curl/docs/HSTS.md
Daniel Stenberg 86d33001e4
reuse: add copyright + license info to individual docs/*.md files
Instead of use 'docs/*.md' in dep5. For clarity and avoiding a wide-
matching wildcard.

+ Remove mention of old files from .reuse/dep5
+ add info to .github/dependabot.yml
+ make scripts/copyright.pl warn on non-matching patterns

Closes #13245
2024-03-31 12:01:18 +02:00

1.2 KiB

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

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