curl/docs/libcurl/opts/CURLOPT_HSTS.md
Daniel Stenberg 5a488251f7
curldown: fixups
- make DEFAULT sections less repetitive

- make historic mentions use HISTORY

- generate the protocols section on `# %PROTOCOLS%` instead of guessing
  where to put it

- generate the availability section on `# %AVAILABILITY%` instead of
  guessing where to put it

- make the protocols section more verbose

Closes #14227
2024-07-19 17:03:25 +02:00

1.9 KiB

c SPDX-License-Identifier Title Section Source Protocol See-also Added-in
Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. curl CURLOPT_HSTS 3 libcurl
HTTP
CURLOPT_ALTSVC (3)
CURLOPT_HSTS_CTRL (3)
CURLOPT_RESOLVE (3)
7.74.0

NAME

CURLOPT_HSTS - HSTS cache filename

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HSTS, char *filename);

DESCRIPTION

Make the filename point to a filename to load an existing HSTS cache from, and to store the cache in when the easy handle is closed. Setting a file name with this option also enables HSTS for this handle (the equivalent of setting CURLHSTS_ENABLE with CURLOPT_HSTS_CTRL(3)).

If the given file does not exist or contains no HSTS entries at startup, the HSTS cache simply starts empty. Setting the filename to NULL or "" only enables HSTS without reading from or writing to any file.

If this option is set multiple times, libcurl loads cache entries from each given file but only stores the last used name for later writing.

FILE FORMAT

The HSTS cache is saved to and loaded from a text file with one entry per physical line. Each line in the file has the following format:

[host] [stamp]

[host] is the domain name for the entry and the name is dot-prefixed if it is an entry valid for all subdomains to the name as well or only for the exact name.

[stamp] is the time (in UTC) when the entry expires and it uses the format "YYYYMMDD HH:MM:SS".

Lines starting with "#" are treated as comments and are ignored. There is currently no length or size limit.

DEFAULT

NULL, no filename

%PROTOCOLS%

EXAMPLE

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_HSTS, "/home/user/.hsts-cache");
    curl_easy_perform(curl);
  }
}

%AVAILABILITY%

RETURN VALUE

Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.