From d212765dc94ba25c04e0e9a278586f0e86851e35 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
Date: Sat, 11 Aug 2018 08:32:20 +0200
Subject: [PATCH] bus-message: fix skipping of array fields in !gvariant
 messages

We copied part of the string into a buffer that was off by two.
If the element signature had length one, we'd copy 0 bytes and crash when
looking at the "first" byte. Otherwise, we would crash because strncpy would
not terminate the string.

(cherry picked from commit 73777ddba5100fe6c0791cd37a91f24a515f3202)

Resolves: #1696224
---
 src/libsystemd/sd-bus/bus-message.c               |   8 ++++----
 ...crash-37449529b1ad867f0c2671fa80aca5d7812a2b70 | Bin 0 -> 534 bytes
 2 files changed, 4 insertions(+), 4 deletions(-)
 create mode 100644 test/fuzz/fuzz-bus-message/crash-37449529b1ad867f0c2671fa80aca5d7812a2b70

diff --git a/src/libsystemd/sd-bus/bus-message.c b/src/libsystemd/sd-bus/bus-message.c
index 09e72d89dd..202f1aab30 100644
--- a/src/libsystemd/sd-bus/bus-message.c
+++ b/src/libsystemd/sd-bus/bus-message.c
@@ -4981,18 +4981,18 @@ static int message_skip_fields(
 
                 } else if (t == SD_BUS_TYPE_ARRAY) {
 
-                        r = signature_element_length(*signature+1, &l);
+                        r = signature_element_length(*signature + 1, &l);
                         if (r < 0)
                                 return r;
 
                         assert(l >= 1);
                         {
-                                char sig[l-1], *s;
+                                char sig[l + 1], *s = sig;
                                 uint32_t nas;
                                 int alignment;
 
-                                strncpy(sig, *signature + 1, l-1);
-                                s = sig;
+                                strncpy(sig, *signature + 1, l);
+                                sig[l] = '\0';
 
                                 alignment = bus_type_get_alignment(sig[0]);
                                 if (alignment < 0)
diff --git a/test/fuzz/fuzz-bus-message/crash-37449529b1ad867f0c2671fa80aca5d7812a2b70 b/test/fuzz/fuzz-bus-message/crash-37449529b1ad867f0c2671fa80aca5d7812a2b70
new file mode 100644
index 0000000000000000000000000000000000000000..6a20265a39e1b4a318b50aee2b13727ddc4113bf
GIT binary patch
literal 534
zcmc~{WMHggWMD`aVqj=xU|>*W&P&W-;Q0Fg|9>Elfq|V9OfmRED27Bi2!jjC2Wn-|
z17hYPAOVtNW-Ml42GVKy`9P9^ffdMS1=8h-IVt%J91NTwNgyEFV4&K>#6$*=MMgl(
r%#fH?l1eMv=;=K=_yi-CK!KUB2_%6r0c0u^mlS2@rGxk|0FGY(dwVLU

literal 0
HcmV?d00001