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| 129 | .\" ======================================================================== |
| 130 | .\" |
| 131 | .IX Title "S_CLIENT 1" |
| 132 | .TH S_CLIENT 1 "2006-11-19" "0.9.8d" "OpenSSL" |
| 133 | .SH "NAME" |
| 134 | s_client \- SSL/TLS client program |
| 135 | .SH "SYNOPSIS" |
| 136 | .IX Header "SYNOPSIS" |
| 137 | \&\fBopenssl\fR \fBs_client\fR |
| 138 | [\fB\-connect host:port\fR] |
| 139 | [\fB\-verify depth\fR] |
| 140 | [\fB\-cert filename\fR] |
| 141 | [\fB\-certform DER|PEM\fR] |
| 142 | [\fB\-key filename\fR] |
| 143 | [\fB\-keyform DER|PEM\fR] |
| 144 | [\fB\-pass arg\fR] |
| 145 | [\fB\-CApath directory\fR] |
| 146 | [\fB\-CAfile filename\fR] |
| 147 | [\fB\-reconnect\fR] |
| 148 | [\fB\-pause\fR] |
| 149 | [\fB\-showcerts\fR] |
| 150 | [\fB\-debug\fR] |
| 151 | [\fB\-msg\fR] |
| 152 | [\fB\-nbio_test\fR] |
| 153 | [\fB\-state\fR] |
| 154 | [\fB\-nbio\fR] |
| 155 | [\fB\-crlf\fR] |
| 156 | [\fB\-ign_eof\fR] |
| 157 | [\fB\-quiet\fR] |
| 158 | [\fB\-ssl2\fR] |
| 159 | [\fB\-ssl3\fR] |
| 160 | [\fB\-tls1\fR] |
| 161 | [\fB\-no_ssl2\fR] |
| 162 | [\fB\-no_ssl3\fR] |
| 163 | [\fB\-no_tls1\fR] |
| 164 | [\fB\-bugs\fR] |
| 165 | [\fB\-cipher cipherlist\fR] |
| 166 | [\fB\-starttls protocol\fR] |
| 167 | [\fB\-engine id\fR] |
| 168 | [\fB\-rand file(s)\fR] |
| 169 | .SH "DESCRIPTION" |
| 170 | .IX Header "DESCRIPTION" |
| 171 | The \fBs_client\fR command implements a generic \s-1SSL/TLS\s0 client which connects |
| 172 | to a remote host using \s-1SSL/TLS\s0. It is a \fIvery\fR useful diagnostic tool for |
| 173 | \&\s-1SSL\s0 servers. |
| 174 | .SH "OPTIONS" |
| 175 | .IX Header "OPTIONS" |
| 176 | .IP "\fB\-connect host:port\fR" 4 |
| 177 | .IX Item "-connect host:port" |
| 178 | This specifies the host and optional port to connect to. If not specified |
| 179 | then an attempt is made to connect to the local host on port 4433. |
| 180 | .IP "\fB\-cert certname\fR" 4 |
| 181 | .IX Item "-cert certname" |
| 182 | The certificate to use, if one is requested by the server. The default is |
| 183 | not to use a certificate. |
| 184 | .IP "\fB\-certform format\fR" 4 |
| 185 | .IX Item "-certform format" |
| 186 | The certificate format to use: \s-1DER\s0 or \s-1PEM\s0. \s-1PEM\s0 is the default. |
| 187 | .IP "\fB\-key keyfile\fR" 4 |
| 188 | .IX Item "-key keyfile" |
| 189 | The private key to use. If not specified then the certificate file will |
| 190 | be used. |
| 191 | .IP "\fB\-keyform format\fR" 4 |
| 192 | .IX Item "-keyform format" |
| 193 | The private format to use: \s-1DER\s0 or \s-1PEM\s0. \s-1PEM\s0 is the default. |
| 194 | .IP "\fB\-pass arg\fR" 4 |
| 195 | .IX Item "-pass arg" |
| 196 | the private key password source. For more information about the format of \fBarg\fR |
| 197 | see the \fB\s-1PASS\s0 \s-1PHRASE\s0 \s-1ARGUMENTS\s0\fR section in \fIopenssl\fR\|(1). |
| 198 | .IP "\fB\-verify depth\fR" 4 |
| 199 | .IX Item "-verify depth" |
| 200 | The verify depth to use. This specifies the maximum length of the |
| 201 | server certificate chain and turns on server certificate verification. |
| 202 | Currently the verify operation continues after errors so all the problems |
| 203 | with a certificate chain can be seen. As a side effect the connection |
| 204 | will never fail due to a server certificate verify failure. |
| 205 | .IP "\fB\-CApath directory\fR" 4 |
| 206 | .IX Item "-CApath directory" |
| 207 | The directory to use for server certificate verification. This directory |
| 208 | must be in \*(L"hash format\*(R", see \fBverify\fR for more information. These are |
| 209 | also used when building the client certificate chain. |
| 210 | .IP "\fB\-CAfile file\fR" 4 |
| 211 | .IX Item "-CAfile file" |
| 212 | A file containing trusted certificates to use during server authentication |
| 213 | and to use when attempting to build the client certificate chain. |
| 214 | .IP "\fB\-reconnect\fR" 4 |
| 215 | .IX Item "-reconnect" |
| 216 | reconnects to the same server 5 times using the same session \s-1ID\s0, this can |
| 217 | be used as a test that session caching is working. |
| 218 | .IP "\fB\-pause\fR" 4 |
| 219 | .IX Item "-pause" |
| 220 | pauses 1 second between each read and write call. |
| 221 | .IP "\fB\-showcerts\fR" 4 |
| 222 | .IX Item "-showcerts" |
| 223 | display the whole server certificate chain: normally only the server |
| 224 | certificate itself is displayed. |
| 225 | .IP "\fB\-prexit\fR" 4 |
| 226 | .IX Item "-prexit" |
| 227 | print session information when the program exits. This will always attempt |
| 228 | to print out information even if the connection fails. Normally information |
| 229 | will only be printed out once if the connection succeeds. This option is useful |
| 230 | because the cipher in use may be renegotiated or the connection may fail |
| 231 | because a client certificate is required or is requested only after an |
| 232 | attempt is made to access a certain \s-1URL\s0. Note: the output produced by this |
| 233 | option is not always accurate because a connection might never have been |
| 234 | established. |
| 235 | .IP "\fB\-state\fR" 4 |
| 236 | .IX Item "-state" |
| 237 | prints out the \s-1SSL\s0 session states. |
| 238 | .IP "\fB\-debug\fR" 4 |
| 239 | .IX Item "-debug" |
| 240 | print extensive debugging information including a hex dump of all traffic. |
| 241 | .IP "\fB\-msg\fR" 4 |
| 242 | .IX Item "-msg" |
| 243 | show all protocol messages with hex dump. |
| 244 | .IP "\fB\-nbio_test\fR" 4 |
| 245 | .IX Item "-nbio_test" |
| 246 | tests non-blocking I/O |
| 247 | .IP "\fB\-nbio\fR" 4 |
| 248 | .IX Item "-nbio" |
| 249 | turns on non-blocking I/O |
| 250 | .IP "\fB\-crlf\fR" 4 |
| 251 | .IX Item "-crlf" |
| 252 | this option translated a line feed from the terminal into \s-1CR+LF\s0 as required |
| 253 | by some servers. |
| 254 | .IP "\fB\-ign_eof\fR" 4 |
| 255 | .IX Item "-ign_eof" |
| 256 | inhibit shutting down the connection when end of file is reached in the |
| 257 | input. |
| 258 | .IP "\fB\-quiet\fR" 4 |
| 259 | .IX Item "-quiet" |
| 260 | inhibit printing of session and certificate information. This implicitly |
| 261 | turns on \fB\-ign_eof\fR as well. |
| 262 | .IP "\fB\-ssl2\fR, \fB\-ssl3\fR, \fB\-tls1\fR, \fB\-no_ssl2\fR, \fB\-no_ssl3\fR, \fB\-no_tls1\fR" 4 |
| 263 | .IX Item "-ssl2, -ssl3, -tls1, -no_ssl2, -no_ssl3, -no_tls1" |
| 264 | these options disable the use of certain \s-1SSL\s0 or \s-1TLS\s0 protocols. By default |
| 265 | the initial handshake uses a method which should be compatible with all |
| 266 | servers and permit them to use \s-1SSL\s0 v3, \s-1SSL\s0 v2 or \s-1TLS\s0 as appropriate. |
| 267 | .Sp |
| 268 | Unfortunately there are a lot of ancient and broken servers in use which |
| 269 | cannot handle this technique and will fail to connect. Some servers only |
| 270 | work if \s-1TLS\s0 is turned off with the \fB\-no_tls\fR option others will only |
| 271 | support \s-1SSL\s0 v2 and may need the \fB\-ssl2\fR option. |
| 272 | .IP "\fB\-bugs\fR" 4 |
| 273 | .IX Item "-bugs" |
| 274 | there are several known bug in \s-1SSL\s0 and \s-1TLS\s0 implementations. Adding this |
| 275 | option enables various workarounds. |
| 276 | .IP "\fB\-cipher cipherlist\fR" 4 |
| 277 | .IX Item "-cipher cipherlist" |
| 278 | this allows the cipher list sent by the client to be modified. Although |
| 279 | the server determines which cipher suite is used it should take the first |
| 280 | supported cipher in the list sent by the client. See the \fBciphers\fR |
| 281 | command for more information. |
| 282 | .IP "\fB\-starttls protocol\fR" 4 |
| 283 | .IX Item "-starttls protocol" |
| 284 | send the protocol-specific message(s) to switch to \s-1TLS\s0 for communication. |
| 285 | \&\fBprotocol\fR is a keyword for the intended protocol. Currently, the only |
| 286 | supported keywords are \*(L"smtp\*(R" and \*(L"pop3\*(R". |
| 287 | .IP "\fB\-engine id\fR" 4 |
| 288 | .IX Item "-engine id" |
| 289 | specifying an engine (by it's unique \fBid\fR string) will cause \fBs_client\fR |
| 290 | to attempt to obtain a functional reference to the specified engine, |
| 291 | thus initialising it if needed. The engine will then be set as the default |
| 292 | for all available algorithms. |
| 293 | .IP "\fB\-rand file(s)\fR" 4 |
| 294 | .IX Item "-rand file(s)" |
| 295 | a file or files containing random data used to seed the random number |
| 296 | generator, or an \s-1EGD\s0 socket (see \fIRAND_egd\fR\|(3)). |
| 297 | Multiple files can be specified separated by a OS-dependent character. |
| 298 | The separator is \fB;\fR for MS\-Windows, \fB,\fR for OpenVMS, and \fB:\fR for |
| 299 | all others. |
| 300 | .SH "CONNECTED COMMANDS" |
| 301 | .IX Header "CONNECTED COMMANDS" |
| 302 | If a connection is established with an \s-1SSL\s0 server then any data received |
| 303 | from the server is displayed and any key presses will be sent to the |
| 304 | server. When used interactively (which means neither \fB\-quiet\fR nor \fB\-ign_eof\fR |
| 305 | have been given), the session will be renegotiated if the line begins with an |
| 306 | \&\fBR\fR, and if the line begins with a \fBQ\fR or if end of file is reached, the |
| 307 | connection will be closed down. |
| 308 | .SH "NOTES" |
| 309 | .IX Header "NOTES" |
| 310 | \&\fBs_client\fR can be used to debug \s-1SSL\s0 servers. To connect to an \s-1SSL\s0 \s-1HTTP\s0 |
| 311 | server the command: |
| 312 | .PP |
| 313 | .Vb 1 |
| 314 | \& openssl s_client -connect servername:443 |
| 315 | .Ve |
| 316 | .PP |
| 317 | would typically be used (https uses port 443). If the connection succeeds |
| 318 | then an \s-1HTTP\s0 command can be given such as \*(L"\s-1GET\s0 /\*(R" to retrieve a web page. |
| 319 | .PP |
| 320 | If the handshake fails then there are several possible causes, if it is |
| 321 | nothing obvious like no client certificate then the \fB\-bugs\fR, \fB\-ssl2\fR, |
| 322 | \&\fB\-ssl3\fR, \fB\-tls1\fR, \fB\-no_ssl2\fR, \fB\-no_ssl3\fR, \fB\-no_tls1\fR options can be tried |
| 323 | in case it is a buggy server. In particular you should play with these |
| 324 | options \fBbefore\fR submitting a bug report to an OpenSSL mailing list. |
| 325 | .PP |
| 326 | A frequent problem when attempting to get client certificates working |
| 327 | is that a web client complains it has no certificates or gives an empty |
| 328 | list to choose from. This is normally because the server is not sending |
| 329 | the clients certificate authority in its \*(L"acceptable \s-1CA\s0 list\*(R" when it |
| 330 | requests a certificate. By using \fBs_client\fR the \s-1CA\s0 list can be viewed |
| 331 | and checked. However some servers only request client authentication |
| 332 | after a specific \s-1URL\s0 is requested. To obtain the list in this case it |
| 333 | is necessary to use the \fB\-prexit\fR option and send an \s-1HTTP\s0 request |
| 334 | for an appropriate page. |
| 335 | .PP |
| 336 | If a certificate is specified on the command line using the \fB\-cert\fR |
| 337 | option it will not be used unless the server specifically requests |
| 338 | a client certificate. Therefor merely including a client certificate |
| 339 | on the command line is no guarantee that the certificate works. |
| 340 | .PP |
| 341 | If there are problems verifying a server certificate then the |
| 342 | \&\fB\-showcerts\fR option can be used to show the whole chain. |
| 343 | .SH "BUGS" |
| 344 | .IX Header "BUGS" |
| 345 | Because this program has a lot of options and also because some of |
| 346 | the techniques used are rather old, the C source of s_client is rather |
| 347 | hard to read and not a model of how things should be done. A typical |
| 348 | \&\s-1SSL\s0 client program would be much simpler. |
| 349 | .PP |
| 350 | The \fB\-verify\fR option should really exit if the server verification |
| 351 | fails. |
| 352 | .PP |
| 353 | The \fB\-prexit\fR option is a bit of a hack. We should really report |
| 354 | information whenever a session is renegotiated. |
| 355 | .SH "SEE ALSO" |
| 356 | .IX Header "SEE ALSO" |
| 357 | \&\fIsess_id\fR\|(1), \fIs_server\fR\|(1), \fIciphers\fR\|(1) |