un-nest curl

curl-8.15.0/docs/HSTS.md

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+<!--
+Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+
+SPDX-License-Identifier: curl
+-->
+
+# HSTS support
+
+HTTP Strict-Transport-Security. Added as experimental in curl
+7.74.0. Supported "for real" since 7.77.0.
+
+## Standard
+
+[HTTP Strict Transport Security](https://datatracker.ietf.org/doc/html/rfc6797)
+
+## Behavior
+
+libcurl features an in-memory cache for HSTS hosts, so that subsequent
+HTTP-only requests to a hostname present in the cache gets internally
+"redirected" to the HTTPS version.
+
+## `curl_easy_setopt()` options:
+
+ - `CURLOPT_HSTS_CTRL` - enable HSTS for this easy handle
+ - `CURLOPT_HSTS` - specify filename where to store the HSTS cache on close
+  (and possibly read from at startup)
+
+## curl command line options
+
+ - `--hsts [filename]` - enable HSTS, use the file as HSTS cache. If filename
+   is `""` (no length) then no file is used, only in-memory cache.
+
+## HSTS cache file format
+
+Lines starting with `#` are ignored.
+
+For each hsts entry:
+
+    [host name] "YYYYMMDD HH:MM:SS"
+
+The `[host name]` is dot-prefixed if it includes subdomains.
+
+The time stamp is when the entry expires.
+
+## Possible future additions
+
+ - `CURLOPT_HSTS_PRELOAD` - provide a set of HSTS hostnames to load first
+ - ability to save to something else than a file