shadow: fix CVE-2017-2616

(From OE-Core rev: 94a1e2794df15f0f2cb62ae030cd81e6c0798b1f)

Signed-off-by: Andrej Valek <andrej.valek@siemens.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 64 insertions, 0 deletions

diff --git a/meta/recipes-extended/shadow/files/CVE-2017-2616.patch b/meta/recipes-extended/shadow/files/CVE-2017-2616.patch
new file mode 100644
index 0000000000..ee728f0952
--- /dev/null
+++ b/meta/recipes-extended/shadow/files/CVE-2017-2616.patch
@@ -0,0 +1,64 @@
+shadow-4.2.1: Fix CVE-2017-2616
+
+[No upstream tracking] -- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=855943
+
+su: properly clear child PID
+
+If su is compiled with PAM support, it is possible for any local user
+to send SIGKILL to other processes with root privileges. There are
+only two conditions. First, the user must be able to perform su with
+a successful login. This does NOT have to be the root user, even using
+su with the same id is enough, e.g. "su $(whoami)". Second, SIGKILL
+can only be sent to processes which were executed after the su process.
+It is not possible to send SIGKILL to processes which were already
+running. I consider this as a security vulnerability, because I was
+able to write a proof of concept which unlocked a screen saver of
+another user this way.
+
+Upstream-Status: Backport [https://github.com/shadow-maint/shadow/commit/08fd4b69e84364677a10e519ccb25b71710ee686]
+CVE: CVE-2017-2616
+bug: 855943
+Signed-off-by: Andrej Valek <andrej.valek@siemens.com>
+
+diff --git a/src/su.c b/src/su.c
+index 3704217..1efcd61 100644
+--- a/src/su.c
++++ b/src/su.c
+@@ -363,20 +363,35 @@ static void prepare_pam_close_session (void)
+                                /* wake child when resumed */
+                                kill (pid, SIGCONT);
+                                stop = false;
++                       } else {
++                               pid_child = 0;
+                        }
+                } while (!stop);
+        }
+ 
+-       if (0 != caught) {
++       if (0 != caught && 0 != pid_child) {
+                (void) fputs ("\n", stderr);
+                (void) fputs (_("Session terminated, terminating shell..."),
+                              stderr);
+                (void) kill (-pid_child, caught);
+ 
+                (void) signal (SIGALRM, kill_child);
++               (void) signal (SIGCHLD, catch_signals);
+                (void) alarm (2);
+ 
+-               (void) wait (&status);
++               sigemptyset (&ourset);
++               if ((sigaddset (&ourset, SIGALRM) != 0)
++                   || (sigprocmask (SIG_BLOCK, &ourset, NULL) != 0)) {
++                       fprintf (stderr, _("%s: signal masking malfunction\n"), Prog);
++                       kill_child (0);
++               } else {
++                       while (0 == waitpid (pid_child, &status, WNOHANG)) {
++                               sigsuspend (&ourset);
++                       }
++                       pid_child = 0;
++                       (void) sigprocmask (SIG_UNBLOCK, &ourset, NULL);
++               }
++
+                (void) fputs (_(" ...terminated.\n"), stderr);
+        }
+