == ';') len--;
      buf[len] = '\0';
    }
  }

  return len;
}

int mg_parse_header(const char *s, const char *var_name, char *buf,
                    size_t buf_size) {
  return parse_header(s, s == NULL ? 0 : strlen(s), var_name, buf, buf_size);
}

#ifndef MONGOOSE_NO_SSI
static void send_ssi_file(struct mg_connection *, const char *, FILE *, int);

static void send_file_data(struct mg_connection *conn, FILE *fp) {
  char buf[IOBUF_SIZE];
  int n;
  while ((n = fread(buf, 1, sizeof(buf), fp)) > 0) {
    mg_write(conn, buf, n);
  }
}

static void do_ssi_include(struct mg_connection *conn, const char *ssi,
                           char *tag, int include_level) {
  char file_name[IOBUF_SIZE], path[MAX_PATH_SIZE], *p;
  char **opts = (MG_CONN_2_CONN(conn))->server->config_options;
  FILE *fp;

  // sscanf() is safe here, since send_ssi_file() also uses buffer
  // of size MG_BUF_LEN to get the tag. So strlen(tag) is always < MG_BUF_LEN.
  if (sscanf(tag, " virtual=\"%[^\"]\"", file_name) == 1) {
    // File name is relative to the webserver root
    mg_snprintf(path, sizeof(path), "%s%c%s",
                opts[DOCUMENT_ROOT], '/', file_name);
  } else if (sscanf(tag, " abspath=\"%[^\"]\"", file_name) == 1) {
    // File name is relative to the webserver working directory
    // or it is absolute system path
    mg_snprintf(path, sizeof(path), "%s", file_name);
  } else if (sscanf(tag, " file=\"%[^\"]\"", file_name) == 1 ||
             sscanf(tag, " \"%[^\"]\"", file_name) == 1) {
    // File name is relative to the currect document
    mg_snprintf(path, sizeof(path), "%s", ssi);
    if ((p = strrchr(path, '/')) != NULL) {
      p[1] = '\0';
    }
    mg_snprintf(path + strlen(path), sizeof(path) - strlen(path), "%s",
                file_name);
  } else {
    mg_printf(conn, "Bad SSI #include: [%s]", tag);
    return;
  }

  if ((fp = fopen(path, "rb")) == NULL) {
    mg_printf(conn, "Cannot open SSI #include: [%s]: fopen(%s): %s",
              tag, path, strerror(errno));
  } else {
    ns_set_close_on_exec(fileno(fp));
    if (mg_match_prefix(opts[SSI_PATTERN], strlen(opts[SSI_PATTERN]),
        path) > 0) {
      send_ssi_file(conn, path, fp, include_level + 1);
    } else {
      send_file_data(conn, fp);
    }
    fclose(fp);
  }
}

#ifndef MONGOOSE_NO_POPEN
static void do_ssi_exec(struct mg_connection *conn, char *tag) {
  char cmd[IOBUF_SIZE];
  FILE *fp;

  if (sscanf(tag, " \"%[^\"]\"", cmd) != 1) {
    mg_printf(conn, "Bad SSI #exec: [%s]", tag);
  } else if ((fp = popen(cmd, "r")) == NULL) {
    mg_printf(conn, "Cannot SSI #exec: [%s]: %s", cmd, strerror(errno));
  } else {
    send_file_data(conn, fp);
    pclose(fp);
  }
}
#endif // !MONGOOSE_NO_POPEN

static void send_ssi_file(struct mg_connection *conn, const char *path,
                          FILE *fp, int include_level) {
  char buf[IOBUF_SIZE];
  int ch, offset, len, in_ssi_tag;

  if (include_level > 10) {
    mg_printf(conn, "SSI #include level is too deep (%s)", path);
    return;
  }

  in_ssi_tag = len = offset = 0;
  while ((ch = fgetc(fp)) != EOF) {
    if (in_ssi_tag && ch == '>') {
      in_ssi_tag = 0;
      buf[len++] = (char) ch;
      buf[len] = '\0';
      assert(len <= (int) sizeof(buf));
      if (len < 6 || memcmp(buf, "<!--#", 5) != 0) {
        // Not an SSI tag, pass it
        (void) mg_write(conn, buf, (size_t) len);
      } else {
        if (!memcmp(buf + 5, "include", 7)) {
          do_ssi_include(conn, path, buf + 12, include_level);
#if !defined(MONGOOSE_NO_POPEN)
        } else if (!memcmp(buf + 5, "exec", 4)) {
          do_ssi_exec(conn, buf + 9);
#endif // !NO_POPEN
        } else {
          mg_printf(conn, "%s: unknown SSI " "command: \"%s\"", path, buf);
        }
      }
      len = 0;
    } else if (in_ssi_tag) {
      if (len == 5 && memcmp(buf, "<!--#", 5) != 0) {
        // Not an SSI tag
        in_ssi_tag = 0;
      } else if (len == (int) sizeof(buf) - 2) {
        mg_printf(conn, "%s: SSI tag is too large", path);
        len = 0;
      }
      buf[len++] = ch & 0xff;
    } else if (ch == '<') {
      in_ssi_tag = 1;
      if (len > 0) {
        mg_write(conn, buf, (size_t) len);
      }
      len = 0;
      buf[len++] = ch & 0xff;
    } else {
      buf[len++] = ch & 0xff;
      if (len == (int) sizeof(buf)) {
        mg_write(conn, buf, (size_t) len);
        len = 0;
      }
    }
  }

  // Send the rest of buffered data
  if (len > 0) {
    mg_write(conn, buf, (size_t) len);
  }
}