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krb5/SOURCES/Use-KCM_OP_RETRIEVE-in-KCM-...

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From 43e3bca2a711de257091454bc5e25a985340d847 Mon Sep 17 00:00:00 2001
From: Greg Hudson <ghudson@mit.edu>
Date: Fri, 26 Mar 2021 23:38:54 -0400
Subject: [PATCH] Use KCM_OP_RETRIEVE in KCM client
In kcm_retrieve(), try KCM_OP_RETRIEVE. Fall back to iteration if the
server doesn't implement it, or if we can an answer incompatible with
KRB5_TC_SUPPORTED_KTYPES.
In kcmserver.py, implement partial decoding for creds and cred tags so
that we can do a basic principal name match.
ticket: 8997 (new)
(cherry picked from commit 795ebba8c039be172ab93cd41105c73ffdba0fdb)
(cherry picked from commit c56d4b87de0f30a38dc61d374ad225d02d581eb3)
---
src/include/kcm.h | 2 +-
src/lib/krb5/ccache/cc_kcm.c | 52 +++++++++++++++++++++++++++++++++---
src/tests/kcmserver.py | 44 +++++++++++++++++++++++++++---
src/tests/t_ccache.py | 11 +++++---
4 files changed, 99 insertions(+), 10 deletions(-)
diff --git a/src/include/kcm.h b/src/include/kcm.h
index 9b66f1cbd..85c20d345 100644
--- a/src/include/kcm.h
+++ b/src/include/kcm.h
@@ -87,7 +87,7 @@ typedef enum kcm_opcode {
KCM_OP_INITIALIZE, /* (name, princ) -> () */
KCM_OP_DESTROY, /* (name) -> () */
KCM_OP_STORE, /* (name, cred) -> () */
- KCM_OP_RETRIEVE,
+ KCM_OP_RETRIEVE, /* (name, flags, credtag) -> (cred) */
KCM_OP_GET_PRINCIPAL, /* (name) -> (princ) */
KCM_OP_GET_CRED_UUID_LIST, /* (name) -> (uuid, ...) */
KCM_OP_GET_CRED_BY_UUID, /* (name, uuid) -> (cred) */
diff --git a/src/lib/krb5/ccache/cc_kcm.c b/src/lib/krb5/ccache/cc_kcm.c
index 46705f1da..23fcf13ea 100644
--- a/src/lib/krb5/ccache/cc_kcm.c
+++ b/src/lib/krb5/ccache/cc_kcm.c
@@ -826,9 +826,55 @@ static krb5_error_code KRB5_CALLCONV
kcm_retrieve(krb5_context context, krb5_ccache cache, krb5_flags flags,
krb5_creds *mcred, krb5_creds *cred_out)
{
- /* There is a KCM opcode for retrieving creds, but Heimdal's client doesn't
- * use it. It causes the KCM daemon to actually make a TGS request. */
- return k5_cc_retrieve_cred_default(context, cache, flags, mcred, cred_out);
+ krb5_error_code ret;
+ struct kcmreq req = EMPTY_KCMREQ;
+ krb5_creds cred;
+ krb5_enctype *enctypes = NULL;
+
+ memset(&cred, 0, sizeof(cred));
+
+ /* Include KCM_GC_CACHED in flags to prevent Heimdal's sssd from making a
+ * TGS request itself. */
+ kcmreq_init(&req, KCM_OP_RETRIEVE, cache);
+ k5_buf_add_uint32_be(&req.reqbuf, map_tcflags(flags) | KCM_GC_CACHED);
+ k5_marshal_mcred(&req.reqbuf, mcred);
+ ret = cache_call(context, cache, &req);
+
+ /* Fall back to iteration if the server does not support retrieval. */
+ if (ret == KRB5_FCC_INTERNAL || ret == KRB5_CC_IO) {
+ ret = k5_cc_retrieve_cred_default(context, cache, flags, mcred,
+ cred_out);
+ goto cleanup;
+ }
+ if (ret)
+ goto cleanup;
+
+ ret = k5_unmarshal_cred(req.reply.ptr, req.reply.len, 4, &cred);
+ if (ret)
+ goto cleanup;
+
+ /* In rare cases we might retrieve a credential with a session key this
+ * context can't support, in which case we must retry using iteration. */
+ if (flags & KRB5_TC_SUPPORTED_KTYPES) {
+ ret = krb5_get_tgs_ktypes(context, cred.server, &enctypes);
+ if (ret)
+ goto cleanup;
+ if (!k5_etypes_contains(enctypes, cred.keyblock.enctype)) {
+ ret = k5_cc_retrieve_cred_default(context, cache, flags, mcred,
+ cred_out);
+ goto cleanup;
+ }
+ }
+
+ *cred_out = cred;
+ memset(&cred, 0, sizeof(cred));
+
+cleanup:
+ kcmreq_free(&req);
+ krb5_free_cred_contents(context, &cred);
+ free(enctypes);
+ /* Heimdal's KCM returns KRB5_CC_END if no cred is found. */
+ return (ret == KRB5_CC_END) ? KRB5_CC_NOTFOUND : map_invalid(ret);
}
static krb5_error_code KRB5_CALLCONV
diff --git a/src/tests/kcmserver.py b/src/tests/kcmserver.py
index 8c5e66ff1..25e6f2bbe 100644
--- a/src/tests/kcmserver.py
+++ b/src/tests/kcmserver.py
@@ -40,6 +40,7 @@ class KCMOpcodes(object):
INITIALIZE = 4
DESTROY = 5
STORE = 6
+ RETRIEVE = 7
GET_PRINCIPAL = 8
GET_CRED_UUID_LIST = 9
GET_CRED_BY_UUID = 10
@@ -54,6 +55,7 @@ class KCMOpcodes(object):
class KRB5Errors(object):
+ KRB5_CC_NOTFOUND = -1765328243
KRB5_CC_END = -1765328242
KRB5_CC_NOSUPP = -1765328137
KRB5_FCC_NOFILE = -1765328189
@@ -86,11 +88,29 @@ def get_cache(name):
return cache
+def unpack_data(argbytes):
+ dlen, = struct.unpack('>L', argbytes[:4])
+ return argbytes[4:dlen+4], argbytes[dlen+4:]
+
+
def unmarshal_name(argbytes):
offset = argbytes.find(b'\0')
return argbytes[0:offset], argbytes[offset+1:]
+def unmarshal_princ(argbytes):
+ # Ignore the type at argbytes[0:4].
+ ncomps, = struct.unpack('>L', argbytes[4:8])
+ realm, rest = unpack_data(argbytes[8:])
+ comps = []
+ for i in range(ncomps):
+ comp, rest = unpack_data(rest)
+ comps.append(comp)
+ # Asssume no quoting is needed.
+ princ = b'/'.join(comps) + b'@' + realm
+ return princ, rest
+
+
def op_gen_new(argbytes):
# Does not actually check for uniqueness.
global next_unique
@@ -126,6 +146,22 @@ def op_store(argbytes):
return 0, b''
+def op_retrieve(argbytes):
+ name, rest = unmarshal_name(argbytes)
+ # Ignore the flags at rest[0:4] and the header at rest[4:8].
+ # Assume there are client and server creds in the tag and match
+ # only against them.
+ cprinc, rest = unmarshal_princ(rest[8:])
+ sprinc, rest = unmarshal_princ(rest)
+ cache = get_cache(name)
+ for cred in (cache.creds[u] for u in cache.cred_uuids):
+ cred_cprinc, rest = unmarshal_princ(cred)
+ cred_sprinc, rest = unmarshal_princ(rest)
+ if cred_cprinc == cprinc and cred_sprinc == sprinc:
+ return 0, cred
+ return KRB5Errors.KRB5_CC_NOTFOUND, b''
+
+
def op_get_principal(argbytes):
name, rest = unmarshal_name(argbytes)
cache = get_cache(name)
@@ -199,6 +235,7 @@ ophandlers = {
KCMOpcodes.INITIALIZE : op_initialize,
KCMOpcodes.DESTROY : op_destroy,
KCMOpcodes.STORE : op_store,
+ KCMOpcodes.RETRIEVE : op_retrieve,
KCMOpcodes.GET_PRINCIPAL : op_get_principal,
KCMOpcodes.GET_CRED_UUID_LIST : op_get_cred_uuid_list,
KCMOpcodes.GET_CRED_BY_UUID : op_get_cred_by_uuid,
@@ -243,10 +280,11 @@ def service_request(s):
return True
parser = optparse.OptionParser()
-parser.add_option('-c', '--credlist', action='store_true', dest='credlist',
- default=False, help='Support KCM_OP_GET_CRED_LIST')
+parser.add_option('-f', '--fallback', action='store_true', dest='fallback',
+ default=False, help='Do not support RETRIEVE/GET_CRED_LIST')
(options, args) = parser.parse_args()
-if not options.credlist:
+if options.fallback:
+ del ophandlers[KCMOpcodes.RETRIEVE]
del ophandlers[KCMOpcodes.GET_CRED_LIST]
server = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
diff --git a/src/tests/t_ccache.py b/src/tests/t_ccache.py
index 90040fb7b..6ea9fb969 100755
--- a/src/tests/t_ccache.py
+++ b/src/tests/t_ccache.py
@@ -25,7 +25,7 @@ from k5test import *
kcm_socket_path = os.path.join(os.getcwd(), 'testdir', 'kcm')
conf = {'libdefaults': {'kcm_socket': kcm_socket_path,
'kcm_mach_service': '-'}}
-realm = K5Realm(create_host=False, krb5_conf=conf)
+realm = K5Realm(krb5_conf=conf)
keyctl = which('keyctl')
out = realm.run([klist, '-c', 'KEYRING:process:abcd'], expected_code=1)
@@ -71,6 +71,11 @@ def collection_test(realm, ccname):
realm.kinit('alice', password('alice'))
realm.run([klist], expected_msg='Default principal: alice@')
realm.run([klist, '-A', '-s'])
+ realm.run([kvno, realm.host_princ], expected_msg = 'kvno = 1')
+ realm.run([kvno, realm.host_princ], expected_msg = 'kvno = 1')
+ out = realm.run([klist])
+ if out.count(realm.host_princ) != 1:
+ fail('Wrong number of service tickets in cache')
realm.run([kdestroy])
output = realm.run([klist], expected_code=1)
if 'No credentials cache' not in output and 'not found' not in output:
@@ -126,14 +131,14 @@ def collection_test(realm, ccname):
collection_test(realm, 'DIR:' + os.path.join(realm.testdir, 'cc'))
-# Test KCM without and with GET_CRED_LIST support.
+# Test KCM with and without RETRIEVE and GET_CRED_LIST support.
kcmserver_path = os.path.join(srctop, 'tests', 'kcmserver.py')
kcmd = realm.start_server([sys.executable, kcmserver_path, kcm_socket_path],
'starting...')
collection_test(realm, 'KCM:')
stop_daemon(kcmd)
os.remove(kcm_socket_path)
-realm.start_server([sys.executable, kcmserver_path, '-c', kcm_socket_path],
+realm.start_server([sys.executable, kcmserver_path, '-f', kcm_socket_path],
'starting...')
collection_test(realm, 'KCM:')