[otrs] SHA1 instead of MD5 for customer authentication

Hello Guys Is there any hack about authenticating customers against a stored sha1 hash instead the md5? Our customer database is storing the login credentials as sha1 hash (and it is used for other purposes too, so i cant change it). We want to use the same source of information so I must find a way to "hack" the code in that manner. AFAIK otrs is only capable to authenticate against plain or crypt passwords or the md5 hash. Any ideas about this? Thanks in advance. Regards, Bruce