CertGetIntendedKeyUsage function

The CertGetIntendedKeyUsage function acquires the intended key usage bytes from a certificate. The intended key usage can be in either the szOID_KEY_USAGE ("2.5.29.15") or szOID_KEY_ATTRIBUTES ("2.5.29.2") extension.

Syntax

BOOL WINAPI CertGetIntendedKeyUsage(
  _In_  DWORD      dwCertEncodingType,
  _In_  PCERT_INFO pCertInfo,
  _Out_ BYTE       *pbKeyUsage,
  _In_  DWORD      cbKeyUsage
);

Parameters

dwCertEncodingType [in]

Specifies the encoding type used. It is always acceptable to specify both the certificate and message encoding types by combining them with a bitwise-OR operation as shown in the following example:

X509_ASN_ENCODING | PKCS_7_ASN_ENCODING

Currently defined encoding types are:

• X509_ASN_ENCODING
• PKCS_7_ASN_ENCODING

pCertInfo [in]

A pointer to CERT_INFO structure of the specified certificate.

pbKeyUsage [out]

A pointer to a buffer to receive the intended key usage. The following list shows currently defined values. These can be combined by using bitwise-OR operations.

• CERT_DATA_ENCIPHERMENT_KEY_USAGE
• CERT_DIGITAL_SIGNATURE_KEY_USAGE
• CERT_KEY_AGREEMENT_KEY_USAGE
• CERT_KEY_CERT_SIGN_KEY_USAGE
• CERT_KEY_ENCIPHERMENT_KEY_USAGE
• CERT_NON_REPUDIATION_KEY_USAGE
• CERT_OFFLINE_CRL_SIGN_KEY_USAGE

cbKeyUsage [in]

The size, in bytes, of the buffer pointed to by pbKeyUsage. Currently, the intended key usage occupies 1 or 2 bytes of data.

Return value

If the certificate does not have any intended key usage bytes, FALSE is returned and pbKeyUsage is zeroed. Otherwise, TRUE is returned and up to cbKeyUsage number of bytes are copied into pbKeyUsage. Any remaining bytes not copied are zeroed.

GetLastError returns zero if none of the required extensions is found.

If the function fails, GetLastError may return an Abstract Syntax Notation One (ASN.1) encoding/decoding error. For information about these errors, see ASN.1 Encoding/Decoding Return Values.

Requirements

See also

Data Management Functions