Using ldap with kerberos gives "keytab not provided" error

[alxbse]

Trying to use the ldap auth provider with kerberes gives me an "keytab not provided" error. Even when the keytab-file flag is used the error is thrown. This applies to both 0.4.0 and master.

The cause for the error seems to be an erroneous if check when verifying ldap options.

https://github.com/appscode/guard/blob/a3c65d74d64b13842a9bff0357951a18623142f3/auth/providers/ldap/options.go#L136-L138

Flags used:

$ guard run --tls-ca-file /pki/ca.crt  --tls-cert-file /pki/server.crt --tls-private-key-file /pki/server.key --auth-providers ldap --ldap.server-address ldap-server --ldap.user-search-dn users-dn --ldap.group-search-dn groups-dn --ldap.auth-choice Kerberos --ldap.keytab-file /keytab-file
I0121 09:51:50.362637       1 logs.go:19] FLAG: --alsologtostderr="false"
I0121 09:51:50.362698       1 logs.go:19] FLAG: --analytics="true"
I0121 09:51:50.362714       1 logs.go:19] FLAG: --auth-providers="[ldap]"
I0121 09:51:50.362723       1 logs.go:19] FLAG: --azure.client-id=""
I0121 09:51:50.362731       1 logs.go:19] FLAG: --azure.client-secret="***REDACTED***"
I0121 09:51:50.362739       1 logs.go:19] FLAG: --azure.environment=""
I0121 09:51:50.362746       1 logs.go:19] FLAG: --azure.tenant-id=""
I0121 09:51:50.362754       1 logs.go:19] FLAG: --azure.use-group-uid="true"
I0121 09:51:50.362763       1 logs.go:19] FLAG: --clock-check-interval="10m0s"
I0121 09:51:50.362771       1 logs.go:19] FLAG: --github.base-url=""
I0121 09:51:50.362779       1 logs.go:19] FLAG: --gitlab.base-url=""
I0121 09:51:50.362786       1 logs.go:19] FLAG: --gitlab.use-group-id="false"
I0121 09:51:50.362793       1 logs.go:19] FLAG: --google.admin-email=""
I0121 09:51:50.362800       1 logs.go:19] FLAG: --google.sa-json-file=""
I0121 09:51:50.362807       1 logs.go:19] FLAG: --help="false"
I0121 09:51:50.362815       1 logs.go:19] FLAG: --ldap.auth-choice="Kerberos"
I0121 09:51:50.362822       1 logs.go:19] FLAG: --ldap.bind-dn=""
I0121 09:51:50.362830       1 logs.go:19] FLAG: --ldap.bind-password="***REDACTED***"
I0121 09:51:50.362837       1 logs.go:19] FLAG: --ldap.ca-cert-file=""
I0121 09:51:50.362845       1 logs.go:19] FLAG: --ldap.group-member-attribute="member"
I0121 09:51:50.362853       1 logs.go:19] FLAG: --ldap.group-name-attribute="cn"
I0121 09:51:50.362860       1 logs.go:19] FLAG: --ldap.group-search-dn="groups-dn"
I0121 09:51:50.362868       1 logs.go:19] FLAG: --ldap.group-search-filter="(objectClass=groupOfNames)"
I0121 09:51:50.362875       1 logs.go:19] FLAG: --ldap.is-secure-ldap="false"
I0121 09:51:50.362882       1 logs.go:19] FLAG: --ldap.keytab-file="/keytab-file"
I0121 09:51:50.362889       1 logs.go:19] FLAG: --ldap.server-address="ldap-server"
I0121 09:51:50.362897       1 logs.go:19] FLAG: --ldap.server-port="389"
I0121 09:51:50.362904       1 logs.go:19] FLAG: --ldap.service-account=""
I0121 09:51:50.362913       1 logs.go:19] FLAG: --ldap.skip-tls-verification="false"
I0121 09:51:50.362921       1 logs.go:19] FLAG: --ldap.start-tls="false"
I0121 09:51:50.362929       1 logs.go:19] FLAG: --ldap.user-attribute="uid"
I0121 09:51:50.362936       1 logs.go:19] FLAG: --ldap.user-search-dn="users-dn"
I0121 09:51:50.362942       1 logs.go:19] FLAG: --ldap.user-search-filter="(objectClass=person)"
I0121 09:51:50.362950       1 logs.go:19] FLAG: --log_backtrace_at=":0"
I0121 09:51:50.362958       1 logs.go:19] FLAG: --log_dir=""
I0121 09:51:50.362964       1 logs.go:19] FLAG: --logtostderr="true"
I0121 09:51:50.362971       1 logs.go:19] FLAG: --max-clock-skew="2m0s"
I0121 09:51:50.362977       1 logs.go:19] FLAG: --ntp-server="0.pool.ntp.org"
I0121 09:51:50.362983       1 logs.go:19] FLAG: --secure-addr=":8443"
I0121 09:51:50.362990       1 logs.go:19] FLAG: --stderrthreshold="0"
I0121 09:51:50.362996       1 logs.go:19] FLAG: --tls-ca-file="/pki/ca.crt"
I0121 09:51:50.363003       1 logs.go:19] FLAG: --tls-cert-file="/pki/server.crt"
I0121 09:51:50.363009       1 logs.go:19] FLAG: --tls-private-key-file="/pki/server.key"
I0121 09:51:50.363014       1 logs.go:19] FLAG: --token-auth-file="***REDACTED***"
I0121 09:51:50.363025       1 logs.go:19] FLAG: --v="0"
I0121 09:51:50.363034       1 logs.go:19] FLAG: --vmodule=""
F0121 09:51:50.436546       1 server.go:71] keytab not provided