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Prevent hangs with long MOTD (filling buffers and blocking)

This commit is contained in:
Jakub Jelen 2016-12-15 14:29:36 +01:00
parent d8c2e8dc88
commit 38869a3406
1 changed files with 69 additions and 29 deletions
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98
openssh-7.1p2-audit-race-condition.patch
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@ -1,8 +1,7 @@
diff --git a/monitor_wrap.c b/monitor_wrap.c
index 89a1762..fe98e08 100644
--- a/monitor_wrap.c
+++ b/monitor_wrap.c
@@ -1251,4 +1251,48 @@ mm_audit_destroy_sensitive_data(const char *fp, pid_t pid, uid_t uid)
diff -up openssh-7.3p1/monitor_wrap.c.audit-race openssh-7.3p1/monitor_wrap.c
--- openssh-7.3p1/monitor_wrap.c.audit-race 2016-12-15 14:27:22.376603747 +0100
+++ openssh-7.3p1/monitor_wrap.c 2016-12-15 14:27:22.381603742 +0100
@@ -1256,4 +1256,48 @@ mm_audit_destroy_sensitive_data(const ch
mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_AUDIT_SERVER_KEY_FREE, &m);
buffer_free(&m);
}
@ -32,13 +31,13 @@ index 89a1762..fe98e08 100644
+ buffer_clear(&m);
+ buffer_append_space(&m, msg_len);
+ if (atomicio(read, fdin, buffer_ptr(&m), msg_len) != msg_len) {
+ error("%s: Failed to read the the buffer conent from the child", __func__);
+ error("%s: Failed to read the the buffer content from the child", __func__);
+ ret = -1;
+ break;
+ }
+ if (atomicio(vwrite, pmonitor->m_recvfd, buf, blen) != blen ||
+ atomicio(vwrite, pmonitor->m_recvfd, buffer_ptr(&m), msg_len) != msg_len) {
+ error("%s: Failed to write the messag to the monitor", __func__);
+ error("%s: Failed to write the message to the monitor", __func__);
+ ret = -1;
+ break;
+ }
@ -51,11 +50,10 @@ index 89a1762..fe98e08 100644
+ pmonitor->m_recvfd = fd;
+}
#endif /* SSH_AUDIT_EVENTS */
diff --git a/monitor_wrap.h b/monitor_wrap.h
index e73134e..fbfe395 100644
--- a/monitor_wrap.h
+++ b/monitor_wrap.h
@@ -86,6 +86,8 @@ void mm_audit_unsupported_body(int);
diff -up openssh-7.3p1/monitor_wrap.h.audit-race openssh-7.3p1/monitor_wrap.h
--- openssh-7.3p1/monitor_wrap.h.audit-race 2016-12-15 14:27:22.376603747 +0100
+++ openssh-7.3p1/monitor_wrap.h 2016-12-15 14:27:22.381603742 +0100
@@ -88,6 +88,8 @@ void mm_audit_unsupported_body(int);
void mm_audit_kex_body(int, char *, char *, char *, char *, pid_t, uid_t);
void mm_audit_session_key_free_body(int, pid_t, uid_t);
void mm_audit_destroy_sensitive_data(const char *, pid_t, uid_t);
@ -64,11 +62,10 @@ index e73134e..fbfe395 100644
#endif
struct Session;
diff --git a/session.c b/session.c
index 8949fd1..9afb764 100644
--- a/session.c
+++ b/session.c
@@ -159,6 +159,10 @@ static Session *sessions = NULL;
diff -up openssh-7.3p1/session.c.audit-race openssh-7.3p1/session.c
--- openssh-7.3p1/session.c.audit-race 2016-12-15 14:27:22.378603745 +0100
+++ openssh-7.3p1/session.c 2016-12-15 14:27:22.382603741 +0100
@@ -164,6 +164,10 @@ static Session *sessions = NULL;
login_cap_t *lc;
#endif
@ -79,7 +76,35 @@ index 8949fd1..9afb764 100644
static int is_child = 0;
static int in_chroot = 0;
static int have_dev_log = 1;
@@ -875,6 +879,8 @@ do_exec(Session *s, const char *command)
@@ -457,6 +457,8 @@ do_authenticated1(Authctxt *authctxt)
}
}
+void child_destory_sensitive_data();
+
#define USE_PIPES 1
/*
* This is called to fork and execute a command when we have no tty. This
@@ -588,6 +592,8 @@ do_exec_no_pty(Session *s, const char *c
cray_init_job(s->pw); /* set up cray jid and tmpdir */
#endif
+ child_destory_sensitive_data();
+
/* Do processing for the child (exec command etc). */
do_child(s, command);
/* NOTREACHED */
@@ -722,6 +728,9 @@ do_exec_pty(Session *s, const char *comm
/* Close the extra descriptor for the pseudo tty. */
close(ttyfd);
+ /* Do this early, so we will not block large MOTDs */
+ child_destory_sensitive_data();
+
/* record login, etc. similar to login(1) */
#ifndef HAVE_OSF_SIA
if (!(options.use_login && command == NULL)) {
@@ -903,6 +912,8 @@ do_exec(Session *s, const char *command)
}
if (s->command != NULL && s->ptyfd == -1)
s->command_handle = PRIVSEP(audit_run_command(s->command));
@ -88,7 +113,7 @@ index 8949fd1..9afb764 100644
#endif
if (s->ttyfd != -1)
ret = do_exec_pty(s, command);
@@ -890,6 +896,20 @@ do_exec(Session *s, const char *command)
@@ -918,6 +929,20 @@ do_exec(Session *s, const char *command)
*/
buffer_clear(&loginmsg);
@ -109,10 +134,13 @@ index 8949fd1..9afb764 100644
return ret;
}
@@ -1707,12 +1727,28 @@ do_child(Session *s, const char *command)
struct passwd *pw = s->pw;
int r = 0;
@@ -1751,6 +1776,33 @@ child_close_fds(void)
endpwent();
}
+void
+child_destory_sensitive_data()
+{
+#ifdef SSH_AUDIT_EVENTS
+ int pparent = paudit[1];
+ close(paudit[0]);
@ -121,23 +149,35 @@ index 8949fd1..9afb764 100644
+ mm_set_monitor_pipe(pparent);
+#endif
+
/* remove hostkey from the child's memory */
- destroy_sensitive_data(1);
- /* Don't audit this - both us and the parent would be talking to the
- monitor over a single socket, with no synchronization. */
+ /* remove hostkey from the child's memory */
+ destroy_sensitive_data(use_privsep);
+ /*
+ * We can audit this, because wer hacked the pipe to direct the
+ * We can audit this, because we hacked the pipe to direct the
+ * messages over postauth child. But this message requires answer
+ * which we can't do using one-way pipe.
+ */
packet_destroy_all(0, 1);
+ packet_destroy_all(0, 1);
+
+#ifdef SSH_AUDIT_EVENTS
+ /* Notify parent that we are done */
+ close(pparent);
+#endif
+
+}
+
/*
* Performs common processing for the child, such as setting up the
* environment, closing extra file descriptors, setting the user and group
@@ -1768,12 +1820,6 @@ do_child(Session *s, const char *command
struct passwd *pw = s->pw;
int r = 0;
- /* remove hostkey from the child's memory */
- destroy_sensitive_data(1);
- /* Don't audit this - both us and the parent would be talking to the
- monitor over a single socket, with no synchronization. */
- packet_destroy_all(0, 1);
-
/* Force a password change */
if (s->authctxt->force_pwchange) {
do_setusercontext(pw);