From 9dbac61cf123a57c1f39a2f134389f1a5877dc29 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>

Date: Thu, 3 Jan 2019 16:09:05 +0100

Subject: [PATCH] journald: set a limit on the number of fields (1k)

We allocate a iovec entry for each field, so with many short entries,

our memory usage and processing time can be large, even with a relatively

small message size. Let's refuse overly long entries.

CVE-2018-16865

https://bugzilla.redhat.com/show_bug.cgi?id=1653861

What from I can see, the problem is not from an alloca, despite what the CVE

description says, but from the attack multiplication that comes from creating

many very small iovecs: (void* + size_t) for each three bytes of input

message.

Resolves: #1657792

---

 src/journal/journal-file.h    | 3 +++

 src/journal/journald-native.c | 4 ++++

 2 files changed, 7 insertions(+)

diff --git a/src/journal/journal-file.h b/src/journal/journal-file.h

index dd8ef52d2a..37749c4459 100644

--- a/src/journal/journal-file.h

+++ b/src/journal/journal-file.h

@@ -158,6 +158,9 @@ int journal_file_open_reliably(

  * files without adding too many zeros. */

 #define OFSfmt "%06"PRIx64

+/* The maximum number of fields in an entry */

+#define ENTRY_FIELD_COUNT_MAX 1024

+

 static inline bool VALID_REALTIME(uint64_t u) {

         /* This considers timestamps until the year 3112 valid. That should be plenty room... */

         return u > 0 && u < (1ULL << 55);

diff --git a/src/journal/journald-native.c b/src/journal/journald-native.c

index cf3349393f..0c451274f7 100644

--- a/src/journal/journald-native.c

+++ b/src/journal/journald-native.c

@@ -134,6 +134,10 @@ void server_process_native_message(

                 }

                 /* A property follows */

+                if (n > ENTRY_FIELD_COUNT_MAX) {

+                        log_debug("Received an entry that has more than " STRINGIFY(ENTRY_FIELD_COUNT_MAX) " fields, ignoring entry.");

+                        goto finish;

+                }

                 /* n existing properties, 1 new, +1 for _TRANSPORT */

                 if (!GREEDY_REALLOC(iovec, m, n + 2 + N_IOVEC_META_FIELDS + N_IOVEC_OBJECT_FIELDS)) {