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diff --git a/ncat/docs/ncat.1 b/ncat/docs/ncat.1 new file mode 100644 index 0000000..7fbc5b5 --- /dev/null +++ b/ncat/docs/ncat.1 @@ -0,0 +1,787 @@ +'\" t +.\" Title: Ncat +.\" Author: [see the "Authors" section] +.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/> +.\" Date: 05/17/2023 +.\" Manual: Ncat Reference Guide +.\" Source: Ncat +.\" Language: English +.\" +.TH "NCAT" "1" "05/17/2023" "Ncat" "Ncat Reference Guide" +.\" ----------------------------------------------------------------- +.\" * Define some portability stuff +.\" ----------------------------------------------------------------- +.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +.\" http://bugs.debian.org/507673 +.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html +.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +.ie \n(.g .ds Aq \(aq +.el .ds Aq ' +.\" ----------------------------------------------------------------- +.\" * set default formatting +.\" ----------------------------------------------------------------- +.\" disable hyphenation +.nh +.\" disable justification (adjust text to left margin only) +.ad l +.\" ----------------------------------------------------------------- +.\" * MAIN CONTENT STARTS HERE * +.\" ----------------------------------------------------------------- +.SH "NAME" +ncat \- Concatenate and redirect sockets +.SH "SYNOPSIS" +.HP \w'\fBncat\fR\ 'u +\fBncat\fR [\fIOPTIONS\fR...] [\fIhostname\fR] [\fIport\fR] +.SH "DESCRIPTION" +.PP +Ncat is a feature\-packed networking utility which reads and writes data across networks from the command line\&. Ncat was written for the Nmap Project and is the culmination of the currently splintered family of Netcat incarnations\&. It is designed to be a reliable back\-end tool to instantly provide network connectivity to other applications and users\&. Ncat will not only work with IPv4 and IPv6 but provides the user with a virtually limitless number of potential uses\&. +.PP +Among Ncat\*(Aqs vast number of features there is the ability to chain Ncats together; redirection of TCP, UDP, and SCTP ports to other sites; SSL support; and proxy connections via SOCKS4, SOCKS5 or HTTP proxies (with optional proxy authentication as well)\&. Some general principles apply to most applications and thus give you the capability of instantly adding networking support to software that would normally never support it\&. +.SH "OPTIONS SUMMARY" +.PP +.if n \{\ +.RS 4 +.\} +.nf +Ncat 7\&.94 ( https://nmap\&.org/ncat ) +Usage: ncat [options] [hostname] [port] + +Options taking a time assume seconds\&. Append \*(Aqms\*(Aq for milliseconds, +\*(Aqs\*(Aq for seconds, \*(Aqm\*(Aq for minutes, or \*(Aqh\*(Aq for hours (e\&.g\&. 500ms)\&. + \-4 Use IPv4 only + \-6 Use IPv6 only + \-U, \-\-unixsock Use Unix domain sockets only + \-\-vsock Use vsock sockets only + \-C, \-\-crlf Use CRLF for EOL sequence + \-c, \-\-sh\-exec <command> Executes the given command via /bin/sh + \-e, \-\-exec <command> Executes the given command + \-\-lua\-exec <filename> Executes the given Lua script + \-g hop1[,hop2,\&.\&.\&.] Loose source routing hop points (8 max) + \-G <n> Loose source routing hop pointer (4, 8, 12, \&.\&.\&.) + \-m, \-\-max\-conns <n> Maximum <n> simultaneous connections + \-h, \-\-help Display this help screen + \-d, \-\-delay <time> Wait between read/writes + \-o, \-\-output <filename> Dump session data to a file + \-x, \-\-hex\-dump <filename> Dump session data as hex to a file + \-i, \-\-idle\-timeout <time> Idle read/write timeout + \-p, \-\-source\-port port Specify source port to use + \-s, \-\-source addr Specify source address to use (doesn\*(Aqt affect \-l) + \-l, \-\-listen Bind and listen for incoming connections + \-k, \-\-keep\-open Accept multiple connections in listen mode + \-n, \-\-nodns Do not resolve hostnames via DNS + \-t, \-\-telnet Answer Telnet negotiations + \-u, \-\-udp Use UDP instead of default TCP + \-\-sctp Use SCTP instead of default TCP + \-v, \-\-verbose Set verbosity level (can be used several times) + \-w, \-\-wait <time> Connect timeout + \-z Zero\-I/O mode, report connection status only + \-\-append\-output Append rather than clobber specified output files + \-\-send\-only Only send data, ignoring received; quit on EOF + \-\-recv\-only Only receive data, never send anything + \-\-no\-shutdown Continue half\-duplex when receiving EOF on stdin + \-\-allow Allow only given hosts to connect to Ncat + \-\-allowfile A file of hosts allowed to connect to Ncat + \-\-deny Deny given hosts from connecting to Ncat + \-\-denyfile A file of hosts denied from connecting to Ncat + \-\-broker Enable Ncat\*(Aqs connection brokering mode + \-\-chat Start a simple Ncat chat server + \-\-proxy <addr[:port]> Specify address of host to proxy through + \-\-proxy\-type <type> Specify proxy type ("http", "socks4", "socks5") + \-\-proxy\-auth <auth> Authenticate with HTTP or SOCKS proxy server + \-\-proxy\-dns <type> Specify where to resolve proxy destination + \-\-ssl Connect or listen with SSL + \-\-ssl\-cert Specify SSL certificate file (PEM) for listening + \-\-ssl\-key Specify SSL private key (PEM) for listening + \-\-ssl\-verify Verify trust and domain name of certificates + \-\-ssl\-trustfile PEM file containing trusted SSL certificates + \-\-ssl\-ciphers Cipherlist containing SSL ciphers to use + \-\-ssl\-servername Request distinct server name (SNI) + \-\-ssl\-alpn ALPN protocol list to use + \-\-version Display Ncat\*(Aqs version information and exit + +See the ncat(1) manpage for full options, descriptions and usage examples +.fi +.if n \{\ +.RE +.\} +.sp +.SH "CONNECT MODE AND LISTEN MODE" +.PP +Ncat operates in one of two primary modes: connect mode and listen mode\&. Other modes, such as the HTTP proxy server, act as special cases of these two\&. In connect mode, Ncat works as a client\&. In listen mode it is a server\&. +.PP +In connect mode, the +\fB\fIhostname\fR\fR +and +\fB\fIport\fR\fR +arguments tell what to connect to\&. +\fB\fIhostname\fR\fR +is required, and may be a hostname or IP address\&. If +\fB\fIport\fR\fR +is supplied, it must be a decimal port number\&. If omitted, it defaults to 31337\&. +.PP +In listen mode, +\fB\fIhostname\fR\fR +and +\fB\fIport\fR\fR +control the address the server will bind to\&. Both arguments are optional in listen mode\&. If +\fB\fIhostname\fR\fR +is omitted, it defaults to listening on all available addresses over IPv4 and IPv6\&. If +\fB\fIport\fR\fR +is omitted, it defaults to 31337\&. +.SH "PROTOCOL OPTIONS" +.PP +\fB\-4\fR (IPv4 only) +.RS 4 +Force the use of IPv4 only\&. +.RE +.PP +\fB\-6\fR (IPv6 only) +.RS 4 +Force the use of IPv6 only\&. +.RE +.PP +\fB\-U\fR, \fB\-\-unixsock\fR (Use Unix domain sockets) +.RS 4 +Use Unix domain sockets rather than network sockets\&. This option may be used on its own for stream sockets, or combined with +\fB\-\-udp\fR +for datagram sockets\&. A description of +\fB\-U\fR +mode is in +the section called \(lqUNIX DOMAIN SOCKETS\(rq\&. +.RE +.PP +\fB\-u\fR, \fB\-\-udp\fR (Use UDP) +.RS 4 +Use UDP for the connection (the default is TCP)\&. +.RE +.PP +\fB\-\-sctp\fR (Use SCTP) +.RS 4 +Use SCTP for the connection (the default is TCP)\&. SCTP support is implemented in TCP\-compatible mode\&. +.RE +.PP +\fB\-\-vsock\fR (Use AF_VSOCK sockets) +.RS 4 +Use AF_VSOCK sockets rather than the default TCP sockets (Linux only)\&. This option may be used on its own for stream sockets or combined with +\fB\-\-udp\fR +for datagram sockets\&. A description of +\fB\-\-vsock\fR +mode is in +the section called \(lqAF_VSOCK SOCKETS\(rq\&. +.RE +.SH "CONNECT MODE OPTIONS" +.PP +\fB\-g \fR\fB\fIhop1\fR\fR\fB[,\fIhop2\fR,\&.\&.\&.]\fR (Loose source routing) +.RS 4 +Sets hops for IPv4 loose source routing\&. You can use +\fB\-g\fR +once with a comma\-separated list of hops, use +\fB\-g\fR +multiple times with single hops to build the list, or combine the two\&. Hops can be given as IP addresses or hostnames\&. +.RE +.PP +\fB\-G \fR\fB\fIptr\fR\fR (Set source routing pointer) +.RS 4 +Sets the IPv4 source route +\(lqpointer\(rq +for use with +\fB\-g\fR\&. The argument must be a multiple of 4 and no more than 28\&. Not all operating systems support setting this pointer to anything other than four\&. +.RE +.PP +\fB\-p \fR\fB\fIport\fR\fR, \fB\-\-source\-port \fR\fB\fIport\fR\fR (Specify source port) +.RS 4 +Set the port number for Ncat to bind to\&. +.RE +.PP +\fB\-s \fR\fB\fIhost\fR\fR, \fB\-\-source \fR\fB\fIhost\fR\fR (Specify source address) +.RS 4 +Set the address for Ncat to bind to\&. +.RE +.SH "LISTEN MODE OPTIONS" +.PP +See +the section called \(lqACCESS CONTROL OPTIONS\(rq +for information on limiting the hosts that may connect to the listening Ncat process\&. +.PP +\fB\-l\fR, \fB\-\-listen\fR (Listen for connections) +.RS 4 +Listen for connections rather than connecting to a remote machine +.RE +.PP +\fB\-m \fR\fB\fInumconns\fR\fR, \fB\-\-max\-conns \fR\fB\fInumconns\fR\fR (Specify maximum number of connections) +.RS 4 +The maximum number of simultaneous connections accepted by an Ncat instance\&. 100 is the default (60 on Windows)\&. +.RE +.PP +\fB\-k\fR, \fB\-\-keep\-open\fR (Accept multiple connections) +.RS 4 +Normally a listening server accepts only one connection and then quits when the connection is closed\&. This option makes it accept multiple simultaneous connections and wait for more connections after they have all been closed\&. It must be combined with +\fB\-\-listen\fR\&. In this mode there is no way for Ncat to know when its network input is finished, so it will keep running until interrupted\&. This also means that it will never close its output stream, so any program reading from Ncat and looking for end\-of\-file will also hang\&. +.RE +.PP +\fB\-\-broker\fR (Connection brokering) +.RS 4 +Allow multiple parties to connect to a centralised Ncat server and communicate with each other\&. Ncat can broker communication between systems that are behind a NAT or otherwise unable to directly connect\&. This option is used in conjunction with +\fB\-\-listen\fR, which causes the +\fB\-\-listen\fR +port to have broker mode enabled\&. +.RE +.PP +\fB\-\-chat\fR (Ad\-hoc \(lqchat server\(rq) +.RS 4 +The +\fB\-\-chat\fR +option enables chat mode, intended for the exchange of text between several users\&. In chat mode, connection brokering is turned on\&. Ncat prefixes each message received with an ID before relaying it to the other connections\&. The ID is unique for each connected client\&. This helps distinguish who sent what\&. Additionally, non\-printing characters such as control characters are escaped to keep them from doing damage to a terminal\&. +.RE +.SH "SSL OPTIONS" +.PP +\fB\-\-ssl\fR (Use SSL) +.RS 4 +In connect mode, this option transparently negotiates an SSL session with an SSL server to securely encrypt the connection\&. This is particularly handy for talking to SSL enabled HTTP servers, etc\&. +.sp +In server mode, this option listens for incoming SSL connections, rather than plain untunneled traffic\&. +.sp +In UDP mode, this option enables Datagram TLS (DTLS)\&. +.RE +.PP +\fB\-\-ssl\-verify\fR (Verify server certificates) +.RS 4 +In client mode, +\fB\-\-ssl\-verify\fR +is like +\fB\-\-ssl\fR +except that it also requires verification of the server certificate\&. Ncat comes with a default set of trusted certificates in the file +ca\-bundle\&.crt\&. +Some operating systems provide a default list of trusted certificates; these will also be used if available\&. Use +\fB\-\-ssl\-trustfile\fR +to give a custom list\&. Use +\fB\-v\fR +one or more times to get details about verification failures\&. +Ncat does not check for revoked certificates\&. +.sp +This option has no effect in server mode\&. +.RE +.PP +\fB\-\-ssl\-cert \fR\fB\fIcertfile\&.pem\fR\fR (Specify SSL certificate) +.RS 4 +This option gives the location of a PEM\-encoded certificate files used to authenticate the server (in listen mode) or the client (in connect mode)\&. Use it in combination with +\fB\-\-ssl\-key\fR\&. +.RE +.PP +\fB\-\-ssl\-key \fR\fB\fIkeyfile\&.pem\fR\fR (Specify SSL private key) +.RS 4 +This option gives the location of the PEM\-encoded private key file that goes with the certificate named with +\fB\-\-ssl\-cert\fR\&. +.RE +.PP +\fB\-\-ssl\-trustfile \fR\fB\fIcert\&.pem\fR\fR (List trusted certificates) +.RS 4 +This option sets a list of certificates that are trusted for purposes of certificate verification\&. It has no effect unless combined with +\fB\-\-ssl\-verify\fR\&. The argument to this option is the name of a PEM +file containing trusted certificates\&. Typically, the file will contain certificates of certification authorities, though it may also contain server certificates directly\&. When this option is used, Ncat does not use its default certificates\&. +.RE +.PP +\fB\-\-ssl\-ciphers \fR\fB\fIcipherlist\fR\fR (Specify SSL ciphersuites) +.RS 4 +This option sets the list of ciphersuites that Ncat will use when connecting to servers or when accepting SSL connections from clients\&. The syntax is described in the OpenSSL ciphers(1) man page, and defaults to +ALL:!aNULL:!eNULL:!LOW:!EXP:!RC4:!MD5:@STRENGTH +.RE +.PP +\fB\-\-ssl\-servername \fR\fB\fIname\fR\fR (Request distinct server name) +.RS 4 +In client mode, this option sets the TLS SNI (Server Name Indication) extension, which tells the server the name of the logical server Ncat is contacting\&. This is important when the target server hosts multiple virtual servers at a single underlying network address\&. If the option is not provided, the TLS SNI extension will be populated with the target server hostname\&. +.RE +.PP +\fB\-\-ssl\-alpn \fR\fB\fIALPN list\fR\fR (Specify ALPN protocol list) +.RS 4 +This option allows you to specify a comma\-separated list of protocols to send via the Application\-Layer Protocol Negotiation (ALPN) TLS extension\&. Not supported by all versions of OpenSSL\&. +.RE +.SH "PROXY OPTIONS" +.PP +\fB\-\-proxy \fR\fB\fIhost\fR\fR\fB[:\fIport\fR]\fR (Specify proxy address) +.RS 4 +Requests proxying through +\fIhost\fR:\fIport\fR, using the protocol specified by +\fB\-\-proxy\-type\fR\&. +.sp +If no port is specified, the proxy protocol\*(Aqs well\-known port is used (1080 for SOCKS and 3128 for HTTP)\&. When specifying an IPv6 HTTP proxy server using the IP address rather than the hostname, the square\-bracket notation (for example [2001:db8::1]:8080) MUST be used to separate the port from the IPv6 address\&. If the proxy requires authentication, use +\fB\-\-proxy\-auth\fR\&. +.RE +.PP +\fB\-\-proxy\-type \fR\fB\fIproto\fR\fR (Specify proxy protocol) +.RS 4 +In connect mode, this option requests the protocol +\fIproto\fR +to connect through the proxy host specified by +\fB\-\-proxy\fR\&. In listen mode, this option has Ncat act as a proxy server using the specified protocol\&. +.sp +The currently available protocols in connect mode are +http +(CONNECT), +socks4 +(SOCKSv4), and +socks5 +(SOCKSv5)\&. The only server currently supported is +http\&. If this option is not used, the default protocol is +http\&. +.RE +.PP +\fB\-\-proxy\-auth \fR\fB\fIuser\fR\fR\fB[:\fIpass\fR]\fR (Specify proxy credentials) +.RS 4 +In connect mode, gives the credentials that will be used to connect to the proxy server\&. In listen mode, gives the credentials that will be required of connecting clients\&. For use with +\fB\-\-proxy\-type http\fR +or +\fB\-\-proxy\-type socks5\fR, the form should be username:password\&. For +\fB\-\-proxy\-type socks4\fR, it should be a username only\&. +.sp +These credentials can be alternatively passed onto Ncat by setting environment variable +\fBNCAT_PROXY_AUTH\fR, which reduces the risk of the credentials being captured in process logs\&. (Option +\fB\-\-proxy\-auth\fR +takes precedence\&.) +.RE +.PP +\fB\-\-proxy\-dns \fR\fB\fItype\fR\fR (Specify where to resolve proxy destination) +.RS 4 +In connect mode, it provides control over whether proxy destination hostnames are resolved by the remote proxy server or locally, by Ncat itself\&. Possible values for +\fItype\fR +are: +.sp +local +\- Hostnames are resolved locally on the Ncat host\&. Ncat exits with error if the hostname cannot be resolved\&. +.sp +remote +\- Hostnames are passed directly onto the remote proxy server\&. This is the default behavior\&. +.sp +both +\- Hostname resolution is first attempted on the Ncat host\&. Unresolvable hostnames are passed onto the remote proxy server\&. +.sp +none +\- Hostname resolution is completely disabled\&. Only a literal IPv4 or IPv6 address can be used as the proxy destination\&. +.sp +Local hostname resolution generally respects IP version specified with options +\fB\-4\fR +or +\fB\-6\fR, except for SOCKS4, which is incompatible with IPv6\&. +.RE +.SH "COMMAND EXECUTION OPTIONS" +.PP +\fB\-e \fR\fB\fIcommand\fR\fR, \fB\-\-exec \fR\fB\fIcommand\fR\fR (Execute command) +.RS 4 +Execute the specified command after a connection has been established\&. The command must be specified as a full pathname\&. All input from the remote client will be sent to the application and responses sent back to the remote client over the socket, thus making your command\-line application interactive over a socket\&. Combined with +\fB\-\-keep\-open\fR, Ncat will handle multiple simultaneous connections to your specified port/application like inetd\&. Ncat will only accept a maximum, definable, number of simultaneous connections controlled by the +\fB\-m\fR +option\&. By default this is set to 100 (60 on Windows)\&. +.RE +.PP +\fB\-c \fR\fB\fIcommand\fR\fR, \fB\-\-sh\-exec \fR\fB\fIcommand\fR\fR (Execute command via sh) +.RS 4 +Same as +\fB\-e\fR, except it tries to execute the command via +/bin/sh\&. This means you don\*(Aqt have to specify the full path for the command, and shell facilities like environment variables are available\&. +.RE +.PP +\fB\-\-lua\-exec \fR\fB\fIfile\fR\fR (Execute a \&.lua script) +.RS 4 +Runs the specified file as a Lua script after a connection has been established, using a built\-in interpreter\&. Both the script\*(Aqs standard input and the standard output are redirected to the connection data streams\&. +.RE +.PP +All exec options add the following variables to the child\*(Aqs environment: +.PP +\fBNCAT_REMOTE_ADDR\fR, \fBNCAT_REMOTE_PORT\fR +.RS 4 +The IP address and port number of the remote host\&. In connect mode, it\*(Aqs the target\*(Aqs address; in listen mode, it\*(Aqs the client\*(Aqs address\&. +.RE +.PP +\fBNCAT_LOCAL_ADDR\fR, \fBNCAT_LOCAL_PORT\fR +.RS 4 +The IP address and port number of the local end of the connection\&. +.RE +.PP +\fBNCAT_PROTO\fR +.RS 4 +The protocol in use: one of +TCP, +UDP, and +SCTP\&. +.RE +.SH "ACCESS CONTROL OPTIONS" +.PP +\fB\-\-allow \fR\fB\fIhost\fR\fR\fB[,\fIhost\fR,\&.\&.\&.]\fR (Allow connections) +.RS 4 +The list of hosts specified will be the only hosts allowed to connect to the Ncat process\&. All other connection attempts will be disconnected\&. In case of a conflict between +\fB\-\-allow\fR +and +\fB\-\-deny\fR, +\fB\-\-allow\fR +takes precedence\&. Host specifications follow the same syntax used by Nmap\&. +.RE +.PP +\fB\-\-allowfile \fR\fB\fIfile\fR\fR (Allow connections from file) +.RS 4 +This has the same functionality as +\fB\-\-allow\fR, except that the allowed hosts are provided in a new\-line delimited allow file, rather than directly on the command line\&. +.RE +.PP +\fB\-\-deny \fR\fB\fIhost\fR\fR\fB[,\fIhost\fR,\&.\&.\&.]\fR (Deny connections) +.RS 4 +Issue Ncat with a list of hosts that will not be allowed to connect to the listening Ncat process\&. Specified hosts will have their session silently terminated if they try to connect\&. In case of a conflict between +\fB\-\-allow\fR +and +\fB\-\-deny\fR, +\fB\-\-allow\fR +takes precedence\&. Host specifications follow the same syntax used by Nmap\&. +.RE +.PP +\fB\-\-denyfile \fR\fB\fIfile\fR\fR (Deny connections from file) +.RS 4 +This is the same functionality as +\fB\-\-deny\fR, except that excluded hosts are provided in a new\-line delimited deny file, rather than directly on the command line\&. +.RE +.SH "TIMING OPTIONS" +.PP +These options accept a +time +parameter\&. This is specified in seconds by default, though you can append +ms, +s, +m, or +h +to the value to specify milliseconds, seconds, minutes, or hours\&. +.PP +\fB\-d \fR\fB\fItime\fR\fR, \fB\-\-delay \fR\fB\fItime\fR\fR (Specify line delay) +.RS 4 +Set the delay interval for lines sent\&. This effectively limits the number of lines that Ncat will send in the specified period\&. This may be useful for low\-bandwidth sites, or have other uses such as coping with annoying +\fBiptables \-\-limit\fR +options\&. +.RE +.PP +\fB\-i \fR\fB\fItime\fR\fR, \fB\-\-idle\-timeout \fR\fB\fItime\fR\fR (Specify idle timeout) +.RS 4 +Set a fixed timeout for idle connections\&. If the idle timeout is reached, the connection is terminated\&. +.RE +.PP +\fB\-w \fR\fB\fItime\fR\fR, \fB\-\-wait \fR\fB\fItime\fR\fR (Specify connect timeout) +.RS 4 +Set a fixed timeout for connection attempts\&. +.RE +.SH "OUTPUT OPTIONS" +.PP +\fB\-o \fR\fB\fIfile\fR\fR, \fB\-\-output \fR\fB\fIfile\fR\fR (Save session data) +.RS 4 +Dump session data to a file +.RE +.PP +\fB\-x \fR\fB\fIfile\fR\fR, \fB\-\-hex\-dump \fR\fB\fIfile\fR\fR (Save session data in hex) +.RS 4 +Dump session data in hex to a file\&. +.RE +.PP +\fB\-\-append\-output\fR (Append output) +.RS 4 +Issue Ncat with +\fB\-\-append\-ouput\fR +along with +\fB\-o\fR +and/or +\fB\-x\fR +and it will append the resulted output rather than truncating the specified output files\&. +.RE +.PP +\fB\-v\fR, \fB\-\-verbose\fR (Be verbose) +.RS 4 +Issue Ncat with +\fB\-v\fR +and it will be verbose and display all kinds of useful connection based information\&. Use more than once (\fB\-vv\fR, +\fB\-vvv\fR\&.\&.\&.) for greater verbosity\&. +.RE +.SH "MISC OPTIONS" +.PP +\fB\-C\fR, \fB\-\-crlf\fR (Use CRLF as EOL) +.RS 4 +This option tells Ncat to convert LF +line endings to CRLF +when taking input from standard input\&. +This is useful for talking to some stringent servers directly from a terminal in one of the many common plain\-text protocols that use CRLF for end\-of\-line\&. +.RE +.PP +\fB\-h\fR, \fB\-\-help\fR (Help screen) +.RS 4 +Displays a short help screen with common options and parameters, and then exits\&. +.RE +.PP +\fB\-\-recv\-only\fR (Only receive data) +.RS 4 +If this option is passed, Ncat will only receive data and will not try to send anything\&. +.RE +.PP +\fB\-\-send\-only\fR (Only send data) +.RS 4 +If this option is passed, then Ncat will only send data and will ignore anything received\&. This option also causes Ncat to close the network connection and terminate after EOF is received on standard input\&. +.RE +.PP +\fB\-\-no\-shutdown\fR (Do not shutdown into half\-duplex mode) +.RS 4 +If this option is passed, Ncat will not invoke shutdown on a socket after seeing EOF on stdin\&. This is provided for backward\-compatibility with OpenBSD netcat, which exhibits this behavior when executed with its \*(Aq\-d\*(Aq option\&. +.RE +.PP +\fB\-n\fR, \fB\-\-nodns\fR (Do not resolve hostnames) +.RS 4 +Completely disable hostname resolution across all Ncat options, such as the destination, source address, source routing hops, and the proxy\&. All addresses must be specified numerically\&. (Note that resolution of proxy destinations is controlled separately via option +\fB\-\-proxy\-dns\fR\&.) +.RE +.PP +\fB\-t\fR, \fB\-\-telnet\fR (Answer Telnet negotiations) +.RS 4 +Handle DO/DONT WILL/WONT Telnet negotiations\&. This makes it possible to script Telnet sessions with Ncat\&. +.RE +.PP +\fB\-\-version\fR (Display version) +.RS 4 +Displays the Ncat version number and exits\&. +.RE +.SH "UNIX DOMAIN SOCKETS" +.PP +The +\fB\-U\fR +option (same as +\fB\-\-unixsock\fR) causes Ncat to use Unix domain sockets rather than network sockets\&. Unix domain sockets exist as an entry in the filesystem\&. You must give the name of a socket to connect to or to listen on\&. For example, to make a connection, +.PP +\fBncat \-U ~/unixsock\fR +.PP +To listen on a socket: +.PP +\fBncat \-l \-U ~/unixsock\fR +.PP +Listen mode will create the socket if it doesn\*(Aqt exist\&. The socket will continue to exist after the program ends\&. +.PP +Both stream and datagram domain sockets are supported\&. Use +\fB\-U\fR +on its own for stream sockets, or combine it with +\fB\-\-udp\fR +for datagram sockets\&. Datagram sockets require a source socket to connect from\&. By default, a source socket with a random filename will be created as needed, and deleted when the program ends\&. Use the +\fB\-\-source\fR +with a path to use a source socket with a specific name\&. +.SH "AF_VSOCK SOCKETS" +.PP +The +\fB\-\-vsock\fR +option causes Ncat to use AF_VSOCK sockets rather than network sockets\&. A CID must be given instead of a hostname or IP address\&. For example, to make a connection to the host, +.PP +\fBncat \-\-vsock 2 1234\fR +.PP +To listen on a socket: +.PP +\fBncat \-l \-\-vsock 1234\fR +.PP +Both stream and datagram domain sockets are supported, but socket type availability depends on the hypervisor\&. Use +\fB\-\-vsock\fR +on its own for stream sockets, or combine it with +\fB\-\-udp\fR +for datagram sockets\&. +.SH "EXAMPLES" +.PP +Connect to example\&.org on TCP port 8080\&. +.RS 4 +\fBncat example\&.org 8080\fR +.RE +.PP +Listen for connections on TCP port 8080\&. +.RS 4 +\fBncat \-l 8080\fR +.RE +.PP +Redirect TCP port 8080 on the local machine to host on port 80\&. +.RS 4 +\fBncat \-\-sh\-exec "ncat example\&.org 80" \-l 8080 \-\-keep\-open\fR +.RE +.PP +Bind to TCP port 8081 and attach /bin/bash for the world to access freely\&. +.RS 4 +\fBncat \-\-exec "/bin/bash" \-l 8081 \-\-keep\-open\fR +.RE +.PP +Bind a shell to TCP port 8081, limit access to hosts on a local network, and limit the maximum number of simultaneous connections to 3\&. +.RS 4 +\fBncat \-\-exec "/bin/bash" \-\-max\-conns 3 \-\-allow 192\&.168\&.0\&.0/24 \-l 8081 \-\-keep\-open\fR +.RE +.PP +Connect to smtphost:25 through a SOCKS4 server on port 1080\&. +.RS 4 +\fBncat \-\-proxy socks4host \-\-proxy\-type socks4 \-\-proxy\-auth joe smtphost 25\fR +.RE +.PP +Connect to smtphost:25 through a SOCKS5 server on port 1080\&. +.RS 4 +\fBncat \-\-proxy socks5host \-\-proxy\-type socks5 \-\-proxy\-auth joe:secret smtphost 25\fR +.RE +.PP +Create an HTTP proxy server on localhost port 8888\&. +.RS 4 +\fBncat \-l \-\-proxy\-type http localhost 8888\fR +.RE +.PP +Send a file over TCP port 9899 from host2 (client) to host1 (server)\&. +.RS 4 +HOST1$ +\fBncat \-l 9899 > outputfile\fR +.sp +HOST2$ +\fBncat HOST1 9899 < inputfile\fR +.RE +.PP +Transfer in the other direction, turning Ncat into a \(lqone file\(rq server\&. +.RS 4 +HOST1$ +\fBncat \-l 9899 < inputfile\fR +.sp +HOST2$ +\fBncat HOST1 9899 > outputfile\fR +.RE +.SH "EXIT CODE" +.PP +The exit code reflects whether a connection was made and completed successfully\&. 0 means there was no error\&. 1 means there was a network error of some kind, for example +\(lqConnection refused\(rq +or +\(lqConnection reset\(rq\&. 2 is reserved for all other errors, like an invalid option or a nonexistent file\&. +.SH "BUGS" +.PP +Like its authors, Ncat isn\*(Aqt perfect\&. But you can help make it better by sending bug reports or even writing patches\&. If Ncat doesn\*(Aqt behave the way you expect, first upgrade to the latest version available from +\m[blue]\fB\%https://nmap.org\fR\m[]\&. If the problem persists, do some research to determine whether it has already been discovered and addressed\&. Try Googling the error message or browsing the +nmap\-dev +archives at +\m[blue]\fB\%https://seclists.org/\fR\m[]\&. + +Read this full manual page as well\&. If nothing comes of this, mail a bug report to +<dev@nmap\&.org>\&. Please include everything you have learned about the problem, as well as what version of Ncat you are running and what operating system version it is running on\&. Problem reports and Ncat usage questions sent to dev@nmap\&.org are far more likely to be answered than those sent to Fyodor directly\&. +.PP +Code patches to fix bugs are even better than bug reports\&. Basic instructions for creating patch files with your changes are available at +\m[blue]\fB\%https://svn.nmap.org/nmap/HACKING\fR\m[]\&. Patches may be sent to +nmap\-dev +(recommended) or to Fyodor directly\&. +.SH "AUTHORS" +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Chris Gibson +<chris@linuxops\&.net> +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Gordon Lyon (Fyodor)<fyodor@nmap\&.org> +(\m[blue]\fB\%http://insecure.org\fR\m[]) +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Kris Katterjohn +<katterjohn@gmail\&.com> +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Mixter +<mixter@gmail\&.com> +.RE +.PP +The original Netcat was written by *Hobbit* +<hobbit@avian\&.org>\&. While Ncat isn\*(Aqt built on any code from the +\(lqtraditional\(rq +Netcat (or any other implementation), Ncat is most definitely based on Netcat in spirit and functionality\&. +.SH "LEGAL NOTICES" +.SS "Ncat Copyright and Licensing" +.PP +Ncat is (C) 2005\(en2022 Nmap Software LLC\&. It is distributed as free and open source software under the same license terms as our Nmap software\&. Precise terms and further details are available +from \m[blue]\fB\%https://nmap.org/man/man-legal.html\fR\m[]\&. +.SS "Creative Commons License for this Ncat Guide" +.PP +This +Ncat Reference Guide +is (C) 2005\(en2022 Nmap Software LLC\&. It is hereby placed under version 3\&.0 of the +\m[blue]\fBCreative Commons Attribution License\fR\m[]\&\s-2\u[1]\d\s+2\&. This allows you redistribute and modify the work as you desire, as long as you credit the original source\&. Alternatively, you may choose to treat this document as falling under the same license as Ncat itself (discussed previously)\&. +.SS "Source Code Availability and Community Contributions" +.PP +Source is provided to this software because we believe users have a right to know exactly what a program is going to do before they run it\&. This also allows you to audit the software for security holes (none have been found so far)\&. +.PP +Source code also allows you to port Nmap (which includes Ncat) to new platforms, fix bugs, and add new features\&. You are highly encouraged to send your changes to +<dev@nmap\&.org> +for possible incorporation into the main distribution\&. By sending these changes to Fyodor or one of the Insecure\&.Org development mailing lists, it is assumed that you are offering the Nmap Project (Nmap Software LLC) the unlimited, non\-exclusive right to reuse, modify, and relicense the code\&. Nmap will always be available open source, +but this is important because the inability to relicense code has caused devastating problems for other Free Software projects (such as KDE and NASM)\&. We also occasionally relicense the code to third parties as discussed in the Nmap man page\&. If you wish to specify special license conditions of your contributions, just say so when you send them\&. +.SS "No Warranty" +.PP +This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE\&. See the Nmap Public Source License for more details at +\m[blue]\fB\%https://nmap.org/npsl/\fR\m[], or in the +LICENSE +file included with Nmap\&. +.SS "Inappropriate Usage" +.PP +Ncat should never be installed with special privileges (e\&.g\&. suid root)\&. +That would open up a major security vulnerability as other users on the system (or attackers) could use it for privilege escalation\&. +.SS "Third\-Party Software" +.PP +This product includes software developed by the +\m[blue]\fBApache Software Foundation\fR\m[]\&\s-2\u[2]\d\s+2\&. A modified version of the +\m[blue]\fBLibpcap portable packet capture library\fR\m[]\&\s-2\u[3]\d\s+2 +is distributed along with Ncat\&. The Windows version of Ncat utilized the Libpcap\-derived +\m[blue]\fBNpcap library\fR\m[]\&\s-2\u[4]\d\s+2 +instead\&. Certain raw networking functions use the +\m[blue]\fBLibdnet\fR\m[]\&\s-2\u[5]\d\s+2 +networking library, which was written by Dug Song\&. +A modified version is distributed with Ncat\&. Ncat can optionally link with the +\m[blue]\fBOpenSSL cryptography toolkit\fR\m[]\&\s-2\u[6]\d\s+2 +for SSL version detection support\&. All of the third\-party software described in this paragraph is freely redistributable under BSD\-style software licenses\&. +.SH "NOTES" +.IP " 1." 4 +Creative Commons Attribution License +.RS 4 +\%http://creativecommons.org/licenses/by/3.0/ +.RE +.IP " 2." 4 +Apache Software Foundation +.RS 4 +\%http://www.apache.org +.RE +.IP " 3." 4 +Libpcap portable packet capture library +.RS 4 +\%http://www.tcpdump.org +.RE +.IP " 4." 4 +Npcap library +.RS 4 +\%https://npcap.com +.RE +.IP " 5." 4 +Libdnet +.RS 4 +\%http://libdnet.sourceforge.net +.RE +.IP " 6." 4 +OpenSSL cryptography toolkit +.RS 4 +\%http://www.openssl.org +.RE |