mongoose.c

static void on_cgi_data(struct ns_connection *nc) {
  struct connection *conn = (struct connection *) nc->connection_data;
  const char *status = "500";
  struct mg_connection c;

  if (!conn) return;

  // Copy CGI data from CGI socket to the client send buffer
  ns_forward(nc, conn->ns_conn);

  // If reply has not been parsed yet, parse it
  if (conn->ns_conn->flags & NSF_BUFFER_BUT_DONT_SEND) {
    struct iobuf *io = &conn->ns_conn->send_iobuf;
    int s_len = sizeof(cgi_status) - 1;
    int len = get_request_len(io->buf + s_len, io->len - s_len);
    char buf[MAX_REQUEST_SIZE], *s = buf;

    if (len == 0) return;

    if (len < 0 || len > (int) sizeof(buf)) {
      len = io->len;
      iobuf_remove(io, io->len);
      send_http_error(conn, 500, "CGI program sent malformed headers: [%.*s]",
        len, io->buf);
    } else {
      memset(&c, 0, sizeof(c));
      memcpy(buf, io->buf + s_len, len);
      buf[len - 1] = '\0';
      parse_http_headers(&s, &c);
      if (mg_get_header(&c, "Location") != NULL) {
        status = "302";
      } else if ((status = (char *) mg_get_header(&c, "Status")) == NULL) {
        status = "200";
      }
      memcpy(io->buf + 9, status, 3);
      conn->mg_conn.status_code = atoi(status);
    }
    conn->ns_conn->flags &= ~NSF_BUFFER_BUT_DONT_SEND;
  }
}
#endif  // !MONGOOSE_NO_CGI

static char *mg_strdup(const char *str) {
  char *copy = (char *) malloc(strlen(str) + 1);
  if (copy != NULL) {
    strcpy(copy, str);
  }
  return copy;
}

static int isbyte(int n) {
  return n >= 0 && n <= 255;
}

static int parse_net(const char *spec, uint32_t *net, uint32_t *mask) {
  int n, a, b, c, d, slash = 32, len = 0;

  if ((sscanf(spec, "%d.%d.%d.%d/%d%n", &a, &b, &c, &d, &slash, &n) == 5 ||
      sscanf(spec, "%d.%d.%d.%d%n", &a, &b, &c, &d, &n) == 4) &&
      isbyte(a) && isbyte(b) && isbyte(c) && isbyte(d) &&
      slash >= 0 && slash < 33) {
    len = n;
    *net = ((uint32_t)a << 24) | ((uint32_t)b << 16) | ((uint32_t)c << 8) | d;
    *mask = slash ? 0xffffffffU << (32 - slash) : 0;
  }

  return len;
}

// Verify given socket address against the ACL.
// Return -1 if ACL is malformed, 0 if address is disallowed, 1 if allowed.
static int check_acl(const char *acl, uint32_t remote_ip) {
  int allowed, flag;
  uint32_t net, mask;
  struct vec vec;

  // If any ACL is set, deny by default
  allowed = acl == NULL ? '+' : '-';

  while ((acl = next_option(acl, &vec, NULL)) != NULL) {
    flag = vec.ptr[0];
    if ((flag != '+' && flag != '-') ||
        parse_net(&vec.ptr[1], &net, &mask) == 0) {
      return -1;
    }

    if (net == (remote_ip & mask)) {
      allowed = flag;
    }
  }

  return allowed == '+';
}

// Protect against directory disclosure attack by removing '..',
// excessive '/' and '\' characters
static void remove_double_dots_and_double_slashes(char *s) {
  char *p = s;

  while (*s != '\0') {
    *p++ = *s++;
    if (s[-1] == '/' || s[-1] == '\\') {
      // Skip all following slashes, backslashes and double-dots
      while (s[0] != '\0') {
        if (s[0] == '/' || s[0] == '\\') { s++; }
        else if (s[0] == '.' && s[1] == '.') { s += 2; }
        else { break; }
      }
    }
  }
  *p = '\0';
}

int mg_url_decode(const char *src, int src_len, char *dst,
                  int dst_len, int is_form_url_encoded) {
  int i, j, a, b;
#define HEXTOI(x) (isdigit(x) ? x - '0' : x - 'W')

  for (i = j = 0; i < src_len && j < dst_len - 1; i++, j++) {
    if (src[i] == '%' && i < src_len - 2 &&
        isxdigit(* (const unsigned char *) (src + i + 1)) &&
        isxdigit(* (const unsigned char *) (src + i + 2))) {
      a = tolower(* (const unsigned char *) (src + i + 1));
      b = tolower(* (const unsigned char *) (src + i + 2));
      dst[j] = (char) ((HEXTOI(a) << 4) | HEXTOI(b));
      i += 2;
    } else if (is_form_url_encoded && src[i] == '+') {
      dst[j] = ' ';
    } else {
      dst[j] = src[i];
    }
  }

  dst[j] = '\0'; // Null-terminate the destination

  return i >= src_len ? j : -1;
}

static int is_valid_http_method(const char *s) {
  return !strcmp(s, "GET") || !strcmp(s, "POST") || !strcmp(s, "HEAD") ||
    !strcmp(s, "CONNECT") || !strcmp(s, "PUT") || !strcmp(s, "DELETE") ||
    !strcmp(s, "OPTIONS") || !strcmp(s, "PROPFIND") || !strcmp(s, "MKCOL");
}

// Parse HTTP request, fill in mg_request structure.
// This function modifies the buffer by NUL-terminating
// HTTP request components, header names and header values.
// Note that len must point to the last \n of HTTP headers.
static int parse_http_message(char *buf, int len, struct mg_connection *ri) {
  int is_request, n;

  // Reset the connection. Make sure that we don't touch fields that are
  // set elsewhere: remote_ip, remote_port, server_param
  ri->request_method = ri->uri = ri->http_version = ri->query_string = NULL;
  ri->num_headers = ri->status_code = ri->is_websocket = ri->content_len = 0;

  buf[len - 1] = '\0';

  // RFC says that all initial whitespaces should be ingored
  while (*buf != '\0' && isspace(* (unsigned char *) buf)) {
    buf++;
  }
  ri->request_method = skip(&buf, " ");
  ri->uri = skip(&buf, " ");
  ri->http_version = skip(&buf, "\r\n");

  // HTTP message could be either HTTP request or HTTP response, e.g.
  // "GET / HTTP/1.0 ...." or  "HTTP/1.0 200 OK ..."
  is_request = is_valid_http_method(ri->request_method);
  if ((is_request && memcmp(ri->http_version, "HTTP/", 5) != 0) ||
      (!is_request && memcmp(ri->request_method, "HTTP/", 5) != 0)) {
    len = -1;
  } else {
    if (is_request) {
      ri->http_version += 5;
    }
    parse_http_headers(&buf, ri);

    if ((ri->query_string = strchr(ri->uri, '?')) != NULL) {
      *(char *) ri->query_string++ = '\0';
    }
    n = (int) strlen(ri->uri);
    mg_url_decode(ri->uri, n, (char *) ri->uri, n + 1, 0);
    if (*ri->uri == '/' || *ri->uri == '.') {
      remove_double_dots_and_double_slashes((char *) ri->uri);
    }
  }

  return len;
}

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

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 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;
}

// Return HTTP header value, or NULL if not found.
const char *mg_get_header(const struct mg_connection *ri, const char *s) {
  int i;

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

  return NULL;
}

// Perform case-insensitive match of string against pattern
int mg_match_prefix(const char *pattern, int pattern_len, const char *str) {
  const char *or_str;
  int len, res, i = 0, j = 0;

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

  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 = mg_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;
}

// This function prints HTML pages, and expands "{{something}}" blocks
// inside HTML by calling appropriate callback functions.
// Note that {{@path/to/file}} construct outputs embedded file's contents,
// which provides SSI-like functionality.
void mg_template(struct mg_connection *conn, const char *s,
                 struct mg_expansion *expansions) {
  int i, j, pos = 0, inside_marker = 0;

  for (i = 0; s[i] != '\0'; i++) {
    if (inside_marker == 0 && !memcmp(&s[i], "{{", 2)) {
      if (i > pos) {
        mg_send_data(conn, &s[pos], i - pos);
      }
      pos = i;
      inside_marker = 1;
    }
    if (inside_marker == 1 && !memcmp(&s[i], "}}", 2)) {
      for (j = 0; expansions[j].keyword != NULL; j++) {
        const char *kw = expansions[j].keyword;
        if ((int) strlen(kw) == i - (pos + 2) &&
            memcmp(kw, &s[pos + 2], i - (pos + 2)) == 0) {
          expansions[j].handler(conn);
          pos = i + 2;
          break;
        }
      }
      inside_marker = 0;
    }
  }
  if (i > pos) {
    mg_send_data(conn, &s[pos], i - pos);
  }
}

#ifndef MONGOOSE_NO_FILESYSTEM
static int must_hide_file(struct connection *conn, const char *path) {
  const char *pw_pattern = "**" PASSWORDS_FILE_NAME "$";
  const char *pattern = conn->server->config_options[HIDE_FILES_PATTERN];
  return mg_match_prefix(pw_pattern, strlen(pw_pattern), path) > 0 ||
    (pattern != NULL && mg_match_prefix(pattern, strlen(pattern), path) > 0);
}

// Return 1 if real file has been found, 0 otherwise
static int convert_uri_to_file_name(struct connection *conn, char *buf,
                                    size_t buf_len, file_stat_t *st) {
  struct vec a, b;
  const char *rewrites = conn->server->config_options[URL_REWRITES];
  const char *root = conn->server->config_options[DOCUMENT_ROOT];
#ifndef MONGOOSE_NO_CGI
  const char *cgi_pat = conn->server->config_options[CGI_PATTERN];
  char *p;
#endif
  const char *uri = conn->mg_conn.uri;
  const char *domain = mg_get_header(&conn->mg_conn, "Host");
  int match_len, root_len = root == NULL ? 0 : strlen(root);

  // Perform virtual hosting rewrites
  if (rewrites != NULL && domain != NULL) {
    const char *colon = strchr(domain, ':');
    int domain_len = colon == NULL ? (int) strlen(domain) : colon - domain;

    while ((rewrites = next_option(rewrites, &a, &b)) != NULL) {
      if (a.len > 1 && a.ptr[0] == '@' && a.len == domain_len + 1 &&
          mg_strncasecmp(a.ptr + 1, domain, domain_len) == 0) {
        root = b.ptr;
        root_len = b.len;
        break;
      }
    }
  }

  // No filesystem access
  if (root == NULL || root_len == 0) return 0;

  // Handle URL rewrites
  mg_snprintf(buf, buf_len, "%.*s%s", root_len, root, uri);
  rewrites = conn->server->config_options[URL_REWRITES];  // Re-initialize!
  while ((rewrites = next_option(rewrites, &a, &b)) != NULL) {
    if ((match_len = mg_match_prefix(a.ptr, a.len, uri)) > 0) {
      mg_snprintf(buf, buf_len, "%.*s%s", (int) b.len, b.ptr, uri + match_len);
      break;
    }
  }

  if (stat(buf, st) == 0) return 1;

#ifndef MONGOOSE_NO_CGI
  // Support PATH_INFO for CGI scripts.
  for (p = buf + strlen(root) + 2; *p != '\0'; p++) {
    if (*p == '/') {
      *p = '\0';
      if (mg_match_prefix(cgi_pat, strlen(cgi_pat), buf) > 0 &&
          !stat(buf, st)) {
      DBG(("!!!! [%s]", buf));
        *p = '/';
        conn->path_info = mg_strdup(p);
        *p = '\0';
        return 1;
      }
      *p = '/';
    }
  }
#endif

  return 0;
}
#endif  // MONGOOSE_NO_FILESYSTEM

static int should_keep_alive(const struct mg_connection *conn) {
  struct connection *c = MG_CONN_2_CONN(conn);
  const char *method = conn->request_method;
  const char *http_version = conn->http_version;
  const char *header = mg_get_header(conn, "Connection");
  return method != NULL &&
    (!strcmp(method, "GET") || c->endpoint_type == EP_USER) &&
    ((header != NULL && !mg_strcasecmp(header, "keep-alive")) ||
     (header == NULL && http_version && !strcmp(http_version, "1.1")));
}

size_t mg_write(struct mg_connection *c, const void *buf, int len) {
  struct connection *conn = MG_CONN_2_CONN(c);
  ns_send(conn->ns_conn, buf, len);
  return conn->ns_conn->send_iobuf.len;
}

void mg_send_status(struct mg_connection *c, int status) {
  if (c->status_code == 0) {
    c->status_code = status;
    mg_printf(c, "HTTP/1.1 %d %s\r\n", status, status_code_to_str(status));
  }
}

void mg_send_header(struct mg_connection *c, const char *name, const char *v) {
  if (c->status_code == 0) {
    c->status_code = 200;
    mg_printf(c, "HTTP/1.1 %d %s\r\n", 200, status_code_to_str(200));
  }
  mg_printf(c, "%s: %s\r\n", name, v);
}

static void terminate_headers(struct mg_connection *c) {
  struct connection *conn = MG_CONN_2_CONN(c);
  if (!(conn->ns_conn->flags & MG_HEADERS_SENT)) {
    mg_send_header(c, "Transfer-Encoding", "chunked");
    mg_write(c, "\r\n", 2);
    conn->ns_conn->flags |= MG_HEADERS_SENT;
  }
}

size_t mg_send_data(struct mg_connection *c, const void *data, int data_len) {
  struct connection *conn = MG_CONN_2_CONN(c);
  terminate_headers(c);
  write_chunk(MG_CONN_2_CONN(c), (const char *) data, data_len);
  return conn->ns_conn->send_iobuf.len;
}

size_t mg_printf_data(struct mg_connection *c, const char *fmt, ...) {
  struct connection *conn = MG_CONN_2_CONN(c);
  va_list ap;
  int len;
  char mem[IOBUF_SIZE], *buf = mem;

  terminate_headers(c);

  va_start(ap, fmt);
  len = ns_avprintf(&buf, sizeof(mem), fmt, ap);
  va_end(ap);

  if (len >= 0) {
    write_chunk((struct connection *) conn, buf, len);
  }
  if (buf != mem && buf != NULL) {
    free(buf);
  }
  return conn->ns_conn->send_iobuf.len;
}

#if !defined(MONGOOSE_NO_WEBSOCKET) || !defined(MONGOOSE_NO_AUTH)
static int is_big_endian(void) {
  static const int n = 1;
  return ((char *) &n)[0] == 0;
}
#endif

#ifndef MONGOOSE_NO_WEBSOCKET
// START OF SHA-1 code
// Copyright(c) By Steve Reid <steve@edmweb.com>
#define SHA1HANDSOFF
#if defined(__sun)
#include "solarisfixes.h"
#endif

union char64long16 { unsigned char c[64]; uint32_t l[16]; };

#define rol(value, bits) (((value) << (bits)) | ((value) >> (32 - (bits))))

static uint32_t blk0(union char64long16 *block, int i) {
  // Forrest: SHA expect BIG_ENDIAN, swap if LITTLE_ENDIAN
  if (!is_big_endian()) {
    block->l[i] = (rol(block->l[i], 24) & 0xFF00FF00) |
      (rol(block->l[i], 8) & 0x00FF00FF);
  }
  return block->l[i];
}

#define blk(i) (block->l[i&15] = rol(block->l[(i+13)&15]^block->l[(i+8)&15] \
    ^block->l[(i+2)&15]^block->l[i&15],1))
#define R0(v,w,x,y,z,i) z+=((w&(x^y))^y)+blk0(block, i)+0x5A827999+rol(v,5);w=rol(w,30);
#define R1(v,w,x,y,z,i) z+=((w&(x^y))^y)+blk(i)+0x5A827999+rol(v,5);w=rol(w,30);
#define R2(v,w,x,y,z,i) z+=(w^x^y)+blk(i)+0x6ED9EBA1+rol(v,5);w=rol(w,30);
#define R3(v,w,x,y,z,i) z+=(((w|x)&y)|(w&x))+blk(i)+0x8F1BBCDC+rol(v,5);w=rol(w,30);
#define R4(v,w,x,y,z,i) z+=(w^x^y)+blk(i)+0xCA62C1D6+rol(v,5);w=rol(w,30);

typedef struct {
    uint32_t state[5];
    uint32_t count[2];
    unsigned char buffer[64];
} SHA1_CTX;

static void SHA1Transform(uint32_t state[5], const unsigned char buffer[64]) {
  uint32_t a, b, c, d, e;
  union char64long16 block[1];

  memcpy(block, buffer, 64);
  a = state[0];
  b = state[1];
  c = state[2];
  d = state[3];
  e = state[4];
  R0(a,b,c,d,e, 0); R0(e,a,b,c,d, 1); R0(d,e,a,b,c, 2); R0(c,d,e,a,b, 3);
  R0(b,c,d,e,a, 4); R0(a,b,c,d,e, 5); R0(e,a,b,c,d, 6); R0(d,e,a,b,c, 7);
  R0(c,d,e,a,b, 8); R0(b,c,d,e,a, 9); R0(a,b,c,d,e,10); R0(e,a,b,c,d,11);
  R0(d,e,a,b,c,12); R0(c,d,e,a,b,13); R0(b,c,d,e,a,14); R0(a,b,c,d,e,15);
  R1(e,a,b,c,d,16); R1(d,e,a,b,c,17); R1(c,d,e,a,b,18); R1(b,c,d,e,a,19);
  R2(a,b,c,d,e,20); R2(e,a,b,c,d,21); R2(d,e,a,b,c,22); R2(c,d,e,a,b,23);
  R2(b,c,d,e,a,24); R2(a,b,c,d,e,25); R2(e,a,b,c,d,26); R2(d,e,a,b,c,27);
  R2(c,d,e,a,b,28); R2(b,c,d,e,a,29); R2(a,b,c,d,e,30); R2(e,a,b,c,d,31);
  R2(d,e,a,b,c,32); R2(c,d,e,a,b,33); R2(b,c,d,e,a,34); R2(a,b,c,d,e,35);
  R2(e,a,b,c,d,36); R2(d,e,a,b,c,37); R2(c,d,e,a,b,38); R2(b,c,d,e,a,39);
  R3(a,b,c,d,e,40); R3(e,a,b,c,d,41); R3(d,e,a,b,c,42); R3(c,d,e,a,b,43);
  R3(b,c,d,e,a,44); R3(a,b,c,d,e,45); R3(e,a,b,c,d,46); R3(d,e,a,b,c,47);
  R3(c,d,e,a,b,48); R3(b,c,d,e,a,49); R3(a,b,c,d,e,50); R3(e,a,b,c,d,51);
  R3(d,e,a,b,c,52); R3(c,d,e,a,b,53); R3(b,c,d,e,a,54); R3(a,b,c,d,e,55);
  R3(e,a,b,c,d,56); R3(d,e,a,b,c,57); R3(c,d,e,a,b,58); R3(b,c,d,e,a,59);
  R4(a,b,c,d,e,60); R4(e,a,b,c,d,61); R4(d,e,a,b,c,62); R4(c,d,e,a,b,63);
  R4(b,c,d,e,a,64); R4(a,b,c,d,e,65); R4(e,a,b,c,d,66); R4(d,e,a,b,c,67);
  R4(c,d,e,a,b,68); R4(b,c,d,e,a,69); R4(a,b,c,d,e,70); R4(e,a,b,c,d,71);
  R4(d,e,a,b,c,72); R4(c,d,e,a,b,73); R4(b,c,d,e,a,74); R4(a,b,c,d,e,75);
  R4(e,a,b,c,d,76); R4(d,e,a,b,c,77); R4(c,d,e,a,b,78); R4(b,c,d,e,a,79);
  state[0] += a;
  state[1] += b;
  state[2] += c;
  state[3] += d;
  state[4] += e;
  // Erase working structures. The order of operations is important,
  // used to ensure that compiler doesn't optimize those out.
  memset(block, 0, sizeof(block));
  a = b = c = d = e = 0;
  (void) a; (void) b; (void) c; (void) d; (void) e;
}

static void SHA1Init(SHA1_CTX* context) {
  context->state[0] = 0x67452301;
  context->state[1] = 0xEFCDAB89;
  context->state[2] = 0x98BADCFE;
  context->state[3] = 0x10325476;
  context->state[4] = 0xC3D2E1F0;
  context->count[0] = context->count[1] = 0;
}

static void SHA1Update(SHA1_CTX* context, const unsigned char* data,
                       uint32_t len) {
  uint32_t i, j;

  j = context->count[0];
  if ((context->count[0] += len << 3) < j)
    context->count[1]++;
  context->count[1] += (len>>29);
  j = (j >> 3) & 63;
  if ((j + len) > 63) {
    memcpy(&context->buffer[j], data, (i = 64-j));
    SHA1Transform(context->state, context->buffer);
    for ( ; i + 63 < len; i += 64) {
      SHA1Transform(context->state, &data[i]);
    }
    j = 0;
  }
  else i = 0;
  memcpy(&context->buffer[j], &data[i], len - i);
}

static void SHA1Final(unsigned char digest[20], SHA1_CTX* context) {
  unsigned i;
  unsigned char finalcount[8], c;

  for (i = 0; i < 8; i++) {
    finalcount[i] = (unsigned char)((context->count[(i >= 4 ? 0 : 1)]
                                     >> ((3-(i & 3)) * 8) ) & 255);
  }
  c = 0200;
  SHA1Update(context, &c, 1);
  while ((context->count[0] & 504) != 448) {
    c = 0000;
    SHA1Update(context, &c, 1);
  }
  SHA1Update(context, finalcount, 8);
  for (i = 0; i < 20; i++) {
    digest[i] = (unsigned char)
      ((context->state[i>>2] >> ((3-(i & 3)) * 8) ) & 255);
  }
  memset(context, '\0', sizeof(*context));
  memset(&finalcount, '\0', sizeof(finalcount));
}
// END OF SHA1 CODE

static void base64_encode(const unsigned char *src, int src_len, char *dst) {
  static const char *b64 =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  int i, j, a, b, c;

  for (i = j = 0; i < src_len; i += 3) {
    a = src[i];
    b = i + 1 >= src_len ? 0 : src[i + 1];
    c = i + 2 >= src_len ? 0 : src[i + 2];

    dst[j++] = b64[a >> 2];
    dst[j++] = b64[((a & 3) << 4) | (b >> 4)];
    if (i + 1 < src_len) {
      dst[j++] = b64[(b & 15) << 2 | (c >> 6)];
    }
    if (i + 2 < src_len) {
      dst[j++] = b64[c & 63];
    }
  }
  while (j % 4 != 0) {
    dst[j++] = '=';
  }
  dst[j++] = '\0';
}

static void send_websocket_handshake(struct mg_connection *conn,
                                     const char *key) {
  static const char *magic = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
  char buf[500], sha[20], b64_sha[sizeof(sha) * 2];
  SHA1_CTX sha_ctx;

  mg_snprintf(buf, sizeof(buf), "%s%s", key, magic);
  SHA1Init(&sha_ctx);
  SHA1Update(&sha_ctx, (unsigned char *) buf, strlen(buf));
  SHA1Final((unsigned char *) sha, &sha_ctx);
  base64_encode((unsigned char *) sha, sizeof(sha), b64_sha);
  mg_snprintf(buf, sizeof(buf), "%s%s%s",
              "HTTP/1.1 101 Switching Protocols\r\n"
              "Upgrade: websocket\r\n"
              "Connection: Upgrade\r\n"
              "Sec-WebSocket-Accept: ", b64_sha, "\r\n\r\n");

  mg_write(conn, buf, strlen(buf));
}

static int deliver_websocket_frame(struct connection *conn) {
  // Having buf unsigned char * is important, as it is used below in arithmetic
  unsigned char *buf = (unsigned char *) conn->ns_conn->recv_iobuf.buf;
  int i, len, buf_len = conn->ns_conn->recv_iobuf.len, frame_len = 0,
      mask_len = 0, header_len = 0, data_len = 0, buffered = 0;

  if (buf_len >= 2) {
    len = buf[1] & 127;
    mask_len = buf[1] & 128 ? 4 : 0;
    if (len < 126 && buf_len >= mask_len) {
      data_len = len;
      header_len = 2 + mask_len;
    } else if (len == 126 && buf_len >= 4 + mask_len) {
      header_len = 4 + mask_len;
      data_len = ((((int) buf[2]) << 8) + buf[3]);
    } else if (buf_len >= 10 + mask_len) {
      header_len = 10 + mask_len;
      data_len = (int) (((uint64_t) htonl(* (uint32_t *) &buf[2])) << 32) +
        htonl(* (uint32_t *) &buf[6]);
    }
  }

  frame_len = header_len + data_len;
  buffered = frame_len > 0 && frame_len <= buf_len;

  if (buffered) {
    conn->mg_conn.content_len = data_len;
    conn->mg_conn.content = (char *) buf + header_len;
    conn->mg_conn.wsbits = buf[0];

    // Apply mask if necessary
    if (mask_len > 0) {
      for (i = 0; i < data_len; i++) {
        buf[i + header_len] ^= (buf + header_len - mask_len)[i % 4];
      }
    }

    // Call the handler and remove frame from the iobuf
    if (call_user(conn, MG_REQUEST) == MG_FALSE) {
      conn->ns_conn->flags |= NSF_FINISHED_SENDING_DATA;
    }
    iobuf_remove(&conn->ns_conn->recv_iobuf, frame_len);
  }

  return buffered;
}

size_t mg_websocket_write(struct mg_connection* conn, int opcode,
                       const char *data, size_t data_len) {
    unsigned char mem[4192], *copy = mem;
    size_t copy_len = 0;

    if (data_len + 10 > sizeof(mem) &&
        (copy = (unsigned char *) malloc(data_len + 10)) == NULL) {
      return 0;
    }

    copy[0] = 0x80 + (opcode & 0x0f);

    // Frame format: http://tools.ietf.org/html/rfc6455#section-5.2
    if (data_len < 126) {
      // Inline 7-bit length field
      copy[1] = data_len;
      memcpy(copy + 2, data, data_len);
      copy_len = 2 + data_len;
    } else if (data_len <= 0xFFFF) {
      // 16-bit length field
      copy[1] = 126;
      * (uint16_t *) (copy + 2) = (uint16_t) htons((uint16_t) data_len);
      memcpy(copy + 4, data, data_len);
      copy_len = 4 + data_len;
    } else {
      // 64-bit length field
      copy[1] = 127;
      * (uint32_t *) (copy + 2) = (uint32_t)
        htonl((uint32_t) ((uint64_t) data_len >> 32));
      * (uint32_t *) (copy + 6) = (uint32_t) htonl(data_len & 0xffffffff);
      memcpy(copy + 10, data, data_len);
      copy_len = 10 + data_len;
    }

    if (copy_len > 0) {
      mg_write(conn, copy, copy_len);
    }
    if (copy != mem) {
      free(copy);
    }

    return MG_CONN_2_CONN(conn)->ns_conn->send_iobuf.len;
}

size_t mg_websocket_printf(struct mg_connection* conn, int opcode,
                           const char *fmt, ...) {
  char mem[4192], *buf = mem;
  va_list ap;
  int len;

  va_start(ap, fmt);
  if ((len = ns_avprintf(&buf, sizeof(mem), fmt, ap)) > 0) {
    mg_websocket_write(conn, opcode, buf, len);
  }
  va_end(ap);

  if (buf != mem && buf != NULL) {
    free(buf);
  }

  return MG_CONN_2_CONN(conn)->ns_conn->send_iobuf.len;
}

static void send_websocket_handshake_if_requested(struct mg_connection *conn) {
  const char *ver = mg_get_header(conn, "Sec-WebSocket-Version"),
        *key = mg_get_header(conn, "Sec-WebSocket-Key");
  if (ver != NULL && key != NULL) {
    conn->is_websocket = 1;
    if (call_user(MG_CONN_2_CONN(conn), MG_WS_HANDSHAKE) == MG_FALSE) {
      send_websocket_handshake(conn, key);
    }
    call_user(MG_CONN_2_CONN(conn), MG_WS_CONNECT);
  }
}

static void ping_idle_websocket_connection(struct connection *conn, time_t t) {
  if (t - conn->ns_conn->last_io_time > MONGOOSE_USE_WEBSOCKET_PING_INTERVAL) {
    mg_websocket_write(&conn->mg_conn, WEBSOCKET_OPCODE_PING, "", 0);
  }
}
#else
#define ping_idle_websocket_connection(conn, t)
#endif // !MONGOOSE_NO_WEBSOCKET

static void write_terminating_chunk(struct connection *conn) {
  mg_write(&conn->mg_conn, "0\r\n\r\n", 5);
}

static int call_request_handler(struct connection *conn) {
  int result;
  conn->mg_conn.content = conn->ns_conn->recv_iobuf.buf;
  if ((result = call_user(conn, MG_REQUEST)) == MG_TRUE) {
    if (conn->ns_conn->flags & MG_HEADERS_SENT) {
      write_terminating_chunk(conn);
    }
    close_local_endpoint(conn);
  }
  return result;
}

const char *mg_get_mime_type(const char *path, const char *default_mime_type) {
  const char *ext;
  size_t i, path_len;

  path_len = strlen(path);

  for (i = 0; static_builtin_mime_types[i].extension != NULL; i++) {
    ext = path + (path_len - static_builtin_mime_types[i].ext_len);
    if (path_len > static_builtin_mime_types[i].ext_len &&
        mg_strcasecmp(ext, static_builtin_mime_types[i].extension) == 0) {
      return static_builtin_mime_types[i].mime_type;
    }
  }

  return default_mime_type;
}

#ifndef MONGOOSE_NO_FILESYSTEM
// Convert month to the month number. Return -1 on error, or month number
static int get_month_index(const char *s) {
  static const char *month_names[] = {
    "Jan", "Feb", "Mar", "Apr", "May", "Jun",
    "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
  };
  int i;

  for (i = 0; i < (int) ARRAY_SIZE(month_names); i++)
    if (!strcmp(s, month_names[i]))
      return i;

  return -1;
}

static int num_leap_years(int year) {
  return year / 4 - year / 100 + year / 400;
}

// Parse UTC date-time string, and return the corresponding time_t value.
static time_t parse_date_string(const char *datetime) {
  static const unsigned short days_before_month[] = {
    0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
  };
  char month_str[32];
  int second, minute, hour, day, month, year, leap_days, days;
  time_t result = (time_t) 0;

  if (((sscanf(datetime, "%d/%3s/%d %d:%d:%d",
               &day, month_str, &year, &hour, &minute, &second) == 6) ||
       (sscanf(datetime, "%d %3s %d %d:%d:%d",
               &day, month_str, &year, &hour, &minute, &second) == 6) ||
       (sscanf(datetime, "%*3s, %d %3s %d %d:%d:%d",
               &day, month_str, &year, &hour, &minute, &second) == 6) ||
       (sscanf(datetime, "%d-%3s-%d %d:%d:%d",
               &day, month_str, &year, &hour, &minute, &second) == 6)) &&
      year > 1970 &&
      (month = get_month_index(month_str)) != -1) {
    leap_days = num_leap_years(year) - num_leap_years(1970);
    year -= 1970;
    days = year * 365 + days_before_month[month] + (day - 1) + leap_days;
    result = days * 24 * 3600 + hour * 3600 + minute * 60 + second;
  }

  return result;
}

// Look at the "path" extension and figure what mime type it has.
// Store mime type in the vector.
static void get_mime_type(const struct mg_server *server, const char *path,
                          struct vec *vec) {
  struct vec ext_vec, mime_vec;
  const char *list, *ext;
  size_t path_len;

  path_len = strlen(path);

  // Scan user-defined mime types first, in case user wants to
  // override default mime types.
  list = server->config_options[EXTRA_MIME_TYPES];
  while ((list = next_option(list, &ext_vec, &mime_vec)) != NULL) {
    // ext now points to the path suffix
    ext = path + path_len - ext_vec.len;
    if (mg_strncasecmp(ext, ext_vec.ptr, ext_vec.len) == 0) {
      *vec = mime_vec;
      return;
    }
  }

  vec->ptr = mg_get_mime_type(path, "text/plain");
  vec->len = strlen(vec->ptr);
}

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

static void construct_etag(char *buf, size_t buf_len, const file_stat_t *st) {
  mg_snprintf(buf, buf_len, "\"%lx.%" INT64_FMT "\"",
              (unsigned long) st->st_mtime, (int64_t) st->st_size);
}

// Return True if we should reply 304 Not Modified.
static int is_not_modified(const struct connection *conn,
                           const file_stat_t *stp) {
  char etag[64];
  const char *ims = mg_get_header(&conn->mg_conn, "If-Modified-Since");
  const char *inm = mg_get_header(&conn->mg_conn, "If-None-Match");
  construct_etag(etag, sizeof(etag), stp);
  return (inm != NULL && !mg_strcasecmp(etag, inm)) ||
    (ims != NULL && stp->st_mtime <= parse_date_string(ims));
}

// For given directory path, substitute it to valid index file.
// Return 0 if index file has been found, -1 if not found.
// If the file is found, it's stats is returned in stp.
static int find_index_file(struct connection *conn, char *path,
                           size_t path_len, file_stat_t *stp) {
  const char *list = conn->server->config_options[INDEX_FILES];
  file_stat_t st;
  struct vec filename_vec;
  size_t n = strlen(path), found = 0;

  // The 'path' given to us points to the directory. Remove all trailing
  // directory separator characters from the end of the path, and
  // then append single directory separator character.
  while (n > 0 && path[n - 1] == '/') {
    n--;
  }
  path[n] = '/';

  // Traverse index files list. For each entry, append it to the given
  // path and see if the file exists. If it exists, break the loop
  while ((list = next_option(list, &filename_vec, NULL)) != NULL) {

    // Ignore too long entries that may overflow path buffer
    if (filename_vec.len > (int) (path_len - (n + 2)))
      continue;

    // Prepare full path to the index file
    strncpy(path + n + 1, filename_vec.ptr, filename_vec.len);
    path[n + 1 + filename_vec.len] = '\0';

    //DBG(("[%s]", path));

    // Does it exist?
    if (!stat(path, &st)) {
      // Yes it does, break the loop
      *stp = st;
      found = 1;
      break;
    }
  }

  // If no index file exists, restore directory path
  if (!found) {
    path[n] = '\0';
  }

  return found;
}

static int parse_range_header(const char *header, int64_t *a, int64_t *b) {
  return sscanf(header, "bytes=%" INT64_FMT "-%" INT64_FMT, a, b);
}

static void gmt_time_string(char *buf, size_t buf_len, time_t *t) {
  strftime(buf, buf_len, "%a, %d %b %Y %H:%M:%S GMT", gmtime(t));
}

static void open_file_endpoint(struct connection *conn, const char *path,
                               file_stat_t *st) {
  char date[64], lm[64], etag[64], range[64], headers[500];
  const char *msg = "OK", *hdr;
  time_t curtime = time(NULL);
  int64_t r1, r2;
  struct vec mime_vec;
  int n;

  conn->endpoint_type = EP_FILE;
  ns_set_close_on_exec(conn->endpoint.fd);
  conn->mg_conn.status_code = 200;

  get_mime_type(conn->server, path, &mime_vec);
  conn->cl = st->st_size;
  range[0] = '\0';

  // If Range: header specified, act accordingly
  r1 = r2 = 0;
  hdr = mg_get_header(&conn->mg_conn, "Range");
  if (hdr != NULL && (n = parse_range_header(hdr, &r1, &r2)) > 0 &&
      r1 >= 0 && r2 >= 0) {
    conn->mg_conn.status_code = 206;
    conn->cl = n == 2 ? (r2 > conn->cl ? conn->cl : r2) - r1 + 1: conn->cl - r1;
    mg_snprintf(range, sizeof(range), "Content-Range: bytes "
                "%" INT64_FMT "-%" INT64_FMT "/%" INT64_FMT "\r\n",
                r1, r1 + conn->cl - 1, (int64_t) st->st_size);
    msg = "Partial Content";
    lseek(conn->endpoint.fd, r1, SEEK_SET);
  }

  // Prepare Etag, Date, Last-Modified headers. Must be in UTC, according to
  // http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3
  gmt_time_string(date, sizeof(date), &curtime);
  gmt_time_string(lm, sizeof(lm), &st->st_mtime);
  construct_etag(etag, sizeof(etag), st);

  n = mg_snprintf(headers, sizeof(headers),
                  "HTTP/1.1 %d %s\r\n"
                  "Date: %s\r\n"
                  "Last-Modified: %s\r\n"
                  "Etag: %s\r\n"
                  "Content-Type: %.*s\r\n"
                  "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;
  }
}