The MongoDBAuthorizationGrants X509 certificate extension (OID 1.3.6.1.4.1.34601.2.1.1") is defined as ASN.1:

MongoDBAuthorizationGrants ::= SET OF MongoDBAuthorizationGrant

MongoDBAuthorizationGrant ::= CHOICE {
 MongoDBRole,
 ...!UTF8String:"Unrecognized entity in MongoDBAuthorizationGrant"
}

MongoDBRole ::= SEQUENCE {
 role     UTF8String,
 database UTF8String
}

Since Windows lacks a good way to parse arbitrary ASN.1, a parser for the above ASN.1 needs to be written. Since we need it on Windows, we also can reuse the same code on other platforms.