390 lines
15 KiB
Groff
390 lines
15 KiB
Groff
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.\" ========================================================================
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.\"
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.IX Title "S_CLIENT 1"
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.TH S_CLIENT 1 "2014-01-06" "1.0.1f" "OpenSSL"
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.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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.\" way too many mistakes in technical documents.
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.if n .ad l
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.nh
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.SH "NAME"
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s_client \- SSL/TLS client program
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.SH "SYNOPSIS"
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.IX Header "SYNOPSIS"
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\&\fBopenssl\fR \fBs_client\fR
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[\fB\-connect host:port\fR]
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[\fB\-verify depth\fR]
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[\fB\-cert filename\fR]
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[\fB\-certform DER|PEM\fR]
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[\fB\-key filename\fR]
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[\fB\-keyform DER|PEM\fR]
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[\fB\-pass arg\fR]
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[\fB\-CApath directory\fR]
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[\fB\-CAfile filename\fR]
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[\fB\-reconnect\fR]
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[\fB\-pause\fR]
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[\fB\-showcerts\fR]
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[\fB\-debug\fR]
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[\fB\-msg\fR]
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[\fB\-nbio_test\fR]
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[\fB\-state\fR]
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[\fB\-nbio\fR]
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[\fB\-crlf\fR]
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[\fB\-ign_eof\fR]
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[\fB\-quiet\fR]
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[\fB\-ssl2\fR]
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[\fB\-ssl3\fR]
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[\fB\-tls1\fR]
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[\fB\-no_ssl2\fR]
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[\fB\-no_ssl3\fR]
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[\fB\-no_tls1\fR]
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[\fB\-bugs\fR]
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[\fB\-cipher cipherlist\fR]
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[\fB\-starttls protocol\fR]
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[\fB\-engine id\fR]
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[\fB\-tlsextdebug\fR]
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[\fB\-no_ticket\fR]
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[\fB\-sess_out filename\fR]
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[\fB\-sess_in filename\fR]
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[\fB\-rand file(s)\fR]
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.SH "DESCRIPTION"
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.IX Header "DESCRIPTION"
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The \fBs_client\fR command implements a generic \s-1SSL/TLS\s0 client which connects
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to a remote host using \s-1SSL/TLS\s0. It is a \fIvery\fR useful diagnostic tool for
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\&\s-1SSL\s0 servers.
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.SH "OPTIONS"
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.IX Header "OPTIONS"
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.IP "\fB\-connect host:port\fR" 4
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.IX Item "-connect host:port"
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This specifies the host and optional port to connect to. If not specified
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then an attempt is made to connect to the local host on port 4433.
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.IP "\fB\-cert certname\fR" 4
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.IX Item "-cert certname"
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The certificate to use, if one is requested by the server. The default is
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not to use a certificate.
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.IP "\fB\-certform format\fR" 4
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.IX Item "-certform format"
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The certificate format to use: \s-1DER\s0 or \s-1PEM\s0. \s-1PEM\s0 is the default.
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.IP "\fB\-key keyfile\fR" 4
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.IX Item "-key keyfile"
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The private key to use. If not specified then the certificate file will
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be used.
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.IP "\fB\-keyform format\fR" 4
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.IX Item "-keyform format"
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The private format to use: \s-1DER\s0 or \s-1PEM\s0. \s-1PEM\s0 is the default.
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.IP "\fB\-pass arg\fR" 4
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.IX Item "-pass arg"
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the private key password source. For more information about the format of \fBarg\fR
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see the \fB\s-1PASS\s0 \s-1PHRASE\s0 \s-1ARGUMENTS\s0\fR section in \fIopenssl\fR\|(1).
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.IP "\fB\-verify depth\fR" 4
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.IX Item "-verify depth"
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The verify depth to use. This specifies the maximum length of the
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server certificate chain and turns on server certificate verification.
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Currently the verify operation continues after errors so all the problems
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with a certificate chain can be seen. As a side effect the connection
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will never fail due to a server certificate verify failure.
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.IP "\fB\-CApath directory\fR" 4
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.IX Item "-CApath directory"
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The directory to use for server certificate verification. This directory
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must be in \*(L"hash format\*(R", see \fBverify\fR for more information. These are
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also used when building the client certificate chain.
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.IP "\fB\-CAfile file\fR" 4
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.IX Item "-CAfile file"
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A file containing trusted certificates to use during server authentication
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and to use when attempting to build the client certificate chain.
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.IP "\fB\-purpose, \-ignore_critical, \-issuer_checks, \-crl_check, \-crl_check_all, \-policy_check, \-extended_crl, \-x509_strict, \-policy \-check_ss_sig\fR" 4
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.IX Item "-purpose, -ignore_critical, -issuer_checks, -crl_check, -crl_check_all, -policy_check, -extended_crl, -x509_strict, -policy -check_ss_sig"
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Set various certificate chain valiadition option. See the
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\&\fBverify\fR manual page for details.
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.IP "\fB\-reconnect\fR" 4
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.IX Item "-reconnect"
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reconnects to the same server 5 times using the same session \s-1ID\s0, this can
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be used as a test that session caching is working.
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.IP "\fB\-pause\fR" 4
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.IX Item "-pause"
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pauses 1 second between each read and write call.
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.IP "\fB\-showcerts\fR" 4
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.IX Item "-showcerts"
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display the whole server certificate chain: normally only the server
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certificate itself is displayed.
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.IP "\fB\-prexit\fR" 4
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.IX Item "-prexit"
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print session information when the program exits. This will always attempt
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to print out information even if the connection fails. Normally information
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will only be printed out once if the connection succeeds. This option is useful
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because the cipher in use may be renegotiated or the connection may fail
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because a client certificate is required or is requested only after an
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attempt is made to access a certain \s-1URL\s0. Note: the output produced by this
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option is not always accurate because a connection might never have been
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established.
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.IP "\fB\-state\fR" 4
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.IX Item "-state"
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prints out the \s-1SSL\s0 session states.
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.IP "\fB\-debug\fR" 4
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.IX Item "-debug"
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print extensive debugging information including a hex dump of all traffic.
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.IP "\fB\-msg\fR" 4
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.IX Item "-msg"
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show all protocol messages with hex dump.
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.IP "\fB\-nbio_test\fR" 4
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.IX Item "-nbio_test"
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tests non-blocking I/O
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.IP "\fB\-nbio\fR" 4
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.IX Item "-nbio"
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turns on non-blocking I/O
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.IP "\fB\-crlf\fR" 4
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.IX Item "-crlf"
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this option translated a line feed from the terminal into \s-1CR+LF\s0 as required
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by some servers.
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.IP "\fB\-ign_eof\fR" 4
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.IX Item "-ign_eof"
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inhibit shutting down the connection when end of file is reached in the
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input.
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.IP "\fB\-quiet\fR" 4
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.IX Item "-quiet"
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inhibit printing of session and certificate information. This implicitly
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turns on \fB\-ign_eof\fR as well.
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.IP "\fB\-psk_identity identity\fR" 4
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.IX Item "-psk_identity identity"
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Use the \s-1PSK\s0 identity \fBidentity\fR when using a \s-1PSK\s0 cipher suite.
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.IP "\fB\-psk key\fR" 4
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.IX Item "-psk key"
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Use the \s-1PSK\s0 key \fBkey\fR when using a \s-1PSK\s0 cipher suite. The key is
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given as a hexadecimal number without leading 0x, for example \-psk
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1a2b3c4d.
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.IP "\fB\-ssl2\fR, \fB\-ssl3\fR, \fB\-tls1\fR, \fB\-no_ssl2\fR, \fB\-no_ssl3\fR, \fB\-no_tls1\fR" 4
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.IX Item "-ssl2, -ssl3, -tls1, -no_ssl2, -no_ssl3, -no_tls1"
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these options disable the use of certain \s-1SSL\s0 or \s-1TLS\s0 protocols. By default
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the initial handshake uses a method which should be compatible with all
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servers and permit them to use \s-1SSL\s0 v3, \s-1SSL\s0 v2 or \s-1TLS\s0 as appropriate.
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.Sp
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Unfortunately there are a lot of ancient and broken servers in use which
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cannot handle this technique and will fail to connect. Some servers only
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work if \s-1TLS\s0 is turned off with the \fB\-no_tls\fR option others will only
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support \s-1SSL\s0 v2 and may need the \fB\-ssl2\fR option.
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.IP "\fB\-bugs\fR" 4
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.IX Item "-bugs"
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there are several known bug in \s-1SSL\s0 and \s-1TLS\s0 implementations. Adding this
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option enables various workarounds.
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.IP "\fB\-cipher cipherlist\fR" 4
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.IX Item "-cipher cipherlist"
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this allows the cipher list sent by the client to be modified. Although
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the server determines which cipher suite is used it should take the first
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supported cipher in the list sent by the client. See the \fBciphers\fR
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command for more information.
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.IP "\fB\-starttls protocol\fR" 4
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.IX Item "-starttls protocol"
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send the protocol-specific message(s) to switch to \s-1TLS\s0 for communication.
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\&\fBprotocol\fR is a keyword for the intended protocol. Currently, the only
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supported keywords are \*(L"smtp\*(R", \*(L"pop3\*(R", \*(L"imap\*(R", and \*(L"ftp\*(R".
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.IP "\fB\-tlsextdebug\fR" 4
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.IX Item "-tlsextdebug"
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print out a hex dump of any \s-1TLS\s0 extensions received from the server.
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.IP "\fB\-no_ticket\fR" 4
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.IX Item "-no_ticket"
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disable RFC4507bis session ticket support.
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.IP "\fB\-sess_out filename\fR" 4
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.IX Item "-sess_out filename"
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output \s-1SSL\s0 session to \fBfilename\fR
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.IP "\fB\-sess_in sess.pem\fR" 4
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.IX Item "-sess_in sess.pem"
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load \s-1SSL\s0 session from \fBfilename\fR. The client will attempt to resume a
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connection from this session.
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.IP "\fB\-engine id\fR" 4
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.IX Item "-engine id"
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specifying an engine (by its unique \fBid\fR string) will cause \fBs_client\fR
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to attempt to obtain a functional reference to the specified engine,
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thus initialising it if needed. The engine will then be set as the default
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for all available algorithms.
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.IP "\fB\-rand file(s)\fR" 4
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.IX Item "-rand file(s)"
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a file or files containing random data used to seed the random number
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generator, or an \s-1EGD\s0 socket (see \fIRAND_egd\fR\|(3)).
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Multiple files can be specified separated by a OS-dependent character.
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The separator is \fB;\fR for MS-Windows, \fB,\fR for OpenVMS, and \fB:\fR for
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all others.
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.SH "CONNECTED COMMANDS"
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.IX Header "CONNECTED COMMANDS"
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If a connection is established with an \s-1SSL\s0 server then any data received
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from the server is displayed and any key presses will be sent to the
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server. When used interactively (which means neither \fB\-quiet\fR nor \fB\-ign_eof\fR
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have been given), the session will be renegotiated if the line begins with an
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\&\fBR\fR, and if the line begins with a \fBQ\fR or if end of file is reached, the
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connection will be closed down.
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.SH "NOTES"
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.IX Header "NOTES"
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\&\fBs_client\fR can be used to debug \s-1SSL\s0 servers. To connect to an \s-1SSL\s0 \s-1HTTP\s0
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server the command:
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.PP
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.Vb 1
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\& openssl s_client \-connect servername:443
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.Ve
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.PP
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would typically be used (https uses port 443). If the connection succeeds
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then an \s-1HTTP\s0 command can be given such as \*(L"\s-1GET\s0 /\*(R" to retrieve a web page.
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.PP
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If the handshake fails then there are several possible causes, if it is
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nothing obvious like no client certificate then the \fB\-bugs\fR, \fB\-ssl2\fR,
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\&\fB\-ssl3\fR, \fB\-tls1\fR, \fB\-no_ssl2\fR, \fB\-no_ssl3\fR, \fB\-no_tls1\fR options can be tried
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in case it is a buggy server. In particular you should play with these
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options \fBbefore\fR submitting a bug report to an OpenSSL mailing list.
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.PP
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A frequent problem when attempting to get client certificates working
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is that a web client complains it has no certificates or gives an empty
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list to choose from. This is normally because the server is not sending
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the clients certificate authority in its \*(L"acceptable \s-1CA\s0 list\*(R" when it
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requests a certificate. By using \fBs_client\fR the \s-1CA\s0 list can be viewed
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and checked. However some servers only request client authentication
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after a specific \s-1URL\s0 is requested. To obtain the list in this case it
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is necessary to use the \fB\-prexit\fR option and send an \s-1HTTP\s0 request
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for an appropriate page.
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.PP
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If a certificate is specified on the command line using the \fB\-cert\fR
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option it will not be used unless the server specifically requests
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a client certificate. Therefor merely including a client certificate
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on the command line is no guarantee that the certificate works.
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.PP
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If there are problems verifying a server certificate then the
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\&\fB\-showcerts\fR option can be used to show the whole chain.
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.PP
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Since the SSLv23 client hello cannot include compression methods or extensions
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these will only be supported if its use is disabled, for example by using the
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\&\fB\-no_sslv2\fR option.
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.SH "BUGS"
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.IX Header "BUGS"
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Because this program has a lot of options and also because some of
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the techniques used are rather old, the C source of s_client is rather
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hard to read and not a model of how things should be done. A typical
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\&\s-1SSL\s0 client program would be much simpler.
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.PP
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The \fB\-verify\fR option should really exit if the server verification
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fails.
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.PP
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The \fB\-prexit\fR option is a bit of a hack. We should really report
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information whenever a session is renegotiated.
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.SH "SEE ALSO"
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.IX Header "SEE ALSO"
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\&\fIsess_id\fR\|(1), \fIs_server\fR\|(1), \fIciphers\fR\|(1)
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