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Add code to handle stash files using keytab format

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In krb5 1.7 and later, the stash file (/var/kerberos/krb5kdc/.k5.$REALM
on Fedora) is created in the regular keytab format instead of the older
less-portable one.  Based from comments and code in kt_file.c, here's a
change to try to recognize that case (the file starts with a magic
number) and read the master key from Python.

The KDC will still read either format, so I left the bits that set
things up on replicas alone (advice appreciated).  The patch works as
expected on my 64-bit box, both on RHEL5 (krb5 1.6.1 with a traditional
stash file) and on Raw Hide (krb5 1.7 with a keytab).
This commit is contained in:
Nalin Dahyabhai 2009-11-24 12:04:58 -05:00 committed by Simo Sorce
parent 5d2bbf5325
commit a094dfa91c
1 changed files with 59 additions and 3 deletions
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62
ipaserver/install/krbinstance.py
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@ -318,12 +318,68 @@ class KrbInstance(service.Service):
self._ldap_mod("pwd-extop-conf.ldif", self.sub_dict)
def __add_master_key(self):
#check for a keytab file by checking if the header magic is for a keytab
def __is_keytab(header):
if header == 0x0502 or header == 0x0501 or header == 0x0205 or header == 0x0105:
return 1
else:
return 0
#check whether a keytab file is v1 or v2
def __keytab_version(header):
if header == 0x0502 or header == 0x0205:
return 2
elif header == 0x0501 or header == 0x0105:
return 1
else:
return 0
#get the Master Key from the stash file
try:
stash = open("/var/kerberos/krb5kdc/.k5."+self.realm, "r")
keytype = struct.unpack('h', stash.read(2))[0]
keylen = struct.unpack('i', stash.read(4))[0]
keydata = stash.read(keylen)
if __is_keytab(keytype):
#in v2, all numbers are stored in network order
if __keytab_version(keytype) > 1:
__endian = '!'
else:
__endian = ''
#walk the first entry (there should only be one)
keyentrylen = struct.unpack(__endian + 'i', stash.read(4))[0]
#number of components in the principal name
keyprinccomps = struct.unpack(__endian + 'h', stash.read(2))[0]
#version 1 counted the realm as a component, version 2 doesn't
if __keytab_version(keytype) == 1:
keyprinccomps = keyprinccomps - 1
keyprinc = []
#read the components. the realm goes first, so we should
#end up with (realm, "K", "M")
for i in range(keyprinccomps + 1):
keyprinccompsize = struct.unpack(__endian + 'h', stash.read(2))[0]
keyprinc = keyprinc + [stash.read(keyprinccompsize)]
#version 2 added the principal name type, otherwise we just
#assume it's a regular old principal name
if __keytab_version(keytype) > 1:
keyprinctype = struct.unpack(__endian + 'i', stash.read(4))[0]
else:
keyprinctype = 1
#date the key was added to this keytab
keydate = struct.unpack(__endian + 'i', stash.read(4))[0]
#kvno
keyversion = struct.unpack('B', stash.read(1))[0]
#read the real enctype
keytype = struct.unpack(__endian + 'h', stash.read(2))[0]
keylen = struct.unpack(__endian + 'h', stash.read(2))[0]
keydata = stash.read(keylen)
#check that we parsed the whole file, so no surprises
keyoffset = stash.tell()
stash.seek(0,2)
if stash.tell() != keyoffset:
logging.critical("Unexpected unprocessed data in Stash file (processed %ld bytes, %ld left)." % (keyoffset, stash.tell() - keyoffset))
else:
keyversion = 1
keyprinctype = 1
keyprinc = [self.realm,"K","M"]
keylen = struct.unpack('i', stash.read(4))[0]
keydata = stash.read(keylen)
except os.error:
logging.critical("Failed to retrieve Master Key from Stash file: %s")
#encode it in the asn.1 attribute
@ -331,7 +387,7 @@ class KrbInstance(service.Service):
MasterKey.setComponentByPosition(0, univ.Integer(keytype))
MasterKey.setComponentByPosition(1, univ.OctetString(keydata))
krbMKey = univ.Sequence()
krbMKey.setComponentByPosition(0, univ.Integer(0)) #we have no kvno
krbMKey.setComponentByPosition(0, univ.Integer(keyversion))
krbMKey.setComponentByPosition(1, MasterKey)
asn1key = pyasn1.codec.ber.encoder.encode(krbMKey)