Hi folks,
There's been a couple of requests to add a switch to pam_tty_audit to
*not* log passwords when logging user commands.
Most commands are entered one line at a time and processed as complete
lines in non-canonical mode. Commands that interactively require a
password, enter canonical mode to do this. This feature (icanon) can be
used to avoid logging passwords by audit while still logging the rest of
the command.
Adding a member to the struct audit_tty_status passed in by
pam_tty_audit allows control of canonical mode per task.
Note: The original patch added a sysctl to control this system-wide,
which did work fine as expected, but it was recommended to keep the
switch with the module invocation, turning it into a per-task switch.
This method has also been tested.
Here are two patches, the first to pam to add the switch to
the pam_tty_audit module. The second is to the kernel to add the
necessary bits in audit and tty:
pam_tty_audit: add an option to control logging of passwords
tty: add an option to control logging of passwords with pam_tty_audit
Please have a quick look and with some initial feedback I'll post them
upstream. I'd normally use git send-email and in-line it, but since
they were patches for two different entities, thought it best to do it
this way instead.
- RGB
--
Richard Guy Briggs <rbri...@redhat.com>
Senior Software Engineer
AMER ENG Base Operating Systems
Remote, Canada, Ottawa
Voice: 1.647.777.2635
Internal: (81) 32635
>From d25d9bf48f62d35f88cee189fd3410dc1083167d Mon Sep 17 00:00:00 2001
From: Richard Guy Briggs <r...@redhat.com>
Date: Thu, 21 Mar 2013 00:56:51 -0400
Subject: [PATCH] pam_tty_audit: add an option to control logging of passwords
To: linux-audit@redhat.com
Most commands are entered one line at a time and processed as complete lines
in non-canonical mode. Commands that interactively require a password, enter
canonical mode to do this. This feature (icanon) can be used to avoid logging
passwords by audit while still logging the rest of the command.
Adding a member to the struct audit_tty_status passed in by pam_tty_audit
allows control of canonical mode per task.
Signed-off-by: Richard Guy Briggs <r...@redhat.com>
---
modules/pam_tty_audit/pam_tty_audit.8.xml | 13 +++++++++++++
modules/pam_tty_audit/pam_tty_audit.c | 9 +++++++--
2 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/modules/pam_tty_audit/pam_tty_audit.8.xml
b/modules/pam_tty_audit/pam_tty_audit.8.xml
index 447b845..deb494d 100644
--- a/modules/pam_tty_audit/pam_tty_audit.8.xml
+++ b/modules/pam_tty_audit/pam_tty_audit.8.xml
@@ -77,6 +77,17 @@
</para>
</listitem>
</varlistentry>
+ <varlistentry>
+ <term>
+ <option>log_icanon</option>
+ </term>
+ <listitem>
+ <para>
+ Log keystrokes in ICANON mode. By default, keystrokes in ICANON
+ mode are not logged to avoid logging passwords.
+ </para>
+ </listitem>
+ </varlistentry>
</variablelist>
</refsect1>
@@ -161,6 +172,8 @@ session required pam_tty_audit.so disable=* enable=root
<para>
pam_tty_audit was written by Miloslav Trmač
<m...@redhat.com>.
+ The log_icanon option was added by Richard Guy Briggs
+ <r...@redhat.com>.
</para>
</refsect1>
diff --git a/modules/pam_tty_audit/pam_tty_audit.c
b/modules/pam_tty_audit/pam_tty_audit.c
index 080f495..8eb4234 100644
--- a/modules/pam_tty_audit/pam_tty_audit.c
+++ b/modules/pam_tty_audit/pam_tty_audit.c
@@ -200,7 +200,7 @@ pam_sm_open_session (pam_handle_t *pamh, int flags, int
argc, const char **argv)
enum command command;
struct audit_tty_status *old_status, new_status;
const char *user;
- int i, fd, open_only;
+ int i, fd, open_only, log_icanon;
(void)flags;
@@ -212,6 +212,7 @@ pam_sm_open_session (pam_handle_t *pamh, int flags, int
argc, const char **argv)
command = CMD_NONE;
open_only = 0;
+ log_icanon = 0;
for (i = 0; i < argc; i++)
{
if (strncmp (argv[i], "enable=", 7) == 0
@@ -237,6 +238,8 @@ pam_sm_open_session (pam_handle_t *pamh, int flags, int
argc, const char **argv)
}
else if (strcmp (argv[i], "open_only") == 0)
open_only = 1;
+ else if (strcmp (argv[i], "log_icanon") == 0)
+ log_icanon = 1;
else
{
pam_syslog (pamh, LOG_ERR, "unknown option `%s'", argv[i]);
@@ -262,7 +265,9 @@ pam_sm_open_session (pam_handle_t *pamh, int flags, int
argc, const char **argv)
}
new_status.enabled = (command == CMD_ENABLE ? 1 : 0);
- if (old_status->enabled == new_status.enabled)
+ new_status.log_icanon = log_icanon;
+ if (old_status->enabled == new_status.enabled
+ && old_status->log_icanon == new_status.log_icanon)
{
open_only = 1; /* to clean up old_status */
goto ok_fd;
--
1.7.1
>From 110971ad92ce8669f6dc18db9e6369e92afdd03e Mon Sep 17 00:00:00 2001
From: Richard Guy Briggs <r...@redhat.com>
Date: Thu, 21 Mar 2013 00:52:37 -0400
Subject: [PATCH] tty: add an option to control logging of passwords with
pam_tty_audit
To: linux-audit@redhat.com
Most commands are entered one line at a time and processed as complete lines
in non-canonical mode. Commands that interactively require a password, enter
canonical mode to do this. This feature (icanon) can be used to avoid logging
passwords by audit while still logging the rest of the command.
Adding a member to the struct audit_tty_status passed in by pam_tty_audit
allows control of canonical mode per task.
Signed-off-by: Richard Guy Briggs <r...@redhat.com>
---
drivers/tty/tty_audit.c | 8 ++++++++
include/linux/sched.h | 1 +
include/uapi/linux/audit.h | 3 ++-
kernel/audit.c | 5 ++++-
4 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/tty_audit.c b/drivers/tty/tty_audit.c
index 6953dc8..cf3f4d9 100644
--- a/drivers/tty/tty_audit.c
+++ b/drivers/tty/tty_audit.c
@@ -153,6 +153,7 @@ void tty_audit_fork(struct signal_struct *sig)
{
spin_lock_irq(¤t->sighand->siglock);
sig->audit_tty = current->signal->audit_tty;
+ sig->audit_tty_log_icanon = current->signal->audit_tty_log_icanon;
spin_unlock_irq(¤t->sighand->siglock);
}
@@ -292,10 +293,17 @@ void tty_audit_add_data(struct tty_struct *tty, unsigned
char *data,
{
struct tty_audit_buf *buf;
int major, minor;
+ int audit_log_tty_icanon;
if (unlikely(size == 0))
return;
+ spin_lock_irq(¤t->sighand->siglock);
+ audit_log_tty_icanon = current->signal->audit_tty_log_icanon;
+ spin_unlock_irq(¤t->sighand->siglock);
+ if (!audit_log_tty_icanon && icanon)
+ return;
+
if (tty->driver->type == TTY_DRIVER_TYPE_PTY
&& tty->driver->subtype == PTY_TYPE_MASTER)
return;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index d35d2b6..031aa39 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -606,6 +606,7 @@ struct signal_struct {
#endif
#ifdef CONFIG_AUDIT
unsigned audit_tty;
+ unsigned audit_tty_log_icanon;
struct tty_audit_buf *tty_audit_buf;
#endif
#ifdef CONFIG_CGROUPS
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index 9f096f1..a863669 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -369,7 +369,8 @@ struct audit_status {
};
struct audit_tty_status {
- __u32 enabled; /* 1 = enabled, 0 = disabled */
+ __u32 enabled; /* 1 = enabled, 0 = disabled */
+ __u32 log_icanon; /* 1 = enabled, 0 = disabled */
};
/* audit_rule_data supports filter rules with both integer and string
diff --git a/kernel/audit.c b/kernel/audit.c
index d596e53..98d43c6 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -873,6 +873,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct
nlmsghdr *nlh)
spin_lock_irq(&tsk->sighand->siglock);
s.enabled = tsk->signal->audit_tty != 0;
+ s.log_icanon = tsk->signal->audit_tty_log_icanon != 0;
spin_unlock_irq(&tsk->sighand->siglock);
audit_send_reply(NETLINK_CB(skb).portid, seq,
@@ -886,11 +887,13 @@ static int audit_receive_msg(struct sk_buff *skb, struct
nlmsghdr *nlh)
if (nlh->nlmsg_len < sizeof(struct audit_tty_status))
return -EINVAL;
s = data;
- if (s->enabled != 0 && s->enabled != 1)
+ if (s->enabled != 0 && s->enabled != 1
+ && s->log_icanon != 0 && s->log_icanon != 1)
return -EINVAL;
spin_lock_irq(&tsk->sighand->siglock);
tsk->signal->audit_tty = s->enabled != 0;
+ tsk->signal->audit_tty_log_icanon = s->log_icanon != 0;
spin_unlock_irq(&tsk->sighand->siglock);
break;
}
--
1.7.1
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