blob: a67989f9334e4ea35922d4b532552209ebeb50c2 [file] [log] [blame]
package config
import (
"fmt"
"math/rand"
"net"
"strconv"
"strings"
"gopkg.in/jcmturner/dnsutils.v1"
)
// GetKDCs returns the count of KDCs available and a map of KDC host names keyed on preference order.
func (c *Config) GetKDCs(realm string, tcp bool) (int, map[int]string, error) {
if realm == "" {
realm = c.LibDefaults.DefaultRealm
}
kdcs := make(map[int]string)
var count int
// Get the KDCs from the krb5.conf.
var ks []string
for _, r := range c.Realms {
if r.Realm != realm {
continue
}
ks = r.KDC
}
count = len(ks)
if count > 0 {
// Order the kdcs randomly for preference.
kdcs = randServOrder(ks)
return count, kdcs, nil
}
if !c.LibDefaults.DNSLookupKDC {
return count, kdcs, fmt.Errorf("no KDCs defined in configuration for realm %s", realm)
}
// Use DNS to resolve kerberos SRV records.
proto := "udp"
if tcp {
proto = "tcp"
}
index, addrs, err := dnsutils.OrderedSRV("kerberos", proto, realm)
if err != nil {
return count, kdcs, err
}
if len(addrs) < 1 {
return count, kdcs, fmt.Errorf("no KDC SRV records found for realm %s", realm)
}
count = index
for k, v := range addrs {
kdcs[k] = strings.TrimRight(v.Target, ".") + ":" + strconv.Itoa(int(v.Port))
}
return count, kdcs, nil
}
// GetKpasswdServers returns the count of kpasswd servers available and a map of kpasswd host names keyed on preference order.
// https://web.mit.edu/kerberos/krb5-latest/doc/admin/conf_files/krb5_conf.html#realms - see kpasswd_server section
func (c *Config) GetKpasswdServers(realm string, tcp bool) (int, map[int]string, error) {
kdcs := make(map[int]string)
var count int
// Use DNS to resolve kerberos SRV records if configured to do so in krb5.conf.
if c.LibDefaults.DNSLookupKDC {
proto := "udp"
if tcp {
proto = "tcp"
}
c, addrs, err := dnsutils.OrderedSRV("kpasswd", proto, realm)
if err != nil {
return count, kdcs, err
}
if c < 1 {
c, addrs, err = dnsutils.OrderedSRV("kerberos-adm", proto, realm)
if err != nil {
return count, kdcs, err
}
}
if len(addrs) < 1 {
return count, kdcs, fmt.Errorf("no kpasswd or kadmin SRV records found for realm %s", realm)
}
count = c
for k, v := range addrs {
kdcs[k] = strings.TrimRight(v.Target, ".") + ":" + strconv.Itoa(int(v.Port))
}
} else {
// Get the KDCs from the krb5.conf an order them randomly for preference.
var ks []string
var ka []string
for _, r := range c.Realms {
if r.Realm == realm {
ks = r.KPasswdServer
ka = r.AdminServer
break
}
}
if len(ks) < 1 {
for _, k := range ka {
h, _, err := net.SplitHostPort(k)
if err != nil {
continue
}
ks = append(ks, h+":464")
}
}
count = len(ks)
if count < 1 {
return count, kdcs, fmt.Errorf("no kpasswd or kadmin defined in configuration for realm %s", realm)
}
kdcs = randServOrder(ks)
}
return count, kdcs, nil
}
func randServOrder(ks []string) map[int]string {
kdcs := make(map[int]string)
count := len(ks)
i := 1
if count > 1 {
l := len(ks)
for l > 0 {
ri := rand.Intn(l)
kdcs[i] = ks[ri]
if l > 1 {
// Remove the entry from the source slice by swapping with the last entry and truncating
ks[len(ks)-1], ks[ri] = ks[ri], ks[len(ks)-1]
ks = ks[:len(ks)-1]
l = len(ks)
} else {
l = 0
}
i++
}
} else {
kdcs[i] = ks[0]
}
return kdcs
}