1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
|
.TH dropbear 8
.SH NAME
dropbear \- lightweight SSH server
.SH SYNOPSIS
.B dropbear
[flag arguments] [\-b
.I banner\fR]
[\-r
.I hostkeyfile\fR] [\-p
.IR [address:]port ]
.SH DESCRIPTION
.B dropbear
is a small SSH server
.SH OPTIONS
.TP
.B \-b \fIbanner
bannerfile.
Display the contents of the file
.I banner
before user login (default: none).
.TP
.B \-r \fIhostkey
Use the contents of the file
.I hostkey
for the SSH hostkey.
This file is generated with
.BR dropbearkey (1)
or automatically with the '-R' option. See "Host Key Files" below.
.TP
.B \-R
Generate hostkeys automatically. See "Host Key Files" below.
.TP
.B \-F
Don't fork into background.
.TP
.B \-E
Log to standard error rather than syslog.
.TP
.B \-m
Don't display the message of the day on login.
.TP
.B \-w
Disallow root logins.
.TP
.B \-s
Disable password logins.
.TP
.B \-g
Disable password logins for root.
.TP
.B \-j
Disable local port forwarding.
.TP
.B \-k
Disable remote port forwarding.
.TP
.B \-p \fI[address:]port
Listen on specified
.I address
and TCP
.I port.
If just a port is given listen
on all addresses.
up to 10 can be specified (default 22 if none specified).
.TP
.B \-i
Service program mode.
Use this option to run
.B dropbear
under TCP/IP servers like inetd, tcpsvd, or tcpserver.
In program mode the \-F option is implied, and \-p options are ignored.
.TP
.B \-P \fIpidfile
Specify a pidfile to create when running as a daemon. If not specified, the
default is /var/run/dropbear.pid
.TP
.B \-a
Allow remote hosts to connect to forwarded ports.
.TP
.B \-W \fIwindowsize
Specify the per-channel receive window buffer size. Increasing this
may improve network performance at the expense of memory use. Use -h to see the
default buffer size.
.TP
.B \-K \fItimeout_seconds
Ensure that traffic is transmitted at a certain interval in seconds. This is
useful for working around firewalls or routers that drop connections after
a certain period of inactivity. The trade-off is that a session may be
closed if there is a temporary lapse of network connectivity. A setting
if 0 disables keepalives. If no response is received for 3 consecutive keepalives the connection will be closed.
.TP
.B \-I \fIidle_timeout
Disconnect the session if no traffic is transmitted or received for \fIidle_timeout\fR seconds.
.TP
.B \-V
Print the version
.SH FILES
.TP
Authorized Keys
~/.ssh/authorized_keys can be set up to allow remote login with a RSA,
ECDSA, or DSS
key. Each line is of the form
.TP
[restrictions] ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAIgAsp... [comment]
and can be extracted from a Dropbear private host key with "dropbearkey -y". This is the same format as used by OpenSSH, though the restrictions are a subset (keys with unknown restrictions are ignored).
Restrictions are comma separated, with double quotes around spaces in arguments.
Available restrictions are:
.TP
.B no-port-forwarding
Don't allow port forwarding for this connection
.TP
.B no-agent-forwarding
Don't allow agent forwarding for this connection
.TP
.B no-X11-forwarding
Don't allow X11 forwarding for this connection
.TP
.B no-pty
Disable PTY allocation. Note that a user can still obtain most of the
same functionality with other means even if no-pty is set.
.TP
.B command="\fIforced_command\fR"
Disregard the command provided by the user and always run \fIforced_command\fR.
The authorized_keys file and its containing ~/.ssh directory must only be
writable by the user, otherwise Dropbear will not allow a login using public
key authentication.
.TP
Host Key Files
Host key files are read at startup from a standard location, by default
/etc/dropbear/dropbear_dss_host_key, /etc/dropbear/dropbear_rsa_host_key, and
/etc/dropbear/dropbear_ecdsa_host_key
or specified on the commandline with -r. These are of the form generated
by dropbearkey. The -R option can be used to automatically generate keys
in the default location - keys will be generated after startup when the first
connection is established. This had the benefit that the system /dev/urandom
random number source has a better chance of being securely seeded.
.TP
Message Of The Day
By default the file /etc/motd will be printed for any login shell (unless
disabled at compile-time). This can also be disabled per-user
by creating a file ~/.hushlogin .
.SH ENVIRONMENT VARIABLES
Dropbear sets the standard variables USER, LOGNAME, HOME, SHELL, PATH, and TERM.
The variables below are set for sessions as appropriate.
.TP
.B SSH_TTY
This is set to the allocated TTY if a PTY was used.
.TP
.B SSH_CONNECTION
Contains "<remote_ip> <remote_port> <local_ip> <local_port>".
.TP
.B DISPLAY
Set X11 forwarding is used.
.TP
.B SSH_ORIGINAL_COMMAND
If a 'command=' authorized_keys option was used, the original command is specified
in this variable. If a shell was requested this is set to an empty value.
.TP
.B SSH_AUTH_SOCK
Set to a forwarded ssh-agent connection.
.SH NOTES
Dropbear only supports SSH protocol version 2.
.SH AUTHOR
Matt Johnston (matt@ucc.asn.au).
.br
Gerrit Pape (pape@smarden.org) wrote this manual page.
.SH SEE ALSO
dropbearkey(1), dbclient(1), dropbearconvert(1)
.P
https://matt.ucc.asn.au/dropbear/dropbear.html
|
