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1 | 28cc354f | Iustin Pop | Security in Ganeti |
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2 | 6884c0ca | Iustin Pop | ================== |
3 | 28cc354f | Iustin Pop | |
4 | 3397d13e | Michael Hanselmann | Documents Ganeti version 2.6 |
5 | 3397d13e | Michael Hanselmann | |
6 | 28cc354f | Iustin Pop | Ganeti was developed to run on internal, trusted systems. As such, the |
7 | 28cc354f | Iustin Pop | security model is all-or-nothing. |
8 | 28cc354f | Iustin Pop | |
9 | 3397d13e | Michael Hanselmann | Up to version 2.3 all Ganeti code ran as root. Since version 2.4 it is |
10 | 3397d13e | Michael Hanselmann | possible to run all daemons except the node daemon as non-root users by |
11 | 3397d13e | Michael Hanselmann | specifying user names and groups at build time. The node daemon |
12 | 3397d13e | Michael Hanselmann | continues to require root privileges to create logical volumes, DRBD |
13 | 3397d13e | Michael Hanselmann | devices, start instances, etc. Cluster commands can be run as root or by |
14 | 3397d13e | Michael Hanselmann | users in a group specified at build time. |
15 | 28cc354f | Iustin Pop | |
16 | 28cc354f | Iustin Pop | Host issues |
17 | 28cc354f | Iustin Pop | ----------- |
18 | 28cc354f | Iustin Pop | |
19 | 7faf5110 | Michael Hanselmann | For a host on which the Ganeti software has been installed, but not |
20 | 7faf5110 | Michael Hanselmann | joined to a cluster, there are no changes to the system. |
21 | 28cc354f | Iustin Pop | |
22 | 28cc354f | Iustin Pop | For a host that has been joined to the cluster, there are very important |
23 | 28cc354f | Iustin Pop | changes: |
24 | 6884c0ca | Iustin Pop | |
25 | 6884c0ca | Iustin Pop | - The host will have its SSH host key replaced with the one of the |
26 | 6884c0ca | Iustin Pop | cluster (which is the one the initial node had at the cluster |
27 | 6884c0ca | Iustin Pop | creation) |
28 | 3397d13e | Michael Hanselmann | - A new public key will be added to root's ``authorized_keys`` file, |
29 | 6884c0ca | Iustin Pop | granting root access to all nodes of the cluster. The private part of |
30 | 6884c0ca | Iustin Pop | the key is also distributed to all nodes. Old files are renamed. |
31 | 6884c0ca | Iustin Pop | - Communication between nodes is encrypted using SSL/TLS. A common key |
32 | 6884c0ca | Iustin Pop | and certificate combo is shared between all nodes of the cluster. At |
33 | 6884c0ca | Iustin Pop | this time, no CA is used. |
34 | 6884c0ca | Iustin Pop | - The Ganeti node daemon will accept RPC requests from any host within |
35 | 6884c0ca | Iustin Pop | the cluster with the correct certificate, and the operations it will |
36 | 6884c0ca | Iustin Pop | do as a result of these requests are: |
37 | 6884c0ca | Iustin Pop | |
38 | 3397d13e | Michael Hanselmann | - running commands under the ``/etc/ganeti/hooks`` directory |
39 | 6884c0ca | Iustin Pop | - creating DRBD disks between it and the IP it has been told |
40 | 6884c0ca | Iustin Pop | - overwrite a defined list of files on the host |
41 | 28cc354f | Iustin Pop | |
42 | 28cc354f | Iustin Pop | As you can see, as soon as a node is joined, it becomes equal to all |
43 | 28cc354f | Iustin Pop | other nodes in the cluster, and the security of the cluster is |
44 | 28cc354f | Iustin Pop | determined by the weakest node. |
45 | 28cc354f | Iustin Pop | |
46 | 3397d13e | Michael Hanselmann | Note that only the SSH key will allow other machines to run any command |
47 | 3397d13e | Michael Hanselmann | on this node; the RPC method will run only: |
48 | 6884c0ca | Iustin Pop | |
49 | 6884c0ca | Iustin Pop | - well defined commands to create, remove, activate logical volumes, |
50 | 6884c0ca | Iustin Pop | drbd devices, start/stop instances, etc; |
51 | 3397d13e | Michael Hanselmann | - run well-defined SSH commands on other nodes in the cluster |
52 | 3397d13e | Michael Hanselmann | - scripts under the ``/etc/ganeti/hooks`` directory |
53 | 28cc354f | Iustin Pop | |
54 | 28cc354f | Iustin Pop | It is therefore important to make sure that the contents of the |
55 | 3397d13e | Michael Hanselmann | ``/etc/ganeti/hooks`` directory is supervised and only trusted sources |
56 | 3397d13e | Michael Hanselmann | can populate it. |
57 | 28cc354f | Iustin Pop | |
58 | 28cc354f | Iustin Pop | Cluster issues |
59 | 28cc354f | Iustin Pop | -------------- |
60 | 28cc354f | Iustin Pop | |
61 | 3397d13e | Michael Hanselmann | As mentioned above, there are multiple ways of communication between |
62 | 3397d13e | Michael Hanselmann | cluster nodes: |
63 | 6884c0ca | Iustin Pop | |
64 | 6884c0ca | Iustin Pop | - SSH-based, for high-volume traffic like image dumps or for low-level |
65 | 6884c0ca | Iustin Pop | command, e.g. restarting the Ganeti node daemon |
66 | 6884c0ca | Iustin Pop | - RPC communication between master and nodes |
67 | 6884c0ca | Iustin Pop | - DRBD real-time disk replication traffic |
68 | 28cc354f | Iustin Pop | |
69 | 4fbe765c | Michael Hanselmann | The SSH traffic is protected (after the initial login to a new node) by |
70 | 4fbe765c | Michael Hanselmann | the cluster-wide shared SSH key. |
71 | 28cc354f | Iustin Pop | |
72 | 7faf5110 | Michael Hanselmann | RPC communication between the master and nodes is protected using |
73 | 7faf5110 | Michael Hanselmann | SSL/TLS encryption. Both the client and the server must have the |
74 | 7faf5110 | Michael Hanselmann | cluster-wide shared SSL/TLS certificate and verify it when establishing |
75 | 7faf5110 | Michael Hanselmann | the connection by comparing fingerprints. We decided not to use a CA to |
76 | 7faf5110 | Michael Hanselmann | simplify the key handling. |
77 | 28cc354f | Iustin Pop | |
78 | 6884c0ca | Iustin Pop | The DRBD traffic is not protected by encryption, as DRBD does not |
79 | 6884c0ca | Iustin Pop | support this. It's therefore recommended to implement host-level |
80 | 888891c7 | Michael Hanselmann | firewalling or to use a separate range of IP addresses for the DRBD |
81 | 3397d13e | Michael Hanselmann | traffic (this is supported in Ganeti through the use of a secondary |
82 | 3397d13e | Michael Hanselmann | interface) which is not routed outside the cluster. DRBD connections are |
83 | 3397d13e | Michael Hanselmann | protected from erroneous connections to other machines (as may happen |
84 | 3397d13e | Michael Hanselmann | due to software issues), and from accepting connections from other |
85 | 3397d13e | Michael Hanselmann | machines, by using a shared secret, exchanged via RPC requests from the |
86 | 3397d13e | Michael Hanselmann | master to the nodes when configuring the device. |
87 | 6884c0ca | Iustin Pop | |
88 | 6884c0ca | Iustin Pop | Master daemon |
89 | 6884c0ca | Iustin Pop | ------------- |
90 | 6884c0ca | Iustin Pop | |
91 | 3397d13e | Michael Hanselmann | The command-line tools to master daemon communication is done via a |
92 | 3397d13e | Michael Hanselmann | UNIX socket, whose permissions are reset to ``0660`` after listening but |
93 | 7faf5110 | Michael Hanselmann | before serving requests. This permission-based protection is documented |
94 | 7faf5110 | Michael Hanselmann | and works on Linux, but is not-portable; however, Ganeti doesn't work on |
95 | 7faf5110 | Michael Hanselmann | non-Linux system at the moment. |
96 | 4fbe765c | Michael Hanselmann | |
97 | 4fbe765c | Michael Hanselmann | Remote API |
98 | 4fbe765c | Michael Hanselmann | ---------- |
99 | 4fbe765c | Michael Hanselmann | |
100 | 7faf5110 | Michael Hanselmann | Starting with Ganeti 2.0, Remote API traffic is encrypted using SSL/TLS |
101 | f1d243bd | Michael Hanselmann | by default. It supports Basic authentication as per :rfc:`2617`. Users |
102 | f1d243bd | Michael Hanselmann | can be granted different capabilities. Details can be found in the |
103 | f1d243bd | Michael Hanselmann | :ref:`RAPI documentation <rapi-users>`. |
104 | 4fbe765c | Michael Hanselmann | |
105 | 7faf5110 | Michael Hanselmann | Paths for certificate, private key and CA files required for SSL/TLS |
106 | 7faf5110 | Michael Hanselmann | will be set at source configure time. Symlinks or command line |
107 | 7faf5110 | Michael Hanselmann | parameters may be used to use different files. |
108 | 558fd122 | Michael Hanselmann | |
109 | 5b2069a9 | Michael Hanselmann | Inter-cluster instance moves |
110 | 5b2069a9 | Michael Hanselmann | ---------------------------- |
111 | 5b2069a9 | Michael Hanselmann | |
112 | 5b2069a9 | Michael Hanselmann | To move instances between clusters, different clusters must be able to |
113 | 5b2069a9 | Michael Hanselmann | communicate with each other over a secure channel. Up to and including |
114 | 5b2069a9 | Michael Hanselmann | Ganeti 2.1, clusters were self-contained entities and had no knowledge |
115 | 5b2069a9 | Michael Hanselmann | of other clusters. With Ganeti 2.2, clusters can exchange data if tokens |
116 | 5b2069a9 | Michael Hanselmann | (an encryption certificate) was exchanged by a trusted third party |
117 | 5b2069a9 | Michael Hanselmann | before. |
118 | 5b2069a9 | Michael Hanselmann | |
119 | 4e9dcb8a | Guido Trotter | KVM Security |
120 | 4e9dcb8a | Guido Trotter | ------------ |
121 | 4e9dcb8a | Guido Trotter | |
122 | 4e9dcb8a | Guido Trotter | When running KVM instances under Ganeti three security models ara |
123 | 3397d13e | Michael Hanselmann | available: "none", "user" and "pool". |
124 | 4e9dcb8a | Guido Trotter | |
125 | 3397d13e | Michael Hanselmann | Under security model "none" instances run by default as root. This means |
126 | 4e9dcb8a | Guido Trotter | that, if an instance gets jail broken, it will be able to own the host |
127 | 4e9dcb8a | Guido Trotter | node, and thus the ganeti cluster. This is the default model, and the |
128 | 4e9dcb8a | Guido Trotter | only one available before Ganeti 2.1.2. |
129 | 4e9dcb8a | Guido Trotter | |
130 | 3397d13e | Michael Hanselmann | Under security model "user" an instance is run as the user specified by |
131 | 3397d13e | Michael Hanselmann | the hypervisor parameter "security_domain". This makes it easy to run |
132 | f7b769b1 | Iustin Pop | all instances as non privileged users, and allows one to manually |
133 | f7b769b1 | Iustin Pop | allocate specific users to specific instances or sets of instances. If |
134 | f7b769b1 | Iustin Pop | the specified user doesn't have permissions a jail broken instance will |
135 | f7b769b1 | Iustin Pop | need some local privilege escalation before being able to take over the |
136 | f7b769b1 | Iustin Pop | node and the cluster. It's possible though for a jail broken instance to |
137 | 4e9dcb8a | Guido Trotter | affect other ones running under the same user. |
138 | 4e9dcb8a | Guido Trotter | |
139 | 3397d13e | Michael Hanselmann | Under security model "pool" a global cluster-level uid pool is used to |
140 | 4e9dcb8a | Guido Trotter | start each instance on the same node under a different user. The uids in |
141 | 4e9dcb8a | Guido Trotter | the cluster pool can be set with ``gnt-cluster init`` and ``gnt-cluster |
142 | 4e9dcb8a | Guido Trotter | modify``, and must correspond to existing users on all nodes. Ganeti |
143 | 4e9dcb8a | Guido Trotter | will then allocate one to each instance, as needed. This way a jail |
144 | 4e9dcb8a | Guido Trotter | broken instance won't be able to affect any other. Since the users are |
145 | 4e9dcb8a | Guido Trotter | handed out by ganeti in a per-node randomized way, in this mode there is |
146 | 4e9dcb8a | Guido Trotter | no way to make sure a particular instance is always run as a certain |
147 | 3397d13e | Michael Hanselmann | user. Use mode "user" for that. |
148 | 4e9dcb8a | Guido Trotter | |
149 | 4e9dcb8a | Guido Trotter | In addition to these precautions, if you want to avoid instances sending |
150 | 4e9dcb8a | Guido Trotter | traffic on your node network, you can use an iptables rule such as:: |
151 | 4e9dcb8a | Guido Trotter | |
152 | 4e9dcb8a | Guido Trotter | iptables -A OUTPUT -m owner --uid-owner <uid>[-<uid>] -j LOG \ |
153 | 4e9dcb8a | Guido Trotter | --log-prefix "ganeti uid pool user network traffic" |
154 | 4e9dcb8a | Guido Trotter | iptables -A OUTPUT -m owner --uid-owner <uid>[-<uid>] -j DROP |
155 | 4e9dcb8a | Guido Trotter | |
156 | 4e9dcb8a | Guido Trotter | This won't affect regular instance traffic (that comes out of the tapX |
157 | 4e9dcb8a | Guido Trotter | allocated to the instance, and can be filtered or subject to appropriate |
158 | 4e9dcb8a | Guido Trotter | policy routes) but will stop any user generated traffic that might come |
159 | 4e9dcb8a | Guido Trotter | from a jailbroken instance. |
160 | 4e9dcb8a | Guido Trotter | |
161 | 558fd122 | Michael Hanselmann | .. vim: set textwidth=72 : |
162 | c71a1a3d | Iustin Pop | .. Local Variables: |
163 | c71a1a3d | Iustin Pop | .. mode: rst |
164 | c71a1a3d | Iustin Pop | .. fill-column: 72 |
165 | c71a1a3d | Iustin Pop | .. End: |