Change ASPSessionID

[Joseph Shoe]

How do you change the ASPSessionID during a web session? I have an ASP
application in SSL. The first screen is a login screen, which requests user
id and password. An ASPSessionID is assigned for this page. Once the user
is authenticated by valid id/pwd, the second page starts the real
applicaiton. I want to change the ASPSessionID to be different from the
first login page, which was issued to an unauthenticated user. How do I do
that in ASP?

Thanks.
Joseph

[Tim Williams]

How about this scenario (multi-user PC) ?

1. User A attempts to log in, has no valid UN/PW but is able to grab the
value of the SessionId using (eg.) a js bookmarklet
2. User B logs in (on the same PC, before the session has timed out) and
begins using the application.

Can user A now access user B's session from another PC by setting a session
cookie to the same value they captured in Step 1 ? Seems to me that they
they might be able to...

--
Tim Williams
Palo Alto, CA
"Aaron Bertrand [SQL Server MVP]" <te*****@dnartr eb.noraa> wrote in message
news:uG******** ******@TK2MSFTN GP15.phx.gbl...

As I understand it, the ASPSessionID is used as a reference to all session variables maintained by ASP for each session. If anybody gains the
sessionID
from the unauthenticated screen, they will be able to use it to gain
access
to the sesion data I maintain during the subsequent authenticated

session.
Can you please demonstrate either of these two parts.

I have never seen a demonstration of guessing or sniffing a currently active sessionID, much less impersonating it.

"9. Force Server-side Session ID Creation
The server should never assume the value of a session ID that is given
before login. Instead the server mush create a unique session ID after
the
user successfully authenticates (a strict web application). This will
foil
session fixatin attacks."
I think you're chasing the wrong squirrel up the wrong tree. I think they
are talking about authenticating here via e.g. Windows Authentication, not
some silly login form in your own app. Your own web application is only

as strong as you make it.

Do you understand the statement that changing the SessionID is not going to make your application any more secure?

[Adrienne]

Gazing into my crystal ball I observed "Tim Williams" <saxifrax at
pacbell dot net> writing in news:eE******** ******@TK2MSFTN GP10.phx.gbl:

How about this scenario (multi-user PC) ?

1. User A attempts to log in, has no valid UN/PW but is able to grab
the value of the SessionId using (eg.) a js bookmarklet
2. User B logs in (on the same PC, before the session has timed out)
and begins using the application.

Can user A now access user B's session from another PC by setting a
session cookie to the same value they captured in Step 1 ? Seems to me
that they they might be able to...

The problem is that if someone really wants to break in, they will. And
sometimes, things just happen. For example, there's a PC at the bank so
you can look up your account information online. Sometimes (a lot of
times), people forget to logout when they're done, and the bank doesn't
automatically log you out for inactivity for 5 minutes. Someone can get
a lot of information in 5 minutes.

--
Adrienne Boswell
http://www.cavalcade-of-coding.info
Please respond to the group so others can share

[Tim Williams]

If someone really wants to break into your car they will.
Doesn't mean it's not worth locking your doors.

Tim.

--
Tim Williams
Palo Alto, CA
"Adrienne" <ar********@sbc global.net> wrote in message
news:Xn******** *************** *****@207.115.6 3.158...

Gazing into my crystal ball I observed "Tim Williams" <saxifrax at
pacbell dot net> writing in news:eE******** ******@TK2MSFTN GP10.phx.gbl:

How about this scenario (multi-user PC) ?

1. User A attempts to log in, has no valid UN/PW but is able to grab
the value of the SessionId using (eg.) a js bookmarklet
2. User B logs in (on the same PC, before the session has timed out)
and begins using the application.

Can user A now access user B's session from another PC by setting a
session cookie to the same value they captured in Step 1 ? Seems to me
that they they might be able to...

The problem is that if someone really wants to break in, they will. And
sometimes, things just happen. For example, there's a PC at the bank so
you can look up your account information online. Sometimes (a lot of
times), people forget to logout when they're done, and the bank doesn't
automatically log you out for inactivity for 5 minutes. Someone can get
a lot of information in 5 minutes.

--
Adrienne Boswell
http://www.cavalcade-of-coding.info
Please respond to the group so others can share

[Aaron Bertrand [SQL Server MVP]]

> Can user A now access user B's session from another PC by setting a

session
cookie to the same value they captured in Step 1 ?

No, because (a) I don't think JS has the ability to read a server-side
sessionID, even if the author of the web page would put it there, and (b)
you can't access user B's session just by changing your cookie.

[Tim Williams]

alert (document.cooki e);

works if I remember correctly. The cookie can be set in similar
fashion (eg) using a js bookmarklet. Since you would then have the
"correct" SessionId why couldn't you access the other session?

Tim.
"Aaron Bertrand [SQL Server MVP]" <te*****@dnartr eb.noraa> wrote in
message news:u1******** ******@TK2MSFTN GP10.phx.gbl...

Can user A now access user B's session from another PC by setting a
session
cookie to the same value they captured in Step 1 ?

No, because (a) I don't think JS has the ability to read a
server-side sessionID, even if the author of the web page would put
it there, and (b) you can't access user B's session just by changing
your cookie.

[Aaron Bertrand [SQL Server MVP]]

> works if I remember correctly. The cookie can be set in similar fashion

(eg) using a js bookmarklet. Since you would then have the "correct"
SessionId

Well, let me know exactly how you plan to do it. See if you can set a
session variable for a browser on one machine, get the cookie without having
access to the ASP file(s) directly, then use another machine and fiddle with
the cookie however you see fit, and see if you can retrieve the session
variable on machine B that was set for the user on machine A.

My experiments in the past have proved to me that it will not work.

In any case, even if the above were to work, a malicious user would have to
have access to the first user's session to get their sessionID at all, and
if they can do that, why not just continue their session?

[Tim Williams]

So said so done. Exactly as described.

Opened login page on PC1, copied sessionid cookie name/value to text
file. Then logged in on PC1 using a known UN/PW.

Few minutes later on PC2, used an "edit cookie" bookmarklet to create
the session cookie from PC1, and was able to bypass the login page and
go directly to a "protected" page. This page would normally (on
seeing there is no "logged in=yes" session variable) redirect me to
the login page but in this case the session from PC1 is referenced due
to the copied cookie.

Bookmarklet for editing the session cookie was from here:
http://visitjesper.homeip.net/bookmarklets.html

However unlikely the scenario, it has to be admitted to be possible
(and not that difficult either). That is the only point I'm trying to
make here.
Easy to prevent just by adding another session cookie on login and
checking for both that *and* the session variable, rather than relying
only on the session variable.

Tim.
"Aaron Bertrand [SQL Server MVP]" <te*****@dnartr eb.noraa> wrote in
message news:uU******** ******@TK2MSFTN GP14.phx.gbl...

works if I remember correctly. The cookie can be set in similar
fashion (eg) using a js bookmarklet. Since you would then have the
"correct" SessionId

Well, let me know exactly how you plan to do it. See if you can set
a session variable for a browser on one machine, get the cookie
without having access to the ASP file(s) directly, then use another
machine and fiddle with the cookie however you see fit, and see if
you can retrieve the session variable on machine B that was set for
the user on machine A.

My experiments in the past have proved to me that it will not work.

In any case, even if the above were to work, a malicious user would
have to have access to the first user's session to get their
sessionID at all, and if they can do that, why not just continue
their session?

[Michael D. Kersey]

Joseph Shoe wrote:

How do you change the ASPSessionID during a web session? I have an ASP
application in SSL. The first screen is a login screen, which requests user
id and password. An ASPSessionID is assigned for this page. Once the user
is authenticated by valid id/pwd, the second page starts the real
applicaiton. I want to change the ASPSessionID to be different from the
first login page, which was issued to an unauthenticated user. How do I do
that in ASP?

Don't use ASP sessions. Instead create and maintain your own "session
ID" passed in the querystring or in hidden field(s). Then you can change
it wherever and whenever you wish, even with each page submission.

[Aaron Bertrand [SQL Server MVP]]

> However unlikely the scenario, it has to be admitted to be possible

(and not that difficult either). That is the only point I'm trying to
make here.
I wasn't able to reproduce, but I'll take your word for it for now.
Easy to prevent just by adding another session cookie on login and
checking for both that *and* the session variable, rather than relying
only on the session variable.

Which is what I suggested further up in the thread (I also still didn't get
a decent answer to my question, what would be accomplished by changing the
sessionID).

[Joseph Shoe]

Thanks, Tim. Your description is mostly correct. One clarificaiton: when
PC2 is able to get to the protected page of PC1 using the same SessionID, the
session variable "logged in" would be yes for PC2, as seen by PC1. PC2 will
not be redirected to the login page.

Your suggestion of using a second session cookie is a sound one. I was
merely looking for a shortcut. Afterall, it shouldn't be much difficult for
ASP to provide an API to change the SessionID.

"Tim Williams" wrote:

So said so done. Exactly as described.

Opened login page on PC1, copied sessionid cookie name/value to text
file. Then logged in on PC1 using a known UN/PW.

Few minutes later on PC2, used an "edit cookie" bookmarklet to create
the session cookie from PC1, and was able to bypass the login page and
go directly to a "protected" page. This page would normally (on
seeing there is no "logged in=yes" session variable) redirect me to
the login page but in this case the session from PC1 is referenced due
to the copied cookie.

Bookmarklet for editing the session cookie was from here:
http://visitjesper.homeip.net/bookmarklets.html

However unlikely the scenario, it has to be admitted to be possible
(and not that difficult either). That is the only point I'm trying to
make here.
Easy to prevent just by adding another session cookie on login and
checking for both that *and* the session variable, rather than relying
only on the session variable.

Tim.
"Aaron Bertrand [SQL Server MVP]" <te*****@dnartr eb.noraa> wrote in
message news:uU******** ******@TK2MSFTN GP14.phx.gbl...

works if I remember correctly. The cookie can be set in similar
fashion (eg) using a js bookmarklet. Since you would then have the
"correct" SessionId

Well, let me know exactly how you plan to do it. See if you can set
a session variable for a browser on one machine, get the cookie
without having access to the ASP file(s) directly, then use another
machine and fiddle with the cookie however you see fit, and see if
you can retrieve the session variable on machine B that was set for
the user on machine A.

My experiments in the past have proved to me that it will not work.

In any case, even if the above were to work, a malicious user would
have to have access to the first user's session to get their
sessionID at all, and if they can do that, why not just continue
their session?