Thank you both for the help! I was able to get it working, albeit with the REST version rather than LDAP. The JSON version would probably work as well.
#========================================
# LDAP ATTRIBUTE REPOSITORY
#========================================
cas.person-directory.active-attribute-repository-ids=attributes
cas.person-directory.attribute-resolution-enabled=true
cas.person-directory.principalAttribute=sAMAccountName
cas.person-directory.return-null=false
cas.person-directory.principal-resolution-failure-fatal=true
cas.person-directory.use-existing-principal-id=false
cas.authn.attribute-repository.core.default-attributes-to-release=cn,givenName,sn,displayName,affiliation
cas.authn.attribute-repository.ldap[0].id=attributes
cas.authn.attribute-repository.ldap[0].order=0
cas.authn.attribute-repository.ldap[0].binary-attributes.objectGUID=objectGUID
cas.authn.attribute-repository.ldap[0].attributes.userPrincipalName=userPrincipalName
cas.authn.attribute-repository.ldap[0].attributes.dn=distinguishedName
cas.authn.attribute-repository.ldap[0].
attributes.sn=sn
cas.authn.attribute-repository.ldap[0].
attributes.cn=cn
cas.authn.attribute-repository.ldap[0].attributes.givenName=givenName
cas.authn.attribute-repository.ldap[0].attributes.sAMAccountName=sAMAccountName
cas.authn.attribute-repository.ldap[0].attributes.displayName=displayName
cas.authn.attribute-repository.ldap[0].attributes.memberOf=memberOf
cas.authn.attribute-repository.ldap[0].connectTimeout=PT3S
cas.authn.attribute-repository.ldap[0].baseDn=[base_dn]
cas.authn.attribute-repository.ldap[0].subtreeSearch=true
cas.authn.attribute-repository.ldap[0].searchFilter=(sAMAccountName={user})
cas.authn.attribute-repository.ldap[0].bindDn=[bind_user]
cas.authn.attribute-repository.ldap[0].bindCredential=[bind_password]
cas.authn.attribute-repository.ldap[0].ldap-url=[ldap_url]
#========================================
# Impersonation / Surrogate Authentication
#========================================
cas.authn.surrogate.rest.url=[url]
cas.authn.surrogate.principal.active-attribute-repository-ids=attributes
cas.authn.surrogate.principal.attribute-resolution-enabled=true
cas.authn.surrogate.principal.principal-attribute=sAMAccountName
cas.authn.surrogate.principal.principal-resolution-failure-fatal=true