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Date: Fri, 04 Jul 2014 11:04:59 +0200
From: perox@freenet.de
Subject: ANSI Escape sequences in PAM message
To: freebsd-stable@freebsd.org
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Hi,
I recently played around with a custom PAM module for user authentication v=
ia
ssh. During the authentication process I want to display various messages w=
hich I
am able to do using a conv() call passing my messages. If the message is si=
mple
everything works as expected.
When I use terminal/ANSI escape codes (e.g. something like =0033[40;37;1m t=
o=20
provide colors) however, the output is only correct when I set the pam mess=
age type
PAM_PROMPT_ECHO_ON. If I choose PAM_TEXT_INFO or PAM_ERROR_MSG=20
the escape sequences have no effect and are printed literally. Using=20
PAM_PROMPT_ECHO_ON as message type is no solution as it requires the=20
user to press a key after each message. Is this a bug or a feature? I could=
imagine=20
this being a security feature, but then, why would one message type allow i=
t?=20
Skimming through the code of libpam and openssh didn't help. Is there perha=
ps=20
a flag or an option to ssh which forbids some things I try to use?
Under Ubuntu and RedHat (which don't use openpam but an own PAM
implementation) everything works as expected. I am using 10-STABLE=20
but 9.2 shows the same behavior.
Thanks!
--
My code looks similar to this:
int style =3D PAM_PROMPT_ECHO_ON;
// don't work
//int style =3D PAM_TEXT_INFO; =
=20
//int style =3D PAM_ERROR_MSG; =20
r =3D pam_get_item(pamhg, PAM_CONV, &convp);
=
=20
conv =3D (const struct pam_conv *)convp;
vsnprintf(msgbuf, PAM_MAX_MSG_SIZE, fmt, ap);
msg.msg_style =3D style;
msg.msg =3D msgbuf;
msgp =3D &msg; =20
r =3D (conv->conv)(1, &msgp, &rsp, conv->appdata_ptr);
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