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fix(kerberos): handle KDC_ERR_ETYPE_NOSUPP as KDC_ERR_PREAUTH_REQUIRED for smart card AS exchange - #790
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Rostyslav Romanets (Rozerchik) wants to merge 1 commit into
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…D for smart card AS exchange This is workaround for the Windows Server 2016 KDC behavior. It answers a smart card AS-REQ without pre-authentication data with `KDC_ERR_ETYPE_NOSUPP` instead of `KDC_ERR_PREAUTH_REQUIRED`. The error is misleading, since the subsequent AS-REQ offers the same encryption types along with pre-authentication data and succeeds.
Rostyslav Romanets (Rozerchik)
marked this pull request as ready for review
November 3, 2026 22:04
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Problem
The KDC on Windows Server 2016 responds to the initial
AS-REQ(without pre-authentication data) withKDC_ERR_ETYPE_NOSUPPinstead of expectedKDC_ERR_PREAUTH_REQUIRED.This error is misleading. If we ignore it and proceed with the next
AS-REQ, includingPA-PK-AS-REQand the default salt, the KDC successfully processes the request and returns aAS-REP.Root cause
This issue was introduced in a738671 when IAKERB support was added.
The change restricted the accepted KDC error codes to
KDC_ERR_PREAUTH_REQUIRED. As a result, any other error code causes the failure.Previously,
KDC_ERR_ETYPE_NOSUPPwas effectively ignored, so this behavior did not cause a failure before the IAKERB implementation.Fix
This PR adds workaround to accept
KDC_ERR_ETYPE_NOSUPPwhen smart card credentials are used, so that Kerberos authentication flow can proceed.