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curl/docs/examples/synctime.c

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/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
*
* This software is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at https://curl.haxx.se/docs/copyright.html.
*
* You may opt to use, copy, modify, merge, publish, distribute and/or sell
* copies of the Software, and permit persons to whom the Software is
* furnished to do so, under the terms of the COPYING file.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
***************************************************************************/
/* <DESC>
* Set your system time from a remote HTTP server's Date: header.
* </DESC>
*/
/* This example code only builds as-is on Windows.
*
* While Unix/Linux user, you do not need this software.
* You can achieve the same result as synctime using curl, awk and date.
* Set proxy as according to your network, but beware of proxy Cache-Control.
*
* To set your system clock, root access is required.
* # date -s "`curl -sI https://nist.time.gov/timezone.cgi?UTC/s/0 \
* | awk -F': ' '/Date: / {print $2}'`"
*
* To view remote webserver date and time.
* $ curl -sI https://nist.time.gov/timezone.cgi?UTC/s/0 \
* | awk -F': ' '/Date: / {print $2}'
*
* Synchronising your computer clock via Internet time server usually relies
* on DAYTIME, TIME, or NTP protocols. These protocols provide good accurate
* time synchronisation but it does not work very well through a
* firewall/proxy. Some adjustment has to be made to the firewall/proxy for
* these protocols to work properly.
*
* There is an indirect method. Since most webserver provide server time in
* their HTTP header, therefore you could synchronise your computer clock
* using HTTP protocol which has no problem with firewall/proxy.
*
* For this software to work, you should take note of these items.
* 1. Your firewall/proxy must allow your computer to surf internet.
* 2. Webserver system time must in sync with the NTP time server,
* or at least provide an accurate time keeping.
* 3. Webserver HTTP header does not provide the milliseconds units,
* so there is no way to get very accurate time.
* 4. This software could only provide an accuracy of +- a few seconds,
* as Round-Trip delay time is not taken into consideration.
* Compensation of network, firewall/proxy delay cannot be simply divide
* the Round-Trip delay time by half.
* 5. Win32 SetSystemTime() API will set your computer clock according to
* GMT/UTC time. Therefore your computer timezone must be properly set.
* 6. Webserver data should not be cached by the proxy server. Some
* webserver provide Cache-Control to prevent caching.
*
* References:
* https://web.archive.org/web/20100228012139/ \
* tf.nist.gov/timefreq/service/its.htm
* https://web.archive.org/web/20100409024302/ \
* tf.nist.gov/timefreq/service/firewall.htm
*
* Usage:
* This software will synchronise your computer clock only when you issue
* it with --synctime. By default, it only display the webserver's clock.
*
* Written by: Frank (contributed to libcurl)
*
* THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND,
* EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
* WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
*
* IN NO EVENT SHALL THE AUTHOR OF THIS SOFTWARE BE LIABLE FOR
* ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
* OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
* WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
* LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
* OF THIS SOFTWARE.
*
*/
#include <stdio.h>
#include <time.h>
#ifndef __CYGWIN__
#include <winsock2.h>
#include <windows.h>
#endif
#include <curl/curl.h>
#define MAX_STRING 256
#define MAX_STRING1 MAX_STRING + 1
#define SYNCTIME_UA "synctime/1.0"
typedef struct
{
char http_proxy[MAX_STRING1];
char proxy_user[MAX_STRING1];
char timeserver[MAX_STRING1];
} conf_t;
const char DefaultTimeServer[3][MAX_STRING1] =
{
"https://nist.time.gov/",
"https://www.google.com/"
};
const char *DayStr[] = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
const char *MthStr[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
int ShowAllHeader;
int AutoSyncTime;
SYSTEMTIME SYSTime;
SYSTEMTIME LOCALTime;
#define HTTP_COMMAND_HEAD 0
#define HTTP_COMMAND_GET 1
size_t SyncTime_CURL_WriteOutput(void *ptr, size_t size, size_t nmemb,
void *stream)
{
fwrite(ptr, size, nmemb, stream);
return (nmemb*size);
}
size_t SyncTime_CURL_WriteHeader(void *ptr, size_t size, size_t nmemb,
void *stream)
{
char TmpStr1[26], TmpStr2[26];
(void)stream;
if(ShowAllHeader == 1)
fprintf(stderr, "%s", (char *)(ptr));
if(strncmp((char *)(ptr), "Date:", 5) == 0) {
if(ShowAllHeader == 0)
fprintf(stderr, "HTTP Server. %s", (char *)(ptr));
if(AutoSyncTime == 1) {
*TmpStr1 = 0;
*TmpStr2 = 0;
if(strlen((char *)(ptr)) > 50) /* Can prevent buffer overflow to
TmpStr1 & 2? */
AutoSyncTime = 0;
else {
int RetVal = sscanf((char *)(ptr), "Date: %s %hu %s %hu %hu:%hu:%hu",
TmpStr1, &SYSTime.wDay, TmpStr2, &SYSTime.wYear,
&SYSTime.wHour, &SYSTime.wMinute,
&SYSTime.wSecond);
if(RetVal == 7) {
int i;
SYSTime.wMilliseconds = 500; /* adjust to midpoint, 0.5 sec */
for(i = 0; i<12; i++) {
if(strcmp(MthStr[i], TmpStr2) == 0) {
SYSTime.wMonth = i + 1;
break;
}
}
AutoSyncTime = 3; /* Computer clock will be adjusted */
}
else {
AutoSyncTime = 0; /* Error in sscanf() fields conversion */
}
}
}
}
if(strncmp((char *)(ptr), "X-Cache: HIT", 12) == 0) {
fprintf(stderr, "ERROR: HTTP Server data is cached."
" Server Date is no longer valid.\n");
AutoSyncTime = 0;
}
return (nmemb*size);
}
void SyncTime_CURL_Init(CURL *curl, char *proxy_port,
char *proxy_user_password)
{
if(strlen(proxy_port) > 0)
curl_easy_setopt(curl, CURLOPT_PROXY, proxy_port);
if(strlen(proxy_user_password) > 0)
curl_easy_setopt(curl, CURLOPT_PROXYUSERPWD, proxy_user_password);
#ifdef SYNCTIME_UA
curl_easy_setopt(curl, CURLOPT_USERAGENT, SYNCTIME_UA);
#endif
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, *SyncTime_CURL_WriteOutput);
curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, *SyncTime_CURL_WriteHeader);
}
int SyncTime_CURL_Fetch(CURL *curl, char *URL_Str, char *OutFileName,
int HttpGetBody)
{
FILE *outfile;
CURLcode res;
outfile = NULL;
if(HttpGetBody == HTTP_COMMAND_HEAD)
curl_easy_setopt(curl, CURLOPT_NOBODY, 1L);
else {
outfile = fopen(OutFileName, "wb");
curl_easy_setopt(curl, CURLOPT_WRITEDATA, outfile);
}
curl_easy_setopt(curl, CURLOPT_URL, URL_Str);
res = curl_easy_perform(curl);
if(outfile != NULL)
fclose(outfile);
return res; /* (CURLE_OK) */
}
void showUsage(void)
{
fprintf(stderr, "SYNCTIME: Synchronising computer clock with time server"
" using HTTP protocol.\n");
fprintf(stderr, "Usage : SYNCTIME [Option]\n");
fprintf(stderr, "Options :\n");
fprintf(stderr, " --server=WEBSERVER Use this time server instead"
" of default.\n");
fprintf(stderr, " --showall Show all HTTP header.\n");
fprintf(stderr, " --synctime Synchronising computer clock"
" with time server.\n");
fprintf(stderr, " --proxy-user=USER[:PASS] Set proxy username and"
" password.\n");
fprintf(stderr, " --proxy=HOST[:PORT] Use HTTP proxy on given"
" port.\n");
fprintf(stderr, " --help Print this help.\n");
fprintf(stderr, "\n");
return;
}
int conf_init(conf_t *conf)
{
int i;
*conf->http_proxy = 0;
for(i = 0; i<MAX_STRING1; i++)
conf->proxy_user[i] = 0; /* Clean up password from memory */
*conf->timeserver = 0;
return 1;
}
int main(int argc, char *argv[])
{
CURL *curl;
conf_t conf[1];
int RetValue;
ShowAllHeader = 0; /* Do not show HTTP Header */
AutoSyncTime = 0; /* Do not synchronise computer clock */
RetValue = 0; /* Successful Exit */
conf_init(conf);
if(argc > 1) {
int OptionIndex = 0;
while(OptionIndex < argc) {
if(strncmp(argv[OptionIndex], "--server=", 9) == 0)
snprintf(conf->timeserver, MAX_STRING, "%s", &argv[OptionIndex][9]);
if(strcmp(argv[OptionIndex], "--showall") == 0)
ShowAllHeader = 1;
if(strcmp(argv[OptionIndex], "--synctime") == 0)
AutoSyncTime = 1;
if(strncmp(argv[OptionIndex], "--proxy-user=", 13) == 0)
snprintf(conf->proxy_user, MAX_STRING, "%s", &argv[OptionIndex][13]);
if(strncmp(argv[OptionIndex], "--proxy=", 8) == 0)
snprintf(conf->http_proxy, MAX_STRING, "%s", &argv[OptionIndex][8]);
if((strcmp(argv[OptionIndex], "--help") == 0) ||
(strcmp(argv[OptionIndex], "/?") == 0)) {
showUsage();
return 0;
}
OptionIndex++;
}
}
if(*conf->timeserver == 0) /* Use default server for time information */
snprintf(conf->timeserver, MAX_STRING, "%s", DefaultTimeServer[0]);
/* Init CURL before usage */
curl_global_init(CURL_GLOBAL_ALL);
curl = curl_easy_init();
if(curl) {
struct tm *lt;
struct tm *gmt;
time_t tt;
time_t tt_local;
time_t tt_gmt;
double tzonediffFloat;
int tzonediffWord;
char timeBuf[61];
char tzoneBuf[16];
SyncTime_CURL_Init(curl, conf->http_proxy, conf->proxy_user);
/* Calculating time diff between GMT and localtime */
tt = time(0);
lt = localtime(&tt);
tt_local = mktime(lt);
gmt = gmtime(&tt);
tt_gmt = mktime(gmt);
tzonediffFloat = difftime(tt_local, tt_gmt);
tzonediffWord = (int)(tzonediffFloat/3600.0);
if((double)(tzonediffWord * 3600) == tzonediffFloat)
snprintf(tzoneBuf, 15, "%+03d'00'", tzonediffWord);
else
snprintf(tzoneBuf, 15, "%+03d'30'", tzonediffWord);
/* Get current system time and local time */
GetSystemTime(&SYSTime);
GetLocalTime(&LOCALTime);
snprintf(timeBuf, 60, "%s, %02d %s %04d %02d:%02d:%02d.%03d, ",
DayStr[LOCALTime.wDayOfWeek], LOCALTime.wDay,
MthStr[LOCALTime.wMonth-1], LOCALTime.wYear,
LOCALTime.wHour, LOCALTime.wMinute, LOCALTime.wSecond,
LOCALTime.wMilliseconds);
fprintf(stderr, "Fetch: %s\n\n", conf->timeserver);
fprintf(stderr, "Before HTTP. Date: %s%s\n\n", timeBuf, tzoneBuf);
/* HTTP HEAD command to the Webserver */
SyncTime_CURL_Fetch(curl, conf->timeserver, "index.htm",
HTTP_COMMAND_HEAD);
GetLocalTime(&LOCALTime);
snprintf(timeBuf, 60, "%s, %02d %s %04d %02d:%02d:%02d.%03d, ",
DayStr[LOCALTime.wDayOfWeek], LOCALTime.wDay,
MthStr[LOCALTime.wMonth-1], LOCALTime.wYear,
LOCALTime.wHour, LOCALTime.wMinute, LOCALTime.wSecond,
LOCALTime.wMilliseconds);
fprintf(stderr, "\nAfter HTTP. Date: %s%s\n", timeBuf, tzoneBuf);
if(AutoSyncTime == 3) {
/* Synchronising computer clock */
if(!SetSystemTime(&SYSTime)) { /* Set system time */
fprintf(stderr, "ERROR: Unable to set system time.\n");
RetValue = 1;
}
else {
/* Successfully re-adjusted computer clock */
GetLocalTime(&LOCALTime);
snprintf(timeBuf, 60, "%s, %02d %s %04d %02d:%02d:%02d.%03d, ",
DayStr[LOCALTime.wDayOfWeek], LOCALTime.wDay,
MthStr[LOCALTime.wMonth-1], LOCALTime.wYear,
LOCALTime.wHour, LOCALTime.wMinute, LOCALTime.wSecond,
LOCALTime.wMilliseconds);
fprintf(stderr, "\nNew System's Date: %s%s\n", timeBuf, tzoneBuf);
}
}
/* Cleanup before exit */
conf_init(conf);
curl_easy_cleanup(curl);
}
return RetValue;
}
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