curl/docs/libcurl/opts/CURLOPT_HSTSREADFUNCTION.md

---

c: Copyright (C) Daniel Stenberg, daniel@haxx.se, et al. SPDX-License-Identifier: curl Title: CURLOPT_HSTSREADFUNCTION Section: 3 Source: libcurl Protocol:

• HTTP See-also:
• CURLOPT_HSTS (3)
• CURLOPT_HSTSREADDATA (3)
• CURLOPT_HSTSWRITEFUNCTION (3)
• CURLOPT_HSTS_CTRL (3) Added-in: 7.74.0 ---

NAME

CURLOPT_HSTSREADFUNCTION - read callback for HSTS hosts

SYNOPSIS

#include <curl/curl.h>

struct curl_hstsentry {
  char *name;
  size_t namelen;
  unsigned int includeSubDomains:1;
  char expire[18]; /* YYYYMMDD HH:MM:SS [null-terminated] */
};

CURLSTScode hstsread(CURL *easy, struct curl_hstsentry *sts, void *clientp);

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HSTSREADFUNCTION, hstsread);

DESCRIPTION

Pass a pointer to your callback function, as the prototype shows above.

This callback function gets called by libcurl repeatedly when it populates the in-memory HSTS cache.

Set the clientp argument with the CURLOPT_HSTSREADDATA(3) option or it is NULL.

When this callback is invoked, the sts pointer points to a populated struct: Copy the hostname to name (no longer than namelen bytes). Make it null-terminated. Set includeSubDomains to TRUE or FALSE. Set expire to a date stamp or a zero length string for forever (wrong date stamp format might cause the name to not get accepted)

The callback should return CURLSTS_OK if it returns a name and is prepared to be called again (for another host) or CURLSTS_DONE if it has no entry to return. It can also return CURLSTS_FAIL to signal error. Returning CURLSTS_FAIL stops the transfer from being performed and make CURLE_ABORTED_BY_CALLBACK get returned.

This option does not enable HSTS, you need to use CURLOPT_HSTS_CTRL(3) to do that.

DEFAULT

NULL - no callback.

%PROTOCOLS%

EXAMPLE

struct priv {
  void *custom;
};

static CURLSTScode hsts_cb(CURL *easy, struct curl_hstsentry *sts,
                           void *clientp)
{
  /* populate the struct as documented */
  return CURLSTS_OK;
}

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    struct priv my_stuff;
    CURLcode res;

    /* set HSTS read callback */
    curl_easy_setopt(curl, CURLOPT_HSTSREADFUNCTION, hsts_cb);

    /* pass in suitable argument to the callback */
    curl_easy_setopt(curl, CURLOPT_HSTSREADDATA, &my_stuff);

    res = curl_easy_perform(curl);
  }
}

%AVAILABILITY%

RETURN VALUE

This returns CURLE_OK.