audit: add an option to control logging of passwords with pam_tty_audit

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 while shutting off echo.  This pair of features
(icanon and !echo) can be used to avoid logging passwords by audit while still
logging the rest of the command.

Adding a member (log_passwd) to the struct audit_tty_status passed in by
pam_tty_audit allows control of canonical mode without echo per task.

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>

1 files changed, 10 insertions, 6 deletions

diff --git a/kernel/audit.c b/kernel/audit.c
index 241aa8593fa8..998a0d4155cf 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -49,6 +49,7 @@
 #include <linux/slab.h>
 #include <linux/err.h>
 #include <linux/kthread.h>
+#include <linux/kernel.h>
 
 #include <linux/audit.h>
 
@@ -808,6 +809,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 
                 spin_lock_irqsave(&tsk->sighand->siglock, flags);
                 s.enabled = tsk->signal->audit_tty != 0;
+                s.log_passwd = tsk->signal->audit_tty_log_passwd;
                 spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
 
                 audit_send_reply(NETLINK_CB(skb).portid, seq,
@@ -815,18 +817,20 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
                 break;
         }
         case AUDIT_TTY_SET: {
-                struct audit_tty_status *s;
+                struct audit_tty_status s;
                 struct task_struct *tsk = current;
                 unsigned long flags;
 
-                if (nlh->nlmsg_len < sizeof(struct audit_tty_status))
-                        return -EINVAL;
-                s = data;
-                if (s->enabled != 0 && s->enabled != 1)
+                memset(&s, 0, sizeof(s));
+                /* guard against past and future API changes */
+                memcpy(&s, data, min(sizeof(s), (size_t)nlh->nlmsg_len));
+                if ((s.enabled != 0 && s.enabled != 1) ||
+                    (s.log_passwd != 0 && s.log_passwd != 1))
                         return -EINVAL;
 
                 spin_lock_irqsave(&tsk->sighand->siglock, flags);
-                tsk->signal->audit_tty = s->enabled != 0;
+                tsk->signal->audit_tty = s.enabled;
+                tsk->signal->audit_tty_log_passwd = s.log_passwd;
                 spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
                 break;
         }