/*
* Copyright (C) 2020 Jens Elkner. All rights reserved.
*
* License: MIT - see https://opensource.org/licenses/MIT
*/
#include "acme.h"
#include "ns_ioalib_impl.h"
#define GET_ACME_PREFIX "GET /.well-known/acme-challenge/"
#define GET_ACME_PREFIX_LEN 32
static int is_acme_req(char *req, size_t len) {
static const char *A = " - 0123456789 ABCDEFGHIJKLMNOPQRSTUVWXYZ _ abcdefghijklmnopqrstuvwxyz ";
int c, i, k;
// Check first request line. Should be like: GET path HTTP/1.x
if (strncmp(req, GET_ACME_PREFIX, GET_ACME_PREFIX_LEN))
return -1;
// Usually (for LE) the "method path" is 32 + 43 = 55 chars. But other
// implementations may choose longer pathes. We define PATHMAX = 127 chars
// to be prepared for "DoS" attacks (STUN msg size max. is ~ 64K).
len -= 21; // min size of trailing headers
if (len > 131)
len = 131;
for (i=GET_ACME_PREFIX_LEN; i < (int) len; i++) {
// find the end of the path
if (req[i] != ' ')
continue;
// consider path < 10 chars invalid. Also we wanna see a "trailer".
if (i < (GET_ACME_PREFIX_LEN + 10) || strncmp(req + i, " HTTP/1.", 8))
return -2;
// finally check for allowed chars
for (k=GET_ACME_PREFIX_LEN; k < i; k++) {
c = req[k];
if ((c > 127) || (A[c] == ' '))
return -3;
}
// all checks passed: sufficient for us to answer with a redirect
return i;
}
return -4; // end of path not found
}
int try_acme_redirect(char *req, size_t len, const char *url,
ioa_socket_handle s)
{
static const char *HTML =
"301 Moved Permanently\
301 Moved Permanently
";
char http_response[1024];
size_t plen, rlen;
if (url == NULL || url[0] == '\0' || req == NULL || s == 0 )
return 1;
if (len < (GET_ACME_PREFIX_LEN + 32) || len > (512 - GET_ACME_PREFIX_LEN)
|| (plen = is_acme_req(req, len)) < (GET_ACME_PREFIX_LEN + 1))
return 2;
req[plen] = '\0';
snprintf(http_response, sizeof(http_response) - 1,
"HTTP/1.1 301 Moved Permanently\r\n"
"Content-Type: text/html\r\n"
"Content-Length: %ld\r\n"
"Connection: close\r\n"
"Location: %s%s\r\n"
"\r\n%s", strlen(HTML), url, req + GET_ACME_PREFIX_LEN, HTML);
rlen = strlen(http_response);
#ifdef LIBEV_OK
ioa_network_buffer_handle nbh_acme = ioa_network_buffer_allocate(s->e);
uint8_t *data = ioa_network_buffer_data(nbh_acme);
bcopy(http_response, data, rlen);
ioa_network_buffer_set_size(nbh_acme, rlen);
send_data_from_ioa_socket_nbh(s, NULL, nbh_acme, TTL_IGNORE, TOS_IGNORE, NULL);
#else
if (write(s->fd, http_response, rlen) == -1) {
TURN_LOG_FUNC(TURN_LOG_LEVEL_WARNING,
"Sending redirect to '%s%s' failed",url, req + GET_ACME_PREFIX_LEN);
} else if (((turn_turnserver *)s->session->server)->verbose) {
TURN_LOG_FUNC(TURN_LOG_LEVEL_INFO, "ACME redirected to %s%s\n",
url, req + GET_ACME_PREFIX_LEN);
}
#endif
req[plen] = ' ';
return 0;
}