1EXTCAP(4)               The Wireshark Network Analyzer               EXTCAP(4)
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NAME

6       extcap - The extcap interface
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DESCRIPTION

9       The extcap interface is a versatile plugin interface that allows
10       external binaries to act as capture interfaces directly in Wireshark.
11       It is used in scenarios, where the source of the capture is not a
12       traditional capture model (live capture from an interface, from a pipe,
13       from a file, etc). The typical example is connecting esoteric hardware
14       of some kind to the main Wireshark application.
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16       Without extcap, a capture can always be achieved by directly writing to
17       a capture file:
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19           the-esoteric-binary --the-strange-flag --interface=stream1 --file dumpfile.pcap &
20           wireshark dumpfile.pcap
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22       but the extcap interface allows for such a connection to be easily
23       established and configured using the Wireshark GUI.
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25       The extcap subsystem is made of multiple extcap binaries that are
26       automatically called by the GUI in a row. In the following chapters we
27       will refer to them as "the extcaps".
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29       Extcaps may be any binary or script within the extcap directory. Please
30       note, that scripts need to be executable without prefacing a script
31       interpreter before the call.
32
33       WINDOWS USER: Because of restrictions directly calling the script may
34       not always work.  In such a case, a batch file may be provided, which
35       then in turn executes the script. Please refer to doc/extcap_example.py
36       for more information.
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38       When Wireshark launches an extcap, it automatically adds its
39       installation path (c:\Program Files\Wireshark\) to the DLL search path
40       so that the extcap library dependencies can be found (it is not
41       designed to be launched by hand).  This is done on purpose. There
42       should only be extcap programs (executable, python scripts, ...) in the
43       extcap folder to reduce the startup time and not have Wireshark trying
44       to execute other file types.
45

GRAMMAR ELEMENTS

47       Grammar elements:
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49       arg (options)
50           argument for CLI calling
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52       number
53           Reference # of argument for other values, display order
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55       call
56           Literal argument to call (--call=...)
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58       display
59           Displayed name
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61       default
62           Default value, in proper form for type
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64       range
65           Range of valid values for UI checking (min,max) in proper form
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67       type
68           Argument type for UI filtering for raw, or UI type for selector:
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70               integer
71               unsigned
72               long (may include scientific / special notation)
73               float
74               selector (display selector table, all values as strings)
75               boolean (display checkbox)
76               radio (display group of radio buttons with provided values, all values as strings)
77               fileselect (display a dialog to select a file from the filesystem, value as string)
78               multicheck (display a textbox for selecting multiple options, values as strings)
79               password (display a textbox with masked text)
80               timestamp (display a calendar)
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82       value (options)
83               Values for argument selection
84               arg     Argument # this value applies to
85

EXAMPLES

87       Example 1:
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89           arg {number=0}{call=--channel}{display=Wi-Fi Channel}{type=integer}{required=true}
90           arg {number=1}{call=--chanflags}{display=Channel Flags}{type=radio}
91           arg {number=2}{call=--interface}{display=Interface}{type=selector}
92           value {arg=0}{range=1,11}
93           value {arg=1}{value=ht40p}{display=HT40+}
94           value {arg=1}{value=ht40m}{display=HT40-}
95           value {arg=1}{value=ht20}{display=HT20}
96           value {arg=2}{value=wlan0}{display=wlan0}
97
98       Example 2:
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100           arg {number=0}{call=--usbdevice}{USB Device}{type=selector}
101           value {arg=0}{call=/dev/sysfs/usb/foo/123}{display=Ubertooth One sn 1234}
102           value {arg=0}{call=/dev/sysfs/usb/foo/456}{display=Ubertooth One sn 8901}
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104       Example 3:
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106           arg {number=0}{call=--usbdevice}{USB Device}{type=selector}
107           arg {number=1}{call=--server}{display=IP address for log server}{type=string}{validation=(?:\d{1,3}\.){3}\d{1,3}}
108           flag {failure=Permission denied opening Ubertooth device}
109
110       Example 4:
111           arg {number=0}{call=--username}{display=Username}{type=string}
112           arg {number=1}{call=--password}{display=Password}{type=password}
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114       Example 5:
115           arg {number=0}{call=--start}{display=Start Time}{type=timestamp}
116           arg {number=1}{call=--end}{display=End Time}{type=timestamp}
117

Security awareness

119       - Users running wireshark as root, we can't save you
120       - Dumpcap retains suid/setgid and group+x permissions to allow users in
121       wireshark group only
122       - Third-party capture programs run w/ whatever privs they're installed
123       with
124       - If an attacker can write to a system binary directory, we're game
125       over anyhow
126       - Reference the folders tab in the wireshark->about information, to see
127       from which directory extcap is being run
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SEE ALSO

130       wireshark(1), tshark(1), dumpcap(1), androiddump(1), sshdump(1),
131       randpktdump(1)
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NOTES

134       Extcap is feature of Wireshark.  The latest version of Wireshark can be
135       found at <https://www.wireshark.org>.
136
137       HTML versions of the Wireshark project man pages are available at:
138       <https://www.wireshark.org/docs/man-pages>.
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1423.4.5                             2021-05-27                         EXTCAP(4)
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