telebit/vendor/github.com/jcmturner/gokrb5/v8/credentials/ccache.go

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2020-06-03 06:18:04 +00:00
package credentials
import (
"bytes"
"encoding/binary"
"errors"
"io/ioutil"
"strings"
"time"
"unsafe"
"github.com/jcmturner/gofork/encoding/asn1"
"github.com/jcmturner/gokrb5/v8/types"
)
const (
headerFieldTagKDCOffset = 1
)
// CCache is the file credentials cache as define here: https://web.mit.edu/kerberos/krb5-latest/doc/formats/ccache_file_format.html
type CCache struct {
Version uint8
Header header
DefaultPrincipal principal
Credentials []*Credential
Path string
}
type header struct {
length uint16
fields []headerField
}
type headerField struct {
tag uint16
length uint16
value []byte
}
// Credential cache entry principal struct.
type principal struct {
Realm string
PrincipalName types.PrincipalName
}
// Credential holds a Kerberos client's ccache credential information.
type Credential struct {
Client principal
Server principal
Key types.EncryptionKey
AuthTime time.Time
StartTime time.Time
EndTime time.Time
RenewTill time.Time
IsSKey bool
TicketFlags asn1.BitString
Addresses []types.HostAddress
AuthData []types.AuthorizationDataEntry
Ticket []byte
SecondTicket []byte
}
// LoadCCache loads a credential cache file into a CCache type.
func LoadCCache(cpath string) (*CCache, error) {
c := new(CCache)
b, err := ioutil.ReadFile(cpath)
if err != nil {
return c, err
}
err = c.Unmarshal(b)
return c, err
}
// Unmarshal a byte slice of credential cache data into CCache type.
func (c *CCache) Unmarshal(b []byte) error {
p := 0
//The first byte of the file always has the value 5
if int8(b[p]) != 5 {
return errors.New("Invalid credential cache data. First byte does not equal 5")
}
p++
//Get credential cache version
//The second byte contains the version number (1 to 4)
c.Version = b[p]
if c.Version < 1 || c.Version > 4 {
return errors.New("Invalid credential cache data. Keytab version is not within 1 to 4")
}
p++
//Version 1 or 2 of the file format uses native byte order for integer representations. Versions 3 & 4 always uses big-endian byte order
var endian binary.ByteOrder
endian = binary.BigEndian
if (c.Version == 1 || c.Version == 2) && isNativeEndianLittle() {
endian = binary.LittleEndian
}
if c.Version == 4 {
err := parseHeader(b, &p, c, &endian)
if err != nil {
return err
}
}
c.DefaultPrincipal = parsePrincipal(b, &p, c, &endian)
for p < len(b) {
cred, err := parseCredential(b, &p, c, &endian)
if err != nil {
return err
}
c.Credentials = append(c.Credentials, cred)
}
return nil
}
func parseHeader(b []byte, p *int, c *CCache, e *binary.ByteOrder) error {
if c.Version != 4 {
return errors.New("Credentials cache version is not 4 so there is no header to parse.")
}
h := header{}
h.length = uint16(readInt16(b, p, e))
for *p <= int(h.length) {
f := headerField{}
f.tag = uint16(readInt16(b, p, e))
f.length = uint16(readInt16(b, p, e))
f.value = b[*p : *p+int(f.length)]
*p += int(f.length)
if !f.valid() {
return errors.New("Invalid credential cache header found")
}
h.fields = append(h.fields, f)
}
c.Header = h
return nil
}
// Parse the Keytab bytes of a principal into a Keytab entry's principal.
func parsePrincipal(b []byte, p *int, c *CCache, e *binary.ByteOrder) (princ principal) {
if c.Version != 1 {
//Name Type is omitted in version 1
princ.PrincipalName.NameType = readInt32(b, p, e)
}
nc := int(readInt32(b, p, e))
if c.Version == 1 {
//In version 1 the number of components includes the realm. Minus 1 to make consistent with version 2
nc--
}
lenRealm := readInt32(b, p, e)
princ.Realm = string(readBytes(b, p, int(lenRealm), e))
for i := 0; i < nc; i++ {
l := readInt32(b, p, e)
princ.PrincipalName.NameString = append(princ.PrincipalName.NameString, string(readBytes(b, p, int(l), e)))
}
return princ
}
func parseCredential(b []byte, p *int, c *CCache, e *binary.ByteOrder) (cred *Credential, err error) {
cred = new(Credential)
cred.Client = parsePrincipal(b, p, c, e)
cred.Server = parsePrincipal(b, p, c, e)
key := types.EncryptionKey{}
key.KeyType = int32(readInt16(b, p, e))
if c.Version == 3 {
//repeated twice in version 3
key.KeyType = int32(readInt16(b, p, e))
}
key.KeyValue = readData(b, p, e)
cred.Key = key
cred.AuthTime = readTimestamp(b, p, e)
cred.StartTime = readTimestamp(b, p, e)
cred.EndTime = readTimestamp(b, p, e)
cred.RenewTill = readTimestamp(b, p, e)
if ik := readInt8(b, p, e); ik == 0 {
cred.IsSKey = false
} else {
cred.IsSKey = true
}
cred.TicketFlags = types.NewKrbFlags()
cred.TicketFlags.Bytes = readBytes(b, p, 4, e)
l := int(readInt32(b, p, e))
cred.Addresses = make([]types.HostAddress, l, l)
for i := range cred.Addresses {
cred.Addresses[i] = readAddress(b, p, e)
}
l = int(readInt32(b, p, e))
cred.AuthData = make([]types.AuthorizationDataEntry, l, l)
for i := range cred.AuthData {
cred.AuthData[i] = readAuthDataEntry(b, p, e)
}
cred.Ticket = readData(b, p, e)
cred.SecondTicket = readData(b, p, e)
return
}
// GetClientPrincipalName returns a PrincipalName type for the client the credentials cache is for.
func (c *CCache) GetClientPrincipalName() types.PrincipalName {
return c.DefaultPrincipal.PrincipalName
}
// GetClientRealm returns the reals of the client the credentials cache is for.
func (c *CCache) GetClientRealm() string {
return c.DefaultPrincipal.Realm
}
// GetClientCredentials returns a Credentials object representing the client of the credentials cache.
func (c *CCache) GetClientCredentials() *Credentials {
return &Credentials{
username: c.DefaultPrincipal.PrincipalName.PrincipalNameString(),
realm: c.GetClientRealm(),
cname: c.DefaultPrincipal.PrincipalName,
}
}
// Contains tests if the cache contains a credential for the provided server PrincipalName
func (c *CCache) Contains(p types.PrincipalName) bool {
for _, cred := range c.Credentials {
if cred.Server.PrincipalName.Equal(p) {
return true
}
}
return false
}
// GetEntry returns a specific credential for the PrincipalName provided.
func (c *CCache) GetEntry(p types.PrincipalName) (*Credential, bool) {
cred := new(Credential)
var found bool
for i := range c.Credentials {
if c.Credentials[i].Server.PrincipalName.Equal(p) {
cred = c.Credentials[i]
found = true
break
}
}
if !found {
return cred, false
}
return cred, true
}
// GetEntries filters out configuration entries an returns a slice of credentials.
func (c *CCache) GetEntries() []*Credential {
creds := make([]*Credential, 0)
for _, cred := range c.Credentials {
// Filter out configuration entries
if strings.HasPrefix(cred.Server.Realm, "X-CACHECONF") {
continue
}
creds = append(creds, cred)
}
return creds
}
func (h *headerField) valid() bool {
// See https://web.mit.edu/kerberos/krb5-latest/doc/formats/ccache_file_format.html - Header format
switch h.tag {
case headerFieldTagKDCOffset:
if h.length != 8 || len(h.value) != 8 {
return false
}
return true
}
return false
}
func readData(b []byte, p *int, e *binary.ByteOrder) []byte {
l := readInt32(b, p, e)
return readBytes(b, p, int(l), e)
}
func readAddress(b []byte, p *int, e *binary.ByteOrder) types.HostAddress {
a := types.HostAddress{}
a.AddrType = int32(readInt16(b, p, e))
a.Address = readData(b, p, e)
return a
}
func readAuthDataEntry(b []byte, p *int, e *binary.ByteOrder) types.AuthorizationDataEntry {
a := types.AuthorizationDataEntry{}
a.ADType = int32(readInt16(b, p, e))
a.ADData = readData(b, p, e)
return a
}
// Read bytes representing a timestamp.
func readTimestamp(b []byte, p *int, e *binary.ByteOrder) time.Time {
return time.Unix(int64(readInt32(b, p, e)), 0)
}
// Read bytes representing an eight bit integer.
func readInt8(b []byte, p *int, e *binary.ByteOrder) (i int8) {
buf := bytes.NewBuffer(b[*p : *p+1])
binary.Read(buf, *e, &i)
*p++
return
}
// Read bytes representing a sixteen bit integer.
func readInt16(b []byte, p *int, e *binary.ByteOrder) (i int16) {
buf := bytes.NewBuffer(b[*p : *p+2])
binary.Read(buf, *e, &i)
*p += 2
return
}
// Read bytes representing a thirty two bit integer.
func readInt32(b []byte, p *int, e *binary.ByteOrder) (i int32) {
buf := bytes.NewBuffer(b[*p : *p+4])
binary.Read(buf, *e, &i)
*p += 4
return
}
func readBytes(b []byte, p *int, s int, e *binary.ByteOrder) []byte {
buf := bytes.NewBuffer(b[*p : *p+s])
r := make([]byte, s)
binary.Read(buf, *e, &r)
*p += s
return r
}
func isNativeEndianLittle() bool {
var x = 0x012345678
var p = unsafe.Pointer(&x)
var bp = (*[4]byte)(p)
var endian bool
if 0x01 == bp[0] {
endian = false
} else if (0x78 & 0xff) == (bp[0] & 0xff) {
endian = true
} else {
// Default to big endian
endian = false
}
return endian
}