What does Windows error code 1749 (RPC_S_INVALID_AUTH_IDENTITY) mean?

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: RPC_S_INVALID_AUTH_IDENTITY the security context is invalid.

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RPC_S_UNKNOWN_AUTHN_LEVEL	RPC_S_UNKNOWN_AUTHZ_SERVICE

RPC_S_INVALID_AUTH_IDENTITY

The authentication identity is an input to the security package

RPC_S_INVALID_AUTH_IDENTITY means the explicit credential identity supplied for RPC authentication cannot be used as provided. Microsoft RPC can accept a SEC_WINNT_AUTH_IDENTITY-style structure when a binding is configured with explicit credentials instead of the process or thread identity.

This is not simply a wrong-password status. A malformed structure, incorrect ANSI/Unicode flag, inconsistent string lengths, or credentials in a form unsupported by the selected authentication service can fail before normal account authentication.

What to inspect

Verify the exact structure version and character-width variant used by the calling API.
Check user, domain, and password lengths as character counts expected by the structure, not byte counts from unrelated buffers.
Confirm the Flags field matches whether the strings are ANSI or Unicode.
Prefer default credentials when the process identity is intended; do not construct an explicit identity unnecessarily.

When explicit credentials are required, log structure metadata without logging passwords. RPC extended error information can help separate credential acquisition from later security-context negotiation.

References

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