<s>
Web-based	B-Protocol
SSH	I-Protocol
refers	O
to	O
the	O
ability	O
to	O
access	O
Secure	B-Protocol
Shell	I-Protocol
(	O
SSH	B-Protocol
)	O
servers	O
through	O
a	O
web	B-Application
browser	I-Application
.	O
</s>
<s>
SSH	B-Protocol
is	O
a	O
secure	O
network	O
protocol	O
that	O
is	O
commonly	O
used	O
to	O
remotely	O
control	O
servers	O
,	O
network	O
devices	O
,	O
and	O
other	O
devices	O
.	O
</s>
<s>
With	O
web-based	B-Protocol
SSH	I-Protocol
,	O
users	O
can	O
access	O
and	O
manage	O
these	O
devices	O
using	O
a	O
standard	O
web	B-Application
browser	I-Application
,	O
without	O
the	O
need	O
to	O
install	O
any	O
additional	O
software	O
.	O
</s>
<s>
Web-based	B-Protocol
SSH	I-Protocol
clients	O
are	O
typically	O
implemented	O
using	O
JavaScript	B-Language
and	O
either	O
Ajax	B-General_Concept
or	O
WebSockets	B-Protocol
.	O
</s>
<s>
These	O
clients	O
communicate	O
with	O
the	O
SSH	B-Protocol
server	O
through	O
a	O
proxy	B-Application
,	O
which	O
allows	O
them	O
to	O
bypass	O
firewalls	B-Application
and	O
other	O
network	O
security	O
measures	O
that	O
may	O
block	O
SSH	B-Protocol
traffic	O
.	O
</s>
<s>
This	O
makes	O
web-based	B-Protocol
SSH	I-Protocol
a	O
convenient	O
and	O
secure	O
way	O
to	O
access	O
remote	O
servers	O
and	O
devices	O
from	O
any	O
location	O
with	O
an	O
internet	O
connection	O
.	O
</s>
<s>
Web-based	B-Protocol
SSH	I-Protocol
is	O
useful	O
for	O
a	O
variety	O
of	O
purposes	O
,	O
including	O
system	O
administration	O
,	O
network	O
management	O
,	O
and	O
remote	O
development	O
.	O
</s>
<s>
Web-based	B-Protocol
SSH	I-Protocol
clients	O
are	O
applications	O
that	O
allow	O
users	O
to	O
access	O
Secure	B-Protocol
Shell	I-Protocol
(	O
SSH	B-Protocol
)	O
servers	O
through	O
a	O
web	B-Application
browser	I-Application
.	O
</s>
<s>
They	O
consist	O
of	O
two	O
main	O
parts	O
:	O
a	O
client-side	O
component	O
,	O
which	O
is	O
typically	O
implemented	O
using	O
JavaScript	B-Language
and	O
dynamic	B-General_Concept
HTML	I-General_Concept
,	O
and	O
a	O
server-side	O
or	O
web	O
application	O
component	O
,	O
which	O
is	O
typically	O
implemented	O
on	O
an	O
application	B-Application
server	I-Application
.	O
</s>
<s>
The	O
client-side	O
component	O
captures	O
keystrokes	O
,	O
transmits	O
messages	O
to	O
and	O
from	O
the	O
server	O
,	O
and	O
displays	O
the	O
results	O
in	O
the	O
user	O
's	O
web	B-Application
browser	I-Application
.	O
</s>
<s>
The	O
server-side	O
component	O
processes	O
incoming	O
requests	O
and	O
forwards	O
keyboard	O
events	O
to	O
a	O
secure	B-Protocol
shell	I-Protocol
client	O
that	O
communicates	O
with	O
the	O
connected	O
SSH	B-Protocol
server	O
.	O
</s>
<s>
Terminal	O
output	O
is	O
either	O
passed	O
to	O
the	O
client	O
,	O
where	O
it	O
is	O
converted	O
into	O
HTML	O
using	O
JavaScript	B-Language
,	O
or	O
it	O
is	O
translated	O
into	O
HTML	O
by	O
the	O
server	O
before	O
it	O
is	O
transmitted	O
to	O
the	O
client	O
.	O
</s>
<s>
Web-based	B-Protocol
SSH	I-Protocol
servers	O
can	O
use	O
either	O
client-side	O
or	O
server-side	O
terminal	O
emulation	O
.	O
</s>
<s>
Client-side	O
terminal	O
emulation	O
transmits	O
the	O
raw	O
terminal	O
output	O
from	O
the	O
SSH	B-Protocol
server	O
directly	O
to	O
the	O
client	O
,	O
which	O
has	O
the	O
advantage	O
of	O
offloading	O
the	O
process	O
of	O
translating	O
terminal	O
output	O
into	O
HTML	O
onto	O
the	O
client	O
.	O
</s>
<s>
However	O
,	O
it	O
can	O
be	O
limited	O
by	O
the	O
capabilities	O
of	O
JavaScript	B-Language
and	O
can	O
use	O
a	O
significant	O
amount	O
of	O
the	O
client	O
's	O
CPU	O
and	O
memory	O
.	O
</s>
<s>
This	O
method	O
has	O
the	O
advantage	O
of	O
keeping	O
the	O
state	O
of	O
the	O
terminal	O
persistent	O
even	O
if	O
the	O
user	O
connects	O
to	O
their	O
existing	O
session	O
from	O
a	O
different	O
web	B-Application
browser	I-Application
,	O
but	O
it	O
can	O
use	O
more	O
CPU	O
and	O
memory	O
on	O
the	O
server	O
.	O
</s>
<s>
The	O
main	O
advantages	O
of	O
web-based	B-Protocol
SSH	I-Protocol
can	O
be	O
summarized	O
as	O
follows	O
:	O
</s>
<s>
Accessibility	O
:	O
Web-based	B-Protocol
SSH	I-Protocol
as	O
described	O
in	O
this	O
article	O
requires	O
no	O
local	O
installation	O
of	O
client	O
software	O
.	O
</s>
<s>
It	O
is	O
thus	O
possible	O
to	O
access	O
SSH	B-Protocol
servers	O
through	O
a	O
web	B-Application
browser	I-Application
from	O
anywhere	O
.	O
</s>
<s>
As	O
communication	O
is	O
based	O
on	O
HTTP	B-Protocol
or	O
HTTPS	B-Protocol
it	O
is	O
also	O
possible	O
to	O
access	O
SSH	B-Protocol
servers	O
from	O
behind	O
a	O
firewall	B-Application
or	O
proxy	B-Application
that	O
restricts	O
Internet	O
access	O
to	O
only	O
ports	O
80	O
(	O
HTTP	B-Protocol
)	O
or	O
443	O
(	O
HTTPS	B-Protocol
)	O
.	O
</s>
<s>
Anonymous	O
Access	O
:	O
As	O
SSH	B-Protocol
access	O
is	O
tunneled	O
through	O
an	O
intermediary	O
web	B-Application
application	I-Application
server	I-Application
it	O
is	O
this	O
server	O
which	O
actually	O
communicates	O
with	O
the	O
SSH	B-Protocol
server	O
.	O
</s>
<s>
This	O
means	O
that	O
the	O
SSH	B-Protocol
server	O
will	O
only	O
be	O
aware	O
of	O
the	O
IP	B-Protocol
address	I-Protocol
of	O
the	O
web	B-Application
application	I-Application
server	I-Application
,	O
keeping	O
the	O
actual	O
client	O
's	O
IP	B-Protocol
address	I-Protocol
hidden	O
.	O
</s>
<s>
Auditability	O
:	O
Because	O
all	O
communication	O
between	O
the	O
client	O
and	O
the	O
SSH	B-Protocol
server	O
must	O
pass	O
through	O
the	O
web	B-Application
application	I-Application
server	I-Application
this	O
communication	O
can	O
be	O
logged	O
.	O
</s>
<s>
The	O
situation	O
is	O
exactly	O
the	O
same	O
as	O
with	O
traditional	O
SSH	B-Protocol
server	O
.	O
</s>
<s>
Resuming	O
Sessions	O
:	O
Some	O
web-based	B-Protocol
SSH	I-Protocol
implementations	O
allow	O
the	O
user	O
to	O
resume	O
their	O
SSH	B-Protocol
sessions	O
after	O
being	O
disconnected	O
.	O
</s>
<s>
This	O
is	O
not	O
possible	O
with	O
a	O
traditional	O
SSH	B-Protocol
client	O
.	O
</s>
<s>
Embeddable	O
:	O
Web-based	B-Protocol
SSH	I-Protocol
implementations	O
can	O
be	O
embedded	O
into	O
any	O
web	O
page	O
allowing	O
them	O
to	O
be	O
integrated	O
into	O
other	O
web-based	O
applications	O
.	O
</s>
<s>
Unique	O
Features	O
:	O
Many	O
web-based	B-Protocol
SSH	I-Protocol
tools	O
have	O
unique	O
features	O
such	O
as	O
the	O
ability	O
to	O
share	O
terminals	O
with	O
other	O
users	O
,	O
can	O
display	O
images	O
within	O
terminals	O
,	O
and	O
other	O
useful	O
capabilities	O
.	O
</s>
<s>
The	O
following	O
issues	O
have	O
to	O
be	O
considered	O
and	O
are	O
important	O
when	O
using	O
a	O
web-based	B-Protocol
SSH	I-Protocol
client	O
:	O
</s>
<s>
Security	O
:	O
It	O
is	O
important	O
to	O
make	O
sure	O
that	O
HTTPS	B-Protocol
is	O
used	O
when	O
communicating	O
with	O
the	O
web	B-Application
application	I-Application
server	I-Application
.	O
</s>
<s>
Otherwise	O
all	O
data	O
being	O
sent	O
would	O
be	O
readable	O
by	O
use	O
of	O
simple	O
packet	B-Protocol
sniffers	I-Protocol
which	O
could	O
reveal	O
sensitive	O
information	O
.	O
</s>
<s>
Trust	O
:	O
The	O
data	O
being	O
sent	O
to	O
the	O
web	B-Application
application	I-Application
server	I-Application
is	O
decrypted	O
there	O
.	O
</s>
<s>
This	O
is	O
necessary	O
in	O
order	O
to	O
forward	O
the	O
issued	O
commands	O
to	O
the	O
actual	O
SSH	B-Protocol
server	O
.	O
</s>
<s>
Even	O
though	O
the	O
operators	O
of	O
web-based	B-Protocol
SSH	I-Protocol
solutions	O
usually	O
do	O
n't	O
log	O
sensitive	O
data	O
the	O
data	O
is	O
theoretically	O
available	O
to	O
them	O
in	O
plain	O
form	O
.	O
</s>
<s>
It	O
is	O
unlikely	O
that	O
this	O
will	O
cause	O
a	O
security	O
issue	O
when	O
the	O
web	B-Application
application	I-Application
server	I-Application
and	O
the	O
SSH	B-Protocol
server	O
are	O
run	O
on	O
the	O
same	O
server	O
or	O
are	O
controlled	O
by	O
the	O
same	O
entity	O
.	O
</s>
<s>
Tunneling	O
:	O
Unlike	O
most	O
traditional	O
,	O
application	O
based	O
SSH	B-Protocol
clients	O
,	O
web-based	B-Protocol
SSH	I-Protocol
clients	O
are	O
unable	O
to	O
tunnel	O
(	O
"	O
forward	O
"	O
)	O
TCP	B-Protocol
traffic	O
.	O
</s>
<s>
For	O
example	O
,	O
running	O
an	O
X	B-Operating_System
session	O
over	O
a	O
web-based	B-Protocol
SSH	I-Protocol
session	O
is	O
not	O
possible	O
.	O
</s>
<s>
Google	O
's	O
Secure	B-Protocol
Shell	I-Protocol
extension	O
for	O
Chrome	O
and	O
Chromium	O
pairs	O
the	O
JavaScript	B-Language
hterm	O
terminal	O
emulator	O
with	O
OpenSSH	B-Language
client	O
code	O
running	O
on	O
Native	B-Application
Client	I-Application
.	O
</s>
<s>
The	O
Secure	B-Protocol
Shell	I-Protocol
extension	O
works	O
with	O
non-Google	O
HTTP-to-SSH	O
proxies	O
via	O
proxy	B-Application
hooks	O
,	O
and	O
third-party	O
application	O
nassh-relay	O
can	O
use	O
those	O
hooks	O
to	O
enable	O
the	O
Secure	B-Protocol
Shell	I-Protocol
extension	O
to	O
establish	O
an	O
SSH	B-Protocol
connection	O
over	O
XMLHttpRequest	B-Protocol
or	O
WebSocket	B-Protocol
transport	O
.	O
</s>
<s>
shellinabox	O
operates	O
as	O
a	O
stand-alone	O
service	O
or	O
in	O
conjunction	O
with	O
nginx	B-Operating_System
to	O
provide	O
HTTPS	B-Protocol
access	O
to	O
a	O
login	O
shell	O
,	O
and	O
is	O
packaged	O
for	O
Debian	O
and	O
RedHat	O
-derived	O
Linux	B-Application
distributions	O
.	O
</s>
<s>
Users	O
connect	O
to	O
a	O
centralized	O
server	O
over	O
HTTPS	B-Protocol
and	O
SSH	B-Protocol
connections	O
are	O
proxied	O
through	O
a	O
secure	O
WebSocket	B-Protocol
transport	O
.	O
</s>
<s>
FireSSH	O
is	O
a	O
browser	B-Application
plug-in	O
that	O
works	O
on	O
Firefox	O
ESR	O
and	O
Waterfox	O
.	O
</s>
