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WIP: Changed is_hsts() function to check both https endpoints. #204

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WIP: Changed is_hsts() function to check both https endpoints. #204

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a8702c5
Changed is_hsts() function to check both https endpoints.
mcdonnnj Aug 15, 2019
7f113b8
If neither https endpoint is live a value of 'None' is expected.
mcdonnnj Aug 15, 2019
001d14e
Handle None in is_hsts()
echudow Aug 20, 2019
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18 changes: 11 additions & 7 deletions pshtt/pshtt.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1199,16 +1199,20 @@ def is_missing_intermediate_cert(domain):

def is_hsts(domain):
"""
Domain has HSTS if its canonical HTTPS endpoint has HSTS.
Domain has HSTS if both https and httpswww endpoints have HSTS when live.
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The canonical endpoint was (I think) introduced by @h-m-f-t in an effort to make the HTTPS report results more digestible by the less technical. I'd have to know his thoughts on this change before approving.

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I think @climber-girl 's point was that if both endpoints are live then both should have HSTS. I think this section of RFC6797 touches on what I mean although it is in the context of a web application and the includeSubDomains directive.

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I don't completely understand all of the reasons for only focusing on the canonical endpoint. It seems like we assume that that is where most users will end up, but plenty of others may use the other endpoint (if it is live), and attackers could take advantage of the other endpoint (via spear-phishing URLs and the like) if it is not sufficiently protected.

strictly_forces_https already looks at both http endpoints, not just the canonical one, but downgrades_https currently only looks at the canonical https endpoint. If we switch this HSTS check to check both endpoints, then we should probably change some other checks to look at both endpoints (such as downgrades_https and maybe even follow-on sslyze checks). Should most of these checks for both endpoints be in new "Strictly_Enforces" checks or should these be changed in the existing checks?

"""
canonical, https, httpswww = domain.canonical, domain.https, domain.httpswww
https, httpswww = domain.https, domain.httpswww

if canonical.host == "www":
canonical_https = httpswww
else:
canonical_https = https
if not https.live and not httpswww.live:
return None

hsts = True
if https.live:
hsts &= https.hsts
if httpswww.live:
hsts &= httpswww.hsts

return canonical_https.hsts
return hsts


def hsts_header(domain):
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