fix(sspi): remove stale rewrite docs and harden credential diagnostics

[Richard Markiewicz (thenextman)]

Follow-up to #177, addressing review comments.

Stale documentation for a rewrite that no longer exists

#177 removed the Base CSP → KSP provider rewrite, but left behind a README section and a doc comment above sspi_CreatePackedCertificateLogon that still describe it. Both are removed here.

To be explicit, since the review suggested implementing the rewrite instead: that would regress the fix. The credential that works names Microsoft Base Smart Card Crypto Provider with KeySpec = 1 — the legacy CAPI provider — and the KSP retarget was in the arm that failed during testing. The claim was wrong, not the code.

The README text is replaced with something accurate and more useful: the credential is passed through as CredPackAuthenticationBufferW produced it, and the provider and container names it records are resolved by the server through the redirected reader — so the same smart card middleware must be installed on both ends. A mismatch surfaces as "the key container does not exist on the smart card", which is a real failure mode and easy to misattribute to the client.

Dead code

sspi_TryGetCspInfo lost its last caller when the rewrite was removed and is deleted.

Bounded credential dump

sspi_GetLocalAllocSizeAsDword returns 0 when the incoming pSpnegoCred is not a LocalAlloc block, which is common — a reconnect passes such a buffer. Zero disables the extent check in sspi_ResolvePackedField, so walking the blob would then trust CspDataLength alone and could read past the credential.

MsRdpEx_CanReadUnsafePtr still guarded every access, so this could not fault or touch unmapped memory; the exposure was logging bytes beyond the allocation. Now the fixed-size header is still reported and only the CspData walk is skipped when the size is unknown, which keeps the diagnostic useful in exactly the reconnect case that produces it.

Thread-safe environment initialisation

MsRdpEx_PcapEnvInit guarded initialisation with a plain bool while writing shared globals, including a strcpy_s into g_PcapFilePath. It is reached from
AcquireCredentialsHandleW and from the message paths, both of which run concurrently on several connection worker threads.

This race predates #177 — the message-path caller is older and hotter — and the written values are idempotent, so impact was minimal. It is now InitOnceExecuteOnce, matching the two existing uses in the same file.

[Copilot]

Pull request overview

Removes obsolete SSPI rewrite documentation and hardens credential diagnostics and environment initialization.

Changes:

• Replaces stale smart-card provider rewrite documentation.
• Removes dead CSP lookup code.
• Bounds credential parsing and serializes environment initialization.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
README.md	Documents current credential and middleware behavior.
dll/Sspi.cpp	Removes dead code and hardens diagnostics and initialization.

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