I've been trying to research how to correctly escape search filters, and I can't find any single reliable source that makes sense.

I look at RFC 2253 (http://www.ietf.org/rfc/rfc2253.txt) section 2.4, and this IBM webpage ( http://publib.boulder.ibm.com/infocenter/iseries/v5r3/index.jsp?topic=/rzahy... ), and they both seem to suggest that you need to escape (for example) the '+' sign.

But when I escape a search filter like this: (&(objectclass=person)(facsimileTelephoneNumber=+1234)) to this: (&(objectclass=person)(facsimileTelephoneNumber=+1234)) it results in a bad filter.

My hunch is that perhaps DNs, attribute names, and attribute values are all escaped different.

Is there a simple explanation online on how to escape search filters?

RFC2253 was about string representation of DN, not filters. RFC2254 was about search filters. They are both deprecated. See RFC4510 for a list of RFCs related to the current specification of LDAP. In any case, '+' does not need any escaping in search filters. Escaping requires '' + two-digit hex representation of escaped octet; in your case, '\2B'.

p.