Honor HSTS only after a valid HTTPS response establishes policy

Frame this document as a source-led configuration and assurance check: Honor HSTS only after a valid HTTPS response establishes policy. Only the official source and traced locations below supply facts. Confirm applicability before acting.

Source fact:

The official RFC 6797 — HTTP Strict Transport Security (HSTS) from RFC Editor / Internet Engineering Task Force supports the following bounded statements:

• A user agent establishes or updates dynamic HSTS state only from a valid Strict-Transport-Security field received over error-free secure transport and ignores the field over insecure HTTP. The research record locates this support at Sections 7.1 (HTTP-over-Secure-Transport Request Type) and 8.1 (Strict-Transport-Security Response Header Field Processing).
• Before loading HTTP for a known HSTS name, the user agent changes the scheme to HTTPS, maps explicit port 80 to 443, and preserves any other explicit port. The research record locates this support at Section 8.3 (URI Loading and Port Mapping).
• A connection to a known HSTS host must terminate on any secure-transport error, including certificate validation or server-identity failure. The research record locates this support at Section 8.4 (Errors in Secure Transport Establishment).

Only the traced statements above are asserted as source facts. Apply the review to clients, origin services, intermediaries, caches, proxies, gateways, protocol versions, and security-policy enforcement points after confirming that the source and deployed context match.

What the source does not establish

This RFC evidence supports only the named web or transport decision; it does not prove browser, intermediary, library, or service compatibility. It does not establish a deployment’s current state, authorize a production change, prove compliance, or show that DNS, certificates, identity providers, time, content delivery, network paths, and application ownership are healthy. Documented options are review inputs, not universal mandates.

Applicability questions

• For source statement 1 at Sections 7.1 (HTTP-over-Secure-Transport Request Type) and 8.1 (Strict-Transport-Security Response Header Field Processing), which observable configuration, record, or test can confirm applicability here?
• For source statement 2 at Section 8.3 (URI Loading and Port Mapping), which observable configuration, record, or test can confirm applicability here?
• For source statement 3 at Section 8.4 (Errors in Secure Transport Establishment), which observable configuration, record, or test can confirm applicability here?
• What inventory proves which parts of clients, origin services, intermediaries, caches, proxies, gateways, protocol versions, and security-policy enforcement points are in and out of scope?
• Which condition in DNS, certificates, identity providers, time, content delivery, network paths, and application ownership must be healthy before evidence is trustworthy?
• What result would disprove the working assumption and return the issue to the owner?

DSE recommendation:

DSE recommends using the cited source as the evidence anchor for this decision. Begin by recording scope and current state before deciding whether a change is warranted. Record the source location, examined part of clients, origin services, intermediaries, caches, proxies, gateways, protocol versions, and security-policy enforcement points, observed and expected states, owner, and reason for deviation.

Translate the conclusion into change control only after documenting dependencies, impact, test method, expected signals, failure signals, and restoration steps. Include DNS, certificates, identity providers, time, content delivery, network paths, and application ownership, while excluding secrets and sensitive personal or topology data from ordinary tickets.

Verification and evidence

Keep the source locations Sections 7.1 (HTTP-over-Secure-Transport Request Type) and 8.1 (Strict-Transport-Security Response Header Field Processing); Section 8.3 (URI Loading and Port Mapping); Section 8.4 (Errors in Secure Transport Establishment) adjacent to the sanitized artifacts used for comparison. Prefer request and response captures, negotiated protocol details, headers, cache behavior, certificate state, and server or proxy logs, with enough identity and timing data for an independent recheck.

Record the decision even when no change is made, including uncertainty and the next trigger. Use safe testing conditions for disruptive work, preserve rollback proof, and revisit the conclusion after relevant platform, dependency, vendor, or ownership changes.

Official references

• RFC 6797 — HTTP Strict Transport Security (HSTS) — RFC Editor / Internet Engineering Task Force