ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/gvpe/doc/gvpe.protocol.7
(Generate patch)

Comparing gvpe/doc/gvpe.protocol.7 (file contents):
Revision 1.9 by pcg, Mon Aug 11 16:02:16 2008 UTC vs.
Revision 1.10 by pcg, Mon Sep 1 06:06:11 2008 UTC

1.\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.32 1.\" Automatically generated by Pod::Man 2.16 (Pod::Simple 3.05)
2.\" 2.\"
3.\" Standard preamble: 3.\" Standard preamble:
4.\" ======================================================================== 4.\" ========================================================================
5.de Sh \" Subsection heading 5.de Sh \" Subsection heading
6.br 6.br
… …
46. ds PI \(*p 46. ds PI \(*p
47. ds L" `` 47. ds L" ``
48. ds R" '' 48. ds R" ''
49'br\} 49'br\}
50.\" 50.\"
51.\" Escape single quotes in literal strings from groff's Unicode transform.
52.ie \n(.g .ds Aq \(aq
53.el .ds Aq '
54.\"
51.\" If the F register is turned on, we'll generate index entries on stderr for 55.\" If the F register is turned on, we'll generate index entries on stderr for
52.\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index 56.\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index
53.\" entries marked with X<> in POD. Of course, you'll have to process the 57.\" entries marked with X<> in POD. Of course, you'll have to process the
54.\" output yourself in some meaningful fashion. 58.\" output yourself in some meaningful fashion.
55.if \nF \{\ 59.ie \nF \{\
56. de IX 60. de IX
57. tm Index:\\$1\t\\n%\t"\\$2" 61. tm Index:\\$1\t\\n%\t"\\$2"
58.. 62..
59. nr % 0 63. nr % 0
60. rr F 64. rr F
61.\} 65.\}
62.\" 66.el \{\
63.\" For nroff, turn off justification. Always turn off hyphenation; it makes 67. de IX
64.\" way too many mistakes in technical documents. 68..
65.hy 0 69.\}
66.if n .na
67.\" 70.\"
68.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2). 71.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
69.\" Fear. Run. Save yourself. No user-serviceable parts. 72.\" Fear. Run. Save yourself. No user-serviceable parts.
70. \" fudge factors for nroff and troff 73. \" fudge factors for nroff and troff
71.if n \{\ 74.if n \{\
… …
127.\} 130.\}
128.rm #[ #] #H #V #F C 131.rm #[ #] #H #V #F C
129.\" ======================================================================== 132.\" ========================================================================
130.\" 133.\"
131.IX Title "GVPE.PROTOCOL 7" 134.IX Title "GVPE.PROTOCOL 7"
132.TH GVPE.PROTOCOL 7 "2008-08-10" "2.2" "GNU Virtual Private Ethernet" 135.TH GVPE.PROTOCOL 7 "2008-09-01" "2.2" "GNU Virtual Private Ethernet"
136.\" For nroff, turn off justification. Always turn off hyphenation; it makes
137.\" way too many mistakes in technical documents.
138.if n .ad l
139.nh
133.SH "The GNU-VPE Protocols" 140.SH "The GNU-VPE Protocols"
134.IX Header "The GNU-VPE Protocols" 141.IX Header "The GNU-VPE Protocols"
135.SH "Overview" 142.SH "Overview"
136.IX Header "Overview" 143.IX Header "Overview"
137\&\s-1GVPE\s0 can make use of a number of protocols. One of them is the \s-1GNU\s0 \s-1VPE\s0 144\&\s-1GVPE\s0 can make use of a number of protocols. One of them is the \s-1GNU\s0 \s-1VPE\s0
… …
150The following sections describe each transport protocol in more 157The following sections describe each transport protocol in more
151detail. They are sorted by overhead/efficiency, the most efficient 158detail. They are sorted by overhead/efficiency, the most efficient
152transport is listed first: 159transport is listed first:
153.Sh "\s-1RAW\s0 \s-1IP\s0" 160.Sh "\s-1RAW\s0 \s-1IP\s0"
154.IX Subsection "RAW IP" 161.IX Subsection "RAW IP"
155This protocol is the best choice, performance\-wise, as the minimum 162This protocol is the best choice, performance-wise, as the minimum
156overhead per packet is only 38 bytes. 163overhead per packet is only 38 bytes.
157.PP 164.PP
158It works by sending the \s-1VPN\s0 payload using raw ip frames (using the 165It works by sending the \s-1VPN\s0 payload using raw \s-1IP\s0 frames (using the
159protocol set by \f(CW\*(C`ip\-proto\*(C'\fR). 166protocol set by \f(CW\*(C`ip\-proto\*(C'\fR).
160.PP 167.PP
161Using raw ip frames has the drawback that many firewalls block \*(L"unknown\*(R" 168Using raw \s-1IP\s0 frames has the drawback that many firewalls block \*(L"unknown\*(R"
162protocols, so this transport only works if you have full \s-1IP\s0 connectivity 169protocols, so this transport only works if you have full \s-1IP\s0 connectivity
163between nodes. 170between nodes.
164.Sh "\s-1ICMP\s0" 171.Sh "\s-1ICMP\s0"
165.IX Subsection "ICMP" 172.IX Subsection "ICMP"
166This protocol offers very low overhead (minimum 42 bytes), and can 173This protocol offers very low overhead (minimum 42 bytes), and can
167sometimes tunnel through firewalls when other protocols can not. 174sometimes tunnel through firewalls when other protocols can not.
168.PP 175.PP
169It works by prepending an \s-1ICMP\s0 header with type \f(CW\*(C`icmp\-type\*(C'\fR and a code 176It works by prepending an \s-1ICMP\s0 header with type \f(CW\*(C`icmp\-type\*(C'\fR and a code
170of \f(CW255\fR. The default \f(CW\*(C`icmp\-type\*(C'\fR is \f(CW\*(C`echo\-reply\*(C'\fR, so the resulting 177of \f(CW255\fR. The default \f(CW\*(C`icmp\-type\*(C'\fR is \f(CW\*(C`echo\-reply\*(C'\fR, so the resulting
171packets look like echo replies, which looks rather strange to network 178packets look like echo replies, which looks rather strange to network
172admins. 179administrators.
173.PP 180.PP
174This transport should only be used if other transports (i.e. raw ip) are 181This transport should only be used if other transports (i.e. raw \s-1IP\s0) are
175not available or undesirable (due to their overhead). 182not available or undesirable (due to their overhead).
176.Sh "\s-1UDP\s0" 183.Sh "\s-1UDP\s0"
177.IX Subsection "UDP" 184.IX Subsection "UDP"
178This is a good general choice for the transport protocol as \s-1UDP\s0 packets 185This is a good general choice for the transport protocol as \s-1UDP\s0 packets
179tunnel well through most firewalls and routers, and the overhead per 186tunnel well through most firewalls and routers, and the overhead per
… …
197It is an abuse of the usage a proxy was designed for, so make sure you are 204It is an abuse of the usage a proxy was designed for, so make sure you are
198allowed to use it for \s-1GVPE\s0. 205allowed to use it for \s-1GVPE\s0.
199.PP 206.PP
200This protocol also has server and client sides. If the \f(CW\*(C`tcp\-port\*(C'\fR is 207This protocol also has server and client sides. If the \f(CW\*(C`tcp\-port\*(C'\fR is
201set to zero, other nodes cannot connect to this node directly. If the 208set to zero, other nodes cannot connect to this node directly. If the
202\&\f(CW\*(C`tcp\-port\*(C'\fR is non\-zero, the node can act both as a client as well as a 209\&\f(CW\*(C`tcp\-port\*(C'\fR is non-zero, the node can act both as a client as well as a
203server. 210server.
204.Sh "\s-1DNS\s0" 211.Sh "\s-1DNS\s0"
205.IX Subsection "DNS" 212.IX Subsection "DNS"
206\&\fB\s-1WARNING:\s0\fR Parsing and generating \s-1DNS\s0 packets is rather tricky. The code 213\&\fB\s-1WARNING:\s0\fR Parsing and generating \s-1DNS\s0 packets is rather tricky. The code
207almost certainly contains buffer overflows and other, likely exploitable, 214almost certainly contains buffer overflows and other, likely exploitable,
… …
224and an \f(CW\*(C`NS\*(C'\fR record pointing to the \s-1GVPE\s0 server (as given by the 231and an \f(CW\*(C`NS\*(C'\fR record pointing to the \s-1GVPE\s0 server (as given by the
225\&\f(CW\*(C`dns\-hostname\*(C'\fR directive). 232\&\f(CW\*(C`dns\-hostname\*(C'\fR directive).
226.PP 233.PP
227The only good side of this protocol is that it can tunnel through most 234The only good side of this protocol is that it can tunnel through most
228firewalls mostly undetected, iff the local \s-1DNS\s0 server/forwarder is sane 235firewalls mostly undetected, iff the local \s-1DNS\s0 server/forwarder is sane
229(which is true for most routers, \s-1WLAN\s0 gateways and nameservers). 236(which is true for most routers, wireless \s-1LAN\s0 gateways and nameservers).
230.PP 237.PP
231Finetuning needs to be done by editing \f(CW\*(C`src/vpn_dns.C\*(C'\fR directly. 238Fine-tuning needs to be done by editing \f(CW\*(C`src/vpn_dns.C\*(C'\fR directly.
232.SH "PART 2: The GNU VPE protocol" 239.SH "PART 2: The GNU VPE protocol"
233.IX Header "PART 2: The GNU VPE protocol" 240.IX Header "PART 2: The GNU VPE protocol"
234This section, unfortunately, is not yet finished, although the protocol 241This section, unfortunately, is not yet finished, although the protocol
235is stable (until bugs in the cryptography are found, which will likely 242is stable (until bugs in the cryptography are found, which will likely
236completely change the following description). Nevertheless, it should give 243completely change the following description). Nevertheless, it should give
237you some overview over the protocol. 244you some overview over the protocol.
238.Sh "Anatomy of a \s-1VPN\s0 packet" 245.Sh "Anatomy of a \s-1VPN\s0 packet"
239.IX Subsection "Anatomy of a VPN packet" 246.IX Subsection "Anatomy of a VPN packet"
240The exact layout and field lengths of a \s-1VPN\s0 packet is determined at 247The exact layout and field lengths of a \s-1VPN\s0 packet is determined at
241compiletime and doesn't change. The same structure is used for all 248compile time and doesn't change. The same structure is used for all
242transort protocols, be it \s-1RAWIP\s0 or \s-1TCP\s0. 249transport protocols, be it \s-1RAWIP\s0 or \s-1TCP\s0.
243.PP 250.PP
244.Vb 3 251.Vb 3
245\& +\-\-\-\-\-\-+\-\-\-\-\-\-+\-\-\-\-\-\-\-\-+\-\-\-\-\-\-+ 252\& +\-\-\-\-\-\-+\-\-\-\-\-\-+\-\-\-\-\-\-\-\-+\-\-\-\-\-\-+
246\& | HMAC | TYPE | SRCDST | DATA | 253\& | HMAC | TYPE | SRCDST | DATA |
247\& +\-\-\-\-\-\-+\-\-\-\-\-\-+\-\-\-\-\-\-\-\-+\-\-\-\-\-\-+ 254\& +\-\-\-\-\-\-+\-\-\-\-\-\-+\-\-\-\-\-\-\-\-+\-\-\-\-\-\-+
… …
275initialization and starts at some random 31 bit value. \s-1VPE\s0 currently uses 282initialization and starts at some random 31 bit value. \s-1VPE\s0 currently uses
276a sliding window of 512 packets/sequence numbers to detect reordering, 283a sliding window of 512 packets/sequence numbers to detect reordering,
277duplication and replay attacks. 284duplication and replay attacks.
278.Sh "The authentication protocol" 285.Sh "The authentication protocol"
279.IX Subsection "The authentication protocol" 286.IX Subsection "The authentication protocol"
280Before hosts can exchange packets, they need to establish authenticity of 287Before nodes can exchange packets, they need to establish authenticity of
281the other side and a key. Every host has a private \s-1RSA\s0 key and the public 288the other side and a key. Every node has a private \s-1RSA\s0 key and the public
282\&\s-1RSA\s0 keys of all other hosts. 289\&\s-1RSA\s0 keys of all other nodes.
283.PP 290.PP
284A host establishes a simplex connection by sending the other host an 291A host establishes a simplex connection by sending the other node an
285\&\s-1RSA\s0 encrypted challenge containing a random challenge (consisting of 292\&\s-1RSA\s0 encrypted challenge containing a random challenge (consisting of
286the encryption key to use when sending packets, more random data and 293the encryption key to use when sending packets, more random data and
287\&\s-1PKCS1_OAEP\s0 padding) and a random 16 byte \*(L"challenge\-id\*(R" (used to detect 294\&\s-1PKCS1_OAEP\s0 padding) and a random 16 byte \*(L"challenge-id\*(R" (used to detect
288duplicate auth packets). The destination host will respond by replying 295duplicate auth packets). The destination node will respond by replying
289with an (unencrypted) \s-1RIPEMD160\s0 hash of the decrypted challenge, which 296with an (unencrypted) \s-1RIPEMD160\s0 hash of the decrypted challenge, which
290will authenticate that host. The destination host will also set the 297will authenticate that node. The destination node will also set the
291outgoing encryption parameters as given in the packet. 298outgoing encryption parameters as given in the packet.
292.PP 299.PP
293When the source host receives a correct auth reply (by verifying the 300When the source node receives a correct auth reply (by verifying the
294hash and the id, which will expire after 120 seconds), it will start to 301hash and the id, which will expire after 120 seconds), it will start to
295accept data packets from the destination host. 302accept data packets from the destination node.
296.PP 303.PP
297This means that a host can only initate a simplex connection, telling the 304This means that a node can only initiate a simplex connection, telling the
298other side the key it has to use when it sends packets. The challenge 305other side the key it has to use when it sends packets. The challenge
299reply is only used to set the current \s-1IP\s0 address of the other side and 306reply is only used to set the current \s-1IP\s0 address of the other side and
300protocol parameters. 307protocol parameters.
301.PP 308.PP
302This protocol is completely symmetric, so to be able to send packets the 309This protocol is completely symmetric, so to be able to send packets the
303destination host must send a challenge in the exact same way as already 310destination node must send a challenge in the exact same way as already
304described (so, in essence, two simplex connections are created per host 311described (so, in essence, two simplex connections are created per node
305pair). 312pair).
306.Sh "Retrying" 313.Sh "Retrying"
307.IX Subsection "Retrying" 314.IX Subsection "Retrying"
308When there is no response to an auth request, the host will send auth 315When there is no response to an auth request, the node will send auth
309requests in bursts with an exponential backoff. After some time it will 316requests in bursts with an exponential back-off. After some time it will
310resort to \s-1PING\s0 packets, which are very small (8 bytes + protocol header) 317resort to \s-1PING\s0 packets, which are very small (8 bytes + protocol header)
311and lightweight (no \s-1RSA\s0 operations required). A host that receives ping 318and lightweight (no \s-1RSA\s0 operations required). A node that receives ping
312requests from an unconnected peer will respond by trying to create a 319requests from an unconnected peer will respond by trying to create a
313connection. 320connection.
314.PP 321.PP
315In addition to the exponential backoff, there is a global rate-limit on 322In addition to the exponential back-off, there is a global rate-limit on
316a per-IP base. It allows long bursts but will limit total packet rate to 323a per-IP base. It allows long bursts but will limit total packet rate to
317something like one control packet every ten seconds, to avoid accidental 324something like one control packet every ten seconds, to avoid accidental
318floods due to protocol problems (like a \s-1RSA\s0 key file mismatch between two 325floods due to protocol problems (like a \s-1RSA\s0 key file mismatch between two
319hosts). 326nodes).
320.PP 327.PP
321The intervals between retries are limited by the \f(CW\*(C`max\-retry\*(C'\fR 328The intervals between retries are limited by the \f(CW\*(C`max\-retry\*(C'\fR
322configuration value. A node with \f(CW\*(C`connect\*(C'\fR = \f(CW\*(C`always\*(C'\fR will always retry, 329configuration value. A node with \f(CW\*(C`connect\*(C'\fR = \f(CW\*(C`always\*(C'\fR will always retry,
323a node with \f(CW\*(C`connect\*(C'\fR = \f(CW\*(C`ondemand\*(C'\fR will only try (and re\-try) to connect 330a node with \f(CW\*(C`connect\*(C'\fR = \f(CW\*(C`ondemand\*(C'\fR will only try (and re-try) to connect
324as long as there are packets in the queue, usually this limits the retry 331as long as there are packets in the queue, usually this limits the retry
325period to \f(CW\*(C`max\-ttl\*(C'\fR seconds. 332period to \f(CW\*(C`max\-ttl\*(C'\fR seconds.
326.PP 333.PP
327Sending packets over the \s-1VPN\s0 will reset the retry intervals as well, which 334Sending packets over the \s-1VPN\s0 will reset the retry intervals as well, which
328means as long as somebody is trying to send packets to a given node, \s-1GVPE\s0 335means as long as somebody is trying to send packets to a given node, \s-1GVPE\s0
… …
330.Sh "Routing and Protocol translation" 337.Sh "Routing and Protocol translation"
331.IX Subsection "Routing and Protocol translation" 338.IX Subsection "Routing and Protocol translation"
332The \s-1GVPE\s0 routing algorithm is easy: there isn't much routing to speak 339The \s-1GVPE\s0 routing algorithm is easy: there isn't much routing to speak
333of: When routing packets to another node, \s-1GVPE\s0 trues the following 340of: When routing packets to another node, \s-1GVPE\s0 trues the following
334options, in order: 341options, in order:
335.IP "If the two hosts should be able to reach each other directly (common protocol, port known), then \s-1GVPE\s0 will send the packet directly to the other node." 4 342.IP "If the two nodes should be able to reach each other directly (common protocol, port known), then \s-1GVPE\s0 will send the packet directly to the other node." 4
336.IX Item "If the two hosts should be able to reach each other directly (common protocol, port known), then GVPE will send the packet directly to the other node." 343.IX Item "If the two nodes should be able to reach each other directly (common protocol, port known), then GVPE will send the packet directly to the other node."
337.PD 0 344.PD 0
338.ie n .IP "If this isn't possible (e.g. because the node doesn't have a \*(C`hostname\*(C' or known port), but the nodes speak a common protocol and a router is available, then \s-1GVPE\s0 will ask a router to ""mediate"" between both nodes (see below)." 4 345.ie n .IP "If this isn't possible (e.g. because the node doesn't have a \*(C`hostname\*(C' or known port), but the nodes speak a common protocol and a router is available, then \s-1GVPE\s0 will ask a router to ""mediate"" between both nodes (see below)." 4
339.el .IP "If this isn't possible (e.g. because the node doesn't have a \f(CW\*(C`hostname\*(C'\fR or known port), but the nodes speak a common protocol and a router is available, then \s-1GVPE\s0 will ask a router to ``mediate'' between both nodes (see below)." 4 346.el .IP "If this isn't possible (e.g. because the node doesn't have a \f(CW\*(C`hostname\*(C'\fR or known port), but the nodes speak a common protocol and a router is available, then \s-1GVPE\s0 will ask a router to ``mediate'' between both nodes (see below)." 4
340.IX Item "If this isn't possible (e.g. because the node doesn't have a hostname or known port), but the nodes speak a common protocol and a router is available, then GVPE will ask a router to mediate between both nodes (see below)." 347.IX Item "If this isn't possible (e.g. because the node doesn't have a hostname or known port), but the nodes speak a common protocol and a router is available, then GVPE will ask a router to mediate between both nodes (see below)."
341.ie n .IP "If a direct connection isn't possible (no common protocols) or forbidden (\*(C`deny\-direct\*(C'\fR) and there are any routers, then \s-1GVPE\s0 will try to send packets to the router with the highest priority that is connected already \fIand is able (as specified by the config file) to connect directly to the target node." 4 348.ie n .IP "If a direct connection isn't possible (no common protocols) or forbidden (\*(C`deny\-direct\*(C'\fR) and there are any routers, then \s-1GVPE\s0 will try to send packets to the router with the highest priority that is connected already \fIand is able (as specified by the config file) to connect directly to the target node." 4
… …
351port number(s) to zero. It can declare other hosts as unreachable by using 358port number(s) to zero. It can declare other hosts as unreachable by using
352a config-file that disables all protocols for these other hosts. Another 359a config-file that disables all protocols for these other hosts. Another
353option is to disable all protocols on that host in the other config files. 360option is to disable all protocols on that host in the other config files.
354.PP 361.PP
355If two hosts cannot connect to each other because their \s-1IP\s0 address(es) 362If two hosts cannot connect to each other because their \s-1IP\s0 address(es)
356are not known (such as dialup hosts), one side will send a \fImediated\fR 363are not known (such as dial-up hosts), one side will send a \fImediated\fR
357connection request to a router (routers must be configured to act as 364connection request to a router (routers must be configured to act as
358routers!), which will send both the originating and the destination host 365routers!), which will send both the originating and the destination host
359a connection info request with protocol information and \s-1IP\s0 address of the 366a connection info request with protocol information and \s-1IP\s0 address of the
360other host (if known). Both hosts will then try to establish a direct 367other host (if known). Both hosts will then try to establish a direct
361connection to the other peer, which is usually possible even when both 368connection to the other peer, which is usually possible even when both

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines