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Updating hash function for MsalAuth._client_credential_cache #347

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Rodrigo Brandão (rodrigobr-msft) wants to merge 1 commit into from
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Updating hash function for MsalAuth._client_credential_cache #347

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2 changes: 1 addition & 1 deletion ...es/microsoft-agents-authentication-msal/microsoft_agents/authentication/msal/msal_auth.py
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Original file line number Diff line number Diff line change
Expand Up @@ -227,7 +227,7 @@ def _create_client_application(
cert = load_pem_x509_certificate(
data=bytes(public_certificate, "UTF-8"), backend=default_backend()
)
thumbprint = cert.fingerprint(hashes.SHA1()).hex()
thumbprint = cert.fingerprint(hashes.SHA256()).hex()

Copilot AI Mar 31, 2026

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Switching the certificate thumbprint hash from SHA-1 to SHA-256 changes both the value and length (40 hex chars -> 64). Since this value is passed to MSAL as the client_credential['thumbprint'], please verify MSAL/AAD expects a SHA-256 thumbprint here; if MSAL is still using the x5t (SHA-1) header/claim, this will break certificate-based authentication. If SHA-256 is the goal, consider using the MSAL-supported field/claim for SHA-256 (e.g., x5t#S256 / a dedicated thumbprint_sha256 parameter) or providing both where supported.

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self._client_credential_cache = {
"thumbprint": thumbprint,
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