The CERT_EXTENSION structure contains the extension information for a certificate. The data in the Value member is in its encoded representation.
typedef struct _CERT_EXTENSION {
LPSTR pszObjId;
BOOL fCritical;
CRYPT_OBJID_BLOB Value;
} CERT_EXTENSION, *PCERT_EXTENSION;
BLOB Structure, CERT_EXTENSIONS, CERT_INFO, CRL_ENTRY, CRL_INFO, CertFindExtension