Reject invalid backup flags combination BS without BE#129
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ScottHelme wants to merge 1 commit intolbuchs:masterfrom
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Reject invalid backup flags combination BS without BE#129ScottHelme wants to merge 1 commit intolbuchs:masterfrom
ScottHelme wants to merge 1 commit intolbuchs:masterfrom
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Per the WebAuthn spec (§6.3.3 / Level 3 §6.1), Backup State (BS) cannot be set without Backup Eligible (BE) also being set. This is a logically impossible state that no legitimate authenticator should produce. Fixes lbuchs#128
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Per the W3C WebAuthn spec (§6.3.3 Authenticator Data / Level 3 §6.1), the Backup State (BS) flag cannot be set without the Backup Eligible (BE) flag also being set. This is a logically impossible state — a credential cannot claim to be backed up if it is not eligible for backup.
Currently
_readFlags()parses both flags but does not validate this constraint, so craftedauthenticatorDatawithBS=1, BE=0is silently accepted.This adds validation after the named flags are assigned:
Fixes #128