From 94a1e2794df15f0f2cb62ae030cd81e6c0798b1f Mon Sep 17 00:00:00 2001 From: Andrej Valek Date: Tue, 24 Jul 2018 13:08:29 +0200 Subject: shadow: fix CVE-2017-2616 Signed-off-by: Andrej Valek Signed-off-by: Ross Burton --- .../shadow/files/CVE-2017-2616.patch | 64 ++++++++++++++++++++++ meta/recipes-extended/shadow/shadow.inc | 1 + 2 files changed, 65 insertions(+) create mode 100644 meta/recipes-extended/shadow/files/CVE-2017-2616.patch (limited to 'meta') 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 $(whoami)". Second, SIGKILL +can only be sent to processes which were executed after the su process. +It is not possible to send SIGKILL to processes which were already +running. I consider this as a security vulnerability, because I was +able to write a proof of concept which unlocked a screen saver of +another user this way. + +Upstream-Status: Backport [https://github.com/shadow-maint/shadow/commit/08fd4b69e84364677a10e519ccb25b71710ee686] +CVE: CVE-2017-2616 +bug: 855943 +Signed-off-by: Andrej Valek + +diff --git a/src/su.c b/src/su.c +index 3704217..1efcd61 100644 +--- a/src/su.c ++++ b/src/su.c +@@ -363,20 +363,35 @@ static void prepare_pam_close_session (void) + /* wake child when resumed */ + kill (pid, SIGCONT); + stop = false; ++ } else { ++ pid_child = 0; + } + } while (!stop); + } + +- if (0 != caught) { ++ if (0 != caught && 0 != pid_child) { + (void) fputs ("\n", stderr); + (void) fputs (_("Session terminated, terminating shell..."), + stderr); + (void) kill (-pid_child, caught); + + (void) signal (SIGALRM, kill_child); ++ (void) signal (SIGCHLD, catch_signals); + (void) alarm (2); + +- (void) wait (&status); ++ sigemptyset (&ourset); ++ if ((sigaddset (&ourset, SIGALRM) != 0) ++ || (sigprocmask (SIG_BLOCK, &ourset, NULL) != 0)) { ++ fprintf (stderr, _("%s: signal masking malfunction\n"), Prog); ++ kill_child (0); ++ } else { ++ while (0 == waitpid (pid_child, &status, WNOHANG)) { ++ sigsuspend (&ourset); ++ } ++ pid_child = 0; ++ (void) sigprocmask (SIG_UNBLOCK, &ourset, NULL); ++ } ++ + (void) fputs (_(" ...terminated.\n"), stderr); + } + diff --git a/meta/recipes-extended/shadow/shadow.inc b/meta/recipes-extended/shadow/shadow.inc index 9a08918818..6efe4a9119 100644 --- a/meta/recipes-extended/shadow/shadow.inc +++ b/meta/recipes-extended/shadow/shadow.inc @@ -18,6 +18,7 @@ SRC_URI = "https://downloads.yoctoproject.org/mirror/sources/${BP}.tar.xz \ file://check_size_of_uid_t_and_gid_t_using_AC_CHECK_SIZEOF.patch \ file://0001-useradd-copy-extended-attributes-of-home.patch \ file://0001-shadow-CVE-2017-12424 \ + file://CVE-2017-2616.patch \ ${@bb.utils.contains('PACKAGECONFIG', 'pam', '${PAM_SRC_URI}', '', d)} \ " -- cgit 1.2.3-korg