Tribblix: manual page: CURLOPT

CURLOPT_HSTS(3) Introduction to Library Functions CURLOPT_HSTS(3)

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 allows HSTS without reading from or writing to any file. NULL
also makes libcurl clear the list of files to read HSTS data from, if
any such were previously set.

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

SECURITY CONCERNS

libcurl cannot fully protect against attacks where an attacker has
write access to the same directory where it is directed to save
files. This is particularly sensitive if you save files using
elevated privileges.

PROTOCOLS

This functionality affects http only

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

Added in curl 7.74.0

RETURN VALUE

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error
occurred, see libcurl-errors(3).