| 1 | .\" -*-nroff-*- |
| 2 | .\". |
| 3 | .de hP |
| 4 | .IP |
| 5 | \h'-\w'\fB\\$1\ \fP'u'\fB\\$1\ \fP\c |
| 6 | .. |
| 7 | .de VS |
| 8 | .sp 1 |
| 9 | .RS |
| 10 | .nf |
| 11 | .ft B |
| 12 | .. |
| 13 | .de VE |
| 14 | .ft R |
| 15 | .fi |
| 16 | .RE |
| 17 | .sp 1 |
| 18 | .. |
| 19 | .ie t \{\ |
| 20 | . ds o \(bu |
| 21 | . ds ss \s8\u |
| 22 | . ds se \d\s0 |
| 23 | . if \n(.g \{\ |
| 24 | . fam P |
| 25 | . \} |
| 26 | .\} |
| 27 | .el \{\ |
| 28 | . ds o o |
| 29 | . ds ss ^ |
| 30 | . ds se |
| 31 | .\} |
| 32 | .TH tripe 8 "10 February 2001" "Straylight/Edgeware" "TrIPE: Trivial IP Encryption" |
| 33 | .SH "NAME" |
| 34 | tripe \- a simple VPN daemon |
| 35 | .SH "SYNOPSIS" |
| 36 | .B tripe |
| 37 | .RB [ \-D ] |
| 38 | .RB [ \-p |
| 39 | .IR port ] |
| 40 | .RB [ \-T |
| 41 | .IR trace-opts ] |
| 42 | .RB [ \-d |
| 43 | .IR dir ] |
| 44 | .RB [ \-a |
| 45 | .IR socket ] |
| 46 | .br |
| 47 | |
| 48 | .RB [ \-k |
| 49 | .IR priv-keyring ] |
| 50 | .RB [ \-K |
| 51 | .IR pub-keyring ] |
| 52 | .RB [ \-t |
| 53 | .IR key-tag ] |
| 54 | .SH "DESCRIPTION" |
| 55 | The |
| 56 | .B tripe |
| 57 | program is a server which can provide strong IP-level encryption and |
| 58 | authentication between two co-operating hosts. The program and its |
| 59 | protocol are deliberately very simple, to make analysing them easy and |
| 60 | to help build trust rapidly in the system. |
| 61 | .SS "Overview" |
| 62 | The |
| 63 | .B tripe |
| 64 | server manages a number of secure connections to other `peer' hosts. |
| 65 | Each daemon is given a private key of its own, and a file of public keys |
| 66 | for the peers with which it is meant to communicate. It is responsible |
| 67 | for negotiating sets of symmetric keys with its peers, and for |
| 68 | encrypting, encapsulating and sending IP packets to its peers, and |
| 69 | decrypting, checking and de-encapsulating packets it receives from |
| 70 | them. |
| 71 | .PP |
| 72 | When the server starts, it creates a Unix-domain socket on which it |
| 73 | listens for administration commands. It also logs warnings and |
| 74 | diagnostic information to the programs connected to its admin socket. |
| 75 | Clients connected to the socket can add new peers, and remove or find |
| 76 | out about existing peers. The textual protocol used to give the |
| 77 | .B tripe |
| 78 | server admin commands is described in |
| 79 | .BR tripe\-admin (5). |
| 80 | A client program |
| 81 | .BR tripectl (1) |
| 82 | is provided to allow commands to be sent to the server either |
| 83 | interactively or by simple scripts. |
| 84 | .SS "Command-line arguments" |
| 85 | If not given any command-line arguments, |
| 86 | .B tripe |
| 87 | will initialize by following these steps: |
| 88 | .hP \*o |
| 89 | It changes directory to |
| 90 | .BR /var/lib/tripe . |
| 91 | .hP \*o |
| 92 | It acquires a UDP socket with an arbitrary kernel-selected port number. |
| 93 | It will use this socket to send and receive all communications with its |
| 94 | peer servers. The port chosen may be discovered by means of the |
| 95 | .B PORT |
| 96 | admin command (see |
| 97 | .BR tripe\-admin (5)). |
| 98 | .hP \*o |
| 99 | It loads the private key with the tag or type name |
| 100 | .B tripe\-dh |
| 101 | from the Catacomb-format file |
| 102 | .BR keyring , |
| 103 | and loads the file |
| 104 | .B keyring.pub |
| 105 | ready for extracting the public keys of peers as they're introduced. |
| 106 | (The format of these files is described in |
| 107 | .BR keyring (5). |
| 108 | They are maintained using the program |
| 109 | .BR key (1) |
| 110 | provided with the Catacomb distribution.) |
| 111 | .hP \*o |
| 112 | It creates and listens to the Unix-domain socket |
| 113 | .BR tripesock . |
| 114 | .PP |
| 115 | Following this, the server enters its main loop, accepting admin |
| 116 | connections and obeying any administrative commands, and communicating |
| 117 | with peers. It also treats its standard input and standard output |
| 118 | streams as an admin connection, reading commands from standard input and |
| 119 | writing responses and diagnostics messages to standard output. |
| 120 | .PP |
| 121 | Much of this behaviour may be altered by giving |
| 122 | .B tripe |
| 123 | suitable command-line options: |
| 124 | .TP |
| 125 | .B "\-h, \-\-help" |
| 126 | Writes a brief description of the command-line options available to |
| 127 | standard output and exits with status 0. |
| 128 | .TP |
| 129 | .B "\-v, \-\-version" |
| 130 | Writes |
| 131 | .BR tripe 's |
| 132 | version number to standard output and exits with status 0. |
| 133 | .TP |
| 134 | .B "\-u, \-\-usage" |
| 135 | Writes a brief usage summary to standard output and exits with status 0. |
| 136 | .TP |
| 137 | .B "\-D, \-\-daemon" |
| 138 | Dissociates from its terminal and starts running in the background after |
| 139 | completing the initialization procedure described above. If running as |
| 140 | a daemon, |
| 141 | .B tripe |
| 142 | will not read commands from standard input or write diagnostics to |
| 143 | standard output. A better way to start |
| 144 | .B tripe |
| 145 | in the background is with |
| 146 | .BR tripectl (1). |
| 147 | .TP |
| 148 | .BI "\-d, \-\-directory=" dir |
| 149 | Makes |
| 150 | .I dir |
| 151 | the current directory, instead of |
| 152 | .BR /var/lib/tripe . |
| 153 | Give a current directory of |
| 154 | .B . |
| 155 | if you don't want it to change directory at all. |
| 156 | .TP |
| 157 | .BI "\-p, \-\-port=" port |
| 158 | Use the specified UDP port for all communications with peers, rather |
| 159 | than an arbitarary kernel-assigned port. |
| 160 | .TP |
| 161 | .BI "\-k, \-\-priv\-keyring=" file |
| 162 | Reads the private key from |
| 163 | .I file |
| 164 | rather than the default |
| 165 | .BR keyring . |
| 166 | .TP |
| 167 | .BI "\-K, \-\-pub\-keyring=" file |
| 168 | Reads public keys from |
| 169 | .I file |
| 170 | rather than the default |
| 171 | .BR keyring.pub . |
| 172 | This can be the same as the private keyring, but that's not recommended. |
| 173 | .TP |
| 174 | .BI "\-t, \-\-tag=" tag |
| 175 | Uses the private key whose tag or type is |
| 176 | .I tag |
| 177 | rather than the default |
| 178 | .BR tripe\-dh . |
| 179 | .TP |
| 180 | .BI "\-a, \-\-admin\-socket=" socket |
| 181 | Accept admin connections to a Unix-domain socket named |
| 182 | .I socket |
| 183 | rather than the default |
| 184 | .BR tripesock . |
| 185 | .TP |
| 186 | .BI "\-T, \-\-trace=" trace-opts |
| 187 | Allows the enabling or disabling of various internal diagnostics. See |
| 188 | below for the list of options. |
| 189 | .SS "Setting up a VPN with tripe" |
| 190 | The |
| 191 | .B tripe |
| 192 | server identifies peers by name. While it's |
| 193 | .I possible |
| 194 | for each host to maintain its own naming system for its peers, this is |
| 195 | likely to lead to confusion, and it's more sensible to organize a naming |
| 196 | system that works everywhere. How you manage this naming is up to you. |
| 197 | The only restriction on the format of names is that they must be valid |
| 198 | Catacomb key tags, since this is how |
| 199 | .B tripe |
| 200 | identifies which public key to use for a particular peer: they may not |
| 201 | contain whitespace characters, or a colon |
| 202 | .RB ` : ' |
| 203 | or dot |
| 204 | .RB ` . ', |
| 205 | .PP |
| 206 | Allocating IP addresses for VPNs can get quite complicated. I'll |
| 207 | attempt to illustrate with a relatively simple example. Our objective |
| 208 | will be to set up a virtual private network between two sites of |
| 209 | .BR example.com . |
| 210 | The two sites are using distinct IP address ranges from the private |
| 211 | address space described in RFC1918: site A is using addresses from |
| 212 | 10.0.1.0/24 and site B is using 10.0.2.0/24. Each site has a gateway |
| 213 | host set up with both an address on the site's private network, and an |
| 214 | externally-routable address from the public IP address space. Site A's |
| 215 | gateway machine, |
| 216 | .BR alice , |
| 217 | has the addresses 10.0.1.1 and 200.0.1.1; site B's gateway is |
| 218 | .B bob |
| 219 | and has addresses 10.0.2.1 and 200.0.2.1. |
| 220 | .PP |
| 221 | This isn't quite complicated enough. Each of |
| 222 | .B alice |
| 223 | and |
| 224 | .B bob |
| 225 | needs an extra IP address which we'll use when setting up the |
| 226 | point-to-point link. These addresses need to be routable, at least |
| 227 | within the virtual private network: unfortunately, you can't just use |
| 228 | the same pair everywhere. We'll assign |
| 229 | .B alice |
| 230 | the point-to-point address 192.168.0.1, and |
| 231 | .B bob |
| 232 | the address 192.168.0.2. |
| 233 | .hP 1. |
| 234 | Install |
| 235 | .B tripe |
| 236 | on both of the gateway hosts. Create the directory |
| 237 | .BR /var/lib/tripe . |
| 238 | .hP 2. |
| 239 | On |
| 240 | .BR alice , |
| 241 | make |
| 242 | .B /var/lib/tripe |
| 243 | the current directory and generate a Diffie-Hellman group: |
| 244 | .RS |
| 245 | .VS |
| 246 | key add \-adh\-param \-LS \-b2048 \-B256 \e |
| 247 | \-eforever \-tparam tripe\-dh\-param |
| 248 | .VE |
| 249 | (See |
| 250 | .BR key (1) |
| 251 | from the Catacomb distribution for details about the |
| 252 | .B key |
| 253 | command.) Also generate a private key for |
| 254 | .BR alice : |
| 255 | .VS |
| 256 | key add \-adh \-pparam \-talice \e |
| 257 | \-e"now + 1 year" tripe\-dh |
| 258 | .VE |
| 259 | Extract the group parameters and |
| 260 | .BR alice 's |
| 261 | public key to |
| 262 | .I separate |
| 263 | files, and put the public key in |
| 264 | .BR keyring.pub : |
| 265 | .VS |
| 266 | key extract param param |
| 267 | key extract \-f\-secret alice alice.pub |
| 268 | key \-kkeyring.pub merge alice.pub |
| 269 | .VE |
| 270 | Send the files |
| 271 | .B param |
| 272 | and |
| 273 | .B alice.pub |
| 274 | to |
| 275 | .B bob |
| 276 | in some secure way (e.g., in PGP-signed email, or by using SSH), so that |
| 277 | you can be sure they've not been altered in transit. |
| 278 | .RE |
| 279 | .hP 3. |
| 280 | On |
| 281 | .B bob |
| 282 | now, make |
| 283 | .B /var/lib/tripe |
| 284 | the current directory, and import the key material from |
| 285 | .BR alice : |
| 286 | .RS |
| 287 | .VS |
| 288 | key merge param |
| 289 | key \-kkeyring.pub merge alice.pub |
| 290 | .VE |
| 291 | Generate a private key for |
| 292 | .B bob |
| 293 | and extract the public half, as before: |
| 294 | .VS |
| 295 | key add \-adh \-pparam \-tbob \e |
| 296 | \-e"now + 1 year" tripe\-dh |
| 297 | key extract \-f\-secret bob bob.pub |
| 298 | key \-kkeyring.pub merge bob.pub |
| 299 | .VE |
| 300 | and send |
| 301 | .B bob.pub |
| 302 | back to |
| 303 | .B alice |
| 304 | using some secure method. |
| 305 | .RE |
| 306 | .hP 4 |
| 307 | On |
| 308 | .BR alice , |
| 309 | merge |
| 310 | .B bob 's |
| 311 | key into the public keyring. Now, on each host, run |
| 312 | .RS |
| 313 | .VS |
| 314 | key \-kkeyring.pub fingerprint |
| 315 | .VE |
| 316 | and check that the hashes match. If the two sites have separate |
| 317 | administrators, they should read the hashes to each other over the |
| 318 | telephone (assuming that they can recognize each other's voices). |
| 319 | .RE |
| 320 | .hP 5. |
| 321 | Start the |
| 322 | .B tripe |
| 323 | servers up. Run |
| 324 | .RS |
| 325 | .VS |
| 326 | tripectl \-slD \-S\-P23169 |
| 327 | .VE |
| 328 | on each of |
| 329 | .B alice |
| 330 | and |
| 331 | .BR bob . |
| 332 | (The |
| 333 | .RB ` \-P23169 ' |
| 334 | forces the server to use UDP port 23169: use some other number if 23169 |
| 335 | is inappropriate for your requirements. I chose it by reducing the |
| 336 | RIPEMD160 hash of |
| 337 | .RB ` tripe\-port\-number\e0 ' |
| 338 | modulo 2\*(ss16\*(se.) |
| 339 | .RE |
| 340 | .hP 6. |
| 341 | To get |
| 342 | .B alice |
| 343 | talking to |
| 344 | .BR bob , |
| 345 | run this shell script (or one like it): |
| 346 | .RS |
| 347 | .VS |
| 348 | #! /bin/sh |
| 349 | |
| 350 | tripectl add bob 200.0.2.1 23169 |
| 351 | ifname=`tripectl ifname bob` |
| 352 | ifconfig $ifname \e |
| 353 | 192.168.0.1 \e |
| 354 | pointopoint 192.168.0.2 |
| 355 | route add -net \e |
| 356 | 10.0.2.0 netmask 255.255.255.0 \e |
| 357 | gw 192.168.0.2 |
| 358 | .VE |
| 359 | Read |
| 360 | .BR ifconfig (8) |
| 361 | and |
| 362 | .BR route (8) |
| 363 | to find out about your system's variants of these commands. The |
| 364 | versions shown above assume a Linux system. |
| 365 | Run a similar script on |
| 366 | .BR bob , |
| 367 | to tell its |
| 368 | .B tripe |
| 369 | server to talk to |
| 370 | .BR alice . |
| 371 | .RE |
| 372 | .hP 7. |
| 373 | Congratulations. The two servers will exchange keys and begin sending |
| 374 | packets almost immediately. You've set up a virtual private network. |
| 375 | .SS "About the name" |
| 376 | The program's name is |
| 377 | .BR tripe , |
| 378 | all in lower-case. The name of the protocol it uses is `TrIPE', with |
| 379 | four capital letters and one lower-case. The name stands for `Trivial |
| 380 | IP Encryption'. |
| 381 | .SH "BUGS" |
| 382 | The code hasn't been audited. It may contain security bugs. If you |
| 383 | find one, please inform the author |
| 384 | .IR immediately . |
| 385 | .SH "SEE ALSO" |
| 386 | .BR key (1), |
| 387 | .BR tripectl (1), |
| 388 | .BR tripe\-admin (5). |
| 389 | .PP |
| 390 | .IR "The Trivial IP Encryption Protocol" , |
| 391 | .IR "The Wrestlers Protocol" . |
| 392 | .SH "AUTHOR" |
| 393 | Mark Wooding, <mdw@nsict.org> |